JP2007148278A - Display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display apparatus wherein information displayed on a display screen can be satisfactorily visually confirmed in visual confirmation from the front direction to be a main visual field angle direction of the display screen and the displayed information is hardly visually confirmed in the entire region of the display screen in the visual confirmation in the direction other than the front direction. <P>SOLUTION: In the display apparatus provided with a display panel 2 displaying desired information and a visual field angle control panel 1 disposed to be laminated on the display panel 2, a liquid crystal display element 11 wherein a liquid crystal layer is disposed between a pair of substrates 12 having electrodes 13 formed thereon is adopted as the visual field angle control panel 1, a liquid crystal 17 of the liquid crystal layer is aligned in parallel and a retardation value Δn<SB>LC</SB>×d<SB>LC</SB>thereof is specified to be 0.3 to 0.8 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a viewing angle control panel, and an area (equivalent to a good visible area or a visible area) where desired information can be satisfactorily viewed by viewing angle control on the same display screen. The present invention relates to a display device adjusted so that a difficult region (corresponding to a defective visible region or an invisible region) is formed.

  Conventionally, display devices used for mobile phones, PDAs, and the like have been required to have a wider viewing angle as the screen size becomes larger.

  However, high-security information such as e-mail is often displayed on a display device used for a mobile phone, a PDA, etc., and the high-security information is displayed on a wide viewing angle display device. Then, there is a possibility that the display can be seen by an unspecified person who is in a position where he can peek at the display screen. Therefore, the need for controlling the viewing angle within a specific range has been increasing from the demand for privacy protection.

  As one of the control techniques for limiting the viewing angle of conventional display devices to a predetermined range, the display device includes a liquid crystal layer for displaying desired information and an alignment film sandwiching the liquid crystal layer, and is compatible with all display screens. There is a configuration in which the alignment film of a region is divided into a plurality of regions, and the viewing angle of the display device is made different by setting the alignment directions of the adjacent regions to a plurality of directions.

  The display device configured as described above applies that the viewing angle of the liquid crystal display is different depending on the alignment processing direction on the alignment film, and when viewing the display screen from a specific direction, A defective visible region (or an invisible region where the information cannot be visually recognized at all) in which it is extremely difficult to visually recognize desired information is used (see Patent Document 1).

JP 2001-264768 A

  In this prior art, if the alignment film of the entire region corresponding to the display screen is divided into a plurality of regions and an alignment process such as rubbing is performed so that the alignment directions of adjacent regions are different, the defective visible region is, for example, It will be arranged in a checkered pattern.

  However, depending on the size and density of each defective visible region constituting the checkered pattern, for example, the defective visible region arranged in the checkered pattern and one object as desired information that is largely projected on the entire display screen When the images overlap, even if half of the image is partially invisible due to the checkerboard pattern, the remaining half of the image is visible without being blocked by the defective visible area, The form of the entire image is easily determined. Similarly, when a defective overlapping area and a sentence overlap in a checkered pattern, even if it is difficult to identify characters in the defective visible area, half of the remaining sentence is blocked by the checkered pattern. Since the characters are identified without being recognized, the contents of the sentence may be easily imagined and discriminated if the visually recognizable characters are connected in pieces.

  Therefore, the present invention makes it possible to satisfactorily view the information displayed on the display screen for viewing from the front direction, which is the main viewing angle direction of the display screen, and particularly for viewing from the left-right direction. An object of the present invention is to provide a display device that makes it difficult to visually recognize displayed information in the entire area of the display screen.

In order to achieve the above-described object, a display device according to a first aspect of the present invention includes a display panel on which desired information is displayed, and a viewing angle control panel disposed on the display panel. In the display device, the viewing angle control panel is a liquid crystal display element in which a liquid crystal layer is disposed between a pair of substrates on which electrodes are formed, and the liquid crystal of the liquid crystal layer is in a parallel orientation and has a retardation value Δn _LC. · _{d LC} is characterized in that it is a 0.3 to 0.8 [mu] m.

  According to the present embodiment, by applying an appropriate voltage to the viewing angle control panel, the dummy pattern is visually recognized in the left and right viewing angle directions, a good visible region is formed in the vertical direction of the display screen, and in the left and right direction. A defective visible area is formed in which a dummy pattern is overlapped with information displayed on the display panel to perform a double display, and the user of the display device visually recognizes the information with a good display quality while unidentifying private information. Can be protected from visual recognition.

  In the display device of the second aspect of the present invention, the display panel is a liquid crystal display element in which a liquid crystal layer is disposed between a pair of transparent substrates on which electrodes are formed. The display device according to the second aspect is characterized in that the viewing angle control panel and the display panel have polarizing plates on the viewing side and the non-viewing side, respectively.

  According to these embodiments, a display device can be configured easily and inexpensively, and the vibration direction of light can be regulated by adjusting the axial direction of the polarization axis.

  The display device according to the fourth aspect of the present invention is the display device according to the second aspect, wherein the viewing angle control panel is disposed above the display panel, a polarizing plate on the viewing side, and a polarizing plate on the non-viewing side. Each of the display panels has a reflective polarizing plate, and the display panel has polarizing plates on a viewing side and an anti-viewing side.

  According to the present embodiment, by providing the reflective polarizing plate, the effect of the first aspect can be obtained at the time of transmissive display, and at the time of reflective display using external light, A defective visible region can be formed by using the reflected light of the reflective polarizing plate to protect private information from being viewed by an unspecified person and to realize a special display effect (appearance).

  The display device according to the fifth aspect of the present invention is the display device according to the first to fourth aspects, wherein a polarization axis angle of light is set to a predetermined angle between the display panel and the viewing angle control panel. An optical rotatory element for guiding rotation is arranged.

  According to this embodiment, the light transmitted through the lower display panel or viewing angle control panel can be guided to the upper viewing angle control panel or display panel by the optical rotation element. In particular, in the display device according to the third aspect, the viewing angle control positioned above the display panel or the viewing angle control panel disposed at the lower position with the light absorbed by the polarizing plate being minimized. In the display device of the fourth aspect, the light transmitted through the lower display panel is suppressed to the minimum by the reflection polarizing plate in the transmissive display. In this state, it is possible to guide to the viewing angle control panel located at the upper level. Therefore, the display device can obtain bright and good visibility.

  The display device according to the sixth embodiment of the present invention is the display device according to the second to fifth aspects, wherein a light diffusion layer is provided between the liquid crystal layer of the viewing angle control panel and the liquid crystal layer of the display panel. Is provided.

  According to this embodiment, since the light diffusion layer diffuses the light transmitted between both liquid crystals, the light path is blurred to make it difficult for the line-shaped colored portion to be visually recognized, thereby obtaining good display screen visibility. Can do.

  According to the present invention, it is possible to satisfactorily visually recognize information displayed on the display screen for viewing from the front direction which is the main viewing angle direction of the display screen, and display for viewing from the side direction. In the entire area of the screen, the displayed information can be made difficult to view or cannot be viewed, and personal information can be protected from being viewed by an unspecified person.

  FIG. 1 is a schematic cross-sectional view of an embodiment of a display device according to the present invention.

  The display device of this embodiment includes a viewing angle control panel 1, a display panel 2, and a backlight unit 3, and the viewing angle control panel 1 is disposed on the viewing side of the display panel 2. A backlight unit 3 is disposed on the non-viewing side of the display panel 2.

  In the present embodiment, a liquid crystal display element 11 is used as the viewing angle control panel 1.

  The liquid crystal display element 11 is electrically connected from the outside so that desired information displayed on the display panel 2 can be viewed in the main viewing angle direction and dummy display can be viewed in directions other than the main viewing angle. A portion where the transmittance and / or the color can be changed by the signal is provided.

  That is, in this embodiment, the liquid crystal display element 11 constituting the viewing angle control panel 1 includes two transparent substrates 12 (hereinafter referred to as the viewing side) arranged substantially in parallel with a gap as shown in FIG. The transparent substrate 12 disposed on the first transparent substrate 12a and the transparent substrate 12 disposed on the non-viewing side is referred to as a second transparent substrate 12b), and the first transparent substrate 12a and the second transparent substrate 12b On the inner surface, a first electrode 13a and a second electrode 13b are formed, respectively, and a dummy display pattern (hereinafter referred to as a dummy pattern) is formed. As the dummy pattern, for example, arbitrary characters arranged continuously (texts if meaningful connection), a pattern in which the same pattern is continuously arranged, and the like can be exemplified. In the present embodiment, a description will be given below by taking as an example a case where continuous sentences of hiragana that are substantially the same as the size of characters displayed on the display panel 2 are formed as dummy patterns.

  A first alignment film 14a and a second alignment film 14b are formed on the upper surfaces of the first electrode 13a and the second electrode 13b, respectively, for controlling the alignment of liquid crystal molecules according to the voltage applied between the electrodes. ing.

The first transparent substrate 12a and the second transparent substrate 12b are disposed so that the first alignment film 14a and the second alignment film 14b face each other, and spacers 15 are dispersed between the first transparent film 12a and the second transparent film 12b. In this state, the periphery is sealed with a peripheral sealing material 16 made of epoxy resin or the like. Furthermore, the liquid crystal 17 is enclosed in the space surrounded by the first transparent substrate 12a, the second transparent substrate 12b, and the peripheral sealing material 16 to form a liquid crystal layer. In the present embodiment, the retardation value Δn _LC · d _LC of the liquid crystal layer is adjusted to be in the range of 0.3 to 0.8 μm. The reason will be described later.

  The first transparent substrate 12a and the second transparent substrate 12b can be made of a light-transmitting material, such as glass or synthetic resin, respectively. As the first electrode 13a and the second electrode 13b, A light-transmitting conductive film such as ITO can be used. The first alignment film 14a and the second alignment film 14b are made of a polymer film such as polyimide, and are subjected to a rubbing process to align liquid crystals in the vicinity of the first transparent substrate 12 and the second transparent substrate 12, It is formed as an orientation anisotropic film. In the present embodiment, the liquid crystal 17 of the liquid crystal layer is parallel aligned along the alignment direction of the first alignment film 14a and the second alignment film 14b.

  In addition, on the viewing side and the non-viewing side of the viewing angle control panel 1, a first polarizing plate 4a and a second polarizing plate, each having a polarization axis (transmission axis) arranged in a predetermined direction in order to regulate the vibration direction of light, respectively. A plate 4b is provided. The first polarizing plate 4a and the second polarizing plate 4b are polarizing plates whose polarization axes and absorption axes are orthogonal to each other.

  FIG. 3 shows the rubbing direction of the alignment film of the viewing angle control panel 1 and the polarization axis directions of the first polarizing plate 4a and the second polarizing plate 4b. As shown in this figure, the rubbing of the alignment film of the viewing angle control panel 1 is performed in the direction parallel to the viewing angle and in the opposite direction on the viewing side and the non-viewing side of the viewing angle control panel 1. The first polarizing plate 4a and the second polarizing plate 4b are both arranged such that their polarization axes are parallel to the viewing angle or orthogonal to the viewing angle. The “polarization axis” used in the text is the same as the “transmission axis”.

  When the viewing angle control panel 1 is disposed on the viewing side of the display panel 2 as in the present embodiment, the axial angle of the second polarizing plate 4b disposed on the non-viewing side of the viewing angle control panel 1 As long as the axial angles of the first polarizing plates 5a of the display panel 2 coincide with each other, one of the polarizing plates can be omitted. In this case, by omitting the arrangement of the second polarizing plate 4b, it is possible to prevent the luminance from being reduced due to the light absorption of the polarizing plate 4, and to reduce the thickness of the display device.

  Further, the viewing angle control panel 1 can be disposed between the backlight unit 3 and the display panel 2.

  Further, the display panel 2 is a known TN type, STN type, IPS type, VA type or the like in which a liquid crystal layer 27 is disposed between a pair of transparent substrates 22a and 22b on which electrodes (not shown) are formed. The liquid crystal display element 21 is used. In addition to the TN liquid crystal, a retardation plate may be disposed between the polarizing plate 5a on the viewing side and the transparent substrate 22a and between the polarizing plate 5b on the non-viewing side and the transparent substrate 22b. It is omitted in the embodiment. The structure of the liquid crystal display element 21 is different in terms of the pattern shape of the liquid crystal display element 11 and the electrode 13 used as the viewing angle control panel 1 described above, but the other structures are substantially the same and the description thereof is omitted. .

  A first polarizing plate 5a and a second polarizing plate 5b each having a polarization axis arranged in a predetermined direction are provided on the viewing side and the non-viewing side of the display panel 2 in order to regulate the vibration direction of light. ing.

  The backlight unit 3 is assumed to be a known unit having a light source (not shown) such as a fluorescent tube and a light guide plate (not shown) for reflecting the light of the light source toward the display panel 2. Omitted.

  In the display device of this embodiment configured as described above, the light emitted from the light source of the backlight unit 3 passes through the second polarizing plate 5b and the display panel 2 of the display panel 2, and The first polarizing plate 5 a and the second polarizing plate 4 b of the viewing angle control panel 1 are converted into linearly polarized light and enter the liquid crystal layer of the viewing angle control panel 1 as it is.

  When no voltage is applied to the first electrode 13 a and the second electrode 13 b of the viewing angle control panel 1, the liquid crystal molecules in the liquid crystal layer are aligned in the same direction and perpendicular to the incident linearly polarized light. . Therefore, the incident light passes through the liquid crystal layer as it is without causing a birefringence effect.

  The direction of the polarization axis of the first polarizing plate 4a of the viewing angle control panel 1 is arranged in the same direction as the linearly polarized light transmitted through the liquid crystal layer of the viewing angle control panel 1, so that the incident light is transmitted as it is. Will be.

  Further, when a voltage is applied to the first electrode 13a and the second electrode 13b of the viewing angle control panel 1, liquid crystal molecules having positive dielectric anisotropy are applied to the first transparent substrate 12a and the second transparent substrate 12b. The arrangement direction is changed vertically (the same direction as the electric field). At this time, incident light passes through the liquid crystal layer as it is without causing a birefringence effect in a direction perpendicular to the display screen, but birefringence occurs in an oblique direction, and the transmittance and color change. This difference in transmittance and color will appear as a dummy pattern.

  Furthermore, in the display panel 2 of the present embodiment, a continuous sentence of hiragana substantially equal to the size of the characters displayed on the display panel 2 is formed as a dummy pattern on the viewing angle control panel 1. When a voltage is applied to the first electrode 13 a and the second electrode 13 b of the viewing angle control panel 1, this dummy pattern is displayed on the viewing angle control panel 1.

  This dummy pattern is not visible in the entire area of the display screen because the light incident on the viewing angle control panel 1 passes through the liquid crystal layer as it is from the front direction which is the main viewing angle direction. From an oblique direction other than the front, since the light incident in the viewing angle control panel 1 is birefringent and changes in transmittance and color, it is visually recognized overlapping with information displayed on the display panel 2. Become.

  In particular, in the present embodiment, when the desired information to be displayed on the display panel 2 is character information by using the dummy pattern as a sentence in which hiragana is arranged, in particular, characters as information and dummy By displaying the pattern characters so as to overlap each other, it is possible to prevent an unspecified person from visually recognizing the characters as information.

Here, the phase difference value Δn _LC · d _{LC of the} liquid crystal layer in the viewing angle control panel 1 of the present embodiment in which the liquid crystal 17 of the liquid crystal layer is aligned in parallel, and the first electrode 13 a and the second electrode 13 b The voltage value to be applied will be described.

FIG. 4 shows a change in voltage (0 V) when the retardation value Δn _LC · d _LC of the liquid crystal layer in the viewing angle control panel 1 of the present embodiment in which the liquid crystal 17 of the liquid crystal layer is aligned in parallel is 0.5 μm. (7V) and the experimental results of the transmittance depending on the viewing angle. FIG. 5 shows the experimental results of the voltage change (0 V to 7 V) and the viewing angle dependence of the transmittance when the retardation value Δn _LC · d _LC of the liquid crystal layer is 1.0 μm. 4 and 5, the circular lines that are concentric circles and are shown at 0 ° to 80 ° at intervals of 20 ° indicate the inclination angle (θ) from the normal line of the display surface of the liquid crystal display device, A line extending radially from the center point of the figure and dividing the figure into 12 indicates a clockwise angle (φ) assuming that the 3 o'clock direction of the display screen of the display device is 0 °. . Here, the transmittance is the transmittance of the voltage application portion of the dummy pattern displayed on the viewing angle control panel 1. When this transmittance is reduced, the contrast with the non-voltage applied portion is increased, and the dummy pattern is easily visually recognized. That is, in the area where the transmittance is small, the display of the display panel 2 and the dummy pattern are displayed so as to overlap each other, so that the information can be protected from being viewed by an unspecified person. 4 and 5, the line indicated by the solid line is a line having a transmittance of 0.2. In the present embodiment, an area where a transmittance of 0.2 or more can be obtained is referred to as a “good visible region”. " Further, the line indicated by the long broken line is a line having a transmittance of 0.1, and in the present embodiment, a region where a transmittance of 0.1 or more and 0.2 or less can be obtained is referred to as a “visible region”. An area where a contrast of 0.1 or less can be obtained is defined as a “defective visible area”. Furthermore, a line indicated by a two-dot chain line is a line having a transmittance of 0.05, and in this embodiment, a region having a contrast of 0.05 or less is defined as an “invisible region”.

  The liquid crystal of the viewing angle control panel used in this experiment is RDP-86030 manufactured by Dainippon Ink & Chemicals, Inc.

The viewing angle control panel 1 in which the retardation value Δn _LC · d _LC of the liquid crystal layer is 0.5 μm has an applied voltage in the range of 3.0 to 4.0 V as shown in FIG. In the vertical direction (12 o'clock / 6 o'clock direction) with respect to the display screen, the tilt angle θ from the normal line is set to 0 to 60 ° in the vertical direction (12 o'clock / 6 o'clock direction) with respect to the display screen. In the left and right directions (9 o'clock and 3 o'clock directions), the inclination angle θ from the normal line can be formed in the range of 0 to 30 °. A defect visible region having a transmittance of 0.1 or less is set to a range in which the inclination angle θ from the normal line is 70 ° or more in the vertical direction with respect to the display screen, and the inclination angle θ from the normal line is 40 ° in the horizontal direction. In addition, it is possible to form an invisible region having a transmittance of 0.05 or less in the above range and in a range where the inclination angle θ from the normal line is 50 ° or more in the left-right direction with respect to the display screen. I understood.

  Considering a display screen of a mobile phone or the like, the user of the display device is often located in the front direction of the display screen, and the unspecified person is often located in the left-right direction. Therefore, if the viewing angle dependency as in the voltage application of 3.0 to 4.0 V shown in FIG. 4 can be obtained, the information displayed on the display screen can be improved for viewing from the front direction. For visual recognition from a direction other than the front, the information is poorly visible or cannot be visually recognized by overlapping a dummy pattern with desired information displayed on the display panel 2 in the defective visible region or invisible region. It can be. Therefore, it is possible to protect private information from being viewed by an unspecified person.

  Under the conditions of this test, when the applied voltage is lower than 3.0 V, the good visible region extends to the range where the inclination angle θ from the normal is 0 to 55 ° in the left-right direction, and the defective visible region. Is in a range in which the inclination angle θ from the normal line is 70 ° or more and hardly exists, so that it can be expected to protect the display screen of a mobile phone or the like from visual recognition by an unspecified person. There wasn't. When the applied voltage is higher than 4.0 V, the good visible region also extends to a range where the inclination angle θ from the normal is 0 to 60 °, particularly in the upper half (9 o'clock to 3 o'clock direction). As a result, the defect visible area is narrowed to a range in which the inclination angle θ from the normal line is 70 ° or more in the left-right direction with respect to the display screen. Protecting against it has not been fully expected.

Further, the viewing angle control panel 1 and 1.0μm retardation value Δn _LC · _{d LC} of the liquid crystal layer, as shown in FIG. 5, the retardation value Δn _LC · _{d LC} of the liquid crystal layer of the above 0. There was no appropriate range of applied voltage at which the same effect as the viewing angle control panel 1 of 5 μm was obtained.

That is, in the viewing angle control panel 1 in which the retardation value Δn _LC · d _LC of the liquid crystal layer is 1.0 μm, when the applied voltage is lower than 3.0 V, the good visible region is from the normal line in the vertical direction. The inclination angle θ extends from 0 to 60 °, and in the left-right direction, the inclination angle θ from the normal line extends to a range of 0 to 55 °, and the defective visible region extends from the normal line in the vertical and horizontal directions with respect to the display screen. The inclination angle [theta] has narrowed to a range of 70 [deg.] Or more. When the applied voltage is 3.0 V, the good visible region becomes narrow in the upper right / upper left direction (2 o'clock / 10 o'clock direction) to a range in which the inclination angle θ from the normal line is 0 to 30 °, and defective visible Although the region spreads in a range in which the inclination angle θ from the normal line is 40 ° or more, in the region of the lower half (3 o'clock to 9 o'clock direction), the good visible region remains the inclination angle θ from the normal line. Is a wide range of 0 to 60 °, and the defective visible region is narrow with an inclination angle θ from the normal of 70 ° or more, so that the display screen of a mobile phone or the like is protected from visual recognition by an unspecified person It wasn't something that could be done. Further, when the applied voltage is 4.0 V or more, the tilt angle θ from the normal line is 0 to 60 ° in the vertical direction when the good visible region is in the vertical direction, and the tilt angle θ from the normal line is 0 to 20 ° in the horizontal direction. It is formed in the range. A defective visible region or an invisible region is formed in a range in which the inclination angle θ from the normal to the display screen in the left-right direction is 30 to 50 °, but the inclination angle θ from the normal is 50 to 60 °. The viewing angle dependency having the characteristic that a visible region is formed is again shown in the range. An unspecified person who visually recognizes a display screen of a mobile phone or the like is often located in the left-right direction of the display screen. Therefore, in the left-right direction of the display screen, the range in which the display screen can be visually recognized is in the invisible region. It is not preferable that it be formed.

In addition, the viewing angle control panel 1 in which the retardation value Δn _LC · d _LC of the liquid crystal layer is less than 0.3 μm has a display area with a grayish transmittance as a whole, and good visibility is obtained. Absent.

From these results, by setting the retardation value Δn _LC · d _LC of the liquid crystal layer in parallel alignment to 0.3 μm to 0.8 μm, a good visible region is formed in the vertical direction of the display screen, In the direction, a defective visible area is formed in which a dummy pattern is superimposed on the information displayed on the display panel 2, and the user of the display device can view private information while viewing information with good display quality. It is possible to protect against unidentified person's visual recognition.

Note that the voltage applied to the electrode also varies depending on the characteristics of the liquid crystal 17 constituting the liquid crystal layer. However, as in the present embodiment, by setting the retardation value Δn _LC · d _LC of the liquid crystal layer to 0.3 μm to 0.8 μm, an appropriate voltage is always applied, so that the present embodiment always shows. Viewing angle control can be performed.

  Further, in the display device of the present embodiment, as shown in FIG. 6, the display panel is disposed between the lower display panel 2 and the upper viewing angle control panel 1 in the above display device. The polarization axis of the light from the axis angle of the polarization axis of the first polarizing plate 5a arranged on the viewing side 2 to the axis angle of the polarization axis of the second polarizing plate 4b arranged on the non-viewing side of the viewing angle control panel 1 An optical rotatory element 6 for rotating the corner may be provided. The alignment direction of the viewing angle control panel 1 is a large factor that causes the birefringence of the liquid crystal in a specific viewing angle direction (oblique direction) to change the transmittance and the color. For example, as shown in FIG. 7, in order to prevent information from being viewed by unspecified persons from the left and right direction, the orientation direction of the viewing angle control panel 1 is arranged so as to be orthogonal to the viewing angle control direction (left and right direction). There is a need to. However, the display panel 2 arranged in the lower layer has an axis angle of the polarization axis of the second polarizing plate 4b of the viewing angle control panel 1 and an axis angle of the polarization axis of the first polarizing plate 5a of the display panel 2 depending on optical specifications. It may not be possible to match. When such mismatching of the polarization axes of the polarizing plates occurs, the light transmitted from the backlight is reduced, which adversely affects the appearance of the display. In order to prevent such a problem, it is preferable to arrange the optical rotator 6. That is, by adopting the optical rotation element 6, the degree of freedom of the combination of the viewing angle control panel 1 and the display panel 2 is improved. In the present embodiment shown in FIG. 7, the first polarizing plate of the viewing angle control panel 1 is used. 4a, the axis angle of the polarization axis of the second polarizing plate 4b coincides with the orientation direction of the viewing angle control panel 1, but the axis angle of the polarization axis of the first polarizing plate 4a and the second polarizing plate 4b is the orientation direction. Even if they are arranged so as to be orthogonal to each other, the viewing angle in the left-right direction can be controlled. Examples of the optical rotatory element 6 include a crystal, a cell using a cholesteric liquid crystal whose optical rotatory power is variable by pitch adjustment, a retardation plate having a retardation value (retardation) of λ / 2, and the like.

  For example, as shown in FIG. 7, the axis angle of the polarization axis of the second polarizing plate 4b disposed on the non-viewing side of the viewing angle control panel 1 in the parallel orientation mode positioned at the upper position is 90 ° from 3 o'clock. When the axis angle of the polarization axis of the first polarizing plate 5a disposed on the viewing side of the display panel 2 positioned at the lower level is set to 135 ° from the 3 o'clock direction, the phase difference value is λ as the optical rotator 6 during that time. A / 2 retardation plate is disposed at an angle of 112.5 ° from the 3 o'clock direction.

  As a result, the light transmitted through the lower display panel 2 can be guided to the upper viewing angle control panel 1 with the light absorption by the polarizing plates 4 and 5 being minimized, so that the display device is good. High visibility can be obtained. By using two retardation plates having a retardation value of λ / 2, it is possible to correct coloring of the display screen caused by the wavelength difference of light. The same applies when the positional relationship (upper / lower) of the viewing angle control panel 1 and the display panel 2 is reversed.

  When the viewing angle control panel 1 is disposed on the viewing side of the display panel 2, the polarization axis and the absorption axis are orthogonal to each other as the second polarizing plate 4 b disposed on the non-viewing side of the viewing angle control panel 1. Instead of the normal polarizing plate, a reflective polarizing plate 4b ′ in which the polarization axis and the reflection axis are orthogonal can be used.

  FIG. 8 shows the rubbing direction of the alignment film of the viewing angle control panel 1 when the second polarizing plate 4b in the viewing angle control panel 1 shown in FIG. 3 is replaced with the reflective polarizing plate 4b ′. The axis angle directions of the 4 ′ polarization axis and the reflection axis are shown. As described above, when the second polarizing plate 4b in the viewing angle control panel 1 is replaced with the reflective polarizing plate 4b ′, the polarizing axis of the reflective polarizing plate 4b ′ is the same as the polarizing axis of the second polarizing plate 4b. Arrange them so that they are oriented. That is, in this embodiment, as shown in FIG. 8, the rubbing of the alignment film of the viewing angle control panel 1 is reversed on the viewing side and the anti-viewing side of the viewing angle control panel 1 in a direction parallel to the viewing angle. It is given to be in the direction. The first polarizing plate 4a and the reflective polarizing plate 4b 'are arranged so that their polarization axes are parallel to the viewing angle. By arranging in this way, the reflection axis of the reflective polarizing plate 4b 'is arranged so as to be orthogonal to the viewing angle. The first polarizing plate 4a and the reflective polarizing plate 4b 'may be arranged so that the respective polarization axes are orthogonal to the viewing angle, and the reflective axis of the reflective polarizing plate 4b' may be arranged parallel to the viewing angle.

  In the display device having such a reflective polarizing plate 4 ', the light transmitted through the lower display panel 2 is minimized by the reflective polarizing plate 4b' during transmission display by the optical rotator 6 '. Since it can be guided to the viewing angle control panel 1 positioned at the upper level in a state of being limited to the limit, bright and good visibility can be obtained. In addition, during reflective display using outside light, a defective visible region is formed by using the reflected light of the reflective polarizing plate 4 ', and private information is protected from unidentified viewers, and a special display is provided. An effect (appearance) can be realized.

  Further, the light diffusion layer 7 may be disposed between the liquid crystal layer of the viewing angle control panel 1 and the liquid crystal layer of the display panel 2 so that the surface is roughened by fine irregularities.

  Further, as shown in FIG. 9, a light diffusion layer 7 is disposed between the second transparent substrate 12b and the second polarizing plate 4b disposed on the opposite viewing side of the viewing angle control panel 1 positioned at the upper position. Alternatively, as shown in FIG. 10, the light diffusion layer 7 can be disposed immediately below the second polarizing plate 12 b of the viewing angle control panel 1 positioned at the upper level.

  According to the display device having these configurations, light transmitted between the two liquid crystals can be diffused by the light diffusion layer 7. That is, a liquid crystal display element in which a striped color filter is formed is used as the display panel 2, and as shown in FIG. 11, the dummy pattern formed in the viewing angle control panel has the same direction as the stripe of the color filter. When a straight line pattern extending in a straight line (a dummy pattern with a letter “P” in FIG. 11) is formed, the outline portion of the dummy pattern is caused by the difference in the refractive index of light inside and outside the dummy pattern. In addition, there is a concern that a line-shaped colored portion (indicated by hatching in FIG. 11) is visually recognized (hereinafter referred to as a pattern appearance). However, by disposing the light diffusion layer 7 as in the present embodiment, it is possible to diffuse the light transmitted between the two liquid crystals and to make the line-shaped colored portion less visible by spreading the light path. it can.

  For example, in the display device of the present embodiment having the configuration shown in FIG. 9, as shown in Table 1, the pattern appearance is visually recognized when the haze value is 10 or 20, and the image blur is haze value 60, 70, It occurred at 80. Therefore, by setting the haze value of the light diffusion layer to 30 to 50, it is possible to prevent image blurring in the display state of desired information and to prevent pattern appearance.

  Further, in the display device of the present embodiment having the configuration shown in FIG. 10, as shown in Table 2, the pattern appearance is visually recognized when the haze value is 10 or 20, and the image blur is when the haze value is 80. Occurred. Therefore, by setting the haze value of the light diffusion layer to 30 to 70, it is possible to prevent image blurring in the display state of desired information and to prevent pattern appearance.

  Further, in the display device having the reflective polarizing plate 4 ′ shown in FIG. 3, when the light diffusion layer 7 is disposed between the liquid crystal layer of the viewing angle control panel 1 and the reflective polarizing plate 4 ′, it is whitish. A diffuse reflection display can be obtained.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed. For example, in the aspect arrange | positioned between the viewing angle control panel 1 and the display panel 2 of the optical rotator 6, two polarizing plates 4 b and 5 a are arranged on both sides of the optical rotator 6. One may be omitted. By omitting the arrangement of the polarizing plates 4b and 5a, it is possible to prevent the transmittance from being lowered due to the light absorption of the polarizing plates 4b and 5a and to reduce the thickness of the display device.

Schematic sectional view of a display device according to an embodiment of the present invention Typical sectional drawing of the viewing angle control panel in the display apparatus of embodiment of this invention Explanatory drawing which shows the rubbing direction of the alignment film of the viewing angle control panel in the display apparatus of embodiment of this invention, and the polarizing-axis direction of a 1st polarizing plate and a 2nd polarizing plate. Experimental results of voltage change (0V to 7V) and contrast viewing angle dependence when liquid crystal layer retardation value Δn _LC · d _LC of viewing angle control panel in display device of embodiment of the present invention is 0.5 μm Explanatory drawing showing Experimental results of voltage change (0 V to 7 V) and dependence of contrast on viewing angle when phase difference value Δn _LC · d _LC of liquid crystal layer of viewing angle control panel in display device of embodiment of the present invention is 1.0 μm Explanatory drawing showing Schematic sectional view showing a case where an optical rotatory element is arranged in the display device of the embodiment of the present invention. Explanatory drawing which shows the example of arrangement | positioning of the optical rotatory element in the display apparatus of embodiment of this invention. In the display apparatus of embodiment of this invention, explanatory drawing which shows the axial angle direction of a polarizing axis at the time of replacing the 2nd polarizing plate of FIG. 3 with a reflective polarizing plate. Schematic sectional view showing a case where a light diffusion layer is provided in a display device according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing another case where a light diffusion layer is provided in a display device according to an embodiment of the present invention. Explanatory drawing showing a specific example of pattern appearance

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 View angle control panel 2 Display panel 3 Backlight unit 4 Polarizing plate (of viewing angle control panel) 4a 1st polarizing plate 4b 2nd polarizing plate 4b 'reflective polarizing plate 5 (of display panel) Polarizing plate 6 Optical rotator 7 Light Diffusion layer 11 Liquid crystal display element 12 Transparent substrate (of viewing angle control panel) 13 Electrode 14 Alignment film 15 Spacer 16 Peripheral sealing material 17 Liquid crystal 22 Transparent substrate (of viewing angle control panel) 27 Liquid crystal (of viewing angle control panel)

Claims (6)

In a display device comprising a display panel on which desired information is displayed, and a viewing angle control panel arranged in a stack on the display panel,
The viewing angle control panel is a liquid crystal display element in which a liquid crystal layer is disposed between a pair of substrates on which electrodes are formed, and the liquid crystal of the liquid crystal layer is in a parallel orientation, and a retardation value Δn _LC · d _LC is A display device having a thickness of 0.3 to 0.8 μm.   The display device according to claim 1, wherein the display panel is a liquid crystal display element in which a liquid crystal layer is disposed between a pair of transparent substrates on which electrodes are formed.   The display device according to claim 2, wherein the viewing angle control panel and the display panel have polarizing plates on the viewing side and the non-viewing side, respectively.   The viewing angle control panel is disposed above the display panel, and has a polarizing plate on the viewing side and a reflective polarizing plate on the non-viewing side, and the display panel has a polarizing plate on the viewing side and the non-viewing side, respectively. The display device according to claim 2.   5. The optical rotation element according to claim 1, wherein an optical rotation element that rotates and guides a polarization axis angle of light by a predetermined angle is disposed between the display panel and the viewing angle control panel. Display device.   The display device according to claim 2, wherein a light diffusion layer is disposed between the liquid crystal layer of the viewing angle control panel and the liquid crystal layer of the display panel.

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