JP2008310271A - Liquid crystal display device and viewing angle control panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device equipped with a viewing angle control panel with which a narrow viewing angle vision with omnidirectional shielding and a wide viewing angle vision are switched between each other by materializing the omnidirectional shielding in viewing with the narrow viewing angle. <P>SOLUTION: The liquid crystal display device 10 is equipped with: a backlight 3; a liquid crystal panel 1 for a display; and a viewing angle control panel 2 with which switching of a viewing angle of the liquid crystal panel 1 for the display between a wide viewing angle mode and a narrow viewing angle mode is conducted. The viewing angle control panel 2 comprises: a polarizing plate 22 over the control panel; a liquid crystal cell 21; and a polarizing plate 23 under the control panel stacked in this order, and retardation plates 24, 25 are respectively disposed between the polarizing plates 22, 23 and the liquid crystal cell 21. Re1 on a white display section in the wide viewing angle mode is set to be nλ/2 (n is an integer of 1 or more), Re2 on the white display section in the narrow viewing angle mode is set to be nλ/2 (n is an integer of 1 or more), and Re3 on a black display section in the narrow viewing angle mode is set to be nλ (n is an integer of 1 or more). The retardation plates 24, 25 are equipped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a viewing angle control panel that switches a viewing angle of a display panel between a wide viewing angle and a narrow viewing angle, and a liquid crystal display device including the viewing angle control panel.

  In general, a display device is required to have a viewing angle as wide as possible so that a clear image can be seen from any viewing angle. In particular, liquid crystal display devices that have been widely used recently have been developed for various viewing angles because the liquid crystal itself has a viewing angle dependency.

  However, depending on the usage environment, it may be more convenient for the viewing angle to be narrow so that only the user himself can view the display content. In particular, a notebook personal computer, a portable information terminal (PDA: Personal Data Assistant), a mobile phone, or the like is highly likely to be used in a place where an unspecified number of people can exist, such as in a train or an airplane. In such a use environment, it is desirable that the viewing angle of the display device is narrow because it is not desirable to look into the display contents from other people in the vicinity from the viewpoint of maintaining confidentiality and protecting privacy. Thus, in recent years, there is an increasing demand for switching the viewing angle of a single display device between a wide viewing angle and a narrow viewing angle depending on the usage situation. This requirement is not limited to the liquid crystal display device, but is a common problem for any display device.

  In response to such a request, for example, Patent Document 1 includes a phase difference control device in addition to a display device that displays an image, and controls the voltage applied to the phase difference control device to control the viewing angle characteristics. Techniques to change are proposed. Patent Document 1 exemplifies chiral nematic liquid crystal, homogeneous liquid crystal, random alignment nematic liquid crystal, and the like as the liquid crystal mode used in the liquid crystal display device for phase difference control.

  Further, for example, in Patent Document 2 and Patent Document 3, a viewing angle control liquid crystal panel is provided on the upper part of the display liquid crystal panel, and these panels are sandwiched between two polarizing plates, and are attached to the viewing angle control liquid crystal panel. A configuration in which viewing angle control is performed by adjusting an applied voltage is also disclosed. In Patent Document 2, the liquid crystal mode of the viewing angle control liquid crystal panel is a twisted nematic system.

Further, for example, in Patent Document 4, a first state in which a first viewing angle range is provided between a backlight and a display device, and a second viewing angle range that is narrower than the first viewing angle range. A display having a liquid crystal device that is switchable between a second state of providing a display and a display is disclosed.
Japanese Patent Laid-Open No. 11-174489 (released on July 2, 1999) Japanese Patent Laid-Open No. 10-268251 (released on October 9, 1998) JP 2005-309020 A (published November 4, 2005) JP 2005-316470 A (published on November 10, 2005) “Nitto Denko Technical Report” 84 (Vol.41), 26-29, 2003

  However, in the above-mentioned conventional patent document 1, it is stated that switching between a wide viewing angle and a narrow viewing angle is possible by using a liquid crystal device for phase difference control, but the effect is not sufficient. For example, as shown in FIG. 25, Patent Document 1 shows an isocontrast curve having a contrast ratio of 10: 1. In the narrow viewing angle mode, the contrast in the wide viewing angle direction surely decreases. However, with such a change, the display is sufficiently visually recognized by the person next to it. This is because the display can be sufficiently visually recognized even when the contrast ratio is reduced to 2: 1.

  The techniques of Patent Documents 2 to 4 also switch the wide viewing angle and the narrow viewing angle by adjusting the contrast by changing the voltage applied to the viewing angle control liquid crystal panel. The effect is not enough.

  That is, any technique of Patent Documents 1 to 4 adopts a method of switching between a wide viewing angle and a narrow viewing angle by reducing the contrast in the wide viewing angle direction. This method has a problem that there is a possibility that an image may be seen from others because the shielding in the wide viewing angle direction is not sufficient when the viewing angle is narrow.

  Further, conventionally, at least two films are required to shield omnidirectionally at a narrow viewing angle, and the omnidirectional shielding mode cannot be realized with one viewing angle switching liquid crystal panel. That is, conventionally, two liquid crystal panels for switching the viewing angle are required in order to shield all directions at a narrow viewing angle.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to switch between a narrow viewing angle and a wide viewing angle of omnidirectional shielding by realizing omnidirectional shielding at a narrow viewing angle. An object of the present invention is to provide a viewing angle control panel and a liquid crystal display device including the same.

  In order to solve the above problems, the liquid crystal display device of the present invention has a backlight, a liquid crystal display panel, and a viewing angle of the liquid crystal display panel within a first viewing angle and the first viewing angle. And a viewing angle control panel that switches between a second viewing angle that is narrower than the first viewing angle. The viewing angle control panel includes a first polarizing plate, a liquid crystal layer, and a second viewing angle control panel. Are provided in this order, and at least one between the first polarizing plate and the liquid crystal layer and between the second polarizing plate and the liquid crystal layer is a retardation plate. Is provided, and when the viewing angle of the liquid crystal display panel is the first viewing angle, the retardation value Re1 of the white display portion is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ. / 4 (n is an integer of 1 or more), and the liquid crystal display panel The retardation value Re2 of the white display portion when the angle is the second viewing angle is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4 (n is an integer of 1 or more), and the liquid crystal display panel The retardation value Re3 of the black display portion when the viewing angle is the second viewing angle is nλ−λ / 4 <Re3 <nλ + λ / 4 (n is an integer of 1 or more), and the retardation plate An optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in x, y, and z directions orthogonal to each other is provided.

  According to the above configuration, when the second viewing angle is narrower than the conventional viewing angle control panel, the shielding region is expanded as compared with the conventional viewing angle control panel (that is, the visible viewing angle range is narrower). A liquid crystal display device can be provided.

  Here, the “white display portion” means an area where light can be transmitted and the display can be visually recognized, and the “black display portion” means an area where light is shielded and the display cannot be visually recognized. Therefore, the “white display portion” can be rephrased as a “viewing region”, and the “black display portion” can be restated as a “non-viewing region”. Here, the retardation value is a phase shift between each component of light that has passed through the viewing angle control panel (more specifically, the phase of light traveling in the plane including the slow axis and the fast axis). The phase of light traveling in the plane including

  In the liquid crystal display device of the present invention, it is preferable that an optical compensation film in which discotic liquid crystal is hybrid-aligned is provided as the retardation plate.

  As a retardation plate, an optical compensation film in which discotic liquid crystals are hybrid-aligned is provided. Here, the phase difference plate has a role of compensating for the retardation value so as to obtain a retardation value for displaying white / black when viewed from each angle.

  By providing the optical compensation film having the main refractive index as described above, it is possible to cancel the retardation caused by the liquid crystal molecules of the liquid crystal layer being inclined at a predetermined pretilt angle. Can be shielded from viewing (that is, omnidirectional shielding can be performed).

  Therefore, a liquid crystal display device that cannot be viewed from a direction other than a specific direction (substantially normal direction in the liquid crystal display panel) and has excellent performance in terms of privacy protection and security enhancement can be provided.

  In the liquid crystal display device of the present invention, as the retardation plate, an optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the x, y, and z directions orthogonal to each other. It is preferable to provide.

  As a retardation plate, an optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the x, y, and z directions orthogonal to each other is provided. Here, the phase difference plate has a role of compensating for the retardation value so as to obtain a retardation value for displaying white / black when viewed from each angle.

  By providing the optical compensation film having the main refractive index as described above, it is possible to cancel the retardation caused by the liquid crystal molecules of the liquid crystal layer being inclined at a predetermined pretilt angle. Can be shielded from viewing (that is, omnidirectional shielding can be performed).

  Therefore, a liquid crystal display device that cannot be viewed from a direction other than a specific direction (substantially normal direction in the liquid crystal display panel) and has excellent performance in terms of privacy protection and security enhancement can be provided.

  In the liquid crystal display device of the present invention, it is preferable that the relationship of 0 ° <θ ≦ 45 ° is satisfied, where θ is the pretilt angle of the liquid crystal molecules in the liquid crystal layer.

  By setting the pretilt angle θ of the liquid crystal molecules in the liquid crystal layer to 0 ° <θ ≦ 45 °, all directions can be shielded more effectively.

  In the liquid crystal display device of the present invention, it is preferable that the relationship of θ≈40 ° is satisfied, where θ is the pretilt angle of the liquid crystal molecules in the liquid crystal layer.

  According to the above configuration, the function of lowering the shielding luminance and increasing the front luminance can be further enhanced.

  In the liquid crystal display device of the present invention, the retardation value Re1 is nλ / 2 (n is an integer of 1 or more), the retardation value Re2 is nλ / 2 (n is an integer of 1 or more), and the retardation value Re3 is nλ (n is an integer of 1 or more) is preferable. According to the above configuration, the viewing angle can be further narrowed in the second viewing angle.

  In the liquid crystal display device of the present invention, the angle formed by the straight line connecting the center of the surface of the viewing angle control panel and the viewpoint to the normal line at the center of the surface of the viewing angle control panel is the polar angle Φ, and Φ = 45 An arbitrary viewpoint satisfying ° is a first viewpoint, and from a line connecting a leg of a perpendicular line dropped from the first viewpoint to a plane including the surface of the viewing angle control panel and a center of the surface of the viewing angle control panel. Is the azimuth angle θ, the viewpoint with θ = 90 ° and Φ = 45 ° is the second viewpoint, the viewpoint with θ = 180 ° and Φ = 45 ° is the third viewpoint, and θ = When the viewpoint of 270 ° and Φ = 45 ° is the fourth viewpoint and the viewpoint from the Φ = 0 ° direction is the fifth viewpoint, the retardation at the fifth viewpoint is the second viewing angle. The value is nλ / 2−λ / 4 to nλ / 2 + λ / 4 (n is an integer of 1 or more), and the first viewpoint, A second viewpoint, the third viewpoint, and (the n 1 or more integer) the retardation value is nλ-λ / 4~nλ + λ / 4 in the fourth aspect may become preferable.

  According to the above configuration, at the second viewing angle, only the fifth viewpoint (viewpoint from the Φ = 0 ° direction) among the five viewpoints can be visually recognized, and the other four The display cannot be visually recognized from the viewpoint. Therefore, visual recognition from the vicinity of the first to fourth viewpoints can be reliably prevented. That is, the accuracy of the narrow viewing angle can be increased.

  In the liquid crystal display device of the present invention, the retardation plate is provided between the first polarizing plate and the liquid crystal layer and between the second polarizing plate and the liquid crystal layer. It is preferable.

  According to the above configuration, the left and right directions and the downward direction of the display panel (the azimuth angle θ shown in FIG. 4 is in the range of 90 ° to 270 °) can be displayed in black at the second viewing angle. Visual recognition from these directions can be prevented more reliably.

  In the liquid crystal display device of the present invention, a plurality of the retardation plates are laminated between at least one of the first polarizing plate and the liquid crystal layer and at least one of the second polarizing plate and the liquid crystal layer. It is preferable that the retardation plates stacked on each other have different refractive indexes.

  According to said structure, the viewing angle control panel which has the above retardation values can be easily comprised using the existing phase difference plate.

  In the liquid crystal display device of the present invention, it is preferable that the polarization transmission axes of the first polarizing plate and the second polarizing plate constituting the viewing angle control panel are orthogonal to each other. In other words, in the viewing angle control panel, it is preferable that the polarization transmission axes of the two polarizing plates arranged opposite to each other with the liquid crystal layer interposed therebetween are arranged to be orthogonal to each other. Here, each polarization transmission axis being orthogonal to each other is used to mean that each polarization transmission axis is substantially orthogonal to each other. Here, the polarization transmission axes being substantially orthogonal to each other means that the range of angles formed by the polarization transmission axes is 80 ° to 100 °.

  According to said structure, the viewing angle switch which has a sufficient difference in a viewing angle range between a 1st viewing angle and a 2nd viewing angle can be performed.

  In the liquid crystal display device of the present invention, it is preferable that the backlight has directivity in the normal direction of the liquid crystal display panel.

  In order to solve the above problems, the viewing angle control panel of the present invention is disposed on at least one of the back surface and the front surface of a display device that displays an image, and the viewing angle of the display device is defined as a first viewing angle, A viewing angle control panel that switches between a second viewing angle within the first viewing angle and narrower than the first viewing angle, wherein the first polarizing plate, the liquid crystal layer, and the second polarizing plate are At least one of the retardation plates is provided in this order, and at least one of the first polarizing plate and the liquid crystal layer and at least one of the second polarizing plate and the liquid crystal layer. The retardation value Re1 of the white display portion when the viewing angle of the display device is the first viewing angle is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ / 4 (n is An integer of 1 or more), and the viewing angle of the display device is the second viewing angle. The retardation value Re2 of the mushroom white display part is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4 (n is an integer of 1 or more), and the viewing angle of the display device is the second viewing angle. The retardation value Re3 of the black display portion at a certain time is characterized by nλ−λ / 4 <Re3 <nλ + λ / 4 (n is an integer of 1 or more).

  According to the above configuration, when the second viewing angle is narrower than the conventional viewing angle control panel, the shielding region is expanded as compared with the conventional viewing angle control panel (that is, the visible viewing angle range is narrower). A liquid crystal display device can be provided.

  Here, the “white display portion” means an area where light can be transmitted and the display can be visually recognized, and the “black display portion” means an area where light is shielded and the display cannot be visually recognized. Therefore, the “white display portion” can be rephrased as a “viewing region”, and the “black display portion” can be restated as a “non-viewing region”. Here, the retardation value is a phase shift between each component of light that has passed through the viewing angle control panel (more specifically, the phase of light traveling in the plane including the slow axis and the fast axis). The phase of light traveling in the plane including

  The viewing angle control panel of the present invention preferably includes an optical compensation film in which discotic liquid crystal is hybrid-aligned as the retardation plate.

  As a retardation plate, an optical compensation film in which discotic liquid crystals are hybrid-aligned is provided. Here, the phase difference plate has a role of compensating for the retardation value so as to obtain a retardation value for displaying white / black when viewed from each angle.

  By providing the optical compensation film having the main refractive index as described above, it is possible to cancel the retardation caused by the liquid crystal molecules of the liquid crystal layer being inclined at a predetermined pretilt angle. Can be shielded from viewing (that is, omnidirectional shielding can be performed).

  Therefore, a viewing angle control panel that is invisible from a direction other than a specific direction (substantially normal direction in a liquid crystal display panel) and has excellent performance in terms of privacy protection and security improvement can be provided. .

  In the viewing angle control panel of the present invention, as the retardation plate, optical compensation having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the x, y, and z directions orthogonal to each other. It is preferable to provide a film.

  As a retardation plate, an optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the x, y, and z directions orthogonal to each other is provided. Here, the phase difference plate has a role of compensating for the retardation value so as to obtain a retardation value for displaying white / black when viewed from each angle.

  By providing the optical compensation film having the main refractive index as described above, it is possible to cancel the retardation caused by the liquid crystal molecules of the liquid crystal layer being inclined at a predetermined pretilt angle. Can be shielded from viewing (that is, omnidirectional shielding can be performed).

  Therefore, a viewing angle control panel that is invisible from a direction other than a specific direction (substantially normal direction in a liquid crystal display panel) and has excellent performance in terms of privacy protection and security improvement can be provided. .

  In the viewing angle control panel of the present invention, it is preferable that the relationship of 0 ° <θ ≦ 45 ° is satisfied, where θ is the pretilt angle of the liquid crystal molecules of the liquid crystal layer.

  By setting the pretilt angle θ of the liquid crystal molecules in the liquid crystal layer to 0 ° <θ ≦ 45 °, all directions can be shielded more effectively.

  In the viewing angle control panel of the present invention, it is preferable to satisfy the relationship of θ≈40 °, where θ is the pretilt angle of the liquid crystal molecules of the liquid crystal layer.

  According to the above configuration, the function of lowering the shielding luminance and increasing the front luminance can be further enhanced.

  In the viewing angle control panel of the present invention, the retardation value Re1 is nλ / 2 (n is an integer of 1 or more), the retardation value Re2 is nλ / 2 (n is an integer of 1 or more), and the retardation value Re3. Is preferably nλ (n is an integer of 1 or more). According to the above configuration, the viewing angle can be further narrowed in the second viewing angle.

  In the viewing angle control panel of the present invention, the angle formed by the straight line connecting the center of the surface of the viewing angle control panel and the viewpoint to the normal line at the center of the surface of the viewing angle control panel is a polar angle Φ, and Φ = An arbitrary viewpoint satisfying 45 ° is defined as a first viewpoint, and a line connecting a leg of a perpendicular line dropped from the first viewpoint to a plane including the surface of the viewing angle control panel and a center of the surface of the viewing angle control panel. Is the azimuth angle θ, the viewpoint with θ = 90 ° and Φ = 45 ° is the second viewpoint, the viewpoint with θ = 180 ° and Φ = 45 ° is the third viewpoint, and θ = 270 ° and Φ = 45 ° viewpoint is the fourth viewpoint, and the viewpoint from the Φ = 0 ° direction is the fifth viewpoint, and at the second viewing angle, The retardation value is nλ / 2−λ / 4 to nλ / 2 + λ / 4 (n is an integer of 1 or more), and the first viewpoint The second viewpoint, the third viewpoint, and (the n 1 or more integer) the retardation value is nλ-λ / 4~nλ + λ / 4 in the fourth aspect may become preferable.

  According to the above configuration, at the second viewing angle, the display can be viewed only from one of the five viewpoints, the fifth viewpoint, and the display can be viewed from the other four viewpoints. Can not do it. Therefore, visual recognition from the vicinity of the first to fourth viewpoints can be reliably prevented. That is, the accuracy of the narrow viewing angle can be increased.

  In the viewing angle control panel of the present invention, the retardation plate is provided between the first polarizing plate and the liquid crystal layer, and between the second polarizing plate and the liquid crystal layer, respectively. It is preferable that

  According to the above configuration, the left and right directions and the downward direction of the display panel (the azimuth angle θ shown in FIG. 4 is in the range of 90 ° to 270 °) can be displayed in black at the second viewing angle. Visual recognition from these directions can be prevented more reliably.

  In the viewing angle control panel of the present invention, at least one of the retardation plates is provided between the first polarizing plate and the liquid crystal layer, and between the second polarizing plate and the liquid crystal layer. Are provided in a stacked manner, and the refractive indexes of the retardation plates stacked on each other are preferably different from each other.

  According to said structure, the viewing angle control panel which has the above retardation values can be easily comprised using the existing phase difference plate.

  In the viewing angle control panel of the present invention, it is preferable that the polarization transmission axes of the first polarizing plate and the second polarizing plate are orthogonal to each other. In other words, in the viewing angle control panel, it is preferable that the polarization transmission axes of the two polarizing plates arranged opposite to each other with the liquid crystal layer interposed therebetween are arranged to be orthogonal to each other. Here, each polarization transmission axis being orthogonal to each other is used to mean that each polarization transmission axis is substantially orthogonal to each other. Here, the polarization transmission axes being substantially orthogonal to each other means that the range of angles formed by the polarization transmission axes is 80 ° to 100 °.

  According to said structure, the viewing angle switch which has a sufficient difference in a viewing angle range between a 1st viewing angle and a 2nd viewing angle can be performed.

  As described above, in the liquid crystal display device of the present invention, the viewing angle control panel includes the first polarizing plate, the liquid crystal layer, and the second polarizing plate in this order, and the first polarizing plate. At least one retardation plate is provided between the liquid crystal layer and at least one of the second polarizing plate and the liquid crystal layer, and the viewing angle of the liquid crystal display panel is as described above. The retardation value Re1 of the white display portion at the first viewing angle is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ / 4 (n is an integer of 1 or more), and the field of view of the liquid crystal display panel The retardation value Re2 of the white display portion when the angle is the second viewing angle is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4 (n is an integer of 1 or more), and the liquid crystal display panel The retardation value of the black display when the viewing angle is the second viewing angle Re3 is nλ−λ / 4 <Re3 <nλ + λ / 4 (n is an integer of 1 or more).

  Further, as described above, the viewing angle control panel of the present invention includes the first polarizing plate, the liquid crystal layer, and the second polarizing plate in this order, and the first polarizing plate and the liquid crystal layer. And at least one of the second polarizing plate and the liquid crystal layer is provided with at least one retardation plate, and the viewing angle of the display device is the first viewing angle. When the retardation value Re1 of the white display portion is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ / 4 (n is an integer of 1 or more), the viewing angle of the display device is the second value. The retardation value Re2 of the white display portion at the viewing angle is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4 (n is an integer of 1 or more), and the viewing angle of the display device is the second angle. The retardation value Re3 of the black display portion when the viewing angle is nλ−λ / 4 <Re3 <nλ + Λ / 4 (n is an integer of 1 or more).

  Therefore, by realizing omnidirectional shielding at a narrow viewing angle, a viewing angle control panel capable of switching between a narrow viewing angle and a wide viewing angle of omnidirectional shielding and a liquid crystal display device including the same can be provided.

  An embodiment of the present invention will be described with reference to the drawings.

[General description of liquid crystal display]
FIG. 2 is a cross-sectional view showing a schematic configuration of the liquid crystal display device 10 according to the embodiment of the present invention.

  As shown in FIG. 2, the liquid crystal display device 10 includes a display liquid crystal panel 1 (“liquid crystal display panel” recited in the claims) as a display panel for displaying an image, and a viewing angle including a liquid crystal cell 21. A control panel 2 and two liquid crystal panels are provided. The display liquid crystal panel 1 is a transmissive type, and a backlight 3 is used as a light source.

  The viewing angle control panel 2 is provided between the backlight 3 and the display liquid crystal panel 1 as shown in FIG.

  The liquid crystal display device 10 performs a switching operation of the liquid crystal in the viewing angle control panel 2, thereby widening the viewing angle in which the image of the display liquid crystal panel 1 can be viewed is wide (see “ 1 viewing angle ”) and a narrow viewing angle (“ second viewing angle ”recited in the claims) in which the viewing angle at which the image of the display liquid crystal panel 1 can be viewed is narrow. The display state can be switched. The narrow viewing angle is particularly preferably used when it is not desired for others to view the image on the display liquid crystal panel 1, and the wide viewing angle is used for other normal use or a plurality of images on the display liquid crystal panel 1. It is preferably used when a person wants to watch at the same time.

  The display liquid crystal panel 1 includes a liquid crystal cell 11 having a liquid crystal sandwiched between a pair of translucent substrates, a liquid crystal panel upper polarizing plate 12 and a liquid crystal panel lower polarizing plate 13 provided on the front and back of the liquid crystal cell 11. ing. The liquid crystal mode and the cell structure of the liquid crystal cell 11 are arbitrary. Further, the drive mode of the display liquid crystal panel 1 is also arbitrary. That is, as the display liquid crystal panel 1, any liquid crystal panel capable of displaying characters, images, or moving images can be used. Therefore, the detailed structure of the display liquid crystal panel 1 is not shown, and the description thereof is also omitted.

  The display liquid crystal panel 1 may be a panel capable of color display or a panel dedicated to monochrome display.

[Configuration and operation of viewing angle control panel]
As shown in FIGS. 3A and 3B, the viewing angle control panel 2 includes a liquid crystal layer (a “liquid crystal layer” described in claims) 21e between a pair of translucent substrates 21a and 21b described later. A liquid crystal cell 21 sandwiching (see FIG. 1), two retardation plates (an upper retardation plate 24 and a lower retardation plate 25) sandwiched between the liquid crystal cells 21, and an upper portion of the upper retardation plate 24, that is, A control panel upper polarizing plate 22 (“first polarizing plate” described in claims) provided on the liquid crystal cell 21 side of the liquid crystal cell 21 and the lower retardation plate 25, that is, the liquid crystal cell 21 And a control panel lower polarizing plate 23 (“second polarizing plate” recited in the claims) provided on the backlight 3 side.

  The liquid crystal layer 21e of the liquid crystal cell 21 of the viewing angle control panel 2 is an ECB (Electrically controlled Birefringence) type. The ECB type liquid crystal alignment modes include homogeneous, homeotropic, hybrid, bend, and spray.

  The viewing angle control panel 2 includes a control panel lower polarizing plate 23, a liquid crystal layer 21e, and a control panel upper polarizing plate 22 in this order, and a lower retardation plate between the control panel lower polarizing plate 23 and the liquid crystal layer 21e. 25, and an upper retardation plate 24 is provided between the liquid crystal layer 21e and the control panel upper polarizing plate 22 (see FIG. 1).

  The upper polarizing plate 22 on the control panel is subjected to a diffusion process such as an AG process on the surface. The lower polarizing plate 23 of the control panel is a so-called clear polarizing plate that is not subjected to surface treatment. The polarizing plate 22 on the control panel is not always necessary and can be omitted. That is, it is sufficient that at least one polarizing plate exists between the viewing angle control panel 2 and the display liquid crystal panel 1, so that the liquid crystal panel lower polarizing plate 13 of the display liquid crystal panel 1 is used as the control panel upper polarizing plate 22. It is possible to share it. In this case, the liquid crystal panel lower polarizing plate 13 corresponds to the polarizing plate of the present invention.

  Next, the configuration and operation of the viewing angle control panel 2 will be described with reference to FIGS. For convenience of explanation, here, as a reference example, a configuration in which the viewing angle control panel 2 is not provided with a retardation plate will be described, and then the retardation plate provided in the viewing angle control panel according to the present embodiment will be described. A more detailed description of the structure will be described.

  FIGS. 3A and 3B are schematic views mainly showing the configuration of the viewing angle control panel 2. FIG. 3A shows the arrangement state of liquid crystal molecules at a narrow viewing angle, and FIG. The alignment state of liquid crystal molecules in

  As shown in FIGS. 3A and 3B, the liquid crystal cell 21 of the viewing angle control panel 2 includes a pair of translucent substrates 21a and 21b. Transparent electrodes 21c and 21g are formed on the respective surfaces of the translucent substrates 21a and 21b by using, for example, ITO (Indium Tin Oxide) (see FIG. 1). The display liquid crystal panel 1 has an electrode structure corresponding to the display unit because it is necessary to drive the liquid crystal in a display unit such as a pixel unit or a segment unit. However, the viewing angle control panel 2 is not limited regarding the electrode structure. For example, in order to perform uniform switching over the entire display surface, the transparent electrodes 21c and 21g may be uniformly formed on the entire surface of the light-transmitting substrates 21a and 21b, or any other electrode structure may be adopted. obtain.

  Alignment films 21d and 21f for aligning liquid crystal molecules 21c are formed on the transparent electrodes 21c and 21g (see FIG. 1). The alignment films 21d and 21f are rubbed by a known method. In FIGS. 3A and 3B, the rubbing direction in each of the translucent substrates 21a and 21b is indicated by arrows Ra and Rb. As shown in FIGS. 3A and 3B, the rubbing direction Ra with respect to the alignment film 21d of the translucent substrate 21a is parallel and opposite to the rubbing direction Rb with respect to the alignment film 21f of the translucent substrate 21b. The rubbing directions Ra and Rb become the direction of the slow axis (nx axis) of the liquid crystal layer.

  That is, the liquid crystal cell 21 is an anti-parallel type cell.

  In the present embodiment, the liquid crystal injected into the liquid crystal cell 21 is a homogeneously aligned liquid crystal. Therefore, the liquid crystal molecules 21c of the liquid crystal cell 21 are arranged so that the molecular long axes are parallel to the substrate surfaces of the translucent substrates 21a and 21b when no voltage is applied. The retardation value d · Δn (d is the thickness of the cell, Δn is the birefringence) of the liquid crystal cell 21 is, for example, 350 nm to 450 nm.

In addition, when a voltage is applied between electrodes (not shown) provided on each of the light-transmitting substrates 21a and 21b, the liquid crystal molecules 21c are in a transparent state as shown in FIG. The direction is gradually changed according to the magnitude of the applied voltage in a plane perpendicular to the normal lines of the light-transmitting substrates 21a and 21b and parallel to the rubbing directions Ra and Rb with respect to the alignment film of the light-transmitting substrate 21a. When the applied voltage reaches a predetermined value, the liquid crystal molecules 21c are arranged in a state where the molecular major axis is substantially perpendicular to the substrate surfaces of the light-transmitting substrates 21a and 21b, as shown in FIG. That is, FIG. 3A shows that the molecular major axis of the liquid crystal molecules 21c is relative to the normal line of the translucent substrates 21a and 21b by the applied voltage V _L (for example, a voltage of about 2.5 V to 3.5 V). Slightly tilted. FIG. 3B shows a state in which the molecular major axis of the liquid crystal molecules 21c is substantially perpendicular to the substrate surfaces of the translucent substrates 21a and 21b by the applied voltage V _H (for example, a voltage of 5.0 V or more). Indicates.

As shown in FIG. 3A, the control panel lower polarizing plate 23 provided below the liquid crystal cell 21 and the control panel upper polarizing plate 22 provided above the liquid crystal cell 21 in the viewing angle control panel 2 are: The respective polarization transmission axes X ₂₃ and the polarization transmission axes X ₂₂ are arranged so as to be substantially orthogonal to each other.

Thus, the polarization transmission axes X ₂₃ and the polarizing transmission axis X ₂₂ is long as it is arranged so as to be substantially perpendicular to each other (i.e., the angle between the polarizing transmission axis X ₂₂ and the polarizing transmission axis X _23, 80 ° ~ If it is in the range of 100 °, a sufficient effect of switching the viewing angle can be obtained. Polarization transmission axis _{X 22} of the control panel upper polarizing plate 22, with respect to the rubbing direction R of the alignment film of the light transmitting substrate 21a, with a slope of 40 ° to 50 ° (preferably 45 °).

[About the principle of switching the viewing angle]
Here, referring to FIGS. 4 and 5 in addition to FIGS. 3A and 3B described above, the viewing angle control panel 2 having the above-described configuration is used to change the viewing angle into a wide viewing angle and a narrow viewing angle. The principle of switching between the two will be described. That is, the viewing angle control panel 2 switches the viewing angle between the wide viewing angle and the narrow viewing angle by switching the voltage applied to the liquid crystal cell 21. In the following description, the viewing angle from a certain viewpoint with respect to the viewing angle control panel 2 is represented by an azimuth angle θ and a polar angle Φ with respect to the center of the upper polarizing plate 22 on the control panel. FIG. 4 shows viewing angles from _three viewpoints P _{1 to} P _{3 with} respect to the viewing angle control panel 2 arranged in the same direction as FIGS.

As shown in FIG. 4, the azimuth angle θ is a rotation angle of a line connecting a leg of a perpendicular line dropped from a viewpoint to a plane including the surface of the control panel upper polarizing plate 22 and a center 22 c of the control panel upper polarizing plate 22. It is. In Figure 4, the azimuth angle theta, the azimuth angle of the direction of the viewpoint P ₁ as 0 °, it is assumed to increase in a clockwise direction when viewed from the normal direction upper side of the control panel on the polarizing plate 22. In Figure 4, the azimuth angle theta ₂ of the viewpoint _{P 2} is 90 °, the azimuth angle theta ₃ of the viewpoint _{P 3} is 180 °. The polar angle Φ is an angle formed by a straight line connecting the center 22c of the polarizing plate 22 on the control panel and the viewpoint with the normal line of the polarizing plate 22 on the control panel.

Here, referring to FIGS. 5A to 5C, the molecular major axis of the liquid crystal molecules 21 c is changed to the light-transmitting substrate 21 a by the voltage _VL applied to the liquid crystal cell 21 as shown in FIG. The display state observed from the respective viewing angles of the viewpoints P _{1 to} P ₃ shown in FIG. 4 when tilted by a slight angle with respect to the normal line 21b will be described.

First, with respect to the viewing angle (azimuth angle θ ₁ = 0 °) from the viewpoint P ₁ shown in FIG. 4, as shown in FIG. 5A, the short axis side of the liquid crystal molecules 21c is opposed to the viewing angle direction. Become. Thus, for the visual angle from the viewpoint P _1, emitted from the backlight 3, linearly polarized light incident on the liquid crystal cell 21 is transmitted through the control panel under the polarizing plate 23, given a birefringence by the liquid crystal molecules 21c Instead, the light is shielded by the polarizing plate 22 on the control panel. Therefore, the viewing angle from the viewpoint P ₁ (azimuth angle θ ₁ = 0 °) is black. When the applied voltage _VL to the liquid crystal cell 21 is about 2.5V to 3.5V as described above, as shown in FIG. 6, the azimuth angle θ ₁ = 0 ° is about 30 for the polar angle Φ. In the range of ° ≦ Φ <90 °, a light-shielding state sufficient to prevent peeping from others can be obtained. Incidentally, in FIG. _6, L 1 ~L ₈ are ^{luminance, 50cd / m 2, 100cd /} m 2, 150cd / m 2, 200cd / m 2, 250cd / m 2, 300cd / m 2, 350cd / m 2 And equipotential lines showing the distribution of viewing angles of 400 cd / m ² .

Further, with respect to the viewing angle (azimuth angle θ ₂ = 90 °) from the viewpoint P ₂ shown in FIG. 4, as shown in FIG. 5B, the molecular major axis of the liquid crystal molecules 21c is the polarizing plate on the control panel. The polarization transmission axis X22 of ₂₂ and the control panel lower polarizing plate 23 are slightly inclined. Thus, for the visual angle from the viewpoint P _2, emitted from the backlight 3, linearly polarized light incident on the liquid crystal cell 21 is transmitted through the control panel under the polarizing plate 23, negligible birefringence by the liquid crystal molecules 21c Although refraction occurs, it is shielded by the upper polarizing plate 22 on the control panel. Accordingly, black is also displayed for the viewing angle from the viewpoint P ₂ (azimuth angle θ ₂ = 90 °). Further, the viewpoint P ₂ position opposite to, that is, by the same principle as when observed from the viewpoint P ₂ may azimuth θ is 270 °, a black display. When the applied voltage _VL to the liquid crystal cell 21 is about 2.5 V to 3.5 V as described above, the azimuth angle θ = 90 ° and the azimuth angle θ = 270 ° are as shown in FIG. In the range of about 30 ° ≦ Φ <90 ° with respect to the angle Φ, a light shielding state sufficient to prevent peeping from others is obtained.

For the viewing angle (azimuth angle θ ₃ = 180 °) from the viewpoint P ₃ shown in FIG. 4, as shown in FIG. 5C, the molecular major axis of the liquid crystal molecules 21c is the polarizing plate on the control panel. about 45 ° inclination with respect to 22 each polarization transmission axis X ₂₃ of the polarizing transmission axis X ₂₂ and the control panel under the polarizing plate 23 of, and a state where the long axis side of the liquid crystal molecules 21c faces the visual angle direction. Thereby, for the viewing angle from the viewpoint P ₃ , the linearly polarized light emitted from the backlight 3 and transmitted through the control panel lower polarizing plate 23 and incident into the liquid crystal cell 21 is birefringent by the liquid crystal molecules 21 c. The polarization direction is rotated so as to coincide with the polarization transmission axis X ₂₂ of the control panel upper polarizing plate 22, and the control panel upper polarizing plate 22 is transmitted. Thus, for the visual angle from the viewpoint P _3, excellent display can be obtained. When the applied voltage _VL is about 2.5V to 3.5V as described above, the azimuth angle θ ₃ = 180 ° is approximately 0 ° ≦ Φ <with respect to the polar angle Φ as shown in FIG. Good display can be obtained in the range of 90 °.

As described above, when the applied voltage _VL for tilting the molecular long axis of the liquid crystal molecules 21c by a slight angle with respect to the substrate normal is applied to the liquid crystal cell 21 of the viewing angle control panel 2, the azimuth angle θ is about 180 °. Good display can be obtained only in a narrow viewing angle range, and for other azimuth angles, the polarized light in the liquid crystal cell 21 is shielded by the lower polarizing plate 13 of the liquid crystal panel, resulting in black display. Therefore, by applying the applied voltage _VL to the liquid crystal cell 21 of the viewing angle control panel 2, the emitted light from the backlight 3 can be shielded in the wide viewing angle direction. That is, the display image of the display liquid crystal panel 1 cannot be viewed from the wide viewing angle direction, and the liquid crystal display device 10 can have a narrow viewing angle.

On the other hand, when an applied voltage V _H that tilts the molecular long axis of the liquid crystal molecules 21c substantially perpendicular to the substrate is applied to the liquid crystal cell 21 of the viewing angle control panel 2 as shown in FIG. As shown in FIG. 7, for any viewing angle of the viewpoints P _{1 to} P ₃ shown, sufficient birefringence is generated so that a good display can be obtained with respect to the omnidirectional angle θ. 10 can be a wide viewing angle. In FIG. 7, L _{1 to} L ₈ have luminance of 130 cd / m ² , 240 cd / m ² , 350 cd / m ² , 460 cd / m ² , 570 cd / m ² , 680 cd / m ² , and 790 cd / m ^2. , And an equipotential line showing the distribution of each viewing angle of 900 cd / m ² .

In the liquid crystal display device 10 of the present embodiment, the voltage applied to the liquid crystal cell 21 of the viewing angle control panel 2 is switched in at least two stages of the applied voltage V _H or the applied voltage _VL , thereby displaying the display of the liquid crystal display device 10. The state can be switched between a wide viewing angle and a narrow viewing angle.

  By the way, from the viewpoint of privacy protection and security improvement, in recent years, in the luminance distribution obtained in the narrow viewing angle mode in the viewing angle control panel not provided with the phase difference plate as shown in FIGS. Narrow viewing angle characteristics are insufficient, and there is an increasing demand for expanding the shielding region in the narrow viewing angle mode.

  Therefore, as shown in FIG. 2, the viewing angle control panel 2 according to the present embodiment includes two retardation plates (an upper retardation plate 24 and a lower retardation plate 25), a liquid crystal cell 21 and a polarizing plate (upper polarization plate). Between the plate 22 and the lower polarizing plate 23). Note that the present invention is not necessarily limited to such a configuration, and there is a phase difference between at least one of the control panel upper polarizing plate 22 and the liquid crystal cell 21 and between the control panel lower polarizing plate 23 and the liquid crystal cell 21. The board should just be provided.

[About the retardation plate]
Here, an optical effect obtained by providing a retardation plate between the polarizing plate and the liquid crystal layer of the viewing angle control panel will be described with reference to FIG. FIG. 8 is a schematic diagram showing a configuration of a viewing angle control panel 2 ′ provided with one retardation plate.

As shown in FIG. 8, the viewing angle control panel 2 ′ further includes a retardation plate 24 a between the translucent substrate 21 a of the liquid crystal cell 21 and the control panel upper polarizing plate 22. When a narrow viewing angle is obtained by applying a voltage _VL to the liquid crystal cell 21, viewing is performed from a viewing angle other than the azimuth angle of 180 ° shown in FIG. 4 (eg, azimuth angle of 0 °, 90 °, 270 °). If linearly polarized light after passing through the exit control panel under the polarizing plate 23 from the backlight 3, the refractive index of the liquid crystal molecules 21c _{(n e,} n _o) by, birefringence occurs in the liquid crystal layer of the liquid crystal cell 21 It becomes elliptically polarized light. Thereby, the component which permeate | transmits the polarizing plate 22 on a control panel arises, and it becomes a cause of light leakage. The phase difference plate 24a is provided for optically compensating the elliptically polarized light. That is, a retardation plate that generates elliptically polarized light that cancels elliptically polarized light generated in the liquid crystal layer of the liquid crystal cell 21 at a narrow viewing angle is used as the retardation plate 24a. As shown in FIG. 8, the three-dimensional refractive index axes N _X , N _Y , and _NZ of the phase difference plate 24a are defined. That, _{N X} is a component perpendicular to the polarizing transmission axis _{X 22} of the control panel upper polarizing plate 22, _{N Y} is a component parallel to the polarizing transmission axis _{X 22} of the control panel upper polarizing plate 22, _{N Z} is a control panel This component is parallel to the normal line of the upper polarizing plate 22.

9 (a) is a refractive index ellipsoid of the liquid crystal molecules 21c of the liquid crystal cell _21, a _n e> n _o. FIG. 9B shows a refractive index ellipsoid of the retardation film 24a, and N _X > N _Z > N _Y. FIG. 9C shows a comparative example, which is a refractive index ellipsoid of a retardation plate (negative A plate film) conventionally used for wide viewing angle of a liquid crystal display device. N _X = N _Z > N _Y.

FIG. 10A shows the polarization transmission axes X ₂₂ and X of the control panel upper polarizing plate 22 and the control panel lower polarizing plate 23 when viewed from the vicinity of the viewpoint P ₂ (azimuth angle θ = 90 °) shown in FIG. ₂₃ is a schematic diagram showing a relationship between the refractive index ellipsoid F _{21 of} the liquid crystal molecules 21c and the refractive index ellipsoid F ₄ of the phase difference plate 24a. Figure 10 (a), _n e of the refractive index ellipsoid _{F 21} of the liquid crystal molecules 21c, the _{n o,} and the component _{n X22} parallel to the polarizing transmission axis _{X 22} of the control panel upper polarizing plate 22, the control panel under the polarizer It is shown decomposed into a component parallel _{n X23} polarization transmission axis _{X 23} of 23. Further, N _X and N _Y of the refractive index ellipsoid F ₄ of the phase difference plate 24 a are changed from the component N _X22 parallel to the polarization transmission axis X ₂₂ of the control panel upper polarizing plate 22 and the polarization transmission of the control panel lower polarizing plate 23. It is shown decomposed into a component _{N X23} parallel to the axis _{X 23.} As can be seen from FIG. 10A, n _X22 and N _X22 are approximately equal in size, and n _X23 and N _X23 are approximately equal in size. Therefore, the phase difference generated in the liquid crystal layer of the liquid crystal cell 21 is offset by the phase difference plate 24a with respect to the viewing angle near the viewpoint P ₂ (azimuth angle θ = 90 °) shown in FIG. 4, and light leakage can be prevented. it can. Even when viewed from a viewing angle near azimuth angle θ = 270 °, light leakage is prevented by the same principle as described above.

10B shows the polarization transmission axis X ₂₂ of the control panel upper polarizing plate 22 and the control panel lower polarizing plate 23 when viewed from the vicinity of the viewpoint P ₁ (azimuth angle θ = 0 °) shown in FIG. , X ₂₃ , the refractive index ellipsoid F _{21 of} the liquid crystal molecules 21 c, and the refractive index ellipsoid F ₄ of the phase difference plate 24 a. As shown in FIG. 10B, when viewed from a viewing angle in the vicinity of the azimuth angle θ = 0 °, there is almost no phase difference, so no light leakage occurs.

  By providing the retardation plate between the polarizing plate and the liquid crystal layer, the narrow viewing angle characteristics in the narrow viewing angle mode can be improved.

[Retardation value]
Furthermore, in the viewing angle control panel 2 of the present invention, the retardation value Re1 of the white display portion in the wide viewing angle mode that is the first viewing angle is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ / 4. The retardation value Re2 of the light passing through the viewing angle control panel at the white display portion in the narrow viewing angle mode as the second viewing angle is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4, and the narrow viewing angle mode The retardation value Re3 of the light passing through the viewing angle control panel in the black display portion at n becomes nλ−λ / 4 <Re3 <nλ + λ / 4. Note that n is an integer of 1 or more (n = 1, 2, 3,...), And each n in Re1, Re2, and Re3 may be the same or different.

  In the present embodiment, the retardation plates 24 and 25 are set so that the retardation values as described above are obtained. Here, the “white display portion” means a portion where light can be transmitted and the display can be visually recognized, and the “black display portion” means a portion where light is shielded and the display cannot be visually recognized. To do. Here, the retardation value means a phase shift between each component of light that has passed through the phase difference plate. Here, the light passing through the viewing angle control panel means light having a wavelength of 380 to 780 μm (visible light region) among the light passing through the viewing angle control panel.

  In order to obtain better narrow viewing angle characteristics, the retardation values Re1, Re2, and Re3 are set to nλ / 2−λ / 8 <Re1 <nλ / 2 + λ / 8 and nλ / 2−λ / 8 <, respectively. It is preferable that Re2 <nλ / 2 + λ / 8 and nλ−λ / 8 <Re3 <nλ + λ / 8, where Re1 is an integral multiple of λ / 2, Re2 is an integral multiple of λ / 2, and Re3 is λ More preferably, it is set so as to be as close as possible to an integer multiple of. It is further preferable that Re1 = nλ / 2, Re2 = nλ / 2, and Re3 = nλ. Here, all n are integers of 1 or more, and each n in Re1, Re2, and Re3 may be the same or different.

  In the present invention, it is preferable to use a combination of a plurality of retardation plates having different refractive indexes. According to this, the viewing angle control panel which has the above retardation values can be comprised using the existing phase difference plate.

[Characteristics of the present invention]
Next, the most important part of the present invention will be described. An object of the present invention is to further devise the retardation plate to realize omnidirectional shielding at a narrow viewing angle. A configuration for realizing this object will be described in detail below.

  In the present embodiment, in particular, a GRP film or a NewGRP film having a main refractive index having the following relationship is used as the retardation plate (upper retardation plate 24 and lower retardation plate 25). Here, the GRP film and the NewGRP film can be rephrased as films in which discotic liquid crystals are hybrid-aligned. The discotic liquid crystal molecule has a disc shape and has a refractive index of nx = nz> ny.

[About the first retardation plate]
FIG. 1 is a diagram showing a more detailed configuration of the viewing angle control panel 2 provided in the liquid crystal display device 10 shown in FIG.

  As shown in FIG. 1, the viewing angle control panel 2 in the present embodiment includes a control panel lower polarizing plate 23, a lower retardation plate 25, a liquid crystal cell 21, an upper retardation plate 24, and a control panel upper polarizing plate 22 in this order. It has a stacked configuration.

  Further, as shown in FIG. 1, as the upper retardation plate 24 and the lower retardation plate 25, negative C plates 33a and 33b, NEW GRP Film (NEW GRP film; "optical compensation film" described in claims) 32a 32b and λ / 4 plates 31a and 31b, and from the side adjacent to the liquid crystal cell 21, negative C plates 33a and 33b, NEW GRP Films 32a and 32b, and λ / 4 plates 31a and 31b are arranged in this order, respectively. have. The refractive indexes of these respective retardation plates are different from each other.

  As shown in FIG. 1, the liquid crystal cell 21 includes, in order from the control panel lower polarizing plate 23 side, a transparent substrate 21a, a transparent electrode 21c using ITO, an alignment film 21d for horizontal alignment, a liquid crystal layer 21e, An alignment film 21f for horizontal alignment, a transparent electrode 21g using ITO, and a glass substrate 21b are arranged.

  Here, each phase difference plate constituting the phase difference plates 24 and 25 will be described. In describing the characteristics of each retardation plate, each retardation plate has a thickness d as shown in FIG. 11A, and three main refractive indexes nx in the x, y, and z axis directions orthogonal to each other. , Ny, nz.

  11B shows a refractive index ellipsoid of NEW GRP Film 32a / 32b, FIG. 11C shows a refractive index ellipsoid of λ / 4 plates 31a / 31b, and FIG. 11D shows a negative ellipsoid. The refractive index ellipsoid of C plate 33a * 33b is shown.

  The NEW GRP Films 32a and 32b have a relationship of nx = nz> ny. The λ / 4 plates 31a and 31b satisfy nx> nz> ny, and the in-plane retardation value given by | nx−ny | · d is λ / 4 [nm] (380 nm <λ <780 nm). It will be. The negative C plates 33a and 33b have a relationship of nx = ny> nz, and the retardation value given by | nx−nz | · d is generally 90 nm to 240 nm.

  Other examples of the retardation plate that can be used in this embodiment include a TAC film and a positive A plate. The TAC film has a relationship of nx = ny> nz, and generally has a retardation value given by | nx−nz | · d of 50 nm to 60 nm. The positive A plate has a relationship of nx> ny = nz. Furthermore, as another phase difference plate, what is described in the nonpatent literature 1 is mentioned, for example.

  In the present embodiment, retardation plates Re1, Re2, Re3 as described above are obtained by combining a plurality of retardation plates used for constituting the retardation plate, and at least one of nx = nz> ny is obtained. There is no particular limitation as long as it has a related optical compensation film (for example, New GRP Film or GRP Film), and various conventionally known retardation plates can be used in appropriate combination. is there. In addition, as an optical compensation film having a relationship of nx = nz> ny, a TAC film or a negative C plate may be used.

  FIG. 12 is a diagram showing an axial configuration of the viewing angle control panel 2 shown in FIG.

  As shown in the figure, the upper polarizing plate absorption axis and the lower polarizing plate absorption axis are substantially orthogonal to each other. Further, the direction of the slow axis (nx axis) of the liquid crystal layer (namely, the anti-parallel rubbing direction), the upper polarizing plate absorption axis and the lower polarizing plate absorption axis form an angle of about 45 °.

  Further, the New GRP Films 32a and 32b provided on the upper phase difference plate 24 and the lower phase difference plate 25 are arranged at positions where the x-axis becomes an azimuth angle of 90 °. That is, the New GRP Films 32a and 32b provided on the upper retardation film 24 and the lower retardation film 25 are arranged in a direction in which the x axis is orthogonal to the slow axis of the liquid crystal layer.

  Further, the λ / 4 plates 31a and 31b provided on the upper retardation plate 24 and the lower retardation plate 25 are arranged at positions where the x-axis is an azimuth angle of 90 °. That is, the λ / 4 plates 31a and 31b provided on the upper retardation plate 24 and the lower retardation plate 25 are arranged in a direction in which the nx axis is orthogonal to the slow axis of the liquid crystal layer. Note that the axial direction here is common to both the upper retardation plate 24 and the lower retardation plate 25. Further, since the negative C plates 33a and 33b have a relationship of nx = ny, the shaft angle can be arbitrarily set.

  Next, the retardation value (Re value) of the wavelength detected at each viewpoint in the narrow viewing angle mode in the liquid crystal display device 10 including the viewing angle control panel 2 having the configuration shown in FIG. 1 will be described.

First, the viewpoints P _{1 to} P _{5 with} respect to the viewing angle control panel 2 will be described with reference to FIG. As shown in FIG. 13, the azimuth angle θ is a rotation angle of a line connecting a leg of a perpendicular line dropped from a viewpoint to a plane including the surface of the control panel upper polarizing plate 22 and a center 22 c of the control panel upper polarizing plate 22. It is. In FIG. 13, the azimuth angle θ increases clockwise when viewed from above the normal direction of the upper polarizing plate 22 on the control panel with the azimuth angle in the direction of the viewpoint P ₁ (first viewpoint) as 0 °. And In FIG. 13, the azimuth angle θ ₂ of the viewpoint P ₂ (second viewpoint) is 90 °, the azimuth angle θ ₃ of the viewpoint P ₃ (third viewpoint) is 180 °, and the viewpoint P ₄ (fourth viewpoint). The azimuth angle θ ₄ is 270 °. The polar angle Φ is an angle that a straight line connecting the center 22c of the polarizing plate 22 on the control panel and the viewpoint forms a normal to the polarizing plate 22 on the control panel. Here, Φ _{1 to} Φ ₄ are all 45 °. To do. The viewpoint P ₅ (fifth viewpoint) is a viewpoint from the upper side in the normal direction of the control panel upper polarizing plate 22.

FIG. 14A is a diagram showing a transmittance distribution at a narrow viewing angle of the liquid crystal display device 10 provided with the viewing angle control panel 2 shown in FIG. In FIG. 14A, T _{1 to} T ₈ have transmittances of 0.04, 0.08, 0.12, 0.16, 0.19, 0.23, 0.27, and 0. .30 is a coordinate line showing the visual distribution of 30. FIG. 14A shows an angle that matches the azimuth angle shown in FIG.

In viewpoint _{P 5,} a value close to the Re value lambda / 2 (i.e., λ / 2-λ / 4~λ / 2 + λ / 4) becomes. In this case, the viewpoint P _5, as also shown in FIG. 14 (a), can view the display becomes "white display portion". At the viewpoints P _{1 to} P ₄ , the Re value is a value close to λ (that is, λ−λ / 4 to λ + λ / 4). In this case, as shown in FIG. 14A, the viewpoints P _{1 to} P ₄ are “black display portions” whose display cannot be visually recognized.

Thus, it shields against the four directions except P _5, thereby enabling all directions shielding.

  The graph (A) in FIG. 15A shows the transmittance characteristic in the left-right direction at a narrow viewing angle when viewed at a certain azimuth angle (for example, 90 °) when the viewing angle control panel 2 shown in FIG. 1 is used. The graph (B) in FIG. 15B shows the azimuth angle (for example, 0 °) when the viewing angle control panel 2 shown in FIG. 1 is used. The transmittance characteristics in the vertical direction at a narrow viewing angle (transmission-polar angle relationship) are shown.

  In each transmittance characteristic, the vertical axis indicates the transmittance, and the horizontal axis indicates the polar angle.

  As can be seen from these transmittance characteristics, the transmittance is high when the polar angle is around 0 °, and the transmittance is lowered as the polar angle goes away from 0 °.

  Further, the graph (C) in FIG. 15 (c) is obtained by changing the vertical axis in the graph (A) in FIG. 15 (a) from 0 to 0.35 to 0 to 0.025. Shows the relationship between transmittance and polar angle. The graph (D) in FIG. 15 (d) is obtained by changing the vertical axis in the graph (B) in FIG. 15 (b) from 0 to 0.35 to 0 to 0.025. It shows the relationship between rate and polar angle. The azimuth angle is the same in FIGS. 15A and 15C, and is the same in FIGS. 15B and 15D.

  From the graph (C) in FIG. 15 (c) and the graph (D) in FIG. 15 (d), it can be seen that if the polar angle is increased to some extent, the transmittance becomes smaller than 0.025 (that is, shielded). .

  On the other hand, in the wide viewing angle mode, liquid crystal molecules are aligned substantially vertically by applying a voltage of, for example, 5.00 V, and almost no retardation is generated in the liquid crystal cell 21. Accordingly, in the wide viewing angle mode, the viewing angle control panel 2 having the configuration shown in FIG. 1 includes only the upper retardation plate 24 and the lower retardation plate 25, and the light that has passed through the viewing angle control panel 2 has a Re value in the entire field of view. Is set to be close to λ / 2.

FIG. 14B is a diagram showing a luminance distribution at a wide viewing angle of the liquid crystal display device provided with the viewing angle control panel shown in FIG. In FIG. 14B, T _{1 to} T ₈ have transmittances of 0.04, 0.08, 0.12, 0.16, 0.19, 0.23, 0.27, and 0. .30 is a coordinate line showing the visual distribution of 30. FIG. 14A shows an angle that matches the azimuth angle shown in FIG.

As shown in FIG. 14B, it can be seen that the entire field of view (that is, all of the viewpoints P _{1 to} P ₅ ) has appropriate luminance, and the display is visible at each viewpoint.

  The retardation value as described above can be set by deciding a region to be shielded and a region to be visually recognized at a narrow viewing angle and simulating an optimal combination of a liquid crystal layer, a retardation plate, and a polarizing plate. .

  The liquid crystal layer has a thickness (cell gap) d of 6.5 μm, and the type of liquid crystal is MS991032 (US019; manufactured by Merck & Co., Inc.) (birefringence index Δn is 0.0615). It is a homogeneous orientation with an angle of 4.5 °. Further, the applied voltage in this case is 2.95 V in the narrow viewing angle mode and 5.00 V in the wide viewing angle mode.

  The graph (I) in FIG. 16A shows the transmittance characteristic (transmission-polar angle relationship) in the left-right direction at a wide viewing angle when viewed at a certain azimuth angle (for example, 90 °). A graph (J) in FIG. 16B shows the transmittance characteristic (transmission-polar angle relationship) in the vertical direction at a wide viewing angle when viewed at a certain azimuth angle (for example, 0 °).

  From these graphs (I) and (J), it can be seen that although the polar angle gradually decreases from 0, it has an appropriate transmittance over the entire visual field and is visible in the entire visual field.

  That is, as described above, an optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the mutually orthogonal x, y, and z directions is provided as the retardation plate. Thus, the retardation caused by the liquid crystal molecules of the liquid crystal layer 21d being inclined at a predetermined pretilt angle can be canceled, and the viewing in a direction other than the substantially normal direction in the liquid crystal display panel can be blocked (that is, Omni-directional shielding is possible).

[About the second retardation plate]
The phase difference plate (the upper phase difference plate 24 and the lower phase difference plate 25) of the present embodiment is not limited to the first phase difference plate described above, and may be the following second phase difference plate. Note that when the second retardation plate is used, the visual recognition region at a narrow viewing angle is narrower than when the first retardation plate is used.

  FIG. 17 is a cross-sectional view showing a more detailed configuration of the viewing angle control panel 2 having a configuration different from that in FIG.

  The viewing angle control panel 2 shown in FIG. 17 is the same as that shown in FIG. 1 except for the configuration of the retardation plate and the configuration of the liquid crystal layer, and thus the description of the configuration other than the retardation plate and the liquid crystal layer is omitted.

  The liquid crystal layer has a different pretilt angle and cell gap from those shown in FIG. The pretilt angle of the liquid crystal layer in FIG. 17 is 40 °, and the cell gap d is 8.0 μm. Other points regarding the liquid crystal layer shown in FIG. 17 are the same as those in FIG.

  Here, it is important that the pretilt angle is 40 °. Such a pretilt angle is set, for example, by polymerizing a polymer precursor in which one alignment film is premixed in a liquid crystal layer as described in Japanese Patent No. 3523376. This can be done by having

  Further, by setting the pretilt angle of the liquid crystal layer to 40 °, the bail view function is further improved (the shielding luminance is reduced, compared to the case where the pretilt angle of the liquid crystal layer is set to 4.5 ° as shown in FIG. 1). Brightness).

  As shown in FIG. 17, each of the phase difference plates (upper phase difference plate 24 and lower phase difference plate 25) includes GRP Film (GRP film; optical compensation film) 36a and 36b, negative C as upper phase difference plate 24 and lower phase difference plate 25. Plates 35a and 35b and λ / 4 plates 34a and 34b are provided. From the side adjacent to the liquid crystal cell 21 (liquid crystal layer), GRP Film 36a and 36b, negative C plates 35a and 35b, and λ / 4 plates 34a and 34b are arranged in this order. Each has an arranged structure.

  The refractive index ellipsoids of the GRP Films 36a and 36b are the same as the refractive index ellipsoids of the NEW GRP Films 32a and 32b shown in FIG.

  Here, the GRP Films 36a and 36b and the New GRP Films 32a and 32b have different discotic liquid crystal tilt angles. That is, the inclination in the hybrid alignment state is different between the two.

  FIG. 18 is a diagram showing an axis configuration of the viewing angle control panel shown in FIG.

  As described above, the upper polarizing plate absorption axis and the lower polarizing plate absorption axis arranged on the control panel upper polarizing plate 22 are substantially orthogonal to each other.

  In addition, the direction of the slow axis of the liquid crystal layer (nx axis) (that is, the antiparallel rubbing direction) and the upper polarizing plate absorption axis form an angle of 42 °, and the direction of the slow axis of the liquid crystal layer (nx axis) And the lower polarizing plate absorption axis form an angle of 48 °.

  The retardation value from each viewpoint can be changed by changing the configuration of the retardation plate (more precisely, changing the configuration of the retardation plate in accordance with the pretilt angle) and shifting the axis.

  Furthermore, the GRP Films 36a and 36b of the upper retardation film 24 and the lower retardation film 25 are arranged at positions where the x-axis is an azimuth angle of 90 °. That is, the GRP Films 36a and 36b of the upper retardation plate 24 and the lower retardation plate 25 are arranged in a direction in which the x axis is orthogonal to the liquid crystal layer slow axis.

  Further, the λ / 4 plates 34a and 34b of the upper phase difference plate 24 and the lower phase difference plate 25 are arranged at positions where the x axis is an azimuth angle of 90 °. That is, the λ / 4 plates 34a and 34b of the upper retardation plate 24 and the lower retardation plate 25 are arranged in a direction in which the x-axis is orthogonal to the liquid crystal layer slow layer axis.

FIG. 19A shows a transmittance distribution at a narrow viewing angle of the liquid crystal display device provided with the viewing angle control panel shown in FIG. In FIG. 19A, T _{1 to} T ₈ have transmittances of 0.04, 0.08, 0.12, 0.16, 0.19, 0.23, 0.27, and 0. .30 is a coordinate line showing the visual distribution of 30. FIG. 19A shows an angle that matches the azimuth angle shown in FIG.

In viewpoint _{P 5,} a value close to the Re value lambda / 2 (i.e., λ / 2-λ / 4~λ / 2 + λ / 4) becomes. In this case, the viewpoint P _5, as also shown in FIG. 19 (a), can view the display becomes "white display portion". At the viewpoints P _{1 to} P ₄ , the Re value is a value close to λ (that is, λ−λ / 4 to λ + λ / 4). In this case, as shown in FIG. 14A, the viewpoints P _{1 to} P ₄ are “black display portions” whose display cannot be visually recognized.

Thus, it shields against the four directions except P _5, thereby enabling all directions shielding.

  The graph (E) in FIG. 15A shows the transmittance characteristic in the left-right direction at a narrow viewing angle when viewed at a certain azimuth angle (for example, 90 °) when the viewing angle control panel 2 shown in FIG. 17 is used. The graph (F) in FIG. 15B shows the azimuth angle (for example, 0 °) when the viewing angle control panel 2 shown in FIG. 17 is used. The transmittance characteristics in the vertical direction at a narrow viewing angle (transmission-polar angle relationship) are shown.

  In each transmittance characteristic, the vertical axis indicates the transmittance, and the horizontal axis indicates the polar angle.

  As can be seen from these transmittance characteristics, the transmittance is high when the polar angle is around 0 °, and the transmittance is lowered as the polar angle goes away from 0 °.

  Furthermore, the graph (G) in FIG. 15 (c) is obtained by changing the vertical axis in the graph (E) in FIG. 15 (a) from 0 to 0.35 to 0 to 0.025. Shows the relationship between transmittance and polar angle. The graph (H) in FIG. 15 (d) is obtained by changing the vertical axis in the graph (F) in FIG. 15 (b) from 0 to 0.35 to 0 to 0.025. It shows the relationship between rate and polar angle. The azimuth angle is the same in FIGS. 15A and 15C, and is the same in FIGS. 15B and 15D.

  From the graph (G) in FIG. 15 (c) and the graph (H) in FIG. 15 (d), it can be seen that if the polar angle is increased to some extent, the transmittance is smaller than 0.025 (that is, shielded). .

  On the other hand, in the wide viewing angle mode, the liquid crystal molecules are arranged substantially vertically by applying a voltage of 5.00 V, and almost no retardation occurs in the liquid crystal cell 21. Accordingly, in the wide viewing angle mode, the viewing angle control panel 2 having the configuration shown in FIG. 17 includes only the upper retardation plate 24 and the lower retardation plate 25, and the light passing through the viewing angle control panel 2 has a Re value in the entire field of view. Is set to be close to λ / 2.

FIG. 19B shows a luminance distribution at a wide viewing angle of the liquid crystal display device provided with the viewing angle control panel shown in FIG. In FIG. 19B, T _{1 to} T ₈ have transmittances of 0.04, 0.08, 0.12, 0.16, 0.19, 0.23, 0.27, and 0. .30 is a coordinate line showing the visual distribution of 30. FIG. 19A shows an angle that matches the azimuth angle shown in FIG.
As shown in FIG. 14B, it can be seen that the entire field of view (that is, all of the viewpoints P _{1 to} P ₅ ) has appropriate luminance, and the display is visible at each viewpoint.

  The retardation value as described above can be set by deciding a region to be shielded and a region to be visually recognized at a narrow viewing angle and simulating an optimal combination of a liquid crystal layer, a retardation plate, and a polarizing plate. .

  The graph (K) in FIG. 16A shows the transmittance characteristic (transmission-polar angle relationship) in the left-right direction at a wide viewing angle when viewed at a certain azimuth angle (for example, 90 °). A graph (L) in FIG. 16B shows the transmittance characteristic (transmission-polar angle relationship) in the vertical direction at a wide viewing angle when viewed at a certain azimuth angle (for example, 0 °).

  From these graphs (K) and (L), it can be seen that although the polar angle gradually decreases from 0, it has an appropriate transmittance over the entire visual field and is visible in the entire visual field.

  The configuration of the phase difference plate (the upper phase difference plate 24 and the lower phase difference plate 25) is not limited to the first phase difference plate or the second phase difference plate, but may be the one shown in FIG.

  That is, as shown in FIG. 20, the phase difference plates (upper phase difference plate 24 and lower phase difference plate 25) are arranged from the liquid crystal cell 21 side to TAC Film 39a / 39b, New GRP Film 38a / 38b, and λ / 4 plate 37a / 37b. Are provided in this order.

  Further, as shown in FIG. 21, the axis configuration of the viewing angle control panel shown in FIG. 20 is further parallel to the axis configuration shown in FIG. 12 with the x axis (or y axis) of the lower TAC Film 39b and the lower polarizing plate absorption axis. And the x-axis (or y-axis) of the upper TAC Film 39a is parallel. Here, TAC Film 39a and 39b have a relationship of nx = ny> nz, and the retardation value given by | nx−nz | · d is generally 50 nm to 60 nm.

  22 is a diagram showing a transmittance distribution at a narrow viewing angle (applied voltage is 2.9 V as an example), and FIG. 23 is a graph at a wide viewing angle (applied voltage is 5.0 V as an example). It is a figure which shows the transmittance | permeability distribution. 22 and FIG. 23 show an angle that matches the azimuth angle shown in FIG.

  Moreover, it is preferable that the backlight 3 of this Embodiment has the directivity to the normal line direction of the liquid crystal display panel 1 (viewing angle control panel 2). Thereby, the omnidirectional shielding function can be further enhanced.

In each of the above configuration examples, a retardation plate (an upper retardation plate 24 and a lower retardation plate) is disposed between the liquid crystal layer 21 and two polarizing plates (the upper polarizing plate 22 on the control panel and the lower polarizing plate 23 on the control panel). Each of the plates 25) is provided, but the present invention is not necessarily limited to such a configuration, and only one of the retardation plates may be used. However, in order to realize a state diagram in which a sufficient shielding effect is obtained at the viewpoints P ₁ , P ₂ , P ₃ , and P ₄ shown in FIG. It is preferable that the phase difference plate is provided between the liquid crystal layer and the two polarizing plates, respectively.

  As shown in FIG. 1, the above-described liquid crystal display device 10 includes a viewing angle control panel 2 provided on the lower side of the display liquid crystal panel 1, but the present invention is not necessarily limited thereto. Instead, the stacking order of the display liquid crystal panel 1 and the viewing angle control panel 2 may be reversed. That is, for example, as shown in FIG. 24, a configuration like a liquid crystal display device 10a in which the display liquid crystal panel 1 is laminated on the backlight 3 and the viewing angle control panel 2 is further laminated thereon is also possible. Is possible. In this case, the display liquid crystal panel 1 may be a transflective liquid crystal panel.

  The present invention can be applied to a liquid crystal display device including a backlight, a display panel, and a viewing angle control panel for controlling the viewing angle of the display panel. If the liquid crystal display device of the present invention is used, the shielding effect at a narrow viewing angle can be increased, so that the liquid crystal display device can be applied to a display device considering privacy protection and security enhancement.

It is sectional drawing which shows the structure of the viewing angle control panel in this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a liquid crystal display device according to an embodiment of the present invention, and is a cross-sectional view illustrating a configuration of a liquid crystal display device including a viewing angle control panel. (A) is a perspective view showing an arrangement state of liquid crystal molecules when the viewing angle control panel is at a narrow viewing angle, and (b) is a perspective view showing an arrangement state of liquid crystal molecules when the viewing angle control panel is at a wide viewing angle. FIG. FIG. 4 is a schematic diagram illustrating definitions of viewing angles and explaining each viewpoint with respect to a viewing angle control panel arranged in the same direction as FIGS. (A) (b) (c) is a figure which shows the positional relationship of the liquid crystal molecule according to a viewing angle, and the polarization transmission axis of a polarizing plate. It is a chart which shows the luminance distribution at the time of a narrow viewing angle of a liquid crystal display device when the retardation plate is not provided in the viewing angle control panel. It is a chart which shows the luminance distribution at the time of the wide viewing angle of a liquid crystal display device when the retardation plate is not provided in the viewing angle control panel. It is a schematic diagram which shows a structure in case a viewing angle control panel has one phase difference plate. (A) shows the refractive index ellipsoid of the liquid crystal molecules of the viewing angle control panel shown in FIG. 8, and (b) shows the refractive index ellipsoid of the retardation plate provided in the viewing angle control panel shown in FIG. (C) is a schematic diagram showing a refractive index ellipsoid of a retardation plate conventionally used for widening the viewing angle of a liquid crystal display device as a comparative example. In the viewing angle control panel shown in FIG. 8, it is a schematic diagram showing the relationship between the polarization transmission axis, the refractive index ellipsoid of the liquid crystal molecules, and the refractive index ellipsoid of the phase difference plate, and (a) is an azimuth angle of 90 °. The viewing angle from the vicinity, (b) is the viewing angle from the vicinity of 0 ° azimuth. (A) shows a schematic diagram of a retardation plate, (b) shows a refractive index ellipsoid of a NEZ plate constituting the retardation plate of the viewing angle control panel, and (c) shows a viewing angle control panel. The refractive index ellipsoid of the λ / 4 plate constituting the retardation plate is shown, and (d) shows the refractive index ellipsoid of the negative C plate constituting the retardation plate of the viewing angle control panel. It is a figure which shows the axial structure of the viewing angle control panel shown in FIG. FIG. 3 is a schematic diagram illustrating the definition of the viewing angle and explaining each viewpoint with respect to the viewing angle control panel arranged in the same direction as FIGS. (A) is a figure which shows the transmittance | permeability distribution at the time of a narrow viewing angle of the liquid crystal display device provided with the viewing angle control panel shown in FIG. 1, (b) is equipped with the viewing angle control panel shown in FIG. It is a figure which shows the luminance distribution at the time of a wide viewing angle of the obtained liquid crystal display device. (A)-(d) shows this Embodiment, (a) is an azimuth angle when using the viewing angle control panel shown in FIG. 1 and the viewing angle control panel shown in FIG. FIG. 6 shows transmittance characteristics in the left-right direction at a narrow viewing angle when viewed, and FIG. 5B shows an azimuth angle when the viewing angle control panel shown in FIG. 1 and the viewing angle control panel shown in FIG. 17 are used. (C) shows the transmittance characteristic in the up and down direction at a narrow viewing angle as viewed in (c), and shows the transmittance characteristic on a micro scale than (a), (d) shows (b) ), The transmittance characteristics are shown more microscopically than the above. (A) and (b) show this embodiment, and (a) shows an azimuth angle when the viewing angle control panel shown in FIG. 1 and the viewing angle control panel shown in FIG. 17 are used. FIG. 5B shows the transmissivity characteristics in the left-right direction at a wide viewing angle, and (b) shows an azimuth angle when the viewing angle control panel shown in FIG. 1 and the viewing angle control panel shown in FIG. 17 are used. The transmittance characteristics in the vertical direction at a wide viewing angle when viewed are shown. FIG. 2 is a cross-sectional view showing a detailed configuration of a viewing angle control panel 2 having a configuration different from that of FIG. 1, showing the viewing angle control panel of the present embodiment. It is a figure shown about the axis | shaft structure of the viewing angle control panel shown in FIG. (A) is a figure which shows the transmittance | permeability distribution at the time of a narrow viewing angle of the liquid crystal display device provided with the viewing angle control panel shown in FIG. 17, (b) is equipped with the viewing angle control panel shown in FIG. It is a figure which shows the luminance distribution at the time of a wide viewing angle of the obtained liquid crystal display device. FIG. 18 shows a viewing angle control panel according to the present embodiment, and is a cross-sectional view showing a detailed configuration of a viewing angle control panel 2 having a configuration different from that of FIGS. 1 and 17. It is a figure shown about the axis | shaft structure of the viewing angle control panel shown in FIG. It is a figure which shows the transmittance | permeability distribution at the time of a narrow viewing angle of the viewing angle control panel shown in FIG. 20 (applied voltage is 2.9 V as an example). It is a figure which shows the transmittance | permeability distribution at the time of the wide viewing angle of the viewing angle control panel shown in FIG. 20 (applied voltage is 5.0 V as an example). FIG. 9 is a cross-sectional view illustrating a modification of the liquid crystal display device illustrated in FIG. 2 and illustrating a configuration of a liquid crystal display device including a display liquid crystal panel on the upper side of the viewing angle control panel. It is a chart which shows the viewing angle distribution of the liquid crystal display device provided with the conventional viewing angle control panel.

Explanation of symbols

1. LCD panel for display (LCD panel)
2 Viewing Angle Control Panel 2a Viewing Angle Control Panel 2b Viewing Angle Control Panel 2c Viewing Angle Control Panel 3 Backlight 10 Liquid Crystal Display Device 10a Liquid Crystal Display Device 11 Liquid Crystal Cell 12 Liquid Crystal Panel Upper Polarizer 13 Liquid Crystal Panel Lower Polarizer 21e Liquid Crystal Layer 22 Polarizing plate on control panel (first polarizing plate)
23 Control panel lower polarizing plate (second polarizing plate)
24 Upper retardation plate (retardation plate)
25 Lower retardation plate (retardation plate)
31a λ / 4 plate (retardation plate)
31b λ / 4 plate (retardation plate)
32a NEW GRP Film (retardation plate; optical compensation film)
32b NEW GRP Film (retardation plate; optical compensation film)
33a Negative C plate (retardation plate)
33b Negative C plate (retardation plate)
34a λ / 4 plate (retardation plate)
34b λ / 4 plate (retardation plate)
35a Negative C plate (retardation plate)
35b Negative C plate (retardation plate)
36a GRP Film (retardation plate; optical compensation film)
36b GRP Film (retardation plate; optical compensation film)
37a λ / 4 plate (retardation plate)
37b λ / 4 plate (retardation plate)
38a NEW GRP Film (retardation plate; optical compensation film)
38b NEW GRP Film (retardation plate; optical compensation film)
39a TAC Film (retardation plate)
39b TAC Film (retardation plate)
X ₂₂ polarization transmission axis X ₂₃ polarization transmission axis

Claims (21)

A backlight, a liquid crystal display panel, and a viewing angle of the liquid crystal display panel are set between a first viewing angle and a second viewing angle that is within the first viewing angle and is narrower than the first viewing angle. In a liquid crystal display device equipped with a viewing angle control panel that is switched with
The viewing angle control panel is provided with a first polarizing plate, a liquid crystal layer, and a second polarizing plate in this order,
At least one retardation plate is provided between at least one of the first polarizing plate and the liquid crystal layer and between the second polarizing plate and the liquid crystal layer.
The retardation value Re1 of the white display portion when the viewing angle of the liquid crystal display panel is the first viewing angle is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ / 4 (n is an integer of 1 or more). And
When the viewing angle of the liquid crystal display panel is the second viewing angle, the retardation value Re2 of the white display portion is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4 (n is an integer of 1 or more). Yes,
The retardation value Re3 of the black display portion when the viewing angle of the liquid crystal display panel is the second viewing angle is nλ−λ / 4 <Re3 <nλ + λ / 4 (n is an integer of 1 or more). A liquid crystal display device.   The liquid crystal display device according to claim 1, further comprising an optical compensation film in which discotic liquid crystal is hybrid-aligned as the retardation plate.   An optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the x, y, and z directions orthogonal to each other as the retardation plate is provided. Item 2. A liquid crystal display device according to item 1. When the pretilt angle of the liquid crystal molecules of the liquid crystal layer is θ,
The liquid crystal display device according to claim 1, wherein a relationship of 0 ° <θ ≦ 45 ° is satisfied. When the pretilt angle of the liquid crystal molecules of the liquid crystal layer is θ,
The liquid crystal display device according to any one of claims 1 to 3, wherein a relationship of θ≈40 ° is satisfied.   The retardation value Re1 is nλ / 2 (n is an integer of 1 or more), the retardation value Re2 is nλ / 2 (n is an integer of 1 or more), and the retardation value Re3 is nλ (n is an integer of 1 or more). The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided. The angle formed by the straight line connecting the center of the surface of the viewing angle control panel and the viewpoint to the normal line at the center of the surface of the viewing angle control panel is the polar angle Φ, and any viewpoint that satisfies Φ = 45 ° The rotation angle from the line connecting the leg of the perpendicular line from the first viewpoint to the plane including the surface of the viewing angle control panel and the center of the surface of the viewing angle control panel is defined as the azimuth angle θ. sometimes,
The viewpoint with θ = 90 ° and Φ = 45 ° is the second viewpoint, the viewpoint with θ = 180 ° and Φ = 45 ° is the third viewpoint, and the viewpoint with θ = 270 ° and Φ = 45 ° is the fourth viewpoint. If the viewpoint from Φ = 0 ° direction is the fifth viewpoint,
At the second viewing angle, the retardation value at the fifth viewpoint is nλ / 2−λ / 4 to nλ / 2 + λ / 4 (n is an integer of 1 or more), and the first viewpoint, The retardation values at the second viewpoint, the third viewpoint, and the fourth viewpoint are nλ−λ / 4 to nλ + λ / 4 (n is an integer of 1 or more). 4. The liquid crystal display device according to any one of items 3 to 3.   2. The retardation plate is provided between the first polarizing plate and the liquid crystal layer, and between the second polarizing plate and the liquid crystal layer, respectively. 4. The liquid crystal display device according to any one of items 1 to 3.   A plurality of the retardation plates are provided between at least one of the first polarizing plate and the liquid crystal layer and between the second polarizing plate and the liquid crystal layer. 4. The liquid crystal display device according to claim 1, wherein refractive indexes of the laminated retardation plates are different from each other. 5.   4. The polarization transmission axis of each of the first polarizing plate and the second polarizing plate constituting the viewing angle control panel is orthogonal to each other. 5. Liquid crystal display device.   4. The liquid crystal display device according to claim 1, wherein the backlight has directivity in a normal direction of the liquid crystal display panel. 5. Arranged on at least one of the back and front of the display device for displaying an image, the display device has a first viewing angle and a first viewing angle that is within the first viewing angle and is narrower than the first viewing angle. A viewing angle control panel that switches between two viewing angles,
While the first polarizing plate, the liquid crystal layer, and the second polarizing plate are provided in this order,
At least one retardation plate is provided between at least one of the first polarizing plate and the liquid crystal layer and between the second polarizing plate and the liquid crystal layer.
The retardation value Re1 of the white display portion when the viewing angle of the display device is the first viewing angle is nλ / 2−λ / 4 <Re1 <nλ / 2 + λ / 4 (n is an integer of 1 or more). Yes,
The retardation value Re2 of the white display portion when the viewing angle of the display device is the second viewing angle is nλ / 2−λ / 4 <Re2 <nλ / 2 + λ / 4 (n is an integer of 1 or more). ,
The retardation value Re3 of the black display portion when the viewing angle of the display device is the second viewing angle is nλ−λ / 4 <Re3 <nλ + λ / 4 (n is an integer of 1 or more). Viewing angle control panel.   13. The viewing angle control panel according to claim 12, wherein the retardation plate includes an optical compensation film in which discotic liquid crystals are hybrid-aligned.   An optical compensation film having three main refractive indexes nx, ny, and nz having a relationship of nx = nz> ny in the x, y, and z directions orthogonal to each other as the retardation plate is provided. Item 13. A viewing angle control panel according to Item 12. When the pretilt angle of the liquid crystal molecules of the liquid crystal layer is θ,
The viewing angle control panel according to claim 12, wherein a relationship of 0 ° <θ ≦ 45 ° is satisfied. When the pretilt angle of the liquid crystal molecules of the liquid crystal layer is θ,
The viewing angle control panel according to any one of claims 12 to 14, wherein a relation of θ≈40 ° is satisfied.   The retardation value Re1 is nλ / 2 (n is an integer of 1 or more), the retardation value Re2 is nλ / 2 (n is an integer of 1 or more), and the retardation value Re3 is nλ (n is an integer of 1 or more). The viewing angle control panel according to claim 12, wherein the viewing angle control panel is provided. The angle formed by the straight line connecting the center of the surface of the viewing angle control panel and the viewpoint to the normal line at the center of the surface of the viewing angle control panel is the polar angle Φ, and any viewpoint that satisfies Φ = 45 ° The rotation angle from the line connecting the leg of the perpendicular line from the first viewpoint to the plane including the surface of the viewing angle control panel and the center of the surface of the viewing angle control panel is defined as the azimuth angle θ. sometimes,
The viewpoint with θ = 90 ° and Φ = 45 ° is the second viewpoint, the viewpoint with θ = 180 ° and Φ = 45 ° is the third viewpoint, and the viewpoint with θ = 270 ° and Φ = 45 ° is the fourth viewpoint. If the viewpoint from Φ = 0 ° direction is the fifth viewpoint,
At the second viewing angle, the retardation value at the fifth viewpoint is nλ / 2−λ / 4 to nλ / 2 + λ / 4 (n is an integer of 1 or more), and the first viewpoint, The retardation values at the second viewpoint, the third viewpoint, and the fourth viewpoint are nλ−λ / 4 to nλ + λ / 4 (n is an integer of 1 or more). The viewing angle control panel according to any one of 14 to 14.   13. The retardation plate is provided between the first polarizing plate and the liquid crystal layer, and between the second polarizing plate and the liquid crystal layer, respectively. 15. The viewing angle control panel according to any one of items 1 to 14.   A plurality of the retardation plates are provided between at least one of the first polarizing plate and the liquid crystal layer and between the second polarizing plate and the liquid crystal layer. The viewing angle control panel according to any one of claims 12 to 14, wherein the refractive indexes of the laminated retardation plates are different from each other.   The viewing angle control panel according to any one of claims 12 to 14, wherein the polarization transmission axes of the first polarizing plate and the second polarizing plate are orthogonal to each other.

Images