JP7449207B2 - liquid crystal display device - Google Patents

Description

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which each pixel includes a reflective region.

Liquid crystal display devices are generally classified into transmissive liquid crystal display devices and reflective liquid crystal display devices. Transmissive liquid crystal display devices perform transmissive mode display using light emitted from a backlight. A reflective liquid crystal display device performs reflective mode display using ambient light. Furthermore, a liquid crystal display device has been proposed in which each pixel includes a reflective area that displays in a reflective mode and a transmissive area that displays in a transmissive mode. Such a liquid crystal display device is called a transflective or transflective liquid crystal display device.

Reflective and transflective liquid crystal display devices are suitably used, for example, as small and medium-sized display devices for mobile applications used outdoors. A reflective liquid crystal display device is disclosed in Patent Document 1, for example. A transflective liquid crystal display device is disclosed in Patent Document 2, for example.

In the reflective liquid crystal display device disclosed in Patent Document 1, a reflective electrode provided on a TFT substrate has an uneven shape. Further, in the transflective liquid crystal display device disclosed in Patent Document 2, the reflective electrode provided in the reflective region has an uneven shape. Since the reflective electrode has an uneven shape, it is possible to diffusely reflect ambient light and realize a display close to paper white.

Japanese Patent Application Publication No. 2000-122094 Japanese Patent Application Publication No. 2003-131268

Further improvement of light utilization efficiency (reflectance) in reflective mode display in reflective and transflective liquid crystal display devices, that is, liquid crystal display devices in which each pixel includes an area (reflective area) where each pixel performs display in reflective mode. (In other words, it is desired to be able to perform brighter display in reflective mode).

The present invention has been made in view of the above-mentioned problems, and its purpose is to improve the reflectance and brighter than the conventional liquid crystal display device, in which each pixel includes a reflective area for displaying in a reflective mode. The goal is to realize the display.

According to an embodiment of the present invention, a liquid crystal display device described in the following items is provided.

[Item 1]
a first substrate;
a second substrate facing the first substrate;
a liquid crystal layer provided between the first substrate and the second substrate;
Equipped with
A liquid crystal display device having a plurality of pixels arranged in a matrix including a plurality of rows and a plurality of columns,
Each of the plurality of pixels includes a reflective area that performs display in reflective mode,
The first substrate includes a pixel electrode provided for each of the plurality of pixels, and a reflective layer located on a side opposite to the liquid crystal layer with respect to the pixel electrode,
The reflective layer includes a first region located within each of the plurality of pixels, and a second region located between any two adjacent pixels among the plurality of pixels,
Any two pixels adjacent to each other along the row direction among the plurality of pixels, any two pixels adjacent to each other along the column direction among the plurality of pixels, or all of the plurality of pixels. A liquid crystal display device, wherein voltages of the same polarity are applied to the liquid crystal layer of the pixels.

[Item 2]
The liquid crystal display device according to item 1, wherein the second substrate does not have a black matrix between any two adjacent pixels among the plurality of pixels.

[Item 3]
The first substrate further includes a transparent insulating layer provided to cover the reflective layer,
3. The liquid crystal display device according to item 1 or 2, wherein the pixel electrode is made of a transparent conductive material and is disposed on the transparent insulating layer.

[Item 4]
Each of the plurality of pixels further includes a transparent area for displaying in a transparent mode,
The liquid crystal display device according to item 3, wherein a part of the pixel electrode is located within the transmissive region.

[Item 5]
5. The liquid crystal display device according to item 4, wherein the thickness of the liquid crystal layer in the transmissive area is greater than the thickness of the liquid crystal layer in the reflective area.

[Item 6]
The first substrate has a backplane circuit electrically connected to the pixel electrode, and a further transparent insulating layer provided to cover the backplane circuit,
the reflective layer is disposed on the further transparent insulating layer,
the further transparent insulating layer has a first contact hole formed in the transparent region;
The transparent insulating layer has a second contact hole formed in the transparent region,
The first substrate further includes a contact portion that electrically connects the pixel electrode and the backplane circuit in the first contact hole and the second contact hole,
6. The liquid crystal display device according to item 4 or 5, wherein the contact portion is formed from a transparent conductive material.

[Item 7]
The first substrate has a first alignment film provided in contact with the liquid crystal layer,
The second substrate has a second alignment film provided in contact with the liquid crystal layer,
7. The liquid crystal display device according to any one of items 4 to 6, wherein at least one of the first alignment film and the second alignment film defines different pretilt orientations in the transmission area and the reflection area.

[Item 8]
8. The liquid crystal display device according to item 7, wherein at least one of the first alignment film and the second alignment film is subjected to a photoalignment treatment.

[Item 9]
The second substrate has a counter electrode provided to face the pixel electrode,
9. The liquid crystal display device according to any one of items 3 to 8, wherein the counter electrode is formed of a transparent conductive material.

[Item 10]
The liquid crystal display device according to any one of items 1 to 9, further comprising a memory circuit connected to each of the plurality of pixels.

[Item 11]
11. The liquid crystal display device according to any one of items 1 to 10, wherein voltages of the same polarity are applied to the liquid crystal layer of all pixels of the plurality of pixels.

[Item 12]
The second substrate includes a first color filter that transmits light of a first color, a second color filter that transmits light of a second color, and a third color filter that transmits light of a third color. having a filter layer;
The second substrate includes a colorless area in which none of the first color filter, the second color filter, and the third color filter are provided,
12. The liquid crystal display device according to any one of items 1 to 11, wherein the colorless region overlaps at least a portion of the second region of the reflective layer when viewed from the normal direction of the display surface.

[Item 13]
13. The liquid crystal display device according to item 12, wherein the colorless region does not overlap the pixel electrode when viewed from the normal direction of the display surface.

[Item 14]
14. The liquid crystal display device according to any one of items 1 to 13, wherein each of the first region and the second region of the reflective layer has an uneven surface structure.

[Item 15]
The liquid crystal display device according to any one of items 1 to 13, further comprising a light scattering layer disposed closer to the viewer than the liquid crystal layer.

[Item 16]
16. The liquid crystal display device according to any one of items 1 to 15, wherein the liquid crystal layer includes liquid crystal molecules and a dichroic dye.

According to the embodiments of the present invention, in a liquid crystal display device in which each pixel includes a reflective area that performs display in a reflective mode, it is possible to improve reflectance than before and achieve brighter display than before.

1 is a plan view schematically showing a liquid crystal display device 100 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 100. FIG. 2 is a cross-sectional view schematically showing a liquid crystal display device 100, showing a cross-sectional structure taken along line 2A-2A' in FIG. 1. FIG. 2 is a cross-sectional view schematically showing a liquid crystal display device 100, showing a cross-sectional structure taken along line 2B-2B' in FIG. 1. FIG. FIG. 2 is a plan view showing an example of a configuration in which each pixel P of the liquid crystal display device 100 is divided into a plurality of sub-pixels Sp. 4 is a diagram showing an example of gradation display using the configuration shown in FIG. 3. FIG. 3 is a plan view showing a liquid crystal display device 900 of a comparative example, showing areas corresponding to three pixels P of the liquid crystal display device 900. FIG. 5 is a cross-sectional view of a liquid crystal display device 900, showing a cross-sectional structure taken along line 6A-6A' in FIG. 5. FIG. 5 is a cross-sectional view of a liquid crystal display device 900, showing a cross-sectional structure taken along line 6B-6B' in FIG. 5. FIG. FIG. 2 is a plan view schematically showing another liquid crystal display device 200 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 200. FIG. 7 is a cross-sectional view schematically showing a liquid crystal display device 200, showing a cross-sectional structure taken along line 8A-8A' in FIG. 7. FIG. 7 is a cross-sectional view schematically showing a liquid crystal display device 200, showing a cross-sectional structure taken along line 8B-8B' in FIG. 7. FIG. 3 is a plan view schematically showing still another liquid crystal display device 300 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 300. FIG. 9 is a cross-sectional view schematically showing a liquid crystal display device 300, showing a cross-sectional structure taken along line 10A-10A' in FIG. 9. FIG. 9 is a cross-sectional view schematically showing a liquid crystal display device 300, showing a cross-sectional structure taken along line 10B-10B' in FIG. 9. FIG. FIG. 4 is a plan view schematically showing still another liquid crystal display device 400 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 400. FIG. 12 is a cross-sectional view schematically showing a liquid crystal display device 400, showing a cross-sectional structure taken along line 12A-12A' in FIG. 11. FIG. 12 is a cross-sectional view schematically showing a liquid crystal display device 400, showing a cross-sectional structure taken along line 12B-12B' in FIG. 11. FIG. 5 is a plan view schematically showing still another liquid crystal display device 500 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 500. FIG. 14 is a cross-sectional view schematically showing a liquid crystal display device 500, showing a cross-sectional structure taken along line 14A-14A' in FIG. 13. FIG. 14 is a cross-sectional view schematically showing a liquid crystal display device 500, showing a cross-sectional structure taken along line 14B-14B' in FIG. 13. FIG. 7 is a plan view schematically showing still another liquid crystal display device 600 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 600. FIG. 15 is a cross-sectional view schematically showing a liquid crystal display device 600, showing a cross-sectional structure taken along line 16A-16A' in FIG. 15. FIG. 15 is a cross-sectional view schematically showing a liquid crystal display device 600, showing a cross-sectional structure taken along line 16B-16B' in FIG. 15. FIG. 7 is a cross-sectional view showing a liquid crystal display device 700 of Example 7. FIG. 7 is a plan view schematically showing still another liquid crystal display device 800 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 800. FIG. 18 is a cross-sectional view schematically showing a liquid crystal display device 800, showing a cross-sectional structure taken along line 19A-19A' in FIG. 18. FIG. 18 is a cross-sectional view schematically showing a liquid crystal display device 800, showing a cross-sectional structure taken along line 19B-19B' in FIG. 18. FIG. FIG. 3 is a plan view schematically showing still another liquid crystal display device 1000 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 1000. 20 is a cross-sectional view schematically showing a liquid crystal display device 1000, showing a cross-sectional structure taken along line 21A-21A' in FIG. 20. FIG. 20 is a cross-sectional view schematically showing a liquid crystal display device 1000, showing a cross-sectional structure taken along line 21B-21B' in FIG. 20. FIG. 7 is a diagram showing another example of the arrangement of the light scattering layer 41. FIG. 7 is a diagram showing still another example of the arrangement of the light scattering layer 41. FIG. 7 is a diagram showing still another example of the arrangement of the light scattering layer 41. FIG. FIG. 3 is a plan view schematically showing still another liquid crystal display device 1100 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 1100. 23 is a cross-sectional view schematically showing a liquid crystal display device 1100, showing a cross-sectional structure taken along line 24A-24A' in FIG. 23. FIG. 24 is a cross-sectional view schematically showing a liquid crystal display device 1100, showing a cross-sectional structure taken along line 24B-24B' in FIG. 23. FIG. FIG. 3 is a plan view schematically showing still another liquid crystal display device 1200 according to an embodiment of the present invention, and shows areas corresponding to three pixels P of the liquid crystal display device 1200. 25 is a cross-sectional view schematically showing a liquid crystal display device 1200, showing a cross-sectional structure taken along line 26A-26A' in FIG. 25. FIG. 25 is a cross-sectional view schematically showing a liquid crystal display device 1200, showing a cross-sectional structure taken along line 26B-26B' in FIG. 25. FIG. FIG. 3 is a plan view schematically showing still another liquid crystal display device 1300 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 1300. 27 is a cross-sectional view schematically showing a liquid crystal display device 1300, showing a cross-sectional structure taken along line 28A-28A' in FIG. 27. FIG. 27 is a cross-sectional view schematically showing a liquid crystal display device 1300, showing a cross-sectional structure taken along line 28B-28B' in FIG. 27. FIG. FIG. 7 is a plan view schematically showing still another liquid crystal display device 1400 according to an embodiment of the present invention, showing areas corresponding to three pixels P of the liquid crystal display device 1400. 29 is a cross-sectional view schematically showing a liquid crystal display device 1400, showing a cross-sectional structure taken along line 30A-30A' in FIG. 29. FIG. 29 is a cross-sectional view schematically showing a liquid crystal display device 1400, showing a cross-sectional structure taken along line 30B-30B' in FIG. 29. FIG.

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments.

(Embodiment 1)
A liquid crystal display device 100 in this embodiment will be described with reference to FIGS. 1, 2A, and 2B. The liquid crystal display device 100 of this embodiment is a reflective liquid crystal display device. FIG. 1 is a plan view schematically showing a liquid crystal display device 100, and shows areas corresponding to three pixels P of the liquid crystal display device 100. 2A and 2B are cross-sectional views schematically showing the liquid crystal display device 100, and show cross-sectional structures taken along lines 2A-2A' and 2B-2B' in FIG. 1, respectively.

The liquid crystal display device 100 has a plurality of pixels P, as shown in FIG. The plurality of pixels P are arranged in a matrix including a plurality of rows and a plurality of columns. The plurality of pixels P typically includes a red pixel PR that displays red, a green pixel _PG that displays green, and _{a blue pixel PB that} displays blue.

Further, as shown in FIG. 2, the liquid crystal display device 100 includes a TFT substrate (first substrate) 10, a counter substrate (second substrate) 20 facing the TFT substrate 10, and a TFT substrate 10 and a counter substrate 20. and a liquid crystal layer 30 provided therebetween. Each pixel P includes a reflective region Rf that displays in reflective mode, and does not include a region (that is, a transmissive region) that displays in transmissive mode.

The TFT substrate 10 includes a pixel electrode 11 provided for each of a plurality of pixels P, and a reflective layer 12 located on the opposite side of the pixel electrode 11 from the liquid crystal layer 30 (that is, on the back side of the pixel electrode 11). has. The TFT substrate 10 further includes a first interlayer insulating layer 13, a second interlayer insulating layer 14, a contact portion CP, and a first alignment film 15.

The components of the TFT substrate 10 (the above-mentioned pixel electrode 11, etc.) are supported by the substrate 10a. The substrate 10a is, for example, a glass substrate or a plastic substrate.

A circuit (backplane circuit) for driving the pixel P is formed on the substrate 10a (not shown). Here, the backplane circuit includes a memory circuit (eg, SRAM) connected to each of the plurality of pixels P. A liquid crystal display device in which a memory circuit is provided for each pixel P is sometimes called a "memory liquid crystal". A specific configuration of the memory liquid crystal is disclosed in, for example, Japanese Patent No. 5,036,864 (corresponding to US Pat. No. 8,692,758). The entire disclosures of Patent No. 5,036,864 and US Pat. No. 8,692,758 are incorporated herein by reference.

The first interlayer insulating layer 13 is provided to cover the backplane circuit. The surface of the first interlayer insulating layer 13 has an uneven shape. That is, the first interlayer insulating layer 13 has an uneven surface structure. The first interlayer insulating layer 13 having an uneven surface structure may be formed using a photosensitive resin, for example, as described in Japanese Patent No. 3394926.

The reflective layer 12 is provided on the first interlayer insulating layer 13 . The reflective layer 12 is made of a metal material with high reflectance. Here, a silver alloy is used as the metal material for forming the reflective layer 12, but the material is not limited to this, and for example, aluminum or an aluminum alloy may be used. The surface of the reflective layer 12 has an uneven shape that reflects the uneven surface structure of the first interlayer insulating layer 13 . In other words, the reflective layer 12 also has an uneven surface structure. The uneven surface structure of the reflective layer 12 is provided to diffusely reflect ambient light and realize a display close to paper white. The uneven surface structure may be composed of a plurality of protrusions p randomly arranged such that, for example, the center distance between adjacent protrusions p is 5 μm or more and 50 μm or less, preferably 10 μm or more and 20 μm or less. When viewed from the normal direction of the substrate 10a, the shape of the convex portion p is approximately circular or approximately polygonal. The area of the convex portion p that occupies the pixel P is, for example, approximately 20% to 40%. The height of the convex portion p is, for example, 1 μm or more and 5 μm or less.

The second interlayer insulating layer 14 is a transparent insulating layer provided so as to cover the reflective layer 12.

The pixel electrode 11 is arranged on the second interlayer insulating layer 14. That is, the pixel electrode 11 is provided on the reflective layer 12 with the transparent insulating layer 14 interposed therebetween. The pixel electrode 11 is made of a transparent conductive material. As the transparent conductive material, for example, indium tin oxide (ITO), indium zinc oxide (IZO (registered trademark)), or a mixture thereof can be used. The pixel electrode 11 is electrically connected to a backplane circuit including a memory circuit.

The contact portion CP electrically connects the pixel electrode 11 and the backplane circuit in the first contact hole CH1 formed in the first interlayer insulating layer 13 and the second contact hole CH2 formed in the second interlayer insulating layer 14. Connecting. In the illustrated example, the contact portion CP includes a first contact electrode 16, a second contact electrode 17, and a third contact electrode 18.

The first contact electrode 16 is an electrode (or a part of the wiring) exposed in the first contact hole CH1. The second contact electrode 17 is formed on the first interlayer insulating layer 13 and within the first contact hole CH1, and is connected to the first contact electrode 16 within the first contact hole CH1. Further, a portion of the second contact electrode 17 is exposed within the second contact hole CH2. The third contact electrode 18 is connected to the second contact electrode 17 and the pixel electrode 11 in the second contact hole CH2. In other words, the third contact electrode 18 is interposed between the second contact electrode 17 and the pixel electrode 11. In the illustrated example, the conductive layer 19 formed from the same conductive film as the second contact electrode 17 (that is, in the same layer as the second contact electrode 17) is connected to the reflective layer 12 and the first interlayer insulating layer 13. intervening in between. Further, the third contact electrode 18 is formed from the same metal film as the reflective layer 12 (that is, in the same layer as the reflective layer 12). The conductive layer 19 and the third contact electrode 18 may be omitted.

The counter substrate 20 has a counter electrode 21 and a second alignment film 25 . Further, the counter substrate 20 further includes a color filter layer and a plurality of columnar spacers (none of which are shown). The components of the counter substrate 20 (the above-mentioned counter electrode 21, etc.) are supported by the substrate 20a. The substrate 20a is, for example, a glass substrate or a plastic substrate. Note that the counter substrate 20 does not have a black matrix (light shielding layer) between any two pixels P adjacent to each other.

The counter electrode 21 is provided to face the pixel electrode 11 . The counter electrode 21 is made of a transparent conductive material. As the transparent conductive material for forming the counter electrode 21, the same material as the pixel electrode 11 can be used. Here, the same potential (common potential) as that applied to the counter electrode 21 is applied to the reflective layer 12, and an auxiliary capacitance is created by the pixel electrode 11, the reflective layer 12, and the second interlayer insulating layer 14 located between them. It is formed.

The color filter layer typically includes a red color filter provided in a region corresponding to the red pixel _PR , a green color filter provided in the region corresponding to the green pixel _PG , and a blue color filter corresponding to the blue pixel PB. Contains a blue color filter provided in the area. The regions of the color filter layer corresponding to the pixels P of different colors are, for example, approximately equally divided by color filters of different colors.

The columnar spacer defines the thickness (cell gap) of the liquid crystal layer 30. The columnar spacer can be formed from photosensitive resin.

The liquid crystal layer 30 here includes a nematic liquid crystal material with negative dielectric anisotropy (that is, negative type) and a chiral agent. The liquid crystal layer 30 can be formed, for example, by a dropping method.

The first alignment film 15 and the second alignment film 25 are provided so as to be in contact with the liquid crystal layer 30, respectively. Here, each of the first alignment film 15 and the second alignment film 25 is a vertical alignment film. At least one of the first alignment film 15 and the second alignment film 25 is subjected to an alignment treatment and defines a pretilt orientation. The liquid crystal molecules of the liquid crystal layer 30 are vertically aligned when no voltage is applied to the liquid crystal layer 30, and are twistedly aligned when a predetermined voltage is applied to the liquid crystal layer 30.

Although not shown here, the liquid crystal display device 100 further includes a polarizing plate disposed on the viewer side of the liquid crystal layer 30. Further, a retardation plate may be provided between the polarizing plate and the liquid crystal layer 30. The polarizing plate (and the retardation plate) are arranged so that display is performed in normally black mode, for example.

The reflective layer 12 includes a first region 12a located within each of the plurality of pixels P, and a second region 12b located between any two pixels P adjacent to each other. The uneven surface structure of the reflective layer 12 is formed in each of the first region 12a and the second region 12b. In other words, not only the first region 12a but also the second region 12b has an uneven surface structure.

In the liquid crystal display device 100, one of the following driving methods is used.

Method (A): Voltages of the same polarity are applied to the liquid crystal layers 30 of any two pixels P adjacent to each other along the row direction among the plurality of pixels P. This is a driving method called row line inversion drive (H line inversion drive), and includes a mode in which the polarity is inverted for every plurality of rows (2H line inversion drive, etc.).

Method (B): Voltages of the same polarity are applied to the liquid crystal layers 30 of any two pixels P adjacent to each other along the column direction among the plurality of pixels P. This is a drive method called column line inversion drive (V line inversion drive), and also includes a mode in which the polarity is inverted for every plurality of columns (2V line inversion drive, etc.).

Method (C): Voltages of the same polarity are applied to the liquid crystal layers 30 of all the pixels P of the plurality of pixels P. This is a drive method called field inversion drive (frame inversion drive).

As described above, in the liquid crystal display device 100 of this embodiment, the reflective layer 12 includes not only the first region 12a located within the pixel P but also the second region 12b located between two adjacent pixels P. I'm here. Therefore, since the area between the pixels P can also contribute to reflective display, the reflective aperture ratio (the ratio of the area that contributes to reflective mode display in the display area) is improved, and the reflectance is further improved. be able to. Therefore, even brighter display can be performed in reflective mode.

Further, in the liquid crystal display device 100 of this embodiment, driving is performed by any one of the above-mentioned methods (A), (B), and (C). This increases the effect of improving reflectance (brightening the display). The reason for this will be explained below.

As a driving method for liquid crystal display devices, a method called dot inversion driving is well known and widely used. In dot inversion driving, voltages of different polarities are applied to the liquid crystal layers of any two adjacent pixels among a plurality of pixels. That is, the polarity of the applied voltage is reversed for each pixel along the row direction, and the polarity of the applied voltage is reversed for each pixel along the column direction. When the polarity of the voltage applied to the liquid crystal layer is opposite between adjacent pixels, as in dot inversion driving, the liquid crystal molecules located between the pixels contribute to brightness due to the influence of the diagonal electric field generated between the pixels. There is a possibility that it will not be oriented properly.

In contrast, in this embodiment, the polarity of the applied voltage is the same (not reversed) between adjacent pixels P along at least one of the row direction and the column direction, so voltages of the same polarity are applied. Liquid crystal molecules located between pixels P can be oriented so as to contribute to brightness. Therefore, the effect of improving reflectance becomes high. Note that from the viewpoint of further improving the reflectance, method (C) is preferable to methods (A) and (B). That is, field inversion driving is preferable, in which voltages of the same polarity are applied to the liquid crystal layer 30 of all the pixels P of the plurality of pixels P.

In addition, in the liquid crystal display device 100 of this embodiment, since the region between the pixels P contributes to display in the reflective mode, the counter substrate 20 has a region between any two pixels P adjacent to each other among the plurality of pixels P. It is preferable not to have a black matrix.

Further, in this embodiment, a transparent insulating layer 14 is provided to cover the reflective layer 12, and a pixel electrode 11 made of a transparent conductive material is arranged on the transparent insulating layer 14. Therefore, the pixel electrode 11 formed from a transparent conductive material and the counter electrode 21 formed from a transparent conductive material are opposed to each other with the liquid crystal layer 30 interposed therebetween. On the other hand, in general reflective liquid crystal display devices, the pixel electrode is a reflective electrode that also serves as a reflective layer, so the pixel electrode (reflective electrode) is made of a metal material, and the opposing The electrodes are opposed to each other with a liquid crystal layer interposed therebetween. Therefore, flicker may occur due to the difference in work function between the metal material and the transparent conductive material. In this embodiment, the pixel electrode 11 and the counter electrode 21 are formed from the same kind of electrode material (both are transparent conductive materials), thereby suppressing the occurrence of such flicker.

Note that, as described above, in a conventional general reflective liquid crystal display device, the pixel electrode also serves as a reflective layer, so a reflective layer cannot be disposed between pixels.

[Example of gradation display]
An example of a configuration for performing gradation display in the case of a memory liquid crystal will be described.

Each pixel P may be divided into a plurality of sub-pixels Sp, as shown in FIG. FIG. 3 shows an example in which one pixel P is divided into three sub-pixels Sp. In this example, the pixel electrode 11 is divided into three sub-pixel electrodes 11a. Of the three sub-pixel electrodes 11a, the two sub-pixel electrodes 11a arranged at the upper and lower sides in the figure are electrically connected to one common memory circuit, and are arranged at the center in the figure. One of the sub-pixel electrodes 11a is electrically connected to another memory circuit. That is, two memory circuits are provided for each pixel P.

By dividing the pixel P as shown in FIG. 3, it is possible to perform four-gradation display using the area coverage modulation method, as shown in FIG. Specifically, as shown on the leftmost side of FIG. 4, by setting all three sub-pixels Sp to a black display state, one pixel P as a whole can display black, and from the left side of FIG. As shown in the second figure, by setting two sub-pixels Sp to a black display state and one sub-pixel Sp to a white display state, one pixel P as a whole can perform a dark halftone display. Furthermore, as shown third from the left in FIG. 4, by setting two sub-pixels Sp to a white display state and setting one sub-pixel Sp to a black display state, one pixel P as a whole displays a bright halftone. As shown on the rightmost side of FIG. 4, by setting all three sub-pixels Sp to a white display state, one pixel P as a whole can display white.

Note that the three sub-pixel electrodes 11a may be electrically connected to separate memory circuits (that is, each pixel P may be provided with three memory circuits).

[Verification results of improvement effect on reflective aperture ratio and reflectance]
The results of fabricating the liquid crystal display device 100 of this embodiment (Example 1) and verifying the effect of improving the reflective aperture ratio and reflectance will be described. The screen size of the manufactured liquid crystal display device 100 was 1.2 inches, and the size of one pixel P was 126 μm long×42 μm wide. Of the first alignment film 15 of the TFT substrate 10 and the second alignment film 25 of the counter substrate 20, only the second alignment film 25 was subjected to the rubbing treatment. Therefore, of the first alignment film 15 and the second alignment film 25, only the second alignment film 25 defines the pretilt orientation. The thickness (cell gap) of the liquid crystal layer 30 is 3 μm, and a chiral agent is added to the liquid crystal material of the liquid crystal layer 30 so that the twist angle is 70° when a white voltage is applied (that is, the liquid crystal molecules are horizontally aligned). was added. The driving method is field inversion driving (method (C)).

In addition to Example 1, liquid crystal display devices of Comparative Example 1 and Comparative Example 2 were also produced and compared with Example 1. A liquid crystal display device 900 of Comparative Example 1 is shown in FIGS. 5, 6A, and 6B. FIG. 5 is a plan view showing the liquid crystal display device 900, and shows areas corresponding to three pixels P of the liquid crystal display device 900. 6A and 6B are cross-sectional views showing the liquid crystal display device 900, and show cross-sectional structures taken along lines 6A-6A' and 6B-6B' in FIG. 5, respectively.

The liquid crystal display device 900 of Comparative Example 1 has a feature that a reflective layer (reflective electrode) 912 that also serves as a pixel electrode is provided on the second interlayer insulating layer 14, as shown in FIGS. 5, 6A, and 6B. This is different from the liquid crystal display device 100 of this embodiment. The reflective electrode 912 includes a region 912a located within each pixel P, but does not include a region located between adjacent pixels P. Here, the liquid crystal display device 900 was used as a reflective liquid crystal display device. Further, the driving method of the liquid crystal display device 900 is field inversion driving.

The liquid crystal display device of Comparative Example 2 has the same pixel structure (electrode structure) as the liquid crystal display device 100 of Example 1, but differs from Example 1 in that dot inversion driving is performed.

Table 1 shows the reflective aperture ratios and reflectances obtained for Comparative Example 1, Comparative Example 2, and Example 1.

As can be seen from Table 1, in Example 1, the reflective aperture ratio and reflectance are improved compared to Comparative Example 1, and it can be seen that both the reflective aperture ratio and reflectance are improved. Further, in Comparative Example 2, although the reflective aperture ratio was improved compared to Comparative Example 1, the improvement in reflectance was slight. From this, when voltages of different polarities are applied to two adjacent pixels P, even if the reflective layer 12 is located between the pixels P, the liquid crystal molecules between the pixels P do not contribute much to improving brightness. This was confirmed.

[Other aspects]
Although a backplane circuit having a memory circuit for each pixel P is illustrated here, the backplane circuit is not limited to this example. The backplane circuit may include a TFT connected to the pixel electrode 11, a gate bus line connected to the TFT, a source bus line, etc., like a general active matrix substrate. The TFT is, for example, a TFT (see Japanese Unexamined Patent Publication No. 2014-007399) that has an amorphous silicon layer, a polysilicon layer, or an oxide semiconductor layer containing an In-Ga-Zn-O-based semiconductor as an active layer. JP 2014-007399 is incorporated herein by reference.

Note that, as Example 1, a VA-HAN mode in which only one vertical alignment film regulates the pretilt orientation is illustrated, but a VA-TN mode in which both vertical alignment films regulate the pretilt orientation may be used. Further, as the first alignment film 15 and the second alignment film 25, a horizontal alignment film may be used instead of the vertical alignment film. Further, instead of the nematic liquid crystal material having negative dielectric anisotropy, the liquid crystal layer 30 may include a nematic liquid crystal material having positive dielectric anisotropy (that is, positive type), or may contain no chiral agent. It's okay.

(Embodiment 2)
The liquid crystal display device 200 in this embodiment will be described with reference to FIGS. 7, 8A, and 8B. The liquid crystal display device 200 of this embodiment is a transflective liquid crystal display device. FIG. 7 is a plan view schematically showing the liquid crystal display device 200, and shows areas corresponding to three pixels P of the liquid crystal display device 200. 8A and 8B are cross-sectional views schematically showing the liquid crystal display device 200, and show cross-sectional structures taken along lines 8A-8A' and 8B-8B' in FIG. 7, respectively. In the following, the differences between the liquid crystal display device 200 of the present embodiment and the liquid crystal display device 100 of the first embodiment will be mainly explained.

The liquid crystal display device 200 of the present embodiment differs from the liquid crystal display device 100 of the first embodiment in that each of the plurality of pixels P includes a transmissive region Tr for displaying in a transmissive mode in addition to the reflective region Rf. . A part of the pixel electrode 11 is located within the transmission region Tr. In the illustrated example, the transparent region Tr is located at the center of the pixel P. Here, the thickness dt of the liquid crystal layer 30 in the transmission region Tr and the thickness dr of the liquid crystal layer 30 in the reflection region Rf are the same (that is, dt=dr).

The area ratio of the transmissive region Tr in the pixel P can be set as appropriate depending on the application, and is, for example, 20% or more and 90% or less. Furthermore, the position and shape of the transparent region Tr within the pixel P can be set as appropriate depending on the purpose and the like.

Also in the liquid crystal display device 200 of this embodiment, since the reflective layer 12 includes the second region 12b located between two adjacent pixels P, the region between the pixels P can also contribute to reflective display. can. Therefore, the reflection aperture ratio is improved, and the reflectance can be further improved.

Furthermore, the liquid crystal display device 200 of this embodiment can solve the following problems in conventional transflective liquid crystal display devices.

2. Description of the Related Art As a transflective liquid crystal display device, a configuration in which a region between adjacent pixels is used for display in a transmissive mode is known. However, since there is no pixel electrode between the pixels, the liquid crystal molecules located between the pixels cannot be sufficiently aligned in a desired direction, resulting in a problem of low transmittance. Furthermore, the area between the pixels includes a region where alignment due to an oblique electric field generated near the edge of the pixel electrode and alignment due to rubbing treatment are not well matched, and the alignment of liquid crystal molecules is unstable. Since such a region in which the alignment between pixels is unstable is used for display in the transmissive mode, display defects (such as afterimages) due to poor alignment occur in the display in the transmissive mode. Furthermore, the change in orientation due to the uneven surface structure of the reflective electrode extends to the region between pixels (the region used for transmissive display), which also causes display defects.

On the other hand, in the liquid crystal display device 200 of this embodiment, since the pixel electrode 11 exists within the transmissive region Tr, the liquid crystal molecules within the transmissive region Tr can be sufficiently aligned in a desired direction. Therefore, the transmittance is improved.

Furthermore, it is possible to use a region with stable orientation for display in a transmission mode, and it is not necessary for the pixel electrode 11 to have an uneven surface structure (the reflective layer 12 separated from the pixel electrode 11 has an uneven surface structure). Therefore, display defects caused by alignment defects in transmission mode display can be improved.

Here, the results of verifying the effects of this embodiment will be explained. The effect was verified by manufacturing the liquid crystal display device 200 of this embodiment (Example 2) and comparing it with Comparative Example 3. Comparative Example 3 is an example in which the liquid crystal display device 900 shown in FIG. 5 etc. is used as a transflective liquid crystal display device, and the gap between the pixel electrodes 912 is used for display in a transmissive mode.

Table 2 shows the results of verifying the reflectance and transmittance and the degree of occurrence of afterimages for Comparative Example 3 and Example 2. The reflectance and transmittance are relative values with the reflectance and transmittance of Comparative Example 3 being 1.0. The degree of occurrence of afterimages was verified by visual observation, and cases in which the occurrence of afterimages was sufficiently suppressed were marked as "○", and cases in which they were not sufficiently suppressed were marked as "x".

As can be seen from Table 2, in Example 2, while maintaining the reflectance and transmittance equivalent to Comparative Example 3, it was possible to sufficiently suppress the occurrence of afterimages due to poor alignment. Therefore, according to this embodiment, it is possible to improve the display quality and yield of a transflective liquid crystal display device.

(Embodiment 3)
The liquid crystal display device 300 in this embodiment will be described with reference to FIGS. 9, 10A, and 10B. The liquid crystal display device 300 of this embodiment is a transflective liquid crystal display device. FIG. 9 is a plan view schematically showing the liquid crystal display device 300, and shows areas corresponding to three pixels P of the liquid crystal display device 300. 10A and 10B are cross-sectional views schematically showing the liquid crystal display device 300, and show cross-sectional structures taken along lines 10A-10A' and 10B-10B' in FIG. 9, respectively. In the following, the differences between the liquid crystal display device 300 of the present embodiment and the liquid crystal display device 200 of the second embodiment will be mainly explained.

In the liquid crystal display device 300 of this embodiment, as shown in FIGS. 9, 10A, and 10B, the thickness dt of the liquid crystal layer 30 in the transmission region Tr is larger than the thickness dr of the liquid crystal layer 30 in the reflection region Rf. This is different from the liquid crystal display device 200 of the second embodiment in that (that is, dt>dr). Specifically, by forming the second contact hole CH2 in the second interlayer insulating layer 14 to be larger than the second contact hole CH2 in the liquid crystal display device 200 of the second embodiment, the cell gap dt of the transmissive region Tr is It is larger than the cell gap dr of the reflection region Rf.

The light used for display in the transmission mode passes through the liquid crystal layer 30 only once, whereas the light used for display in the reflection mode passes through the liquid crystal layer 30 twice. Therefore, as in the present embodiment, when the cell gap dt of the transmissive region Tr is larger than the cell gap dr of the reflective region Rf, the liquid crystal layer 30 with respect to light used for transmissive mode display and light used for reflective mode display retardation can be made close to each other, and a voltage-luminance characteristic that is preferable for both the transmission region Tr and the reflection region Rf (brighter display can be realized) can be obtained.

From the viewpoint of achieving brighter display in both the transmissive region Tr and the reflective region Rf, the cell gap dt of the transmissive region Tr and the cell gap dr of the reflective region Rf should substantially satisfy the relationship dt=2dr. is preferred.

As described in Embodiment 1, only one of the first alignment film 15 and the second alignment film 16 is subjected to alignment treatment (e.g., rubbing treatment) so that the liquid crystal molecules are aligned in a twisted manner when a voltage is applied. If the regulation is performed in this embodiment, it may not be possible to simultaneously achieve the optimal (specifically, brighter) orientation state for both regions due to the difference in cell gap between the transmission region Tr and the reflection region Rf. . Therefore, in this embodiment, a chiral agent may not be added to the liquid crystal material of the liquid crystal layer 30, and the twist angle at the time of voltage application may be set to 0°.

Alternatively, the twist angle at the time of voltage application may be made different between the transmission region Tr and the reflection region Rf. At least one of the first alignment film 15 and the second alignment film 25 defines different pretilt directions in the transmission region Tr and the reflection region Rf, so that the twist angle at the time of voltage application is controlled in the transmission region Tr and the reflection region Rf. can be made different. In this case, it is preferable that the alignment treatment for the alignment film (at least one of the first alignment film 15 and the second alignment film 25) is performed by photo-alignment treatment.

Here, the results of verifying the effects of this embodiment will be explained. The effect was verified by manufacturing a liquid crystal display device 300 of this embodiment (Example 3) and comparing it with Example 2. In Example 3, no chiral agent was added to the liquid crystal material, and the twist angle at the time of voltage application was set to 0°. The cell gap dr of the reflective region Rf was 2.0 μm, and the cell gap dt of the transmissive region Tr was 4.0 μm.

Table 3 shows the reflectance and transmittance of Example 2 and Example 3. The reflectance and transmittance are relative values based on the reflectance and transmittance of Example 2 being 1.0. Further, Table 3 shows the results when Example 3 was manufactured so that the reflectance of Example 3 was the same as the reflectance of Example 2.

Table 3 shows that in Example 3, the transmittance is improved compared to Example 2 while maintaining the same reflectance as in Example 2. This is an effect due to the fact that the cell gap dt in the transmissive region Tr is larger than the cell gap dr in the reflective region Rf.

Table 4 shows the results when Example 3 was manufactured so that the transmittance of Example 3 was the same as that of Example 2.

Table 4 shows that in Example 3, the reflectance is improved compared to Example 2 while maintaining the same transmittance as in Example 2. This is because in Example 3, even if the transmission region Tr is narrower than in Example 2, the same transmittance as in Example 2 can be obtained, so the reflection region Rf could be made wider than in Example 2. .

(Embodiment 4)
The liquid crystal display device 400 in this embodiment will be described with reference to FIGS. 11, 12A, and 12B. The liquid crystal display device 400 of this embodiment is a transflective liquid crystal display device. FIG. 11 is a plan view schematically showing the liquid crystal display device 400, and shows areas corresponding to three pixels P of the liquid crystal display device 400. 12A and 12B are cross-sectional views schematically showing the liquid crystal display device 400, and show cross-sectional structures taken along lines 12A-12A' and 12B-12B' in FIG. 11, respectively. Below, the explanation will focus on the differences between the liquid crystal display device 400 of this embodiment and the liquid crystal display device 200 of the second embodiment.

In the liquid crystal display device 400 of this embodiment shown in FIGS. 11, 12A, and 12B, the pixel electrode 11 and the backplane circuit are electrically connected in the first contact hole CH1 and the second contact hole CH2 formed in the transmissive region Tr. This embodiment is different from the liquid crystal display device 200 of Embodiment 2 in that the contact portions CP that are connected to each other are formed of a transparent conductive material (that is, are transparent).

In this embodiment, the contact portion CP is composed of a first contact electrode 16 and a second contact electrode 17. That is, unlike the contact portion CP of the liquid crystal display device 200 of the second embodiment, the contact portion CP of the liquid crystal display device 400 does not include the third contact electrode 18 formed from the same metal film as the reflective layer 12. Further, the first contact electrode 16 and the second contact electrode 17 included in the contact portion CP of the liquid crystal display device 400 are both formed from a transparent conductive material. Therefore, the contact portion CP of the liquid crystal display device 400 is transparent as a whole. Note that the same material as the pixel electrode 11 and the like can be used as the transparent conductive material for forming the first contact electrode 16 and the second contact electrode 17.

In this way, in the liquid crystal display device 400 of this embodiment, since the contact portion CP is formed from a transparent conductive material, the region where the contact portion CP is provided can be used for display in a transmissive mode (that is, in a transmissive mode). (can be made to function suitably as a region Tr). Therefore, the transmittance can be further improved than that of the liquid crystal display device 200 of the second embodiment.

Here, the results of verifying the effects of this embodiment will be explained. The effect was verified by manufacturing a liquid crystal display device 400 of this embodiment (Example 4) and comparing it with Example 2.

Table 5 shows the reflectance and transmittance of Example 2 and Example 4. The reflectance and transmittance are relative values based on the reflectance and transmittance of Example 2 being 1.0. Further, Table 5 shows the results when Example 4 was manufactured so that the reflectance of Example 4 was the same as the reflectance of Example 2.

Table 5 shows that in Example 4, the transmittance is improved compared to Example 2 while maintaining the same reflectance as Example 2. This is an effect caused by the region where the contact portion CP is provided functioning as the transmission region Tr.

Table 6 shows the results when Example 4 was manufactured so that the transmittance of Example 4 was the same as that of Example 2.

Table 6 shows that in Example 4, the reflectance is improved compared to Example 2 while maintaining the same transmittance as in Example 2. This is because in Example 4, even if the transmission region Tr is narrower than in Example 2, the same transmittance as in Example 2 can be obtained, so the reflection region Rf could be made wider than in Example 2. .

(Embodiment 5)
A liquid crystal display device 500 in this embodiment will be described with reference to FIGS. 13, 14A, and 14B. The liquid crystal display device 500 of this embodiment is a transflective liquid crystal display device. FIG. 13 is a plan view schematically showing the liquid crystal display device 500, and shows areas corresponding to three pixels P of the liquid crystal display device 500. 14A and 14B are cross-sectional views schematically showing the liquid crystal display device 500, and show cross-sectional structures taken along lines 14A-14A' and 14B-14B' in FIG. 13, respectively. Below, the explanation will focus on the differences between the liquid crystal display device 500 of this embodiment and the liquid crystal display device 200 of the second embodiment.

The liquid crystal display device 500 of this embodiment shown in FIGS. 13, 14A, and 14B is different from the liquid crystal display device 200 of the second embodiment in that the contact portion CP is formed of a transparent conductive material (that is, it is transparent). It is different from

In this embodiment, the contact portion CP does not include the third contact electrode 18 formed from the same metal film as the reflective layer 12. Further, the first contact electrode 16 and the second contact electrode 17 included in the contact portion CP are both formed from a transparent conductive material. Therefore, the contact portion CP of the liquid crystal display device 500 is transparent as a whole.

Furthermore, the liquid crystal display device 500 of the present embodiment has the following features in that the thickness dt of the liquid crystal layer 30 in the transmissive region Tr is larger than the thickness dr of the liquid crystal layer 30 in the reflective region Rf (that is, dt>dr). This is different from the liquid crystal display device 200 of No. 2. Specifically, by forming the second contact hole CH2 in the second interlayer insulating layer 14 to be larger than the second contact hole CH2 in the liquid crystal display device 200 of the second embodiment, the cell gap dt of the transmissive region Tr is It is larger than the cell gap dr of the reflection region Rf.

In this way, in the liquid crystal display device 500 of this embodiment, since the contact portion CP is formed of a transparent conductive material, the region where the contact portion CP is provided can be used for display in a transmissive mode (that is, in a transmissive mode). (can be made to function suitably as a region Tr). Therefore, the transmittance can be further improved than that of the liquid crystal display device 200 of the second embodiment.

Further, in this embodiment, since the cell gap dt of the transmission region Tr is larger than the cell gap dr of the reflection region Rf, the retardation of the liquid crystal layer 30 with respect to the light used for transmission mode display and the light used for reflection mode display is can be made close to each other, and a voltage-luminance characteristic that is preferable for both the transmission region Tr and the reflection region Rf (brighter display can be realized) can be obtained.

Here, the results of verifying the effects of this embodiment will be explained. The effect was verified by manufacturing a liquid crystal display device 500 of this embodiment (Example 5) and comparing it with Example 2.

Table 7 shows the reflectance and transmittance of Example 2 and Example 5. The reflectance and transmittance are relative values based on the reflectance and transmittance of Example 2 being 1.0. Further, Table 7 shows the results when Example 5 was manufactured so that the reflectance of Example 5 was the same as the reflectance of Example 2.

From Table 7, it can be seen that in Example 5, the transmittance was significantly improved compared to Example 2 while maintaining the same reflectance as in Example 2. This is an effect due to the fact that the region where the contact portion CP is provided functions as the transmissive region Tr, and the cell gap dt of the transmissive region Tr is larger than the cell gap dr of the reflective region Rf.

Table 8 shows the results when Example 5 was manufactured so that the area of the transmission region Tr of Example 5 was set to the minimum (approximately the area of the contact portion CP) and the reflectance was maximized.

Table 8 shows that in Example 5, the transmittance can be made higher than in Example 2 even if the area of the transmission region Tr is the smallest. Furthermore, since the area of the reflective region Rf can be increased, the reflectance is improved.

(Embodiment 6)
A liquid crystal display device 600 in this embodiment will be described with reference to FIGS. 15, 16A, and 16B. The liquid crystal display device 600 of this embodiment is a reflective liquid crystal display device. FIG. 15 is a plan view schematically showing the liquid crystal display device 600, and shows areas corresponding to three pixels P of the liquid crystal display device 600. 16A and 16B are cross-sectional views schematically showing the liquid crystal display device 600, and show cross-sectional structures taken along lines 16A-16A' and 16B-16B' in FIG. 15, respectively. Note that illustration of the substrate 20a is omitted in FIGS. 16A and 16B. Below, the explanation will focus on the differences between the liquid crystal display device 600 of this embodiment and the liquid crystal display device 100 of the first embodiment.

The counter substrate 20 of the liquid crystal display device 600 includes a red color filter (first color filter) 22R that transmits a first color light (here, red light) and a second color light (here, green light). The color filter layer 22 includes a green color filter (second color filter) 22G that transmits light of a third color (here, blue light) and a blue color filter (third color filter) 22B that transmits light of a third color (here, blue light). In this embodiment, the counter substrate 20 includes a colorless region Clr in which none of the red color filter 22R, the green color filter 22G, and the blue color filter 22B are provided, as shown in FIG. 16A. When viewed from the normal direction of the display surface, the colorless region Clr overlaps at least a portion of the second region 12b of the reflective layer 12. In the illustrated example, the red color filter 22R, the green color filter 22G, and the blue color filter 22B have a stripe shape extending along the column direction, and the colorless region Clr is formed along the row direction among the plurality of pixels. It is located between any two pixels adjacent to each other. Further, when viewed from the normal direction of the display surface, the colorless region Clr does not overlap the pixel electrode 11.

The color filter or black matrix arranged so as to overlap the second region 12b of the reflective layer 12 becomes a factor that reduces the reflectance. As in this embodiment, when the counter substrate 20 includes the colorless region Clr overlapping at least a portion of the second region 12b of the reflective layer 12, the reflectance can be improved. Further, by arranging the colorless region Clr so as not to overlap the pixel electrode 11, it is possible to suppress a decrease in color purity during monochrome display.

The liquid crystal display device 600 of this embodiment was manufactured (Example 6), and the results of verifying the reflectance improvement effect and color reproduction range (NTSC ratio) will be described. The screen size of the manufactured liquid crystal display device 600 was 1.2 inches, and the size of one pixel P was 126 μm long×42 μm wide. Of the first alignment film 15 of the TFT substrate 10 and the second alignment film 25 of the counter substrate 20, only the second alignment film 25 was subjected to the rubbing treatment. Therefore, of the first alignment film 15 and the second alignment film 25, only the second alignment film 25 defines the pretilt orientation. The thickness (cell gap) of the liquid crystal layer 30 is 3 μm, and a chiral agent is added to the liquid crystal material of the liquid crystal layer 30 so that the twist angle is 70° when a white voltage is applied (that is, the liquid crystal molecules are horizontally aligned). was added. The driving method is field inversion driving (method (C)). The width w1 of the colorless region Clr along the row direction was 2.0 μm, and the interval w2 between adjacent pixel electrodes 11 along the row direction was 2.5 μm.

In addition to Example 6, a liquid crystal display device 700 of Example 7 shown in FIG. 17 was also produced and compared with Example 6. The liquid crystal display device 700 of Example 7 has the same configuration as Example 6, except that the counter substrate 20 does not have the colorless region Clr.

Table 9 shows the reflectances and NTSC ratios (relative ratios) obtained for Examples 6 and 7.

Table 9 shows that in Example 6, the reflectance is improved more than in Example 7. Further, from Table 9, it can be seen that in Example 6, a color reproduction range equivalent to that in Example 7 was obtained. In this way, it was confirmed that the reflectance can be improved by providing the colorless region Clr, and that by not overlapping the colorless region Clr with the pixel electrode 11, it is possible to suppress a decrease in color purity during monochrome display. Note that although the description has been given here taking a reflective type liquid crystal display device as an example, similar effects can be obtained in a transflective type liquid crystal display device.

(Embodiment 7)
A liquid crystal display device 800 in this embodiment will be described with reference to FIGS. 18, 19A, and 19B. The liquid crystal display device 800 of this embodiment is a reflective liquid crystal display device. FIG. 18 is a plan view schematically showing the liquid crystal display device 800, and shows areas corresponding to three pixels P of the liquid crystal display device 800. 19A and 19B are cross-sectional views schematically showing the liquid crystal display device 800, and show cross-sectional structures taken along lines 19A-19A' and 19B-19B' in FIG. 18, respectively. Below, the explanation will focus on the differences between the liquid crystal display device 800 of this embodiment and the liquid crystal display device 100 of the first embodiment.

The reflective layer 12 of the liquid crystal display device 800 is formed on the first interlayer insulating layer 13 that does not have an uneven shape (that is, is flat). Therefore, the reflective layer 12 does not have an uneven surface structure and functions as a specular reflective layer.

The liquid crystal display device 800 further includes a circularly polarizing plate 40 placed on the viewer's side of the counter substrate 20 and a light scattering layer 41 placed on the viewer's side of the liquid crystal layer 30 . The light scattering layer 41 is, for example, an anisotropic light scattering film. In the illustrated example, the light scattering layer 41 is arranged between the substrate 20a and the circularly polarizing plate 40.

In this embodiment, the light is scattered by the light scattering layer 41, so that a display close to paper white can be realized.

(Embodiment 8)
The liquid crystal display device 1000 in this embodiment will be described with reference to FIGS. 20, 21A, and 22B. The liquid crystal display device 1000 of this embodiment is a transflective liquid crystal display device. FIG. 20 is a plan view schematically showing the liquid crystal display device 1000, and shows areas corresponding to three pixels P of the liquid crystal display device 1000. 21A and 21B are cross-sectional views schematically showing the liquid crystal display device 1000, and show cross-sectional structures taken along lines 21A-21A' and 21B-21B' in FIG. 20, respectively. Below, the explanation will focus on the differences between the liquid crystal display device 1000 of this embodiment and the liquid crystal display device 800 of the seventh embodiment.

The liquid crystal display device 1000 of the present embodiment differs from the liquid crystal display device 800 of the seventh embodiment in that each of the plurality of pixels P includes a transmissive region Tr for displaying in a transmissive mode in addition to the reflective region Rf. . A part of the pixel electrode 11 is located within the transmission region Tr. In the illustrated example, the transparent region Tr is located at the center of the pixel P. Furthermore, the liquid crystal display device 1000 includes an additional circularly polarizing plate 42 arranged on the back side of the TFT substrate 10.

In the liquid crystal display device 1000 of this embodiment as well, although the reflective layer 12 does not have an uneven surface structure, light is scattered by the light scattering layer 41, so that a display close to paper white can be realized.

(Arrangement of light scattering layer)
19A, FIG. 19B, FIG. 21A, and FIG. 21B illustrate the arrangement in which the light scattering layer (anisotropic light scattering film) 41 is located between the substrate 20a and the circularly polarizing plate 40, but the arrangement of the light scattering layer 41 is not limited to this example.

FIG. 22A shows another example of the arrangement of the light scattering layer 41. In the example shown in FIG. 22A, the light scattering layer 41 is placed on the viewer's side of the circularly polarizing plate 40.

FIG. 22B shows still another example of the arrangement of the light scattering layer 41. In the example shown in FIG. 22B, the circularly polarizing plate 40 is composed of a linearly polarizing plate 40a and a retardation layer 40b provided on the back side of the linearly polarizing plate 40a, and the light scattering layer 41 is composed of a linearly polarizing plate 40a. 40a and the retardation layer 40b. Note that two or more retardation layers 40b may be provided.

FIG. 22C shows still another example of the arrangement of the light scattering layer 41. In the example shown in FIG. 22C, the circularly polarizing plate 40 includes a linearly polarizing plate 40a, a λ/2 plate 40b1 provided on the back side of the linearly polarizing plate 40a, and a λ/2 plate 40b1 provided on the back side of the λ/2 plate 40b1. /4 plate 40b2, and the light scattering layer 41 is arranged between λ/2 plate 40b1 and λ/4 plate 40b2. Note that two λ/2 plates 40b1 may be provided.

(Embodiment 9)
The liquid crystal display device 1100 in this embodiment will be described with reference to FIGS. 23, 24A, and 24B. The liquid crystal display device 1100 of this embodiment is a reflective liquid crystal display device. FIG. 23 is a plan view schematically showing the liquid crystal display device 1100, and shows areas corresponding to three pixels P of the liquid crystal display device 1100. 24A and 24B are cross-sectional views schematically showing the liquid crystal display device 1100, and show cross-sectional structures taken along lines 24A-24A' and 24B-24B' in FIG. 23, respectively. Below, the explanation will focus on the differences between the liquid crystal display device 1100 of this embodiment and the liquid crystal display device 100 of the first embodiment.

Liquid crystal layer 30 of liquid crystal display device 1100 includes liquid crystal molecules 31 and dichroic dye 32. In other words, the liquid crystal display device 1100 is of a so-called guest-host type. The color of the dichroic dye is, for example, black. The amount of dichroic dye added to the liquid crystal material is, for example, 3% by weight. When no voltage is applied to the liquid crystal layer 30, the liquid crystal molecules 31 and the dichroic dye 32 are horizontally aligned, and black display is performed in this state. When a predetermined voltage is applied to the liquid crystal layer 30, the liquid crystal molecules 31 and the dichroic dye 32 are vertically aligned, and white display is performed in this state. The guest-host type liquid crystal display device 1100 does not require a polarizing plate. Therefore, the brightness of the display is improved. Note that the second interlayer insulating layer 14 has substantially no phase difference.

(Embodiment 10)
The liquid crystal display device 1200 in this embodiment will be described with reference to FIGS. 25, 26A, and 26B. The liquid crystal display device 1200 of this embodiment is a reflective liquid crystal display device. FIG. 25 is a plan view schematically showing the liquid crystal display device 1200, and shows areas corresponding to three pixels P of the liquid crystal display device 1200. 26A and 26B are cross-sectional views schematically showing the liquid crystal display device 1200, and show cross-sectional structures taken along lines 26A-26A' and 26B-26B' in FIG. 25, respectively. The following will mainly explain the differences between the liquid crystal display device 1200 of this embodiment and the liquid crystal display device 1100 of the ninth embodiment.

The liquid crystal display device 1200 of this embodiment includes a retardation layer (in-cell retardation film) as the second interlayer insulating layer 14A that covers the reflective layer 12. Specifically, the retardation layer 14A functions as a λ/4 plate. For example, the slow axis of the retardation layer 14A functioning as a λ/4 plate is arranged to form an angle of approximately 45° with the absorption axis of the dichroic dye in a state where no voltage is applied. By providing the retardation layer 14A, the contrast ratio is improved.

(Embodiment 11)
The liquid crystal display device 1300 in this embodiment will be described with reference to FIGS. 27, 28A, and 28B. The liquid crystal display device 1300 of this embodiment is a transflective liquid crystal display device. FIG. 27 is a plan view schematically showing the liquid crystal display device 1300, and shows areas corresponding to three pixels P of the liquid crystal display device 1300. 28A and 28B are cross-sectional views schematically showing the liquid crystal display device 1300, and show cross-sectional structures taken along lines 28A-28A' and 28B-28B' in FIG. 27, respectively. Below, the explanation will focus on the differences between the liquid crystal display device 1300 of this embodiment and the liquid crystal display device 1200 of the tenth embodiment.

The liquid crystal display device 1300 of the present embodiment differs from the liquid crystal display device 1200 of the tenth embodiment in that each of the plurality of pixels P includes a transmissive region Tr for displaying in a transmissive mode in addition to the reflective region Rf. . A part of the pixel electrode 11 is located within the transmission region Tr. In the illustrated example, the transparent region Tr is located at the center of the pixel P. Note that the second interlayer insulating film 14 has substantially no phase difference.

The liquid crystal display device 1300 of this embodiment is also of a guest-host type. A polarizing plate is not required on the viewer side (front side) of the counter substrate 20. A polarizing plate may not be provided on the back side (back side) of the TFT substrate 10, or may be provided.

(Embodiment 12)
A liquid crystal display device 1400 in this embodiment will be described with reference to FIGS. 29, 30A, and 30B. The liquid crystal display device 1400 of this embodiment is a transflective liquid crystal display device. FIG. 29 is a plan view schematically showing the liquid crystal display device 1400, and shows areas corresponding to three pixels P of the liquid crystal display device 1400. 30A and 30B are cross-sectional views schematically showing the liquid crystal display device 1400, and show cross-sectional structures taken along lines 30A-30A' and 30B-30B' in FIG. 29, respectively. Below, the explanation will focus on the points in which the liquid crystal display device 1400 of this embodiment differs from the liquid crystal display device 1300 in the eleventh embodiment.

The liquid crystal display device 1400 of this embodiment includes a retardation layer (in-cell retardation film) as the second interlayer insulating layer 14A that covers the reflective layer 12. Further, the liquid crystal display device 1400 includes a circularly polarizing plate 42 provided on the back side of the TFT substrate 10. Specifically, the retardation layer 14A functions as a λ/4 plate. By providing the retardation layer 14A, the contrast ratio is improved.

Embodiments of the present invention can be widely applied to liquid crystal display devices (that is, reflective liquid crystal display devices and transflective liquid crystal display devices) in which each pixel includes a reflective region that performs display in a reflective mode.

10 TFT substrate 11 pixel electrode 11a sub-pixel electrode 12 reflective layer 12a first region 12b second region 13 first interlayer insulating layer 14, 14A second interlayer insulating layer 15 first alignment film 20 counter substrate 21 counter electrode 22 color filter layer 22R red color filter 22G green color filter 22B blue color filter 25 second alignment film 30 liquid crystal layer 31 liquid crystal molecules 32 dichroic dye 40 circularly polarizing plate 41 light scattering layer 42 circularly polarizing plate 100, 200, 300, 400, 500, 600, 700, 800 Liquid crystal display device 1000, 1100, 1200, 1300, 1400 Liquid crystal display device P Pixel Sp Sub-pixel Rf Reflective region Tr Transmissive region CP Contact portion Clr Colorless region

Claims (16)

a first substrate;
a second substrate facing the first substrate;
a liquid crystal layer provided between the first substrate and the second substrate;
Equipped with
A liquid crystal display device having a plurality of pixels arranged in a matrix including a plurality of rows and a plurality of columns,
Each of the plurality of pixels includes a reflective area that performs display in a reflective mode,
The first substrate includes a pixel electrode provided for each of the plurality of pixels, and a reflective layer located on a side opposite to the liquid crystal layer with respect to the pixel electrode,
The reflective layer includes a first region located within each of the plurality of pixels, and a second region located between any two pixels adjacent to each other among the plurality of pixels,
Any two pixels adjacent to each other along the row direction among the plurality of pixels, any two pixels adjacent to each other along the column direction among the plurality of pixels, or all of the plurality of pixels. A voltage of the same polarity is applied to the liquid crystal layer of the pixel ,
The first substrate further includes a transparent insulating layer provided to cover the reflective layer,
The pixel electrode is made of a transparent conductive material and is disposed on the transparent insulating layer,
Each of the plurality of pixels further includes a transparent area for displaying in a transparent mode,
A liquid crystal display device , wherein a part of the pixel electrode is located within the transmissive region . 2. The liquid crystal display device according to claim 1 , wherein the thickness of the liquid crystal layer in the transmissive region is greater than the thickness of the liquid crystal layer in the reflective region. The first substrate has a backplane circuit electrically connected to the pixel electrode, and a further transparent insulating layer provided to cover the backplane circuit,
the reflective layer is disposed on the further transparent insulating layer,
the further transparent insulating layer has a first contact hole formed in the transparent region;
The transparent insulating layer has a second contact hole formed in the transparent region,
The first substrate further includes a contact portion that electrically connects the pixel electrode and the backplane circuit in the first contact hole and the second contact hole,
3. The liquid crystal display device according to claim 1 , wherein the contact portion is made of a transparent conductive material. The first substrate has a first alignment film provided in contact with the liquid crystal layer,
The second substrate has a second alignment film provided in contact with the liquid crystal layer,
4. The liquid crystal display device according to claim 1 , wherein at least one of the first alignment film and the second alignment film defines different pretilt orientations in the transmission area and the reflection area. 5. The liquid crystal display device according to claim 4 , wherein the at least one of the first alignment film and the second alignment film is subjected to a photoalignment treatment. The second substrate has a counter electrode provided to face the pixel electrode,
6. The liquid crystal display device according to claim 1 , wherein the counter electrode is made of a transparent conductive material. The second substrate includes a first color filter that transmits light of a first color, a second color filter that transmits light of a second color, and a third color filter that transmits light of a third color. having a filter layer;
The second substrate includes a colorless area in which none of the first color filter, the second color filter, and the third color filter are provided,
7. The liquid crystal display device according to claim 1, wherein the colorless region overlaps at least a portion of the second region of the reflective layer when viewed from the normal direction of the display surface. 8. The liquid crystal display device according to claim 7, wherein the colorless region does not overlap the pixel electrode when viewed from the normal direction of the display surface. a first substrate;
a second substrate facing the first substrate;
a liquid crystal layer provided between the first substrate and the second substrate;
Equipped with
A liquid crystal display device having a plurality of pixels arranged in a matrix including a plurality of rows and a plurality of columns,
Each of the plurality of pixels includes a reflective area that performs display in a reflective mode,
The first substrate includes a pixel electrode provided for each of the plurality of pixels, and a reflective layer located on a side opposite to the liquid crystal layer with respect to the pixel electrode,
The reflective layer includes a first region located within each of the plurality of pixels, and a second region located between any two pixels adjacent to each other among the plurality of pixels,
Any two pixels adjacent to each other along the row direction among the plurality of pixels, any two pixels adjacent to each other along the column direction among the plurality of pixels, or all of the plurality of pixels. A voltage of the same polarity is applied to the liquid crystal layer of the pixel,
The second substrate includes a first color filter that transmits light of a first color, a second color filter that transmits light of a second color, and a third color filter that transmits light of a third color. having a filter layer;
The second substrate includes a colorless area in which none of the first color filter, the second color filter, and the third color filter are provided,
The liquid crystal display device, wherein the colorless region overlaps at least a portion of the second region of the reflective layer when viewed from the normal direction of the display surface. 10. The liquid crystal display device according to claim 9 , wherein the colorless region does not overlap the pixel electrode when viewed from the normal direction of the display surface. 11. The liquid crystal display device according to claim 1, wherein the second substrate does not have a black matrix between any two adjacent pixels among the plurality of pixels. 12. The liquid crystal display device according to claim 1, further comprising a memory circuit connected to each of the plurality of pixels. 13. The liquid crystal display device according to claim 1, wherein voltages of the same polarity are applied to the liquid crystal layer of all pixels of the plurality of pixels. 14. The liquid crystal display device according to claim 1, wherein each of the first region and the second region of the reflective layer has an uneven surface structure. 14. The liquid crystal display device according to claim 1, further comprising a light scattering layer disposed closer to a viewer than the liquid crystal layer. 16. The liquid crystal display device according to claim 1, wherein the liquid crystal layer contains liquid crystal molecules and a dichroic dye.

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