JP2008064790A - Display, and viewing angle controller used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display which is adaptable to various usage environments and uses by switching a display states between a wide viewing angle and a narrow viewing angle. <P>SOLUTION: The display is provided with a liquid crystal panel for controlling the viewing angle on at least one side of a rear surface and a front surface of a display device. The liquid crystal panel for controlling the viewing angle is provided with: a liquid crystal layer 213 which is bend aligned between alignment layers 211a and 211b each provided on a pair of light transmissible substrates; and a driving circuit applying voltage to the liquid crystal layer 213. The liquid crystal layer 213 is disposed between two polarizing plates 13 and 22 which are so disposed that polarization absorption axes X<SB>13</SB>and X<SB>22</SB>thereof are nearly orthogonal to each other. The driving circuit switches the display state between the wide viewing angle and the narrow viewing angle by changing the alignment state of liquid crystal molecules 213m of the liquid crystal layer 213. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a viewing angle control device capable of switching a viewing angle of a display between a wide viewing angle and a narrow viewing angle, and a display using the viewing angle control device.

  A display is generally 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 displays that have been widely used recently have been developed with respect to wide 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, notebook personal computers, personal digital assistants (PDAs), mobile phones, and the like are highly likely to be used in places where an unspecified number of people can exist, such as in trains and airplanes. In such a use environment, it is desirable that the viewing angle of the display is narrow because it is not desirable to look into the display content 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 between a wide viewing angle and a narrow viewing angle depending on the usage situation. This requirement is not limited to a liquid crystal display, but is a common problem for any display.

  In response to such demands, there is a technology that includes a phase difference control device in addition to a display device that displays an image, and changes the viewing angle characteristics by controlling the voltage applied to the phase difference control device. It has been proposed (for example, Patent Document 1 below). Patent Document 1 exemplifies chiral nematic liquid crystal, homogeneous liquid crystal, random alignment nematic liquid crystal, and the like as a liquid crystal mode used in a liquid crystal display device for phase difference control.

In addition, a viewing angle control liquid crystal panel is provided above the display liquid crystal panel, and these panels are sandwiched between two polarizing plates, and the applied voltage to the viewing angle control liquid crystal panel is adjusted to control the viewing angle. The structure which performs this is also disclosed conventionally (for example, Patent Documents 2 and 3). In Patent Document 2, the liquid crystal mode of the viewing angle control liquid crystal panel is a twisted nematic system. Patent Document 3 discloses a configuration in which a viewing angle control liquid crystal panel is provided between two polarizing plates having parallel transmission axes.
Patent No. 3322197 JP-A-10-268251 JP 2005-316470 A

  In Patent Document 1 described above, it is possible to switch between a wide viewing angle and a narrow viewing angle by using a liquid crystal element for phase difference control, but the effect is not sufficient. For example, FIG. 4 of Patent Document 1 shows an iso-contrast curve having a contrast ratio of 10: 1, and the contrast in the wide viewing angle direction is certainly lowered at a narrow viewing angle. However, with such a change, the display is sufficiently visually recognized by the person next to it. In general, even if the contrast ratio is reduced to 2: 1, the display can be sufficiently visually recognized.

  The technique of Patent Document 2 also switches between a wide viewing angle and a narrow viewing angle by adjusting the contrast by changing the voltage applied to the viewing angle control liquid crystal panel, and the effect is sufficient. It can not be said.

  That is, both techniques of Patent Documents 1 and 2 employ a method of switching between a wide viewing angle and a narrow viewing angle by reducing the contrast in the wide viewing angle direction. However, there is a problem that when the viewing angle is narrow, the shielding in the wide viewing angle direction is not sufficient, and an image may be seen from others.

  Therefore, the present invention has been made to solve the above-described problem, and a display that can be adapted to various usage environments and applications by switching between a wide viewing angle and a narrow viewing angle, and to be used in the display. An object of the present invention is to provide a viewing angle control device.

  In order to achieve the above object, a display according to the present invention is disposed on a display device driven according to an image to be displayed and at least one of a back surface and a front surface of the display device, and a viewing angle of the display device. A viewing angle control device that controls a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are bend-aligned between a pair of translucent substrates; and A driving circuit for applying a voltage, and the liquid crystal cell is disposed between two polarizing plates disposed so that polarization transmission axes are substantially orthogonal to each other in the display, and the viewing angle control device and the two sheets A retardation film is provided at least at one position between the polarizing plate and the drive circuit changes the alignment state of the liquid crystal molecules of the liquid crystal layer of the viewing angle control device, thereby changing the display state to the first view. Switchable between a first state providing an angular range and a second state providing a second viewing angle range within the first viewing angle range and narrower than the first viewing angle range. It is characterized by that.

  In the above configuration, two polarizing plates whose polarization transmission axes are substantially orthogonal are arranged so as to sandwich the viewing angle control device. Note that the viewing angle control device and the two polarizing plates are not necessarily adjacent to each other, and some component may be interposed between them. In the above configuration, the polarization state of the light emitted from the liquid crystal cell of the viewing angle control device is changed by applying a predetermined voltage to the liquid crystal layer to change the alignment state of the liquid crystal molecules and utilizing the birefringence of the liquid crystal. Then, the polarizing plate arranged on the viewer side of the viewing angle control device acts as an analyzer, and the light emitted from the viewing angle control device to the viewer side can be transmitted or shielded depending on the viewing angle. it can. In addition, a retardation film fulfill | performs the function which compensates the retardation value which arises by birefringence in a liquid crystal cell between two polarizing plates. That is, the display state is the first state (wide viewing angle) that provides the first viewing angle range and the second viewing angle range that is within the first viewing angle range and is narrower than the first viewing angle range. Can be switched to one of the second states (narrow viewing angle). “Wide viewing angle” and “narrow viewing angle” do not mean a specific absolute angle range, but rather a relatively wide viewing angle and a relatively narrow viewing angle. In the above configuration, by using a liquid crystal cell in which liquid crystal molecules are bend-aligned, it is possible to realize a narrow viewing angle state in which display can be visually recognized only in a limited viewing angle. This makes it possible to control the viewing angle by switching between transmission and shielding of light, rather than reducing the contrast of display on the wide viewing angle side as in the conventional viewing angle control technique. As a result, it is possible to provide a display that can be adapted to various usage environments and applications.

  In the display according to the present invention, the liquid crystal layer of the viewing angle control device includes a positive nematic liquid crystal, and the driving circuit applies the first voltage to the liquid crystal layer, whereby the first viewing angle range is obtained. It is preferable that the second viewing angle range is provided by applying a second voltage higher than the first voltage to the liquid crystal layer.

  In the display according to the present invention, rubbing treatment may be performed in parallel and in the same direction with respect to the alignment films respectively included in the pair of translucent substrates of the liquid crystal cell.

  In the display according to the present invention, it is preferable that the two polarizing plates are arranged so that their polarization transmission axes intersect within a range of 80 ° to 100 °.

  In the display according to the present invention, it is preferable that the display device is a display device that emits linearly polarized light, and one of the two polarizing plates is a polarizing plate provided in the display device. For example, the display device may be a transmissive liquid crystal display device and may further include a backlight. In this case, the viewing angle control device may be disposed between the backlight and the transmissive liquid crystal display device, or may be disposed on the front surface of the transmissive liquid crystal display device. Moreover, it is preferable that the said backlight is a directional backlight which has directivity in a normal line direction.

  In the display according to the present invention, the display device is preferably a reflective liquid crystal display device or a transflective liquid crystal display device. Alternatively, the display device is a self-luminous display device, and one of the two polarizing plates is configured between the self-luminous display device and the viewing angle control device. May be.

  In the display according to the present invention, the polarizing transmission axis of the polarizing plate is arranged so as to intersect with the alignment axis of the liquid crystal molecules viewed from the normal direction of the viewing angle control device in a range of 40 ° to 50 °. It is preferable.

  In order to achieve the above object, the first viewing angle control device according to the present invention is disposed on at least one of the back surface and the front surface of the display device that is driven according to an image to be displayed and emits linearly polarized light. A viewing angle control device used for controlling a viewing angle of the display device, the liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are bend-aligned between a pair of translucent substrates, and a voltage applied to the liquid crystal layer A polarizing plate having a polarization transmission axis substantially orthogonal to the plane of polarization of the linearly polarized light, the driving circuit for applying the linearly polarized light from the display device in the liquid crystal cell, and the visual field A retardation film provided in at least one place between the angle control device and the two polarizing plates, and the drive circuit changes the alignment state of the liquid crystal molecules in the liquid crystal layer, Output range And a first viewing angle range, characterized in that it can be switched between a first narrower second viewing angle range than the viewing angle range in a first viewing angle range.

  In order to achieve the above object, a second viewing angle control device according to the present invention is disposed in front of a self-luminous display device driven in accordance with an image to be displayed, and the self-luminous display device. A viewing angle control device used for controlling a viewing angle of a device, which includes a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are bend-aligned between a pair of translucent substrates, and a voltage is applied to the liquid crystal layer. At least one location between the drive circuit, a pair of polarizing plates provided on the outside of the pair of translucent substrates so that polarization transmission axes are orthogonal, and the viewing angle control device and the two polarizing plates And the driving circuit changes the alignment state of the liquid crystal molecules in the liquid crystal layer to change the light emission range to either a wide viewing angle or a narrow viewing angle. Features.

  As described above, according to the present invention, a display that can be adapted to various usage environments and applications by switching the display state between a wide viewing angle and a narrow viewing angle, and a viewing angle control device used therefor are provided. Can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the drawings referred to below, for convenience of explanation, among the constituent members of the embodiment of the present invention, only the main members necessary for explaining the present invention are shown in a simplified manner. Therefore, the display according to the present invention may include arbitrary components not shown in the drawings referred to in this specification. Moreover, the dimension of the member in each figure does not represent the dimension of an actual structural member, the dimension ratio of each member, etc. faithfully.

  FIG. 1 is a cross-sectional view showing a schematic configuration of a liquid crystal display 100 according to an embodiment of the present invention. As shown in FIG. 1, the liquid crystal display 100 includes two liquid crystal panels, a display liquid crystal panel 1 (display device) for displaying an image and a viewing angle control liquid crystal panel 2 (viewing angle control device). . The display liquid crystal panel 1 in this embodiment is a transmissive type, and a backlight 3 is used as a light source. The viewing angle control liquid crystal panel 2 is provided between the backlight 3 and the display liquid crystal panel 1. The liquid crystal display 100 performs a switching operation of the liquid crystal in the viewing angle control liquid crystal panel 2 so that the image on the display liquid crystal panel 1 can be viewed with a wide viewing angle (wide viewing angle) and a narrow viewing angle (narrow). Display angle). 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 in which a liquid crystal is sandwiched between a pair of translucent substrates, and polarizing plates 12 and 13 provided on the front and back of the liquid crystal cell 11. 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 that can display characters, images, or moving images can be used. Therefore, in FIG. 1, 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. Further, the configuration of the backlight 3 is not limited at all, and any known backlight can be used. Therefore, illustration and description of the detailed structure of the backlight 3 are also omitted.

The viewing angle control liquid crystal panel 2 includes a liquid crystal cell 21 having a liquid crystal layer sandwiched between a pair of translucent substrates, and a polarizing plate 22 provided on the backlight 3 side of the liquid crystal cell 21. The polarizing plate 22 and the above-described polarizing plate 13 are linear polarizing plates, and are arranged so that the polarization absorption axis X ₂₂ and the polarization absorption axis X ₁₃ are substantially orthogonal to each other. That is, the polarizing plates 13 and 22 are disposed so that the polarization transmission axes are substantially orthogonal to each other. If the angle formed between the polarization absorption axis X ₂₂ and the polarization absorption axis X ₁₃ is in the range of 80 ° to 100 °, a sufficient effect of switching the viewing angle can be obtained. In the liquid crystal cell 21, a liquid crystal layer is formed by bend-aligned positive type (the dielectric constant in the major axis direction of the liquid crystal molecules is higher than the dielectric constant in the minor axis direction).

  2A and 2B are schematic views showing the liquid crystal alignment state of the liquid crystal cell 21 according to the first embodiment. In these drawings, the size of liquid crystal molecules is exaggerated for easy understanding of the behavior of the liquid crystal molecules.

  As shown in FIGS. 2A and 2B, the liquid crystal cell 21 includes a pair of translucent substrates 211 a and 211 b that sandwich the liquid crystal layer 213. Transparent electrodes (not shown) are formed on the surfaces of the translucent substrates 211a and 211b using, for example, ITO (Indium Tin Oxide). Since the display liquid crystal panel 1 needs to drive the liquid crystal in display units (pixel units or segment units), the display liquid crystal panel 1 has an electrode structure corresponding to the display unit. 2 has no restriction regarding the electrode structure. For example, a uniform transparent electrode may be formed on the entire surface of the translucent substrates 211a and 211b in order to perform uniform switching over the entire display surface, or any other electrode structure may be employed.

  Horizontal alignment films 212a and 212b are provided on the surfaces of the translucent substrates 211a and 211b in contact with the liquid crystal layer 213, respectively. The liquid crystal molecules 213m in the vicinity of the horizontal alignment films 212a and 212b are aligned so that their molecular long axes are substantially parallel to the surfaces of the horizontal alignment films 212a and 212b. A pretilt is given to the horizontal alignment films 212a and 212b by a rubbing process. The pretilt angle θ (see FIG. 2A) is approximately 2 ° <θ <7 °, but it is preferable that the pretilt angle θ be as large as possible in order to reliably bend the liquid crystal. In FIG. 2A, the magnitude of θ is exaggerated from the actual value. The direction of the rubbing process in the horizontal alignment films 212a and 212b is parallel (parallel and the same direction).

Here, with reference to FIGS. 2A and 2B, the behavior of the liquid crystal molecules 213m in accordance with the applied voltage will be described. The bend alignment is maintained in the liquid crystal layer 213 of the liquid crystal cell 21 by applying a voltage within a predetermined range (for example, 2 V to 6 V in this embodiment). When a relatively low voltage V _L (for example, 2 V) is applied to the liquid crystal cell 21, as shown in FIG. 2A, the long axis of the liquid crystal molecules 213m is at the interface with the horizontal alignment films 212a and 212b. The state rises with respect to the interface by a pretilt angle θ. In this case, the major axis of the liquid crystal molecule 213m is such that, in the bulk region, the major axis of the liquid crystal molecule 213m is gradually rotated with respect to the substrate normal, and the central region of the bulk region (the center in the thickness direction of the liquid crystal layer 213) Near) the substrate normal. On the other hand, when a voltage V _H (for example, 6 V) higher than the voltage V _L is applied to the liquid crystal 21, the state of the liquid crystal molecules 213m at the interface with the horizontal alignment films 212a and 212b applies the voltage V _L. However, the liquid crystal molecules 213m are aligned so as to align the major axis with the substrate normal over almost the entire voltage bulk region. That is, comparing the case where the voltage V _L is applied with the case where the voltage V _H is applied, the vicinity of the interface with the horizontal alignment films 212a and 212b and the vicinity of the center of the bulk region (near the center in the thickness direction of the liquid crystal layer 213) ) And the liquid crystal molecules are substantially the same in the other regions, but have different retardation values in the other regions because the rotation angles of the major axis of the liquid crystal molecules are different.

The viewing angle control liquid crystal panel 2 utilizes this difference in retardation value, and switches the voltage applied to the liquid crystal cell 21 between the above voltages V _L and V _H , whereby the image of the display liquid crystal panel 1 is displayed. The display state is switched between a wide viewing angle (wide viewing angle) and a narrow viewing angle (narrow viewing angle).

FIGS. 3A and 3B are schematic cross-sectional views schematically showing the state of the liquid crystal cell 21 when the voltage applied to the liquid crystal cell 21 is V _H. When the substrate surface of the liquid crystal cell 21 is the xy plane, the rubbing direction in the horizontal alignment films 212a and 212b is the x axis, and the substrate normal direction is the z axis, FIG. FIG. 3B is a cross-sectional view in the yz plane.

  As shown in FIG. 3A, in the bend-aligned liquid crystal layer 213, the alignment of the liquid crystal molecules 213m is vertically symmetrical with respect to the substrate normal direction. 3A and 3B, in the liquid crystal layer 213, a region near the horizontal alignment film 212a is defined as a region 213a, and a region near the horizontal alignment film 212b is defined as a region 213b with the vicinity of the center in the substrate normal direction as a boundary. . In the liquid crystal cell 21, light transmitted in an oblique direction with respect to the normal line direction of the liquid crystal layer 213 has a phase difference in each of the region 213 a and the region 213 b. However, since the directions of the liquid crystal molecules in each of the regions 213a and 213b are symmetric, the phase differences generated in these regions 213a and 213b cancel each other. Therefore, as shown in FIG. 3A, assuming two light rays L1 and L2 that are parallel to the xz plane and incident so that the angles formed with respect to the substrate normal (z axis) are equal to each other, The retardation values Re1 and Re2 of the light beams are substantially equal. In addition, as shown in FIG. 3B, two light beams L3 and L4 that are incident in parallel to the yz plane so that the angles formed with respect to the substrate normal (z axis) are equal to each other may be assumed. The retardation values Re3 and Re4 of these rays are almost equal. That is, when the liquid crystal cell 21 of the viewing angle control liquid crystal panel 2 is viewed with respect to the substrate surface (xy plane), the rubbing direction (x-axis direction) and the direction orthogonal to the rubbing direction (y-axis direction) It has a symmetric luminance characteristic around the center of the substrate.

  Therefore, by providing a retardation film that compensates for any one of Re1 and Re2 and Re3 and Re4 so that the retardation between polarizing plates 13 and 22 is 0, as shown in FIG. For either one of the rubbing direction (x-axis direction) and the direction orthogonal to the rubbing direction (y-axis direction), light is not transmitted from the polarizing plate 13 with respect to the viewing angle oblique to the liquid crystal cell 21. can do. Thereby, a narrow viewing angle state can be realized.

The example shown in FIG. 4 shows the luminance distribution when the voltage applied to the liquid crystal cell 21 is V _H. As shown in FIG. 4, in this case, with respect to viewing angles near azimuth angle 0 ° or 180 °, the luminance is such that display content of display liquid crystal panel 1 can be visually recognized at almost all polar angles. With respect to the viewing angle near 90 ° or 270 °, the luminance is not high enough to allow the display contents of the display liquid crystal panel 1 to be visually recognized except in a range where the polar angle is small (almost in the front direction of the panel). Accordingly, in this example, a narrow viewing angle state is realized in which a peep from an oblique direction can be prevented with respect to a viewing angle near 90 ° or 270 °.

  In this example, the azimuth angle (θ) is 0 ° in the lower panel direction, 90 ° in the right panel direction, 180 ° in the upper panel direction, and 270 ° in the left panel direction. . The polar angle (φ) is an angle formed by a line connecting an observer's viewpoint and the center of the surface of the liquid crystal cell 21 with respect to the substrate normal line of the liquid crystal cell 21.

Further, when the voltage applied to the liquid crystal cell 21 is _VL , as shown in FIG. 5, a wide enough brightness is obtained so that the display contents of the display liquid crystal panel 1 can be visually recognized for almost all viewing angles. It becomes a viewing angle state.

As described above, in order to switch between the wide viewing angle state and the narrow viewing angle state by switching the voltage applied to the liquid crystal cell 21 between V _L and V _H , the viewing angle control liquid crystal panel of the present embodiment. 6 includes retardation films 4a and 4b, respectively, between the translucent substrate 211a and the polarizing plate 13 and between the translucent substrate 211b and the polarizing plate 22, as shown in FIG. . The retardation films 4a and 4b have a relationship of N _x > N _z > N _y . The retardation film 4 a is arranged so that its N _x axis is parallel to the polarization absorption axis X ₁₃ of the polarizing plate 13. The retardation film 4 b is arranged so that its N _x axis is parallel to the polarization absorption axis X ₂₂ of the polarizing plate 22.

As shown in FIG. 6, the polarization absorption axis X ₁₃ of the polarizing plate 13 of the display liquid crystal panel 1 is 40 ° to 50 ° (preferably with respect to the rubbing direction _{Ra with} respect to the alignment film of the translucent substrate 211a. Has an inclination of 45 °.

For example, when RDP-98006 (trade name) manufactured by Dainippon Ink & Chemicals, Inc. is used as the liquid crystal material of the liquid crystal layer 213 and the cell gap (thickness of the liquid crystal layer 213) is about 3.7 μm, the liquid crystal layer In order to obtain a narrow viewing angle state with an applied voltage V _H to 213 of 6V, the xy in-plane retardation of the retardation films 4a and 4b when viewed from a viewing angle of 45 ° polar angle is, for example, 140 nm. It is preferable to set the degree. The extraordinary refractive index ne of RDP-98006 (trade name) is 1.712, and the ordinary refractive index no is 1.514.

  As described above, the liquid crystal panel for viewing angle control 2 according to the present embodiment uses the bend-aligned liquid crystal cell 21 and the retardation film in combination, thereby narrowing the visual field in two directions such as the vertical and horizontal directions of the panel. An angular state can be obtained.

  Furthermore, the liquid crystal display 100 according to the present embodiment may use a general backlight (a backlight having a substantially average luminance distribution over the entire polar angle range) as the backlight 3, but the directional backlight. Is preferably used. A directional backlight is a backlight having a luminance distribution such that the luminance in a relatively narrow angle range centered on the front direction of the display, that is, the polar angle φ = 0 °, is higher than the luminance of other portions. Yes, it can be realized by laminating one or a plurality of lens sheets on a general backlight.

Here, the characteristics of the backlight applicable to the liquid crystal display 100 according to the present embodiment will be described with reference to FIGS. FIG. 7 is a luminance distribution diagram of the backlight 3 when a general backlight (without a lens sheet) that is not a directional backlight is used. In this case, the backlight 3 has a symmetrical luminance distribution in the horizontal direction (direction angle θ = 0 ° to θ = 180 °), but the vertical direction (azimuth angle θ = 90 ° to θ = 270 °). With respect to (direction), the luminance peak P ₁ is in the vicinity of the azimuth angle θ = 270 ° and the polar angle φ = 45 °. Note that the design in which the luminance peak P ₁ of the backlight 3 is shifted from the front direction in this way is that when two lens sheets are stacked as described later, the luminance peak is directly in front (polar angle φ = 0 °). ). That is, when a lens sheet is not used or when only one lens sheet is laminated, the luminance peak of the backlight 3 is different from the position shown in FIG.

FIGS. 8-10 shows the luminance distribution of the backlight 3 at the time of setting it as the directional backlight using a lens sheet. FIG. 8 is a luminance distribution diagram of the backlight 3 in the case where one lens sheet is laminated on the light exit surface of the backlight having the luminance characteristics of FIG. As the lens sheet, “BEF II 90/50 (trade name)” manufactured by Sumitomo 3M Limited was used, but is not limited thereto. In this case, as shown in FIG. 8, the luminance distribution is changed by laminating one lens sheet on the light emitting surface, and the luminance peak P ₂ is near the azimuth angle θ = 270 ° and the polar angle φ = 30 °. Appear. In the horizontal direction, the luminance is relatively higher than the other portions in the range where the polar angle is about 0 ° ≦ φ ≦ 40 ° and in the vertical direction the polar angle is about 0 ° ≦ φ ≦ 60 °. Become.

FIG. 9 shows a backlight 3 having a configuration in which the same lens sheet as described above is laminated on the light emitting surface of the backlight having the luminance characteristics shown in FIG. It is a luminance distribution diagram. In this case, as shown in FIG. 9, the luminance peak P ₃ appears in the vicinity of the azimuth angle θ = 270 ° and the polar angle φ = 15 °, and the polar angle in the horizontal direction is approximately 0 ° ≦ φ ≦ 60 °. With respect to the range and the vertical direction, the luminance is relatively higher than the other portions in the range where the polar angle is approximately 0 ° ≦ φ ≦ 40 °.

FIG. 10 shows the luminance distribution of the backlight 3 when the same lens sheet as described above is laminated on the light emitting surface of the backlight having the luminance characteristics shown in FIG. FIG. In this case, as shown in FIG. 10, the luminance peak P ₄ appears almost in front (azimuth angle θ = 270 °, polar angle φ = 5 ° vicinity), and the polar angle in the horizontal direction is approximately 0 ° ≦ φ. In the range of ≦ 40 ° and in the vertical direction in the range where the polar angle is about 0 ° ≦ φ ≦ 40 °, the luminance is relatively higher than the other portions.

  FIG. 11 is a luminance-polar angle characteristic diagram showing the luminance distribution in the horizontal direction (direction from azimuth angle θ = 0 ° to θ = 180 °) of the backlight 3 according to the presence or absence of the lens sheet. FIG. 12 is a luminance-polar angle characteristic diagram showing the luminance distribution in the vertical direction of the backlight 3 (direction from the azimuth angle θ = 90 ° to θ = 270 °) according to the presence or absence of the lens sheet. In FIG. 11, the polar angle on the azimuth angle θ = 180 ° side from the front direction (polar angle φ = 0 °) is represented by a negative sign, and in FIG. 12, the front direction (polar angle φ = 0 °) is represented. ) To the polar angle on the azimuth angle θ = 270 ° side with a negative sign.

  As shown in FIGS. 11 and 12, when one lens sheet is laminated, the luminance in the normal direction (polar angle φ = 0 °) is about 1.8 times that without the lens sheet (the rate of increase in luminance is About 1.60). In addition, when two lens sheets are stacked, the luminance in the normal direction is about 2.8 times that when there is no lens sheet (the luminance increase rate is about 1.95). However, since the luminance increase rate varies depending on the constituent material and design of the entire backlight system or the overall lighting effect, the above-described luminance increase rate is not always optimal.

  Moreover, Th shown in FIG. 11 and FIG. 12 represents the luminance corresponding to 50% of the luminance in the normal direction when one lens sheet is laminated. The polar angle range (horizontal direction) in which the luminance equal to or higher than Th is obtained is about 66 ° in the case of the lens sheet arrangement shown in FIG. 8, and about 96 ° in the case of the lens sheet arrangement shown in FIG. Similarly, the polar angle range (vertical direction) in which the luminance of Th or higher can be obtained is about 99 ° in the case of the lens sheet arrangement shown in FIG. 8, and about 66 ° in the case of the lens sheet arrangement shown in FIG. It is. When two lens sheets are laminated, the polar angle range in which the luminance corresponding to 50% of the luminance in the normal direction is obtained is about 58 ° in the horizontal direction and about 88 ° in the vertical direction.

  FIG. 4 shows the luminance distribution when a general backlight having a substantially average luminance distribution over the entire polar angle range is used as the backlight 3 instead of the directional backlight. When only the backlight 3 is changed to the directional backlight having the luminance distribution shown in FIG. 10 under the same conditions as when FIG. 4 is measured, the luminance distribution as shown in FIG. 13 is obtained in the narrow viewing angle state. . That is, as the luminance peak approaches the front direction, the range of the azimuth angle in which the light is shielded becomes wider. Therefore, it is possible to realize a display device that more reliably prevents peeping from others who are obliquely behind.

  FIG. 14 shows a configuration of a liquid crystal display 200 as a modification of the liquid crystal display 100 according to the present embodiment. As can be seen from a comparison between FIG. 1 and FIG. 14, in the liquid crystal display 100 and the liquid crystal display 200, the stacking order of the display liquid crystal panel 1 and the viewing angle control liquid crystal panel 2 is reversed. That is, as shown in FIG. 14, the liquid crystal display 200 has a configuration in which the display liquid crystal panel 1 is laminated on the backlight 3, and the viewing angle control liquid crystal panel 2 is further laminated thereon. In the liquid crystal display 200, the display liquid crystal panel 1 may be a transflective liquid crystal panel.

As described above, according to the liquid crystal displays 100 and 200 according to the present embodiment, when the voltage V _H is applied to the liquid crystal cell 21 of the viewing angle control liquid crystal panel 2, the display can be visually recognized only from a limited viewing angle. A narrow viewing angle display can be realized. Further, if the voltage _VL is applied to the liquid crystal cell 21 of the viewing angle control liquid crystal panel 2, the display can be viewed from a wide viewing angle.

In addition, this embodiment shows the specific example of this invention to the last, Comprising: There is no intention which limits the technical scope of this invention to these specific examples. For example, in the above description of the present embodiment, a wide viewing angle state can be obtained by setting the voltage applied to the liquid crystal cell 21 to the voltage V _L, and narrowing by setting the voltage applied to the liquid crystal cell 21 to the voltage V _H. Although the viewing angle state is obtained, the relationship between the magnitude of the applied voltage and the viewing angle may be reversed. However, taking into consideration whether the usage frequency is high in the wide viewing angle state or the narrow viewing angle state, the applied voltage for realizing the high usage state is set to V _H to reduce power consumption. From the viewpoint of

  In the above description, an example in which bend alignment is realized by performing parallel rubbing on the horizontal alignment film is shown. However, bend alignment can also be realized by forming a rib for regulating the tilt direction of the liquid crystal molecules on the alignment film.

  Furthermore, in the above description, the configuration in which the entire liquid crystal layer 213 of the viewing angle control liquid crystal panel 2 is uniformly controlled is illustrated. However, if the electrode structure of the liquid crystal cell 21 is made different for each local region, the operation of the liquid crystal can be controlled for each local region. Thereby, the viewing angle of the display screen can be varied for each local region.

  In the above description, the example in which the viewing angle control device is disposed on the back surface or the front surface of the display device has been described. However, the configuration in which the viewing angle control device is disposed on both the back surface and the front surface of the display device is also applicable. Included in the technical scope.

  In the above description, the transmissive liquid crystal panel is given as a specific example of the display device, but the display device is not limited to this. For example, a reflective or transflective liquid crystal display panel can be used as the display device. In addition to a non-light emitting display device such as a liquid crystal display panel, for example, a CRT (Cathode Ray Tube), a plasma display, an organic EL (Electronic Luminescence) element, an inorganic EL element, an LED (Light Emitting Diode) display, fluorescence A self-luminous display device such as a display tube (Vacuum Fluorescent Display), a field emission display (Field Emission Display), or a surface electric field display (Surface-conduction Electron-emitter Display) can also be used.

FIG. 15 shows a configuration example in the case of using a reflective liquid crystal display panel as the display device. The liquid crystal display 300 shown in FIG. 15 has a configuration in which the viewing angle control liquid crystal panel 2 is disposed on the front surface (observer side) of the reflective liquid crystal display panel 30. The reflective liquid crystal display panel 30 includes a reflective liquid crystal cell 31 including a reflective plate (not shown) on a substrate opposite to the observer, and a polarizing plate 32 disposed on the upper surface of the reflective liquid crystal cell 31. ing. Since the structure and operation of the reflective liquid crystal cell are well known, detailed description thereof is omitted here. In the liquid crystal display 300 shown in FIG. 15, similarly to the liquid crystal display 100, the voltage applied to the liquid crystal cell 21 of the viewing angle control liquid crystal panel 2 is switched between V _L and V _H , thereby allowing the liquid crystal display 300 to Can be switched between a wide viewing angle and a narrow viewing angle.

FIG. 16 shows a configuration example when a self-luminous display device such as an EL element is used as the display device. The display 400 shown in FIG. 16 has a configuration in which the viewing angle control liquid crystal panel 2 is disposed on the front surface (observer side) of the self-luminous display device 40. In this case, the viewing angle control liquid crystal panel 2 includes a pair of polarizing plates 22 and 23 on the front and back of the liquid crystal cell 21. The polarizing transmission axes of the polarizing plates 22 and 23 are arranged so as to be substantially orthogonal to each other. In the display 400 shown in FIG. 16, similarly to the liquid crystal display 100, the voltage applied to the liquid crystal cell 21 of the viewing angle control liquid crystal panel 2 is switched between V _L and V _H , thereby displaying the display 400. The state can be switched between a wide viewing angle and a narrow viewing angle.

  In any of the above embodiments, when the display state of the display is a narrow viewing angle, a message, an image, an icon, or the like for informing the user is displayed on the screen of the display device. May be.

  In any of the above embodiments, the driving circuit of the viewing angle control device operates according to the content of the image displayed on the display device, and automatically switches between the narrow viewing angle and the wide viewing angle. Also good. For example, when the display is used to view a web page on the Internet, referring to the software flag associated with each page according to the content of the web page, and when it is preferable content not to be seen by others, etc. You may make it switch automatically to the display state of a narrow viewing angle. Further, when the browser is activated in the encryption mode, the display state may be switched to a narrow viewing angle.

  In addition, when the display is a part of the data input device, or when the data type to be input or the data type to be input is confidential, the display is related to the data input device. It is also possible to adjust the display state to be switched to a narrow viewing angle. For example, when the user inputs some personal identification number, the display may be automatically switched to the narrow viewing angle.

  In any of the above embodiments, the viewing angle control device may be formed as a module or a cover that can be detached from the display device. When such a removable module is attached to the display device, it can be electrically connected to the display device to obtain appropriate power and control signals.

  In any of the above-described embodiments, an optical sensor (ambient sensor) that measures the ambient light of the display is further provided, and when the measured value of the optical sensor falls below a predetermined threshold, the display state of the display is set to a narrow viewing angle. It is also preferable that

  The display and the viewing angle control device according to the present invention have a wide variety of uses. For example, it is not only applied to a display of a notebook personal computer, a portable information terminal (PDA), a portable game machine, or a cellular phone, but also installed in an ATM (automatic cash dispenser) or a public place. It is applied to displays of various devices such as information terminals, ticket vending machines, and in-vehicle displays.

  In addition, the viewing angle control device according to the present invention may be implemented in a state of being incorporated in a display, but as a display component, the viewing angle control device may be manufactured and distributed as a single unit.

  INDUSTRIAL APPLICABILITY The present invention is industrially applicable as a display that can be adapted to various usage environments and applications by switching between a wide viewing angle and a narrow viewing angle, and a viewing angle control device used therefor.

It is sectional drawing which shows schematic structure of the display concerning one Embodiment of this invention. (A) is a schematic diagram showing the behavior of bend-aligned liquid crystal molecules when a relatively low voltage is applied, and (b) is a schematic diagram showing the behavior of bend-aligned liquid crystal molecules when a relatively high voltage is applied. is there. (A) And (b) is a cross-sectional schematic diagram explaining the retardation value of the liquid crystal panel for viewing angle control concerning one Embodiment of this invention. It is a chart which shows the luminance distribution at the time of a narrow viewing angle of the display concerning one Embodiment of this invention. It is a chart which shows the luminance distribution at the time of a wide viewing angle of the display concerning one Embodiment of this invention. It is a schematic diagram which shows the structure of the liquid crystal panel for viewing angle control concerning one Embodiment of this invention. It is a luminance distribution map of a general backlight (without a lens sheet). It is a luminance distribution figure of an example of the directional backlight which laminated | stacked the lens sheet. It is a luminance distribution figure of the other example of the directional backlight which laminated | stacked the lens sheet. It is a luminance distribution figure of the further another example of the directional backlight which laminated | stacked the lens sheet. FIG. 6 is a luminance-polar angle characteristic diagram showing the luminance distribution in the horizontal direction of the backlight (direction from azimuth angle θ = 0 ° to θ = 180 °) according to the presence or absence of a lens sheet. FIG. 6 is a luminance-polar angle characteristic diagram showing the luminance distribution in the vertical direction of the backlight (azimuth angle θ = 90 ° to θ = 270 °) with or without a lens sheet. 4 is a chart showing the luminance distribution of the viewing angle control liquid crystal panel in the narrow viewing angle state when only the backlight is changed to the directional backlight having the luminance distribution shown in FIG. 10 under the same conditions as those in the case of FIG. It is. It is sectional drawing which shows the structure of the other modification of the display concerning embodiment of this invention. It is sectional drawing which shows the structure of the other modification of the display concerning embodiment of this invention. It is sectional drawing which shows the structure of the other modification of the display concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display liquid crystal panel 2 Viewing angle control liquid crystal panel 3 Backlight 11 Liquid crystal cell 12 Polarizing plate 13 Polarizing plate 21 Liquid crystal cell 22 Polarizing plate 23 Polarizing plate 30 Reflective liquid crystal display panel 31 Liquid crystal cell 32 Polarizing plate 40 Self-luminous display Device 100 Liquid crystal display 200 Liquid crystal display 300 Display 400 Display

Claims (14)

A display device driven according to an image to be displayed;
A display provided with at least one of a rear surface and a front surface of the display device, and a viewing angle control device for controlling a viewing angle of the display device,
The viewing angle control device includes a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are bend-aligned between a pair of translucent substrates, and a drive circuit for applying a voltage to the liquid crystal layer,
The liquid crystal cell is disposed between two polarizing plates disposed so that the polarization transmission axes are substantially orthogonal within the display,
In at least one place between the viewing angle control device and the two polarizing plates, a retardation film is provided,
The driving circuit changes the alignment state of the liquid crystal molecules in the liquid crystal layer of the viewing angle control device, thereby changing the display state to a first state providing a first viewing angle range and a first viewing angle range. A display that is switchable between a second state that is within and provides a second viewing angle range that is narrower than the first viewing angle range. The liquid crystal layer of the viewing angle control device includes a positive nematic liquid crystal,
The driving circuit provides the first viewing angle range by applying a first voltage to the liquid crystal layer, and applying a second voltage higher than the first voltage to the liquid crystal layer. The display of claim 1, providing the first viewing angle range.   The display according to claim 1 or 2, wherein rubbing treatment is performed in parallel and in the same direction with respect to the alignment films respectively included in the pair of translucent substrates of the liquid crystal cell.   The display according to any one of claims 1 to 3, wherein the two polarizing plates are arranged so that their polarization transmission axes intersect each other in a range of 80 ° to 100 °. The display device is a display device that emits linearly polarized light,
The display according to any one of claims 1 to 4, wherein one of the two polarizing plates is a polarizing plate provided in the display device.   The display according to claim 1, wherein the display device is a transmissive liquid crystal display device and further includes a backlight.   The display according to claim 6, wherein the viewing angle control device is disposed between the backlight and the transmissive liquid crystal display device.   The display according to claim 6, wherein the viewing angle control device is disposed on a front surface of the transmissive liquid crystal display device.   The display according to any one of claims 6 to 8, wherein the backlight is a directional backlight having directivity in a normal direction.   The display according to any one of claims 1 to 5, wherein the display device is a reflective liquid crystal display device or a transflective liquid crystal display device. The display device is a self-luminous display device,
5. The display according to claim 1, wherein one of the two polarizing plates is provided between the self-luminous display device and the viewing angle control device.   The polarizing transmission axis of the polarizing plate is disposed so as to intersect with the alignment axis of the liquid crystal molecules viewed from the normal direction of the viewing angle control device in a range of 40 ° to 50 °. The display according to any one of the above. A viewing angle control device which is arranged according to an image to be displayed and is arranged on at least one of a back surface and a front surface of a display device which emits linearly polarized light, and is used for controlling a viewing angle of the display device,
A liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are bend-aligned between a pair of translucent substrates;
A drive circuit for applying a voltage to the liquid crystal layer;
A polarizing plate provided on the opposite side of the plane of incidence of linearly polarized light from the display device in the liquid crystal cell and having a polarization transmission axis substantially orthogonal to the plane of polarization of the linearly polarized light;
A retardation film provided in at least one place between the viewing angle control device and the two polarizing plates;
The drive circuit changes the alignment state of the liquid crystal molecules in the liquid crystal layer, so that the light emission range is within the first viewing angle range and the first viewing angle range, and from the first viewing angle range. A viewing angle control device capable of switching between a narrow second viewing angle range. A viewing angle control device that is disposed in front of a self-luminous display device that is driven according to an image to be displayed and is used to control the viewing angle of the self-luminous display device,
A liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are bend-aligned between a pair of translucent substrates;
A drive circuit for applying a voltage to the liquid crystal layer;
A pair of polarizing plates provided outside the pair of translucent substrates so that the polarization transmission axes are substantially orthogonal;
A retardation film provided in at least one place between the viewing angle control device and the two polarizing plates;
The drive circuit changes the alignment state of the liquid crystal molecules in the liquid crystal layer, so that the light emission range is within the first viewing angle range and the first viewing angle range, and from the first viewing angle range. A viewing angle control device capable of switching between a narrow second viewing angle range.

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