JP2023010591A - Liquid crystal display device - Google Patents

Abstract

To provide a liquid crystal display device that includes a reflection region for pixels to perform display in a reflection mode, in which the reflection rate is improved compared to a conventional one and display brighter than the conventional one is realized.SOLUTION: A liquid crystal display device comprises a first substrate, a second substrate, and a vertical alignment type liquid crystal layer. The first substrate includes a backplane circuit, a first interlayer insulating layer that covers the backplane circuit, a first reflection electrode which is provided on the first interlayer insulating layer and includes a first region located in each pixel and a second region located between two discretionary pixels adjacent to each other, a second interlayer insulting layer that covers the first reflection electrode, and a pixel electrode provided on the second interlayer insulting layer in each pixel. The pixel electrode is electrically connected to the backplane circuit in a first and second contact holes formed in the first and second interlayer insulating layers. The first substrate further includes a second reflection electrode provided on the second interlayer insulating layer that overlaps the first contact hole when seen from the display surface normal direction.SELECTED DRAWING: Figure 2B

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 area.

Liquid crystal display devices are generally classified into transmissive liquid crystal display devices and reflective liquid crystal display devices. A transmissive liquid crystal display device performs transmissive mode display using light emitted from a backlight. A reflective liquid crystal display device performs display in a reflective mode using ambient light. Further, a liquid crystal display device has been proposed in which each pixel includes a reflective region for displaying in a reflective mode and a transmissive region for displaying in a transmissive mode. Such liquid crystal display devices are called transflective or transflective liquid crystal display devices.

Reflective and transflective liquid crystal display devices are suitably used, for example, as small and medium-sized display devices for mobile use outdoors. A reflective liquid crystal display device is disclosed in Patent Document 1, for example. A transflective liquid crystal display device is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2002-200021.

JP-A-2000-122094 Japanese Patent Application Laid-Open No. 2003-131268

Further improvement of light utilization efficiency (reflectance) in reflective mode display in reflective and semi-transmissive liquid crystal display devices, that is, in liquid crystal display devices including a region (reflective region) in which each pixel performs display in a reflective mode. (that is, to be able to provide a brighter display in reflective mode).

The embodiments of the present invention have been made in view of the above problems, and an object of the present invention is to improve the reflectance in a liquid crystal display device including a reflective region in which each pixel performs display in a reflective mode. To realize brighter display than

According to embodiments of the present invention, solutions are provided in the following items.

[Item 1]
a first substrate;
a second substrate facing the first substrate;
a vertically aligned liquid crystal layer provided between the first substrate and the second substrate;
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 displays in a reflective mode;
The first substrate is
a substrate;
a backplane circuit provided on the substrate and driving the plurality of pixels;
a first interlayer insulating layer provided to cover the backplane circuit;
A first reflective electrode provided on the first interlayer insulating layer, the first region positioned within each of the plurality of pixels, and arbitrary two pixels adjacent to each other among the plurality of pixels. a first reflective electrode including a second region positioned therebetween;
a second interlayer insulating layer provided to cover the first reflective electrode;
a pixel electrode formed of a transparent conductive material and provided on the second interlayer insulating layer in each of the plurality of pixels;
has
the pixel electrode is electrically connected to the backplane circuit through a first contact hole formed in the first interlayer insulating layer and a second contact hole formed in the second interlayer insulating layer;
The liquid crystal display device, wherein the first substrate further includes a second reflective electrode provided on the second interlayer insulating layer so as to overlap the first contact hole when viewed from the direction normal to the display surface.

[Item 2]
The liquid crystal display device according to item 1, wherein the first reflective electrode has an uneven surface structure in each of the first region and the second region.

[Item 3]
3. The liquid crystal display device according to item 2, wherein the second reflective electrode has an uneven surface structure.

[Item 4]
The liquid crystal display device according to item 1, further comprising a light scattering layer arranged closer to the viewer than the liquid crystal layer.

[Item 5]
5. The liquid crystal display device according to item 4, wherein the first reflective electrode and the second reflective electrode do not have an uneven surface structure.

[Item 6]
the first substrate further includes a third reflective electrode provided on the first interlayer insulating layer so as to overlap the second contact hole when viewed from the direction normal to the display surface;
Item 6. The liquid crystal display device according to item 5, wherein the third reflective electrode does not have an uneven surface structure.

[Item 7]
7. The liquid crystal display device according to any one of items 1 to 6, wherein the second reflective electrode is electrically connected to the pixel electrode.

[Item 8]
each of the plurality of pixels further includes a transmissive region for displaying in a transmissive mode;
8. The liquid crystal display device according to any one of items 1 to 7, wherein part of the pixel electrode is located within the transmissive region.

[Item 9]
9. The liquid crystal display device according to any one of items 1 to 8, wherein the backplane circuit includes a memory circuit connected to each of the plurality of pixels.

[Item 10]
a first substrate;
a second substrate facing the first substrate;
a vertically aligned liquid crystal layer provided between the first substrate and the second substrate;
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 displays in a reflective mode;
The first substrate is
a substrate;
a backplane circuit provided on the substrate and driving the plurality of pixels;
a first interlayer insulating layer provided to cover the backplane circuit;
A first reflective electrode provided on the first interlayer insulating layer, the first region positioned within each of the plurality of pixels, and arbitrary two pixels adjacent to each other among the plurality of pixels. a first reflective electrode including a second region located therebetween;
a second interlayer insulating layer provided to cover the first reflective electrode;
a pixel electrode formed of a transparent conductive material and provided on the second interlayer insulating layer in each of the plurality of pixels;
has
the pixel electrode is electrically connected to the backplane circuit through a first contact hole formed in the first interlayer insulating layer and a second contact hole formed in the second interlayer insulating layer;
The first substrate is
a third interlayer insulating layer provided in the second contact hole;
a second reflective electrode provided on the third interlayer insulating layer so as to overlap at least the second contact hole when viewed from the direction normal to the display surface;
A liquid crystal display device further comprising:

[Item 11]
the second contact hole and the third interlayer insulating layer overlap the first contact hole when viewed from the direction normal to the display surface;
11. The liquid crystal display device according to item 10, wherein the second reflective electrode also overlaps with the first contact hole when viewed from the direction normal to the display surface.

[Item 12]
12. The liquid crystal display device according to item 10 or 11, wherein the first reflective electrode has an uneven surface structure in each of the first region and the second region.

[Item 13]
13. The liquid crystal display device according to Item 12, wherein the second reflective electrode has an uneven surface structure.

[Item 14]
12. The liquid crystal display device according to item 10 or 11, further comprising a light scattering layer arranged closer to the viewer than the liquid crystal layer.

[Item 15]
15. The liquid crystal display device according to item 14, wherein the first reflective electrode and the second reflective electrode each do not have an uneven surface structure.

[Item 16]
16. The liquid crystal display device according to any one of Items 10 to 15, wherein the second reflective electrode is electrically connected to the pixel electrode.

[Item 17]
17. The liquid crystal display device according to any one of items 10 to 16, wherein each of the plurality of pixels further includes a transmissive region displaying in a transmissive mode.

[Item 18]
18. A liquid crystal display device according to item 17, wherein the transmissive area is not light-shielded by the backplane circuit.

[Item 19]
19. The liquid crystal display device according to any one of items 10 to 18, wherein the backplane circuit includes a memory circuit connected to each of the plurality of pixels.

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

1 is a plan view schematically showing a liquid crystal display device 100 according to an embodiment of the present invention, showing regions corresponding to three pixels P of the liquid crystal display device 100. FIG. FIG. 2 is a cross-sectional view schematically showing the liquid crystal display device 100, showing a cross-sectional structure along line 2A-2A' in FIG. FIG. 2 is a cross-sectional view schematically showing the liquid crystal display device 100, showing a cross-sectional structure along line 2B-2B' in FIG. 2 is a diagram showing an example of gradation display using the configuration illustrated in FIG. 1; FIG. FIG. 3 is a cross-sectional view schematically showing a liquid crystal display device 900 of a comparative example; FIG. 3 is a cross-sectional view schematically showing a liquid crystal display device 900 of a comparative example; FIG. 3 is a plan view schematically showing another liquid crystal display device 200 according to an embodiment of the present invention, showing regions corresponding to three pixels P of the liquid crystal display device 200. FIG. FIG. 6 is a cross-sectional view schematically showing the liquid crystal display device 200, showing the cross-sectional structure along line 6A-6A' in FIG. FIG. 6 is a cross-sectional view schematically showing the liquid crystal display device 200, showing a cross-sectional structure along line 6B-6B' in FIG. FIG. 3 is a plan view schematically showing still another liquid crystal display device 300 according to an embodiment of the present invention, showing regions corresponding to three pixels P of the liquid crystal display device 300. FIG. FIG. 8 is a cross-sectional view schematically showing the liquid crystal display device 300, showing a cross-sectional structure along line 8A-8A' in FIG. FIG. 8 is a cross-sectional view schematically showing the liquid crystal display device 300, showing the cross-sectional structure along line 8B-8B' in 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 regions corresponding to three pixels P of the liquid crystal display device 400. FIG. FIG. 5 is a plan view schematically showing still another liquid crystal display device 500 according to an embodiment of the present invention, showing regions corresponding to three pixels P of the liquid crystal display device 500. FIG. FIG. 11 is a cross-sectional view schematically showing the liquid crystal display device 500, showing the cross-sectional structure along line 11A-11A' in FIG. FIG. 11 is a cross-sectional view schematically showing the liquid crystal display device 500, showing the cross-sectional structure along line 11B-11B' in FIG.

Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following embodiment.

(Embodiment 1)
A liquid crystal display device 100 according to the present embodiment will be described with reference to FIGS. 1, 2A and 2B. The liquid crystal display device 100 of the present embodiment is a transflective (transmissive/reflective) liquid crystal display device. FIG. 1 is a plan view schematically showing the liquid crystal display device 100, showing regions corresponding to three pixels P of the liquid crystal display device 100. FIG. 2A and 2B are cross-sectional views schematically showing the liquid crystal display device 100, showing cross-sectional structures 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. A 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 red pixels P _R that display red, green pixels P _G that display green, and blue pixels P _B that display blue.

2A and 2B, 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 the counter substrate. 20 and a vertical alignment type liquid crystal layer 30 provided between them. Each pixel P includes a reflective region Rf for display in a reflective mode and a transmissive region Tr for display in a transmissive mode. In the illustrated example, the thickness (cell gap) dt of the liquid crystal layer 30 in the transmissive region Tr and the thickness (cell gap) dr of the liquid crystal layer 30 in the reflective region Rf are the same (that is, dt=dr). . The ratio of the area of the transmissive region Tr within the pixel P can be appropriately set depending on the application, and is, for example, 20% or more and 90% or less. Also, the position and shape of the transmissive region Tr in the pixel P can be appropriately set according to the application. In the specification of the present application, an area Iv that does not contribute to either reflective display or transmissive display within the pixel P may be referred to as an "ineffective area".

The TFT substrate 10 has a substrate 10 a , a backplane circuit BP, a first interlayer insulating layer 13 , a first reflective electrode 12 , a second interlayer insulating layer 14 and pixel electrodes 11 .

The substrate 10a supports the backplane circuit BP and the like. The substrate 10a is transparent and has insulating properties. The substrate 10a is, for example, a glass substrate or a plastic substrate.

The backplane circuit BP is provided on the substrate 10a. The backplane circuit BP is a circuit for driving a plurality of pixels P. As shown in FIG. Here, the backplane circuit has a memory circuit (eg, SRAM) connected to each of the plurality of pixels P. FIG. 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, for example, in Japanese Patent No. 5036864 (corresponding to US Pat. No. 8,692,758). The entire disclosures of US Pat. No. 5,036,864 and US Pat. No. 8,692,758 are incorporated herein by reference.

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

The first reflecting electrode 12 is provided on the first interlayer insulating layer 13 . The first reflecting electrode 12 is made of a highly reflective metal material. Here, a silver alloy is used as the metal material for forming the first reflecting electrode 12, but the material is not limited to this, and for example, aluminum or an aluminum alloy may be used.

The surface of the first reflective electrode 12 has an uneven shape reflecting the uneven surface structure of the first interlayer insulating layer 13 . That is, the first reflecting electrode 12 also has an uneven surface structure. The uneven surface structure of the first reflective electrode 12 is provided to diffusely reflect ambient light to achieve a display close to paper white. The uneven surface structure can be composed of, for example, a plurality of protrusions p randomly arranged such that 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 protrusion p is substantially circular or substantially polygonal. The area of the convex portion p that occupies the pixel P is, for example, about 20% to 40%. The height of the convex portion p is, for example, 1 μm or more and 5 μm or less.

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

A second interlayer insulating layer 14 is provided to cover the first reflecting electrode 12 . The second interlayer insulating layer 14 is a transparent insulating layer.

The pixel electrode 11 is provided for each of the plurality of pixels P. As shown in FIG. Also, the pixel electrode 11 is provided on the second interlayer insulating layer 14 . That is, the pixel electrode 11 is arranged on the first reflective electrode 12 with the second interlayer insulating layer (transparent insulating layer) 14 interposed therebetween. In other words, the first reflective electrode 12 is located on the side opposite to the liquid crystal layer 30 with respect to the pixel electrode 11 (that is, on the back side of the pixel electrode 11).

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 BP including a memory circuit. A part of the pixel electrode 11 is located in the transmissive region Tr, and another part of the pixel electrode 11 is located in the reflective region Rf.

The TFT substrate 10 further has a contact portion CP, a second reflective electrode 16 and a first alignment film 15 .

The contact part CP electrically connects the pixel electrode 11 and the backplane circuit BP through a first contact hole CH1 formed in the first interlayer insulating layer 13 and a second contact hole CH2 formed in the second interlayer insulating layer 14. connect to. In the illustrated example, the contact part CP is composed of a first contact electrode ce1, a second contact electrode ce2 and a third contact electrode ce3.

The first contact electrode ce1 is an electrode (or part of the wiring) exposed in the first contact hole CH1. The second contact electrode ce2 is formed on the first interlayer insulating layer 13 and inside the first contact hole CH1, and is connected to the first contact electrode ce1 inside the first contact hole CH1. A part of the second contact electrode ce2 is exposed in the second contact hole CH2. The third contact electrode ce3 is connected to the second contact electrode ce2 and the pixel electrode 11 inside the second contact hole CH2. In other words, the third contact electrode ce3 is interposed between the second contact electrode ce2 and the pixel electrode 11 . Here, the first contact electrode ce1 is made of a metal material and is opaque. Also, the second contact electrode ce2 is made of a transparent conductive material (that is, transparent). The third contact electrode ce3 is formed from the same metal film as the first reflective electrode 12 (that is, in the same layer as the first reflective electrode 12) and is opaque. In the illustrated example, the conductive layer 19 formed from the same transparent conductive film as the second contact electrode ce2 (that is, in the same layer as the second contact electrode ce2) is formed between the first reflective electrode 12 and the first interlayer insulating layer. 13, this conductive layer 19 may be omitted.

A second reflective electrode 16 is provided on the second interlayer insulating layer 14 . The second reflective electrode 16 is arranged so as to overlap the first contact hole CH1 when viewed from the normal direction of the display surface. The second reflective electrode 16 is formed in contact with the pixel electrode 11 and electrically connected to the pixel electrode 11 . In the illustrated example, the second reflective electrode 16 is formed on the pixel electrode 11, but is formed below the pixel electrode 11 (that is, between the second interlayer insulating layer 14 and the pixel electrode 11). may

The second reflective electrode 16 is made of a highly reflective metal material. Here, a silver alloy is used as the metal material for forming the second reflective electrode 16, but the material is not limited to this, and for example, aluminum or an aluminum alloy may be used.

The second interlayer insulating layer 14 has an uneven surface structure in a portion overlapping with the first contact hole CH1. Second interlayer insulating layer 14 having an uneven surface structure can be formed using a photosensitive resin, like first interlayer insulating layer 13 .

The pixel electrode 11 has an uneven shape reflecting the uneven surface structure of the second interlayer insulating layer 14 in a portion overlapping with the first contact hole CH1. That is, the pixel electrode 11 also has an uneven surface structure.

Also, the second reflective electrode 16 has an uneven shape reflecting the uneven surface structure of the pixel electrode 11 . That is, the second reflecting electrode 16 also has an uneven surface structure. The concave-convex surface structure of the second reflective electrode 16 is also provided to diffusely reflect ambient light to achieve a display close to paper white. The arrangement, shape, etc. of the projections forming the uneven surface structure of the second reflective electrode 16 may be the same as the arrangement, shape, etc. of the projections p of the first reflective electrode 16 .

The counter substrate 20 has a substrate 20 a , a color filter layer 22 , a counter electrode (common electrode) 21 and a second alignment film 25 . Although not shown here, the counter substrate 20 further has a plurality of columnar spacers.

The substrate 20a supports the color filter layer 22 and the like. The substrate 20a is transparent and has insulating properties. The substrate 20a is, for example, a glass substrate or a plastic substrate.

The color filter layer 22 typically includes a red color filter 22R provided in a region corresponding to the red pixels PR, a green color filter _22G provided in a region corresponding to the green pixels _PG , and a blue pixel P A blue color filter 22B provided in a region corresponding to _B is included. The red color filter 22R, green color filter 22G, and blue color filter 22B transmit red light, green light, and blue light, respectively. 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 so as to face the pixel electrode 11 and the first reflective electrode 12 . 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.

The columnar spacers define the thickness (cell gap) of the liquid crystal layer 30 . The columnar spacers can be made of photosensitive resin.

The liquid crystal layer 30 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 by, for example, 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 alignment treatment and defines the pretilt orientation. The liquid crystal molecules 31 of the liquid crystal layer 30 are vertically aligned when no voltage is applied to the liquid crystal layer 30 (see FIG. 2A), and are tilted and twisted when a predetermined voltage is applied to the liquid crystal layer 30 . Thus, the liquid crystal layer 30 is a vertically aligned liquid crystal layer.

The liquid crystal display device 100 further includes a pair of circularly polarizing plates 40A and 40B and an illumination device (backlight) (not shown). One of the pair of circularly polarizing plates 40A and 40B (first circularly polarizing plate) 40A is arranged on the back side of the TFT substrate 10, and the other (second circularly polarizing plate) 40B is arranged on the viewer side of the opposing substrate 20. are placed in The illumination device is arranged on the back side of the first circularly polarizing plate 40A.

The illustrated liquid crystal display device 100 has a configuration for performing gradation display with memory liquid crystal. Specifically, each pixel P of the liquid crystal display device 100 is divided into a plurality of sub-pixels Sp as shown in FIG. FIG. 1 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 on the upper side and the lower side in the drawing are electrically connected to one common memory circuit, and are arranged in the center of the drawing. One sub-pixel electrode 11a is electrically connected to another one memory circuit. That is, two memory circuits are provided for each pixel P. FIG.

Since the pixel P is divided as shown in FIG. 1, it is possible to perform 4-grayscale display by the area grayscale method, as shown in FIG. Specifically, as shown on the leftmost side of FIG. 3, by setting all the three sub-pixels Sp to a black display state, a black display can be performed as a whole pixel P. From the left side of FIG. As shown in the second figure, by setting two sub-pixels Sp in a black display state and one sub-pixel Sp in a white display state, a dark halftone display can be performed as a whole pixel P. FIG. In addition, as shown in the third from the left side of FIG. 3, by setting two sub-pixels Sp in a white display state and one sub-pixel Sp in a black display state, a bright halftone display is obtained as a whole pixel P. As shown on the rightmost side of FIG. 3, by bringing all three sub-pixels Sp into the white display state, the entire pixel P can perform white display.

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).

As described above, in the liquid crystal display device 100 of the present embodiment, the first reflective electrode 12 is arranged not only in the first region 12a located within the pixel P, but also in the second region 12b located between two adjacent pixels P. contains. Therefore, since the area between the pixels P can also contribute to the reflective display, the reflective aperture ratio (ratio occupied by the area contributing to the display in the reflective mode in the display area) is improved, and the reflectance is further improved. be able to. Therefore, brighter display can be performed in the reflective mode. Note that in a conventional general reflective liquid crystal display device, the pixel electrode is a reflective electrode (the reflective electrode functions as the pixel electrode), so the reflective electrode cannot be arranged between the pixels.

Further, the liquid crystal display device 100 of the present embodiment can solve the following problems of the conventional transflective liquid crystal display device.

As a semi-transmissive 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 oriented in a desired direction, resulting in a problem of low transmittance. In addition, a region between pixels includes an area in which alignment by an oblique electric field generated near the edge of the pixel electrode and alignment by rubbing treatment are not well matched, and the alignment of liquid crystal molecules is unstable. Since the region where the orientation between pixels is unstable is used for display in the transmission mode, display defects (such as afterimages) caused by the poor orientation occur in the display in the transmission mode.

In contrast, in the liquid crystal display device 100 of the present embodiment, the pixel electrodes 11 exist within the transmissive region Tr, so liquid crystal molecules within the transmissive region Tr can be sufficiently aligned in a desired direction. Therefore, transmittance is improved. In addition, since the region where the orientation is stable is used for display in the transmission mode, it is possible to improve display defects caused by poor orientation in the display in the transmission mode.

Further, in the liquid crystal display device 100 of the present embodiment, the second reflective electrode 16 having an uneven surface structure is formed on the second interlayer insulating layer 14 so as to overlap the first contact hole CH1 when viewed in the direction normal to the display surface. Therefore, the region where the first contact hole CH1 exists can sufficiently contribute to the reflective display (that is, function as the reflective region Rf), and a brighter display can be realized. This point will be described below while comparing the liquid crystal display device 900 and the liquid crystal display device 100 of the comparative example shown in FIGS. 4A and 4B. 4A and 4B are cross-sectional views schematically showing a liquid crystal display device 900 of a comparative example, showing a cross-sectional structure of the liquid crystal display device 100 corresponding to the cross-sectional structure shown in FIGS. 2A and 2B.

The liquid crystal display device 900 of the comparative example differs from the liquid crystal display device 100 in that it does not have the second reflective electrode 16, as shown in FIG. 4B. Further, in the liquid crystal display device 900 of the comparative example, the pixel electrode 11 and the second interlayer insulating layer 14 do not have the uneven surface structure in the portion overlapping the first contact hole CH1.

In the liquid crystal display device 900 of the comparative example, the region where the first contact hole CH1 exists does not contribute to transmissive display because the light from the illumination device is blocked by the first contact electrode ce1. In addition, since no reflective electrode is provided in the region where the first contact hole CH1 exists, this region does not contribute to reflective display. In addition, the region where the second contact hole CH2 exists does not contribute to transmissive display because the third contact electrode ce3 blocks the light from the illumination device. Furthermore, although the third contact electrode ce3 formed of the same metal film as the first reflective electrode 12 is positioned in the region where the second contact hole CH2 exists, the tapered shape of the second contact hole CH2 is different from that of the second contact hole CH2. Since it is steeper than the uneven surface structure of the first reflective electrode 12, the third contact electrode ce3 does not contribute to diffuse reflection, and this region does not contribute to reflective display. Thus, in the liquid crystal display device 900 of the comparative example, the region where the first contact hole CH1 exists and the region where the second contact hole CH2 exists become the invalid region Iv.

In contrast, in the liquid crystal display device 100 of the present embodiment, the second reflective electrode 16 having an uneven surface structure is provided on the second interlayer insulating layer 14 so as to overlap the first contact hole CH1. Since the region where the contact hole CH1 exists can sufficiently contribute to the reflective display, the area of the ineffective region Iv can be reduced compared to the liquid crystal display device 900 of the comparative example, and the brightness of the display can be improved. can be made

It should be noted that the liquid crystal display device 100 preferably employs one of the following driving methods.
Method (A): Voltages of the same polarity are applied to the liquid crystal layers 30 of arbitrary two pixels P adjacent to each other along the row direction among the plurality of pixels P. This driving method is called row-line inversion driving (H-line inversion driving), and includes a mode in which the polarity is inverted for every plurality of rows (2H-line inversion driving, etc.).
Method (B): Voltages of the same polarity are applied to the liquid crystal layers 30 of arbitrary two pixels P adjacent to each other along the column direction among the plurality of pixels P. This is a driving method called column line inversion driving (V line inversion driving), and includes a mode in which the polarity is inverted for every plurality of columns (2V line inversion driving, 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. FIG. This driving method is called field inversion driving (frame inversion driving).

The effect of improving the reflectance (brightening the display) is increased by performing the drive by any one of the methods (A), (B), and (C). 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 arbitrary two pixels adjacent to each other among a plurality of pixels. That is, the polarity of the applied voltage is inverted pixel by pixel along the row direction, and the polarity of the applied voltage is inverted pixel by 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 the brightness due to the oblique electric field generated between the pixels. may not be oriented in the same way.

On the other hand, when driving is performed by any one of the methods (A), (B), and (C), the polarities of the applied voltages are different between adjacent pixels P along at least one of the row direction and the column direction. Since they are the same (not inverted), the liquid crystal molecules 31 located between the pixels P to which voltages of the same polarity are applied can be oriented so as to contribute to brightness. Therefore, the effect of improving the reflectance is enhanced. From the viewpoint of further improving the reflectance, method (C) is preferable to methods (A) and (B). In other words, field inversion driving is preferable, in which voltages of the same polarity are applied to the liquid crystal layers 30 of all the pixels P of the plurality of pixels P. FIG.

[Verification result of brightness improvement effect]
The liquid crystal display device 100 of this embodiment was produced (Example 1), and the result of verifying the effect of improving the brightness 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 rubbed. 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 becomes 70° when white voltage is applied. The driving method is field inversion driving (method (C)).

A liquid crystal display device 900 of a comparative example was also produced in the same manner as in Example 1, and was compared with Example 1. FIG. Table 1 shows the ratio of the transmissive region Tr within the display region (transmissive aperture ratio), the ratio of the reflective region Rf within the display region (reflective aperture ratio), and the reflectance during white display for Example 1 and the comparative example. (white reflectance), reflectance at black display (black reflectance), and contrast ratio.

As shown in Table 1, Example 1 and Comparative Example have the same transmission aperture ratio. On the other hand, in Example 1, the reflective aperture ratio is about 1.05 times higher than in the comparative example. Therefore, in Example 1, the white reflectance is about 1.05 times higher than in Comparative Example. In Example 1, the black reflectance is also higher than in the comparative example due to the improvement in the reflective aperture ratio. The increase remains about 1.03 times. Therefore, in Example 1, the contrast ratio is improved by about 1.02 times as compared to the comparative example.

Thus, it was confirmed that the liquid crystal display device 100 according to the embodiment of the present invention improved the brightness of the display.

In the liquid crystal display device 100 of the present embodiment, the area between the pixels P contributes to the display in the reflective mode. It is preferred not to have a black matrix. For the same reason, it is preferable that the red color filter 22R, the green color filter 22G and the blue color filter 22B do not overlap each other when viewed from the normal direction of the display surface.

[Potential of the first reflecting electrode]
The potential applied to the first reflecting electrode 12 is not particularly limited. For example, the same potential as that of the counter electrode 21 may be applied to the first reflecting electrode 12 . A potential different from that of the counter electrode 21 may be applied to the first reflective electrode 12. For example, the same potential as the potential applied to the pixel electrode 11 when displaying the highest gradation (hereinafter also referred to as "white display potential") may be applied. may be given. By applying a potential different from that of the counter electrode 21 to the first reflective electrode 12, a sufficiently high voltage can be applied to the liquid crystal layer 30 between the pixels P, so that the space between the pixels P is brightened during white display. be able to. Therefore, the effect of improving the reflectance is further enhanced.

Further, the first reflecting electrode 12 may be in an electrically floating state (floating state), or may be supplied with a ground potential. By putting the first reflective electrode 12 in a floating state or applying a ground potential to the first reflective electrode 12, the voltage applied between the first reflective electrode 12 and the pixel electrode 11 in the white display state and the black display state is changed. have the same time average. Therefore, since the occurrence of image sticking is suppressed, low-frequency driving can be preferably performed.

Table 2 shows examples of potentials applied to the pixel electrode 11, the first reflective electrode 12, the second reflective electrode 16, and the counter electrode 21.

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

Also, although the VA-HAN mode in which only one of the vertical alignment films defines the pretilt orientation has been exemplified, the VA-TN mode in which both of the vertical alignment films regulate the pretilt orientations may also be used.

Further, although the configuration in which the cell gap dt in the transmissive region Tr and the cell gap dr in the reflective region Rf are the same has been exemplified, the cell gap dt in the transmissive region Tr is larger than the cell gap dr in the reflective region Rf (that is, dt> dr) configuration may be employed.

The light used for transmissive mode display passes through the liquid crystal layer 30 only once, while the light used for reflective mode display passes through the liquid crystal layer 30 twice. Therefore, when the cell gap dt of the transmissive region Tr is larger than the cell gap dr of the reflective region Rf, the retardation of the liquid crystal layer 30 can be made close to the light used for display in the transmissive mode and the light used for display in the reflective mode. Thus, favorable voltage-luminance characteristics (achieving brighter display) can be obtained for both the transmissive region Tr and the reflective region Rf.

From the viewpoint of 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 of dt=2dr. is preferred.

Also, although the configuration in which each pixel P is divided into a plurality of sub-pixels Sp is illustrated, each pixel P may not be divided into a plurality of sub-pixels Sp.

(Embodiment 2)
A liquid crystal display device 200 according to the present embodiment will be described with reference to FIGS. 5, 6A and 6B. FIG. 5 is a plan view schematically showing the liquid crystal display device 200, showing regions corresponding to three pixels P of the liquid crystal display device 200. As shown in FIG. 6A and 6B are cross-sectional views schematically showing the liquid crystal display device 200, showing cross-sectional structures along lines 6A-6A' and 6B-6B' in FIG. 5, respectively. In the following, the liquid crystal display device 200 of the present embodiment will be described with a focus on the differences from the liquid crystal display device 100 of the first embodiment.

The first reflective electrode 12 and the second reflective electrode 16 of the liquid crystal display device 200 are formed on the first interlayer insulating layer 13 and the second interlayer insulating layer 14 that do not have unevenness (that is, are flat), respectively. Therefore, the first reflecting electrode 12 and the second reflecting electrode 16 do not have an uneven surface structure, and function as specular reflection layers.

The liquid crystal display device 200 further includes a light scattering layer 50 arranged closer to the viewer than the liquid crystal layer 30 is. The light scattering layer 50 is, for example, an anisotropic light scattering film. In the illustrated example, the light scattering layer 50 is arranged between the substrate 20a and the second circularly polarizing plate 40B. In this embodiment, light is scattered by the light scattering layer 50, so that a display close to paper white can be realized.

In the liquid crystal display device 200 of the present embodiment, the combination of the second reflective electrode 16 and the light scattering layer 50 allows the region where the first contact hole CH1 exists to sufficiently contribute to the reflective display, resulting in a brighter display. can be realized.

In addition, in the liquid crystal display device 200 of the present embodiment, the third contact electrode ce3 provided on the first interlayer insulating layer 13 so as to overlap the second contact hole CH2 when viewed in the direction normal to the display surface and the light scattering electrode ce3 In combination with the layer 50, the region where the second contact hole CH2 exists can also be made to contribute sufficiently to the reflective display, so the region contributing to the reflective display is further widened (for example, the invalid region Iv is substantially eliminated). be able to. At this time, the third contact electrode ce3 functions as a third reflective electrode for performing reflective display. The third contact electrode (third reflecting electrode) ce3 also does not have an uneven surface structure.

In the above description, a semi-transmissive (both transmissive and reflective) liquid crystal display device is exemplified. A reflective liquid crystal display device may also be used. In the reflective liquid crystal display device as well, the display brightness can be improved by providing a further reflective electrode similar to the second reflective electrode 16 of the liquid crystal display devices 100 and 200 described above.

(Embodiment 3)
A liquid crystal display device 300 according to the present embodiment will be described with reference to FIGS. 7, 8A and 8B. The liquid crystal display device 300 of this embodiment is a reflective liquid crystal display device. FIG. 7 is a plan view schematically showing the liquid crystal display device 300, showing regions corresponding to three pixels P of the liquid crystal display device 300. As shown in FIG. 8A and 8B are cross-sectional views schematically showing the liquid crystal display device 300, showing cross-sectional structures along lines 8A-8A' and 8B-8B' in FIG. 7, respectively.

The liquid crystal display device 300 has a plurality of pixels P, as shown in FIG. A 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 red pixels P _R that display red, green pixels P _G that display green, and blue pixels P _B that display blue.

8A and 8B, the liquid crystal display device 300 includes a TFT substrate (first substrate) 10, a counter substrate (second substrate) 20 facing the TFT substrate 10, and a TFT substrate 10 and the counter substrate. 20 and a vertical alignment type liquid crystal layer 30 provided between them. Each pixel P includes a reflective area Rf that displays in a reflective mode.

The TFT substrate 10 has a substrate 10 a , a backplane circuit BP, a first interlayer insulating layer 13 , a first reflective electrode 12 , a second interlayer insulating layer 14 and pixel electrodes 11 .

The substrate 10a supports the backplane circuit BP and the like. The substrate 10a is transparent and has insulating properties. The substrate 10a is, for example, a glass substrate or a plastic substrate.

The backplane circuit BP is provided on the substrate 10a. The backplane circuit BP is a circuit for driving a plurality of pixels P. As shown in FIG. Here, the backplane circuit has a memory circuit connected to each of the plurality of pixels P. FIG.

The first interlayer insulating layer 13 is provided so as to cover the backplane circuit BP. The surface of first interlayer insulating layer 13 has an uneven shape. That is, first interlayer insulating layer 13 has an uneven surface structure.

The first reflecting electrode 12 is provided on the first interlayer insulating layer 13 . The first reflecting electrode 12 is made of a highly reflective metal material. Here, a silver alloy is used as the metal material for forming the first reflecting electrode 12, but the material is not limited to this, and for example, aluminum or an aluminum alloy may be used. The surface of the first reflective electrode 12 has an uneven shape reflecting the uneven surface structure of the first interlayer insulating layer 13 . That is, the first reflecting electrode 12 also has an uneven surface structure.

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

A second interlayer insulating layer 14 is provided to cover the first reflecting electrode 12 . The second interlayer insulating layer 14 is a transparent insulating layer.

The pixel electrode 11 is provided for each of the plurality of pixels P. As shown in FIG. Also, the pixel electrode 11 is provided on the second interlayer insulating layer 14 . That is, the pixel electrode 11 is arranged on the first reflective electrode 12 with the second interlayer insulating layer (transparent insulating layer) 14 interposed therebetween. In other words, the first reflective electrode 12 is located on the side opposite to the liquid crystal layer 30 with respect to the pixel electrode 11 (that is, on the back side of the pixel electrode 11).

The pixel electrode 11 is made of a transparent conductive material. As the transparent conductive material, for example, indium tin oxide, indium zinc oxide, or a mixture thereof can be used. The pixel electrode 11 is electrically connected to a backplane circuit BP including a memory circuit.

The TFT substrate 10 further has a contact portion CP, a third interlayer insulating layer 17 , a second reflective electrode 18 and a first alignment film 15 .

The contact part CP electrically connects the pixel electrode 11 and the backplane circuit BP through a first contact hole CH1 formed in the first interlayer insulating layer 13 and a second contact hole CH2 formed in the second interlayer insulating layer 14. connect to. In the illustrated example, the contact part CP is composed of a first contact electrode ce1, a second contact electrode ce2 and a third contact electrode ce3.

The first contact electrode ce1 is an electrode (or part of the wiring) exposed in the first contact hole CH1. The second contact electrode ce2 is formed on the first interlayer insulating layer 13 and inside the first contact hole CH1, and is connected to the first contact electrode ce1 inside the first contact hole CH1. A part of the second contact electrode ce2 is exposed in the second contact hole CH2. The third contact electrode ce3 is connected to the second contact electrode ce2 and the pixel electrode 11 inside the second contact hole CH2. In other words, the third contact electrode ce3 is interposed between the second contact electrode ce2 and the pixel electrode 11 . Here, the first contact electrode ce1 is made of a metal material and is opaque. Also, the second contact electrode ce2 is made of a transparent conductive material (that is, transparent). The third contact electrode ce3 is made of the same metal film as the first reflective electrode 12 (that is, in the same layer as the first reflective electrode 12) and is opaque. In the illustrated example, the conductive layer 19 formed from the same transparent conductive film as the second contact electrode ce2 (that is, in the same layer as the second contact electrode ce2) is formed between the first reflective electrode 12 and the first interlayer insulating layer. 13, this conductive layer 19 may be omitted.

The third interlayer insulating layer 17 is provided inside the second contact hole CH2. In the illustrated example, the second contact hole CH2 and the third interlayer insulating layer 17 overlap the first contact hole CH1 when viewed from the direction normal to the display surface. It is also located inside the first contact hole CH1.

A second reflective electrode 18 is provided on the third interlayer insulating layer 17 . The second reflective electrode 18 is arranged so as to overlap at least the second contact hole CH2 when viewed in the direction normal to the display surface. In the illustrated example, the second reflecting electrode 18 overlaps not only the second contact hole CH2 but also the first contact hole CH1. The second reflective electrode 18 is in contact with the pixel electrode 11 and is electrically connected to the pixel electrode 11 . In the illustrated example, a conductive layer 19' made of a transparent conductive material is interposed between the second reflecting electrode 18 and the third interlayer insulating layer 17. This conductive layer 19' May be omitted. When the conductive layer 19' is provided, the second reflective electrode 18 may be electrically connected to the pixel electrode 11 via the conductive layer 19'.

The second reflecting electrode 18 is made of a highly reflective metal material. Here, a silver alloy is used as the metal material for forming the second reflective electrode 18, but the material is not limited to this, and for example, aluminum or an aluminum alloy may be used.

Third interlayer insulating layer 17 has an uneven surface structure. Third interlayer insulating layer 17 having an uneven surface structure can be formed using a photosensitive resin, like first interlayer insulating layer 13 .

The second reflective electrode 18 has an uneven shape reflecting the uneven surface structure of the third interlayer insulating layer 17 . That is, the second reflecting electrode 18 also has an uneven surface structure.

The counter substrate 20 has a substrate 20 a , a color filter layer 22 , a counter electrode (common electrode) 21 and a second alignment film 25 . Although not shown here, the counter substrate 20 further has a plurality of columnar spacers.

The substrate 20a supports the color filter layer 22 and the like. The substrate 20a is transparent and has insulating properties. The substrate 20a is, for example, a glass substrate or a plastic substrate.

The color filter layer 22 typically includes a red color filter 22R provided in a region corresponding to the red pixels PR, a green color filter _22G provided in a region corresponding to the green pixels _PG , and a blue pixel P A blue color filter 22B provided in a region corresponding to _B is included. The red color filter 22R, green color filter 22G, and blue color filter 22B transmit red light, green light, and blue light, respectively. 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 so as to face the pixel electrode 11 and the like. 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.

The columnar spacers define the thickness (cell gap) of the liquid crystal layer 30 . The columnar spacers can be made of photosensitive resin.

The liquid crystal layer 30 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 by, for example, 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 alignment treatment and defines the 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 tilted and twisted when a predetermined voltage is applied to the liquid crystal layer 30. FIG. Thus, the liquid crystal layer 30 is a vertically aligned liquid crystal layer.

The liquid crystal display device 300 further includes a pair of circularly polarizing plates 40A and 40B and an illumination device (backlight) (not shown). One of the pair of circularly polarizing plates 40A and 40B (first circularly polarizing plate) 40A is arranged on the back side of the TFT substrate 10, and the other (second circularly polarizing plate) 40B is arranged on the viewer side of the opposing substrate 20. are placed in The illumination device is arranged on the back side of the first circularly polarizing plate 40A.

The illustrated liquid crystal display device 300 has a configuration for performing gradation display with memory liquid crystal. Specifically, each pixel P of the liquid crystal display device 300 is divided into a plurality of sub-pixels Sp as shown in FIG. 7, and the pixel electrode 11 is divided into a plurality of sub-pixel electrodes 11a. As with the liquid crystal display device 100 of the first embodiment, the liquid crystal display device 300 can perform gradation display by the area gradation method.

As described above, in the liquid crystal display device 300 of the present embodiment, the first reflective electrode 12 is arranged not only in the first region 12a located within the pixel P, but also in the second region 12b located between two adjacent pixels P. contains. Therefore, since the area between the pixels P can also contribute to the reflective display, the reflective aperture ratio (ratio occupied by the area contributing to the display in the reflective mode in the display area) is improved, and the reflectance is further improved. be able to. Therefore, brighter display can be performed in the reflective mode.

Furthermore, in the liquid crystal display device 300 of the present embodiment, the second reflective electrode 18 having the uneven surface structure is arranged so as to overlap the first contact hole CH1 and the second contact hole CH2 when viewed from the direction normal to the display surface. Since it is provided on the third interlayer insulating layer 17, the region where the first contact hole CH1 and the second contact hole CH2 are present can sufficiently contribute to the reflective display (that is, function as the reflective region Rf). , a brighter display can be achieved. In the liquid crystal display device 100 of Embodiment 1, the region where the second contact hole CH2 exists is the invalid region Iv, but in the liquid crystal display device 300 of this embodiment, the region where the second contact hole CH2 exists. can also function as the reflective area Rf, the invalid area Iv in the pixel P can be substantially eliminated.

In the liquid crystal display device 300 as well, it is preferable to use any one of the driving methods (A), (B) and (C) already described. The effect of improving the reflectance (brightening the display) is increased by performing the drive by any one of the methods (A), (B), and (C).

[Verification result of brightness improvement effect]
The liquid crystal display device 300 of this embodiment was manufactured (Example 2), and the result of verifying the effect of improving the brightness will be described. The screen size of the manufactured liquid crystal display device 300 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 rubbed. 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 becomes 70° when white voltage is applied. The driving method is field inversion driving (method (C)).

Example 3 was prepared by modifying Example 1 to a reflective type (that is, in which the transmissive region Tr of Example 1 was replaced with a reflective region Rf, and compared with Example 2. Table 3 shows Example 2. and 3, the transmission aperture ratio, reflection aperture ratio, white reflectance, black reflectance and contrast ratio are shown.

As shown in Table 3, in Example 2, the reflective aperture ratio is higher than that in Example 3 by about 1.04 times. Therefore, in Example 2, the white reflectance is about 1.04 times higher than in Example 3. In Example 2, the black reflectance is also higher than in Example 3 due to the improvement in the reflective aperture ratio. It remains about 1.03 times. Therefore, in Example 2, the contrast ratio is improved by about 1.02 times as compared with Example 3.

Thus, it was confirmed that the brightness of the display was further improved by adopting the configuration of the liquid crystal display device 300 of the present embodiment.

[Potential of the first reflecting electrode]
The potential applied to the first reflecting electrode 12 is not particularly limited. For example, the same potential as that of the counter electrode 21 may be applied to the first reflecting electrode 12 . A potential different from that of the counter electrode 21 may be applied to the first reflective electrode 12. For example, the same potential as the white display potential may be applied. By applying a potential different from that of the counter electrode 21 to the first reflective electrode 12, a sufficiently high voltage can be applied to the liquid crystal layer 30 between the pixels P, so that the space between the pixels P is brightened during white display. be able to. Therefore, the effect of improving the reflectance is further enhanced.

Also, the first reflecting electrode 12 may be in a floating state, or may be supplied with a ground potential. By putting the first reflective electrode 12 in a floating state or applying a ground potential to the first reflective electrode 12, the voltage applied between the first reflective electrode 12 and the pixel electrode 11 in the white display state and the black display state is changed. have the same time average. Therefore, since the occurrence of image sticking is suppressed, low-frequency driving can be preferably performed.

Table 4 shows examples of potentials applied to the pixel electrode 11, the first reflective electrode 12, the second reflective electrode 18, and the counter electrode 21.

(Embodiment 4)
A liquid crystal display device 400 according to the present embodiment will be described with reference to FIG. FIG. 9 is a plan view schematically showing the liquid crystal display device 400, showing regions corresponding to three pixels P of the liquid crystal display device 400. FIG. Below, the liquid crystal display device 400 of the present embodiment will be described with a focus on the differences from the liquid crystal display device 300 of the third embodiment.

The liquid crystal display device 400 is different from the liquid crystal display device 300 of the third embodiment in that it is a transflective (transmissive/reflective) liquid crystal display device. That is, each pixel P of the liquid crystal display device 400 includes a transmissive region Tr for displaying in the transmissive mode, as shown in FIG.

The transmission region Tr does not overlap the contact portion CP. Also, the transmissive region Tr is arranged so as not to be shaded by the backplane circuit BP (that is, not to overlap the opaque electrodes or wiring of the backplane circuit BP).

Although not shown here, in the liquid crystal display device 400 of the present embodiment, as in the liquid crystal display device 300 of the third embodiment, the second reflective electrode 18 having an uneven surface structure is is provided on the third interlayer insulating layer 17 so as to overlap with the first contact hole CH1 and the second contact hole CH2, the region where the first contact hole CH1 and the second contact hole CH2 are present is reflectively displayed. (that is, function as a reflective region Rf), and the invalid region Iv in the pixel P can be substantially eliminated to realize a brighter display.

A liquid crystal display device 400 of this embodiment was produced (Example 4), and the effect of improving brightness was verified.
Table 5 shows the transmission aperture ratio, reflection aperture ratio, white reflectance, black reflectance and contrast ratio for Examples 4 and 1.

As shown in Table 5, in Example 4, the reflective aperture ratio is higher than that in Example 1 by about 1.05 times. Therefore, in Example 1, the white reflectance is about 1.05 times higher than in Comparative Example. In Example 4, the black reflectance is also higher than in Example 1 due to the improvement in the reflective aperture ratio. It remains about 1.03 times. Therefore, in the fourth embodiment, the contrast ratio is improved by about 1.03 times as compared with the first embodiment.

(Embodiment 5)
A liquid crystal display device 500 according to the present embodiment will be described with reference to FIGS. 10, 11A and 11B. FIG. 10 is a plan view schematically showing the liquid crystal display device 500, showing regions corresponding to three pixels P of the liquid crystal display device 500. As shown in FIG. 11A and 11B are cross-sectional views schematically showing the liquid crystal display device 500, showing cross-sectional structures along lines 11A-11A' and 11B-11B' in FIG. 10, respectively. In the following, the liquid crystal display device 500 of this embodiment will be described with a focus on the differences from the liquid crystal display device 300 of the third embodiment.

The first reflective electrode 12 and the second reflective electrode 18 of the liquid crystal display device 500 are formed on the first interlayer insulating layer 13 and the third interlayer insulating layer 14 that do not have unevenness (that is, are flat), respectively. Therefore, the first reflective electrode 12 and the second reflective electrode 18 do not have an uneven surface structure, and function as specular reflection layers.

The liquid crystal display device 500 further includes a light scattering layer 50 arranged closer to the viewer than the liquid crystal layer 30 is. The light scattering layer 50 is, for example, an anisotropic light scattering film. In the illustrated example, the light scattering layer 50 is arranged between the substrate 20a and the second circularly polarizing plate 40B. In this embodiment, light is scattered by the light scattering layer 50, so that a display close to paper white can be realized.

In the liquid crystal display device 500 of the present embodiment, the combination of the second reflective electrode 18 and the light scattering layer 50 allows the region where the first contact hole CH1 and the second contact hole CH2 are present to sufficiently contribute to reflective display. Therefore, a brighter display can be realized.

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.

REFERENCE SIGNS LIST 10 TFT substrate 11 pixel electrode 11a sub-pixel electrode 12 first reflective electrode 12a first region 12b second region 13 first interlayer insulating layer 14 second interlayer insulating layer 15 first alignment film 16, 18 second reflective electrode 17 third third Interlayer insulating layer 20 Counter substrate 21 Counter electrode 22 Color filter layer 25 Second alignment film 30 Liquid crystal layer 31 Liquid crystal molecules 40A, 40B Circularly polarizing plate 50 Light scattering layer 100, 200, 300, 400, 500 Liquid crystal display device P Pixel Sp Sub pixel Rf reflective region Tr transmissive region CP contact portion ce1 first contact electrode ce2 second contact electrode ce3 third contact electrode

Claims (19)

a first substrate;
a second substrate facing the first substrate;
a vertically aligned liquid crystal layer provided between the first substrate and the second substrate;
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 displays in a reflective mode;
The first substrate is
a substrate;
a backplane circuit provided on the substrate and driving the plurality of pixels;
a first interlayer insulating layer provided to cover the backplane circuit;
A first reflective electrode provided on the first interlayer insulating layer, the first region positioned within each of the plurality of pixels, and arbitrary two pixels adjacent to each other among the plurality of pixels. a first reflective electrode including a second region positioned therebetween;
a second interlayer insulating layer provided to cover the first reflective electrode;
a pixel electrode formed of a transparent conductive material and provided on the second interlayer insulating layer in each of the plurality of pixels;
has
the pixel electrode is electrically connected to the backplane circuit through a first contact hole formed in the first interlayer insulating layer and a second contact hole formed in the second interlayer insulating layer;
The liquid crystal display device, wherein the first substrate further includes a second reflective electrode provided on the second interlayer insulating layer so as to overlap the first contact hole when viewed from the direction normal to the display surface. 2. The liquid crystal display device according to claim 1, wherein said first reflective electrode has an uneven surface structure in each of said first region and said second region. 3. The liquid crystal display device of claim 2, wherein the second reflective electrode has an uneven surface structure. 2. The liquid crystal display device according to claim 1, further comprising a light scattering layer arranged closer to the viewer than said liquid crystal layer. 5. The liquid crystal display device according to claim 4, wherein said first reflective electrode and said second reflective electrode do not have an uneven surface structure. the first substrate further includes a third reflective electrode provided on the first interlayer insulating layer so as to overlap the second contact hole when viewed from the direction normal to the display surface;
6. The liquid crystal display device according to claim 5, wherein said third reflective electrode does not have an uneven surface structure. 7. The liquid crystal display device according to claim 1, wherein said second reflective electrode is electrically connected to said pixel electrode. each of the plurality of pixels further includes a transmissive region for displaying in a transmissive mode;
7. The liquid crystal display device according to any one of claims 1 to 6, wherein a portion of said pixel electrode is located within said transmissive region. 7. The liquid crystal display device according to any one of claims 1 to 6, wherein said backplane circuit includes a memory circuit connected to each of said plurality of pixels. a first substrate;
a second substrate facing the first substrate;
a vertically aligned liquid crystal layer provided between the first substrate and the second substrate;
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 displays in a reflective mode;
The first substrate is
a substrate;
a backplane circuit provided on the substrate and driving the plurality of pixels;
a first interlayer insulating layer provided to cover the backplane circuit;
A first reflective electrode provided on the first interlayer insulating layer, the first region positioned within each of the plurality of pixels, and arbitrary two pixels adjacent to each other among the plurality of pixels. a first reflective electrode including a second region positioned therebetween;
a second interlayer insulating layer provided to cover the first reflective electrode;
a pixel electrode formed of a transparent conductive material and provided on the second interlayer insulating layer in each of the plurality of pixels;
has
the pixel electrode is electrically connected to the backplane circuit through a first contact hole formed in the first interlayer insulating layer and a second contact hole formed in the second interlayer insulating layer;
The first substrate is
a third interlayer insulating layer provided in the second contact hole;
a second reflective electrode provided on the third interlayer insulating layer so as to overlap at least the second contact hole when viewed from the direction normal to the display surface;
A liquid crystal display device further comprising: the second contact hole and the third interlayer insulating layer overlap the first contact hole when viewed from the direction normal to the display surface;
11. The liquid crystal display device according to claim 10, wherein said second reflective electrode also overlaps said first contact hole when viewed from the direction normal to the display surface. 12. The liquid crystal display device according to claim 10, wherein said first reflective electrode has an uneven surface structure in each of said first region and said second region. 13. The liquid crystal display of claim 12, wherein the second reflective electrode has an uneven surface structure. 12. The liquid crystal display device according to claim 10, further comprising a light scattering layer arranged closer to the viewer than said liquid crystal layer. 15. The liquid crystal display device according to claim 14, wherein said first reflective electrode and said second reflective electrode each do not have an uneven surface structure. 12. The liquid crystal display device according to claim 10, wherein said second reflective electrode is electrically connected to said pixel electrode. 12. The liquid crystal display device according to claim 10, wherein each of said plurality of pixels further includes a transmissive region displaying in a transmissive mode. 18. The liquid crystal display of claim 17, wherein said transmissive areas are unshielded by said backplane circuitry. 12. The liquid crystal display device according to claim 10, wherein said backplane circuit includes a memory circuit connected to each of said plurality of pixels.

Images