Reflective display panel

Abstract

The invention provides a reflective display panel suitable for reflecting external light beams. The reflective display panel comprises a pixel array substrate, a light-transmitting substrate, a pixel structure and a liquid crystal layer. The pixel structure comprises a first pixel electrode and an opposite electrode which are overlapped. The liquid crystal layer is arranged between the first pixel electrode and the opposite electrode, and the phase retardation of the liquid crystal layer ranges from 187 nm to 240 nm. The light beam has a first color after passing through the liquid crystal layer to which the first voltage is applied and exiting the reflective display panel. The light beam has a second color after passing through the liquid crystal layer to which the second voltage is applied and exiting the reflective display panel. The first voltage is different from the second voltage. The chromaticity coordinate (x1, y1) of the first color in the CIE1931 color space is within a chromaticity coordinate range. The chromaticity coordinate (x2, y2) of the second color in the CIE1931 color space is outside the chromaticity coordinate range.

Description

Technical Field

[0001] The present invention relates to a display panel, and in particular to a reflective display panel. Background Art

[0002] Generally, liquid crystal display panels can be divided into three categories: transmissive, reflective, and transflective. The basis for classification is the difference in the illumination source used and the configuration of the pixel array substrate. Among them, reflective liquid crystal display panels mainly use natural light or ambient light as the light source. Since it can be displayed without backlighting, it has good energy-saving characteristics. Therefore, it is often used in outdoor or well-lit places, such as billboards, electronic labels, sports watches, etc. Most of these display applications use a light background color (such as white) to highlight the advertisements or promotional information to be displayed.

[0003] In order to meet the needs of color display, a color resist layer can be added to a reflective liquid crystal display panel to achieve the desired display color. However, the setting of the color resist layer will sacrifice the overall reflectivity of the display pixel. Therefore, how to balance the needs of color display and reflectivity is still one of the important issues in the development of reflective liquid crystal display panels. Summary of the invention

[0004] The present invention is directed to a reflective display panel, which has better chromaticity and reflectivity of white screen.

[0005] According to an embodiment of the present invention, a reflective display panel is suitable for reflecting a light beam from the outside. The reflective display panel includes a pixel array substrate, a light-transmitting substrate, a pixel structure and a liquid crystal layer. The light-transmitting substrate and the pixel array substrate are arranged opposite to each other. The pixel structure includes a first pixel electrode and an opposite electrode. The first pixel electrode is arranged on the pixel array substrate. The opposite electrode is arranged on the light-transmitting substrate and overlaps the first pixel electrode. The liquid crystal layer is arranged between the first pixel electrode and the opposite electrode. The phase delay of the liquid crystal layer is in the range of 187nm to 240nm. The first pixel electrode, the opposite electrode and the liquid crystal layer are located on the transmission path of the light beam. When the first pixel electrode and the opposite electrode are applied with a first voltage, the light beam passing through the liquid crystal layer and exiting the reflective display panel has a first color. When the first pixel electrode and the opposite electrode are applied with a second voltage, the light beam passing through the liquid crystal layer and exiting the reflective display panel has a second color. The second voltage is different from the first voltage. The chromaticity coordinates (x1, y1) of the first color in the CIE1931 color space are located in a chromaticity coordinate range. The chromaticity coordinates (x2, y2) of the second color in the CIE1931 color space are outside the chromaticity coordinate range.

[0006] In the reflective display panel according to the embodiment of the present invention, the thickness of the liquid crystal layer is in the range of 1.5 μm to 4 μm.

[0007] In the reflective display panel according to the embodiment of the present invention, the reflectivity of the reflective display panel to the light beam having the first color is greater than the reflectivity of the reflective display panel to the light beam having the second color.

[0008] In the reflective display panel according to the embodiment of the present invention, the chromaticity coordinates (x2, y2) of the second color in the CIE1931 color space are within the chromaticity coordinate range of (0.490±0.05, 0.460±0.05).

[0009] In the reflective display panel according to the embodiment of the present invention, the second voltage is greater than or equal to 0V and less than the first voltage.

[0010] In the reflective display panel according to the embodiment of the present invention, a chromaticity coordinate range is (0.300±0.05, 0.330±0.05).

[0011] In the reflective display panel according to the embodiment of the present invention, the first voltage is within the range of 1.5V to 2.5V.

[0012] In the reflective display panel according to the embodiment of the present invention, the first pixel electrode and the counter electrode are further adapted to be applied with a third voltage, so that the light beam passing through the liquid crystal layer cannot exit the reflective display panel. The third voltage is greater than or less than the first voltage and the second voltage.

[0013] In the reflective display panel according to an embodiment of the present invention, the reflective display panel further comprises a filter pattern. The pixel structure comprises a second pixel electrode. The filter pattern overlaps the second pixel electrode and does not overlap the first pixel electrode. The color of the filter pattern is different from the first color and the second color.

[0014] In the reflective display panel according to the embodiment of the present invention, the first pixel electrode and the second pixel electrode respectively have a first reflective surface and a second reflective surface. The second reflective surface overlaps the filter pattern. The percentage of the area of ​​the first reflective surface to the total area of ​​the first reflective surface and the second reflective surface is greater than 55%.

[0015] Based on the above, in a reflective display panel of an embodiment of the present invention, the liquid crystal layer has a relatively high phase retardation within a specific range. By applying different voltages to the liquid crystal layer, the light beams passing through the liquid crystal layer and exiting the reflective display panel have different colors. This can not only meet the requirements of multi-color display, but also effectively improve the reflectivity and chromaticity performance of the reflective display panel in specific colors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a front view schematic diagram of a reflective display panel according to a first embodiment of the present invention;

[0017] Figure 2 yes Figure 1 A cross-sectional schematic diagram of a reflective display panel;

[0018] Figure 3 yes Figure 2 A curve distribution diagram of reflectivity versus voltage of a reflective display panel;

[0019] Figure 4 is a front view schematic diagram of a reflective display panel according to a second embodiment of the present invention.

[0020] Description of Reference Numerals

[0021] 10, 10A: reflective display panel;

[0022] 100: pixel array substrate;

[0023] 200: light-transmitting substrate;

[0024] DL, DL1, DL2: data lines;

[0025] FP: filter pattern;

[0026] GL: scan line;

[0027] LB1, LB2, LB3: beam;

[0028] LC: liquid crystal molecules;

[0029] LCL: Liquid crystal layer;

[0030] OE: opposite electrode;

[0031] PA, PA1, PA2, PA3: pixel area;

[0032] PE, PE1, PE2: pixel electrodes;

[0033] POL: polarizing layer;

[0034] PX, PX-A: pixel structure;

[0035] RS1, RS2: reflective surfaces;

[0036] T, T1, T2: active components;

[0037] V1: first voltage;

[0038] V2: second voltage;

[0039] V3: third voltage;

[0040] X, Y, Z: direction. DETAILED DESCRIPTION

[0041] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0042] Figure 1 is a front view schematic diagram of a reflective display panel according to a first embodiment of the present invention. Figure 2 yes Figure 1 For the sake of clarity, Figure 1 Omitted Figure 2 2 , the counter electrode OE, the light-transmitting substrate 200, the polarizing layer POL and the liquid crystal layer LCL are shown.

[0043] Please refer to Figure 1 and Figure 2 In this embodiment, the reflective display panel 10 is suitable for reflecting light beams from the outside for display. That is, the reflective display panel 10 uses external ambient light as an illumination light source for display. The reflective display panel 10 includes a pixel array substrate 100, a light-transmitting substrate 200, a plurality of pixel structures PX and a liquid crystal layer LCL. The liquid crystal layer LCL is disposed between the pixel array substrate 100 and the light-transmitting substrate 200.

[0044] The pixel structure PX may include an active element T, a pixel electrode PE and an opposite electrode OE. The active element T and the pixel electrode PE are disposed on the pixel array substrate 100 and are electrically connected to each other. The opposite electrode OE is disposed on the light-transmitting substrate 200. The pixel electrode PE is disposed between the liquid crystal layer LCL and the pixel array substrate 100. The opposite electrode OE is disposed between the liquid crystal layer LCL and the light-transmitting substrate 200. That is, the liquid crystal layer LCL is disposed between the pixel electrode PE and the opposite electrode OE.

[0045] It is first explained that the phase retardation of the liquid crystal layer LCL is within the range of 187nm to 240nm. In the present embodiment, the thickness of the liquid crystal layer LCL is preferably within the range of 1.5μm to 4μm, but not limited thereto. In other words, in the present embodiment, the absolute difference between the extraordinary refractive index and the ordinary refractive index of the liquid crystal layer LCL is within the range of 0.067 to 0.070, but not limited thereto. The phase retardation of the liquid crystal layer LCL is the product of the thickness of the liquid crystal layer LCL and the above absolute difference.

[0046] In the present embodiment, the counter electrodes OE of different pixel structures PX can be connected to each other and form a common electrode distributed on the entire surface of the transparent substrate 200, but the present invention is not limited thereto. The counter electrode OE is, for example, a light-transmitting electrode, and the material of the light-transmitting electrode includes metal oxides, such as indium tin oxide, indium zinc oxide, aluminum tin oxide, aluminum zinc oxide, or other suitable oxides, or a stacked layer of at least two of the above. The pixel electrode PE is, for example, a reflective electrode, and the material of the reflective electrode includes metal, alloy, nitride of metal material, oxide of metal material, oxynitride of metal material, or other suitable materials, or a stacked layer of metal material and other conductive materials.

[0047] It is also noted that, although not shown in the drawings, an alignment layer may be provided between the liquid crystal layer LCL and the pixel electrode PE and between the liquid crystal layer LCL and the counter electrode OE to define the arrangement direction of the plurality of liquid crystal molecules LC in the liquid crystal layer LCL when no voltage is applied.

[0048] In this embodiment, a plurality of scan lines GL and a plurality of data lines DL are further disposed on the pixel array substrate 100. For example, the data lines DL may be arranged along direction X and extend in direction Y, and the scan lines GL may be arranged along direction Y and extend in direction X, wherein direction X may be optionally perpendicular to direction Y. That is, the scan lines GL may be perpendicular to the data lines DL and define a plurality of pixel areas PA. The aforementioned plurality of pixel structures PX are respectively disposed in the pixel areas PA.

[0049] For example, the active element T of the pixel structure PX can be electrically connected to a scan line GL and a data line DL. The scan line GL is suitable for transmitting a gate signal to the gate of the active element T at a specific time. The data line DL is suitable for transmitting a grayscale signal to the active element T when the gate is turned on to charge and discharge the pixel electrode PE so that the pixel electrode PE has a potential corresponding to the displayed grayscale. In this embodiment, the counter electrodes OE of each pixel structure PX are connected to each other and have a ground potential or a common potential.

[0050] When the pixel electrode PE and the counter electrode OE have a potential difference (i.e., voltage), an electric field is formed between the two, and this electric field can be used to drive the liquid crystal molecules LC of the liquid crystal layer LCL to rotate. More specifically, the arrangement direction of the liquid crystal molecules LC of the liquid crystal layer LCL can be controlled by the voltage applied between the pixel electrode PE and the counter electrode OE.

[0051] For example, in the present embodiment, the liquid crystal molecules LC of the liquid crystal layer LCL may be positive liquid crystal molecules, and the liquid crystal layer LCL is operated in an electrically controlled birefringence (ECB) mode. That is, the liquid crystal molecules LC tend to be arranged along the direction of the electric field under the action of the electric field, and the liquid crystal molecules LC are generally arranged horizontally when not under the action of the electric field (that is, the molecular long axis is generally parallel to the substrate surface). Therefore, in the present embodiment, when a voltage is applied to the pixel electrode PE and the counter electrode OE, the molecular long axis (or optical axis) of the liquid crystal molecules LC is arranged along the direction of the electric field formed between the pixel electrode PE and the counter electrode OE.

[0052] In this embodiment, the reflective display panel 10 further includes a polarizing layer POL, which is disposed on the side of the transparent substrate 200 facing away from the liquid crystal layer LCL and has the functions of polarizing and analyzing the light beam. The light beam from the external environment or the front light source will first pass through the polarizing layer POL before entering the liquid crystal layer LCL through the transparent substrate 200 and have a specific initial polarization state. After the pixel electrode light beam passes through the liquid crystal layer LCL, its initial polarization state will change according to the phase delay amount of the liquid crystal layer LCL on the transmission path of the light beam.

[0053] More specifically, the pixel electrode PE, the counter electrode OE and the liquid crystal layer LCL are located on the transmission path of the light beam from the outside. It is particularly noted that the light beam transmitted toward the pixel array substrate 100 will be reflected by the pixel electrode PE on the pixel array substrate 100 after passing through the liquid crystal layer LCL and pass through the liquid crystal layer LCL again. In other words, the light beam from the outside will be reflected once by the pixel electrode PE during the reflection process of the reflective display panel 10, and pass through the liquid crystal layer LCL, the counter electrode OE, the transparent substrate 200 and the polarizing layer POL twice. Therefore, the total phase delay actually felt by the light beam is twice the phase delay of the liquid crystal layer LCL.

[0054] On the other hand, in order to reflect the light beam back to the transparent substrate 200 for emission, the pixel electrode PE of this embodiment can be made of a metal material with high reflectivity, that is, the pixel electrode PE can be a reflective electrode, but is not limited thereto. In an embodiment not shown, an additional reflective layer can also be provided on the pixel array substrate 100, and the reflective layer overlaps the pixel electrode PE.

[0055] In this embodiment, the reflective display panel 10 is suitable for displaying three colors, such as yellow, white and black, but not limited thereto. Figure 2For example, when the pixel electrode PE and the counter electrode OE in the pixel area PA1 are applied with the first voltage V1, the light beam LB1 entering the pixel area PA1 is reflected by the pixel electrode PE after passing through the liquid crystal layer LCL for the first time, and has a first color when exiting the reflective display panel 10 after passing through the liquid crystal layer LCL for the second time. When the pixel electrode PE and the counter electrode OE in the pixel area PA2 are applied with the second voltage V2, the light beam LB2 entering the pixel area PA2 is reflected by the pixel electrode PE after passing through the liquid crystal layer LCL for the first time, and has a second color when exiting the reflective display panel 10 after passing through the liquid crystal layer LCL for the second time.

[0056] It is particularly noted that when the third voltage V3 is applied to the pixel electrode PE and the counter electrode OE in the pixel area PA3, the light beam LB3 entering the pixel area PA3 is reflected by the pixel electrode PE after passing through the liquid crystal layer LCL for the first time, and cannot pass through the polarizing layer POL after passing through the liquid crystal layer LCL for the second time. In other words, the light beam LB3 entering the pixel area PA3 cannot exit the reflective display panel 10, and the pixel area PA3 presents the third color, that is, black.

[0057] In this embodiment, the chromaticity coordinates (x1, y1) of the aforementioned first color in the CIE1931 color space may be within the chromaticity coordinate range of (0.300±0.05, 0.330±0.05), that is, the first color of this embodiment may be white with high color purity. The chromaticity coordinates (x2, y2) of the aforementioned second color in the CIE1931 color space may be outside the chromaticity coordinate range of (0.300±0.05, 0.330±0.05), for example, within the chromaticity coordinate range of (0.490±0.05, 0.460±0.05). That is, the second color of this embodiment may be yellow.

[0058] Figure 3 FIG. 2 shows a curve distribution diagram of the reflectivity of the reflective display panel 10 of the present embodiment versus the voltage. Figure 2 and Figure 3 In this embodiment, the liquid crystal is a positive liquid crystal, and the first voltage V1 may be in the range of 1.5V to 2.5V, such as 2V, but not limited thereto. The second voltage V2 may be greater than or equal to 0V and less than the first voltage V1. The third voltage V3 may be greater than the first voltage V1 and the second voltage V2, and may be, for example, 7V, but not limited thereto.

[0059] In other embodiments, if the liquid crystal is a negative type liquid crystal, the third voltage V3 for driving the black screen will be greater than or equal to 0V and less than the first voltage V1 for driving the white screen and the second voltage V2 for driving the yellow screen, and the first voltage V1 for driving the white screen will be less than the second voltage V2 for driving the yellow screen.

[0060] Depend on Figure 3 It can be seen that when the driving voltage of the reflective display panel 10 is 2V (i.e., the first voltage V1), the reflectivity of the white screen can reach 40%, which is 36.5% higher than the reflectivity of the white screen of the current reflective display panel driven by the voltage of 0V, which is 29.3%. Since the liquid crystal layer LCL of the present embodiment has a higher phase retardation than the liquid crystal layer of the current reflective display panel and is within the range of 187nm to 240nm, even if the reflectivity of the white screen is greatly improved, the color shift of the white screen will not occur.

[0061] On the other hand, in the current reflective display panel, in order to allow the same pixel area to present white and yellow, a yellow filter pattern is usually set in the pixel area. For example, the projection area of ​​the yellow filter pattern on the reflective surface in the pixel area accounts for 36% of the total reflective surface area, and the area of ​​the portion of the reflective surface that is not overlapped by the yellow filter pattern accounts for 64% of the total reflective surface area. Since 36% of the reflective surface area in the pixel area is set with the yellow filter pattern, the transmittance of this portion will decrease, that is, the overall reflectivity of the reflective display panel will be sacrificed. However, since the pixel area PA of the reflective display panel 10 of the present embodiment does not need to be set with a yellow filter pattern to display yellow, the overall reflectivity of the reflective display panel 10 can be further improved.

[0062] Another embodiment will be listed below to explain the present disclosure in detail, wherein the same components will be marked with the same symbols, and the description of the same technical content will be omitted. For the omitted parts, please refer to the above embodiment and will not be repeated below.

[0063] Figure 4 is a front view schematic diagram of a reflective display panel according to a second embodiment of the present invention. Figure 4 , different from Figure 1 The reflective display panel 10A of this embodiment may further include a plurality of filter patterns FP disposed on the light-transmitting substrate 200 .

[0064] In detail, in the present embodiment, the pixel structure PX-A may include a first pixel electrode PE1, a second pixel electrode PE2, a first active element T1 and a second active element T2. Accordingly, a plurality of first data lines DL1, a plurality of second data lines DL2 and a plurality of scan lines GL may be provided on the pixel array substrate 100. The first data lines DL1 and the second data lines DL2 are alternately arranged along the direction X and extend in the direction Y. The plurality of scan lines GL are arranged along the direction Y and extend in the direction X. The first active element T1 is electrically connected to the first pixel electrode PE1, a scan line GL and a first data line DL1. The second active element T2 is electrically connected to the second pixel electrode PE2, a scan line GL and a second data line DL2.

[0065] For example, in this embodiment, the first pixel electrode PE1 and the second pixel electrode PE2 in each pixel area PA can be arranged side by side along the direction X, but not limited thereto. Since the configuration relationship and driving method of the liquid crystal layer LCL, the first pixel electrode PE1 and the opposite electrode OE in this embodiment are similar to Figure 2 For detailed description of the configuration relationship and driving method of the liquid crystal layer LCL, the pixel electrode PE and the counter electrode OE of the reflective display panel 10, please refer to the relevant paragraphs of the aforementioned embodiment, which will not be repeated here.

[0066] In the present embodiment, a filter pattern FP is provided in each pixel area PA. The filter pattern FP overlaps the second pixel electrode PE2 along the direction Z and does not overlap the first pixel electrode PE1. It is particularly noted that the color of the filter pattern FP of the present embodiment is different from the first color and the second color of the aforementioned embodiment. For example, the color of the filter pattern FP is red, but is not limited thereto.

[0067] Furthermore, the first pixel electrode PE1 and the second pixel electrode PE2 have a first reflective surface RS1 and a second reflective surface RS2, respectively. The filter pattern FP overlaps the second reflective surface RS2 along the direction Z, but does not overlap the first reflective surface RS1. In the present embodiment, the percentage value of the area of ​​the first reflective surface RS1 to the total area of ​​the first reflective surface RS1 and the second reflective surface RS2 may be greater than 55%.

[0068] On the other hand, in the current reflective display panel, in order to allow the same pixel area to present white, yellow and red, a yellow filter pattern and a red filter pattern are usually set in the pixel area. For example, the projection area of ​​the yellow filter pattern on the reflection surface in the pixel area accounts for 33.3% of the total reflection surface area, and the projection area of ​​the red filter pattern on the reflection surface in the pixel area accounts for 33.3% of the total reflection surface area, and the area of ​​the portion of the reflection surface that is not overlapped by the yellow filter pattern and the red filter pattern accounts for 33.3% of the total reflection surface area. Since 33.3% of the reflection surface area in the pixel area is set with a yellow filter pattern, the transmittance of this portion will decrease, which means that the overall reflectivity of the reflective display panel will be sacrificed.

[0069] However, since the reflective display panel 10A of the present embodiment can display yellow without providing a yellow filter pattern in the pixel area PA, the overall reflectivity of the reflective display panel 10A can be further improved.

[0070] In summary, in a reflective display panel of an embodiment of the present invention, the liquid crystal layer has a relatively high phase retardation within a specific range. By applying different voltages to the liquid crystal layer, the light beams passing through the liquid crystal layer and exiting the reflective display panel have different colors. This not only meets the requirements of multi-color display, but also effectively improves the reflectivity and chromaticity performance of the reflective display panel in specific colors.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reflective display panel, adapted to reflect a light beam from outside, characterized in that: The reflective display panel comprises: Pixel array substrate; A light-transmitting substrate, disposed opposite to the pixel array substrate; Pixel structure, including: A first pixel electrode is disposed on the pixel array substrate; and a counter electrode, disposed on the light-transmitting substrate and overlapping the first pixel electrode; and A liquid crystal layer is disposed between the first pixel electrode and the counter electrode, and a phase delay of the liquid crystal layer is in a range of 187 nm to 240 nm. The first pixel electrode, the counter electrode and the liquid crystal layer are located on a transmission path of the light beam. When a first voltage is applied to the first pixel electrode and the counter electrode, the light beam passing through the liquid crystal layer and emitted from the reflective display panel has a first color. When a second voltage is applied to the first pixel electrode and the counter electrode, the second voltage is different from the first voltage, and the light beam passing through the liquid crystal layer and emitted from the reflective display panel has a second color. The chromaticity coordinates (x1, y1) of the first color in the CIE1931 color space are within a chromaticity coordinate range, and the chromaticity coordinates (x2, y2) of the second color in the CIE1931 color space are outside the chromaticity coordinate range.

2. The reflective display panel according to claim 1, characterized in that: The thickness of the liquid crystal layer is in the range of 1.5 μm to 4 μm.

3. The reflective display panel according to claim 1, characterized in that: A reflectivity of the reflective display panel to the light beam having the first color is greater than a reflectivity of the reflective display panel to the light beam having the second color.

4. The reflective display panel according to claim 1, characterized in that: The chromaticity coordinates (x2, y2) of the second color in the CIE1931 color space are within the chromaticity coordinate range of (0.490±0.05, 0.460±0.05).

5. The reflective display panel according to claim 4, characterized in that: The second voltage is greater than or equal to 0V and less than the first voltage.

6. The reflective display panel according to claim 1, characterized in that: The chromaticity coordinate range is (0.300±0.05, 0.330±0.05).

7. The reflective display panel according to claim 5, characterized in that: The first voltage is in the range of 1.5V to 2.5V.

8. The reflective display panel according to claim 1, wherein: The first pixel electrode and the counter electrode are also suitable for being applied with a third voltage so that the light beam passing through the liquid crystal layer cannot be emitted from the reflective display panel, and the third voltage is greater than or less than the first voltage and the second voltage.

9. The reflective display panel according to claim 1, characterized in that: Also includes: A filter pattern, wherein the pixel structure includes a second pixel electrode, the filter pattern overlaps the second pixel electrode and does not overlap the first pixel electrode, and the color of the filter pattern is different from the first color and the second color.

10. The reflective display panel according to claim 9, characterized in that: The first pixel electrode has a first reflection surface, the second pixel electrode has a second reflection surface, the second reflection surface overlaps the filter pattern, and the percentage of the area of ​​the first reflection surface to the total area of ​​the first reflection surface and the second reflection surface is greater than 55%.

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