Reflective display panel

Abstract

To provide a reflective display panel in which the background color display is whiter. [Solution] The reflective display panel includes a first substrate, a second substrate, a liquid crystal layer, a pixel driving layer, a color filter layer, and a polarizer. The pixel driving layer is provided with a reflective layer overlapping the color filter layer. The first filter pattern of the color filter layer has an absorbance of less than 0.05 in the wavelength range of 630 nm to 780 nm, and an absorbance of 0.25 to 0.9 in the wavelength range of 530 nm to 580 nm. The second filter pattern of the color filter layer has an absorbance of less than 0.1 in the wavelength range of 480 nm to 580 nm, and an absorbance of 0.8 to 1.25 in the wavelength range of 630 nm to 680 nm. The third filter pattern of the color filter layer has an absorbance of less than 0.1 in the wavelength range of 430 nm to 480 nm, and an absorbance of 0.95 to 1.3 in the wavelength range of 580 nm to 630 nm.

Description

[Technical Field]

[0001] The present invention relates to a display panel, and more particularly to a reflective display panel. [Background technology]

[0002] Reflective display panels have the advantage of low power consumption, making them ideal for many applications. For example, in some existing product applications, such as electronic labels and e-book readers, the background color of the display on a reflective display panel is mostly white. However, in existing reflective display panels, in order to ensure high electrical conductivity in the transparent electrode layer, the film thickness must be controlled between 1200 angstroms and 1700 angstroms. However, with a transparent electrode layer in this thickness range, the background color of the reflective display panel tends to be yellowish, which adversely affects the display content. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention provides a reflective display panel that displays a whiter background color. [Means for solving the problem]

[0004] The reflective display panel of the present invention includes a first substrate, a second substrate, a liquid crystal layer, a pixel driving layer, a color filter layer, and a polarizer. The first substrate and the second substrate are stacked on top of each other. The liquid crystal layer is provided between the first substrate and the second substrate. The pixel driving layer is provided on the first substrate, and a reflective layer is provided thereon. The color filter layer is provided on the second substrate and overlaps the reflective layer. The color filter layer includes a first filter pattern, a second filter pattern, and a third filter pattern. The first filter pattern has an absorbance of less than 0.05 in the wavelength range of 630 nm to 780 nm, and an absorbance of 0.25 to 0.9 in the wavelength range of 530 nm to 580 nm. The second filter pattern has an absorbance of less than 0.1 in the wavelength range of 480 nm to 580 nm, and an absorbance of 0.8 to 1.25 in the wavelength range of 630 nm to 680 nm. The absorbance of the third filter pattern in the wavelength range of 430 nm to 480 nm is less than 0.1, and the absorbance in the wavelength range of 580 nm to 630 nm is 0.95 to 1.3. The polarizer is provided on the opposite side of the liquid crystal layer from the reflective layer and overlaps the liquid crystal layer.

[0005] In one embodiment of the present invention, the absorbance of the first filter pattern in the wavelength range of 380 nm to 430 nm is 0.1 to 0.45, and the absorbance of the first filter pattern in the wavelength range of 430 nm to 480 nm is 0.3 to 0.6.

[0006] In one embodiment of the present invention, the absorbance of the first filter pattern of the reflective display panel in the wavelength range of 480 nm to 530 nm is 0.45 or more and 0.85 or less.

[0007] In one embodiment of the present invention, the absorbance of the second filter pattern of the reflective display panel in the wavelength range of 380 nm to 430 nm is 0.35 or more and 0.9 or less.

[0008] In one embodiment of the present invention, the second filter pattern of the reflective display panel has an absorbance of 0.6 or more and 0.9 or less in the wavelength range of 385 nm to 400 nm.

[0009] In one embodiment of the present invention, the second filter pattern of the reflective display panel has an absorbance of 0.45 or less in the wavelength range of 430 nm to 480 nm.

[0010] In one embodiment of the present invention, the second filter pattern of the reflective display panel has an absorbance of 0.4 or more and 1.2 or less in the wavelength range of 680 nm to 730 nm.

[0011] In one embodiment of the present invention, the third filter pattern of the reflective display panel has an absorbance of 0.5 or less in the wavelength range of 480 nm to 530 nm.

[0012] In one embodiment of the present invention, the absorbance of the third filter pattern of the reflective display panel in the wavelength range of 530 nm to 580 nm is 0.4 or more and 1.1 or less, the absorbance of the third filter pattern in the wavelength range of 580 nm to 630 nm is 0.95 or more and 1.3 or less, and the absorbance of the third filter pattern in the wavelength range of 630 nm to 680 nm is 0.65 or more and 1.1 or less.

[0013] In one embodiment of the present invention, the single hue b* of the polarizer of the reflective display panel is between 0 and 3.3, and the reflective display panel is suitable for displaying a white screen, with the hue b* of the white screen being between -4.1 and 0.4. [Effects of the Invention]

[0014] In view of the above, in a reflective display panel according to one embodiment of the present invention, a color filter layer is superimposed on a reflective layer of a pixel driving layer. The color filter layer has three filter patterns, each of which has an absorbance of less than 0.1 in three different wavelength ranges. By controlling the absorbance distribution of these three filter patterns in the visible light wavelength range, the problem of the yellowish background color displayed on the reflective display panel can be significantly improved. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view of a reflective display panel according to one embodiment of the present invention. [Figure 2] 2 is a schematic diagram showing the axial relationship between the absorption axis of the polarizer and the optical axis of the liquid crystal layer in FIG. 1. FIG. [Figure 3] 2 is a curve diagram showing the distribution of absorbance with respect to wavelength for the three types of filter patterns in FIG. 1. FIG. [Figure 4] FIG. 10 is a schematic cross-sectional view of a reflective display panel according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Reference will now be made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same element numbers are used in the drawings and the description to refer to the same or like parts.

[0017] Fig. 1 is a schematic cross-sectional view of a reflective display panel according to one embodiment of the present invention. Fig. 2 is a schematic diagram showing the axial relationship between the absorption axis of the polarizer and the optical axis of the liquid crystal layer in Fig. 1. Fig. 3 is a curve diagram showing the distribution of absorbance with respect to wavelength for the three types of filter patterns in Fig. 1. Fig. 4 is a schematic cross-sectional view of a reflective display panel according to another embodiment of the present invention.

[0018] Referring to FIG. 1, the reflective display panel 10 includes a first substrate SUB1, a second substrate SUB2, a liquid crystal layer LCL, and a pixel driving layer PDL. The first substrate SUB1 and the second substrate SUB2 are stacked on top of each other, and the liquid crystal layer LCL is disposed between the first substrate SUB1 and the second substrate SUB2. The above-mentioned overlapping relationship means, for example, that the first substrate SUB1 and the second substrate SUB2 overlap each other along the film thickness direction of the liquid crystal layer LCL (e.g., direction Z). Hereinafter, unless otherwise specified, the overlapping relationship between the two components is defined as above, and a description of the overlapping direction will be omitted.

[0019] The pixel driving layer PDL is provided on the first substrate SUB1, and a reflective layer RFL is provided thereon. For example, the pixel driving layer PDL may be provided with a plurality of signal lines (not shown) and a plurality of active elements (not shown). The plurality of signal lines may include a plurality of data lines and a plurality of scan lines. These data lines and scan lines may define a plurality of pixel regions of the reflective display panel 10, and each of these pixel regions may be provided with a plurality of the aforementioned active elements. Each active element may be electrically connected to a corresponding data line and scan line. In this embodiment, the reflective layer RFL may be provided with a plurality of reflective electrodes RE, and each reflective electrode RE may be electrically connected to an active element, but is not limited thereto.

[0020] In this embodiment, a common electrode layer CEL may be provided on the second substrate SUB2. The common electrode layer CEL and the reflective electrode RE are enabled to modulate the phase retardation of the liquid crystal layer LCL. The common electrode layer CEL is, for example, a translucent electrode, and the material of the translucent electrode may include a metal oxide such as indium tin oxide, indium zinc oxide, aluminum tin oxide, aluminum zinc oxide, or other suitable oxide, or a stack layer of at least two of the above. In this embodiment, the thickness of the common electrode layer CEL along the direction Z may be, but is not limited to, a range of 120 nm to 170 nm.

[0021] For example, in this embodiment, the liquid crystal layer LCL can be driven in an electrically controlled birefringence (ECB) mode, but is not limited thereto. In other embodiments, the liquid crystal layer LCL can be driven in a twisted nematic (TN) mode.

[0022] First, when the reflective electrode RE and the common electrode layer CEL are not enabled, the liquid crystal layer LCL can have a maximum phase retardation, and at this time the reflective display panel 10 displays a white screen. This white screen can be used as the background color display of the reflective display panel 10. The aforementioned maximum phase retardation is defined, for example, as (ne-no)d, where ne is the extraordinary refractive index of the liquid crystal layer LCL, no is the ordinary refractive index of the liquid crystal layer LCL, and d is the thickness of the liquid crystal layer LCL in the film thickness direction Z.

[0023] However, the present invention is not limited thereto. In another embodiment, the pixel driving layer PDL-A of the reflective display panel 10A may be provided with a common electrode layer CEL-A (as shown in FIG. 4). That is, the common electrode layer CEL-A is provided on the first substrate SUB1. In particular, the common electrode layer CEL-A can simultaneously serve as the reflective layer RFL-A of the reflective display panel 10A, i.e., the common electrode layer CEL-A can function as a reflective electrode. Therefore, in the embodiment of FIG. 4, the reflective electrode RE of FIG. 1 can be replaced with a pixel electrode PE made of a transparent conductive material, and the pixel electrode PE can have a plurality of microslits SLT. More specifically, in this embodiment, the liquid crystal layer LCL is driven, for example, in a fringe-field switching (FFS) mode. In another modified embodiment, the liquid crystal layer LCL can also be driven in an in-plane switching (IPS) mode.

[0024] 1 and 2, the reflective display panel 10 further includes a polarizer POL provided on the side of the liquid crystal layer LCL opposite the reflective layer RFL. In this embodiment, for example, the polarizer POL is provided on the surface of the second substrate SUB2 opposite the liquid crystal layer LCL, and the included angle θ between the absorption axis AA of the polarizer POL on the second substrate SUB2 and the orthogonal projection of the optical axis OA of the liquid crystal layer LCL is, for example, but not limited to, 45 degrees.

[0025] To achieve a color display effect, the reflective display panel 10 further includes a color filter layer CFL disposed on the second substrate SUB2 and overlapping the reflective layer RFL. The color filter layer CFL is located between the second substrate SUB2 and the common electrode layer CEL and is suitable for transmitting visible light. In this embodiment, the color filter layer CFL includes a plurality of filter patterns, such as a first filter pattern FP1, a second filter pattern FP2, and a third filter pattern FP3. These filter patterns overlap the plurality of reflective electrodes RE of the reflective layer RFL, respectively.

[0026] For example, in this embodiment, the first filter pattern FP1, the second filter pattern FP2, and the third filter pattern FP3 are suitable for transmitting red light, green light, and blue light, respectively. Referring to FIGS. 1 and 3, more specifically, the absorbance of the first filter pattern FP1 in the wavelength range of 630 nm to 780 nm is less than 0.05 (as shown by curves R1 to R3). The absorbance of the second filter pattern FP2 in the wavelength range of 480 nm to 580 nm is less than 0.1 (as shown by curves G1 to G3). The absorbance of the third filter pattern FP3 in the wavelength range of 430 nm to 480 nm is less than 0.1 (as shown by curves B1 to B3). Thus, the background color display of the reflective display panel 10 has a display effect closer to white.

[0027] In particular, existing reflective display panels have a problem in that the background color display has a yellowish tinge due to the polarizer POL and common electrode layer CEL. To solve this problem, the color filter layer CFL of this embodiment is specially designed to have absorbance distributions in different wavelength ranges of the visible light wavelength range for each of the first filter pattern FP1, second filter pattern FP2, and third filter pattern FP3.

[0028] More specifically, as shown by curves R1 to R3 in Fig. 3, the absorbance of the first filter pattern FP1 in the wavelength range of 380 nm to 430 nm is 0.1 or more and 0.45 or less. The absorbance of the first filter pattern FP1 in the wavelength range of 430 nm to 480 nm is 0.3 or more and 0.6 or less. The absorbance of the first filter pattern FP1 in the wavelength range of 480 nm to 530 nm is 0.45 or more and 0.85 or less. The absorbance of the first filter pattern FP1 in the wavelength range of 530 nm to 580 nm is 0.25 or more and 0.9 or less. The absorbance of the first filter pattern FP1 in the wavelength range of 580 nm to 630 nm is 0.05 or more and 0.45 or less.

[0029] As shown by curves G1 to G3 in FIG. 3, the absorbance of the second filter pattern FP2 in the wavelength range of 380 nm to 430 nm is 0.35 or more and 0.9 or less. The absorbance of the second filter pattern FP2 in the wavelength range of 430 nm to 480 nm is 0.45 or less. The absorbance of the second filter pattern FP2 in the wavelength range of 580 nm to 630 nm is 0.1 or more and 0.9 or less. The absorbance of the second filter pattern FP2 in the wavelength range of 630 nm to 680 nm is 0.8 or more and 1.25 or less. The absorbance of the second filter pattern FP2 in the wavelength range of 680 nm to 730 nm is 0.4 or more and 1.2 or less.

[0030] As shown by curves B1 to B3 in FIG. 3, the absorbance of the third filter pattern FP3 in the wavelength range of 380 nm to 430 nm is 0.5 or less. The absorbance of the third filter pattern FP3 in the wavelength range of 480 nm to 530 nm is 0.5 or less. The absorbance of the third filter pattern FP3 in the wavelength range of 530 nm to 580 nm is 0.4 or more and 1.1 or less. The absorbance of the third filter pattern FP3 in the wavelength range of 580 nm to 630 nm is 0.95 or more and 1.3 or less. The absorbance of the third filter pattern FP3 in the wavelength range of 630 nm to 680 nm is 0.65 or more and 1.1 or less. The absorbance of the third filter pattern FP3 in the wavelength range of 680 nm to 730 nm is 0.6 or more and 0.8 or less. The absorbance of the third filter pattern FP3 in the wavelength range of 730 nm to 780 nm is 0.4 or more and 0.9 or less.

[0031] Of particular note, the first filter pattern FP1 has an absorbance of 0.7 to 0.9 in the wavelength range of 550 to 560 nm, the highest absorbance in the visible light wavelength range. The second filter pattern FP2 has an absorbance of 1.0 to 1.25 in the wavelength range of 650 to 670 nm, the highest absorbance in the visible light wavelength range. The second filter pattern FP2 has an absorbance of 0.6 to 0.9 in the wavelength range of 385 to 400 nm, the second highest absorbance in the visible light wavelength range. The third filter pattern FP3 has an absorbance of 1.1 to 1.3 in the wavelength range of 600 to 620 nm, the highest absorbance in the visible light wavelength range. The third filter pattern FP3 has an absorbance of 0.65 to 0.9 in the wavelength range of 745 to 770 nm, the second highest absorbance in the visible light wavelength range.

[0032] Specifically, in this embodiment, the single hue b* of the polarizer POL can be, but is not limited to, 0 to 3.3. The absorbance distribution design within the visible light wavelength range of each of the first filter pattern FP1, second filter pattern FP2, and third filter pattern FP3 described above can significantly improve the problem of the yellowish background color display (i.e., the aforementioned white screen) of the reflective display panel 10 caused by the polarizer POL and common electrode layer CEL. For example, the hue a* of the white screen of the reflective display panel 10 can be 0 to 2.8, and the hue b* of the white screen can be -4.1 to 0.4.

[0033] The aforementioned hue a* and hue b* are numerical parameters used to define colors in the CIELAB color space. The more positive the hue a*, the more reddish the color, and the more negative the hue a*, the more greenish the color. The more positive the hue b*, the more yellowish the color, and the more negative the hue b*, the more bluish the color. When both hue a* and hue b* are 0, the color is white. In other words, the background color displayed by the reflective display panel 10 of the present invention does not suffer from the problem of a yellowish tint.

[0034] In summary, a reflective display panel according to one embodiment of the present invention includes a color filter layer superimposed on a reflective layer of a pixel driving layer. The color filter layer includes three filter patterns, each of which has an absorbance of less than 0.1 in three different wavelength ranges. By controlling the absorbance distribution of the three filter patterns within the visible light wavelength range, the problem of the yellowish background color displayed on the reflective display panel can be significantly improved.

[0035] Finally, it should be noted that the present invention is not limited to use with fully reflective display panels, but is applicable to any display panel that includes a reflective pixel structure, such as transflective or semi-transmissive displays. [Industrial Applicability]

[0036] The color filter layer of the present invention can be applied to a display panel having a reflective layer. [Explanation of symbols]

[0037] 10, 10A: Reflective display panel AA: Absorption axis CEL, CEL‐A: common electrode layer CFL: Color filter layer FP1~FP3: 1st filter pattern~3rd filter pattern LCL: Liquid crystal layer OA: optical axis PDL, PDL-A: Pixel driving layer PE: pixel electrode POL: Polarizer RE: Reflective electrode RFL, RFL-A: Reflective layer R1~R3, G1~G3, B1~B3: Curve SLT: Micro slit SUB1: First board SUB2: Second board Z: Direction θ: Groove angle

Claims

1. a first substrate and a second substrate provided so as to be stacked on top of each other; a liquid crystal layer provided between the first substrate and the second substrate; a pixel driving layer disposed on the first substrate and having a reflective layer; a color filter layer provided on the second substrate and overlapping the reflective layer; a polarizer provided on the opposite side of the liquid crystal layer from the reflective layer and overlapping the liquid crystal layer, The color filter layer is a first filter pattern having an absorbance of less than 0.05 in a wavelength range of 630 nm to 780 nm and an absorbance of 0.25 or more and 0.9 or less in a wavelength range of 530 nm to 580 nm; a second filter pattern having an absorbance of less than 0.1 in the wavelength range of 480 nm to 580 nm and an absorbance of 0.8 to 1.25 in the wavelength range of 630 nm to 680 nm; a third filter pattern having an absorbance of less than 0.1 in the wavelength range of 430 nm to 480 nm and an absorbance of 0.95 or more and 1.3 or less in the wavelength range of 580 nm to 630 nm.

2. 2. The reflective display panel of claim 1, wherein the absorbance of the first filter pattern in the wavelength range of 380 nm to 430 nm is 0.1 or more and 0.45 or less, and the absorbance of the first filter pattern in the wavelength range of 430 nm to 480 nm is 0.3 or more and 0.6 or less.

3. 2. The reflective display panel according to claim 1, wherein the absorbance of the first filter pattern in the wavelength range of 480 nm to 530 nm is 0.45 or more and 0.85 or less.

4. 2. The reflective display panel according to claim 1, wherein the absorbance of the second filter pattern in the wavelength range of 380 nm to 430 nm is 0.35 or more and 0.9 or less.

5. 5. The reflective display panel according to claim 4, wherein the absorbance of the second filter pattern in the wavelength range of 385 nm to 400 nm is 0.6 or more and 0.9 or less.

6. 2. The reflective display panel according to claim 1, wherein the absorbance of the second filter pattern in the wavelength range of 430 nm to 480 nm is 0.45 or less.

7. 2. The reflective display panel according to claim 1, wherein the absorbance of the second filter pattern in the wavelength range of 680 nm to 730 nm is 0.4 or more and 1.2 or less.

8. 2. The reflective display panel according to claim 1, wherein the absorbance of the third filter pattern in the wavelength range of 480 nm to 530 nm is 0.5 or less.

9. 2. The reflective display panel of claim 1, wherein the absorbance of the third filter pattern in the wavelength range of 530 nm to 580 nm is 0.4 or more and 1.1 or less, the absorbance of the third filter pattern in the wavelength range of 580 nm to 630 nm is 0.95 or more and 1.3 or less, and the absorbance of the third filter pattern in the wavelength range of 630 nm to 680 nm is 0.65 or more and 1.1 or less.

10. 2. The reflective display panel of claim 1, wherein the single hue b* of the polarizer is 0 or more and 3.3 or less, the reflective display panel is suitable for displaying a white screen, and the hue b* of the white screen is -4.1 or more and 0.4 or less.

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