JP2007101606A - Personal digital assistant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a personal digital assistant capable of effectively preventing a peep into a display screen from an oblique direction, and also preventing the display screen from becoming hard to see for a user. <P>SOLUTION: The personal digital assistant includes a display device for displaying information in a display area on the display screen, and a visual field changeover device for changing over a visual field angle of the above display area between a wide visual field mode for referring to the above display area with a wide visual field angle and a narrow visual field mode for referring thereto with a narrow visual field angle, and is configured so that the above visual field change-over device divides the above display area into two or more pattern areas in the above narrow visual field mode, and makes the visual field angle of each pattern narrower than that in the above wide visual filed mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a portable information terminal device, and more specifically, a portable information terminal such as a cellular phone that can variably control the viewing angle of a display device on which various types of information are displayed and suppress peeping on the display screen. Relates to the device.

  A small portable information terminal device can be carried in a pocket or a bag, and is used in various places. For example, it is often used in conference rooms, restaurants, station platforms, trains and buses. In such a case, the display screen of the portable information terminal device may be peeped by a nearby third party, and there is a problem that the privacy of the user cannot be ensured.

  As a countermeasure against such peeping, it is conceivable to narrow the viewing angle of the display device. For example, a narrow-field film that can be attached to a display screen of a mobile phone is conventionally known. A narrow-field film is a film that looks transparent from the front but appears opaque (for example, black) from an oblique direction, and has a certain effect in preventing peeping. However, if this kind of narrow-field film is attached, the image quality deteriorates even when viewed from the front, and the user must always see a low-quality screen display. Further, it is not possible to use the display screen obliquely as in the case of viewing the display screen with a large number of people.

In addition, techniques for variably controlling the viewing angle of a display device have been conventionally proposed (for example, Patent Document 1 and Patent Document 2). Patent Document 1 describes a configuration for controlling a viewing angle using a liquid crystal panel in a display device for a mobile phone, and Patent Document 2 describes a display device for a car navigation device. In particular, the car navigation device of Patent Document 2 describes a configuration in which a viewing angle is narrowed for a part of a region in a display area so that only the region is not visible from the driver's seat.
JP 2004-62094 A JP 2003-15535 A

  Conventional display devices make it difficult to see the screen display from an oblique direction by narrowing the viewing angle of the display screen. However, even with such a display device, the screen display cannot be completely invisible from an oblique direction, and even when viewed from outside the viewing angle, the contrast is lowered and is difficult to see. Only. Therefore, there is a problem that a third party can peep at the display screen even from an oblique direction.

  Therefore, the applicant of the present application forms a pattern region in the display area in the application filed on April 1, 2005 (Japanese Patent Application No. 2005-105980), and sets the viewing angle other than the pattern region to a narrow viewing angle in the narrow viewing mode. A configuration was proposed. With such a configuration, when the display screen is viewed from an oblique direction that is within the viewing angle with respect to the pattern area but outside the viewing angle with respect to other than the pattern area in the narrow viewing mode, if the display screen is viewed from an oblique direction other than the pattern area Due to the difference in viewing angle, the pattern area is visually recognized with high contrast close to white, and other areas than the pattern area are visually recognized with low contrast close to black. Thereby, since the pattern based on the contrast difference is visually recognized, it is possible to attract the consciousness of the person who is looking into the display screen to the high contrast pattern and make it difficult to read the low contrast screen display.

  The viewing angle control as described above can be performed by changing the light transmittance in a region other than the pattern region in accordance with the angle of the viewpoint viewing the display screen. More specifically, the area other than the pattern area has the maximum light transmittance for the viewpoint from the direction perpendicular to the display screen, and has the same transmittance as the pattern area, but the vertical direction. The transmittance gradually decreases as the tilt angle of the viewpoint with respect to increases.

  Here, even when the user views the display screen from the front, the viewpoint from the left and right eyes is not strictly perpendicular to the display screen, but is slightly tilted. For this reason, the light transmittance in a region other than the pattern region is lowered, and a contrast difference is generated between the pattern region and the region other than the pattern region based on the difference in the light transmittance with the pattern region.

  Therefore, the pattern may be visible to the user who views the display screen from the front in the narrow field mode. In particular, when the user is viewing the display screen from near, the angle of the viewpoint from the left and right eyes with respect to the direction perpendicular to the display screen becomes large, and the above-described problems are likely to occur. When the pattern is seen from the front in this way, there arises a problem that it is difficult for the user to see the display screen.

  The present invention has been made in view of the above circumstances, and can effectively prevent peeping of the display screen from an oblique direction and can prevent the display screen from being difficult for the user to see. An object is to provide an apparatus.

  A portable information terminal device according to the first aspect of the present invention includes a display device for displaying information in a display area on a display screen, a wide viewing mode for viewing the display area with a wide viewing angle, and a narrow viewing mode for viewing with a narrow viewing angle. And a visual field switching device that switches the viewing angle of the display area, the visual field switching device divides the display area into two or more pattern regions in the narrow visual field mode, It is configured to have a different viewing angle that is narrower than that in the wide viewing mode.

  With such a configuration, when the display screen is viewed from an oblique direction in the narrow viewing mode, the viewing angles of two or more pattern areas in the display area are different viewing angles that are narrower than those in the wide viewing mode. It can be. Accordingly, since a pattern based on the contrast difference can be displayed on the display screen, it is possible to attract the consciousness of the person who is looking into the display screen to the pattern and make it difficult to read the screen display. Accordingly, it is possible to effectively prevent peeping of the display screen from an oblique direction.

  Further, since the pattern is displayed in the display area in the narrow viewing mode at a different viewing angle that is narrower than that in the wide viewing mode, the contrast difference of the pattern does not become too large. Therefore, when the display screen is viewed from the front, it is possible to suppress the pattern from being seen based on the angle difference between the viewpoints from the left and right eyes, and it is possible to prevent the user from seeing the display screen.

  In the portable information terminal device according to the second aspect of the present invention, the viewing angle switching device includes the first and second electrode plates, the liquid crystal disposed between the first and second electrode plates, and the first and second electrode plates. Voltage applying means for applying an alternating voltage to the two electrode plates, and the display area is formed with a first pattern region and a second pattern region, and the voltage applying means includes a first pattern region in the first electrode plate. A first voltage applying means for applying a voltage to one pattern region and a second pattern region; and applying a voltage having a phase opposite to that of the first electrode plate to the first pattern region of the second electrode plate; And a second voltage applying means for applying a voltage that is neither in phase nor opposite in phase to the first electrode plate in the second pattern region of the second electrode plate.

  With such a configuration, when the display screen is viewed from an oblique direction, the viewing angles of the first pattern region and the second pattern region can be made different. At this time, the first pattern region in the second electrode plate is visually recognized with a low contrast close to black by applying a voltage having a phase opposite to that of the first electrode plate, and the second pattern in the second electrode plate is observed. The region is visually recognized in gray with a higher contrast than the first pattern region by applying a voltage having a phase that is neither in phase nor in antiphase with the first electrode plate.

  Accordingly, since a pattern based on the contrast difference can be displayed on the display screen, it is possible to attract the consciousness of the person who is looking into the display screen to the pattern and make it difficult to read the screen display. Accordingly, it is possible to effectively prevent peeping of the display screen from an oblique direction.

  Compared to a configuration in which a high-contrast pattern close to white is displayed by applying a voltage having the same phase as that of the first electrode plate to the second pattern region of the second electrode plate, the first pattern region And the second pattern area do not become too large. Therefore, when the display screen is viewed from the front, it is possible to suppress the pattern from being seen based on the angle difference between the viewpoints from the left and right eyes, and it is possible to prevent the user from seeing the display screen.

  The portable information terminal device according to a third aspect of the present invention is configured such that the phase of the voltage applied by the second voltage applying unit to the second pattern region of the second electrode plate is opposite to that of the first electrode plate, or Phase control means for switching to a phase that is neither in-phase nor anti-phase with the first electrode plate is provided.

  With such a configuration, when the phase of the voltage applied by the second voltage applying means to the second pattern region of the second electrode plate is opposite to that of the first electrode plate, the display screen is viewed from an oblique direction. In addition, the viewing angle of the first pattern area and the second pattern area can be matched to make the entire display area a narrow viewing angle, which is a phase that is neither in-phase nor anti-phase with the first electrode plate. For example, when viewing the display screen from an oblique direction, the viewing angle of the first pattern area and the second pattern area is made different so that a gray pattern having a higher contrast than the first pattern area is visually recognized in the second pattern area. be able to.

  In the portable information terminal device according to the fourth aspect of the present invention, the phase control means is configured to switch the phase of the voltage applied to the second pattern region of the second electrode plate based on a user setting.

  With such a configuration, the contrast of the pattern displayed on the display screen can be adjusted by switching the phase of the applied voltage according to the user's preference. In other words, the user who places importance on the visibility when the user sees from the front rather than the prevention of peeping by a third party, determines the phase difference between the applied voltages of the first pattern region and the second pattern region on the second electrode plate. By making it small, the contrast of the pattern displayed on the display screen can be lowered, and the pattern can be made more difficult to see when viewed from the front. On the other hand, a user who places importance on prevention of peeping by a third party rather than ease of viewing when viewed from the front should increase the phase difference between the applied voltages of the first pattern region and the second pattern region on the second electrode plate. Thus, the contrast of the pattern displayed on the display screen can be increased, and the pattern based on the contrast difference can be displayed more clearly when the display screen is viewed from an oblique direction.

  In the portable information terminal device according to the fifth aspect of the present invention, the phase control means determines the phase of the voltage applied by the second voltage application means to the second pattern region of the second electrode plate, and the first electrode plate. The phase can be switched to a phase shifted by a predetermined amount in the range of 45 ° to 90 ° with respect to the phase of the voltage applied to.

  With such a configuration, the phase of the voltage applied to the second pattern region in the second electrode plate can be displayed more clearly when the display screen is viewed from an oblique direction, and the pattern based on the contrast difference can be displayed more clearly. It is possible to switch to an appropriate phase so that the pattern is more difficult to see when viewed.

  According to the present invention, since a pattern based on a contrast difference can be displayed on the display screen, it is possible to attract the consciousness of a person who is looking into the display screen to the pattern and make the screen display difficult to read. Further, it is possible to effectively prevent peeping of the display screen from an oblique direction. In addition, since the contrast difference of the pattern does not become too large, when the display screen is viewed from the front, the pattern is prevented from being seen based on the angle difference between the viewpoints from the left and right eyes, making it difficult for the user to view the display screen. Can be prevented.

FIG. 1 is an external view showing an example of a portable information terminal device according to an embodiment of the present invention. A mobile phone 1 is shown as an example of the portable information terminal device. The mobile phone 1 is a so-called foldable mobile phone, in which a display housing 100 and an operation housing 200 are connected via a hinge part 300, and are folded with one surface of the display housing 100 and the operation housing 200 facing each other. be able to.

  In the display housing 100, the main display unit 101 and the receiver for receiving 103 are arranged on the inner casing surface when folded, and the sub display section 102 and the camera 104 are arranged on the outer casing surface. In addition, the operation casing 200 has a large number of operation keys 201 and a microphone for transmitting 203 arranged on the inner casing surface when folded. Such a foldable mobile phone 1 can be carried in a compactly folded state, and if the casing is unfolded, the operation key 201 can be pressed while viewing the display on the main display unit 101. . That is, main information display is performed using the main display unit 101, and main operation input is performed using the operation keys 201.

  The main display unit 101 generally has a display area having a vertically long rectangular shape, and various information including personal information is displayed in the display area. In order to prevent such a display from being viewed by a third party, the main display unit 101 can variably control the viewing angle in the left-right direction. Here, it is assumed that a wide viewing mode that is an operation state with a wide viewing angle and a narrow viewing mode that is an operation state with a narrow viewing angle can be switched. In general, the main display unit 101 of a mobile phone has a display area smaller than that of a television receiver or a stationary information terminal device, and the position of the user's eyes and the display screen for use in the hand. Since the relationship is almost constant, it is suitable for viewing angle control. Further, since the mobile phone is used with the main display unit 101 standing to some extent, the peeping can be effectively prevented by narrowing the viewing angle in the left-right direction.

  The operation key 201 includes a visual field switching button 202 for the user to instruct switching of the visual angle of the main display unit 101. When the main display unit 101 is in a wide viewing mode that can be viewed well from an oblique direction, the main display unit 101 cannot be easily viewed from an oblique direction if the user operates the view switching button 202. It becomes. Thereafter, when the user operates the visual field switching button 202 again, the main display unit 101 returns to the wide visual field mode.

  In this embodiment, an example in which the viewing angle control is performed on the main display unit 101 will be described, but it is needless to say that the same viewing angle control can be applied to the sub display unit 102. In this embodiment, an example in which the viewing angle in the left-right direction is controlled will be described. However, the viewing angle in the up-down direction can be controlled in the same manner.

  FIG. 2 is an explanatory diagram showing an example of how the main display unit 101 in the narrow field mode is seen. (A) in the figure shows an image when the main display unit 101 is viewed from the viewpoint within the viewing angle in the narrow viewing mode, and (b) is oblique from the viewpoint outside the viewing angle in the narrow viewing mode. The image when seen in is shown.

  In the case of the wide viewing mode, if the main display unit 101 is viewed from the viewpoint within the viewing angle in the wide viewing mode, it is natural that the screen display can be viewed well. Similarly, even in the narrow field mode, if the main display unit 101 is viewed from the viewpoint within the viewing angle in the narrow field mode, the screen display can be viewed well as shown in FIG. it can. In the narrow field mode, the color quality and the like are slightly reduced as compared with the wide field mode, but it can be visually recognized in a generally good manner.

  On the other hand, when the main display unit 101 in the narrow viewing mode is viewed from a viewpoint that is within the viewing angle in the wide viewing mode but out of the viewing angle in the narrow viewing mode, as shown in FIG. The original screen display can be seen only with a low contrast, and a pattern composed of a plurality of stars superimposed on the screen can be seen with a high contrast. This pattern is realized by partially changing the viewing angle in the display area of the main display unit 101.

  The main display unit 101 in the narrow field mode narrows only the other background regions while maintaining a wide viewing angle state for the star-shaped pattern region. Therefore, when viewed from an oblique direction, the pattern area remains bright and only the background area becomes dark, and a high-contrast pattern appears in the low-contrast display area based on the contrast difference (brightness difference). Looks up. Thereby, as shown in FIG. 2B, a star-shaped pattern can be displayed with a high contrast close to white with respect to a low contrast background region close to black. As will be described later, the light transmittance in the star-shaped pattern region can be adjusted, and by adjusting the transmittance, the star-shaped pattern can be displayed in gray having a higher contrast than the background region.

  When viewing a screen display in which two patterns with different contrasts are superimposed, human vision is unconsciously attracted to high-contrast patterns, making it difficult to recognize low-contrast patterns. Yes. The cellular phone 1 according to the present embodiment attracts the viewer's consciousness to the pattern in this way, so that even if the original screen display is seen with low contrast, the content is difficult to recognize or read. ing.

  If attention is focused only on the pattern area, the screen display is easier to see than when the entire display area is narrowed. However, if the shape of the pattern region is devised by shortening the width or height, or extending it in an oblique direction, the contents can be made difficult to recognize or interpret in combination with the above-described visual attraction.

  FIG. 3 is a cross-sectional view showing a configuration example of the main display unit 101, and shows a cross section taken along the line AA of FIG. The main display unit 101 includes the visual field switching panel 2 and the liquid crystal display device 5. On the display screen of the liquid crystal display device 5, the display transmission surface of the visual field switching panel 2 is arranged, and the visual field switching panel 2 switches the viewing angle of the display transmission surface, whereby the viewing angle of the main display unit 101 is increased. Can be switched.

  The liquid crystal display device 5 is a known display device including a display liquid crystal panel 3 and a backlight 4. In the liquid crystal panel 3 for display, a liquid crystal 34 is sealed between two insulating transparent substrates (for example, glass substrates) 32a and 32b. Further, polarizing plates 31a and 31b are arranged on the outer surfaces of the substrates 32a and 32b, respectively, and transparent electrodes (for example, ITO electrodes) 33a and 33b are formed on the inner surfaces, respectively. An alternating voltage is applied to the transparent electrodes 33a and 33b. For example, in the case of a general TFT liquid crystal display device, a common electrode is formed as the front-side electrode 33a, and a large number of pixel electrodes are formed as the back-side electrode 33b.

  The backlight 4 is a light source that supplies light from the back side to the transmissive liquid crystal panel 3 for display. The display liquid crystal panel 3 displays characters and images by controlling the potential of each pixel electrode and controlling whether or not the incident light from the backlight 4 is transmitted for each pixel. That is, the area on the substrate 32b where the pixel electrodes are arranged corresponds to a display area, and information made up of characters, figures, etc. is displayed by varying the light transmittance according to the position in the display area. Is done.

  On the other hand, the view switching panel 2 realizes variable control of the viewing angle by changing the transmittance according to the traveling direction of light. A region through which light from the liquid crystal display device 5 is transmitted, that is, a region on the visual field switching panel 2 corresponding to the display area of the liquid crystal display device 5 is referred to as a display transmission surface.

  In this view switching panel 2, a liquid crystal 24 is sealed between two insulating transparent substrates (for example, glass substrates) 22a and 22b, and a polarizing plate 21 is disposed on the outer surface of the front substrate 22a. Transparent electrodes (for example, ITO electrodes) 23a and 23b are respectively formed on the inner surface of 22b. That is, if the polarizing plate 31 a of the display liquid crystal panel 3 is added, the configuration is the same as that of the display liquid crystal panel 3. An AC voltage is applied to the transparent electrodes 23a and 23b.

  The polarizing plates 21 and 31a are arranged so that their transmission axes coincide with each other, and incident light from the display liquid crystal panel 3 is transmitted through the visual field switching panel 2 if the polarization plane of the liquid crystal 24 does not change. Can do. In the liquid crystal 24, the polarization plane of the transmitted light rotates according to the angle formed by the optical axis of the transmitted light with respect to the front direction. Therefore, incident light traveling obliquely in the liquid crystal 24 toward the outside of a predetermined viewing angle is The polarizing plate 21 is blocked.

  The AC voltage is applied to the electrodes 23a, 23b, 33a, and 33b of the view switching panel 2 and the display liquid crystal panel 3 because impurities other than liquid crystal molecules mixed in the liquid crystals 24 and 34, for example, + ions and − ions are on one side. This is to prevent the electrode from being biased. When a DC voltage is applied between the opposing electrodes, impurities may be biased to one of the electrodes, and so-called burn-in may occur. By applying an AC voltage, such burn-in can be prevented. Can do.

  4 and 5 are diagrams for explaining the principle of viewing angle control. 4A and 4B are schematic views showing a state in the wide field mode, in which FIG. 4A is a perspective view, and FIG. 4B is a C arrow view. FIGS. 5A and 5B are schematic views showing a state in the narrow field mode, in which FIG. 5A is a perspective view, and FIG.

  The main display unit 101 aligns the transmission axes a1 and a2 of the polarizing plates 21 and 31a with the vertical direction of the display screen, and the liquid crystal molecules 24e (molecules of the liquid crystal 24) disposed between the polarizing plates 21 and 31a. By controlling the orientation direction, the viewing angle in the left-right direction of the display screen is changed.

  In the wide viewing mode, the liquid crystal molecules 24e are aligned so as to be parallel to the transmission axes a1 and a2 (see FIG. 4). At this time, even when the visual field switching panel 2 is viewed from the front viewpoint e1, or when viewed from the viewpoint e2 having an angle α in the left-right direction with respect to the viewpoint e1, the direction of the liquid crystal molecules 24e. Appears to coincide with the transmission axes a1 and a2. Therefore, regardless of the light traveling direction, the incident light from the display liquid crystal panel 3 is not birefringent in the liquid crystal 24 and can pass through the polarizing plate 21. The viewing angle of the main display unit 101 is the widest in this case and matches the viewing angle of the display liquid crystal panel 3.

  On the other hand, in the narrow field mode, an electric field is formed between the electrodes 23a and 23b, and the liquid crystal molecules 24e are rotated from the state shown in FIG. 4 and are oriented so as to form an angle θ with respect to the transmission axes a1 and a2 ( (See FIG. 5). However, the liquid crystal molecules 24e are only tilted in the front-rear direction by the rotation, and the projected image on the display screen is still kept parallel to the transmission axes a1 and a2. That is, the liquid crystal molecules 24e are rotated in a plane perpendicular to the display screen and parallel to the transmission axes a1 and a2.

  When the field switching panel 2 in such a narrow field mode is viewed from the front viewpoint e1, the direction of the liquid crystal molecules 24e coincides with the direction of the transmission axes a1 and a2 as in the wide field mode, but the viewpoint e1. When viewed from a viewpoint e2 having an angle α in the horizontal direction, the direction of the liquid crystal molecules 24e forms an angle β with the transmission axes a1 and a2. For this reason, the light traveling toward the viewpoint e2 has its polarization plane rotated according to the angle β in the liquid crystal 24 and attenuated or blocked by the polarizing plate 21. Since the angle β changes according to the angle θ and the angle α, a viewing angle corresponding to the angle θ is obtained. Accordingly, the viewing angle of the viewing switching panel 2 can be linearly changed according to the angle θ between the liquid crystal molecules 24e and the transmission axes a1 and a2.

  When the viewing angle switching panel 2 is AC driven, the angle θ changes according to the effective value of the AC voltage applied between the electrodes 23a and 23b. In the present embodiment, alternating voltages of the same level and the same period are applied to the electrodes 23a and 23b, and as described later, only the phase of the applied voltage is changed, so that the viewing angle in the display area is partially increased. Are different.

  FIG. 6 is a diagram showing a configuration example of the electrodes 23a and 23b of the visual field switching panel 2 of FIG. Each of the electrodes 23a and 23b is divided into one or more pattern regions and a background region excluding these pattern regions, and each region is configured as an independent electrode piece. These electrode pieces are insulated from each other by providing a slight gap (for example, a minimum of 12 μm) between adjacent electrode pieces.

  The electrode 23a on the front side has three types of character patterns “(not shown for violation of public order and morals)”, “(not shown for violation of public order and morals)” and “(not shown for violation of public order and morals)” (both are trademarks or A pattern region made of (registered trademark) is formed. These pattern areas and background areas as other pattern areas are formed as independent electrode pieces, and the phase and voltage level of the applied voltage can be controlled independently. Here, the background area is the electrode terminal Ta0, “(not shown for public order and morals violation)” is the electrode terminal Ta1, “(not shown for public order and morals violation)” is the electrode terminal Ta2, “(about public order and morals violation, Not shown) "is connected to the electrode terminal Ta3.

  In addition, a large number of star-shaped pattern regions are formed on the back electrode 23b. This pattern region is an aggregate of small star-shaped pattern pieces, and each pattern piece is connected to each other arranged on an oblique straight line from the upper right to the lower left of the display area, and extends obliquely. A plurality of pattern rows are formed. These pattern rows are connected to the electrode terminal Tb1 or the electrode terminal Tb2 so that the adjacent pattern rows are connected to different electrode terminals. That is, a first pattern region in which a plurality of pattern rows are connected in a comb-like shape and connected to the electrode terminal Tb1, and a second pattern region in which a plurality of pattern rows are connected in a comb-like shape and connected to the electrode terminal Tb2 , One tooth is arranged in a combined state so as to be inserted between the other teeth. The background areas as the first pattern area, the second pattern area, and the other pattern areas are formed as independent electrode pieces, and the background area is connected to the electrode terminal Tb0.

  If the phase of the voltage applied to the electrode terminals Ta0 to Ta3 and Tb0 to Tb2 is controlled, the effective value of the AC voltage applied to the opposing electrodes 23a and 23b is changed to change the viewing angle in the display area. Can be partially different. For example, if a voltage having the same phase is applied to the opposing electrodes 23a and 23b, the region has a wide viewing angle. If the phase of the voltage applied to the opposing electrodes 23a and 23b is shifted, the viewing angle depends on the shift amount. Becomes narrower.

  FIG. 7 and FIG. 8 are diagrams showing changes in the effective value when the phase of the AC voltage applied to the opposing electrodes 23a and 23b is shifted, and the voltage applied to each of the opposing electrodes 23a and 23b is shown in FIG. The waveform and its combined wave are shown. 7A shows the case where the phase is the same, FIG. 7B shows the case where the phase is shifted by 45 °, and FIG. 7C shows the case where the phase is shifted by 67.5 °. 8A shows a case where the phase is shifted by 90 °, FIG. 8B shows a case where the phase is shifted by 135 °, and FIG. 8C shows a case where the phase is reversed. In the present embodiment, the voltage level applied to each electrode 23a, 23b is 1.80V.

An effective value RMS (Root Mean Square) based on the potential difference E between the electrodes 23a and 23b can be expressed by the square root of the time-average square of the potential difference E, that is, the following equation.
RMS = √ {(∫E ² dt) / T}

  Therefore, as shown in FIG. 7A, when the applied voltages to the opposing electrodes 23a and 23b are in phase, the potential difference E is always 0, so the effective value RMS is 0. On the other hand, as shown in FIG. 8C, when the voltage applied to the opposing electrodes 23a and 23b is in the opposite phase, the potential difference E is always the maximum value (1.80 V), so the effective value RMS is 1 .80V.

  On the other hand, when the voltage applied to the opposing electrodes 23a and 23b is shifted to a phase that is neither in-phase nor opposite-phase, according to the amount of the shift, FIGS. As shown in FIGS. 8A and 8B, the effective value RMS changes. For example, when the phase of the voltage applied to the opposing electrodes 23a and 23b is shifted by 45 ° as shown in FIG. 7B, the effective value RMS becomes 0.90 V, and as shown in FIG. When the phase of the voltage applied to the opposing electrodes 23a and 23b is shifted by 67.5 °, the effective value RMS is 1.10V. When the phase of the voltage applied to the electrodes 23a and 23b facing each other is shifted by 90 ° as shown in FIG. 8A, the effective value RMS is 1.27 V, and the electrodes face each other as shown in FIG. 8B. When the phase of the voltage applied to the electrodes 23a and 23b is shifted by 135 °, the effective value RMS is 1.56V.

  As shown in FIG. 8B, when the RMS value reaches about 1.5 V, the viewing angle becomes very narrow, and when the display screen is viewed from an oblique direction, the area is visually recognized with a low contrast close to black. The Therefore, when viewing the display screen from an oblique direction, a voltage with the same phase is applied between the opposing electrodes 23a and 23b so that a region that is visible with high contrast close to white or a voltage with an opposite phase is applied. Therefore, the effective value RMS may be in the range of 0.9V to 1.3V in order to distinguish the region viewed with low contrast close to black and make the region have a viewing angle that is visible in gray. For this purpose, the phase difference between the electrodes 23a and 23b is preferably in the range of 45 ° to 90 °. In particular, when the phase difference is set to about 67.5 ° and the effective value RMS is set to about 1.1 V, it is visually recognized in gray that can be easily distinguished from a high contrast region close to white and a low contrast region close to black. A viewing angle can be obtained, which is more preferable.

  9 and 10 are diagrams showing an example of the display transmission surface of the visual field switching panel 2 in the narrow visual field mode.

  FIG. 9A shows an example of a pattern area formed by a viewing angle difference in the display area of the narrow viewing mode using the character pattern of the electrode 23a on the front side. In this example, a voltage is applied to the electrode terminals Tb0 to Tb2 of the back-side electrode 23b at a predetermined voltage level (for example, 1.80 V), and the electrode terminals Tb0 to Tb0 to the electrode terminal Ta0 of the front-side electrode 23a. A voltage of the opposite phase is applied at the same level as Tb2, and a voltage of the same phase as the electrode terminals Tb0 to Tb2 is applied to the electrode terminals Ta1 to Ta3.

  Thus, when the display screen is viewed from an oblique direction that is within the viewing angle with respect to the pattern region but outside the viewing angle with respect to other than the pattern region, a voltage having a phase opposite to that of the electrode 23b on the back side is applied. The background region corresponding to the electrode terminal Ta0 is visually recognized with low contrast close to black, and three characters corresponding to the electrode terminals Ta1 to Ta3 to which a voltage in phase with the electrode 23b on the back side is applied, respectively. The pattern areas of the patterns “(not published for public order and morals violation)”, “(not published for public order and morals violation)” and “(not published for public order and morals violation)” are visually recognized with high contrast close to white.

  In the example shown in FIG. 9, the back-side electrode 23b is a first electrode plate, and the front-side electrode 23a is a second electrode plate. In the display area, a first pattern region corresponding to the electrode terminal Ta0 of the front electrode 23a and a second pattern region corresponding to the electrode terminals Ta1 to Ta3 are formed.

  When the phase of the voltage applied to the electrode terminals Ta1 to Ta3 of the electrode 23a on the front surface side is shifted from the case of FIG. 9A, and a voltage that is neither in phase nor in reverse phase with the electrode terminals Tb0 to Tb2 is applied, When the display screen is viewed obliquely from the same viewpoint as in the case of FIG. 9A, as shown in FIG. 9B, three character patterns corresponding to the electrode terminals Ta1 to Ta3, respectively 9), “(Not listed for public order and morals violation)” and “(Not published for public order and morals violation)” have higher contrast than the background area, but in the case of FIG. 9 (a) Is visible in a lower contrast gray.

  On the other hand, the phase of the voltage applied to the electrode terminals Ta1 to Ta3 of the front electrode 23a is opposite to that of the electrode terminals Tb0 to Tb2, and the entire front electrode 23a is opposite in phase to the rear electrode 23b. When a voltage is applied, when the display screen is viewed obliquely from the same viewpoint as in FIG. 9A, the entire display area is visually recognized with a low contrast close to black, as shown in FIG. 9C. The character pattern as in FIGS. 9A and 9B is not visually recognized.

  FIG. 10A shows an example of a pattern area formed by a viewing angle difference in the display area of the narrow viewing mode using the graphic pattern of the electrode 23b on the back side. In this example, a voltage is applied to the electrode terminals Ta0 to Ta3 of the front electrode 23a at a predetermined voltage level (for example, 1.80 V), and the electrode terminals Ta0 to Tab0 of the back electrode 23b are applied. A voltage of the opposite phase is applied at the same level as that of Ta3, and a voltage of the same phase as that of the electrode terminals Ta0 to Ta3 is applied to the electrode terminals Tb1 to Tb2.

  Thus, when the display screen is viewed from an oblique direction that is within the viewing angle with respect to the pattern region but outside the viewing angle with respect to other than the pattern region, a voltage having a phase opposite to that of the front electrode 23a is applied. The background region corresponding to the electrode terminal Tb0 is visually recognized with a low contrast close to black and has a star shape corresponding to each of the electrode terminals Tb1 to Tb2 to which a voltage having the same phase as that of the front electrode 23a is applied. The pattern area is visually recognized with high contrast close to white.

  In the example shown in FIG. 10, the front electrode 23a is a first electrode plate, and the back electrode 23b is a second electrode plate. In the display area, a first pattern region corresponding to the electrode terminal Ta0 of the back-side electrode 23b and a second pattern region corresponding to the electrode terminals Tb1 to Tb2 are formed.

  When the phase of the voltage applied to the electrode terminals Tb1 to Tb2 of the electrode 23b on the back side is shifted from the case of FIG. 10 (a) and a voltage that is neither in phase nor opposite phase to the electrode terminals Ta0 to Ta3 is applied, When the display screen is viewed obliquely from the same viewpoint as in the case of FIG. 10A, as shown in FIG. 10B, the star-shaped pattern regions corresponding to the electrode terminals Tb1 and Tb2 are the background. Although it has a higher contrast than the region, it is visually recognized in gray with a lower contrast than in the case of FIG.

  On the other hand, the phase of the voltage applied to the electrode terminals Tb1 to Tb2 of the electrode 23b on the back side is opposite to that of the electrode terminals Ta0 to Ta3, and the entire electrode 23b on the back side has the opposite phase to the electrode 23a on the front side. When a voltage is applied, when the display screen is viewed obliquely from the same viewpoint as in FIG. 10A, the entire display area is visually recognized with low contrast close to black, as shown in FIG. 10C. A star-shaped pattern as in FIGS. 10A and 10B is not visually recognized.

  As shown in FIGS. 9B and 10B, even if the pattern area is displayed in gray with respect to the background area close to black, the consciousness of the person who wants to look into the display screen Can be attracted to the pattern, so that the screen display can be made difficult to read as compared with the case where the pattern is not displayed as shown in FIGS. 9C and 10C. Accordingly, it is possible to effectively prevent peeping of the display screen from an oblique direction.

  On the other hand, as shown in FIGS. 9A and 10A, when a high-contrast pattern close to white is displayed on a low-contrast background area close to black, the display screen is viewed from the front. Even in such a case, based on the fact that the viewpoints from the left and right eyes are slightly inclined with respect to the direction perpendicular to the display screen, a high-contrast pattern can be seen from the front to the user viewing the display screen. There is a case.

  That is, even when the user is looking at the display screen from the front, the viewpoint from the left and right eyes is not strictly perpendicular to the display screen, but in the left-right direction, similar to the viewpoint e2 shown in FIGS. It is shifted by the angle α. Accordingly, as shown in FIG. 4, in the pattern region, the direction of the liquid crystal molecules 24e coincides with the transmission axes a1 and a2, and the pattern region is visually recognized with high contrast close to white, whereas in the background region, FIG. As shown, the direction of the liquid crystal molecules 24e forms an angle β with the transmission axes a1 and a2, and the contrast of the background region is slightly lower than that of the pattern region. For this reason, there is a problem that the pattern can be seen from the front to the user who sees the display screen.

  However, as shown in FIGS. 9 (b) and 10 (b), when a gray pattern is displayed on the background area close to black, it is shown in FIGS. 9 (a) and 10 (a). Thus, the contrast difference between the background area and the pattern area does not become too large compared to the case where a high-contrast pattern close to white is displayed with respect to the low-contrast background area close to black. Therefore, when the display screen is viewed from the front, it is possible to suppress the pattern from being seen based on the angle difference between the viewpoints from the left and right eyes, and it is possible to prevent the user from seeing the display screen.

  FIG. 11 is a block diagram showing an example of the internal configuration of the mobile phone 1 shown in FIG. The main control unit 400 is a processor that controls main operations of the mobile phone 1. Here, the receiver receiver 103, the camera 104, the operation keys 201, the transmitter microphone 203, the wireless unit 401, the viewing angle controller 402, and the LCD controller 403 are controlled.

  The wireless unit 401 transmits / receives radio waves to / from a base station (not shown), and transmits / receives call sounds and e-mails. The LCD controller 403 supplies drive signals to the main display unit 101 and the sub display device 102. The viewing angle controller 402 supplies a driving signal to the viewing field switching panel 2 to perform switching control of the viewing angle, and constitutes a viewing field switching device together with the viewing field switching panel 2. The viewing angle controller 402 generates a voltage signal to be applied to each electrode terminal Ta0 to Ta3, Tb0 to Tb2 of the viewing switching panel 2 based on a control signal from the main control unit 400.

  FIG. 12 is a block diagram showing a configuration example of the viewing angle controller 402 of FIG. The viewing angle controller 402 includes a phase control unit 410, a PWM generation circuit 411, a phase inversion unit 412, seven switching elements 413, and seven amplifiers 414. Each switching element 413 and each amplifier 414 are associated with electrode terminals Ta0 to Ta3 and Tb0 to Tb2, respectively.

  The PWM generation circuit 411 generates a pulse signal (for example, frequency 70 Hz) for AC driving the visual field switching panel 2. That is, the PWM generation circuit 411 is a voltage applying unit that applies a pulse signal as an AC voltage to the electrode terminals Ta0 to Ta3 and Tb0 to Tb2.

  The phase inversion unit 412 inverts the phase of the pulse signal by shifting the phase of the pulse signal output from the PWM generation circuit 411 by 180 ° or by inverting the voltage level. The pulse signal inverted by the phase inversion unit 412 is input to the switching element 413 corresponding to the electrode terminals Ta0 and Tb0. These switching elements 413 select and output either a pulse signal directly input from the PWM generation circuit 411 or a pulse signal input from the phase inversion unit 412, and the pulse signal corresponds to a voltage in the amplifier 414 corresponding to the pulse signal. After the level is amplified, it is output to the corresponding electrode terminals Ta0 and Tb0.

  The phase control unit 410 shifts the phase of the pulse signal output from the PWM generation circuit 411, thereby shifting the pulse signal to a predetermined phase (hereinafter referred to as “intermediate”). This is referred to as “phase”). The pulse signal whose phase is switched by the phase control unit 410 is input to the switching element 413 corresponding to the electrode terminals Ta1 to Ta3 and Tb1 to Tb2. These switching elements 413 select and output either a pulse signal directly input from the PWM generation circuit 411 or a pulse signal input from the phase control unit 410, and the voltage at the amplifier 414 to which the pulse signal corresponds. After the level is amplified, it is output to the corresponding electrode terminals Ta1-Ta3, Tb1-Tb2.

  In the example shown in FIG. 9, the pulse signal from the PWM generation circuit 411 is directly input to the electrode terminals Tb0 to Tb2 as the first electrode plates, and the electrode terminals as the first pattern regions in the second electrode plate. The pulse signal inverted in phase by the phase inverting unit 412 is input to Ta0, and the pulse signal whose phase is switched by the phase control unit 410 to the electrode terminals Ta1 to Ta3 as the second pattern regions in the second electrode plate. Entered. At this time, the PWM generation circuit 411 applies a voltage to the first voltage applying means for applying a voltage to the electrode terminals Tb0 to Tb2 as the first electrode plates and to the electrode terminals Ta0 to Ta3 as the second electrode plates. It functions as a second voltage applying means.

  When the phase of the pulse signal is not switched in the phase control unit 410 and a pulse signal having the same phase as the pulse signal output from the PWM generation circuit 411 is input to the electrode terminals Ta1 to Ta3, FIG. As shown, the pattern is displayed with high contrast close to white. Further, when the phase of the pulse signal is switched to the intermediate phase in the phase control unit 410, as shown in FIG. 9 (b), the pattern is displayed in gray with lower contrast than in the case of FIG. 9 (a). The On the other hand, when the phase of the pulse signal is switched to the opposite phase in the phase control unit 410, as shown in FIG. 9C, the pattern area has the same low black color as the background area, and the pattern is displayed. Not.

  In the example shown in FIG. 10, the pulse signal from the PWM generation circuit 411 is directly input to the electrode terminals Ta0 to Ta3 as the first electrode plates, and the electrode terminals as the first pattern region in the second electrode plate. A pulse signal inverted in phase by the phase inverting unit 412 is input to Tb0, and a pulse signal whose phase is switched by the phase control unit 410 is applied to the electrode terminals Tb1 to Tb2 as the second pattern regions in the second electrode plate. Entered. At this time, the PWM generation circuit 411 applies a voltage to the first voltage applying means for applying a voltage to the electrode terminals Ta0 to Ta3 as the first electrode plates and to the electrode terminals Tb0 to Tb2 as the second electrode plates. It functions as a second voltage applying means.

  When the phase of the pulse signal is not switched in the phase control unit 410 and a pulse signal having the same phase as the pulse signal output from the PWM generation circuit 411 is input to the electrode terminals Tb1 to Tb2, FIG. As shown, the pattern is displayed with high contrast close to white. Further, when the phase of the pulse signal is switched to the intermediate phase in the phase control unit 410, as shown in FIG. 10 (b), the pattern is displayed in gray with lower contrast than in the case of FIG. 10 (a). The On the other hand, when the phase of the pulse signal is switched to the opposite phase in the phase control unit 410, as shown in FIG. 10C, the pattern area has the same low contrast as the background area, which is black, and the pattern is displayed. Not.

  In the present embodiment, the PWM generation circuit 411 generates a pulse signal only when the narrow field mode is selected. That is, when the user operates the visual field switching button 202 in the wide visual field mode, a signal instructing generation of a pulse signal is input from the visual field switching unit 421 to the PWM generation circuit 411, and the electrode terminals Ta0 to Ta3, Tb0 to Tb0. When a voltage is applied to Tb2 with a predetermined phase and voltage level, the mode is switched to the narrow field mode.

  On the other hand, when the user operates the visual field switching button 202 in the narrow visual field mode, a signal for stopping the generation of the pulse signal is input from the visual field switching unit 421 to the PWM generation circuit 411, and the electrode terminals Ta0 to Ta3, respectively. No voltage is applied to Tb0 to Tb2. Thereby, there is no potential difference between the electrode terminals Ta0 to Ta3 and Tb0 to Tb2 in the display area, and the entire display area is switched to the wide viewing mode.

  The phase of the voltage output from the phase control unit 410 is switched based on an input signal from the pattern display setting unit 422 or the transmittance setting unit 423 to the phase control unit 410. That is, when the user operates the operation key 201 so that the pattern is not displayed in the narrow field mode, a signal to that effect is input from the pattern display setting unit 422 to the phase control unit 410 and the phase control is performed. The unit 410 is set to output a voltage having an opposite phase. In this case, in the narrow-field mode, no pattern is displayed in the display area as shown in FIG. 9C or FIG.

  On the other hand, when the user operates the operation key 201 to set to display a pattern in the narrow field mode, a signal indicating that is input from the pattern display setting unit 422 to the phase control unit 410 and the phase control is performed. The unit 410 is set to output a voltage having the same phase or intermediate phase. In this case, in the narrow field mode, a pattern is displayed in the display area.

  When the pattern is preset to be displayed in the narrow field mode, the pattern is displayed with high contrast close to white as shown in FIG. 9A or 10A, or FIG. As shown in b) or FIG. 10B, whether to display in gray can be set by the user operating the operation key 201. That is, when the user operates the operation key 201 to set a high light transmittance in the pattern area, a signal to that effect is input from the transmittance setting unit 423 to the phase control unit 410. 410 is set to output a voltage having the same phase. In this case, in the narrow field mode, as shown in FIG. 9A or FIG. 10A, the pattern is displayed in the display area with high contrast close to white.

  On the other hand, when the user operates the operation key 201 to set the light transmittance in the pattern region to be low, a signal to that effect is input from the transmittance setting unit 423 to the phase control unit 410. 410 is set so that an intermediate phase voltage is output. In this case, in the narrow field mode, as shown in FIG. 9B or FIG. 10B, the pattern is displayed in gray in the display area.

  Thus, in the present embodiment, the contrast of the pattern displayed on the display screen can be adjusted by switching the phase of the voltage output from the phase control unit 410 according to the user's preference. That is, the user who places importance on the visibility when the user sees from the front rather than the prevention of peeping by a third party sets the phase of the voltage output from the phase control unit 410 as an intermediate phase, thereby FIG. As shown in b) or FIG. 10B, the contrast of the pattern displayed on the display screen can be lowered to make the pattern less visible when viewed from the front. On the other hand, a user who places importance on prevention of peeping by a third party rather than ease of viewing when viewed from the front makes the phase of the voltage output from the phase control unit 410 the same phase, so that FIG. As shown in FIG. 10 (a), the contrast of the pattern displayed on the display screen can be increased, and the pattern based on the contrast difference can be displayed more clearly when the display screen is viewed from an oblique direction.

  As described above, the intermediate phase voltage output from the phase control unit 410 may be a phase shifted by a predetermined amount in the range of 45 ° to 90 ° with respect to the phase of the voltage output from the PWM generation circuit 411. A range of 60 ° to 70 ° is more preferable. If the intermediate phase is set in such a range, the pattern based on the contrast difference can be displayed more clearly when the display screen is viewed from an oblique direction, and the pattern is more difficult to see when viewed from the front. Can be in phase.

  The phase control unit 410 and the phase inversion unit 412 can be configured by a digital circuit including a CPU (Central Processing Unit). Therefore, the contrast of the pattern displayed on the display screen can be adjusted with a simple circuit configuration by shifting the phase rather than shifting the voltage level of the applied voltage.

  However, by controlling the phase of the voltage applied to the electrodes 23a and 23b, the voltage applied to the visual field switching panel 2 is not limited by controlling the voltage level or the like, not limited to the configuration in which a gray pattern is displayed in the display area. The effective value may be controlled to display a gray pattern in the display area.

  The voltage applied to the electrodes 23a and 23b may be switchable to two or more intermediate phases that are neither in-phase nor anti-phase. Further, the configuration is not limited to the configuration in which the pattern region and the background region are formed in both the electrodes 23a and 23b, and the configuration in which the pattern region and the background region are formed in only one of the electrodes may be employed.

  The contrast of the pattern region is not limited to a configuration that can be adjusted by a user operation as in the above embodiment, and may be displayed with a predetermined gray contrast. Further, the wide-field mode and the narrow-field mode are not limited to the configuration that is switched by the operation of the field-of-view switching button 202, and the mode preset by the user may be executed.

1 is an external view showing an example of a portable information terminal device according to an embodiment of the present invention, and a mobile phone is shown as an example of a portable information terminal device. It is explanatory drawing which showed an example of how the main display part of a narrow visual field mode looks. It is sectional drawing which showed one structural example of the main display part, and the AA cross section of FIG. 1 is shown. It is a figure for demonstrating the principle of viewing angle control, and is the schematic diagram which showed the mode in wide viewing mode. It is a figure for demonstrating the principle of viewing angle control, and is the schematic diagram which showed the mode in the narrow field mode. It is the figure which showed one structural example of the electrode of the visual field switching panel of FIG. It is the figure which showed the aspect of the change of an effective value at the time of shifting the phase of the alternating voltage applied to the electrode which opposes, (a) is the same phase, (b) is when the phase is shifted 45 degrees, c) shows a case where the phase is shifted by 67.5 °. It is the figure which showed the aspect of the change of an effective value at the time of shifting the phase of the alternating voltage applied to the electrode which opposes, (a) when the phase shifted 90 degrees, (b) shifted the phase 135 degrees In the case, (c) shows the case of antiphase. It is the figure which showed an example of the display transmission surface of the visual field switching panel in a narrow visual field mode. It is the figure which showed an example of the display transmission surface of the visual field switching panel in a narrow visual field mode. FIG. 2 is a block diagram showing an example of an internal configuration of the mobile phone shown in FIG. 1. FIG. 12 is a block diagram illustrating a configuration example of a viewing angle controller in FIG. 11.

Explanation of symbols

1 Personal digital assistant (mobile phone)
2 View switching panel 3 Display liquid crystal panel 4 Backlight 5 Liquid crystal display devices 21, 31a, 31b Polarizing plates 22a, 22b, 32a, 32b Insulating transparent substrates 23a, 23b, 33a, 33b Transparent electrodes 24, 34 Liquid crystal 101 Main display Unit 102 Sub display unit 201 Operation key 202 View switching button 400 Main control unit 402 View angle controller 403 LCD controller 410 Phase control unit 411 PWM generation circuit 412 Phase inversion unit 413 Switching element 414 Amplifier 421 View switching unit 422 Pattern display setting unit 423 Transmittance setting part a1, a2 Transmission axis e1, e2 Viewpoint Ta0-Ta4 Front side electrode terminals Tb0-Tb2 Back side electrode terminals

Claims (5)

A display device for displaying information in a display area on the display screen;
A visual field switching device that switches the viewing angle of the display area between a wide viewing mode for browsing the display area with a wide viewing angle and a narrow viewing mode for viewing with a narrow viewing angle;
The field-of-view switching device divides the display area into two or more pattern areas in the narrow-field mode, and sets the viewing angle of each pattern area to a different viewing angle that is narrower than that in the wide-field mode. A portable information terminal device. The viewing angle switching device includes a first and second electrode plate, a liquid crystal disposed between the first and second electrode plates, and a voltage application that applies an alternating voltage to the first and second electrode plates. Means and
In the display area, a first pattern region and a second pattern region are formed,
The voltage applying means includes first voltage applying means for applying a voltage to the first pattern area and the second pattern area of the first electrode plate, and the first pattern area of the second electrode plate to the first pattern area. A second voltage applying means for applying a voltage having a phase opposite to that of the electrode plate and applying a voltage having neither the same phase nor the opposite phase as that of the first electrode plate to the second pattern region of the second electrode plate; The portable information terminal device according to claim 1, further comprising:   The phase of the voltage applied by the second voltage application means to the second pattern region of the second electrode plate is opposite to that of the first electrode plate, or is the same phase and opposite phase as that of the first electrode plate. The portable information terminal device according to claim 2, further comprising phase control means for switching to a phase that is not any of the above.   4. The portable information terminal device according to claim 3, wherein the phase control unit switches a phase of a voltage applied to a second pattern region in the second electrode plate based on a user setting.   The phase control means may be configured such that the phase of the voltage applied by the second voltage applying means to the second pattern region of the second electrode plate is 45 ° to the phase of the voltage applied to the first electrode plate. The portable information terminal device according to claim 3 or 4, wherein the portable information terminal device can be switched to a phase shifted by a predetermined amount within a range of 90 °.