Indication device

Abstract

To provide a display device with improved color reproduction. [Solution] The display device 100 has a display panel 10 containing multiple color particles of different colors, and a voltage is applied to the display panel 10 to move the color particles and display an image corresponding to the image data in color by subtractive color mixing. The display device 100 includes an illumination unit 21 having multiple illumination elements of different colors that illuminate the display panel 10 with illumination light of different colors, and a control unit 22 that estimates the degree of difference between the color of the image data and the color of the display image actually displayed, and controls the multiple illumination elements based on the degree of difference.

Description

Technical Field

[0001] The present disclosure relates to a display device that performs color display of a display image by subtractive color mixing. Background Art

[0002] Conventionally, it is known that the perceived color of an image varies depending on the surrounding environment in display devices. Accordingly, methods for providing an image whose color tone perceived by a user does not change even when external light conditions (light characteristics of external light) change have been studied (see, for example, Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2002-041017 Summary of the Invention Problem to be Solved by the Invention

[0004] A conventional image display device includes an image display unit that displays an image based on an input color signal, and a color signal conversion unit that converts the color signal input to the image display unit according to the light characteristics of external light with which the image display unit is irradiated.

[0005] Incidentally, in recent years, electronic paper has been known as a rewritable display panel with low power consumption. Electronic paper includes a display panel provided with a plurality of color capsules containing a plurality of color particles of different colors, and displays an image by applying a voltage to the display panel to move the color particles. However, since the display panel of electronic paper does not emit light by itself, there has been a problem that the range of expressible colors is limited due to the influence of the intensity and tint of ambient light and restrictions on the type and number of colors that can be used.

[0006] The present disclosure has been made to solve the above problem, and an object thereof is to provide a display device with improved color reproducibility. [Means for solving the problem]

[0007] The display device according to this disclosure has a display panel containing a plurality of color particles of different colors, and is a display device that displays a display image corresponding to image data in color by subtractive color mixing by applying a voltage to the display panel to move the color particles, and is characterized by comprising: an illumination unit having a plurality of illumination elements of different colors that irradiate the display panel with illumination light of different colors, and a control unit that estimates the degree of difference between the color of the image data and the color of the display image actually displayed, and controls the plurality of illumination elements based on the degree of difference.

[0008] In the display device according to this disclosure, the control unit may be configured to control the plurality of lighting elements in such a way that the degree of difference becomes small.

[0009] In the display device according to this disclosure, the control unit may be configured to calculate the amount of luminance deficit of the display image that is actually displayed relative to the luminance of the image data for each of the multiple lighting elements, and to control the multiple lighting elements based on the amount of luminance deficit for each of the multiple lighting elements.

[0010] In the display device according to this disclosure, the control unit may be configured to control the plurality of lighting elements based on the proportion of colors in the display image and the amount of luminance deficit for each color of the plurality of lighting elements.

[0011] In the display device according to this disclosure, the illumination unit may be configured to be provided along the outer edge of the display panel.

[0012] The display device according to this disclosure may include an ambient light sensor that detects color information of ambient light, and the control unit may be configured to control the plurality of lighting elements based on the degree of difference and the detection result of the ambient light sensor. [Effects of the Invention]

[0013] According to this disclosure, the degree of difference between the color of the image data that should be displayed on the display panel and the color of the displayed image that is actually displayed is estimated, and the color reproduction is improved by adding and adjusting the color of the illumination part to compensate for this difference, thereby bringing it closer to the target color. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional view showing the structure of a display device according to an embodiment of the present disclosure. [Figure 2] This is a plan view showing the display device as seen from the front. [Figure 3] This is a schematic diagram of the display device according to an embodiment of the present disclosure. [Figure 4] This is an enlarged cross-sectional view showing a magnified view of the area around the display panel. [Modes for carrying out the invention]

[0015] The display device according to the embodiment of this disclosure will be described below with reference to the drawings.

[0016] Figure 1 is a schematic cross-sectional view showing the structure of a display device according to an embodiment of the present disclosure, Figure 2 is a plan view showing the display device as seen from the front, and Figure 3 is a schematic configuration diagram of a display device according to an embodiment of the present disclosure.

[0017] The display device 100 according to the embodiment of this disclosure is used, for example, as electronic paper, electronic shelf labels, electronic advertisements, and e-book terminals. The display device 100 has a display panel 10 containing a plurality of color particles 132 (see Figure 4) of different colors, and a voltage is applied to the display panel 10 to move the color particles 132 and display an image corresponding to the image data in color by subtractive color mixing. The display device 100 has an illumination unit 21 having a plurality of illumination elements 21a relative to the display panel 10, a control unit 22 that controls the plurality of illumination elements 21a, and an ambient light sensor 23 that detects ambient light KL color information. Here, image data refers to the image that is supposed to be displayed, and the display image refers to the image that is actually displayed on the display panel 10.

[0018] In the display device 100, the display panel 10, the control unit 22, and the illumination unit 21 are housed in a housing 1, and an opening 1a is provided on a front surface of the housing 1. The display panel 10 has a size slightly larger than the opening 1a, and is arranged to cover the opening 1a. A region of the display panel 10 corresponding to the opening 1a is a display region where an image is visually recognized by a user. The display panel 10 will be described with reference to FIG. 4 described later.

[0019] The illumination unit 21 is provided along an outer edge of the display panel 10. A plurality of illumination elements 21a each emit illumination light SL of different colors. A combination of colors of the illumination light SL emitted by the plurality of illumination elements 21a may be determined according to a combination of colors of a plurality of color particles 132. In the present embodiment, for example, the configuration is such that it emits illumination light SL of three types of colors such as red, blue, and green, and is provided such that the number of illumination elements 21a corresponding to each color is substantially equal. The combination of colors of the illumination light SL is not limited to this, and may be appropriately changed according to the color of the color particles 132.

[0020] FIG. 2 shows a configuration in which the illumination unit 21 is provided along an upper side and a lower side of the display panel 10 in a top view, but the present invention is not limited thereto. The illumination unit 21 may be provided along a left side and a right side of the display panel 10, and a range where the illumination unit 21 is provided may be appropriately changed. By providing the illumination unit 21 along the outer edge of the display panel 10 in this manner, the illumination light SL can be irradiated to the display panel 10 from a closer position without blocking the display panel 10.

[0021] The control unit 22 estimates a degree of difference between a color of image data and a color of an actually displayed display image, and controls the plurality of illumination elements 21a based on the degree of difference. Processing performed by the control unit 22 will be described together with a relationship between the color of the display panel 10 and the color of the illumination light SL.

[0022] The ambient light sensor 23 is provided exposed on the surface of the housing 1 so as to be capable of receiving light from the outside. The ambient light sensor 23 acquires parameters obtained by quantifying the lightness, saturation, hue, luminance and the like of ambient light KL as color information of the ambient light KL.

[0023] Figure 4 is an enlarged cross-sectional view showing an enlarged periphery of the display panel. In Figure 4, for distinguishing between a plurality of color particles, hatched first color particles 132a and non-hatched second color particles 132b are shown.

[0024] The display panel 10 includes a first substrate 11, a second substrate 12 disposed opposite to the first substrate 11, a plurality of color capsules 13, a first electrode 14, and a second electrode 15.

[0025] The first substrate 11 is formed of a transparent plate member or sheet member such as glass or resin. An antireflection film may be formed on the outer surface of the first substrate 11 (the side opposite to the second substrate 12), or a water-repellent treatment may be applied thereto. The second substrate 12 is formed of a plate member or sheet member such as glass or resin.

[0026] The color capsules 13 are disposed between the first substrate 11 and the second substrate 12, and for example, are laid in one layer. The color capsules 13 are substantially spherical, and have a diameter of not less than several tens of micrometers and not more than several hundreds of micrometers. The color capsule 13 includes a membrane 131, a plurality of color particles 132, and a dispersion liquid 133. The membrane 131 is, for example, a transparent resin membrane. The material of the membrane 131 is not particularly limited, and is, for example, urethane resin, melamine resin, or rubber.

[0027] The color particles 132 constitute a part of an image displayed on the display panel 10, and are pigments that move when a voltage is applied thereto. In the present embodiment, "move" includes moving and rotating. The color particles are electrophoretic particles, and move in the dispersion liquid 133 in accordance with a voltage applied between the first electrode 14 and the second electrode 15. Accordingly, a predetermined image is displayed on the display panel 10.

[0028] The color particles 132 are, for example, organic or inorganic particles. In this embodiment, the color particles 132 include, for example, white particles containing white pigment, red particles containing red pigment, blue particles containing blue pigment, green particles containing green pigment, yellow particles containing yellow pigment, and black particles containing black pigment. The colors of the color particles 132 are not limited to the colors described above, and may consist of, for example, four colors: white, magenta, cyan, and yellow.

[0029] Figure 4 illustrates two particles of different colors, a first-color particle 132a and a second-color particle 132b, for the sake of simplicity. The first-color particle 132a is negatively charged, while the second-color particle 132b is positively charged. In other words, the first-color particle 132a and the second-color particle 132b are not only different in color but also charged with different polarities.

[0030] The dispersion 133 is, for example, a transparent, insulating liquid. The dispersion 133 is not particularly limited, but may include, for example, water, alcoholic solvents, esters, ketones, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, or oils. In this embodiment, the dispersion 133 contains aliphatic hydrocarbons.

[0031] The first electrode 14 and the second electrode 15 are arranged facing each other, with the color capsule 13 in between. The first electrode 14 is positioned on the outside (towards the first substrate 11) relative to the color capsule 13 and is formed on the first substrate 11. The second electrode 15 is positioned on the inside (towards the second substrate 12) relative to the color capsule 13 and is formed on the second substrate 12.

[0032] The first electrode 14 is formed of a light-transmitting conductive material, for example, ITO. In this embodiment, the first electrode 14 is a common electrode, and for example, one is provided for multiple (in this case, all) pixels. The first electrode 14 is grounded and has a ground potential.

[0033] The second electrode 15 is formed of a metallic material such as copper. In this embodiment, the second electrode 15 is a pixel electrode, is formed in a substantially rectangular shape in a plan view, and is provided in multiples. The multiple second electrodes 15 are arranged adjacent to each other with a predetermined gap between them.

[0034] For example, when a positive potential is applied to the second electrode 15, the first color particles 132a are attracted to the second electrode 15, and the second color particles 132b are attracted to the first electrode 14. On the other hand, when a negative potential is applied to the second electrode 15, the first color particles 132a are attracted to the first electrode 14, and the second color particles 132b are attracted to the second electrode 15. In this way, the display device 100 displays an image by controlling the voltage applied to the first electrode 14 and the second electrode 15 to move the color particles 132.

[0035] The display device 100 identifies the color of each pixel in the image data using the luminance of red, green, and blue. For explanatory purposes, red, green, and blue may be collectively referred to as the three primary colors, and when distinguishing between them, red may be abbreviated as R, green as G, and blue as B. In addition, other colors in the color particles 132 may be abbreviated as Y for yellow, M for magenta, C for cyan, and W for white.

[0036] In the display device 100, the color particles 132 are drawn towards the surface (first substrate 11), and the color corresponding to the color particles 132 arranged on the outermost surface is the color visible to the user. In this case, by arranging color particles 132 of different colors, it is made to appear as if colors have been mixed. In this embodiment, the configuration includes four types of color particles 132, but depending on the combination of the colors of the color particles 132, there are colors that are difficult to reproduce.

[0037] For example, with light color combinations like Y+M+C, when color mixing, black doesn't become truly black, resulting in a display image with lower contrast and poor reproduction of dark colors. Conversely, with dark color combinations like Y+R+B, light colors are poorly reproduced.

[0038] Furthermore, there are differences in human visual perception regarding the intensity (luminance) of colored light that reaches the user's eye. Generally, for the three primary colors (RGB), luminance = 0.3R + 0.6G + 0.1B. For example, since magenta light is made up of R and B light, it is 0.3 + 0.1 = 0.4. On the other hand, red light is 0.3 and blue light is 0.1.

[0039] Here, if we scatter 132 red and blue color particles evenly in a 1:1 ratio, we can reflect red and blue light and create magenta. However, since the brightness of red is 0.3 and blue is 0.1, the brightness of the mixed magenta becomes (0.1 + 0.3) ÷ 2 = 0.2, which is a decrease in brightness.

[0040] In contrast, the display device 100 according to this embodiment adjusts the color of the displayed image by irradiating the display panel 10 with illumination light SL from the illumination unit 21. For example, if the color of the image data is magenta with a R luminance of 0.4, and when magenta is reproduced using subtractive color mixing with color particles 132, assuming that the R luminance of the displayed image becomes 0.3, then the R luminance deficit will be 0.1. In this case, the control unit 22 irradiates the display panel 10 with R illumination light SL to compensate for the R luminance deficit. By compensating for the insufficient luminance in this way, the color can be brought closer to the target color.

[0041] As described above, the control unit 22 estimates the degree of difference between the color of the image data that should be displayed on the display panel 10 and the color of the display image that is actually displayed. By adding and adjusting the color of the illumination unit 21 to compensate for this difference, the control unit 22 improves color reproducibility to approach the target color. Furthermore, the control unit 22 can improve color reproducibility by controlling multiple illumination elements 21a to reduce the degree of difference.

[0042] Furthermore, the display device 100 may control the multiple illuminating elements 21a based on the proportion of colors in the displayed image and the amount of brightness deficiency for each color of the multiple illuminating elements 21a. For example, if the area of ​​magenta is the largest among cyan, magenta, yellow, and black in the displayed image, the multiple illuminating elements 21a are controlled to compensate for the brightness deficiency of magenta. In this way, by improving the reproducibility of colors that occupy a large area in the image, the overall appearance of the image can be brought closer to the target color scheme.

[0043] Furthermore, the display device 100 may control multiple illumination elements 21a based on the degree of difference and the detection results of the ambient light sensor 23. For example, in an environment illuminated by yellowish light such as incandescent light, if the ambient light KL is weak in blue, the reflected light from the blue color particles 132 will be weaker when detected by the ambient light sensor 23. Therefore, by supplementing the blue light with illumination light SL, the color shift can be eliminated. In other words, the color tone of the displayed image appears to change depending on the ambient light KL, so by correcting the image while taking this effect into consideration, the color tone can be brought closer to the target color.

[0044] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of symbols]

[0045] 1 cabinet 10 Display Panel 11. First circuit board 12 Second board 13 colored capsules 132 color particles 14 1st electrode 15 2nd electrode 21 Lighting Section 21a Illumination element 22 Control Unit 23 Ambient light sensor 100 display device

Claims

1. A display device having a display panel containing multiple color particles of different colors, wherein a voltage is applied to the display panel to move the color particles, and a display image corresponding to the image data is displayed in color by subtractive color mixing, The display panel is provided with an illumination unit having multiple illumination elements of different colors, each emitting illumination light of a different color. The system includes a control unit that estimates the degree of difference between the color of the image data and the color of the displayed image, and controls the plurality of lighting elements based on the degree of difference. A display device characterized by the following.

2. A display device according to claim 1, The control unit controls the plurality of lighting elements so that the degree of difference becomes smaller. A display device characterized by the following.

3. A display device according to claim 1, The control unit calculates the amount of brightness deficit of the displayed image relative to the brightness of the image data for each of the multiple lighting elements, and controls the multiple lighting elements based on the amount of brightness deficit for each of the multiple lighting elements. A display device characterized by the following.

4. A display device according to claim 3, The control unit controls the plurality of lighting elements based on the proportion of colors in the displayed image and the amount of brightness deficiency for each color of the plurality of lighting elements. A display device characterized by the following.

5. A display device according to claim 1, The illumination unit is provided along the outer edge of the display panel. A display device characterized by the following.

6. A display device according to claim 1, Equipped with an ambient light sensor that detects the color information of the surrounding light, The control unit controls the plurality of lighting elements based on the difference and the detection result of the ambient light sensor. A display device characterized by the following.

Images