JP2008203446A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent display from becoming hardly viewed by contrast difference caused by switching of a visual angle when the visual angle is switched by a visual angle control element, in a display device provided with the visual angle control element capable of changing angle distribution of transmission light and a display element performing display utilizing the transmission light. <P>SOLUTION: In the display device 1, the visual angle control element 10 is provided with a pair of light transmissive substrates 4 and 6 having light transmissive electrodes 5 and 7 formed on the inner surfaces thereof, a liquid crystal layer 9 held by an opening between the pair of light transmissive substrates 4 and 6 and an acicular filler 8 dispersed and held by an opening between the pair of light transmissive substrates 4 and 6 and aligned in nearly one direction in the planes of the substrates and angle distribution of the transmission light is changed according to the change of voltage given to the liquid crystal layer 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device that can change the viewing angle of displayed characters, figures, and the like.

  In recent years, display devices such as liquid crystal display devices have been widely used in portable devices such as mobile phones. This type of display device is often used in a crowded vehicle. There are cases where contents such as confidential information and personal information that are not desired to be known to others are displayed by operating the portable device in such a place where there are many others nearby. In that case, it is convenient if the operator can read the display information and can switch the display state so that the display information cannot be read from the surrounding people.

  As this type of display device, one in which a viewing angle control element is added before and after the display device is known (see, for example, Patent Document 1). FIG. 7 is a schematic cross-sectional view of a liquid crystal display device in which a viewing angle control element 51 is added to the liquid crystal display element 50. A viewing angle control element 51 is inserted between the surface light source composed of the light source 57 and the light guide plate 52 and the liquid crystal display element 50. The viewing angle control element 51 is composed of a polymer dispersed liquid crystal (see, for example, Patent Document 2), and a transparent solid material 54 and a transparent solid material 54 are disposed between a pair of transparent substrates (not shown) having a transparent electrode formed on the inner surface. Liquid crystal droplets 53 dispersed in the conductive solid material 54 are sandwiched.

  FIG. 7 shows a state in which no voltage is applied to the viewing angle control element 51, and the liquid crystal molecules in the liquid crystal droplets 53 are oriented in random directions. The light guide plate 52 on which the light from the light source 57 is incident emits substantially parallel light 56 having directivity substantially perpendicular to the emission surface. The viewing angle control element 51 to which the substantially parallel light 56 is incident scatters light at the domain boundary of the liquid crystal molecules in the liquid crystal droplets 53 facing the random direction and the boundary between the liquid crystal droplets 53 and the transparent solid material 54. To do. Therefore, the directivity of the transmitted light 55 emitted from the viewing angle control element 51 decreases and enters the liquid crystal display element 50. Since light in an oblique direction is incident on the liquid crystal display element 50, characters, images, and the like displayed on the liquid crystal display element 50 can be viewed from the oblique direction.

  FIG. 8 shows a state in which a voltage is applied to the viewing angle control element 51. The liquid crystal molecules of the viewing angle control element 51 are aligned in the electric field direction. As a result, the domains in the liquid crystal droplets 53 disappear, and light scattering at the interface between the liquid crystal droplets 53 and the transparent solid material 54 is also reduced. Therefore, the substantially parallel light 56 having directivity emitted from the light guide plate 52 is not scattered by the viewing angle control element 51, and transmitted light 55 having high directivity enters the liquid crystal display element 50. As a result, characters, images, and the like displayed on the liquid crystal display element 50 are difficult to see from an oblique direction and can be viewed from a direction perpendicular to the display surface. In this way, the viewing angle of the display light 59 emitted from the liquid crystal display element 50 can be controlled.

  FIG. 9A is a graph comparing the directivity of light emitted from the viewing angle control element 51 when an electric field is applied to the viewing angle control element 51 and when it is not applied. The display surface of the liquid crystal display element 50 is regarded as a clock face. The scales at 9 o'clock 3 o'clock and 12 o'clock 6 o'clock represent the tilt angle from the perpendicular to the display surface. The fall angle increases as you move away from the center. That is, the inclination angle becomes larger. In each graph, when no electric field is applied and when an electric field is applied, the transmitted light intensity at an angle indicating the maximum transmitted light intensity of the transmitted light 55 is defined as 100%. It is a curve. Graph Wa shows the viewing angle characteristics when no electric field is applied, and graph Wb shows the viewing angle characteristics when the electric field is applied. As apparent from FIG. 9A, the viewing angle characteristics when no electric field is applied are wide, and the viewing angle characteristics when an electric field is applied are narrow. All of them have a uniform distribution in the circumferential direction.

FIG. 9B is a graph comparing the intensity distribution of the transmitted light 55 emitted from the viewing angle control element 51 when an electric field is applied to the viewing angle control element 51 and when it is not applied. The horizontal axis represents the 9 o'clock 3 o'clock direction, and the vertical axis represents the transmitted light intensity. Graph Ia shows transmitted light characteristics when no electric field is applied, and graph Ib shows transmitted light characteristics when an electric field is applied. Obviously, when no electric field is applied, the transmitted light 55 is diffused in an oblique direction and the light intensity is weak. On the other hand, when an electric field is applied, the directivity is high and the light intensity in the vertical direction is high. The broken line Xa indicates 80% of the transmitted light intensity with respect to the maximum transmitted light intensity when no electric field is applied, and corresponds to the graph Wa in FIG. Similarly, a broken line Xb indicates 80% of the transmitted light intensity with respect to the maximum transmitted light intensity when an electric field is applied, and corresponds to the graph Wb in FIG.
JP 2005-265920 A JP 2002-268050 A

  However, as shown in FIGS. 9A and 9B, when no voltage is applied to the viewing angle control element 51, the transmitted light 55 is emitted isotropically in an oblique direction. The intensity of the light 55 is reduced. Therefore, there is a problem that the entire display becomes dark. Further, when a voltage is applied to the viewing angle control element 51, transmitted light 55 having a narrow viewing angle range is applied to the liquid crystal display element 50, and the display is displayed on the liquid crystal display element 50 by a difference in brightness in the vertical and horizontal directions toward the display surface. There has been a problem that it is difficult to visually recognize the letters, figures and the like.

  In order to solve the above-described problems, the present invention includes a viewing angle control element that can change the angle distribution of transmitted light and a display element that performs display using the transmitted light in a stacked manner. In the display device, the viewing angle control element includes a pair of translucent substrates each having a translucent electrode formed on an inner surface thereof, and a polymer dispersed liquid crystal layer sandwiched between the pair of translucent substrates. And a needle-like filler dispersed and sandwiched in the gap between the pair of translucent substrates and oriented in substantially one direction within the plane of the substrate, according to a change in voltage applied to the liquid crystal layer, The display device is characterized in that the angle distribution of the transmitted light changes.

  The liquid crystal layer is a polymer dispersed liquid crystal layer.

  The transmitted light is a display device in which the change in angular distribution in the direction orthogonal to the substantially one direction is smaller than that in the approximately one direction.

  In addition, the substantially one direction is a display device that is approximately 9 o'clock and 3 o'clock when viewed from the viewing direction of the display.

  In addition, a visual angle control circuit for driving the visual angle control element, and a luminance control circuit for controlling the display luminance of the display element, and a change in voltage applied to the visual angle control element by the visual angle control circuit Accordingly, a display device in which the display brightness of the display element is controlled by the brightness control circuit is provided.

  The present invention is a display device in which a viewing angle control element and a display element are stacked, and the viewing angle control element includes a pair of translucent substrates having translucent electrodes formed on the inner surface, and a high height sandwiched between the substrates. A molecule-dispersed liquid crystal layer and a needle-like filler dispersed and sandwiched between the substrates and oriented in one direction within the substrate surface are applied, and a voltage is applied between the electrodes to transmit the viewing angle control element. The angular distribution of transmitted light was controlled. As a result, before and after changing the viewing angle of the display, the brightness difference of the display is reduced and the light intensity is reduced with respect to a specific direction when the narrow viewing angle state is set, and the light intensity with respect to other directions. Has the advantage that the display can be made easier to see without lowering.

<Example 1>
FIG. 1 is a perspective view showing Example 1 of a display device 1 according to the present invention. A display element is composed of the display panel 2 and the surface light source 3. A viewing angle control element 10 is inserted between the display panel 2 and the surface light source 3. The viewing angle control element 10 is composed of a pair of translucent substrates 4 and 6 having translucent electrodes 5 and 7 formed on the inner surface, and a needle-like filler 8 and a liquid crystal layer 9 sandwiched between these substrates. ing. The acicular filler 8 is oriented substantially in one direction within the substrate surface. In this embodiment, the long axis of the needle-like filler 8 is oriented in the 9 o'clock 3 o'clock direction.

  The translucent electrodes 5 and 7 are connected so that a voltage can be supplied from the power source 11 via the switch S. In the state where the switch S is turned off and no electric field is applied to the liquid crystal layer 9, the alignment directions of the liquid crystal molecules 12 are not aligned. The liquid crystal molecules 12 constitute a domain, and light is scattered at the interface. As a result, the transmitted light passing through the viewing angle control element 10 is scattered in any direction, and the display displayed on the display panel 2 can be viewed from any direction. When the switch S is turned on and an electric field is applied to the liquid crystal layer 9, the liquid crystal molecules 12 of the liquid crystal layer 9 are aligned in the electric field direction. As a result, the domain due to the liquid crystal molecules 12 disappears in the liquid crystal layer 9, and the scattering state by the liquid crystal is eliminated. However, the needle-like filler 8 is oriented in the 9 o'clock 3 o'clock direction. Light is scattered at the interface due to the difference in refractive index between the needle-like filler 8 and the liquid crystal layer 9. This scattered light is strongly scattered in the direction perpendicular to the needle-like filler 8, that is, in the direction of 12:00 to 6 o'clock. As a result, the viewing angle of display on the display panel 2 is wide at 12 o'clock and 6 o'clock and narrow at 9 o'clock and 3 o'clock. That is, it becomes difficult to visually recognize the display from 9 o'clock to 3 o'clock.

  Thus, by the visual angle control for turning on and off the switch S, the orientation direction of the needle filler 8 is more than the change in the angular distribution of transmitted light at 12 o'clock in the 6 o'clock direction perpendicular to the orientation direction of the needle filler 8. The change in angular distribution in the 9 o'clock and 3 o'clock direction can be increased. And compared with the case where viewing angle control is performed by a viewing angle control element that does not form the needle filler 8, the switch S is turned on to narrow the display viewing angle, and the switch S is turned off to widen the display viewing angle. The difference in display brightness between the state and the state can be reduced, and the visibility of the display can be improved because the narrow direction of the viewing angle in the narrow viewing angle state is only the specific direction.

  In the first embodiment, a glass substrate or a transparent plastic substrate is used as the translucent substrates 4 and 6 of the viewing angle control element 10. The translucent electrodes 5 and 7 were formed by sputtering ITO (indium tin oxide). In addition to ITO, SnO2, ZnO2, In2O3, or a mixture thereof can be formed by sputtering or electron beam evaporation. The translucent electrodes 5 and 7 were formed on the entire surface of the translucent substrates 4 and 6. As the needle-like filler 8, a transparent or white material such as titanium oxide, silicon oxide, glass material or the like is used. The acicular filler 8 has a refractive index different from that of the liquid crystal layer 9. The acicular filler 8 has a shape in which the major axis is extremely large with respect to the minor axis. The minor axis is preferably 1 to 20 μm, and the major axis is preferably 10 to 500 μm. Considering the light diffusibility of the liquid crystal, the minor axis is preferably 5 to 20 μm. The acicular filler 8 also functions as a spacer that defines a gap between the translucent substrates 4 and 6. Note that it is not necessary for all the needle-like fillers 8 to be oriented in the same direction, and it is sufficient if they are oriented in a specific direction on average.

  As the liquid crystal constituting the liquid crystal layer 9, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal and a mixture thereof, or DSM (dynamic scattering mode) liquid crystal can be used. In short, it is sufficient that the light scattering state and the non-scattering state can be switched by applying an electric field or supplying a current. Further, for example, a polymer-dispersed liquid crystal having a network structure in which liquid crystal droplets are dispersed in a transparent solid substance can be used. A polymerizable composition can be used as the transparent solid substance, and a nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal, or the like can be used as the liquid crystal. When no electric field is applied to the liquid crystal layer, the liquid crystals in the droplets are randomly oriented. In this state, a refractive index difference occurs between the liquid crystal domains to scatter light, and light is also scattered by a refractive index difference between the droplet and the transparent solid substance. When an electric field is applied to the liquid crystal layer, the liquid crystal in the droplets is aligned in the direction of the electric field, the boundaries between the liquid crystal domains disappear, and the refractive index difference disappears. As a result, the liquid crystal in the droplet becomes transparent. Further, if the ordinary light refractive index of the liquid crystal and the refractive index of the transparent solid material are matched, the difference in refractive index at the boundary between the liquid crystal droplet and the transparent solid material can be eliminated when an electric field is applied. This also eliminates light scattering at the boundary.

  A transmissive liquid crystal display element is used as the display element. The liquid crystal display element may be any type such as a TN type, an STN type, and a horizontal electric field type. A reflective liquid crystal display element can be used as the display element. In this case, the viewing angle control element is arranged in the display viewing direction of the liquid crystal display element. The display element is not limited to a liquid crystal display element. Any display element such as a plasma display, an EL display element, and an organic EL display element can be used. In addition, when using self-luminous display elements, such as a plasma display, the viewing angle control element 10 is installed in front of the viewing direction of these display elements.

  The surface light source 3 can be composed of a light source including a planar light guide plate and a light emitting diode for irradiating light from the side surface. In addition, an optical sheet made of a prism sheet or the like and a light diffusion plate can be stacked, and an EL light emitting element or a cold cathode tube can be installed below the optical sheet.

  In Example 1, the translucent electrodes 5 and 7 were formed on the entire inner surfaces of the translucent substrates 4 and 6 corresponding to the display area of the display panel 2. This may be formed such that the translucent electrodes 5 and 7 are striped electrodes, and the translucent electrode 5 and the translucent electrode 7 are orthogonal to each other, or formed only in a specific region of the display region. May be. If the striped electrodes are orthogonal to each other, a mosaic pattern can be applied to the display of the viewing angle control range.

<Example 2>
2 and 3 are schematic cross-sectional views showing Example 2 of the display device using the polymer dispersion type liquid crystal layer 9, and FIG. 2 shows a state in which no electric field is applied to the liquid crystal layer 9. FIG. Represents a state in which an electric field is applied to the liquid crystal layer 9. The same portions or portions having the same function are denoted by the same reference numerals.

  In FIG. 2, the viewing angle control element 10 has a liquid crystal layer 9 and a needle-like filler 8 sandwiched between a pair of translucent substrates 4 and 6 having translucent electrodes 5 and 7 formed on the inner surface. The liquid crystal layer 9 is composed of a transparent solid material 14 and droplets 13 containing liquid crystal. The transparent solid substance 14 is composed of a polymerizable composition part, and the droplets 13 are dispersed in the transparent solid substance 14 having a three-dimensional network structure. The droplet 13 contains a nematic liquid crystal having positive dielectric anisotropy. The acicular filler 8 is made of titanium oxide, and has a minor axis of 5 μm to 20 μm and a major axis of 10 to 500 μm. The needle-like filler 8 has a major axis oriented in a direction substantially perpendicular to the paper surface.

  The display panel 2 is a transmissive TN liquid crystal panel, and description of a polarizing plate and the like is omitted. A light guide plate 15 and a light source 16 for irradiating light to the light guide plate 15 are installed on the opposite side of the viewing angle control element 10 from the display panel 2. The light guide plate 15 emits substantially parallel light 20 perpendicular to the surface of the viewing angle control element 10. The viewing angle control element 10 receives substantially parallel light 20 and emits transmitted light 21 whose viewing angle direction is controlled. The display panel 2 receives the transmitted light 21 and emits the display light 22 modulated into characters, images, and the like. The display panel 2, the light guide plate 15, and the light source 16 constitute a display element. The translucent electrodes 5 and 7 are electrically connected to the power source 11 via the switch S.

  In FIG. 2, since the switch S is off, no electric field is applied to the liquid crystal layer 9. The liquid crystal molecules in the droplets 13 dispersed in the transparent solid substance 14 are oriented in random directions. The substantially parallel light 20 incident from the light guide plate 15 is scattered at the liquid crystal domain boundary in the droplet 13 and at the interface between the transparent solid substance 14 and the droplet 13. Further, the substantially parallel light 20 incident from the light guide plate 15 is also scattered by the needle filler 8. Scattering by the acicular filler 8 is stronger in the short axis direction than in the long axis direction.

  In FIG. 3, since the switch S is on, an electric field is applied to the liquid crystal layer 9. Then, the liquid crystal molecules of the droplet 13 are directed in the electric field direction. For this reason, the domain of the liquid crystal disappears, and the difference in refractive index with respect to the incident direction of light at the interface between the transparent solid substance 14 and the droplet 13 disappears. As a result, the incident substantially parallel light 20 is predominantly scattered by the needle filler 8. Therefore, more light is scattered in the direction perpendicular to the needle-like filler 8 than in the direction parallel to the needle-like filler 8.

  FIG. 4A shows the viewing angle characteristic of the transmitted light 21 emitted from the viewing angle control element 10 shown in FIGS. In the display device 1 shown in FIGS. 2 and 3, the left-right direction on the paper surface is the 12 o'clock 6 o'clock direction, and the front and back direction of the paper surface is the 9 o'clock 3 o'clock direction. The graphs Wx and Wy shown in FIG. 4 show the directivity of the transmitted light 21 emitted from the viewing angle control element 10 when no electric field is applied to the liquid crystal layer 9 and when an electric field is applied. To express. The graduations in the 9 o'clock 3 o'clock direction and the 12 o'clock 6 o'clock direction represent the tilt angle from the perpendicular to the substrate surface of the viewing angle control element 10, and the tilt angle increases from the center toward the periphery. The scale is an arbitrary unit. Each graph is an equal light intensity curve connecting points of light intensity of 80%, with light intensity at an angle indicating the maximum transmitted light intensity being 100% when no electric field is applied and when an electric field is applied.

  4A, the graph Wx when no electric field is applied has a circular shape, and the transmitted light 21 emitted from the viewing angle control element 10 has a substantially uniform intensity in the circumferential direction. On the other hand, the graph Wy when the electric field is applied is elliptical. That is, the transmitted light 21 has a wide viewing angle range at 12 o'clock and 6 o'clock and a narrow viewing angle range at 9 o'clock and 3 o'clock. As a result, characters, images, and the like displayed on the display panel 2 are difficult to see from 9 o'clock to 3 o'clock. However, since the viewing angle range is wide in the 12 o'clock direction, the difference in brightness of the display light 22 emitted from the display panel 2 is reduced. Therefore, the visibility of display is improved.

  FIG. 4B shows the transmitted light intensity distribution of the transmitted light 21 emitted from the viewing angle control element 10 shown in FIGS. The direction of the display device 1 is as described with reference to FIG. The horizontal axis represents the 9 o'clock 3 o'clock direction, and the vertical axis represents the intensity of transmitted light emitted from the viewing angle control element 10, which is an arbitrary unit. Graph Ix represents the transmitted light intensity characteristics when no electric field is applied to the liquid crystal layer 9, and graph Iy represents the transmitted light intensity characteristics when the electric field is applied. Obviously, the transmitted light 21 is diffused in an oblique direction when no electric field is applied. Directivity is strong when an electric field is applied, and the intensity of transmitted light 21 in the vertical direction is greater than when no electric field is applied. However, even when a voltage is applied to the viewing angle control element 10 to limit the viewing angle range in the 9 o'clock direction at 9 o'clock, the viewing angle range in the 12 o'clock direction is sufficiently wide and no electric field is applied. It has transmitted light intensity characteristics at the same level as time. Thereby, the character, figure, etc. which were displayed on the display panel 2 can be visually recognized easily.

  In the above description, the direction for limiting the viewing angle range is the 9 o'clock 3 o'clock direction, but the present invention is not limited to this. By selecting the orientation direction of the acicular filler 8 of the viewing angle control element 10, the viewing angle limiting direction can be set to an arbitrary direction. Further, a TN liquid crystal display panel is used as the display panel 2, and the viewing angle range of the display light 22 is set more effectively by combining the unique viewing angle direction of the TN liquid crystal display panel and the viewing angle limiting direction of the viewing angle control element 10. can do.

  In the above description, components and functions that are not particularly described are the same as those in the first embodiment, and a description thereof is omitted here.

  Next, an example of a method for manufacturing the viewing angle control element 10 in the first embodiment or the second embodiment will be described. First, translucent substrates 4 and 6 made of a pair of glasses or the like are prepared. Translucent electrodes 5 and 7 made of ITO are formed on the substrate surface by electron beam evaporation or sputtering. Next, the needle-like filler 8 is attached to the surface of the one translucent substrate 4 on which the translucent electrode 5 is formed. The acicular filler 8 is attached by an offset printing method. Specifically, a polyimide solution in which acicular filler is dispersed in a polyimide solution is prepared. This solution is applied to a roll-shaped original plate. Next, the applied polyimide is transferred from the roll-shaped original plate to a cylindrical blanket, and further transferred from the cylindrical blanket to the translucent substrate 4 for printing. Then, a polyimide film in which the major axes of the needle fillers 8 are aligned in the rotation direction of the cylindrical blanket is printed. Next, the polyimide film is cured by irradiating the translucent substrate 4 with ultraviolet light or baking the translucent substrate. Next, a seal for encapsulating the liquid crystal layer 9 is formed on the surface of the translucent substrate 6 on which the translucent electrode 7 is formed by using a screen printing method or the like. Next, the other translucent substrate 4 and the surface on which the translucent electrode 5 is formed are bonded to face each other to cure the seal. Next, the transparent solid substance 14 in which the droplets 13 are dispersed is sealed in the gap between the two light-transmitting substrates 4 and 6 to form the polymer-dispersed liquid crystal layer 9.

  In addition to the offset printing method, a screen printing method or the like can be used as a method for attaching the needle-like filler 8 to the translucent substrate. Moreover, although the acicular filler was disperse | distributed and printed in the polyimide liquid, the solvent is not limited to a polyimide. According to the above manufacturing method, the major axis of the needle-like filler 8 can be oriented in a specific direction, and the gap between the two translucent substrates 4 and 6 is defined by the minor diameter of the needle-like filler 8. be able to.

<Example 3>
FIG. 5 is a block diagram showing Example 3 of the display device 1 according to the present invention. The same parts and the parts having the same functions are denoted by the same reference numerals.

  The display device 1 includes a display panel 2 including a liquid crystal display panel, a surface light source including a light source 16 and a light guide plate 15, a viewing angle control element 10 inserted between the display panel 2 and the light guide plate 15, and a viewing angle control element. Display control for controlling the operation of the viewing angle control circuit 17 for controlling the voltage applied to 10, the luminance control circuit 18 for controlling the light emission intensity of the light source 16, the display panel 2, the viewing angle control circuit 17, the brightness control circuit 18, and the like. And a circuit 19. Since the viewing angle control element 10, the display panel 2, and the surface light source are the same as those already described, description thereof is omitted here.

  FIG. 6 shows the viewing angle dependency of the intensity of transmitted light that passes through the viewing angle control element 10. The horizontal axis represents the viewing angle in the 9: 3 o'clock direction, and the vertical axis represents the transmitted light intensity, both of which are arbitrary units. The solid line graphs Ix and Iy in FIG. 6 are the same as those in FIG. That is, the graph Ix represents the transmitted light intensity when no electric field is applied to the liquid crystal layer 9, and the graph Iy represents the transmitted light intensity when the electric field is applied. Here, paying attention to the vertical direction (the center point of the horizontal axis in FIG. 6), the transmitted light intensity when an electric field is applied is higher than the transmitted light intensity when no electric field is applied. This is because the incident light is scattered in an oblique direction by the liquid crystal layer 9 when no electric field is applied, so that the transmitted light intensity in the vertical direction is lowered, and when the electric field is applied, the transmitted light intensity in the vertical direction is difficult to be scattered in the oblique direction. Is relatively high. Therefore, when the viewing angle control signal is supplied to the viewing angle control circuit 17 to control the viewing angle, the luminance control signal is simultaneously supplied to the brightness control circuit 18 to control the emission intensity of the light source 16. When the viewing angle range of the transmitted light 21 is switched by the viewing angle control element 10, for example, the light emission intensity of the light source 16 is also controlled so that the transmitted light intensity in the vertical direction takes a constant value.

  This will be specifically described. The display control circuit 19 gives a viewing angle control signal to the viewing angle control circuit 17. The viewing angle control circuit 17 applies a voltage to the viewing angle control element 10 to turn on the viewing angle control element 10. In addition, the display control circuit 19 provides a luminance control signal to the luminance control circuit 18 in synchronization with the viewing angle control signal. The brightness control circuit 18 reduces the power supplied to the light source 16 to a predetermined amount based on the brightness control signal, and reduces the light emission intensity of the light source 16. The transmitted light intensity at this time is a graph Iy 'shown in FIG. As a result, the transmitted light intensity in the vertical direction does not change even when the viewing angle control element 10 is switched on and off, thereby improving the visibility of the display, and the narrow viewing angle in the narrow viewing angle state is only the specific direction. Therefore, the display can be easily visually recognized even in this state.

  Further, the graph Ix ′ in FIG. 6 increases the power supplied to the light source 16 from the luminance control circuit 18 when the viewing angle control element 10 is turned off by the viewing angle control circuit 17 to widen the viewing angle range in the 9 o'clock direction. The viewing angle characteristics of the transmittance intensity when the emission intensity is increased. As a result, similarly to the above, the transmitted light intensity in the vertical direction does not change even when the viewing angle control element 10 is switched. In this way, by adjusting the emission intensity of the light source 16 according to the viewing angle control of the viewing angle control element 10, the visibility of characters, images, etc. displayed on the display panel 2 can be improved. In the above example, the direction in which the transmitted light intensity does not change regardless of whether the viewing angle control element 10 is on or off is the vertical direction. However, the present invention is not limited to this. For example, the viewing angle at which the transmitted light intensity is constant can be set as appropriate, for example, by setting the angle at 6 o'clock to 10 ° or 20 °.

  The display device 1 described above can be used as display means for a mobile phone, an electronic book, a personal computer, a digital camera, or the like. The displayed information is concealed from the surroundings, and a portable device with excellent visibility can be provided to the operator.

1 is a perspective view of a display device according to the present invention. It is typical sectional drawing of the display apparatus by this invention. It is typical sectional drawing of the display apparatus by this invention. It is a graph which shows the transmitted light viewing angle characteristic of the display apparatus by this invention. It is typical sectional drawing of the display apparatus by this invention. It is a graph which shows the transmitted light viewing angle characteristic of the display apparatus by this invention. It is sectional drawing of a conventionally well-known liquid crystal display device. It is sectional drawing of a conventionally well-known liquid crystal display device. It is a graph which shows the permeation | transmission light acquisition property of a conventionally well-known liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Display panel 3 Surface light source 4, 6 Translucent board | substrate 5, 7 Translucent electrode 8 Needle-like filler 9 Liquid crystal layer 10 Viewing angle control element 11 Power supply 12 Liquid crystal molecule 13 Droplet 14 Translucent solid substance 15 Conduction Light plate 16 Light source

Claims (5)

A display device in which a viewing angle control element capable of changing an angular distribution of transmitted light and a display element that performs display using the transmitted light are stacked,
The viewing angle control element includes a pair of translucent substrates having inner surfaces on which a translucent electrode is formed, a liquid crystal layer sandwiched between the pair of translucent substrates, and a gap between the pair of translucent substrates. And acicular fillers that are dispersed and sandwiched and oriented in substantially one direction within the plane of the substrate,
The display device characterized in that an angular distribution of the transmitted light changes in accordance with a change in voltage applied to the liquid crystal layer.   The display device according to claim 1, wherein the liquid crystal layer is a polymer-dispersed liquid crystal layer.   The display device according to claim 1, wherein the transmitted light has a smaller change in angular distribution in a direction orthogonal to the substantially one direction than in the approximately one direction.   The display device according to claim 1, wherein the substantially one direction is a direction of about 9 o'clock and 3 o'clock when viewed from a viewing direction of the display. A visual angle control circuit for driving the visual angle control element; and a luminance control circuit for controlling the display luminance of the display element;
5. The display brightness of the display element is controlled by the brightness control circuit in accordance with a change in voltage applied to the viewing angle control element by the viewing angle control circuit. The display device described.

Images