This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-205972, filed Dec. 11, 2020, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a liquid crystal display device.
In recent years, in order to improve the contrast of the display device, a technology using a display panel for dimming in addition to a display panel for image display has been developed. However, in this technology, since the two display panels are configured to overlap each other, when an observer observes the display image, parallax according to the distance between the display layer of one display panel and the display layer of the other display panel is generated, and there is a possibility that the display quality is deteriorated such as occurrence of a double image.
In general, according to one embodiment, a liquid crystal display device includes a first display panel, a backlight and a second display panel. The first display panel includes a display area for displaying an image. The backlight is provided on an opposite side of a display surface of the first display panel. The second display panel is provided between the first display panel and the backlight and controls brightness of the image displayed on the first display panel. The first display panel and the second display panel both include a liquid crystal layer. A first refractive index of a member provided between the liquid crystal layer of the second display panel and the liquid crystal layer of the first display panel is higher than a second refractive index of a member provided above the liquid crystal layer of the first display panel.
Embodiments will be described hereinafter with reference to the accompanying drawings.
The disclosure is merely an example, and proper changes within the spirit of the invention, which are easily conceivable by a skilled person, are included in the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are schematically illustrated in the drawings, compared to the actual modes. However, the schematic illustration is merely an example, and adds no restrictions to the interpretation of the invention. Besides, in the specification and drawings, the same or similar elements as or to those described in connection with preceding drawings or those exhibiting similar functions are denoted by like reference numerals, and a detailed description thereof is omitted unless otherwise necessary.
As shown in
The liquid crystal display panel PNL1 has, for example, a rectangular shape. In the illustrated example, a shorter side EX of the liquid crystal display panel PNL1 is parallel to the first direction X, and a longer side EY of the liquid crystal display panel PNL1 is parallel to the second direction Y. The third direction Z corresponds to the thickness direction of the liquid crystal display panel PNL1. The main surface of the liquid crystal display panel PNL1 is parallel to the X-Y plane defined by the first direction X and the second direction Y. The liquid crystal display panel PNL1 includes a display area DA and a peripheral area SA outside the display area DA. The peripheral area SA has a terminal region MT on which an IC chip or a flexible printed circuit is mounted. In
The display area DA is an area for displaying an image, and includes, for example, a plurality of pixels PX arrayed in a matrix. As illustrated in an enlarged manner in
The switching element SW includes, for example, a thin-film transistor (TFT), and is electrically connected to the scanning line G and the signal line S. The scanning line G is electrically connected to the switching element SW in each of the pixels PX arranged in the first direction X. The signal line S is electrically connected to the switching element SW in each of the pixels PX arranged in the second direction Y. The pixel electrode PE is electrically connected to the switching element SW. Each of the pixel electrodes PE faces the common electrode CE, and the liquid crystal layer LC is driven by an electric field generated between the pixel electrode PE and the common electrode CE. The capacitance CS is formed, for example, between an electrode having the same electric potential as the common electrode CE and an electrode having the same electric potential as the pixel electrode PE.
The terminal region MT is provided along the shorter side EX of the liquid crystal display panel PNL1 and includes a terminal for electrically connecting the liquid crystal display panel PNL1 to an external device or the like. The liquid crystal display panel PNL1 is electrically connected to an external device such as a flexible printed circuit via a terminal portion provided in the terminal region MT.
Although a detailed configuration is not shown in
The backlight unit BL is disposed on the lower side of the dimming panel PNL2, and an image is displayed by controlling light from the backlight unit BL for each pixel PX.
As described above, the display device DSP includes the liquid crystal display panel PNL1, the dimming panel PNL2, and the backlight unit BL. In
As shown in
Hereinafter, first, the configuration of the liquid crystal display panel PNL1 will be described.
As shown in
The first polarizer PL11 is provided below the first substrate SUB11, and the second polarizer PL21 is provided above the second substrate SUB21. The polarization axis of the first polarizer PL11 and the polarization axis of the second polarizer PL21 have, for example, a crossed Nicols relationship, that is, 90 degrees.
Next, a configuration of the dimming panel PNL2 will be described.
As shown in
The first polarizer PL12 is provided below the first substrate SUB12, and the second polarizer PL22 is provided above the second substrate SUB22. The polarization axis of the first polarizer PL12 and the polarization axis of the second polarizer PL22 have, for example, a crossed Nicols relationship, that is, 90 degrees. The polarization axis of the first polarizer PL11 of the liquid crystal display panel PNL1 and the polarization axis of the second polarizer PL22 of the dimming panel PNL2 are in the same direction.
Here, problems that may occur in two display panels, specifically, a display device DSP including a liquid crystal display panel PNL1 and a dimming panel PNL2 will be described with reference to
Therefore, when the observer observes the pixel PX1 from the oblique direction of the display surface in order to observe the image displayed on the pixel PX1 of the liquid crystal display panel PNL1, a light beam corresponding to the pixel PX2 of the dimming panel PNL2 is incident on an eye of the observer in addition to a light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1. More specifically, the light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1 is incident on the eye of the observer following an optical path L1 illustrated in
According to this, as shown in
In principle, the parallax can be made zero by the light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1 and the light beam corresponding to the pixel PX2 of the dimming panel PNL2 forming an image at the same position on the retina of the observer. That is, assuming that the pixel PX2 of the dimming panel PNL2 is at the position of a pixel PX2′ from which a light beam following the same optical path as the light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1 can be emitted, the parallax can be made zero, and in view of this, the number of pixels (that is, a difference corresponding to d1 in
As a method for suppressing occurrence of a double image due to the parallax described above, blurring process is known. The blurring process is a method in which, for example, when an image is displayed on the pixel PX1 of the liquid crystal display panel PNL1, in addition to the pixel PX2 of the dimming panel PNL2 corresponding to the pixel PX1, pixels located around the pixel PX2 are controlled to be turned on (or turned off) for dimming, and the image displayed on the liquid crystal display panel PNL1 is blurred and displayed.
In a case where the display image is displayed in white, in the liquid crystal display panel PNL1, as shown in (a) of
According to this, when the display device DSP is observed from the frontal direction, as shown in (a) of
In addition, in a case where the display image is displayed in black, in the liquid crystal display panel PNL1, as shown in (b) of
According to this, when the display device DSP is observed from the frontal direction, as shown in (b) of
As described above, by performing the blurring process in the dimming panel PNL2, it is possible to provide a display image that is less likely to appear as a double image, more specifically, a display image having a larger outline than the display image displayed on the liquid crystal display panel PNL1, to an observer observing the display device DSP from an oblique direction.
In the blurring process described above, the wider the range (hereinafter, referred to as a blurring process range) of the pixel PX2 that is turned on or off so as to spread the high gradation portion to the low gradation portion side, the more it is possible to provide a display image that is less likely to appear as a double image to the observer. On the other hand, when the blurring process range is wide, halo occurs over a wide range, and thus there is a problem that the display quality is deteriorated. That is, according to the blurring process described above, although the occurrence of the double image due to the parallax can be suppressed, if the range of the blurring process is too wide, halo occurs over a wide range, and thus, there is a possibility that the display quality is deteriorated, for example, the display image becomes indistinct.
Therefore, the inventor of the present application has devised a configuration of a display device DSP capable of suppressing the occurrence of the double image due to the parallax by reducing the parallax itself instead of performing the blurring process to suppress the occurrence of the double image due to the parallax. In other words, the configuration of the display device DSP capable of reducing the parallax between the imaging position of the light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1 and the imaging position of the light beam corresponding to the pixel PX2 of the dimming panel PNL2 has been devised.
Specifically, a configuration has been devised in which each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is made of a high refractive member so that the imaging position of the light beam corresponding to the pixel PX2 of the dimming panel PNL2 approaches the imaging position of the light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1, and the parallax can be reduced. More specifically, a configuration has been devised in which each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is made of a high refractive member so that a refractive index (first refractive index) based on each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is higher than a refractive index (second refractive index) based on the second substrate SUB21 and the second polarizer PL21 of the liquid crystal display panel PNL1, and the parallax can be reduced.
Hereinafter, effects of the display device DSP according to the present embodiment will be described using a comparative example. Note that the comparative example is for describing a part of the effects that the display device DSP according to the present embodiment can exhibit, and does not exclude the effects common between the comparative example and the present embodiment from the scope of the present invention.
Note that, in the display device DSP having the configuration according to the present embodiment, as described above, each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is constituted by a high refractive member, and here, as an example, a refractive index based on members from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 indicates a first value n1. Note that the refractive index based on the members from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 corresponds to the refractive index based on the members from the display layer (liquid crystal layer) of the dimming panel PNL2 to the display layer (liquid crystal layer) of the liquid crystal display panel PNL1, and thus may be referred to as an interlayer refractive index.
On the other hand, in the display device DSP having the configuration according to the comparative example, it is assumed that each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is formed of a low refractive member, and for example, an interlayer refractive index from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 indicates a second value n2 (<n1).
In the configuration according to the comparative example, as indicated by a broken line in
Therefore, in the configuration according to the comparative example, as shown in
On the other hand, in the configuration according to the present embodiment, as indicated by the solid line in
Since the configuration according to the present embodiment and the configuration according to the comparative example are similar to each other except that the interlayer refractive index from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is different, the light beam corresponding to the pixel PX1 located above the first substrate SUB11 of the liquid crystal display panel PNL1 is not affected by the difference in the interlayer refractive index described above, and the light beam corresponding to the pixel PX1 of the liquid crystal display panel PNL1 follows the optical path L1 and is incident on the eye of the observer, and forms an image at the first imaging position P1 on the retina of the observer, similarly to the comparative example described above.
According to this, even in the configuration according to the present embodiment, as shown in
Furthermore, according to the configuration according to the present embodiment, as described above, the occurrence of the double image can be suppressed to some extent even if the blurring process is not performed in the dimming panel PNL2. Therefore, for example, in a case where the blurring process is further performed in the dimming panel PNL2 in order to further suppress the occurrence of the double image, it is possible to sufficiently suppress the occurrence of the double image even if the blurring process range is narrow. That is, according to the configuration according to the present embodiment, it is possible to suppress occurrence of halo due to the blurring process and to keep the halo in a narrow range even if the blurring process is further added while suppressing occurrence of a double image due to parallax.
Here, as shown in (a) of
As shown in (b) of
Therefore, in the display device DSP having the configuration according to the present embodiment in which the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 are formed of the high refractive member, the parallax can be reduced, and the occurrence of the double image caused by the parallax can be suppressed.
Here, as shown in (a) and (b) of
Also in this case, as shown in (c) of
Therefore, in the display device DSP having the configuration according to the present embodiment in which the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 are formed of the high refractive member, the parallax can be reduced, and the occurrence of the double image caused by the parallax can be suppressed.
As shown in (c) of
In the display device DSP having the configuration according to the embodiment described above, each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is formed of a high refractive member such that the refractive index based on each part from the second substrate SUB22 of the dimming panel PNL2 to the first substrate SUB11 of the liquid crystal display panel PNL1 is higher than the refractive index based on the second substrate SUB21 and the second polarizer PL21 of the liquid crystal display panel PNL1. Consequently, the occurrence of the double image caused by the parallax can be suppressed, and the degradation of the display quality in the display device including the two display panels can be suppressed.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2020-205972 | Dec 2020 | JP | national |