VIDEO DISPLAY DEVICE

Provided are a liquid crystal panel capable of controlling the viewing angle with less increase in thickness and a video display device including the liquid crystal panel. The video display device includes: a display panel displaying an image; and a liquid crystal panel. The display panel includes at least a polarizer. The polarizer in the display panel is opposite to the liquid crystal panel on the display panel side of the liquid crystal panel. The liquid crystal panel includes, between a pair of transparent substrates, electrodes A arranged at intervals in plan view, a liquid crystal layer, and an electrode B opposite to the electrodes A with the liquid crystal layer interposed therebetween, and includes a voltage application unit which applies voltage between the electrodes A and the electrode B.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-101787 filed on Jun. 21, 2023, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The following disclosure is related to a video display device.

Description of Related Art

A liquid crystal panel which is a main part of a video display device is generally configured so that a liquid crystal layer is sealed between a pair of substrates, and controls the light transmission amount by applying a voltage to the liquid crystal layer to change the alignment state of liquid crystal molecules according to the applied voltage. Such a liquid crystal panel is widely used in various applications taking advantage of the features, such as thinness, lightness in weight, and low power consumption.

In recent years, the enhancement of viewing angle characteristics has been examined in a video display device so that images can be observed at similar levels in either a case where the images are observed in a narrow viewing angle range or a case where the images are observed in a wide viewing angle range. From the viewpoint of maintaining privacy, a display method has been examined which allows the images to be observed in a narrow viewing angle range, but makes the images difficult to observe in a wide viewing angle range. Thus, a display device has been demanded which can be switched between a public mode (also referred to as a wide viewing angle mode) and a privacy mode (also referred to as a narrow viewing angle mode), wherein the public mode allows images to be observed both in the narrow viewing angle range and the wide viewing angle range and the privacy mode allows images to be observed in the narrow viewing angle range and but makes images difficult to be observed in the wide viewing angle range.

With regard to a technology of switching between the viewing angle modes, JP 2007-206373 A, for example, discloses a display device including a liquid crystal display element, a light source, and an optical element disposed therebetween, and describes, as an example, a form in which the optical element has, between a pair of transparent substrates, first regions containing a light-transmitting material and second regions arranged between the first regions and containing a composite material selectively switched between a light-transmitting state and a light scattering or absorption state, and the composite material contains a material obtained by adding a dichroic black dye to a polymer-dispersed liquid crystal. JP 2005-221756 A discloses a video display device in which a viewing angle control element is arranged on the front surface, for example, of the video display device, and describes, as an example, a form in which the viewing angle control element includes a first region and a second region opposite to one pixel, the first region which has first transmittance and the second region in which the transmittance can be switched between a second transmittance and a third transmittance smaller than the first transmittance and the second transmittance, and the second region (light-shielding region) is formed of a guest-host liquid crystal containing a dichroic dye.

WO 2008/047754 discloses a display including a viewing angle control device including a liquid crystal layer to which a dichroic dye is added and a drive circuit that enables switching the display state by changing the alignment state of liquid crystal molecules of the liquid crystal layer, and a display device having a polarizer on the device side. US 2020/0064666 A discloses a display panel including a first display, a second display including a liquid crystal layer interposed between a pair of electrodes, and a polarizer interposed therebetween, in which the liquid crystal layer possessed by the second display is a guest-host liquid crystal cell containing liquid crystal molecules as a host and dye molecules as a guest, and the major axis direction of the liquid crystal molecule and the major axis direction of the dye molecule are parallel to each other.

BRIEF SUMMARY OF THE INVENTION

FIG.27is a schematic cross-sectional view of a video display device1R found by the applicant. As illustrated inFIG.27, the video display device1R includes a liquid crystal panel20R, a display panel10R, and a backlight40in order from the observation surface side to the back surface side. Between the display panel10R and the liquid crystal panel20R, an adhesive layer150for attaching the display panel10R and the liquid crystal panel20R together is provided. The liquid crystal panel20R includes a first transparent substrate210, a first electrode231, a liquid crystal layer240containing a guest-host liquid crystal obtained by adding a dichroic dye (guest) to a liquid crystal material (host), second electrodes232, an interlayer insulating film250, a third electrode233, and a second transparent substrate220in order from the observation surface side. The display panel10R includes a polarizer141, a color filter (CF) substrate110including a CF layer, a liquid crystal layer130, a thin film transistor (TFT) substrate120including TFTs, and a polarizer142in order from the observation surface side.

The liquid crystal layer240possessed by the liquid crystal panel20R has overlapping regions241overlapping the second electrodes232and non-overlapping regions242not overlapping the second electrodes232. The liquid crystal layer240has the features of being the guest-host (GH) liquid crystal layer containing a dichroic dye and having the overlapping regions241and the non-overlapping regions242, so that the liquid crystal layer240has transparent regions and switching regions switched between a transmission state and an absorption state. Such a video display device1R has a function of controlling the viewing angle by applying or not applying a voltage to the liquid crystal layer240, and, in addition to this function, also has a louver function in which the liquid crystal layer240itself functions as a louver. Therefore, the video display device1R is extremely useful in the field of display devices.

However, the inventors of this application have further examined the video display device1R, and have found that the louver function cannot be sufficiently obtained depending on the polarization direction of light incident on the liquid crystal panel20R from the back surface side in some cases. The inventors of this application have found that, even when the video display device1R includes the display panel10R, the liquid crystal panel20R, and the backlight40in order from the observation surface side to the back surface side, the louver function cannot be sufficiently obtained in some cases. Thus, the inventors of this application have found that the video display device1R, which is extremely useful, has still room for improvement to more effectively control the viewing angle.

The inventors of this application have conducted a more detailed examination, and have found that the cause thereof is that light orthogonal to the alignment direction of the liquid crystal molecules in the liquid crystal layer240(GH liquid crystal layer) out of the light incident on the liquid crystal layer240is transmitted without being absorbed. In this case, it is considered that the liquid crystal layer240still has problems with the absorption function due to the switching regions and the transmission function due to the transparent regions. Specifically, it is considered that, in a state where a voltage is applied between the first electrode231and the second electrodes232(262) and a voltage is not applied between the first electrode231and the third electrode233(261) (state where a voltage is applied), for example, the switching regions are not switched to the absorption state, so that omnidirectional light is transmitted (seeFIG.28A), or the transparent regions also enter the absorption state, so that omnidirectional light is blocked (seeFIG.28B).FIGS.28A and28Bare views with which problems that can occur in the video display device1R found by the applicant of this application were examined.

JP 2007-206373 A does not describe anything about having examined the polarization direction of light incident on the optical element. Further, in the optical element described in JP 2007-206373 A, the first region in the transmission state and the second region in which the transmission state and the scattering or absorption state are selectively switched are physically distinguished by differentiating materials used for these regions. The optical element described in JP 2007-206373 A has had various problems in putting it into practical use, such as difficulty in narrowing the viewing angle in common liquid crystal processes and complexity of the manufacturing process.

In the viewing angle control element described in JP 2005-221756 A, the first region having the first transmittance and the second region in which the transmittance can be switched are physically distinguished by differentiating materials used for these regions. The viewing angle control element described in JP 2005-221756 A is extremely useful in the field of display devices because the element can prevent deterioration of the image quality due to a reduction in luminance of the video display device at a wide viewing angle while achieving both a wide viewing angle and a narrow viewing angle. However, the element has had room for contrivance to more effectively achieve the viewing angle control.

The display described in WO 2008/047754 is also extremely useful in the field of display devices because the device is applicable to various usage environments or applications by switching the display state between a wide viewing angle and a narrow viewing angle. However, the device has had room for contrivance to further reduce a light transmission loss in order to further enhance the display luminance. The display panel described in US 2020/0064666 A has been concerned about deterioration of the image quality due to a reduction in luminance at a wide viewing angle, and also has had room for contrivance to facilitate the viewing angle control.

The present invention has been made in view of the above-described circumstances, and aims to provide a liquid crystal panel capable of controlling the viewing angle with less or no increase in thickness and a video display device including the liquid crystal panel.(1) In one embodiment of the present invention, a video display device includes: a display panel configured to display an image; and a liquid crystal panel, the display panel including at least a polarizer, the polarizer provided in the display panel being arranged opposite to the liquid crystal panel on a display panel side of the liquid crystal panel, the liquid crystal panel including, between a pair of transparent substrates, electrodes A arranged at intervals in plan view, a liquid crystal layer, and an electrode B arranged opposite to the electrodes A with the liquid crystal layer between the electrodes A and the electrode B, and including a voltage application unit configured to apply a voltage between the electrodes A and the electrode B, the liquid crystal layer being a guest-host liquid crystal layer containing a dichroic dye and liquid crystal molecules, and including overlapping regions overlapping the electrodes A and non-overlapping regions not overlapping the electrodes A, a transmission axis of the polarizer being substantially vertical to an initial alignment direction of the liquid crystal molecules in plan view.(2) In an embodiment of the present invention, the video display device includes the structure (1) above, and the liquid crystal layer includes a transparent region and a switching region switchable between a transmission state and an absorption state.(3) In an embodiment of the present invention, the video display device includes the structure (2) above, and the transparent regions and the switching regions are formed of the same material.(4) In an embodiment of the present invention, the video display device includes the structure (1), (2), or (3) above, and the electrodes A are arranged in a stripe shape in plan view.(5) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), or (4) above, the liquid crystal panel includes a first transparent substrate, a first electrode, the liquid crystal layer, a second electrode, an interlayer insulating film, a third electrode, and a second transparent substrate in the stated order, the second electrode corresponds to the electrodes A, the first electrode corresponds the electrode B, and the liquid crystal panel further includes a voltage application unit configured to apply a voltage between the first electrode and the third electrode.(6) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), or (4) above, the liquid crystal panel includes a first transparent substrate, a first electrode, a first interlayer insulating film, a second electrode, the liquid crystal layer, a third electrode, a second interlayer insulating film, a fourth electrode, and a second transparent substrate in the stated order, one of the second electrode and the third electrode corresponds to the electrodes A and the other of the second electrode and the third electrode corresponds to the electrode B, the voltage application unit is a unit configured to apply a voltage between the second electrode and the third electrode, and the liquid crystal panel further includes a voltage application unit configured to apply a voltage between the first electrode and the fourth electrode.(7) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), or (4) above, the liquid crystal panel includes a first transparent substrate, a first electrode, a first interlayer insulating film, a second electrode, the liquid crystal layer, a third electrode, a second interlayer insulating film, a fourth electrode, and a second transparent substrate in the stated order, at least one of the second electrode or the third electrode corresponds to the electrodes A, at least one of the first electrode or the fourth electrode corresponds to the electrode B, and the voltage application unit includes a first voltage application unit configured to apply a voltage between the second electrode and the fourth electrode and a second voltage application unit configured to apply a voltage between the first electrode and the third electrode.(8) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), (4), (5), (6), or (7) above, and the non-overlapping regions have a thickness of 30 μm or less.(9) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), (4), (5), (6), (7), or (8) above, and the electrodes A and the electrode B are transparent electrodes.(10) In an embodiment of the present invention, the video display device includes the structure (5), (8), or (9) above, and the first electrode, the second electrode, and the third electrode are transparent electrodes.(11) In an embodiment of the present invention, the video display device includes the structure (6), (7), (8), or (9) above, and the first electrode, the second electrode, the third electrode, and the fourth electrodes are transparent electrodes.(12) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), or (11) above, and further includes a backlight.(13) In an embodiment of the present invention, the video display device includes the structure (12) above, and the backlight has a local dimming function.(14) In an embodiment of the present invention, the video display device includes the structure (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), or (13) above, and the display panel is a liquid crystal display panel or a self-luminous display panel.

The present invention can provide a liquid crystal panel capable of controlling the viewing angle with less or no increase in thickness and a video display device including the liquid crystal panel.

DETAILED DESCRIPTION OF THE INVENTION

Definition of Terms

In this specification, an observation surface side means a side closer to a screen (display surface) of a video display device, and a back surface side means a side farther from the screen (display surface) of the video display device.

A polar angle means an angle formed between a target direction (e.g., measurement direction) and the normal direction of the panel surface of a liquid crystal panel. An azimuth (φ) means a direction when the target direction is projected on the screen of the liquid crystal panel, and is expressed by an angle (azimuthal angle) formed between the target direction and the azimuth serving as the reference.

Herein, the direction serving as the reference (φ=0°) is set to the horizontal right direction of the screen of the liquid crystal panel. For the angle and the azimuthal angle, an angle counterclockwise from the azimuth serving as the reference is a positive angle, an angle clockwise from the azimuth serving as the reference is a negative angle. Both the counterclockwise direction and the clockwise direction indicate the rotation directions when the screen of the liquid crystal panel is viewed from the observation surface side (front). The angle indicates a value measured in a state where the screen of the liquid crystal panel is viewed in plan view.

A state where no voltage is applied means a state where a voltage applied to the liquid crystal layer is less than the threshold voltage (including no voltage application). A state where a voltage is applied means a state where a voltage applied to the liquid crystal layer is equal to or more than the threshold voltage. In this specification, the state where no voltage is applied is also referred to as “when no voltage is applied”, and the state where a voltage is applied is also referred to as “when a voltage is applied”.

The initial alignment direction of liquid crystal molecules means the major axis direction of the liquid crystal molecules when no voltage is applied.

Hereinafter, video display devices according to embodiments of the present invention are described. The present invention is not limited to the description given in the embodiments described below, and can be subject to changes in design as appropriate insofar as the configurations of the present invention are satisfied.

FIGS.1and2Aare schematic cross-sectional views of a video display device of this embodiment.FIG.3Ais a schematic cross-sectional view illustrating a wide viewing angle mode of the video display device of this embodiment.FIG.4Ais a schematic cross-sectional view illustrating a narrow viewing angle mode of the video display device of this embodiment.

A video display device1of this embodiment includes a liquid crystal panel20, a display panel10displaying an image, and a backlight40in order from the observation surface side to the back surface side as illustrated inFIGS.1,2A,3A, and4A. This embodiment can achieve a video display device capable of displaying an image of the display panel10using light from the backlight40and capable of controlling the viewing angle with less increase in thickness. Between the display panel10and the liquid crystal panel20, an adhesive layer150for attaching the display panel10and the liquid crystal panel20together is usually provided.

The liquid crystal panel20includes a first transparent substrate210, a first electrode231, a liquid crystal layer240, second electrodes232, an interlayer insulating film250, a third electrode233, and a second transparent substrate220in order from the observation surface side to the back surface side as illustrated inFIG.1. The second electrodes232are arranged at intervals in plan view, and the second electrodes232and the first electrode231are arranged opposite to each other with the liquid crystal layer240interposed therebetween. The liquid crystal panel20further includes a first voltage application unit262which applies a voltage between the first electrode231and the second electrodes232and a second voltage application unit261which applies a voltage between the first electrode231and the third electrode233. On the display panel side (back surface side in this embodiment) of the liquid crystal panel20, a polarizer141provided in the display panel10is arranged opposite to the liquid crystal panel20. The liquid crystal panel20has a function of controlling the viewing angle, and therefore can be referred to as a “viewing angle control cell”.

The first transparent substrate210and the second transparent substrate220may be substrates transparent to visible light. Examples of the substrate include glass substrates, plastic substrates, and the like.

The first electrode231is arranged in a planar manner over the entire surface of the first transparent substrate210. More specifically, the first electrode231is a solid electrode covering the first transparent substrate210. This allows the entire liquid crystal panel to be switched between the wide viewing angle mode and the narrow viewing angle mode. The first electrode231may be a transparent electrode. The transparent electrode can be formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or tin oxide (SnO), or an alloy thereof, for example.

The second electrodes232are arranged at intervals in plan view. In this specification, the electrodes A mean electrodes arranged at intervals in plan view, and the electrode B means an electrode arranged opposite to the electrode A with the liquid crystal layer240interposed therebetween. In this embodiment, the second electrodes232correspond to the electrodes A, and the first electrode231corresponds to the electrode B. The second electrodes232are arranged at intervals in plan view, so that the liquid crystal layer240has overlapping regions241overlapping the second electrodes232and non-overlapping regions242not overlapping the second electrodes232.

In this embodiment, the electrodes A (second electrodes232in this embodiment) are arranged in a stripe shape (also referred to as a slit shape) in plan view as illustrated inFIG.2B.FIG.2Bis a schematic plan view illustrating the arrangement form of the second electrodes232(electrodes A) in the liquid crystal layer240possessed by the liquid crystal panel20of this embodiment. Examples of the stripe shape include a straight shape illustrated inFIG.5Aand a doglegged shape illustrated inFIG.5B.FIGS.5A and5Bare schematic plan views each illustrating a specific example of the stripe shape. The arrangement of the electrodes A in a stripe shape in plan view as described above can secure sufficient switching regions that can be switched between a transmission state and an absorption state, and therefore the viewing angle in the right-and-left direction of the screen can be effectively controlled. When the electrodes A are arranged in a grid shape in plan view, for example, the switching regions decrease, and the effect of switching between the transmission state and the absorption state cannot be sufficiently obtained.

Herein, the “overlapping the electrodes A” means directly or indirectly contacting the electrodes A. Examples of an aspect of indirectly contacting the electrodes A include an aspect in which the overlapping regions241and the electrodes A contact each other via an alignment film. The alignment film is a film having a function of controlling the alignment of liquid crystal molecules contained in the liquid crystal layer240. The non-overlapping regions242mean regions not overlapping the electrodes A of the liquid crystal layer240.

The width of the electrodes A can be appropriately set considering the desired switching effect or the desired viewing angle. For example, a ratio (W1/W2) between a width W1 of the non-overlapping regions242not overlapping the electrode A and a width W2 of the overlapping regions241overlapping the electrode A may be 100/1 to 100/500 or may be 100/50 to 100/300.

A thickness D of the non-overlapping regions242is preferably 100 μm or less, for example. The thickness is more preferably 50 μm or less, still more preferably 30 μm or less, particularly preferably 20 μm or less, most preferably 10 μm or less. Thus, the liquid crystal panel of this embodiment is applicable to common liquid crystal processes (generally within 10 μm), and has excellent viewing angle performance. The lower limit of the thickness is not limited, and is preferably 1 μm or more, for example.

The thickness of the non-overlapping regions242is also referred to as the height of the non-overlapping regions242. The thickness of the non-overlapping regions242corresponds to a distance D between the first electrode231and the interlayer insulating film250inFIG.6.FIG.6is a conceptual diagram for explaining the thickness D of the non-overlapping region, the width W1 of the non-overlapping region, the width W2 of the overlapping region, and the viewing angle θ.

The pitch between the non-overlapping regions242is preferably smaller than the pixel pitch of the display panel10. This can sufficiently suppress the occurrence of a moire. In particular, the pixel pitch of the display panel10is suitably an integral multiple of the pitch between the non-overlapping regions242. The pixel pitch is more preferably 1 to 50 times, still more preferably 6 to 24 times the pitch between the non-overlapping region.

The viewing angle θ of the liquid crystal panel20in the narrow viewing angle mode can be optionally set by the thickness D and the width W1 of the non-overlapping regions242. Specifically, the viewing angle θ can be set by Equation (2) below:

For the second electrodes232, a transparent electrode is used in this embodiment. Examples of the transparent electrode are as described above.

The third electrode233is arranged in a planar manner over the entire surface of the second transparent substrate220in this embodiment. More specifically, the third electrode233is a solid electrode covering the second transparent substrate220. The third electrode233may be a transparent electrode. Examples of the transparent electrode are as described above.

The liquid crystal layer240is a guest-host liquid crystal layer (also referred to as a GH liquid crystal layer) including dichroic dye (guest)2402and liquid crystal (host) molecules2401. The proportion of the dichroic dye2402is preferably 0.5 to 15% by mass based on the total amount (100% by mass) of the liquid crystal layer240. The proportion is more preferably 1 to 10% by mass, still more preferably 2 to 5%. The color of the dichroic dye2402is not limited, and may be a black color or a red color, or may be adjusted to be a black color by combining two or more types of dyes with different colors. The dichroic dye2402are aligned in the same direction as that of the liquid crystal molecules2401. More specifically, the dichroic dye2402can absorb light vibrating in the same direction as that of the liquid crystal molecules2401.

In this embodiment, as the liquid crystal molecules (also referred to as liquid crystal components)2401, liquid crystal molecules in which a dielectric anisotropy (Δε) has a positive value are used, the dielectric anisotropy (Δε) being defined by Equation L below:

Δε=(Dielectric constant in major axis direction of liquid crystal molecules)−(Dielectric constant in short axis direction of liquid crystal molecules) (L). However, liquid crystal molecules in which a dielectric anisotropy (Δε) has a negative value may be acceptable (see Embodiment 2 below). The liquid crystal molecules having a positive dielectric anisotropy are aligned in a direction parallel to the electric field direction. The liquid crystal molecules having a negative dielectric anisotropy are aligned in a direction vertical to the electric field direction. The liquid crystal molecules having a positive dielectric anisotropy are also referred to as positive liquid crystals (or positive liquid crystal molecules). The liquid crystal molecules having a negative dielectric anisotropy are also referred to as negative liquid crystals (or negative liquid crystal molecules).

The initial alignment direction of the liquid crystal molecules2401is directed in a substantially vertical direction to the transmission axis of a polarizer (polarizer141in this embodiment) arranged on the liquid crystal panel20side opposite to the liquid crystal panel20among polarizers possessed by the display panel10in plan view. More specifically, the transmission axis (also referred to as a polarization transmission axis) of the polarizer141possessed by the display panel10is directed substantially vertical to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240possessed by the liquid crystal panel20in plan view. Specifically, when the polarizer141has a shape having a rectangular plane surface and having a thickness, and the direction of one side of the plane surface of the polarizer141is set as the x-axis direction and the other side thereof is set as the y-axis direction, and the thickness direction is set as the z-axis direction, for example, one of the following forms is suitable: (1) a form in which the transmission axis of the polarizer141is directed along the x-axis direction and the initial alignment direction of the liquid crystal molecules2401is directed along the y-axis direction; or (2) a form in which the transmission axis of the polarizer141is directed along the y-axis direction and the initial alignment direction of the liquid crystal molecules2401is directed along the x-axis direction.

In this specification, the “substantially vertical (also referred to as substantially orthogonal)” and the “substantially vertical arrangement (also referred to as substantially orthogonal arrangement)” with respect to the arrangement angle formed between the initial alignment direction of liquid crystal molecules and the transmission axis direction of a polarizer means forming an angle (absolute value) in the range of 90°+10°. This angle is preferably in the range of 90°+5°, more preferably in the range of 90°+3°, still more preferably in the range of 90°+1º, particularly preferably 90° (completely vertical).

In this embodiment, both the alignment of the liquid crystal molecules2401and the dichroic dye2402in the liquid crystal layer240when no voltage is applied (wide viewing angle mode) and the transmission axis direction (indicated by the arrow) of the polarizer141possessed by the display panel10are indicated on the right side ofFIG.2A(front view). A view (plan view) in which the alignment of the liquid crystal molecules2401in the liquid crystal layer240when no voltage is applied is viewed from directly above (observation surface side) is illustrated in a column (i) ofFIG.2C. A view (plan view) in which the transmission axis direction of the polarizer141possessed by the display panel10is viewed from the observation surface side is illustrated in a column (ii) ofFIG.2C. It is found fromFIG.2Cthat the initial alignment direction (up-and-down direction in the drawing) of the liquid crystal molecules2401and the transmission axis direction (right-and-left direction in the drawing) of the polarizer141are arranged in a substantially vertical arrangement in plan view.

Herein, the inventors of this application have found that the video display device1R cannot sufficiently obtain a louver function depending on the polarization direction of incident light in some cases as described above. Then, the inventors of this application have found that the cause thereof is that light orthogonal to the alignment direction of liquid crystal molecules in the liquid crystal layer240(GH liquid crystal layer) out of the light incident on the liquid crystal layer240is transmitted without being absorbed (see alsoFIGS.27,28A, and28B). Thus, the inventors of this application have solved the problem by arranging the initial alignment direction of the liquid crystal molecules2401and the transmission axis direction of the polarizer141in the substantially vertical arrangement in plan view as described above. This arrangement allows the liquid crystal layer240itself to effectively act as the louver that can be switched on and off. Thus, the video display device1of the present invention has also the louver function in addition to the function of controlling the viewing angle by applying or not applying a voltage. Therefore, the thickness, weight, and manufacturing cost of the liquid crystal panel20or the video display device1including the liquid crystal panel20can be reduced as compared with those of a video display device having a louver layer separately from a liquid crystal panel. To further enhance the louver function, it is better for the liquid crystal molecules2401to have a higher degree of order. For example, the liquid crystal molecules2401preferably have physical property values, such as a high transition point temperature Tni and a small scattering parameter.

As described above, the liquid crystal layer240has the overlapping regions241overlapping the second electrodes232and the non-overlapping regions242not overlapping the second electrodes232. The liquid crystal layer240has the features of being the GH liquid crystal layer containing the liquid crystal molecules having a predetermined initial alignment direction and having the overlapping regions241and the non-overlapping regions242, so that the liquid crystal layer240has transparent regions and switching regions that are switched between the transmission state and the absorption state.

This embodiment is designed to switch the switching regions between the transmission state and the absorption state by applying or not applying a voltage between the first electrode231and the second electrodes232(262). Boundary portions (corresponding to c inFIG.4A) between the overlapping regions241and the non-overlapping regions242serve as the switching regions. Portions (corresponding to a inFIG.4A) obtained by excluding the boundary portions c from the overlapping regions241and portions (corresponding to b inFIG.4A) obtained by excluding the boundary portions c from the non-overlapping regions242serve as the transparent regions. The voltage application unit may be a power supply that can be turned on and off.

The boundary portions between the overlapping regions241and the non-overlapping regions242serving as the switching regions include not only strict boundaries between the overlapping regions241and the non-overlapping regions242, but the overlapping regions241and the non-overlapping regions242around the boundaries. More specifically, the switching region include parts of the overlapping regions241and the non-overlapping regions242(see a to c inFIG.4).

Herein, the important point in the present invention is that the liquid crystal layer240is the GH liquid crystal layer containing the liquid crystal molecules having a predetermined initial alignment direction, and includes the overlapping regions241overlapping the electrodes A (second electrodes232in this embodiment) and the non-overlapping regions242not overlapping the electrodes A, so that the liquid crystal layer240has the transparent regions and the switching regions that are switched between the transmission state and the absorption state. More specifically, the important features of the present invention are that the application of a voltage to each electrode forms the transparent region having high transmittance and the absorption regions having low transmittance in the liquid crystal layer240, so that the liquid crystal layer240itself can act as the louver that can be switched on and off. Therefore, the degree of overlap between the switching regions and the overlapping regions241or the non-overlapping regions242is not limited insofar as the transparent region having high transmittance and the absorption regions having low transmittance are formed when a voltage is applied. The transparent regions and the switching regions are not limited to the form illustrated inFIG.4A, and can be controlled as appropriate by the width and the pitch of the electrodes A, the cell thickness (i.e., thickness D of the non-overlapping regions242), the application of a voltage to each electrode, or the like.

In this embodiment, the second electrodes232and the third electrode233are arranged with the interlayer insulating film250interposed therebetween. In this case, the first electrode231functions as a common electrode, the second voltage application unit261between the first electrode231and the third electrode233controls the voltage application or the no-voltage-application to the non-overlapping regions242, and the first voltage application unit262between the first electrode231and the second electrodes232can control the voltage application or the no-voltage-application to the overlapping regions241. Such an electrode structure is extremely useful because the electrode structure is applicable to various drive systems in the field of video display devices.

The transparent region is a region exhibiting the transmission state both when a voltage is applied and when no voltage is applied. The transmission state is a state having transparency to light. The switching region is a region that is switched between the transmission state and the absorption state. The absorption state is a state where light is absorbed and a state where the transmittance is lower than that of the transmission state. The liquid crystal layer240in the absorption state is in a state similar to that of light blocking glass.

In this embodiment, the liquid crystal layer240has a certain degree of transmittance (also referred to as visible light transmittance or light transmittance) T1 in the wide viewing angle mode (seeFIGS.3A and3B) as described later. In the narrow viewing angle mode (seeFIGS.4A and4B), the transparent regions a and b inFIG.4Ahave transmittances T2 and T3, respectively, and the switching regions c inFIG.4Ahave a transmittance T4 due to the absorption. T1, T2, T3, and T4 satisfy the relationships of “T1≥T2>T4” and “T1≥T3>T4”. The relative magnitudes of T2 and T3 are not limited.

The transmittance T1 may be 100%. The transmittance T4 may be 0%.

FIG.3Bis a view for explaining the alignment direction (initial alignment direction) of the liquid crystal molecules2401in the wide viewing angle mode (FIG.3A) of this embodiment. Specifically,FIG.3Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.3Aviewed from the observation surface side. At the bottom ofFIG.3B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIGS.4B and4Care views for explaining the alignment direction of the liquid crystal molecules2401in the narrow viewing angle mode (FIG.4A) of this embodiment. Specifically,FIG.4Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.4Aviewed from the observation surface side. At the bottom ofFIG.4B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIG.4Cis a view (cross-sectional view) in which only the liquid crystal panel20is extracted fromFIG.4Aand with which the alignment of the liquid crystal molecules2401is examined. The dotted lines inFIG.4Cindicate lines of electric force.

As illustrated inFIGS.3A and4A, light is incident on the liquid crystal panel20via the display panel10from the back surface side (specifically the backlight40). In a state where no voltage is applied between the first electrode231and the second electrodes232(262) and no voltage is applied also between the first electrode231and the third electrode233(261) (state where no voltage is applied), the polarization direction of the light incident on the liquid crystal layer240and the alignment direction of the liquid crystal molecules2401in the liquid crystal layer240are arranged in a substantially orthogonal arrangement (also referred to as substantially vertical arrangement) in plan view (seeFIG.3B), and therefore the incident light is not absorbed in the liquid crystal layer240. More specifically, the liquid crystal layer240is integrated, and the entire liquid crystal layer240enters the transmission state (constitutes a transparent region) (seeFIG.3A). More specifically, the liquid crystal layer240enters a state of having the transmittance T1. In this case, omnidirectional light from the backlight40is transmitted through the liquid crystal panel20(seeFIG.3A). As a result, light from the back surface side can be transmitted without loss from the low polar angle side to the high polar angle side, and therefore the wide viewing angle mode can be achieved with high luminance.

In a state where a voltage is applied between the first electrode231and the second electrodes232(262) and no voltage is applied between the first electrode231and the third electrode233(261) (state where a voltage is applied), the liquid crystal layer240itself acts as the louver. More specifically, light1LB in the oblique direction and part of light1LA in the front direction out of the light incident on the liquid crystal layer240from the backlight40are absorbed (attenuated) in the boundary portions (c regions inFIG.4A) between the overlapping regions241and the non-overlapping regions242and are transmitted as the attenuated light through the liquid crystal panel20(seeFIG.4A). Specifically, mainly in the regions (a regions inFIG.4A) corresponding to the overlapping regions241, longitudinal electric fields are generated between the first electrode231and the second electrodes232, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10(see a regions inFIG.4C), and therefore the incident light is transmitted without being absorbed. Mainly in the regions (b regions inFIG.4A) corresponding to the non-overlapping regions242, no voltage is applied, i.e., the first electrode231and the third electrode233have the same potential. Thus, the liquid crystal molecules2401maintain the substantially horizontal alignment (front view) to the transmission axis of the polarizer141of the display panel10(see b regions inFIG.4C), and therefore the incident light is transmitted without being absorbed. In contrast thereto, in the boundary portions (c regions inFIG.4A) between the overlapping regions241and the non-overlapping regions242, transverse electric fields are generated between the second electrodes232and the third electrode233, so that the alignment direction of the liquid crystal molecules2401is changed by about 90° in plan view (see c regions inFIG.4C). Therefore, the liquid crystal molecules2401are aligned along the electric field direction. In this case, the polarization direction of light incident through the polarizer141of the display panel10and the alignment direction of the liquid crystal molecules2401are matched with each other, and therefore the incident light is absorbed.

By switching the voltages as described above, the regions in the absorption state (switching regions) and the regions in the transmission state (transparent regions) can be formed. Specifically, the a and b regions inFIG.4Aremain in the transmission state, while the c regions inFIG.4Aenter the absorption state. More specifically, the liquid crystal layer240enters a state in which the transparent regions a and b inFIG.4Ahave the transmittances T2 and T3, respectively, and the switching regions c inFIG.4Ahave the transmittance T4 due to the absorption (T1≥T2>T4 and T1≥T3>T4).

Further, the light1LA in the front direction out of the light incident on the liquid crystal panel20from the backlight40is transmitted through the liquid crystal panel20without being attenuated (seeFIG.4A). As a result, the light from the backlight40is attenuated on the high polar angle side, and the light from the back surface side can be transmitted with the same luminance only on the low polar angle side, and therefore the narrow viewing angle mode can be achieved.

In this specification, with respect to the change angle between the initial alignment direction of liquid crystal molecules and the alignment direction of liquid crystal molecules when a voltage is applied, the “substantially 90°” means an angle (absolute value) in the range of 90°±10°. This angle is preferably in the range of 90°±5°, more preferably in the range of 90°±3°, still more preferably in the range of 90°±1º, particularly preferably 90° (completely vertical).

As the interlayer insulating film250, any of an organic insulating film, an inorganic insulating film, or a laminate of an organic insulating film and an inorganic insulating film is usable. As the organic insulating film, an organic film (relative dielectric constant ¿=2 to 5), such as acrylic resin, polyimide resin, or novolac resin, or a laminate thereof is usable, for example. The film thickness of the organic insulating film is not limited, and is 2 μm or more and 4 μm or less, for example. As the inorganic insulating film, an inorganic film (relative dielectric constant ¿=5 to 7), such as silicon nitride (SiNx) or silicon oxide (SiO2), or a laminated film thereof is usable, for example. The film thickness of the inorganic insulating film is not limited, and is 1500 Å or more and 3500 Å or less, for example.

The film thickness of the interlayer insulating film250is preferably 0.1 μm or more and 4 μm or less. The film thickness is more preferably 0.15 μm or more and 0.35 μm or less.

As described above, the liquid crystal panel20is applicable to common liquid crystal processes (generally within 10 μm), and therefore can easily achieve the narrow viewing angle mode and has excellent viewing angle performance. In this embodiment, the transparent regions and the switching regions are not physically distinguished by materials, but distinguished by the design of a power supply (e.g., arrangement of electrodes or the like). The transparent regions and the switching regions are formed of the same material. Therefore, this embodiment does not require a UV curing process to fix the state to the transmission state (transparent region) in advance in manufacturing as illustrated in FIG. 11 of JP 2007-206373 A, for example. Thus, the liquid crystal panel20of this embodiment is also advantageous in that a manufacturing process of the liquid crystal panel or the video display device can be simplified.

The liquid crystal panel20may not have a polarizer. More specifically, the display panel10has the polarizer (polarizer141in this embodiment) on the liquid crystal panel20side, and the polarizer is also usable as the polarizer of the liquid crystal panel20. This eliminates the necessity of adding a polarizer to the liquid crystal panel20, making it possible to further suppress the transmission loss.

The display panel10may be one having a function of displaying images. The display panel10can turn on and off the display of images. This embodiment gives a description taking a case where the display panel10is a liquid crystal display panel as an example.

As illustrated inFIG.1, the display panel10includes the polarizer141, a color filter (CF) substrate110including a CF layer, a liquid crystal layer130, a thin film transistor (TFT) substrate120including TFTs, and a polarizer142in order from the observation surface side to the back surface side. In this embodiment, the display panel10functions as a liquid crystal display panel, and therefore the video display device of this embodiment is a liquid crystal display device.

Among the polarizers possessed by the display panel10, the polarizer (polarizer141in this embodiment) arranged on the liquid crystal panel20side opposite to the liquid crystal panel20has the transmission axis arranged substantially vertically to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20in plan view.

The polarizers141and142may be arranged so that the transmission axes are parallel to each other or may be arranged so that the transmission axes are orthogonal to each other. More specifically, the arrangement of the polarizers141and142may be a parallel Nicols arrangement or a crossed Nicols arrangement.

Herein, the “parallel to each other” means that the transmission axes form an angle in the range of 0°±10°. This angle is preferably in the range of 0°±5°. The “orthogonal to each other” means that the transmission axes form an angle in the range of 90°±10°. This angle is preferably in the range of 90°±5°.

The axis azimuth of the polarizers141and142can be set as appropriate, and are preferably set in the range of 0°±10º or 90°±10°, for example. In particular, the axis azimuths are more preferably set in the range of 0°±5° or 90°±5°, still more preferable substantially set to 0° or 90°. This can achieve a bright display in the normal direction and in the up-and-down and right-and-left directions.

The polarizers141and142are linear polarizers. The linear polarizer is a polarizer having a function of extracting polarized light (linearly polarized light) vibrating only in a specific direction from unpolarized light (natural light), partially polarized light, or polarized light. The polarizer (polarizer142in this embodiment) arranged on the backlight40side is a polarizer corresponding to the wavelength of light from the backlight40. The light from the backlight40is incident on the polarizer142, and only linearly polarized light vibrating along the polarization transmission axis of the polarizer142is transmitted.

The polarizers141and142may be absorption polarizers or reflection polarizers. Both the polarizers141and142may be absorption polarizers or one of the polarizers141and142may be a reflection polarizer and the other one of them may be an absorption polarizer.

Specifically, the absorption polarizer includes a polarizer obtained by dyeing a polyvinyl alcohol film with an anisotropic material such as an iodine complex (or colorant), and making the anisotropic material adsorbed onto the polyvinyl alcohol film, and then stretching and aligning the resultant polyvinyl alcohol film, for example. In general, to ensure mechanical strength and moist heat resistance, the polyvinyl alcohol film is put into practical use with a protective film such as a triacetyl cellulose film being laminated on both sides. Specifically, the reflective polarizer includes a film in which a plurality of dielectric thin films is laminated, a film in which a plurality of thin films different in refractive index anisotropy is laminated, a nanowire grid polarizer, and a polarizer using selective reflection of cholesteric liquid crystals, for example.

As the CF substrate110, those commonly used in the field of liquid crystal display panels are usable, and may be configured so that members, such as a color filter and a black matrix (BM) layer, are arranged on the surface of a transparent substrate such as a glass substrate, for example. More specifically, the CF substrate110includes, on an insulating substrate, a black matrix provided in a lattice shape to correspond to gate lines and source lines, color filters of a plurality of colors including a red layer, a green layer, and a blue layer arranged periodically between the lattices of the black matrix, an overcoat layer formed of a transparent insulating resin provided to cover the black matrix and each color filter, and a photo spacer provided in a columnar shape on the overcoat layer.

The TFT substrate120has an insulating substrate, and includes a plurality of gate lines provided to extend in parallel to each other, and a plurality of source lines provided to extend in parallel to each other in a direction intersecting the gate lines via the insulating film on the insulating substrate in a display region. The plurality of gate lines and the plurality of source lines are formed in a lattice shape as a whole so as to partition each pixel. At the intersection between each source line and each gate line, a thin film transistor is arranged as a switching element.

The TFT substrate120has a planar common electrode arranged on the surface on the liquid crystal layer130side of the insulating substrate, an insulating film covering the common electrode, and pixel electrodes arranged on the surface on the liquid crystal layer130side of the insulating film and each provided with a slit. The pixel electrode is arranged in each region surrounded by two adjacent source lines and two adjacent gate lines. The pixel electrodes are electrically connected to the corresponding source lines via a semiconductor layer provided in the thin film transistor. More specifically, the display panel10of this embodiment is a liquid crystal display panel in a fringe field switching (FFS) mode. The arrangement of the common electrode and the pixel electrodes may be interchanged. In that case, the common electrode provided with slits is arranged on the planar pixel electrode formed to occupy each pixel region via the insulating film.

In this embodiment, the display panel10in a horizontal alignment mode in which the pixel electrodes and the common electrode are provided on one of the substrates. The horizontal alignment mode refers to a mode in which liquid crystal molecules are aligned in a direction substantially horizontal to the principal surface of each of a pair of substrates when no voltage is applied to a liquid crystal layer, and includes, in addition to the above-described FFS mode, an IPS (In-Plane Switching) mode, for example. The display panel10may also be in a vertical alignment mode in which the pixel electrodes are provided on the TFT substrate120and the common electrode is provided on the CF substrate110. The vertical alignment mode refers to a mode in which liquid crystal molecules are aligned in a direction substantially vertical to the principal surface of each of a pair of substrates when no voltage is applied to a liquid crystal layer and includes a vertical alignment (VA) mode, a twisted nematic (TN) mode, and the like, for example.

Between the TFT substrate120and the liquid crystal layer130and between the CF substrate110and the liquid crystal layer130, alignment films having a function of controlling the alignment of liquid crystal molecules contained in the liquid crystal layer130are arranged. In the state where no voltage is applied, in which no voltage is applied between the pixel electrodes and the common electrode, the liquid crystal molecules contained in the liquid crystal layer130are aligned substantially horizontally to the principal surface of each of the pair of substrates.

The display panel10further includes a source driver electrically connected to the source lines, a gate driver electrically connected to the gate lines, and a controller. The gate driver sequentially supplies scanning signals to the gate lines under the control of the controller. The source driver supplies data signals to the source lines under the control of the controller at the timing when the TFT enters the state where a voltage is applied due to the scanning signals. The pixel electrodes each are set to a potential according to the data signal supplied via the corresponding TFT, and a fringe electric field is generated between the pixel electrodes and the common electrode, causing the liquid crystal molecules of the liquid crystal layer to rotate. Thus, the magnitude of the voltage applied between the pixel electrodes and the common electrode is controlled, the retardation of the liquid crystal layer is changed, and the transmission of light and the non-transmission of light are controlled.

The adhesive layer150(OCA, for example) is not limited, and those used in common liquid crystal display devices are also usable. For the liquid crystal layer130, those used in common liquid crystal display devices are also usable. Therefore, descriptions of the adhesive layer150and the liquid crystal layer130are omitted.

The backlight40is not limited insofar as it emits light to the liquid crystal panel20and/or the display panel10. Examples include a configuration in which the backlight40has a light source and a reflective sheet. As the light source, common backlight light sources, i.e., a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), and the like, are usable, for example.

The backlight40may also be a direct-lit one or an edge-lit one. Taking the edge-lit backlight as an example, examples include a configuration in which the backlight40has a light source, a reflective sheet, and a light guiding plate. The light source is arranged on the end surface of the light guiding plate, and the reflective sheet is arranged on the back surface side of the light guiding plate. For the light guiding plate, those commonly used in the field of video display devices are usable. Examples of the reflective sheet include an aluminum plate, a white polyethylene terephthalate (PET) film, and a reflective film (e.g., enhanced specular reflector (ESR) film manufactured by3M).

As the backlight40, a local dimming driving backlight is also usable. The local dimming drive is a function of controlling light for each area, the area being obtained by dividing an image display region of a display device into a plurality of areas (also referred to as segments). The use of the local dimming driving backlight enables the local control of the luminance of the backlight, making it possible to achieve a high contrast ratio and low power consumption of the display device. However, in general, the display device in which the viewing angle is controlled by the backlight is difficult to achieve both the control of the viewing angle and the local dimming drive. In contrast thereto, the present invention can control the viewing angle by the liquid crystal panel20, and therefore a method for driving the backlight is not limited. Therefore, the liquid crystal panel20and the local dimming driving backlight can be combined, which is very useful.

The video display device of this embodiment contains, in addition to the above-described members, external circuits such as a tape carrier package (TCP) and a printed wiring substrate (PCB); optical films such as a viewing angle expansion film and a luminance enhancement film; and a bezel (frame), and some members may be incorporated into other members. Members other than those previously described are not limited, and those commonly used in the field of video display devices are usable, and therefore descriptions thereof are omitted.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that liquid crystal molecules in which the dielectric anisotropy (Δε) has a negative value are used as the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20.

FIG.7Ais a schematic cross-sectional view of a video display device of this embodiment.FIG.8Ais a schematic cross-sectional view illustrating the wide viewing angle mode of the video display device of this embodiment.FIG.9Ais a schematic cross-sectional view illustrating the narrow viewing angle mode of the video display device of this embodiment.

In this embodiment, the alignment of the liquid crystal molecules2401and the dichroic dye molecules2402in the liquid crystal layer240when no voltage is applied and the transmission axis direction (indicated by the arrow) of the polarizer141possessed by the display panel10are also indicated on the right side ofFIG.7A(front view). A view (plan view) in which the alignment of the liquid crystal molecules2401in the liquid crystal layer240when no voltage is applied is viewed from the observation surface side is illustrated in a column (i) ofFIG.7B. A view (plan view) in which the transmission axis direction of the polarizer141possessed by the display panel10is viewed from the observation surface side is illustrated in a column (ii) ofFIG.7B. It is found fromFIG.7Bthat the initial alignment direction (right-and-left direction in the drawing) of the liquid crystal molecules2401and the transmission axis direction (up-and-down direction in the drawing) of the polarizer141are arranged in the substantially vertical arrangement in plan view.

FIG.8Bis a view for explaining the alignment direction (initial alignment direction) of the liquid crystal molecules2401in the wide viewing angle mode (FIG.8A) of this embodiment. Specifically,FIG.8Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.8Aviewed from the observation surface side. At the bottom ofFIG.8B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIG.9Bis a view for explaining the alignment direction of the liquid crystal molecules2401in the narrow viewing angle mode (FIG.9A) of this embodiment.

Specifically,FIG.9Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.9Aviewed from the observation surface side. At the bottom ofFIG.9B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.

In this embodiment, the liquid crystal layer240has a certain degree of transmittance T1 in the wide viewing angle mode (seeFIGS.8A and8B) as described later. In the narrow viewing angle mode (seeFIGS.9A and9B), the transparent regions a and b inFIG.9Ahave transmittances T2 and T3, respectively, and the switching regions c inFIG.9Ahave a transmittance T4 due to the absorption. T1, T2, T3, and T4 satisfy the relationships of “T1≥T2>T4” and “T1≥T3>T4”. The relative magnitudes of T2 and T3 are not limited.

The transmittance T1 may be 100%. The transmittance T4 may be 0%.

As illustrated inFIGS.8A and9A, light is incident on the liquid crystal panel20via the display panel10from the back surface side (specifically the backlight40). In a state where no voltage is applied between the first electrode231and the second electrodes232(262) and no voltage is applied also between the first electrode231and the third electrode233(261) (state where no voltage is applied), the polarization direction of the light incident on the liquid crystal layer240and the alignment direction of the liquid crystal molecules2401in the liquid crystal layer240are arranged in the substantially orthogonal arrangement (seeFIG.8B) in plan view, and therefore the incident light is not absorbed in the liquid crystal layer240. More specifically, the liquid crystal layer240is integrated, and the entire liquid crystal layer240enters the transmission state (constitutes a transparent region) (seeFIG.8A). More specifically, the liquid crystal layer240enters a state of having the transmittance T1. In this case, omnidirectional light from the backlight40is transmitted through the liquid crystal panel20(seeFIG.8A). As a result, the light from the back surface side can be transmitted without loss from the low polar angle side to the high polar angle side, and therefore the wide viewing angle mode can be achieved with high luminance.

In a state where a voltage is applied between the first electrode231and the second electrodes232(262) and no voltage is applied between the first electrode231and the third electrode233(261) (state where a voltage is applied), the liquid crystal layer240itself acts as the louver. More specifically, the light1LB in the oblique direction and part of the light1LA in the front direction out of the light incident on the liquid crystal layer240from the backlight40are absorbed (attenuated) in the boundary portions (c regions inFIG.9A) between the overlapping regions241and the non-overlapping regions242and are transmitted as the attenuated light through the liquid crystal panel20(seeFIG.9A). Specifically, mainly in the regions (a regions inFIG.9A) corresponding to the overlapping regions241, longitudinal electric fields are generated between the first electrode231and the second electrodes232, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10, and therefore the incident light is transmitted without being absorbed. Mainly in the regions (b regions inFIG.9A) corresponding to the non-overlapping regions242, no voltage is applied, i.e., the first electrode231and the third electrode233have the same potential. Thus, the liquid crystal molecules2401maintain the substantially horizontal alignment (front view) to the transmission axis of the polarizer141of the display panel10, and therefore the incident light is transmitted without being absorbed. In contrast thereto, in the boundary portions (c regions inFIG.9A) between the overlapping regions241and the non-overlapping regions242, transverse electric fields are generated between the second electrodes232and the third electrode233, so that the alignment direction of the liquid crystal molecules2401is changed by about 90° in plan view. Therefore, the liquid crystal molecules2401are aligned along the electric field direction. In this case, the polarization direction of the light incident through the polarizer141of the display panel10and the alignment direction of the liquid crystal molecules2401are matched with each other, and therefore the incident light is absorbed.

By switching the voltages as described above, the regions in the absorption state (switching regions) and the regions in the transmission state (transparent regions) can be formed. Specifically, the a and b regions inFIG.9Aremain in the transmission state, while the c regions inFIG.9Aenter the absorption state. More specifically, the liquid crystal layer240enters a state in which the transparent regions a and b inFIG.9Ahave the transmittances T2 and T3, respectively, and the switching regions c inFIG.9Ahave the transmittance T4 due to the absorption (T1≥T2>T4 and T1≥T3>T4). Further, the light1LA in the front direction out of the light incident on the liquid crystal panel20from the backlight40is transmitted through the liquid crystal panel20without being attenuated (seeFIG.9A). As a result, the light from the backlight40is attenuated on the high polar angle side, and the light from the back surface side can be transmitted with the same luminance only on the low polar angle side, and therefore the narrow viewing angle mode can be achieved.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that the arrangement of the liquid crystal panel20and the display panel10is different.

In the video display device1of Embodiment 1, the display panel10is arranged on the back surface side of the liquid crystal panel20, but the display panel10may be arranged on the observation surface side of the liquid crystal panel20. More specifically, the video display device1may be configured to include the display panel10, the liquid crystal panel20, and the backlight40in order from the observation surface side to the back surface side as illustrated inFIG.10.FIG.10is a schematic cross-sectional view of a video display device of this embodiment.

In this embodiment, the polarizer (polarizer142in this embodiment) arranged on the liquid crystal panel20side opposite to the liquid crystal panel20of the polarizers possessed by the display panel10has the transmission axis arranged substantially vertically to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20in plan view.

In this embodiment, the alignment of the liquid crystal molecules2401and the dichroic dye molecules2402in the liquid crystal layer240when no voltage is applied and the transmission axis direction (indicated by the arrow) of the polarizer142possessed by the display panel10are also indicated (front view) on the right side ofFIG.10(schematic cross-sectional view). A view (plan view) in which the alignment of the liquid crystal molecules2401in the liquid crystal layer240when no voltage is applied is viewed from the observation surface side is illustrated in the column (i) ofFIG.2C. A view (plan view) in which the transmission axis direction of the polarizer142possessed by the display panel10is viewed from the observation surface side is illustrated in the column (ii) ofFIG.2C. It is found fromFIG.2Cthat the initial alignment direction (up-and-down direction in the drawing) of the liquid crystal molecules2401and the transmission axis direction (right-and-left direction in the drawing) of the polarizer142are arranged in the substantially vertical arrangement in plan view.

In this embodiment, light is incident on the liquid crystal panel20from the back surface side (specifically, backlight40), and only light transmitting through the liquid crystal panel20is incident on the display panel10. Also in this case, the wide viewing angle mode and the narrow viewing angle mode can be individually achieved substantially by the same principle as that of Embodiment 1.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that the liquid crystal panel20has a different layer structure (layer arrangement).

FIG.11is a schematic cross-sectional view of a video display device of this embodiment. In Embodiment 1, the liquid crystal panel20includes the first transparent substrate210, the first electrode231, the liquid crystal layer240, the second electrodes232, the interlayer insulating film250, the third electrode233, and the second transparent substrate220in order from the observation surface side to the back surface side (seeFIG.1, for example). In contrast thereto, in this embodiment, the liquid crystal panel20includes the first transparent substrate210, the first electrode231, the liquid crystal layer240, the second electrodes232, the interlayer insulating film250, the third electrode233, and the second transparent substrate220in order from the back surface side to the observation surface side (seeFIG.11). In other words, the liquid crystal panel20of this embodiment includes the second transparent substrate220, the third electrode233, the interlayer insulating film250, the second electrodes232, the liquid crystal layer240, the first electrode231, and the first transparent substrate210in order from the observation surface side to the back surface side.

The second electrodes232are arranged in a stripe shape in plan view, and the second electrodes232and the first electrode231are arranged opposite to each other with the liquid crystal layer240interposed therebetween. The liquid crystal panel20further includes the first voltage application unit262(not illustrated) which applies a voltage between the first electrode231and the second electrodes232, and the second voltage application unit261(not illustrated) which applies a voltage between the first electrode231and the third electrode233. On the display panel side (back surface side in this embodiment) of the liquid crystal panel20, the polarizer141provided in the display panel10is arranged opposite to the liquid crystal panel20.

In this embodiment, the polarizer (polarizer141in this embodiment) arranged on the liquid crystal panel20side opposite to the liquid crystal panel20of the polarizers possessed by the display panel10has the transmission axis arranged substantially vertically to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20in plan view.

In this embodiment, the alignment of the liquid crystal molecules2401and the dichroic dye2402in the liquid crystal layer240when no voltage is applied and the transmission axis direction (indicated by the arrow) of the polarizer142possessed by the display panel10are also indicated (front view) on the right side ofFIG.11(schematic cross-sectional view).

Modification of Embodiment 4

Embodiment 4 describes the aspect in which the display panel10is arranged on the back surface side of the liquid crystal panel20, but the display panel10may be arranged on the observation surface side of the liquid crystal panel20. More specifically, an aspect may be acceptable in which the video display device1includes the display panel10, the liquid crystal panel20, and the backlight40in order from the observation surface side to the back surface side, and the liquid crystal panel20includes the second transparent substrate220, the third electrode233, the interlayer insulating film250, the second electrodes232, the liquid crystal layer240, the first electrode231, and the first transparent substrate210in order from the observation surface side to the back surface side (seeFIG.12). Also in this case, the polarizer (polarizer142in this embodiment) arranged on the liquid crystal panel20side opposite to the liquid crystal panel20of the polarizers possessed by the display panel10has the transmission axis arranged substantially vertically to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20in plan view.FIG.12is a schematic cross-sectional view of the video display device in this example.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that the liquid crystal panel20has a different electrode structure.

FIG.13is a schematic cross-sectional view of a video display device of this embodiment.FIG.14Ais a schematic cross-sectional view illustrating the wide viewing angle mode of the video display device of this embodiment.FIG.15Ais a schematic cross-sectional view illustrating the narrow viewing angle mode of the video display device of this embodiment.

In this embodiment, the liquid crystal panel20includes the first transparent substrate210, the first electrode231, a first interlayer insulating film251, second electrodes2321, the liquid crystal layer240, third electrodes2322, a second interlayer insulating film252, a fourth electrode233, and the second transparent substrate220in order from the observation side to the back side as illustrated inFIG.13. The liquid crystal panel20further includes a second voltage application unit263which applies a voltage between the first electrode231and the fourth electrode233, and a first voltage application unit264which applies a voltage between the second electrodes2321and the third electrodes2322. The polarizer141provided in the display panel10is arranged opposite to the liquid crystal panel20on the display panel10side (back surface side in this embodiment) of the liquid crystal panel20.

The first electrode231is arranged in a planar manner over the entire surface of the first transparent substrate210. More specifically, the first electrode231is a solid electrode covering the first transparent substrate210. The fourth electrode233is arranged in a planar manner over the entire surface of the second transparent substrate220. More specifically, the fourth electrode233is a solid electrode covering the second transparent substrate220. The first electrode231and the fourth electrode233may be transparent electrodes. Examples of the transparent electrode are as described above.

The second electrodes2321are arranged in a stripe shape in plan view. The third electrodes2322are also arranged in a stripe shape in plan view. The second electrodes2321and the third electrodes2322are arranged substantially opposite to each other. In this embodiment, both the second electrodes2321and the third electrodes2322correspond to the electrodes A. Therefore, this embodiment also has a form in which the second electrodes2321correspond to the electrodes A and the third electrodes2322correspond to the electrode B or also has a form in which the third electrodes2322correspond to the electrodes A and the second electrodes2321correspond to the electrode B. The second electrodes2321and the third electrodes2322may be transparent electrodes. Examples of the transparent electrode are as described above.

The electrodes A (second electrodes2321and third electrodes2322in this embodiment) are arranged in a stripe shape in plan view and the second electrodes2321and the third electrodes2322are arranged substantially opposite to each other, so that the liquid crystal layer240has the overlapping regions241overlapping the second electrodes2321and the third electrodes2322and the non-overlapping regions242not overlapping the second electrodes2321and the third electrodes2322.

This embodiment is designed to switch the switching regions between the transmission state and the absorption state by applying or not applying a voltage between the second electrodes2321and the third electrodes2322(264) and applying or not applying a voltage between the first electrode231and the fourth electrode233(263). Boundary portions (corresponding to c inFIG.15A) between the overlapping regions241and the non-overlapping regions242serve as the switching regions. Portions (corresponding to a inFIG.15A) obtained by excluding the boundary portions c from the overlapping regions241and portions (corresponding to a′ inFIG.15A) obtained by excluding the boundary portions c from the non-overlapping regions242serve as the transparent regions. The voltage application unit may be a power supply that can be turned on and off.

In this embodiment, the liquid crystal layer240has a certain degree of transmittance T1 in the wide viewing angle mode (seeFIGS.14A and14B) as described later. In the narrow viewing angle mode (seeFIGS.15A and15B), the transparent regions a and a′ inFIG.15Ahave transmittances T2 and T3, respectively, and the switching regions c inFIG.15Ahave a transmittance T4 due to the absorption. T1, T2, T3, and T4 satisfy the relationships of “T1≥T2>T4” and “T1≥T3>T4”. The relative magnitudes of T2 and T3 are not limited.

The transmittance T1 may be 100%. The transmittance T4 may be 0%.

FIG.14Bis a view for explaining the alignment direction (initial alignment direction) of the liquid crystal molecules2401in the wide viewing angle mode (FIG.14A) of this embodiment. Specifically,FIG.14Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.14Aviewed from the observation surface side. At the bottom ofFIG.14B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIG.15Bis a view for explaining the alignment direction of the liquid crystal molecules2401in the narrow viewing angle mode (FIG.15A) of this embodiment.

Specifically,FIG.15Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.15Aviewed from the observation surface side. At the bottom ofFIG.15B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.

As illustrated inFIGS.14A and15A, light is incident on the liquid crystal panel20via the display panel10from the back surface side (specifically the backlight40). Herein, the liquid crystal layer240itself acts as the louver in a state where a region different in the alignment of the liquid crystal molecules2401appears in the liquid crystal layer240(i.e., region different in the electric field appears in the liquid crystal layer240) in plan view. More specifically, the light1LB in the oblique direction and part of the light1LA in the front direction out of the light incident on the liquid crystal layer240from the backlight40are absorbed (attenuated) in the boundary portions (c regions inFIG.15A) between the overlapping regions241and the non-overlapping regions242and are transmitted as the attenuated light through the liquid crystal panel20(seeFIG.15A).

Specifically, mainly in the regions (a regions inFIG.15A) corresponding to the overlapping regions241, longitudinal electric fields are generated between the second electrodes2321and the third electrodes2322, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10, and therefore the incident light is transmitted without being absorbed. Mainly in the regions (a′ regions inFIG.15A) corresponding to the non-overlapping regions242, longitudinal electric fields are generated between the first electrode231and the fourth electrode233, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10, and therefore the incident light is transmitted without being absorbed. In contrast thereto, in the boundary portions (c regions inFIG.15A) between the overlapping regions241and the non-overlapping regions242, transverse electric fields are generated between the first electrode231and the second electrodes2321and between the third electrodes2322and the fourth electrode233, so that the alignment direction of the liquid crystal molecules2401is changed by about 90° in plan view. Therefore, the liquid crystal molecules2401are aligned along the electric field direction. In this case, the polarization direction of the light incident through the polarizer141of the display panel10and the alignment direction of the liquid crystal molecules2401are matched with each other, and therefore the incident light is absorbed.

In a state where the region different in the alignment of the liquid crystal molecules2401does not appear in the liquid crystal layer240in plan view, the polarization direction of the light incident on the liquid crystal layer240and the alignment direction of the liquid crystal molecules2401in the liquid crystal layer240are arranged in a substantially orthogonal arrangement (also referred to as substantially vertical arrangement) in plan view (seeFIG.14B), and therefore the incident light is not absorbed in the liquid crystal layer240. More specifically, the liquid crystal layer240is integrated, and the entire liquid crystal layer240enters the transmission state (constitutes a transparent region) (seeFIG.14A). More specifically, the liquid crystal layer240enters a state of having the transmittance T1. In this case, omnidirectional light from the backlight40is transmitted through the liquid crystal panel20(seeFIG.14A). As a result, the light from the back surface side can be transmitted without loss from the low polar angle side to the high polar angle side, and therefore the wide viewing angle mode can be achieved with high luminance.

Herein, to cause the region different in the alignment of the liquid crystal molecules2401to appear in the liquid crystal layer240(i.e., to cause a region different in the electric field to appear in the liquid crystal layer240) in plan view, it is important that a voltage difference V1 between the first electrode231and the fourth electrode233, a voltage difference V2 between the second electrodes2321and the third electrodes2322, a voltage difference V3 between the first electrode231and the second electrodes2321, and a voltage difference V4 between the third electrodes2322and the fourth electrode233are all in sufficient ranges. Thus, by bringing the liquid crystal layer240into a state where the region different in the alignment of the liquid crystal molecules2401appears in the liquid crystal layer240, the liquid crystal layer240itself acts as the louver. Specifically, V1, V2, V3, and V4 each have a value exceeding 0 V. V1, V2, V3, and V4 each preferably are 2 V or more. The voltage differences V1 and V2 correspond to the voltages of the longitudinal electric fields, and the voltage differences V3 and V4 correspond to the voltages of the transverse electric fields.

Effective voltage application examples of this embodiment include the following aspect.

Examples in which the voltages of the longitudinal electric fields and the transverse electric fields are the same include an aspect in which input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 5 V, 0 V, and 5 V, respectively, as illustrated inFIG.15Cand an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 5 V, 10 V, and 5 V, respectively, as illustrated inFIG.15D, for example. In these cases, V1, V2, V3, and V4 are all 5 V.

Examples in which the voltages of the longitudinal electric fields are the same include an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 3 V, 8 V, and 5 V, respectively, as illustrated inFIG.15Eand an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 1 V, 8 V, 3 V, and 6 V, respectively, as illustrated inFIG.15F, for example. In the former aspect, V1 and V2 are 5 V and V3 and V4 are 3V. In the latter aspect, V1 and V2 are 5 V, V3 is 7 V, and V4 is 3 V.

Examples in which the voltages of the transverse electric fields are the same include an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 4 V, 1 V, and 5 V, respectively, as illustrated inFIG.15G, for example. In this case, V1 is 5 V, V2 is 3 V, and V3 and V4 are 4 V.

FIGS.15C to15Gillustrate the effective voltage application examples of this embodiment. Herein,FIGS.15C to15Gare examples in which such liquid crystal molecules that the alignment of the liquid crystal molecules sufficiently follows, under the voltage of 3 V, the voltage are used. In these drawings, a portion from the first electrode231to the fourth electrode233of the liquid crystal panel20is focused and illustrated. In each drawing, the voltage value described in the parentheses next to each reference numeral indicating the electrode is the input voltage to the electrode. The voltage values (values attached to the arrows) in the drawings are the voltage differences between the voltages. InFIGS.15D to15G, the voltage application units263and264are omitted.

In contrast thereto, when the voltages of the transverse electric fields are 0 V (e.g., an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 5 V, 5 V, 0 V, and 0 V, respectively, or an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 0 V, 5 V, and 5 V, respectively), the region different in the electric field is not generated in the liquid crystal layer240. More specifically, the liquid crystal layer240enters a state in which the longitudinal electric fields are simply applied, and therefore the liquid crystal layer240cannot act as the louver. Cases where the voltages of the longitudinal electric fields and/or the transverse electric fields are 1 V (e.g., an aspect in which the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 1 V, 0 V, and 1 V, respectively, an aspect in which the input voltages to voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 5 V, 4 V, 0 V, and 1 V, respectively, and an aspect in which the input voltages to voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 5 V, 6 V, and 1 V, respectively) are also not effective for causing the louver function by the liquid crystal layer240to exhibit.

By switching the voltages or changing the input voltages as appropriate as described above, the regions in the absorption state (switching regions) and the regions in the transmission state (transparent regions) can be formed. Specifically, the regions a and a′ inFIG.15Aremain in the transmission state, while the c regions inFIG.15Aenter the absorption state. More specifically, the liquid crystal layer240enters a state in which the transparent regions a and a′ inFIG.15Ahave the transmittances T2 and T3, respectively, and the switching regions c inFIG.15Ahave the transmittance T4 due to the absorption (T1≥T2>T4 and T1≥T3>T4). The light1LA in the front direction out of the light incident on the liquid crystal panel20from the backlight40is transmitted through the liquid crystal panel20without being attenuated (seeFIG.15A). As a result, the light from the backlight40is attenuated on the high polar angle side, and the light from the back surface side can be transmitted with the same luminance only on the low polar angle side, and therefore the narrow viewing angle mode can be achieved.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that the liquid crystal panel20has a different electrode structure.

FIG.16is a schematic cross-sectional view of a video display device of this embodiment.FIG.17Ais a schematic cross-sectional view illustrating the wide viewing angle mode of the video display device of this embodiment.FIG.18Ais a schematic cross-sectional view illustrating the narrow viewing angle mode of the video display device of this embodiment.

In this embodiment, the liquid crystal panel20includes the first transparent substrate210, the first electrode231, the first interlayer insulating film251, the second electrodes2321, the liquid crystal layer240, the third electrodes2322, the second interlayer insulating film252, the fourth electrode233, and the second transparent substrate220in order from the observation surface side to the back surface side as illustrated inFIG.16. The liquid crystal panel20further includes a first voltage application unit265which applies a voltage between the first electrode231and the third electrodes2322and a second voltage application unit266which applies a voltage between the second electrodes2321and the fourth electrode233. The polarizer141provided in the display panel10is arranged opposite to the liquid crystal panel20on the display panel10side (back surface side in this embodiment) of the liquid crystal panel20.

The first electrode231is arranged in a planar manner over the entire surface of the first transparent substrate210. More specifically, the first electrode231is a solid electrode covering the first transparent substrate210. The fourth electrode233is arranged in a planar manner over the entire surface of the second transparent substrate220. More specifically, the fourth electrode233is a solid electrode covering the second transparent substrate220. The first electrode231and the fourth electrode233may be transparent electrodes. Examples of the transparent electrode are as described above.

The second electrodes2321are arranged in a stripe shape in plan view. The third electrodes2322are also arranged in a stripe shape in plan view. The second electrodes2321and the third electrodes2322are arranged in a staggered manner so as not to be opposite to each other. More specifically, the third electrodes2322are arranged in the non-overlapping regions of the second electrodes2321and the second electrodes2321are arranged in the non-overlapping regions of the third electrodes2322(seeFIG.16). In this embodiment, both the second electrodes2321and the third electrodes2322correspond to the electrodes A. Therefore, this embodiment also has a form in which the second electrodes2321correspond to the electrodes A and the fourth electrode233corresponds to the electrode B or also has a form in which the third electrodes2322correspond to the electrodes A and the first electrode231corresponds to the electrode B. The second electrodes2321and the third electrodes2322may be transparent electrodes. Examples of the transparent electrode are as described above.

The electrodes A (second electrodes2321and third electrodes2322in this embodiment) are arranged in a stripe shape in plan view and the second electrodes2321and the third electrodes2322are arranged so as not to be opposite to each other, so that the liquid crystal layer240has overlapping regions2411overlapping the second electrodes2321, overlapping regions2412overlapping the third electrodes2322, and the non-overlapping regions242not overlapping the second electrodes2321and the third electrodes2322.

The width of the electrodes A can be appropriately set considering the desired switching effect or the desired viewing angle. For example, a ratio (W1/W2) between the width W1 of the non-overlapping regions242not overlapping the second electrodes2321and the third electrodes2322and the width W2 of either the overlapping regions2412overlapping the second electrodes2321or the overlapping regions2411overlapping the third electrodes2322may be ½ to 1/20 or may be ⅓ to 1/10.

This embodiment is designed to switch the switching regions between the transmission state and the absorption state by applying or not applying a voltage between the first electrode231and the third electrodes2322(265) and applying or not applying a voltage between the second electrodes2321and the fourth electrode233(266). The non-overlapping regions242(corresponding to c inFIG.18A) serve as the switching regions. The overlapping regions2411(corresponding to a″ inFIG.18A) overlapping the second electrodes2321and the overlapping regions2412(corresponding to a inFIG.18A) overlapping the third electrodes2322serve as the transparent regions. Although not explicitly illustrated in the figure, boundary portions between the non-overlapping regions242and the overlapping regions2411or the overlapping regions2412also serve as the switching regions. The voltage application unit may be a power supply that can be turned on and off.

In this embodiment, the liquid crystal layer240has a certain degree of transmittance T1 in the wide viewing angle mode (seeFIGS.17A and17B) as described later. The transparent regions a and a″ inFIG.18Ahave transmittances T2 and T3, respectively, and the switching regions c inFIG.18Ahave a transmittance T4 due to the absorption in the narrow viewing angle mode (seeFIGS.18A and18B). T1, T2, T3, and T4 satisfy the relationships of “T1≥T2>T4” and “T1≥T3>T4”. The relative magnitudes of T2 and T3 are not limited.

The transmittance T1 may be 100%. The transmittance T4 may be 0%.

FIG.17Bis a view for explaining the alignment direction (initial alignment direction) of the liquid crystal molecules2401in the wide viewing angle mode (FIG.17A) of this embodiment. Specifically,FIG.17Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.17Aviewed from the observation surface side. At the bottom ofFIG.17B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIG.18Bis a view for explaining the alignment direction of the liquid crystal molecules2401in the narrow viewing angle mode (FIG.18A) of this embodiment. Specifically,FIG.18Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.18Aviewed from the observation surface side. At the bottom ofFIG.18B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.

As illustrated inFIGS.17A and18A, light is incident on the liquid crystal panel20via the display panel10from the back surface side (specifically the backlight40). In a state where no voltage is applied between the first electrode231and the third electrodes2322(265) and no voltage is applied also between the second electrodes2321and the fourth electrode233(266) (state where no voltage is applied), the polarization direction of the light incident on the liquid crystal layer240and the alignment direction of the liquid crystal molecules2401in the liquid crystal layer240are arranged in the substantially orthogonal arrangement (seeFIG.17B) in plan view, and therefore the incident light is not absorbed in the liquid crystal layer240. More specifically, the liquid crystal layer240is integrated, and the entire liquid crystal layer240enters the transmission state (constitutes a transparent region) (seeFIG.17A). More specifically, the liquid crystal layer240enters a state of having the transmittance T1. In this case, omnidirectional light from the backlight40is transmitted through the liquid crystal panel20(seeFIG.17A). As a result, the light from the back surface side can be transmitted without loss from the low polar angle side to the high polar angle side, and therefore the wide viewing angle mode can be achieved with high luminance.

In a state where a voltage is applied between the first electrode231and the third electrodes2322(265) and a voltage is applied also between the second electrodes2321and the fourth electrode233(266) (state where a voltage is applied), the liquid crystal layer240itself acts as the louver. More specifically, the light1LB in the oblique direction and part of the light1LA in the front direction out of the light incident on the liquid crystal layer240from the backlight40are absorbed (attenuated) in the non-overlapping regions242(c regions inFIG.18A) and are transmitted as the attenuated light through the liquid crystal panel20(seeFIG.18A). Specifically, in the overlapping regions2412(a regions inFIG.18A), longitudinal electric fields are generated between the first electrode231and the third electrodes2322, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10, and therefore the incident light is transmitted without being absorbed. In the overlapping regions2411(a″ regions inFIG.18A), longitudinal electric fields are generated between the second electrodes2321and the fourth electrode233, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10, and therefore the incident light is transmitted without being absorbed. In contrast thereto, in the non-overlapping regions (c regions inFIG.18A), transverse electric fields are generated between the first electrode231and the second electrodes2321and between the third electrode2322and the fourth electrode233, so that the alignment direction of the liquid crystal molecules2401is changed by about 90° in plan view. Therefore, the liquid crystal molecules2401are aligned along the electric field direction. In this case, the polarization direction of the light incident through the polarizer141of the display panel10and the alignment direction of the liquid crystal molecules2401are matched with each other, and therefore the incident light is absorbed.

By switching the voltages as described above, the regions in the absorption state (switching regions) and the regions in the transmission state (transparent regions) can be formed. Specifically, the a and a″ regions inFIG.18Aremain in the transmission state, while the c regions inFIG.18Aenter the absorption state. More specifically, the liquid crystal layer240enters a state in which the transparent regions a and a″ inFIG.18Ahave the transmittances T2 and T3, respectively, and the switching regions c inFIG.18Ahave the transmittance T4 due to the absorption (T1≥T2>T4 and T1≥T3>T4). Further, the light1LA in the front direction out of the light incident on the liquid crystal panel20from the backlight40is transmitted through the liquid crystal panel20without being attenuated (seeFIG.18A). As a result, the light from the backlight40is attenuated on the high polar angle side, and the light from the back surface side can be transmitted with the same luminance only on the low polar angle side, and therefore the narrow viewing angle mode can be achieved.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that the liquid crystal panel20has a different electrode structure.

FIG.19is a schematic cross-sectional view of a video display device of this embodiment.FIG.20Ais a schematic cross-sectional view illustrating the wide viewing angle mode of the video display device of this embodiment.FIG.21Ais a schematic cross-sectional view illustrating the narrow viewing angle mode of the video display device of this embodiment.

In this embodiment, the liquid crystal panel20includes the first transparent substrate210, the first electrodes2321, the liquid crystal layer240, the second electrodes2322, and the second transparent substrate220in order from the observation surface side to the back surface side as illustrated inFIG.19. The liquid crystal panel20further includes the voltage application unit264which applies a voltage between the first electrodes2321and the second electrodes2322. The polarizer141provided in the display panel10is arranged opposite to the liquid crystal panel20on the display panel10side (back surface side in this embodiment) of the liquid crystal panel20.

The first electrodes2321are arranged in a stripe shape in plan view. The second electrodes2322are also arranged in a stripe shape in plan view. The first electrodes2321and the second electrodes2322are arranged substantially opposite to each other. In this embodiment, both the first electrodes2321and the second electrodes2322correspond to the electrodes A. Therefore, this embodiment also has a form in which the first electrodes2321correspond to the electrodes A and the second electrodes2322correspond to the electrode B or also has a form in which the second electrodes2322correspond to the electrodes A and the first electrodes2321correspond to the electrode B.

The electrodes A (first electrodes2321and second electrodes2322in this embodiment) are arranged in a stripe shape in plan view and the first electrodes2321and the second electrodes2322are arranged substantially opposite to each other, so that the liquid crystal layer240has the overlapping regions241overlapping the first electrodes2321and the second electrodes2322and the non-overlapping regions242not overlapping the first electrodes2321and the second electrodes2322.

This embodiment is designed to switch the switching regions between the transmission state and the absorption state by applying or not applying a voltage between the first electrodes2321and the second electrodes2322(264). Boundary portions (corresponding to c inFIG.21A) between the overlapping regions241and the non-overlapping regions242serve as the switching regions. Portions (corresponding to a inFIG.21A) obtained by excluding the boundary portions c from the overlapping regions241and portions (corresponding to d inFIG.21A) obtained by excluding the boundary portions c from the non-overlapping regions242serve as the transparent regions. The voltage application unit may be a power supply that can be turned on and off.

In this embodiment, the liquid crystal layer240has a certain degree of transmittance T1 in the wide viewing angle mode (seeFIGS.20A and20B) as described later. The transparent regions a and d inFIG.21Ahave transmittances T2 and T3, respectively, and the switching regions c inFIG.21Ahave transmittance T4 due to the absorption in the narrow viewing angle mode (seeFIGS.21A and21B). T1, T2, T3, and T4 satisfy the relationships of “T1≥T2>T4” and “T1≥T3>T4”. The relative magnitudes of T2 and T3 are not limited.

The transmittance T1 may be 100%. The transmittance T4 may be 0%.

FIG.20Bis a view for explaining the alignment direction (initial alignment direction) of the liquid crystal molecules2401in the wide viewing angle mode (FIG.20A) of this embodiment. Specifically,FIG.20Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.20Aviewed from the observation surface side. At the bottom ofFIG.20B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIGS.21B and21Care views for explaining the alignment direction of the liquid crystal molecules2401in the narrow viewing angle mode (FIG.21A) of this embodiment. Specifically,FIG.21Bis a view (plan view) of a X-X′ portion of the liquid crystal layer240inFIG.21Aviewed from the observation surface side. At the bottom ofFIG.21B, the transmission axis direction (plan view) of the polarizer141possessed by the display panel10is indicated by the arrow.FIG.21Cis a view (cross-sectional view) in which only the liquid crystal panel20is extracted fromFIG.21Aand with which the alignment of the liquid crystal molecules2401is examined. The dotted lines inFIG.21Cindicate lines of electric force.

As illustrated inFIGS.20A and21A, light is incident on the liquid crystal panel20via the display panel10from the back surface side (specifically the backlight40). In a state where no voltage is applied between the first electrodes2321and the second electrodes2322(264) (state where no voltage is applied), the polarization direction of the light incident on the liquid crystal layer240and the alignment direction of the liquid crystal molecules2401in the liquid crystal layer240are arranged in the substantially orthogonal arrangement (seeFIG.20B) in plan view, and therefore the incident light is not absorbed in the liquid crystal layer240. More specifically, the liquid crystal layer240is integrated, and the entire liquid crystal layer240enters the transmission state (constitutes a transparent region) (seeFIG.20A). More specifically, the liquid crystal layer240enters a state of having the transmittance T1. In this case, omnidirectional light from the backlight40is transmitted through the liquid crystal panel20(seeFIG.20A). As a result, the light from the back surface side can be transmitted without loss from the low polar angle side to the high polar angle side, and therefore the wide viewing angle mode can be achieved with high luminance.

In a state where a voltage is applied between the first electrodes2321and the second electrodes2322(264) (state where a voltage is applied), the liquid crystal layer240itself acts as the louver. More specifically, the light1LB in the oblique direction and part of the light1LA in the front direction out of the light incident on the liquid crystal layer240from the backlight40are absorbed (attenuated) in the boundary portions (c regions inFIG.21B) between the overlapping regions241and the non-overlapping regions242and are transmitted as the attenuated light through the liquid crystal panel20(seeFIG.21B).

Specifically, mainly in the regions (a regions inFIG.21A) corresponding to the overlapping regions241, longitudinal electric fields are generated between the first electrodes2321and the second electrodes2322, and the liquid crystal molecules2401are aligned substantially vertically (front view) to the transmission axis of the polarizer141of the liquid panel10(see a regions inFIG.21C), and therefore the incident light is transmitted without being absorbed. Mainly in the regions (d regions inFIG.21A) corresponding to the non-overlapping regions242, no voltage is applied, and therefore the regions are not affected by any electric field, and thus the liquid crystal molecules2401maintain the initial alignment (see d regions inFIG.21C), and therefore the incident light is transmitted without being absorbed. In contrast thereto, the boundary portions (c regions inFIG.21A) between the overlapping regions241and the non-overlapping regions242, the liquid crystal molecules2401are aligned along the electric field lying out of the electrode width between the first electrodes2321and the second electrodes2322(see c regions inFIG.21C). In this case, the polarization direction of the light incident through the polarizer141of the display panel10and the alignment direction of the0065liquid crystal molecules2401are matched with each other, and therefore the incident light is absorbed.

By switching the voltages as described above, the regions in the absorption state (switching regions) and the regions in the transmission state (transparent regions) can be formed. Specifically, the a and d regions inFIG.21Aremain in the transmission state, while the c regions inFIG.21Aenter the absorption state. More specifically, the liquid crystal layer240enters a state in which the transparent regions a and d inFIG.21Ahave the transmittances T2 and T3, respectively, and the switching regions c inFIG.21Ahave the transmittance T4 due to the absorption (T1≥T2>T4 and T1≥T3>T4).

Further, the light1LA in the front direction out of the light incident on the liquid crystal panel20from the backlight40is transmitted through the liquid crystal panel20without being attenuated (seeFIG.21A). As a result, the light from the backlight40is attenuated on the high polar angle side, and the light from the back surface side can be transmitted with the same luminance only on the low polar angle side, and therefore the narrow viewing angle mode can be achieved.

This embodiment mainly describes the features peculiar to this embodiment, and omits a description overlapping with the description in Embodiment 1 given above. This embodiment is substantially the same as Embodiment 1, except that the display panel10is a self-luminous display panel.

FIG.22is a schematic cross-sectional view of a video display device according to this embodiment. As illustrated inFIG.22, the video display device1of this embodiment includes the liquid crystal panel20of this embodiment (voltage application unit is not illustrated), and a self-luminous display panel as the display panel10displaying images. Between the display panel10and the liquid crystal panel20, the adhesive layer150for attaching the display panel10and the liquid crystal panel20together is provided. The video display device of this embodiment has the self-luminous display panel as the display panel10, and therefore requires no backlight.

The display panel10(self-luminous display panel) has a structure in which a self-luminous layer is interposed between a pair of substrates in this embodiment (seeFIG.22), but is not limited to the structure insofar as it is a self-luminous display panel. For example, the display panel includes an organic electroluminescent (EL) display panel, a display panel containing minute LEDs on the micrometer (μm) scale as RGB elements, and the like. The present invention can control the viewing angle by the liquid crystal panel20regardless of the presence or absence of the backlight. Therefore, the liquid crystal panel20and the self-luminous display panel can be combined, which is very useful.

Although the embodiments of the present invention are described above, all of the individual matters described above are applicable to the entire present invention.

EXAMPLES

The present invention is described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to only these examples. Image display devices of the examples described below were adaptive to common liquid crystal processes, did not cause a moire, and had excellent viewing angle performance and an excellent louver function. In addition, the video display devices were able to achieve the wide viewing angle mode with high luminance, and were able to reduce or prevent an increase in the thickness, weight, and manufacturing cost of each of the video display devices.

A video display device of Example 1 corresponds to the video display device of Embodiment 1 described above (seeFIGS.1to4C). The size of the display panel10was set to 11 inches, the resolution was set to the FHD, and the pixel pitch (Pixel width in extension direction of gate lines x Pixel width in extension direction of source lines) was set to 42 μm×126 μm. Table 1 shows various design values of the liquid crystal panel20.

In the examples described later, the same display panel and the same backlight as the display panel10and the backlight40, respectively, of Example 1 were used unless otherwise specified. Various designs and structures of the liquid crystal panel20are the same as those of Example 1 unless otherwise specified.

FIG.23Aillustrates waveform views of voltages of electrodes in the wide viewing angle mode in the video display device of this example.FIG.23Billustrates waveform views of voltages of electrodes in the narrow viewing angle mode in the video display device of this example. I (231) is the waveform view of the voltage of the first electrode231. II (232) is the waveform view of the voltage of the second electrode232. III (233) is the waveform view of the voltage of the third electrode233. The horizontal axis represents time, and the vertical axis represents the voltage (V). The driving voltage is not limited to this voltage setting, and may be set as appropriate.

In this example, the first electrode231(I) functioned as a common electrode, the non-overlapping regions242were electrically controlled by the voltage application unit between the first electrode231(I) and the third electrode233(III), and the overlapping regions241were electrically controlled by the voltage application unit between the first electrode231(I) and the second electrodes232(II). In this example, the a and b regions inFIG.4Aserve as the transparent regions, and the c regions inFIG.4Aserve as the switching regions.

A video display device of this example corresponds to the video display device of Embodiment 2 described above (seeFIGS.2B, and7A to9B). Example 2 is similar to Example 1 described above, except for using liquid crystal molecules in which the dielectric anisotropy (Δε) has a negative value as the liquid crystal molecules2401.

A video display device of this example corresponds to the video display device of Embodiment 3 described above (seeFIGS.2B,2C, and10). Example 3 is similar to Example 1 described above, except that the arrangement of the liquid crystal panel20and the display panel10is reversed to that of Example 1, and the transmission axis of the polarizer142provided on the liquid crystal panel20side in the display panel10is substantially vertical to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20in plan view.

A video display device of this example corresponds to the video display device of Embodiment 4 described above (seeFIGS.2B,2C, and11). Example 4 is similar to Example 1 described above, except that the liquid crystal panel20has a different layer structure (layer arrangement). The transmission axis of the polarizer141provided on the liquid crystal panel20side in the display panel10is substantially vertical to the initial alignment direction of the liquid crystal molecules2401contained in the liquid crystal layer240of the liquid crystal panel20in plan view.

A video display device of this example corresponds to the video display device of Embodiment 5 described above (FIGS.2B,2C, and13to15C). Example 5 is substantially the same as Example 1 described above, except that the liquid crystal panel20has a different layer structure (layer arrangement). In this example, the input voltages to the first electrode231, the second electrode2321, the third electrode2322, and the fourth electrode233are set to 0 V, 10 V, 0 V, and 10 V, respectively (seeFIG.15C: InFIG.15C, the input voltages to the second and fourth electrodes each are described as 5 V, but are set to 10 V in this example as described above.).

FIG.24Aillustrates waveform views of voltages of electrodes in the wide viewing angle mode in the video display device of this example.FIG.24Billustrates waveform views of voltages of electrodes in the narrow viewing angle mode in the video display device of this example. I (231) is the waveform view of the voltage of the first electrode231. II (2321) is the waveform view of the voltage of the second electrode2321. III (2322) is the waveform view of the voltage of the third electrode2322. IV (233) is the waveform view of the voltage of the fourth electrode233. The horizontal axis represents time, and the vertical axis represents the voltage (V). The driving voltage is not limited to this voltage setting, and may be set as appropriate.

In this example, the non-overlapping regions242were electrically controlled by the voltage application unit between the first electrode231(I) and the fourth electrode233(IV), and the overlapping regions241were electrically controlled by the voltage application unit between the second electrodes2321(II) and the third electrodes2322(III). In this example, the regions a and a′ inFIG.15Aserve as the transparent regions, and the c regions inFIG.15Aserve as the switching regions.

A video display device of this example corresponds to the video display device of Embodiment 6 described above (seeFIGS.2B,2C, and16to18B). Example 6 is substantially the same as Embodiment 1, except that the liquid crystal panel20has a different electrode structure.

FIG.25Aillustrates waveform views of voltages of electrodes in the wide viewing angle mode in the video display device of this example.FIG.25Billustrates waveform views of voltages of electrodes in the narrow viewing angle mode in the video display device of this example. I (231) is the waveform view of the voltage of the first electrode231. II (2321) is the waveform view of the voltage of the second electrode2321. III (2322) is the waveform view of the voltage of the third electrode2322. IV (233) is the waveform view of the voltage of the fourth electrode233. The horizontal axis represents time, and the vertical axis represents the voltage (V). The driving voltage is not limited to this voltage setting, and may be set as appropriate.

In this example, the overlapping regions241were electrically controlled by the voltage application unit between the first electrode231(I) and the third electrodes2322(III) and the voltage application unit between the second electrodes2321(II) and the fourth electrode233(IV). In this example, the regions a and a″ inFIG.18Aserve as the transparent regions, and the c regions inFIG.18Aserve as the switching regions.

A video display device of this example corresponds to the video display device of Embodiment 7 described above (seeFIGS.2B,2C, and19to21C). Example 7 is substantially the same as Embodiment 1, except that the liquid crystal panel20has a different electrode structure.

FIG.26Aillustrates waveform views of voltages of electrodes in the wide viewing angle mode in the video display device of this example.FIG.26Billustrates waveform views of voltages of electrodes in the narrow viewing angle mode in the video display device of this example. I (2321) is the waveform view of the voltage of the first electrode2321. II (2322) is the waveform view of the voltage of the second electrode2322. The horizontal axis represents time, and the vertical axis represents the voltage (V). The driving voltage is not limited to this voltage setting, and may be set as appropriate.

In this example, the overlapping regions241and the non-overlapping regions242were electrically controlled by the voltage application unit between the first electrodes2321(I) and the second electrodes2322(II). In this example, the regions a and d inFIG.21Aserve as the transparent regions, and the c regions inFIG.21Aserve as the switching regions.

A video display device of this example corresponds to the video display device of Embodiment 8 described above (seeFIGS.2B,2C, and22). Even when the liquid crystal panel20and the self-luminous display panel are combined with each other, the video display device having excellent viewing angle performance was able to be achieved while an increase in the thickness, weight, and manufacturing cost was reduced or prevented.

The aspects of the present invention described above may be combined as appropriate without deviating from the gist of the present invention.

REFERENCE SIGNS LIST