JP2006171333A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of surely preventing a display screen from being visualized from a specified direction at a specified utilization time , thereby enhancing the convenience and security of the device. <P>SOLUTION: In the display device, a second liquid crystal display portion to control a viewing angle is arranged on a first liquid crystal display portion to display a picture. Transparent substrates disposed so as to be opposite to each other are disposed on polarizing plates of the first liquid crystal display portion. Alignment layers are formed on the respective mutually opposing faces of the transparent substrates. A liquid crystal layer is filled between the alignment layers. A second polarizing plate is disposed on the display surface of the second liquid crystal display portion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of preventing peeping.

  Liquid crystal display elements are now widely applied to information devices such as computers and mobile phones, large-sized TVs, large and small consumer display devices, and industrial devices such as ATMs. Among these applications, information devices such as notebook PCs and mobile phones, industrial information devices such as information terminals (kiosk information terminals) in ATMs and convenience stores, navigation display elements, etc., require a wide viewing angle. In some cases, however, there is a high demand for preventing others from peeping. For example, when the ATM is not used, the viewing angle is widened and used as an advertising medium. On the other hand, when the ATM is used, there is a demand for narrowing the viewing angle and preventing others from looking into it. In addition, in a vehicle-mounted navigation system, a system is desired in which information such as a map can be seen from the driver when the vehicle is stopped, while only a passenger seat is visible from the driver's seat while driving.

  Conventionally, as a technique for narrowing the viewing angle, methods using a liquid crystal display device having both a liquid crystal layer for image display and a liquid crystal layer for phase difference control are disclosed in Patent Document 1, Patent Document 2, and Patent Document 3. ing. A method using a lens sheet as a narrow viewing angle technique is disclosed in Patent Document 4, and a liquid crystal display device using a diffusion light guide plate is disclosed in Patent Document 3. For example, Patent Document 1 discloses a structure in which another liquid crystal element is placed on a liquid crystal display element (LCD). In this structure, no polarizing plate is interposed between the liquid crystal display element and the other liquid crystal elements, and deflecting plates are arranged on both sides thereof. Thus, in the apparatus disclosed in Patent Document 1, the other liquid crystal element added to the liquid crystal display element (LCD) has a function of controlling the phase difference of one liquid crystal display element. Birefringence is controlled, that is, the viewing angle itself is controlled.

  In addition, the display screen can be clearly seen from the front of the liquid crystal display device in the same manner as a normal liquid crystal display without being bound by the narrow viewing angle technology. Japanese Patent Application Laid-Open No. H10-228707 discloses a liquid crystal display device that prevents a peep by preventing a fixed image that is irrelevant from being viewed and obstructing viewing from a direction other than the front.

In addition, Non-Patent Documents 1 to 3 describe the transmission characteristics of the liquid crystal display element, but are merely reported on the characteristics, and have not been studied on a liquid crystal display device that prevents any peeping.
JP-A-11-174489 JP-A-11-007045 JP 09-010598 JP 10-097199 A JP 2001-264768 A Takano / Ikezaki / Teriya / Tajima / Suzuki Proceedings of the 16th Liquid Crystal Symposium p220 (1990) Hisatake / Sato / Yamamoto / Ishikawa / Hato 18th Liquid Crystal Discussion Symposium Proceedings p290 (1992) H. Takano, M. Ikezaki, S. Suzuki the IV International Topical Meeting on Optics of Liquid Crystals, Oct. 7-11, 1991, Cocoa Beach, Fla

  As described above, there are various techniques such as a technique for narrowing the viewing angle disclosed in Patent Documents 1 to 5 or a technique for preventing a peep by visually recognizing a fixed image unrelated to the display screen disclosed in Patent Document 5. Peep prevention technology has already been proposed. However, in the display device disclosed in Patent Document 1, the light incident on the other liquid crystal element to be added does not form an image, the viewing angle is limited, and coloring may occur.

  There is a demand for the emergence of a peek prevention technique that is more convenient and more reliable than such conventional techniques.

  The present invention has been made in order to solve the above-described problems, and the object thereof is to reliably hinder the visual recognition of the display screen from a specific direction at the time of specific use, thereby improving the convenience and safety of the device. The object is to provide a liquid crystal display device.

According to this invention,
First and second substrates opposed to each other, wherein at least the second substrate on the display surface side is formed transparently; and
A plurality of first and second electrodes corresponding to each of the plurality of pixels formed on the first and second substrates;
First and second alignment films formed on inner surfaces of the first and second substrates facing each other;
A first liquid crystal layer filled between the first and second alignment films and aligned according to the alignment characteristics of the first and second alignment films; and at least provided on the second substrate on the display surface side A first polarizing plate,
A first liquid crystal display unit comprising:
A third transparent substrate provided on the first polarizing plate and a fourth transparent substrate disposed to face the third transparent substrate;
Third and fourth transparent electrodes formed on inner surface regions of the third and fourth substrates facing each other corresponding to the display region of the first liquid crystal display unit;
Third and fourth alignment films respectively formed on opposing surfaces of the third and fourth transparent substrates;
A second liquid crystal layer filled between the third and fourth alignment films and aligned according to the alignment characteristics of the third and fourth alignment films; and provided on the display surface side of the fourth substrate. A second polarizing plate,
A second liquid crystal display unit comprising:
A display device is provided.

Moreover, according to this invention,
First and second substrates opposed to each other, wherein at least the second substrate on the display surface side is formed transparently; and
A plurality of first and second electrodes corresponding to each of a plurality of pixels formed on the first and second substrates;
First and second alignment films formed on inner surfaces of the first and second substrates facing each other;
A first liquid crystal layer filled between the first and second alignment films and aligned according to the alignment characteristics of the first and second alignment films; and at least provided on the second substrate on the display surface side A first polarizing plate,
A first liquid crystal display unit comprising:
A third transparent substrate provided on the first polarizing plate and a fourth transparent substrate disposed to face the third transparent substrate;
Third and fourth transparent electrodes formed on inner surface regions of the third and fourth substrates facing each other corresponding to the display region of the first liquid crystal display unit;
Third and fourth alignment films respectively formed on opposing surfaces of the third and fourth transparent substrates;
A second liquid crystal layer filled between the third and fourth alignment films and aligned according to the alignment characteristics of the third and fourth alignment films; and provided on the display surface side of the fourth substrate. A second polarizing plate,
A second liquid crystal display unit comprising:
A fifth transparent substrate provided on the second polarizing plate and a sixth transparent substrate disposed opposite to the fifth transparent substrate;
Fifth and sixth transparent electrodes formed on inner surface regions of the fifth and sixth substrates facing each other corresponding to the display region of the first liquid crystal display unit;
Fifth and sixth alignment films respectively formed on opposing surfaces of the fifth and sixth transparent substrates;
A third liquid crystal layer filled between the fifth and sixth alignment films and aligned according to alignment characteristics of the fifth and sixth alignment films; and a display surface side of the sixth substrate. A third polarizing plate,
A third liquid crystal display unit comprising:
A display device is provided.

  According to the liquid crystal display device of the present invention, it is possible to improve the convenience and safety of the device by reliably obstructing the visual recognition of the display screen from a specific direction at the time of specific use.

  The liquid crystal display device according to the embodiment of the present invention has been made based on the following idea of the inventors, and the idea of the inventors will be described prior to the description of the specific embodiment.

  In general, a liquid crystal element displays an image or the like by adjusting the light transmittance using the change in optical anisotropy depending on the voltage of a liquid crystal material. Moreover, in order to utilize the optical anisotropy of the liquid crystal material, polarizing plates disposed on both sides thereof are disposed. That is, when the observer observes the liquid crystal element, polarized light is observed instead of natural light. Therefore, image information appearing from the liquid crystal element can be further controlled by appropriately controlling the polarization.

  The liquid crystal display device of the present invention has been made based on such an idea, and the polarized light emitted from the first liquid crystal display element for image display is further supplied to the liquid crystal of the second liquid crystal display element. The viewing angle of the liquid crystal display element is controlled by passing the layers. That is, by providing the second liquid crystal display element for controlling the viewing angle on the first liquid crystal display element for image display, the viewing angle is limited, and peeping can be prevented.

  Preferably, in the second liquid crystal display element that controls the viewing angle, the two liquid crystal display elements provided in the liquid crystal display element are arranged with respect to the transmission axis of the polarizing plate provided between the first and second liquid crystal display elements. The viewing angle is controlled by adopting an o-mode in which the rubbing direction of the alignment film is set substantially perpendicular to the transmission axis of the polarizing plate.

  In a simple TN mode liquid crystal display element, an e-mode is generally adopted. However, in the second liquid crystal display element that controls the viewing angle, it is preferable to adopt an o mode (o-mode) instead of the e mode (e-mode). Here, the e mode (e-mode) means a light transmission mode in a liquid crystal structure in which the rubbing direction is parallel to the direction of the transmission axis of the polarizing plate, and the o mode (o-mode) is This means a light transmission mode in a liquid crystal structure in which the rubbing direction is orthogonal to the direction of the transmission axis of the polarizing plate.

  The liquid crystal display element for viewing angle control as the second liquid crystal display element can view an image displayed on the first liquid crystal display element with a wide viewing angle condition and only from one of the left and right directions. It is important to be able to set narrow viewing angle conditions that can be used. As an example, in the case of adapting to a car navigation system, as a narrow viewing angle condition, it is necessary to realize a state where the contents of the liquid crystal display element cannot be sufficiently seen when viewed from a wide area including the driver's seat. As will be described in detail in the examples, in the o mode (o-mode) compared to the above-described e mode (e-mode), the transmittance decreases when observed from a wide direction, and viewed from a part of the range. Other than this, it is possible to realize a driving condition in which the contents of the first liquid crystal display element cannot be observed. In the e-mode, the region where the transmittance of the second liquid crystal element is low cannot be made sufficiently wide.

  Further, in order to maximize the peeping prevention characteristics, the second liquid crystal unit and the third liquid crystal unit are provided in the second liquid crystal unit, and the second liquid crystal unit and the third liquid crystal unit are in the o mode. (O-mode) is preferably set, and the second liquid crystal part and the third liquid crystal part are provided with a structure in which the liquid crystal material which is a constituent element is twisted in the opposite direction, so that the second liquid crystal part and the third liquid crystal part The third liquid crystal unit can be set to o mode.

  In order to achieve the o-mode, it is necessary to perform the rubbing treatment on the alignment films constituting the second liquid crystal portion and the third liquid crystal portion so as to induce reverse twist directions. In order to achieve this more effectively, an optically active material added to the liquid crystal material used for the second liquid crystal part and an optically active material added to the liquid crystal material used for the third liquid crystal part are used. It is preferable to select optically active substances having different optical rotations so as to induce a twist in the reverse direction when added to the material.

  In this way, the most efficient optical element can be configured by selecting the liquid crystal material and the rubbing direction so that the twist directions of the liquid crystal materials of the two liquid crystal elements are opposite to each other.

  Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device includes a first liquid crystal display unit 2 that can display a normal image and a second liquid crystal display unit 4 that controls the display by switching the display of the display device.

  The first liquid crystal display unit 2 employs a TFT structure. In this TFT structure, as is well known, the first and second transparent substrates 6 and 8 are arranged to face each other, and on the outer surface side thereof. Are formed with first and second polarizing plates 10 and 12 having first and second transmission axes. An active element (not shown) such as a TFT is formed on the inner surface of the first substrate 6 facing the second substrate 8, and an element driving wiring (not shown) for applying a voltage to the active element. A transparent pixel electrode (ITO electrode) 14 connected to the active element is formed as the first electrode. A first alignment film 16 is formed on these active elements, element driving wirings, and pixel electrodes 14. A backlight as a light source of the first liquid crystal display unit 2 is provided outside the first substrate 6, and a backlight beam from the backlight is directed from the first substrate 6 onto the second substrate 8. It has been. The first alignment film 16 is rubbed so as to give a predetermined alignment direction as will be described later as an example.

  A transparent common electrode (ITO electrode) 18 is formed as a second electrode on the inner surface of the second substrate 8 facing the first substrate 6, and the second alignment film 20 is formed on the common electrode 18. Is formed. Similarly, the second alignment film 20 is rubbed so as to give a predetermined alignment direction as will be described later as an example. A seal portion 22 that supports the substrates 6 and 8 is provided around the first and second substrates 6 and 8, and a uniform gap is provided between the first and second substrates 6 and 8 facing each other. The first liquid crystal layer 24 is filled between the first and second alignment films 16 and 20 disposed in the gap. The first liquid crystal layer 24 is sealed in the first liquid crystal display unit 2 by the seal portion 22 and the substrates 6 and 8.

  In the first liquid crystal display unit 2, a driving voltage signal is given from the liquid crystal driving circuit 30 to the common electrode 18 and the element driving wiring based on the image signal supplied from the external circuit to the liquid crystal driving circuit 30. The active element is selectively activated according to the voltage application of the drive wiring, and a voltage is applied between the pixel electrode 14 and the common electrode 18. Accordingly, the alignment characteristic of each liquid crystal cell defined by each pixel electrode 14 in the first liquid crystal 24 is changed, and the transmission of the backlight beam is controlled for each liquid crystal cell so that an image signal is transmitted through the second substrate 8. A corresponding image is observed.

  Here, the first liquid crystal unit 2 is not particularly limited as long as the polarizing plates 10 and 12 are arranged on both surfaces thereof, and a TN liquid crystal, STN liquid crystal, IPS liquid crystal, or MVA liquid crystal system is used. It is possible.

  As will be described later, the second liquid crystal display unit 4 displays the image displayed on the first liquid crystal display unit 2 and the visual field restriction mode for limiting the viewing range of the image displayed on the first liquid crystal display unit 2. It has a structure that can be switched to a wide viewing mode for displaying over a wide viewing angle determined by the apparatus. That is, in the second liquid crystal display unit 4, a transparent third substrate 42 is provided on the second polarizing plate 12 of the first liquid crystal display unit 2, and similarly, facing the third substrate 42. A transparent fourth substrate 44 is disposed. Similarly, a third polarizing plate 46 is formed on the outer surface of the fourth substrate 44.

  Transparent third and fourth electrodes 48 and 50 are formed on the inner surfaces of the third and fourth substrates 42 and 44 facing each other, and on the third and fourth electrodes 48 and 50, respectively. Third and fourth alignment films 52 and 54 are formed. A gap between the third and fourth alignment films 52 and 54 defined by the third and fourth substrates 42 and 44 is filled with the second liquid crystal 56, and the third and fourth substrates 42 and 44 are filled. Is provided with a seal portion 58 that supports the substrates 42 and 44, and the second liquid crystal 56 is provided in the second liquid crystal display portion by the third and fourth substrates 42 and 44 and the seal portion 58 facing each other. 4 is sealed.

  Here, the second liquid crystal unit 4 is provided for controlling the polarized light emitted from the polarizing plate 12 on the surface of the first liquid crystal display unit 2, and later according to the direction in which the viewing angle is to be controlled. As described in a specific embodiment, the liquid crystal unit 4 is given an appropriate structure. For example, in order to provide an appropriate field of view with high luminance, the third alignment film 52 is determined so that the rubbing direction thereof is substantially orthogonal to the light transmission axis of the second polarizing plate 12. The alignment film 54 is preferably determined so that the rubbing direction thereof is substantially orthogonal to the light transmission axis of the third polarizing plate 46.

  The second liquid crystal unit 4 is not particularly limited to a specific type of liquid crystal element, but the third and fourth alignment films 52 and 54 on the third and fourth substrates 42 and 44 are not limited. TN system in which the orientation (rubbing) directions of the substrate are orthogonal, and a homogeneous system in which the rubbing directions of the upper and lower substrates are made parallel. Of these liquid crystal elements, a TN liquid crystal element is particularly suitable.

  As will be described later, the second liquid crystal display unit 4 has a halftone display state between the display switching circuit 60 and the third and fourth electrodes 48 and 50 in accordance with the direction of the transmission axis of the second polarizing plate 46. When the voltage corresponding to is applied, the normally white type that is set to the field-of-view restriction mode, and when the voltage higher than the saturation voltage is applied between the third and fourth electrodes 48 and 50, the wide-field mode is set. There is a normally black type.

  In the normally white type, when no voltage is applied between the third and fourth electrodes 48 and 50, the light from the first liquid crystal display unit 2 is transmitted without limitation and allowed to pass as it is. Thus, the image displayed on the first liquid crystal display unit 2 can be observed from the outside. In the normally white type, when a voltage is applied between the third and fourth electrodes 48 and 50 from the display switching circuit 60 according to the control signal, the alignment characteristics of the liquid crystal 56 of the first liquid crystal display unit 2 are obtained. Is changed so that the transmission distribution of the light beam is limited, and the light beam from the first liquid crystal display unit 2 is emitted in a distribution toward a specific direction. Therefore, the area where the image displayed on the first liquid crystal display unit 2 can be observed is limited.

  In the normally black type, when a voltage corresponding to a halftone is applied between the third and fourth electrodes 48 and 50, light is transmitted according to the alignment characteristics of the liquid crystal 56 of the first liquid crystal display unit 2. The distribution is limited, and light is emitted from the first liquid crystal display unit 2 in a distribution directed in a specific direction. Therefore, the area where the image displayed on the first liquid crystal display unit 2 can be observed is limited. In the normally black type, when a voltage higher than the saturation voltage is applied between the third and fourth electrodes 48 and 50 from the display switching circuit 60 according to the control signal, the liquid crystal of the second liquid crystal display unit 4 is displayed. The orientation characteristics of 56 are changed, and the light beam from the first liquid crystal display unit 2 is transmitted without being limited, and passed through as it is, and an image displayed on the first liquid crystal display unit 2 is observed from the outside with a wide field of view. be able to.

  As mentioned above, normally white and normally black are used to mean that light is not restricted in the normal state and light is restricted in the normal state, and it should be noted that it has no meaning of white or black. .

  The second liquid crystal unit 4 described above can provide characteristics according to the purpose of use. For example, in applications such as ATMs and kiosk information terminals, the transmittance in the oblique direction can be adjusted while maintaining the transmittance in the front direction. In such applications, it is preferable to select a value Δnd of 1.5 or more, preferably 2 or more and 3 or less as the liquid crystal material. Here, Δn represents the refractive index anisotropy, and d represents the thickness of the liquid crystal layer.

  Further, in applications where the transmittance in the front direction does not become a problem as in a navigation system, it is preferable that Δnd of the liquid crystal material is as small as possible. This is based on the following reason.

  When voltage is applied, the transmittance at a specific angle is minimized, but when the panel is further observed from the outside, a phenomenon in which the transmittance increases again is observed. That is, when a voltage is applied, even if the transmittance from a specific angle decreases and the first liquid crystal display unit 2 becomes invisible, a phenomenon occurs in which the first liquid crystal display unit 2 can be seen through from the outside. As a result, a phenomenon occurs in which the range in which the first liquid crystal display unit 2 cannot be seen becomes very narrow. This phenomenon is likely to occur when Δnd represented by the following formula (1) is large. Therefore, the smaller this Δnd, the better.

  As the TN liquid crystal element, Δnd has a preferable minimum value. This minimum value is referred to as the first minimum Δnd. The first minimum value Δnd is about 0.5, which maximizes the transmittance in front of the display element. However, in the car navigation display element of an automobile, the front direction is not particularly important, and the transmittance in the direction toward the passenger seat or driver seat is important. In other words, the condition for maximizing the transmittance from the passenger seat or driver seat becomes important.

When the second liquid crystal display unit 4 is a TN liquid crystal element, when the thickness of the liquid crystal layer of the second liquid crystal element is dμm and the refractive index anisotropy of the liquid crystal layer is Δn,
Δnd = a × COS ⁻¹ θ. . . (1)
(A is 0.5 ± 0.1, and θ is an arbitrarily set angle.)
The relationship expressed by Here, in the liquid crystal display device for automobile navigation, θ corresponds to an angle formed with respect to a perpendicular corresponding to the front direction, and can provide the maximum transmittance in this direction. You can see a brighter display.

  The voltage applied to the liquid crystal of the second liquid crystal unit 4 can be selected according to the purpose and application, but the brightness from the front such as an ATM or kiosk information terminal cannot be reduced. It is preferable to apply a voltage of 40% to 60% with respect to the saturation voltage of the liquid crystal element. On the other hand, it is preferable to apply a voltage of 60% to 80% with respect to the saturation voltage of the liquid crystal element for a navigation system or the like that does not need to consider a reduction in front luminance.

  On the other hand, when it is necessary to prevent peeping, it is preferable to reduce the luminance of the first liquid crystal unit 2 as well. That is, it is more difficult to look into a person who has lowered the luminance of the front as much as possible within a range in which the front visibility is maintained. Furthermore, it is preferable that the screen in the first liquid crystal unit 2 that is desired to be prevented from being viewed is configured only in a halftone. In other words, in the case of gradation display from gradations L0 to L63, it is preferable to configure a screen that avoids the vicinity of gradation L0 or the vicinity of gradation L63 and does not want to be viewed only in the gradation of the halftone as much as possible. In that case, it is preferable to make the display monotone and avoid color display as much as possible.

  The first liquid crystal display unit 2 shown in FIG. 1 has been described as an active matrix type display unit structure in the above description, but the present invention naturally has a structure such as a passive matrix type display unit. Obviously it can be applied. In FIG. 1, the image is displayed by a transmitted light from the backlight. However, naturally, the light is incident on the apparatus shown in FIG. 1 and the image is reflected by the reflected light. Obviously, it may be displayed. In this reflection system, it is obvious that the first substrate 6 on the side opposite to the image observing side may not be a transparent substrate. In the case of the reflection method, it is clear that the polarizing plate 10 provided on the outer surface of the first substrate 6 is not necessary.

  The optical arrangement of the liquid crystal display device shown in FIG. 1 and its modifications will be described in more detail with reference to various embodiments. In the following embodiments, when a voltage is applied to the second liquid crystal display unit 4 and the third liquid crystal display unit 9, all voltages corresponding to halftone display are applied. This is the same even when a specific voltage value is shown or when a specific voltage value is not shown.

Example 1
FIG. 2 is a schematic diagram showing an optical arrangement of an optical system according to a normally white type in the liquid crystal display device shown in FIG. As shown in FIG. 2, the display element as the first liquid crystal display unit 2 is opposed to the first and second polarizing plates 10 and 12 facing each other, and similarly between the polarizing plates 10 and 12. Optical components such as a liquid crystal layer made of liquid crystal provided between the first and second alignment films 16 and 20 and the alignment films 16 and 20 are arranged. The first liquid crystal display element 2 is a normal liquid crystal element, and can be selected from TN liquid crystal, STN liquid crystal, IPS liquid crystal, MVA liquid crystal, etc. An attached liquid crystal element may be used.

  A polyimide film is formed as a third alignment film 52 that is rubbed on the glass substrate 42 on which the ITO electrode is formed in contact with the first liquid crystal element, and the third alignment film 52 is formed on the substrate 44. Oppositely, a polyimide film is similarly formed as the fourth alignment film 54. A liquid crystal material for TN type liquid crystal (for example, ZLI4792 manufactured by Merck Co., Ltd.) is filled between the alignment films 52 and 54 so that the thickness of the liquid crystal layer is 5 μm, and the periphery is sealed with a sealant 58. A liquid crystal element is formed as the second liquid crystal display unit 4 on the first liquid crystal display unit 3. A polarizing plate 46 is installed on the outer surface of the second liquid crystal display unit 4.

  In FIG. 2, arrows P1, P2, and P3 indicated by the first, second, and third polarizing plates 10, 12, and 46 indicate transmission axes of polarized light that can pass through the polarizing plates 10, 12, and 46. The arrows R1, R2, R3, and R4 shown in the first, second, third, and fourth alignment films 16, 20, 52, and 54 indicate the direction of the rubbing process, respectively. Arrows R1 and R3 indicated by solid lines indicate that the alignment films 16 and 52 on the upper surface side of the substrates 6 and 42 are rubbed, and arrows R2 and R4 indicated by broken lines indicate the lower surface side of the substrates 8 and 44. This shows that the alignment films 20 and 54 are rubbed.

  In the display device shown in FIG. 2, in the first liquid crystal display unit 2, the rubbing direction R <b> 1 of the alignment film 16 adjacent to the transmission axis P <b> 1 of the polarizing plate 10 is set parallel to the polarizing plate 12. The rubbing direction R2 of the alignment film 20 adjacent to the transmission axis P2 is set in parallel.

  On the other hand, in the second liquid crystal display unit 4, the rubbing direction R3 of the alignment film 52 adjacent to the transmission axis P2 of the polarizing plate 12 is set so as to be substantially orthogonal to the transmission axis P2 of the polarizing plate 46. The rubbing direction R4 of the alignment film 54 adjacent to P3 is set so as to be substantially orthogonal to P3. That is, in the second liquid crystal display unit 4, the o-mode in which the rubbing directions R 3 and R 4 of the alignment films 52 and 54 are determined substantially perpendicular to the transmission axes P 2 and P 3 of the polarizing plates 12 and 46 that are close to each other. When (o-mode) is employed and the second liquid crystal display unit 4 is activated in the view restriction mode, the viewing angle is controlled.

  Next, a usage mode of the display device shown in FIG. 2 will be described.

The display device shown in FIG. 2 can be used without particular limitation as long as it is used as a display device. The display device shown in FIG. 2 is particularly suitable for an ATM, a digital kiosk terminal, a public device such as a resident ticketing machine, an electronic ballot box, etc., which are arranged horizontally or close to each other.

  For financial equipment such as ATMs and digital kiosks, or electronic ballot boxes and resident card ticketing machines, information such as deposit balances, personal names and withdrawal amounts, or personal information such as the names and addresses of candidates voted by individuals are displayed. The

  FIG. 3 shows the positions of the device 60, the user 62, and the peeping people 63, 64 when using the display device shown in FIG. The device 60 is surrounded by frames in three directions I, II and III, and no one can see the device 60 from this direction. The user 62 observes the display while standing in the direction IV. On the other hand, those peeping persons 63 and 64 who are not regular observers observe within a range of −50 degrees to 50 degrees when the IV direction is defined as 0 degrees with respect to the regular observer 62. become.

  Next, considering the angle formed between the line-of-sight direction of the display user 62 and the normal direction of the display surface, a regular observer can observe the angle from about 0 degrees to 20 degrees. On the other hand, the angle formed by the peeper is generally in the range of 60-80 degrees.

  When the normally white second liquid crystal element 4 shown in FIG. 2 is in a no-voltage state, the entire viewing angle is substantially the same as the viewing angle of the first liquid crystal element, so that it is displayed on the first liquid crystal element. The information can also be read from those around.

  On the other hand, when a voltage V of 1.5V to 2V is applied to the second liquid crystal element 4 to the second liquid crystal element 4 whose saturation voltage Vmax is set to 4V, the second liquid crystal element 4 In the horizontal plane from the front, the transmittance of −45 degrees to 45 degrees is 30% or less, and it is difficult for a person other than the front observer to visually recognize the information displayed on the display element.

  The voltage V applied to the second liquid crystal element 4 is preferably adjustable depending on the degree of security of display information, the brightness of the installation location, and the position where a person who is looking into can stand, but the saturation voltage Vmax of the liquid crystal display element 4 It is preferable to apply an AC voltage of 40% to 60% (maximum voltage if rectangular wave, effective value if sine wave). If it is 40% or less, it becomes difficult to obtain a sufficient peeping prevention effect for a normal purpose, and when a voltage V of 60% or more is applied, the front luminance decreases greatly. Furthermore, it has been found that even when observed from −45 ° to 45 °, a phenomenon in which peeping prevention is insufficient and the content is visually recognized again is observed. Therefore, it is preferable to drive with a voltage V between 40% and 60% of the saturation voltage Vmax.

  Even in the above manner, there is a case where the effect of preventing peeping is not sufficient with respect to what is peeped from other than the user.

In that case,
1． When peep prevention is required, the luminance of the display element displaying information is reduced from 80% to 50% with respect to the maximum luminance.

  2． The display for which peeping prevention is to be made is a monotone, and the display is composed of gradations as close as possible. In the case of a liquid crystal display element capable of displaying with gradations L0 to L63, it is preferable to avoid the display near the gradation L0 and the vicinity of L63 and to display halftones. Further, avoiding the use of colors and making them monotone can further enhance the peep prevention effect.

  According to the apparatus and the display method as described above, it is possible to realize a display device in which display contents are normally observed by an authorized user and display contents are not visually recognized by others.

  As described above, such an apparatus can be used for public equipment such as ATM terminals, digital kiosk terminals, and resident card issuing machines installed horizontally.

  In order to use this method, it is necessary that the transmission axis of the polarizing plate on the viewer side of the liquid crystal display element displaying characters and images is around 45 degrees as defined above.

(Example 2)
FIG. 4 schematically shows an optical system of a display device according to the second embodiment in which the second liquid crystal element 4 is installed on the first liquid crystal display element 2 having a diagonal size of 8 inches.

  About the display apparatus shown in FIG. 4, the same code | symbol is attached | subjected about the same location or the same part as the display apparatus shown in FIG. 2, and the description is abbreviate | omitted. In the display device shown in FIG. 4, in the second display unit 4, the rubbing treatment direction R4 of the alignment film 54 is directed in the direction opposite to the rubbing treatment direction R4 of the alignment film 54 shown in FIG.

  A case where the display device shown in FIG. 4 is used as a car navigation system will be described with reference to FIG.

  FIG. 5 schematically shows how the display device shown in FIG. 4 is used, and the display unit 71 of the car navigation system is attached to the dashboard of the vehicle.

  In the display device shown in FIG. 4, when the vehicle is stopped, a voltage is applied between the electrodes 48 and 50 of the second liquid crystal display unit 4, and the driver 72 and the passenger 73 in the passenger seat It is possible to simultaneously view images displayed on the display unit 71 of the navigation system.

  When the automobile is running, that is, when the driver 72 is driving, the electrodes of the second liquid crystal display unit 4 are applied so that a voltage V of 30% to 70% of the saturation voltage Vmax of the liquid crystal element is applied to the liquid crystal 56. A voltage is applied between 48 and 50. Accordingly, the transmittance of the second liquid crystal display unit 4 as viewed from the direction of the driver 72 is set to 10% or less so that the driver 72 cannot see the image of the second liquid crystal display unit 4 during driving. ing. As a result, the driver cannot see the display contents of the navigation system during driving, and side-by-side driving is prevented.

  On the other hand, the passenger 73 sitting in the passenger seat can always visually recognize the display unit 71 of the car navigation system. The voltage V applied between the electrodes 48 and 50 of the second liquid crystal display unit 4 is preferably 60% to 80% of the saturation voltage Vmax of the liquid crystal 56. When it is 60% or less, it is possible to see from the driver's seat, and when it is 80% or more, the visibility from the passenger seat is dark.

  In addition, it is effective to use this system in conjunction with the driving situation of the automobile. In other words, when the engine is stopped, the voltage applied between the electrodes 48 and 50 of the second liquid crystal display unit 4 is cut off and can be used more appropriately by applying the voltage at the same time as the automobile moves (or moves forward). It is preferable to be able to do this.

(Example 3)
FIGS. 6A and 6B schematically show the arrangement of the optical system of the second liquid crystal display unit 4 adopting the configuration of the e mode (e-mode) and the o mode (o-mode). .

  In the second liquid crystal display element 4 shown in FIGS. 6A and 6B, the same reference numerals are given to the same portions or the same portions as those in the display device shown in FIG. In the second liquid crystal display element 4 shown in FIGS. 6A and 6B, the rubbing direction R3 of the third alignment film 52 and the rubbing direction R4 of the fourth alignment film 54 are the same. The transmission axis P2 of the second polarizing plate 12 and the transmission axis P3 of the third polarizing plate 46 are different from each other. That is, in the second liquid crystal display element 4 shown in FIG. 6A adopting the e-mode, the transmission axis P3 of the third polarizing plate 46 is the rubbing direction R4 of the fourth alignment film 54. In the second liquid crystal display element 4 shown in FIG. 6B that employs an o-mode, the third polarizing plate 46 has a parallel relationship. The transmission axis P3 is set to be orthogonal to the rubbing direction R4 of the fourth alignment film 54. Similarly, the transmission axis P2 of the second polarizing plate 12 and the rubbing direction R3 of the third alignment film 52 are also set to have an orthogonal relationship.

  In the second liquid crystal display element 4 shown in FIGS. 6A and 6B, ZLI4792 (left-handed spiral pitch 100 μm) manufactured by Merck Co., Ltd. is used as the material of the liquid crystal 56, and the thickness of the liquid crystal layer is 5 μm. Yes.

  In the state which applied 2.4V to the liquid crystal 56 of the 2nd liquid crystal display element 4 shown by FIG. 6 (a) and (b), it installed in the light box and diffused the light of the fluorescent lamp with the diffusion plate. FIGS. 7A and 7B show the results of measuring the luminance of the central portion of the liquid crystal element from each direction when irradiating light in all directions. This measurement is carried out in an environment at room temperature of 25 degrees using a luminance measuring device (EZ-CONTRAST 160D) manufactured by ELDIM.

  FIGS. 7A and 7B show the o mode (o-mode) in the second liquid crystal display unit 4 and the e mode (e-mode) realized by the structure shown in FIG. 6A. The light transmission characteristics are shown. 7A and 7B, the intensity (luminance) of light rays directed from the display surface to the surroundings with respect to a certain point in the center of the display surface on the second liquid crystal display unit 4 is a contour line. It is represented. When observing the second liquid crystal display unit 4, a light beam having the brightness represented by the contour lines is directed to the observer. Further, polar angles 0 ° to 360 ° at which the observer is located are attached around the luminance distribution represented by the contour lines. Further, on the broken lines with polar angles of 0 ° and 180 °, an azimuth angle (an angle formed with respect to the perpendicular to the display surface) is 10 ° to 70 ° as an observation angle for observing the display surface of the second liquid crystal display unit 4. The reference circle corresponding to this observation angle of 10 ° to 70 ° is drawn as a concentric circle indicated by a broken line. The contour lines in the reference circle designated at each observation angle indicate the luminance distribution of the display surface observed at this observation angle.

  7A and 7B, the display surface area of the second liquid crystal display unit 4 is relatively large when viewed from the direction of the polar angle 0 ° at any of the observation angles (azimuth angles) of 10 ° to 70 °. It is displayed brightly with high brightness. When comparing FIG. 7A and FIG. 7B with respect to luminance, the o mode (o-mode) has a sufficiently high luminance and a clear display compared to the e mode (e-mode) as a comparative example. Is obtained.

  In addition, when viewed from the polar angle of 180 ° in any of the observation angles (azimuth angles) of 10 ° to 70 °, the display surface area of the second liquid crystal display unit 4 is shown in FIGS. 7 (a) and 7 (b). ) Are displayed with reduced brightness. Therefore, at a polar angle of 180 degrees, a clear display cannot be obtained, and the display surface of the second liquid crystal display unit 4 cannot be viewed. The viewing range based on this azimuth angle of 0 ° is a relatively narrow range within the entire polar angle range in the o mode (o-mode), whereas the e mode (e-mode) as a comparative example is used. ) Is a relatively wide range within the entire polar angle range. In other words, the permissible viewing range is relatively narrow in the o mode (o-mode) as compared to the e mode (e-mode), and as a result, display information can be protected over a wide range. Further, considering the azimuth angle, the o-mode (o-mode) similarly has a relatively narrow azimuth angle range that is visually recognized compared with the e-mode (e-mode). It becomes possible to protect.

  FIGS. 8A and 8B show the luminance in the horizontal direction and the vertical direction when 2.4 V is applied to the second liquid crystal display unit 4 in the e mode shown in FIG. 6A. 8 (c) and 8 (d) show a case where 2.4V is applied to the o-mode second liquid crystal display unit 4 shown in FIG. 6 (b). The viewing angle dependency of the luminance in the horizontal direction and the vertical direction is shown.

  Note that in FIGS. 8A and 8B and FIGS. 8C and 8D, the maximum luminance is drawn to be equal.

  From the measurement results shown in FIGS. 8A and 8B and FIGS. 8C and 8D, the following is found. In the e mode (e-mode) and the o mode (o-mode), when observing from one direction, for example, from the passenger seat side, as shown in FIGS. 8A and 8C, the e mode (e In -mode), the range in which the brightness decreases is narrow, whereas in o mode (o-mode), the range in which the brightness decreases is wide. Further, as shown in FIGS. 8B and 8D, in the e mode (e-mode), the vertical luminance does not decrease over a wide range, whereas in the o mode (o-mode), the luminance is low. It can be seen that the luminance is lowered over a wide range even when the low range is viewed over a wide range.

  Thus, it can be seen that in the o mode (o-mode) compared to the e mode (e-mode), the range that can be protected is widened and more preferable characteristics are obtained.

Example 4
FIG. 9 shows a liquid crystal display device according to the fourth embodiment. In the display device shown in FIG. 9, a third liquid crystal display unit 9 having a structure substantially the same as that of the second liquid crystal display unit 4 on the second liquid crystal display unit 4 having a diagonal size of 8 inches shown in FIG. 4. Is fixed. Since the first and second liquid crystal display units 2 and 4 are substantially the same as the structure shown in FIG. 4, the parts or portions shown in FIG.

In FIG. 9, an arrow P 4 shown in the fourth polarizing plate 96 indicates the transmission axis of the polarized light beam that can pass through the polarizing plate 96, and is shown in the fifth and sixth alignment films 92 and 94. The arrows R5 and R6 indicate the direction of the rubbing process, respectively. The third liquid crystal display unit 9 is similar to the second liquid crystal display unit 4 in the viewing range of the image displayed on the first liquid crystal display unit 2. And a wide-field mode for displaying an image displayed on the first liquid crystal display unit 2 over a wide viewing angle determined by the apparatus. That is, the third liquid crystal display unit 9 is provided with a transparent fifth substrate (not shown) on the third polarizing plate 46 of the second liquid crystal display unit 4, and faces the fifth substrate. Similarly, a transparent sixth substrate (not shown) is disposed. Similarly, a fourth polarizing plate 96 is formed on the outer surface of the sixth substrate.

  Transparent fifth and sixth electrodes (not shown) are formed on the inner surfaces of the fifth and sixth substrates facing each other, and the fifth and sixth electrodes are formed on the fifth and sixth electrodes. Six alignment films 92 and 94 are formed. A gap between the fifth and sixth alignment films 92 and 94 defined by the fifth and sixth substrates is filled with a third liquid crystal (not shown), and around the fifth and sixth substrates. Is provided with a seal portion (not shown) for supporting the fifth and sixth substrates, and the third liquid crystal 56 is a third liquid crystal display by the fifth and sixth substrates and the seal portion facing each other. It is sealed in the part 9.

  In the third liquid crystal display unit 9, the fifth alignment film 92 is rubbed along a direction R5 orthogonal to the transmission axis P3 of the third polarizing plate 46, and in a direction R6 orthogonal to the rubbing direction R5. The sixth alignment film 94 is rubbed. Further, the transmission axis P4 of the fourth polarizing plate 96 is set to be orthogonal to the rubbing direction R6 of the sixth alignment film 94.

  A case where the liquid crystal display device shown in FIG. 9 is used as a car navigation system will be described.

  In the liquid crystal display device shown in FIG. 9, when the display device is viewed from both the passenger seat and the driver seat when the vehicle is not traveling, the second and third liquid crystal display portions 4 and 9 have a voltage. Not applied. On the other hand, when the vehicle is running, when the display device is visible only from the passenger seat and not from the driver seat, the second and third liquid crystal display sections 4 and 9 have 2.6 V to 2 V respectively. A voltage of .8V is applied.

  In such a liquid crystal display device, if no voltage is applied to the second and third display units 4 and 9, the characteristics of the first liquid crystal display unit 2 are not particularly changed. However, the transmittance of the entire apparatus is about 70%. However, when a voltage is applied to the two second and third display units 4 and 9 at the same time, the transmittance when viewed from the right direction in the figure is 100% from the front when the luminance of the first display unit 2 is 100. The tilt angle can be set to 0.1 or less in the range of 30 ° to 60 °.

  As will be described later, in the second display unit 4 or the third display unit 9 alone, even if it decreases to about 1% at 30 °, it rises to about 4% at 50-60 ° and lowers the first liquid crystal. There is also a possibility that the display of the display unit 2 can be seen through.

  In the display device shown in FIG. 9, the applied voltages applied to the second and third display portions 4 and 9 can be made equal, and different voltages can be applied. The angle at which the luminance of the liquid crystal element is reduced most depends on the applied voltage. Therefore, for example, when it is desired to prevent viewing from an angle inclined by 20 ° to 40 ° with respect to the front, one of the liquid crystal display units 4 and 9 is set to 20 ° and the darkest angle is set to the other liquid crystal. The target condition can be obtained by setting the darkest angle of the element to 40 °. Also, regarding the configuration, the second and third liquid crystal display units 4 and 9 can be configured differently. It is also possible to answer more diverse requirements by giving Δnd different values for the two liquid crystal elements.

  FIG. 10 shows the viewing angle dependence of the transmittance in each of the second and third liquid crystal display units 4 and 9. In FIG. 10, the vertical axis represents the transmittance (relative value%), and the horizontal axis represents the viewing angle. The state in which the voltage V is not applied to the liquid crystal corresponds to normally white, and as shown by the transmittance distribution T0, the transmittance is gradually attenuated to a viewing angle of ± 70 ° at a viewing angle of 0 ° with a maximum transmittance. The When a voltage of 2.6 V is applied to the liquid crystal, as shown by the transmittance distribution T1, the transmittance is maximum at a viewing angle of −30 °, and gently 4% to a viewing angle of + 30 ° and a viewing angle of −70 °. The transmittance is attenuated to the extent. When a voltage of 2.8 V is applied to the liquid crystal, the transmittance is maximum at a viewing angle of −30 ° (maximum transmission compared to the transmittance distribution T1 of voltage 2.6 V) as shown in the transmittance distribution T2. Similarly, the transmittance is gradually attenuated to about 4% until the viewing angle + 30 ° and the viewing angle −70 °.

  Thus, in the case where only the second liquid crystal display unit 4 is provided alone in the display device, the transmittance is reduced only to about 4% around a viewing angle of 60 °. Although the transmittance of about 4% does not cause a problem under normal use conditions, the image displayed on the first liquid crystal display unit 2 below is transparent in an environment where the brightness is low such as use at night. There is a risk of seeing. For example, in the case of traveling without night room light for car navigation applications, the display of the first liquid crystal display element 2 may be seen through in the above configuration.

  FIG. 11 shows the viewing angle dependency of the transmittance in the display device in which the second and third liquid crystal display units 4 and 9 are provided as shown in FIG. FIG. 12 shows an enlarged part of the transmittance distribution shown in FIG.

  In a state where the voltage V is not applied to the liquid crystal, the light beam transmitted through the transmittance distribution T01 of the second liquid crystal display unit 4 is attenuated by the third liquid crystal display unit 9, and the transmittance distribution of the device itself is represented by a curve T02. The transmittance distribution is as shown. When a voltage of 2.6 V is applied to the liquid crystal, the light beam transmitted through the transmittance distribution T1 of the second liquid crystal display unit 4 is attenuated by the third liquid crystal display unit 9, and the transmittance of the device itself is obtained. The distribution is a transmittance distribution as shown by a curve T3. Similarly, when a voltage of 2.8 V is applied to the liquid crystal, the light beam transmitted through the transmittance distribution T2 of the second liquid crystal display unit 4 is attenuated by the third liquid crystal display unit 9 and transmitted by the device itself. The rate distribution is a transmittance distribution as shown by the curve T4.

  As is apparent from the transmittance distributions T3 and T4 shown in FIG. 11, the transmittance can be suppressed to 0.1% or less at a viewing angle of 30 ° or more. In the case of a transmittance of 0.1% transmittance, the display content is not seen through even during night driving, and the visibility from the driver side can be completely prevented. The function of preventing visual recognition during night driving is provided with second and third liquid crystal display units 4 and 9 for controlling the viewing angle with reference to FIG. Thus, it becomes clearer that the transmittance is suppressed to 0.1% or less by duplicating the panel.

  In the display structure shown in FIG. 9, it is clear that the voltages applied to the second and third liquid crystal display units 4 and 9 may be the same or different, and at night use. A voltage is applied to both the second and third liquid crystal display units 4 and 9 to make them active and limit the viewing angle. In daytime use, the second and third liquid crystal display units 4 and 9 A voltage may be applied to one side and only one of them may be activated to limit the viewing angle. When only one of the second and third liquid crystal display units 4 and 9 is active and the viewing angle is limited, the transmittance can be set large as apparent from FIGS. The display device can display information such as an image with sufficient luminance against external light.

  For example, one of the liquid crystal display units 4 and 9 is set to have a minimum point at a viewing angle of 30 °, and the other of the liquid crystal display units 4 and 9 is set to have a minimum point at a viewing angle of 50 °. By combining with the above, it is possible to realize a display device capable of narrowing the viewing angle and widening the range for protecting display information. In the liquid crystal display units 4 and 9, the same effect can be expected even if the thickness of the liquid crystal cell or the configuration of the liquid crystal material is changed.

  Further, in the structure in which the liquid crystal display units 4 and 9 are overlapped, it is preferable that at least one liquid crystal display unit 4 and 9 is configured in an o-mode. In the structure in which the liquid crystal display units 4 and 9 are superimposed, a wide range of angles can be protected by applying and adjusting different voltages to the two liquid crystal display units 4 and 9, but the e mode (e In the case of only -mode), it is difficult to secure a sufficiently wide angle.

(Example 5)
FIG. 13 shows a liquid crystal display device according to a fifth embodiment of the present invention. In the display device shown in FIG. 13, like the display device shown in FIG. 9, a second liquid crystal display unit 4 having a structure substantially the same as that of the second liquid crystal display unit 4 is formed on the second liquid crystal display unit 4 having a diagonal size of 8 inches. 3 liquid crystal display units 9 are fixed. In FIG. 13, the same parts or portions as those shown in FIG.

  In the liquid crystal display device shown in FIG. 13, unlike the display device shown in FIG. 9, in the second liquid crystal display unit 4, the rubbing direction R3 of the third alignment film 52 is the transmission axis of the second polarizing plate 12. The rubbing direction R4 of the fourth alignment film 54 is set parallel to the transmission axis P3 of the third polarizing plate 46. That is, the second liquid crystal display unit 4 is set to an orientation substantially the same as that of the first liquid crystal display unit 2. In the third liquid crystal display unit 9, the rubbing direction R 5 of the fifth alignment film 92 is set perpendicular to the transmission axis P 3 of the third polarizing plate 46. In the third liquid crystal display unit 9, the rubbing direction R 6 of the sixth alignment film 94 is set to be orthogonal to the transmission axis P 4 of the fourth polarizing plate 96 as in FIG. Here, it should be noted that the transmission axis P4 of the fourth polarizing plate 96 and the rubbing direction R6 of the sixth alignment film 94 are different from those in FIG.

  A case where the display device shown in FIG. 13 is used as a car navigation system will be described. In the display device shown in FIG. 13, the third display unit is responsible for the vertical viewing angle control of the image displayed on the first display device 2. With such an optical arrangement, it is possible to prevent the contents of the liquid crystal display screen from being viewed from the driver's seat while traveling, and at the same time, it is possible to prevent reflection on the windshield of the car.

  Further, by applying a voltage only to the second liquid crystal display unit 4 and using the third display unit 9 without applying a voltage, the luminance of the liquid crystal display unit can be kept high. Conversely, when the vehicle is not running, only the third display unit 9 is applied with a voltage, and the second display unit 4 is not applied with a voltage so that only the function of preventing reflection on the windshield of the car can be used. Is possible.

  The second and third liquid crystal display units 4 and 9 do not work independently, and the effect of the third liquid crystal display unit 9 can be enhanced by applying a voltage to the second liquid crystal display unit 4. The function of the second liquid crystal display unit 4 can be enhanced by applying a voltage to the third liquid crystal display unit 9. Therefore, it can be used according to the purpose.

(Example 6)
FIG. 14 shows a liquid crystal display device according to the sixth embodiment of the present invention. In the display device shown in FIG. 14, the second and third liquid crystal display units 4 and 6 are installed on the first liquid crystal display unit 2 having a diagonal size of 15 inches. In the display device shown in FIG. 14, the same parts or portions as those shown in FIG.

  The display device shown in FIG. 14 is suitable for use as a game as an example. The display device shown in FIG. 14 is different from the display device shown in FIG. 13, in the second liquid crystal display unit 4, the rubbing direction R <b> 3 of the third alignment film 52 is the transmission axis P <b> 2 of the second polarizing plate 12. The rubbing direction R4 of the fourth alignment film 54 is also set to be orthogonal to the transmission axis P3 of the third polarizing plate 46. In the third liquid crystal display unit 9, the rubbing direction R 5 of the fifth alignment film 92 is set so as to be orthogonal to the transmission axis P 3 of the third polarizing plate 46. In the third liquid crystal display unit 9, the rubbing direction R 6 of the sixth alignment film 94 is set to be orthogonal to the transmission axis P 4 of the fourth polarizing plate 96. Here, in comparison with the display device shown in FIG. 9, the rubbing directions R1 to R4 and the directions of the transmission axes P1 to P3 of the first and second display units 2 and 4 are the same. It should be noted that the rubbing directions R5 and R6 of FIG.

  In the display device having such an arrangement, the direction in which the viewing angle of the third display unit 9 is controlled is opposite to the direction in which the viewing angle of the second display unit 4 is controlled. And peeping from the left can be controlled independently. Such a function makes it possible to increase the versatility of, for example, an arcade game function.

(Example 7)
FIG. 15 shows a liquid crystal display device according to a seventh embodiment of the present invention. The display device shown in FIG. 15 has the same structure as the display device shown in FIG. 4, and the second liquid crystal display unit 4 is installed on the first liquid crystal display unit 2 having a diagonal size of 15 inches. Further, a half mirror 98 is disposed on the second liquid crystal display unit 4. In the display device shown in FIG. 15, the same parts or portions as those shown in FIG.

In the display device shown in FIG. 15, the first liquid crystal display unit 2 has a direction in which the transmittance has a large viewing angle dependency in the front direction in FIG. 15, and the second liquid crystal display unit 4 has the front direction. The direction in which the viewing angle depends greatly on the viewing angle.

  In order to create a state that is not seen by the peeping person but only seen by the user, the ratio of the left and right transmittances is increased. As another method, it is conceivable to make it difficult for a person looking into the display of the liquid crystal display device. Now, the visibility limit is defined as the minimum value of the transmitted light intensity of the device that can be visually recognized. It is effective to adjust the visibility limit so that it is stably between the left and right transmittances (in general, it is increased). For this purpose, it is effective to reflect the incident light without transmitting it. For this purpose, it is effective to use the half mirror 98.

  When the half mirror 98 was stretched on the second display unit 4, no light leaked to the side of the person peeping when voltage was applied, and the information displayed on the first display unit 2 was completely invisible.

  The display device shown in FIG. 15 can be used as an ATM. In the display device shown in the first embodiment, the display content may not be sufficiently concealed from the direction in which it is originally intended to be concealed. In such a case, it is possible to enhance the concealment effect by attaching a half mirror to the liquid crystal display surface. As the half mirror, an acrylic half mirror MRH-001 T10 manufactured by Mitsubishi Rayon Group Co., Ltd., Hyogo, etc. can be used. In this way, by attaching a half mirror, the reflected light on the surface can be kept above a certain value, and a sufficient concealing effect can be exhibited without duplicating the liquid crystal element for controlling the viewing angle. Become.

  The above-described display device is an example when used for ATM, and when a voltage is not applied, it is a normal viewing angle, and display contents can be seen from the periphery. On the other hand, when a voltage is applied, it is possible to prevent peeping to around 45 degrees left and right with the front front as the center by appropriately selecting the voltage. When the half mirror is not attached, the concealing effect at the time of voltage application is not sufficient, and the effect of preventing peeping is not enough, but it is possible to improve the effect of preventing peeping enough by attaching the half mirror. Become.

(Example 8)
FIG. 16 shows a liquid crystal display device according to an eighth embodiment of the present invention in which a lamp is installed on the front surface of the display unit in order to enhance the effect of preventing looking into. The liquid crystal display device 100 is not limited to the structure shown in FIG. 1 but includes the structure of the display device according to the embodiment shown in FIGS. 2, 4, and 13 to 15. As described above, the peep prevention can be realized by sufficiently reducing the transmitted light amount when viewed from one side of the display element with respect to the transmitted light amount when viewed from the other side. However, as another factor, it can be realized by making the ratio of transmitted light and reflected light on the surface appropriate. In the case of nighttime when the reflected light becomes very small, the display content may be visually recognized even if the transmitted light becomes weak. For example, when the navigation system is used at night, the first display unit 2 may be seen through when viewed from the driver's seat even when the half mirror 98 is attached. Even if the liquid crystal panel is doubled, the lower liquid crystal panel may be seen through slightly. This phenomenon can be solved by arranging a light source such as a small fluorescent tube or LED in the vicinity of the surface of the optical element opposite to the driver's seat. That is, the lamp 102 can be installed as a light source that generates reflected light on the opposite side of the display unit from the direction in which it is desired to prevent peeping, and the reflected light can be generated to make the contents of the liquid crystal display device 100 invisible. .

Example 9
Using one second liquid crystal display unit 4 shown in FIG. 17 (a) and one liquid crystal display unit 9 shown in FIG. 17 (b), a display device having a structure shown in FIG. ) And.) Was created. For the second liquid crystal display unit 4 shown in FIG. 17A, ZLI-4792 (UR009) is used as the liquid crystal material, and for the third liquid crystal display unit 9 shown in FIG. As a material, ZLI-4792 (US009) is used. The two materials differ only in the direction of optical rotation of the added optically active substance.

  For comparison, a display device (referred to as a prototype device (B)) having the structure shown in FIG. 18 was created by using the two second liquid crystal display units 4 shown in FIG. In the display device (prototype device (A)) shown in FIG. 9, the rubbing direction R5 is different from the rubbing direction R3, and the rubbing direction R6 is different from the rubbing direction R4. The prototype device (B)) differs in that the rubbing directions R5 and R6 are substantially the same as the rubbing directions R3 and R4, respectively.

  As the first liquid crystal display element portion 2, a commercially available 8-inch wide liquid crystal monitor (surface brightness 400 cd / m 2) for car navigation was used. The sizes of the liquid crystal display units 4 and 9 were selected so that the display area was equal to the display area of the liquid crystal monitor as the first display device 2.

  A normal image (natural image) is displayed on the first liquid crystal display unit 2 of the prototype devices (A) and (B) installed horizontally, and the observer displays the image on the panel from a position inclined 30 ° left and right from the front of the panel. Observed images were observed. When no voltage was applied, the image on the screen could be satisfactorily observed in both prototype devices (A) and (B). Next, the liquid crystal display unit 4 applies a signal voltage so that the darkest part is at the left end of the 8-inch panel when viewed from the right side 30 °, and the liquid crystal display unit 9 is at the right end when viewed from the right side 30 °. A signal voltage was applied so that the darkest part was present. The image at the center of the panel was observed under such conditions.

In the prototype device (B), an image was observed well from the left 30 ° under a fluorescent lamp or in the daytime window, but no image was observed from the right 30 °. On the other hand, when the room was a dark room (equivalent to driving at night), the contents could be distinguished depending on the image (in the case of a bright image). In the case of the prototype device (A), the contents of any image could not be distinguished even when the room was made a dark room. (Except when staring for more than 1 minute)
As described above, the optically active substance used in the second and third display units 4 and 9 and the rubbing direction are changed so that the directions of the twist angles of the two liquid crystal elements are different, thereby preventing peeping. The performance can be greatly improved. That is, by appropriately selecting the liquid crystal material used for the second and third display portions 4 and 9, the second and third display portions 4 and 9 can be given twist structures in opposite directions. it can. Further, the optically active substances having different optical rotatory properties that induce twist directions opposite to each other can be obtained by the optically active substances added to the liquid crystal materials of the second and third display portions 4 and 9.

  In the above-described embodiment, the transmission type is described, but it is obvious that it can be applied to the reflection type. That is, regarding the application of the present invention, there is no difference depending on whether the liquid crystal display device (LCD) to be applied is a transmissive type or a reflective type. However, when the liquid crystal display device (LCD) is of a reflective type, the incident polarized light passes through the liquid crystal layer and is reflected as it is, and then passes through the liquid crystal layer again, so that it passes through the liquid crystal layer twice. For this reason, it is necessary to adjust the thickness of the retardation cell to 1/2. In the liquid crystal display device (LCD) according to the present invention, incident light passes through the liquid crystal element, passes through the polarizing plate, then temporarily exits the liquid crystal element, then enters the liquid crystal display device (LCD), and further passes through the polarizing plate. Linearly polarized light enters the liquid crystal element. For this reason, even in the reflection type, the function of the liquid crystal element is not changed from that of the transmission type, and therefore the structure of the liquid crystal element is not changed between the transmission type and the reflection type.

1 is a cross-sectional view schematically showing a liquid crystal display device according to an embodiment of the present invention. It is a schematic diagram which shows roughly the optical arrangement | positioning of the liquid crystal display device shown by FIG. It is a schematic diagram which shows roughly the position of the display apparatus at the time of using the display apparatus shown by FIG. 2, a user, and the person who peeps. It is a schematic diagram which shows roughly the optical arrangement | positioning of the display apparatus which concerns on 2nd Example of this invention. It is a schematic diagram for demonstrating the positional relationship of a display part at the time of applying the display apparatus shown by FIG. 4 to a car navigation system, a driver | operator, and a passenger. FIG. 5 is a schematic diagram schematically showing an optical arrangement of a second liquid crystal display unit adopting a configuration of an e mode (e-mode) and an o mode (o-mode) in the display device shown in FIG. 4. FIG. 7 is a contour diagram showing light transmission characteristics of a liquid crystal display unit configured in an e mode (e-mode) and an o mode (o-mode) in the liquid crystal display device shown in FIG. 6. (A)-(d) is a graph which shows the viewing angle dependence of the brightness | luminance of the left-right direction and the up-down direction in the 2nd liquid crystal display part shown by Fig.6 (a) and (b). It is a schematic diagram which shows schematically the liquid crystal display device based on 4th Example of this invention. 10 is a graph showing the viewing angle dependence of the transmittance in each of the liquid crystal display units shown in FIG. 9. It is a graph which shows the viewing angle dependence of the transmittance | permeability in the display apparatus in which the 2nd and 3rd liquid crystal display part is provided as FIG. 9 shows. It is a graph which expands and shows a part of transmittance | permeability distribution shown by FIG. It is a schematic diagram which shows schematically the liquid crystal display device based on 5th Example of this invention. It is a schematic diagram which shows schematically the liquid crystal display device based on 6th Example of this invention. It is a schematic diagram which shows schematically the liquid crystal display device based on the 7th Example of this invention. It is a schematic diagram which shows schematically the liquid crystal display device based on the 8th Example of this invention. (A) And (b) is a top view which shows the liquid crystal display part which has a different rubbing direction integrated in the display apparatus based on the 9th Example of this invention. It is a schematic diagram which shows schematically the liquid crystal display device based on 9th Example of this invention.

Explanation of symbols

  2. . . 1. first liquid crystal display unit; . . 2nd liquid crystal display part, 6, 8, 42, 44. . . 8. transparent substrate; . . Third liquid crystal display unit 10, 12, 46. . . Polarizing plate, 14, 48, 50. . . Transparent electrode 16, 20, 52, 54. . . Alignment film, 18. . . Common electrode, 24. . . Liquid crystal layer, 30. . . Liquid crystal drive circuit,

Claims (20)

First and second substrates opposed to each other, wherein at least the second substrate on the display surface side is formed transparently; and
A plurality of first and second electrodes corresponding to each of the plurality of pixels formed on the first and second substrates;
First and second alignment films formed on inner surfaces of the first and second substrates facing each other;
A first liquid crystal layer filled between the first and second alignment films and aligned according to the alignment characteristics of the first and second alignment films; and at least provided on the second substrate on the display surface side A first polarizing plate,
A first liquid crystal display unit comprising:
A third transparent substrate provided on the first polarizing plate and a fourth transparent substrate disposed to face the third transparent substrate;
Third and fourth transparent electrodes formed on inner surface regions of the third and fourth substrates facing each other corresponding to the display region of the first liquid crystal display unit;
Third and fourth alignment films respectively formed on opposing surfaces of the third and fourth transparent substrates;
A second liquid crystal layer filled between the third and fourth alignment films and aligned according to the alignment characteristics of the third and fourth alignment films; and provided on the display surface side of the fourth substrate. A second polarizing plate,
A second liquid crystal display unit comprising:
A display device comprising:     2. The display device according to claim 1, wherein the rubbing direction of the third alignment film disposed in the vicinity of the first polarizing plate is substantially perpendicular to the transmission axis of the first polarizing plate. .     The display device according to claim 2, wherein the second liquid crystal unit is a TN liquid crystal element. The first substrate is transparent, and a third polarizing plate is provided on the outer surface of the transparent substrate, and illumination light rays are externally transmitted to the first liquid crystal display unit through the third polarizing plate. When the thickness of the liquid crystal layer of the second liquid crystal display unit is d μm and the refractive index anisotropy of the liquid crystal layer is Δn,
Δnd = a × COS ⁻¹ θ
(A is 0.5 ± 0.1, and θ is an arbitrarily set angle.)
The display device according to claim 3, wherein a relationship represented by:     2. A driving unit that drives the second liquid crystal display unit with a voltage of 40% to 80% of a saturation voltage of the liquid crystal display unit when the second liquid crystal display unit is driven. Display device. First and second substrates opposed to each other, wherein at least the second substrate on the display surface side is formed transparently; and
A plurality of first and second electrodes corresponding to each of a plurality of pixels formed on the first and second substrates;
First and second alignment films formed on inner surfaces of the first and second substrates facing each other;
A first liquid crystal layer filled between the first and second alignment films and aligned according to the alignment characteristics of the first and second alignment films; and at least provided on the second substrate on the display surface side A first polarizing plate,
A first liquid crystal display unit comprising:
A third transparent substrate provided on the first polarizing plate and a fourth transparent substrate disposed to face the third transparent substrate;
Third and fourth transparent electrodes formed on inner surface regions of the third and fourth substrates facing each other corresponding to the display region of the first liquid crystal display unit;
Third and fourth alignment films respectively formed on opposing surfaces of the third and fourth transparent substrates;
A second liquid crystal layer filled between the third and fourth alignment films and aligned according to the alignment characteristics of the third and fourth alignment films; and provided on the display surface side of the fourth substrate. A second polarizing plate,
A second liquid crystal display unit comprising:
A fifth transparent substrate provided on the second polarizing plate and a sixth transparent substrate disposed opposite to the fifth transparent substrate;
Fifth and sixth transparent electrodes formed on inner surface regions of the fifth and sixth substrates facing each other corresponding to the display region of the first liquid crystal display unit;
Fifth and sixth alignment films respectively formed on opposing surfaces of the fifth and sixth transparent substrates;
A third liquid crystal layer filled between the fifth and sixth alignment films and aligned according to alignment characteristics of the fifth and sixth alignment films; and a display surface side of the sixth substrate. A third polarizing plate,
A third liquid crystal display unit comprising:
A display device comprising:     7. The display device according to claim 6, wherein the rubbing direction of the third alignment film disposed in the vicinity of the first polarizing plate is substantially perpendicular to the transmission axis of the first polarizing plate. .     The display device according to claim 6, wherein a rubbing direction of the fifth alignment film disposed in the vicinity of the second polarizing plate is substantially perpendicular to a transmission axis of the second polarizing plate. .     The rubbing direction of the third alignment film disposed in the vicinity of the first polarizing plate is substantially perpendicular to the transmission axis of the first polarizing plate, and in the vicinity of the second polarizing plate. The display device according to claim 6, wherein a rubbing direction of the fifth alignment film disposed is substantially perpendicular to a transmission axis of the second polarizing plate.     7. The display device according to claim 6, wherein the second and third liquid crystal display units have the same direction of large viewing angle dependency of transmittance during halftone display.   7. The display device according to claim 6, wherein the second and third liquid crystal display units are different in the direction in which the viewing angle dependency of the transmittance at the time of halftone display is large.     The directions in which the second viewing angle and the third viewing angle of the second and third liquid crystal display sections are largely dependent on the viewing angle coincide with each other, and the liquid crystal materials constituting the second and third liquid crystal layers are twisted in opposite directions. 9. The display device according to claim 8, wherein the display device has a structure.     9. The display according to claim 8, wherein the optically active substance added to the liquid crystal material constituting the second and third liquid crystal layers is an optically active substance having different optical rotations that induce twist directions opposite to each other. apparatus.   The display according to claim 6, 7, 8, 8, or 9, wherein the second and third liquid crystal display units have different viewing angle dependency directions in the halftone display. apparatus.     The display device according to claim 14, wherein directions in which the transmittance has a large viewing angle dependency are orthogonal to each other.     15. The display device according to claim 14, wherein the viewing angle dependency direction of the transmittance at the time of halftone display of the second and third liquid crystal display units is opposite.     The display device according to claim 1, wherein a half mirror is attached to a surface of the third polarizing plate of the third liquid crystal display unit.     The display device according to claim 1, wherein the display unit of the display device is irradiated to reflect a reflected light beam from a surface thereof in a specific direction.     7. The vehicle navigation system according to claim 1, wherein the display unit of the display device is always visible on the passenger seat side, and the display unit of the display device is not visually recognized at a predetermined time on the driver side. Display device.     The display device according to claim 1, wherein a light beam emitted from a display unit of the display device is prevented from being reflected on a windshield.

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