Display unit

Abstract

To provide a display unit that can guarantee the confidentiality of a specific image without losing usability.SOLUTION: A display unit 10 comprises: a display 30; a polarization module 11 that is arranged and superimposed on the display, and that can actively switch a polarization state between a first polarization state and a second polarization state; and a controller 20. The controller is configured to generate second image data from first image data, display, on the display, a first image based on the first image data and a second image based on the second image data in a time-division manner, and in synchronization with the timing of the time division, switch the polarization state of the polarization module to be the first polarization state when the first image is displayed and the second polarization state when the second image is displayed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a display device. [Background technology]

[0002] There are cases where secret or private information should only be displayed under certain conditions. For example, Japanese Patent Application Laid-Open No. 2001-255844 (hereinafter referred to as Patent Document 1) discloses a system in which a user viewing a display using a pair of active glasses having shuttered lenses can view private data, and an unauthorized observer without active glasses can view only the private data obscured by masking data. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-255844 A Summary of the Invention

[0004] However, such a system requires glasses having lenses with shutters. Therefore, the glasses used by the user may become bulky and expensive. In addition, control is required to synchronize the glasses with the display in order to open and close the lens shutters. Therefore, wireless or wired communication is required for the user's wearable device, which may impair usability for the user. Therefore, a display device that can ensure the confidentiality of a specific image without impairing usability is desired.

[0005] According to one embodiment, a display device includes a display, a polarization module overlaid on the display, the polarization module being capable of actively switching the polarization state between a first polarization state and a second polarization state, and a controller, the controller being configured to generate second image data from first image data, cause the display to display a first image based on the first image data and a second image based on the second image data in a time-division manner, and switch the polarization state of the polarization module in synchronization with the timing of the time division so that the polarization state is the first polarization state when the first image is displayed and the second polarization state is displayed when the second image is displayed.

[0006] Further details will be described in the following embodiments. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a display system according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a display device included in the display system. [Diagram 3] FIG. 3 is a schematic plan view of the display device as viewed from the observation surface side. [Figure 4] FIG. 4 is a schematic plan view showing an example of an arrangement (layout) of a first spacer and a second spacer of a polarization module included in a display device. [Diagram 5] FIG. 5 is a diagram showing an example of the first image and the second image. [Figure 6] FIG. 6 is a diagram showing an example of a look-up table (LUT). [Figure 7] FIG. 7 is a diagram for explaining the luminance visually recognized by an observer when not wearing polarized glasses. [Figure 8] FIG. 8 is a diagram for explaining the luminance visually recognized by an observer when not wearing polarized glasses. [Figure 9] FIG. 9 is a flowchart showing an example of a method for controlling a display device in a display system. [Figure 10] FIG. 10 is a schematic diagram showing an example of the display of a display panel, the polarization state of a polarization module, and an image perceived by a viewer. [Figure 11] FIG. 11 is a schematic diagram showing an example of the display of a display panel, the polarization state of a polarization module, and an image perceived by a viewer. [Figure 12] FIG. 12 is a schematic diagram illustrating a partial configuration of a display system according to the second embodiment. [Figure 13] FIG. 13 is a schematic diagram for explaining the relationship between the display of the display panel and the polarization state of the polarization module in the display system according to the second embodiment. [Figure 14] FIG. 14 is a diagram for explaining the luminance visually recognized when the observer wears polarized glasses in the relationship of FIG. [Figure 15] FIG. 15 is a diagram for explaining the luminance visually recognized when the observer wears polarized glasses in the relationship of FIG. [Figure 16] FIG. 16 is a diagram for explaining an example of a method for generating second image data from first image data in a display system according to the third embodiment. [Figure 17] FIG. 17 is a schematic diagram showing an example of the display of the display panel, the polarization state of the polarization module, and an image perceived by a viewer in the display system according to the third embodiment. [Figure 18] FIG. 18 is a diagram showing another example of the LUT. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <1. Overview of the display device> (1) A display device according to an embodiment includes a display, a polarization module that is arranged on top of the display and is switchable between a plurality of polarization states, the polarization module being capable of actively switching the polarization state between a first polarization state and a second polarization state, and a controller. The controller is configured to generate second image data from first image data, cause a first image based on the first image data and a second image based on the second image data to be displayed on the display in a time-division manner, and switch the polarization state of the polarization module in synchronization with the timing of the time division so that the first polarization state is displayed when the first image is displayed and the second polarization state is displayed when the second image is displayed.

[0009] The observer uses polarized glasses that transmit an image displayed on a display and that is output from the polarization module in a first polarization state, but do not transmit an image output in a second polarization state. When the observer wears the polarized glasses, the observer sees only the first image of the first and second images that are switched and displayed on the display in a time-division manner. When the observer does not wear the polarized glasses, the observer sees both the first and second images that are switched and displayed on the display in a time-division manner. When the display of the first and second images is switched at a speed such that only the first image is not perceived when the observer does not wear the polarized glasses and flicker is not perceived, a composite image of the first and second images is perceived when the observer does not wear the polarized glasses. This makes it possible to make the first image perceived only when the polarized glasses are worn, or only by a user who wears the polarized glasses. At that time, it is not necessary to change the polarization state of the polarized glasses in synchronization with the display on the display. Therefore, it is not necessary to control the polarized glasses by wireless communication or the like. In addition, the polarized glasses do not require a control mechanism or a power supply, so the display device according to the present embodiment can ensure the confidentiality of a specific image (first image) without impairing usability.

[0010] (2) In the display device according to (1), preferably, the first polarization state allows the observer to view the first image through polarized glasses worn by the observer, and the second polarization state allows the observer not to view the second image through the polarized glasses. This makes it possible to easily ensure the confidentiality of the first image by using the polarized glasses as described above.

[0011] (3) In the display device according to (1) or (2), preferably, generating the second image data includes converting the image data into a gradation having a predefined relationship with respect to the gradation of the image data, so that the composite image of the first image and the second image becomes an image having a gradation according to the predefined relationship.

[0012] (4) In the display device according to (1) to (3), preferably, generating the second image data includes converting the gradation of pixels belonging to at least a part of the image data into different gradations having a predefined relationship for each gradation, and setting the gradation of pixels belonging to areas other than the part of the image data to the predefined gradation regardless of the gradation. This limits the area in the second image where the pattern of the first image may appear to the part of the image, and does not appear in other areas. Therefore, the pattern of the first image is difficult to perceive even if there is blinking or a sudden movement of the line of sight. This can further increase the secrecy of the first image.

[0013] (5) In the display device according to (1) to (4), preferably, generating the second image data includes dividing the image data into a plurality of areas and changing the gradation of each area to a gradation having a predetermined relationship according to the gradation of pixels belonging to each area. This may result in a composite image of the first image and the second image having different gradations for each area.

[0014] (6) In the display device according to (1) to (5), preferably, switching the polarization state of the polarization module includes dividing the polarization module into a plurality of segments along the scanning direction of the display, and switching the polarization states of the plurality of segments with a time difference in order along the scanning direction. This makes it possible to suppress the area of ​​the display in which rewriting to the first image has not been completed, which is included in the range of the polarization module in the first polarization state, compared to the case where the polarization state of the polarization module is switched uniformly as a whole. Therefore, the difference (unevenness) in the brightness of the first image viewed by the viewer when wearing the polarized glasses is suppressed compared to the case where the polarization state of the polarization module is switched uniformly as a whole.

[0015] <2. Examples of display devices>

[0016] [First embodiment] 1 is a schematic configuration diagram of a display system 100 according to a first embodiment. The display system 100 includes a display device 10 and a controller 20 that controls display on the display device 10. The display device 10 is mounted on, for example, a smartphone, a tablet terminal, a smartwatch, an in-vehicle information display, a personal computer, a monitor for a personal computer, a television, and the like.

[0017] FIG. 2 is a schematic cross-sectional view of a display device 10. The display device 10 includes a display 30 and a polarizing module 11 arranged to overlap the display 30. In FIG. 2, the polarizing module 11 is shown spaced apart from the display 30, but the polarizing module 11 and the display 30 may be overlapped with no space or with a very small space. The display 30 includes a display panel 12 and a backlight 13 arranged to overlap the rear surface (lower surface) of the display panel 12. In FIG. 2, the backlight 13 is shown spaced apart from the display panel 12, but the backlight 13 and the display panel 12 may be overlapped with no space or with a very small space. The polarizing module 11 is arranged on the front surface (upper surface) of the display panel 12. The display device 10 is observed by an observer A from the front side of the display panel 12. Therefore, the front surface of the display panel 12 is also an observation surface.

[0018] 3 is a schematic plan view of the display device 10 as viewed from the observation surface side. As an example, the display device 10 has a display area 1100 and a frame area 1200 arranged in a frame shape around the outer edge of the display area 1100. The display area 1100 is an area in which an arbitrary image or the like is displayed. In other words, it is an area that is visible from the observation surface side of the display device 1000 when the backlight 13 is turned on. The frame area 1200 does not transmit light. The display device 10 does not need to have the frame area 1200.

[0019] The display panel 12 has a plurality of pixels. Preferably, the display panel 12 has a plurality of pixels arranged in a matrix. The configuration of the display panel 12 is not particularly limited. The display panel 12 may have a structure in which a liquid crystal layer is sandwiched between a pair of substrates. In detail, the display panel 12 may have a liquid crystal layer sandwiched between a pair of substrates, one of which has a pixel electrode and a common electrode formed thereon, and a voltage is applied between the pixel electrode and the common electrode to apply a horizontal electric field (including a fringe electric field) to the liquid crystal layer, thereby performing display. As another example, the display panel 12 may have a liquid crystal layer sandwiched between a pair of substrates, one of which has a pixel electrode and a common electrode formed thereon, and a voltage is applied between the pixel electrode and the common electrode to apply a vertical electric field to the liquid crystal layer, thereby performing display. Examples of the horizontal electric field type include an FFS mode and an IPS mode, and examples of the vertical electric field type include a VA (Vertical Alignment) mode and a TN (Twisted Nematic) mode.

[0020] The liquid crystal mode of the display panel 12 is not particularly limited. For example, the liquid crystal mode of the display panel 12 may be one in which the liquid crystal molecules in the liquid crystal layer 260 are oriented perpendicular to the substrate surface to display black, or one in which the liquid crystal molecules in the liquid crystal layer 260 are oriented parallel to the substrate surface or in a direction neither perpendicular nor parallel to the substrate surface to display black. The driving method of the display panel 12 may be a TFT method (active matrix method), a simple matrix method (passive matrix method), a plasma address method, or the like.

[0021] As an example, the display panel 12 has a structure in which a liquid crystal layer 260 is sandwiched between a pair of substrates 211, 212, which are sandwiched between insulating films 231, 232. One of the substrates (substrate 211) is provided with pixel electrodes and a common electrode (not shown). The substrate 211 is provided with a black matrix layer (BM layer) 250, and a color filter layer 240 (a blue color filter layer 240B, a red color filter layer 240R, and a green color filter layer 240G) that are regularly arranged between the BM layer. The display panel 12 is preferably provided with the BM layer 250, and the BM layer 250 is preferably arranged in a lattice pattern in a plan view.

[0022] The display panel 12 is connected to a display panel drive unit 16, and display is realized by the display panel drive unit 16. Under the control of the display panel drive unit 16, the display panel 12 sequentially displays a main image (first image) and a sub-image (second image) described below by switching in a time-division manner.

[0023] The backlight 13 has one or more light sources (not shown). One example of the light source is an LED (Light Emitting Diode).

[0024] The backlight 13 is connected to a backlight (BL) driver 17 and is controlled to be turned on and off by the BL driver 17. A plurality of light sources (not shown) may be controlled to be turned on and off individually, or may be controlled to be turned on and off uniformly. When the display panel driver 16 sequentially displays a first image and a second image (described below) on the display panel 12 by switching them in a time-division manner, the BL driver 17 turns on all the backlights in the display area 1100.

[0025] As an example, the polarization module 11 is a panel configured with an active retarder. The polarization module 11 is switched between a plurality of polarization states by an AR (Active Retarder) panel driving unit 15. The polarization module 11 switches between a first polarization state and a second polarization state in synchronization with switching between a main image (first image) and a sub-image (second image) on the display panel 12 under the control of the AR panel driving unit 15. As an example, when the first image is displayed on the display panel 12, the polarization module 11 is in the first polarization state, and when the second image is displayed on the display panel 12, the polarization module 11 is in the second polarization state.

[0026] Observer A observes the display in display area 1100 using detachable polarized glasses 200. Note that polarized glasses 200 do not have a shutter function. When observer A is wearing polarized glasses 200, the display on display panel 12 is given a polarized state by polarization module 11 and reaches observer A's eyes via polarized glasses 200. When observer A is not wearing polarized glasses 200, the display on display panel 12 is given a polarized state by polarization module 11 and reaches observer A's eyes without passing through polarized glasses 200. The display on display panel 12 entering observer A's field of vision is referred to as "visual recognition," and ascertaining the meaning of the display that has entered the field of vision is referred to as "perception."

[0027] The polarized glasses 200 have polarizing films attached to both eye portions. The polarizing films are preferably circular polarizing films. The polarizing films are not limited to circular polarizing films, and other types of polarizing films may be used.

[0028] The polarized glasses 200 transmit an image displayed on the display panel 12 for a first polarization state in the polarization module 11, and do not transmit an image displayed on the display panel 12 for a second polarization state. In other words, the first polarization state in the polarization module 11 is a polarization state that transmits the first image displayed on the display panel 12 through the polarized glasses 200, and the second polarization state is a polarization state that does not transmit the second image displayed on the display panel 12 through the polarized glasses 200.

[0029] As a result, when observer A is not wearing the polarized glasses 200, he / she views both the first image and the second image displayed on the display panel 12 by switching in a time-division manner. When observer A is wearing the polarized glasses 200, he / she views only the first image of the first image and the second image displayed on the display panel 12 by switching in a time-division manner. In the display system 100, there is no need to change the polarization state of the polarized glasses 200 in synchronization with the display on the display panel 12. Therefore, there is no need to control the polarized glasses 200 by wireless communication or the like. Furthermore, the polarized glasses 200 do not require a control mechanism, and no power supply is required.

[0030] The polarization module 11 includes an optical laminate 110 and a retarder 120. The optical laminate 110 includes a pair of substrates 111 and 112, a pair of electrodes 121 and 122, a liquid crystal layer 160, and columnar spacers 151 and 152. More specifically, from the observation surface side, the polarization module 110 includes a first substrate 111, a first electrode 121, a liquid crystal layer 160, a second electrode 122, and a second substrate 112. Between the first substrate 111 and the first electrode 121, a light-shielding layer 170 for limitatively shielding the columnar spacers 151 and 152 is provided, and between the light-shielding layer 170 and the first electrode 121, a planarization film 180 is provided. In addition, between the electrodes 121 and 122 and the liquid crystal layer 160, insulating films 131 and 132 and alignment films 141 and 142 are respectively arranged in order from the electrode side.

[0031] The second spacers 152 are disposed to control the thickness of the liquid crystal layer 160. The first spacers 151 are disposed in a floating island shape, which makes it possible to impart surface pressure resistance to the polarization module 11.

[0032] The first spacer 151 being arranged like a floating island means that the first spacer 151 is arranged like a floating island in the liquid crystal layer 160. Specifically, this means that the liquid crystal layer 160 exists between the first spacer 151 and the first substrate 111 or the second substrate 112 in a cross-sectional view. That is, the height of the first spacer 151 is smaller than the thickness of the liquid crystal layer 160. On the other hand, the height of the second spacer 152 is equal to the thickness of the liquid crystal layer 160.

[0033] The height of the first spacers 151 is smaller than the thickness of the liquid crystal layer 160. In other words, when the thickness of the liquid crystal layer 160 is taken as 100%, the height of the first spacers 151 may be a value less than 100%, for example, 5 to 95%.

[0034] The first spacer 151 and the second spacer 152 are formed, for example, from a resin material having light-transmitting properties. The first spacer 151 and the second spacer 152 can be formed by forming a plurality of types of columnar spacers with different heights on one of the substrates (for example, the first substrate 111). Specifically, for example, after forming columnar spacers with different heights on the first substrate 111 side, the second substrate 112 is bonded with a liquid crystal material sandwiched therebetween, so that the columnar spacers with a height lower than the thickness of the liquid crystal layer 160 formed from the liquid crystal material become the first spacers 151, and the other columnar spacers become the second spacers 152.

[0035] The optical laminate 110 has a light shielding portion (also called a light shielding layer) 170 as an example of a light shielding means for restrictively shielding the first spacer 151 and the second spacer 152. The light shielding portion 170 is disposed at a position overlapping the columnar spacer. By providing such a light shielding means, it is possible to sufficiently suppress deterioration of display performance caused by phase difference shift around the columnar spacer.

[0036] The light shielding portion 170 being disposed at a position overlapping with the columnar spacer means that 80% to 100% of the area of ​​the columnar spacer overlaps with the light shielding layer in plan view, preferably 85% to 100%, more preferably 90% to 100% of the area of ​​the columnar spacer overlaps with the light shielding layer.

[0037] The light shielding portion 170 is formed from a light shielding material. Examples of the light shielding material include a metal black matrix (also referred to as a metal BM) made of a metal, and a resin black matrix (also referred to as a resin BM) made of a resin material. Examples of the metal BM include a metal film containing aluminum, molybdenum, chromium, titanium, or an alloy thereof. Examples of the resin BM include a black resist, and among them, a black photosensitive resin is preferable. A specific example is a black photosensitive acrylic resin. The light shielding portion 170 may be a single-layer film or a multi-layer film.

[0038] The light transmittance of the light shielding portion 170 is preferably, for example, 0 to 1%. The thickness of the light shielding portion 170 is not particularly limited. The thickness of the light shielding portion 170 is preferably, for example, 10 nm or more and 2 μm or less. The thickness of the light shielding portion 170 is more preferably 50 nm or more and 1.5 μm or less.

[0039] FIG. 4 is a schematic plan view showing an example of the arrangement (layout) of the first spacer 151 and the second spacer 152. The unit of the numbers in the figure is μm. The left-right direction in the figure is parallel to the long side direction of the active area of ​​the polarization module 11, that is, the area corresponding to the display area 1100 of the display device 10. The length of the long side of the display area 1100 is 59.6736 cm, and the length of the pitch B parallel to the long side A of the display area 1100 among the pixel pitches of the display panel 12 is 77.7 μm. The polarization module 11 is configured by repeatedly arranging the basic unit U in the entire area of ​​the liquid crystal layer 160, with a unit consisting of 932.4 μm × 932.4 μm square when the liquid crystal layer 160 is viewed in a plane. In FIG. 4, one basic unit U is shown surrounded by a dotted line. In the basic unit U, two second spacers 152 having a diameter φ of approximately 15.3 μm and a height of 1.6 μm are arranged, and 44 first spacers 151 having a minor axis of approximately 15 μm, a major axis of 40 μm, a height of 1.3 μm, and a quadrant shape are arranged.

[0040] To obtain the unit U, first, a large number of first spacers 151 are regularly arranged with a distance (gap) between a first spacer 151 and another first spacer 151 adjacent to it in the left-right direction of 37.7 μm, and a distance (gap) between a first spacer 151 and another first spacer 151 adjacent to it in the up-down direction of 217.6 μm. Then, the third, fourth, and fifth first spacers 151 (total of three) from the left in the second row from the bottom are removed, and one second spacer 152 is arranged at the center of the removed area (second spacer 152A). The distance (gap) between the first spacers 151a and 151b on both the left and right sides of the removed first spacer 151 (three pieces) and the second spacer 152A arranged this time is 127.75 μm. The X-view on the right side of FIG. 4 shows that the second spacer 152A arranged here and the adjacent first spacers 151a and 151b are arranged so that their central positions in the up-down direction are aligned.

[0041] Furthermore, the first spacer 151 (one piece) in the fourth row from the bottom and the third from the right is also removed, and one second spacer 152 is placed in the center of the removed area (second spacer 152B). The distance (gap) between the first spacers 151c and 151d on both the left and right sides of the removed first spacer 151 (one piece) and the second spacer 152B placed this time is 50.5 μm.

[0042] Between the light-shielding layer 170 and the first electrode 121, a planarization film (also referred to as a planarization layer) 180 for planarization is provided. The planarization film 180 is preferably, for example, an organic insulating film. As the organic insulating film, for example, an organic film having a small relative dielectric constant (relative dielectric constant ε=2 to 5) such as a photosensitive resin, or a laminated film thereof can be used. Specific examples include organic films such as acrylic resin, polyimide resin, novolac resin, and laminated bodies thereof. The thickness of the planarization film 180 is not particularly limited, but is preferably, for example, 10 nm or more and 5 μm or less. The thickness of the planarization film 180 is more preferably 30 nm or more and 3 μm or less.

[0043] The first substrate 111 and the second substrate 112 are preferably transparent substrates. The transparent substrate may be any substrate that is transparent to visible light. Examples of the transparent substrate include a glass substrate and a plastic substrate.

[0044] The first electrode 121 and the second electrode 122 are preferably transparent electrodes. The transparent electrodes can be made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), tin oxide (SnO), or an alloy thereof.

[0045] The first electrode 121 and the second electrode 122 are electrodes disposed in a planar manner on the entire surface of each substrate, that is, so-called solid electrodes, but may be patterned.

[0046] The polarization module 11 is driven in an ECB mode, for example. The ECB mode controls the birefringence of the liquid crystal layer 160 by applying a voltage, and is classified into a horizontal alignment type, a vertical alignment type (VA), and a HAN type according to the difference in the initial alignment state of the liquid crystal molecules. In these modes, a voltage is applied vertically to the liquid crystal layer. Note that FFS (Fringe Field Switching) mode and IPS (In-Plane Switching) mode, in which a voltage is applied horizontally, can also be considered as a type of ECB mode in the sense that the birefringence of the liquid crystal layer is controlled by applying a voltage. The polarization module 11 according to the embodiment uses a positive liquid crystal and adopts a vertical electric field type ECB mode in which the initial alignment of the liquid crystal molecules is horizontal.

[0047] The liquid crystal layer 160 is composed of a liquid crystal material containing liquid crystal molecules 1601. The amount of light transmitted can be controlled by applying a voltage to the liquid crystal layer 160 and changing the alignment state of the liquid crystal molecules 1601 according to the applied voltage. Note that a state in which the voltage applied to the liquid crystal layer 160 is less than the threshold value is referred to as a no-voltage applied state.

[0048] The liquid crystal molecules 1601 may preferably have a positive dielectric anisotropy (Δε) defined by the following formula: Δε = (dielectric constant in the long axis direction) - (dielectric constant in the short axis direction)

[0049] The liquid crystal molecules 1601 may have a negative dielectric anisotropy (Δε). In the polarization module 11 according to the embodiment, liquid crystal molecules having a positive dielectric anisotropy (Δε) are used. Note that liquid crystal molecules having a positive dielectric anisotropy are also called positive type liquid crystals, and liquid crystal molecules having a negative dielectric anisotropy are also called negative type liquid crystals. The long axis direction of the liquid crystal molecules is the direction of the slow axis.

[0050] It is also preferable that the liquid crystal molecules 1601 satisfy the following formula (1). K11 ≧ γ1 / {(Δε) 2 x1.3x10 11} Formula (1) (In the formula, K11 represents the splay elastic constant (pN) of the liquid crystal molecule 1601. γ1 represents the rotational viscosity coefficient (mPa·sec) of the liquid crystal material. Δε represents the dielectric anisotropy of the liquid crystal molecule 1601.)

[0051] That is, it is preferable to select liquid crystal molecules having a dielectric anisotropy Δε that satisfies the relationship of formula (1) as liquid crystal molecules 1601. This makes it possible to shorten the response time, particularly when voltage is switched from on to off, and obtain polarization module 11 that can follow ultra-high speed image switching.

[0052] The dielectric anisotropy Δε of the liquid crystal molecules 1601 may be within a range satisfying the above formula (1), but from the viewpoint of realizing a high-speed response, it is preferable that the dielectric anisotropy Δε is 0.1 or more. More preferably, the dielectric anisotropy Δε is 0.11 or more. Furthermore, from the viewpoint of cell thickness control taking into account practical production, it is preferable that the dielectric anisotropy Δε is 0.22 or less. More preferably, the dielectric anisotropy Δε is 0.2 or less.

[0053] From the viewpoint of achieving a faster response, the liquid crystal molecules 1601 preferably have a splay elastic constant K11 of 5 pN or more. More preferably, the splay elastic constant K11 is 10 pN or more. From the same viewpoint, the splay elastic constant K11 is preferably 30 pN or less. More preferably, the splay elastic constant K11 is 20 pN or less. The most preferable range for the splay elastic constant K11 is 10 to 20 pN.

[0054] From the viewpoint of achieving a faster response, the liquid crystal material constituting the liquid crystal layer 160 preferably has a rotational viscosity coefficient γ1 of 100 mPa·second (mPa·s) or less. More preferably, the rotational viscosity coefficient γ1 is 60 mPa·second or less. From the same viewpoint, the rotational viscosity coefficient γ1 is preferably 20 mPa·second or more. More preferably, the rotational viscosity coefficient γ1 is 30 mPa·second or more. The most preferable range for the rotational viscosity coefficient γ1 is 30 to 60 mPa·second.

[0055] The thickness (cell thickness) of the liquid crystal layer 160 is preferably 100 nm to 10 μm, more preferably 500 nm to 5 μm, and further preferably 1 μm to 3 μm.

[0056] Alignment films 141, 142 are disposed on both sides (the observation surface side and the back surface side) of the liquid crystal layer 160. Furthermore, an insulating film may be provided between the alignment film and the electrode. In the polarization module 11 according to the embodiment, an insulating film 131 and an alignment film 141 are provided between the first electrode 121 and the liquid crystal layer 160, in that order from the electrode side, and an insulating film 132 and an alignment film 142 are provided between the second electrode 122 and the liquid crystal layer 160, in that order from the electrode side.

[0057] The alignment films 141 and 142 have a function of controlling the alignment of liquid crystal molecules contained in the liquid crystal layer 160. When the voltage applied to the liquid crystal layer 160 is less than the threshold voltage (including no voltage application), the alignment films mainly function to control the alignment of the liquid crystal molecules in the liquid crystal layer 160. As the material for the alignment films 141 and 142, materials commonly used in the field of liquid crystal display panels, such as polymers having polyimide in the main chain, polymers having polyamic acid in the main chain, and polymers having polysiloxane in the main chain, can be used.

[0058] The insulating films 131 and 132 are preferably, for example, inorganic insulating films. Examples of the inorganic insulating film that can be used include inorganic films (relative dielectric constant ε=5 to 7) such as silicon nitride (SiNx) and silicon oxide (SiO2), and laminated films thereof. The thickness of each insulating film is not particularly limited, but is preferably, for example, 10 nm or more and 500 nm or less. More preferably, the thickness of each insulating film is 30 nm or more and 300 nm or less.

[0059] The retardation plate 120 to be combined with the optical laminate 110 may have an in-plane retardation Ro or a thickness direction retardation Rth. The retardation plate 120 is preferably a uniaxial retardation plate having an in-plane retardation Ro. The absolute value |Ro| of the in-plane retardation Ro is preferably 50 nm or more. More preferably, the absolute value |Ro| is 80 nm or more, and even more preferably, 100 nm or more. In addition, the absolute value |Ro| is preferably 500 nm or less. More preferably, the absolute value |Ro| is 400 nm or less, and even more preferably, 350 nm or less.

[0060] A λ / 4 phase difference plate (also referred to as a λ / 4 plate) or a λ / 2 phase difference plate (also referred to as a λ / 2 plate) is suitable as the phase difference plate 120. In the polarization module 11 according to the embodiment, a λ / 4 plate is used as the phase difference plate 120, as described later.

[0061] The retarder 120 may have a single-layer structure or a laminated structure of two or more layers. When the display panel 12 and the polarization module 11 are combined, the retarder 120 is preferably disposed on the display panel 12 side.

[0062] The thickness of the retardation plate 120 is not particularly limited, but is preferably, for example, 10 μm or more and 500 μm or less, and more preferably, 50 μm or more and 200 μm or less.

[0063] The material of the retardation plate 120 is not particularly limited, and for example, a stretched polymer film, a liquid crystal material with fixed orientation, a thin plate made of an inorganic material, etc. The method of forming the retardation plate 120 is also not particularly limited.

[0064] When the retardation plate 120 is formed from a polymer film, the formation method may be, for example, a solvent casting method, a melt extrusion method, or the like. The formation method of the retardation plate 120 may be a method of simultaneously forming a plurality of retardation plates 120 by a co-extrusion method. As long as the retardation plate 120 exhibits a desired retardation, the retardation plate 120 may be unstretched or may be stretched. The stretching method is not particularly limited, and may be a roll-to-roll tensile stretching method, a roll-to-roll compression stretching method, a tenter horizontal uniaxial stretching method, an oblique stretching method, a vertical and horizontal biaxial stretching method, or a special stretching method in which stretching is performed under the action of a shrinkage force of a heat-shrinkable film.

[0065] When the retarder 120 is made of a liquid crystalline material, the retarder 120 may be formed, for example, by applying a liquid crystalline material onto a substrate film that has been subjected to an orientation treatment, and then fixing the orientation. As long as the retarder 120 exhibits a desired phase difference, the retarder 120 may be formed by a method that does not involve a special orientation treatment on the substrate film, or by fixing the orientation, peeling the substrate film off, and transferring the substrate to another film. Furthermore, the retarder 120 may be formed by a method that does not fix the orientation of the liquid crystalline material. When the retarder 120 is formed of a non-liquid crystalline material, the retarder 120 may be formed by the same method as when the retarder 120 is formed of a liquid crystalline material.

[0066] A film that is stretched and contains a material with positive intrinsic birefringence (intrinsic refractive index anisotropy) as a component can be appropriately used as the retardation plate 120. Examples of materials with positive intrinsic birefringence include polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, triacetyl cellulose, diacyl cellulose, and cycloolefin polymer.

[0067] The method for producing the optical laminate 110 and the method for producing the polarizing module 11 using the optical laminate 110 and the retardation plate 120 are not particularly limited, and any method commonly used in the field of liquid crystal panels can be used.

[0068] The AR panel driver 15 controls the application of a voltage to the liquid crystal layer 160 under the control of a controller 20, which will be described later. This allows the polarization module 11 to be switched between a plurality of polarization states.

[0069] In the polarization module 11 according to the embodiment, the optical laminate 110 performs phase difference switching between λ / 2 and 0. In the polarization module 11 according to the embodiment, a λ / 4 plate is used as the retardation plate 120, and is arranged so that the slow axis of the optical laminate 110 and the slow axis of the retardation plate 120 are perpendicular to each other. This allows the polarization module 11 according to the embodiment to perform phase difference switching between +λ / 4 and -λ / 4.

[0070] In this case, a polarizing film having either a -λ / 4 phase difference or a +λ / 4 phase difference is attached to the polarizing glasses 200. As an example, if the phase of +λ / 4 in the polarization module 11 is a first polarization state and the phase of -λ / 4 is a second polarization state, a polarizing film having a +λ / 4 phase difference is attached to the polarizing glasses 200. As a result, when the polarization module 11 is in the first state (phase difference switching state is +λ / 4), the phase difference is +λ / 2 (=(+λ / 4)+(+λ / 4)), and the polarized glasses 200 transmit polarized light. When the polarization module 11 is in the second state (phase difference switching state is -λ / 4), the phase difference is 0 (=(-λ / 4)+(+λ / 4)), and the polarized glasses 200 do not transmit polarized light. When the first polarization state and the second polarization state of the polarization module 11 in the phase difference switching between +λ / 4 and -λ / 4 are reversed, a polarizing film with a -λ / 4 phase difference can be attached to the polarized glasses 200.

[0071] The controller 20 includes a timing controller 21, a memory 22, an image generating unit 23, and a data selector 25. The memory 22 includes a storage area 221 for storing first image data D1 input from the outside as an image signal Sg1.

[0072] The image generating unit 23 generates the second image data D2 from the first image data D1 stored in the memory 22. To generate the second image data D2 from the first image data D1, the image generating unit 23 uses a look-up table (LUT) 24, which will be described later. The image generating unit 23 may be configured by an electric circuit, or may be realized by software control.

[0073] The timing controller 21 inputs the synchronization signal Sg2 at a predetermined timing to the memory 22, the data selector 25, and the AR panel driving unit 15. The predetermined timing is, for example, for each frame of the first image data D1 included in the signal Sg1.

[0074] The data selector 25 obtains the first image data D1 stored in the memory 22 and the second image data D2 generated by the image generating unit 23. The data selector 25 alternately outputs the first image data D1 and the second image data D2 to the display panel driving unit 16 at a timing according to the synchronization signal Sg2. As a result, the first image based on the first image data D1 and the second image based on the second image data D2 are displayed on the display panel 12 in a time-division manner alternately at a timing based on the synchronization signal Sg2. The timing based on the synchronization signal Sg2 is, for example, every frame. The switching of the display of the first image and the second image is not limited to every frame, and may be fast enough so that the first image and the second image are not perceived individually when the observer A does not wear the polarized glasses 200 and flicker is not felt. The switching of the display of the first image and the second image is preferably 180 Hz or more.

[0075] The AR panel driving unit 15 alternately switches the polarization state of the polarization module 11 between the first polarization state and the second polarization state at a timing based on the synchronization signal Sg2, in synchronization with switching between the first image and the second image on the display panel 12. As an example, the AR panel driving unit 15 switches the polarization state of the polarization module 11 between the first polarization state and the second polarization state for each frame. That is, the polarization module 11 switches to the first polarization state when the first image is displayed on the display panel 12, and switches to the second polarization state when the second image is displayed on the display panel 12.

[0076] Generating the second image data D2 from the first image data D1 in the image generating section 23 means converting at least a part of the first image data D1 to generate the second image data D2, which is an image that is synthesized with the first image so that the first image is not perceived. Preferably, the second image data D2 may be an image that is synthesized with the first image so that the first image is not perceived in a state where there is an influence of luminance due to the responsiveness of the display panel 12. In other words, the second image data D2 is an image that is displayed on the display panel 12 and synthesized with the first image viewed by the observer A so that the first image is not perceived by the observer A. The image generating section 23 converts the pixel values ​​of predefined pixels among the pixels shown in the first image data D1 in a predefined relationship. The predefined pixels are, for example, all the pixels of the first image. The second image is, for example, an image in which all the pixels have a specific pixel value (for example, a gray image) when synthesized with the first image.

[0077] Fig. 5 is a diagram showing an example of a first image 301 and a second image 302. The first image 301 in Fig. 5 is an image of 6 x 6 dots in which "A" is represented by black pixels and the other pixels are white pixels. As an example, the image generating unit 23 generates the second image data D2 by inverting the first image data D1 for the first image 301. In the example of Fig. 5, the second image 302 is an image of 6 x 6 dots in which "A" is represented by white pixels and the other pixels are black pixels.

[0078] 5 are alternately displayed on the display panel 12 in a time-division manner, so that when observer A does not wear the polarized glasses 200, a composite image (gray image) of the first image 301 and the second image 302 is perceived, and only the first image 301 is not viewed. When observer A wears the polarized glasses 200, the second image 302 is not viewed, and only the first image 301 is viewed. This makes it possible for the first image 301 to be viewed only when the polarized glasses 200 are worn, or only by a user wearing the polarized glasses 200.

[0079] The LUT 24 defines the correspondence relationship between pixel values ​​of the first image data D1 and the second image data D2. The image generating unit 23 generates the second image data D2 by converting the pixel value of each pixel of the first image data D1 into a pixel value defined by the LUT 24. Preferably, the correspondence relationship between the pixel values ​​of the first image data D1 and the second image data D2 is determined by measuring, using a luminance meter, combinations of the gradations of the first image data D1 and the second image data D2 displayed with the same settings of the display panel 12, the responsiveness of the polarization module 11, and the display settings of the display panel 12 such as overdrive and gamma value as those of the display device 100, so that the integral luminance for each combination is constant. As another example, the correspondence relationship between the pixel values ​​of the first image data D1 and the second image data D2 may be defined by a function or an arithmetic expression. As another example, the correspondence between pixel values ​​of the first image data D1 and the second image data D2 may be learned by machine learning, such as by deep learning, such that the image generating unit 23 uses the first image data D1 as an input value and outputs the second image data D2.

[0080] 6 is a diagram showing an example of the LUT 24. The LUT 24 defines a pixel value 242 of the second image data D2 corresponding to a pixel value 241 of the first image data D1. Specifically, pixel values ​​255, ...X, Y, ...0 of the second image data D2 are defined for pixel values ​​0, ...127, 128, ...255 of the first image data D1, respectively.

[0081] The brightness (luminance) at which observer A views each pixel of display panel 12 is the amount of light that observer A receives from that pixel over a predetermined period of time. Therefore, the brightness at which observer A views each pixel of display panel 12 is the integral value of the luminance change of that pixel over a predetermined period of time. The integral value of the luminance of a pixel over a predetermined period of time is also called "integral luminance" to distinguish it from the instantaneous luminance of that pixel. By alternately displaying the first image and the second image on display panel 12 in a time-division manner, the luminance of each pixel viewed by observer A when not wearing polarized glasses 200 is the integral luminance of that pixel in the first image and the second image.

[0082] 7 and 8 are diagrams for explaining the luminance perceived by observer A when he is not wearing polarized glasses 200. In FIGS. 7 and 8, the horizontal axis represents the passage of time. The vertical axis represents the luminance of the display panel 12 in gradation value. In FIGS. 7 and 8, the second image data D2 has a correspondence relationship with the first image data D1 that is defined in the LUT 24 of FIG. 6. That is, the pixel value of the second image corresponding to a pixel having a pixel value of 0 gradation in the first image is 255 gradation, and the pixel value of the second image corresponding to a pixel having a pixel value of 255 gradation in the first image is 0 gradation.

[0083] In Fig. 7 and Fig. 8, times t0 to t1, times t1 to t2, times t2 to t3, and times t3 to t4 are all time T for one frame. A first image is displayed on the display panel 12 during times t0 to t1 and times t2 to t3, which is defined as a first image period T1. A second image is displayed on the display panel 12 during times t1 to t2 and times t3 to t4, which is defined as a second image period T2. The polarization state of the polarization module 11 is switched from the second polarization state to the first polarization state at times t0 and t2, and is switched from the first polarization state to the second polarization state at times t1 and t3. Note that in Fig. 7 and Fig. 8, it is assumed that the response of the polarization module 11 is sufficiently fast.

[0084] Here, attention is paid to a pixel whose pixel value is 0 gradation in the first image and a pixel whose pixel value is 255 gradation in the first image. The former pixel is called the first target pixel, and the latter pixel is called the second target pixel. The first target pixel has a pixel value of 255 gradation in the second image, and the second target pixel has a pixel value of 0 gradation in the second image. Curve L1 in FIG. 7 represents the change in instantaneous luminance of the first target pixel. Curve L2 in FIG. 8 represents the change in instantaneous luminance of the second target pixel.

[0085] 7, when the display is switched to the first image at time t0, the luminance of the first target pixel changes from the gradation value before the switch (255 gradations) to 0 gradations. The target pixel being at 0 gradations indicates a state in which the light emitted from the backlight 13 is blocked. When the display is switched from the first image to the second image at time t1, the luminance of the first target pixel changes from 0 gradations to 255 gradations of the second image. The target pixel being at 255 gradations indicates a state in which the light emitted from the backlight 13 is transmitted.

[0086] 8, when the display is switched to the first image at time t0, the luminance of the second target pixel changes from the gradation value before the switch (gradation 0) to gradation 255. When the display is switched from the first image to the second image at time t1, the luminance of the second target pixel changes from gradation 255 to gradation 0 of the first image.

[0087] The luminance perceived by viewer A of the first target pixel when he / she is not wearing polarized glasses 200 is the integral value of curve L1. The integral value of curve L1 is the area S1 hatched in Fig. 7. The luminance perceived by viewer A of the second target pixel when he / she is not wearing polarized glasses 200 is the integral value of curve L2. The integral value of curve L2 is the area S2 hatched in Fig. 8.

[0088] For the first target pixel, when the luminance of the first target pixel in the second image is 255 gradations, the luminance perceived by observer A when not wearing the polarized glasses 200 is maximum. For the second target pixel, when the luminance of the second target pixel in the second image is 0 gradations, the luminance perceived by observer A when not wearing the polarized glasses 200 is minimum.

[0089] Since the pixel values ​​of the pixels of the first image data D1 and the second image data D2 have the corresponding relationship defined in the LUT 24 of Fig. 6, the area S1 in Fig. 7 is equal to the area S2 in Fig. 8. Therefore, the maximum luminance of the first target pixel and the minimum luminance of the second target pixel that can be viewed by the viewer A when he / she is not wearing the polarized glasses 200 are equal. In other words, since the LUT 24 defines the pixel values ​​of the second image data D2 with respect to the pixel values ​​of the first image data D1 so that the integrated luminances are equal, it is possible to make the entire image be viewed at a specific integrated luminance when the viewer A is not wearing the polarized glasses 200.

[0090] The relationship between the pixel values ​​of the first image data D1 and the pixel values ​​of the second image data D2 is not limited to the table format shown in Fig. 6. As another example, it may be an arithmetic formula into which the pixel values ​​of the first image data D1 are substituted to obtain the pixel values ​​of the second image data D2. The LUT 24 may define the relationship between the pixel values ​​of the first image data D1 and the second image data D2 for each of the R, G, and B pixels, or may define the relationship between the pixel values ​​of the first image data D1 and the second image data D2 commonly for the R, G, and B pixels.

[0091] The LUT24 does not need to define the correspondence of the pixel values ​​of the second image data D2 to all pixel values ​​of the first image data D1, but may define the correspondence of at least some pixel values. For example, the LUT24 may define the correspondence of the second image data D2 to a number of pixel values ​​less than all of the pixel values ​​of the first image data D1, and the other pixel values ​​may be obtained by linear interpolation or the like. Furthermore, a LUT24 may be prepared for each temperature, and a LUT24 corresponding to the temperature on the display panel 12 may be used. Alternatively, a LUT24 may be prepared for each of a number of specific temperatures, and a linear interpolation may be performed according to the temperature on the display panel 12 to use the LUT24.

[0092] Fig. 9 is a flow chart showing an example of a method of controlling the display device 10 in the display system 100. The memory 22 stores first image data D1 inputted from the outside as an image signal Sg1. The control in Fig. 9 is started, for example, when an instruction to display the first image data D1 is given by an input device (not shown). As an example, the instruction to display may include a designation as to whether the first image data D1 is to be displayed as a secret image or in a normal display. As another example, the first image data D1 may include information indicating that it is a secret image, and the control in Fig. 9 may be performed in the display system 100 by reading the information indicating that it is secret information from the first image data D1.

[0093] The image generation unit 23 generates second image data D2 from the first image data D1 stored in the memory 22 (step S101), and inputs the second image data D2 to the data selector 25. The timing controller 21 outputs a synchronization signal Sg2 for each frame of the first image data D1 included in the signal Sg1.

[0094] Data selector 25 outputs a control signal to display panel driver 16 to display a first image from first image data D1 stored in memory 22 on display panel 12 at the timing indicated by synchronization signal Sg2 (step S103). Also, at the same timing indicated by synchronization signal Sg2, AR panel driver 15 sets polarization module 11 to the first polarization state (step S105).

[0095] When receiving a synchronization signal Sg2 indicating the timing of the next frame from the timing controller 21 (YES in step S107), the data selector 25 outputs a control signal to the display panel driver 16 to cause the display panel 12 to display a second image from the second image data D2 (step S109). At the same timing indicated by the synchronization signal Sg2, the AR panel driver 15 sets the polarization module 11 to the second polarization state (step S111).

[0096] When the synchronization signal Sg2 indicating the timing of the next frame is received from the timing controller 21 (YES in step S113), the process is repeated from step S103. That is, until the synchronization signal Sg2 indicating the timing of the next frame is not received from the timing controller 21 (NO in step S107 or NO in step S113), the data selector 25 outputs a control signal to the display panel drive unit 16 in accordance with the synchronization signal Sg2 from the timing controller 21 so as to alternately display the first image and the second image on the display panel 12. In addition, the AR panel drive unit 15 alternately switches the polarization state of the polarization module 11 between the first polarization state and the second polarization state.

[0097] 10 and 11 are schematic diagrams showing an example of the display of the display panel 12, the polarization state of the polarization module 11, and an image viewed by a viewer A. Fig. 10 shows an image perceived when the viewer A wears polarized glasses 200. Fig. 11 shows an image perceived when the viewer A does not wear the polarized glasses 200.

[0098] 10 and 11, a first image 301 is displayed on the display panel 12 from time t0 to t1 and from time t2 to t3. Furthermore, the polarization module 11 switches to a first polarization state at times t0 and t2. In Fig. 10 and 11, a second image 302 is displayed on the display panel 12 from time t1 to t2 and from time t3 to t4. Furthermore, the polarization module 11 switches to a second polarization state at times t1 and t3.

[0099] When observer A wears the polarized glasses 200 (FIG. 10), the first image 301 displayed at times t0 to t1 and times t2 to t3 is visible to observer A through the polarized glasses 200. The second image 302 displayed at times t1 to t2 and times t3 to t4 does not pass through the polarized glasses 200 and is not visible to observer A. Therefore, when observer A wears the polarized glasses 200, only the first image 301 is visible from times t0 to t1 and times t2 to t3, and nothing is visible from times t1 to t2 and times t3 to t4. As a result, only the first image 301 is visible to observer A wearing the polarized glasses 200.

[0100] When the observer A is not wearing the polarized glasses 200 (FIG. 11), the observer A visually recognizes both the first image 301 displayed at times t0-t1 and t2-t3 and the second image 302 displayed at times t1-t2 and t3-t4. Therefore, when the observer A is not wearing the polarized glasses 200, the observer A visually recognizes the first image 301 and the second image 302, switching frame by frame. As a result, the observer A, who is not wearing the polarized glasses 200, perceives a third image 303, which is a combination of the first image 301 and the second image 302. The first image 301 and the second image 302 have the same integral luminance when displayed for each pixel. Therefore, the third image 303 is an image with a uniform gradation as a whole, such as a gray image.

[0101] By using the display system 100 according to the embodiment, the viewer A can perceive the first image only when wearing the polarized glasses 200. When the viewer A does not wear the polarized glasses 200, an image (second image) different from the first image is also viewed, and the viewer A cannot perceive the first image. This allows the first image to be perceived only by a specific user who can wear the polarized glasses 200. Or, the first image can be perceived only at a specific timing when the polarized glasses 200 can be worn. The first image can be, for example, secret information or private information, thereby ensuring the confidentiality of the information. In this way, in the display system 100 according to the embodiment, the confidentiality of a specific image can be guaranteed without impairing the usability of the user, simply by the presence or absence of the polarized glasses 200.

[0102] [Second embodiment] 12 is a schematic diagram showing a partial configuration of a display system 100 according to a second embodiment. Images are written to the display panel 12 in a direction D by the display panel driver 16 sequentially applying voltages based on image data to each pixel. The direction D represents the scanning direction of the display panel 12, and is a direction from the upper end 12U to the lower end 12D of the display panel 12. That is, images are written to the display panel 12 in a sequential manner from the upper end 12U to the lower end 12D.

[0103] In the display system 100 according to the second embodiment, the polarization module 11 is divided into a plurality of segments in the direction D. In the example of FIG. 12, the polarization module 11 is divided into an upper segment 11A and a lower segment 11B. The upper end 11AU of the upper segment 11A coincides with the upper end 12U of the display panel 12, and the lower end 11BD of the lower segment 11B coincides with the lower end 12D of the display panel 12. The lower end 11AD of the upper segment 11A coincides with the upper end 11BU of the lower segment 11B, which coincide with the center of the display panel 12. The AR panel driver 15 controls the polarization states of the upper segment 11A and the lower segment 11B independently.

[0104] 13 is a schematic diagram for explaining the relationship between the display of the display panel 12 and the polarization state of the polarization module 11 in the display system 100 according to the second embodiment. The horizontal axis (Y axis) of FIG. 13 represents the passage of time. The vertical axis (Y axis) of FIG. 13 represents the positions in direction D of the polarization module 11 and the display panel 12. The position of 0 (Y=0) on the vertical axis Y is the bottom end 12D of the display panel 12 and the bottom end 11BD of the lower segment 11B. The negative direction of the Y axis coincides with direction D.

[0105] The display panel driver 16 applies voltages based on image data to the display panel 12 in sequence from the upper end 12U to the lower end 12D in one frame time T, and an image is written on the display panel 12. The writing direction E indicated by an arrow in FIG. 13 indicates the writing position and timing on the display panel 12. Writing of the first image 301 starts from the upper end 12U of the display panel 12 at times t0 and t2, and writing is completed up to the lower end 12D of the display panel 12 at times t1 and t3 after a time T. Writing of the second image 302 starts from the upper end 12U of the display panel 12 at times t1 and t3, and writing is completed up to the lower end 12D of the display panel 12 at times t2 and t4 after a time T. Therefore, at the start times t0 and t2 of writing of the first image 301, the first image 301 is not displayed below the upper end 12U of the display panel 12, and the second image 302 before switching is displayed. At start times t1 and t3 of writing the second image 302, the second image 302 is not displayed below the upper end 12U of the display panel 12, and the first image 301 before switching is displayed.

[0106] At this time, when the AR panel driving unit 15 switches the polarization state of the entire polarization module 11 to the first polarization state at times t0 and t2 based on the synchronization signal Sg2 from the timing controller 21, when the observer A is wearing the polarized glasses 200, the first image 301 is displayed only on the upper end 12U of the display panel 12, and the observer A views a screen below the upper end 12U on which the second image 302 is displayed. In other words, if the entire polarization module 11 is switched to the first polarization state at the same timing as the start of writing of the first image 301, the first image 301 may not be properly viewed.

[0107] In this regard, the AR panel driving unit 15 according to the second embodiment switches the polarization state of the upper segment 11A and the polarization state of the lower segment 11B by shifting them in the order of direction D, based on the synchronization signal Sg2 from the timing controller 21. In this example, the AR panel driving unit 15 switches the polarization state by shifting the lower segment 11B from the upper segment 11A by half a frame (T / 2).

[0108] As a result, the upper segment 11A is in the first polarization state at least at the timing when the first image 301 is displayed on the upper end 12U of the display panel 12, and the first image 301 is visible at least on the upper end 12U when the observer A wears the polarized glasses 200. On the other hand, at that timing, the lower segment 11B does not switch to the first polarization state but is in the second polarization state, so that when the observer A wears the polarized glasses 200, the second image 302, which remains displayed, is less visible.

[0109] Preferably, the AR panel driving unit 15 switches the polarization state of the upper segment 11A a predetermined time after the start of writing an image to the display panel 12. By switching the polarization state of the upper segment 11A a predetermined time after the start of writing an image to the display panel 12, writing to a large area of ​​the display panel 12 is completed at the time when the upper segment 11A switches to the first polarization state.

[0110] As an example, the AR panel driving unit 15 switches the upper segment 11A to the first polarization state after a time difference dt1 (dt1 < T) from times t0 and t2. The AR panel driving unit 15 shifts by half a frame (T / 2) from the upper segment 11A and switches the lower segment 11B to the first polarization state after a time difference dt2 (dt2 = dt1 + T / 2) from times t0 and t2. Also, the AR panel driving unit 15 switches the upper segment 11A to the second polarization state after a time difference dt1 (dt1 < T) from times t1 and t3. The AR panel driving unit 15 shifts by half a frame (T / 2) from the upper segment 11A and switches the lower segment 11B to the second polarization state after a time difference dt2 (dt2 = dt1 + T / 2) from times t1 and t3.

[0111] FIGS. 14 and 15 are diagrams for explaining the luminance that observer A visually recognizes when wearing the polarized glasses 200 in the relationship of FIG. 13. In FIGS. 14 and 15, the horizontal axis represents the passage of time. The vertical axis represents the luminance of the display panel 12 as a gradation value. Curves L2 in FIG. 14 and L3 in FIG. 15 represent the change in the instantaneous luminance of the pixel whose pixel value of the first image 301 is 255 gradations (the second target pixel described above). FIG. 14 represents the change in the instantaneous luminance when the second target pixel is located near the upper end 12U of the display panel 12. The curve L2 in FIG. 14 is the same as the curve L2 in FIG. 8. FIG. 15 represents the change in the instantaneous luminance when the second target pixel is located near the lower end 12D of the display panel 12.

[0112] When the second target pixel is located near the upper end 12U of the display panel 12 (FIG. 14), the first image 301 is written at time t0, t2 when the writing of the first image starts, and is displayed until time t1, t3. Since the upper segment 11A is in the first polarization state after the time difference dt1, when the observer A wears the polarized glasses 200, the first image 301 is viewed from time t0, t2 after the time difference dt1 to time t1, t3. Since the writing of the second image 302 starts at time t1, t3, the second image 302 is viewed near the upper end 12U for the period from time t0, t2 until time T has elapsed. Therefore, the luminance viewed by the observer A in this case is the integral value of the curve L2 during the period during which the curve L2 is viewed. The integral value of the curve L2 during the period during which the curve L2 is viewed is the area S3 indicated by hatching in FIG. 14.

[0113] 13, the polarization state of the lower segment 11B is switched half a frame (T / 2) behind the upper segment 11A. Therefore, the positional relationship of the second target pixel located near the upper end 12U of the display panel 12 to the upper segment 11A is equal to the positional relationship of the second target pixel located slightly below the center of the display panel 12 to the lower segment 11B. Therefore, even when the second target pixel is located slightly below the center of the display panel 12, the luminance perceived by observer A when wearing the polarized glasses 200 is the area S3 in FIG.

[0114] When the second target pixel is located near the lower end 12B of the display panel 12 (Fig. 15), at the time delayed by the writing time from the start times t0 and t2 of writing the first image, that is, after one frame time T from the times t0 and t2 (times t1 and t3), the first image 301 is written and is displayed until times t2 and t4. After a time difference dt2 (dt2 < T) from time t2, the upper segment 11A becomes the first polarization state, and when a time T has elapsed (t2 + dt2 + T), the first polarization state switches to the second polarization state. Therefore, when the observer A wears the polarized glasses 200, the first image 301 is visible during the period from time t3 until the end of the first polarization state of the upper segment 11A. Since the second image 302 is written until time t3, the second image 302 is visible during the period from a time difference dt2 (dt2 < T) from time t2 until time t3. Therefore, in this case, the luminance visually recognized by the observer A is the integral value of the period of the curve L3 that is visible. The integral value of the period of the curve L3 that is visible is the area S4 indicated by hatching in Fig. 15.

[0115] In the example of Fig. 13, the lower segment 11B is shifted by half a frame (T / 2) from the upper segment 11A and the polarization state switches. Therefore, the positional relationship of the second target pixel located near the lower end 12B of the display panel 12 with respect to the lower segment 11B is the same as the positional relationship of the second target pixel located slightly above the center of the display panel 12 with respect to the upper segment 11A. Therefore, even when the second target pixel is located slightly above the center of the display panel 12, the luminance visually recognized by the observer A when wearing the polarized glasses 200 is the area S4 in Fig. 15.

[0116] By dividing the polarization module 11 into a plurality of segments in the direction D and switching the polarization state by shifting them in order, it is possible to reduce the area of ​​the display panel 12 that is included in the range of the polarization module 11 in the first polarization state and in which rewriting to the first image 301 has not been completed, compared to when the polarization state of the entire polarization module 11 is switched uniformly at the start of each frame. Therefore, the difference (unevenness) in the luminance of the first image 301 viewed when the observer A wears the polarized glasses 200 is suppressed, compared to when the polarization state of the entire polarization module 11 is switched uniformly at the start of each frame. As a result, the display quality when the observer A wears the polarized glasses 200 can be improved.

[0117] The difference in timing for switching the polarization state between the upper segment 11A and the lower segment 11B is not limited to 1 / 2 (T / 2) of one frame time, and may be another time difference. The difference in timing for switching the polarization state between the upper segment 11A and the lower segment 11B may be set according to the response of writing on the display panel 12, or may be set according to the response speed of the polarization module 11.

[0118] The control of switching the polarization state of the upper segment 11A and the lower segment 11B at different timings may include control of switching the polarization state of the upper segment 11A and the lower segment 11B at the same time, that is, control of switching the polarization state of the entire polarization module 11 uniformly. That is, the AR panel driving unit 15 may switch the polarization state of the upper segment 11A and the lower segment 11B simultaneously. The division of the polarization module 11 in the direction D is not limited to two divisions. The polarization module 11 may be divided into three or more divisions in the direction D.

[0119] [Third embodiment] As another example, generating the second image data D2 from the first image data D1 in the image generation unit 23 may involve converting the pixel values ​​of pixels belonging to at least a partial area of ​​the first image data D1 in accordance with the LUT 24, and setting the pixel values ​​of pixels belonging to areas other than the partial area to a predetermined specific gradation value regardless of the pixel value.

[0120] 16 is a diagram for explaining an example of a method for generating second image data D2 from first image data D1 in a display system 100 according to a third embodiment. The image generating unit 23 converts pixel values ​​of specific pixels in the first image data D1 into pixel values ​​defined by the LUT 24. The specific pixels are pixels belonging to one or more areas 301a, 301b, 301c, and 301d defined in advance for the first image 301. The image generating unit 23 inverts black and white for each pixel in the areas 301a, 301b, 301c, and 301d, as in the first embodiment.

[0121] In addition, the image generating unit 23 sets pixels in areas other than the areas 301a, 301b, 301c, and 301d to a predefined gradation such as black (gradation 0). The color to be converted is not limited to black (gradation 0) and may be other gradations. For example, different gradations may be specified for each of RGB.

[0122] In the display system 100 according to the first embodiment, all pixels of the first image data D1 are converted into the second image data D2 having a specific relationship, so that the pattern of the first image 301 may appear in the second image 302. Therefore, when the viewer A is not wearing the polarized glasses 200, and blinks or moves his / her gaze suddenly, the pattern of the first image 301 may be perceived momentarily due to the gaze tracking integral effect.

[0123] In contrast, in the display system 100 according to the third embodiment, the area in the second image 304 in which the pattern of the first image 301 may appear is limited to a certain area, and does not appear in other areas. Therefore, the pattern of the first image 301 is difficult to perceive even if there is blinking or a sudden movement of the line of sight, etc. This can further improve the concealment of the first image 301.

[0124] In the display system 100 according to the third embodiment, when the viewer A is not wearing the polarized glasses 200, a fourth image 305 obtained by combining the first image 301 and the second image 304 is perceived. Fig. 17 is a schematic diagram showing an example of the display of the display panel 12 and the polarization state of the polarization module 11, and an example of an image perceived by the viewer A in the display system 100 according to the third embodiment, and shows the image perceived when the viewer A is not wearing the polarized glasses 200.

[0125] 17, a first image 301 is displayed on the display panel 12 from time t0 to t1 and from time t2 to t3. Furthermore, the polarization module 11 switches to a first polarization state at times t0 and t2. A second image 304 is displayed on the display panel 12 from time t1 to t2 and from time t3 to t4. Furthermore, the polarization module 11 switches to a second polarization state at times t1 and t3.

[0126] When the observer A is not wearing the polarized glasses 200, the observer A perceives a fourth image 305 in which the first image 301 and the second image 304 are combined. The sum of the pixel values ​​of the pixels in the areas 301a, 301b, 301c, and 301d of the first image 301 and the second image 304 is equal. The areas other than the areas 301a, 301b, 301c, and 301d are monochromatic areas in which the pixel values ​​of the second image 304 are black (0 gradation). Therefore, although the areas other than the areas 301a, 301b, 301c, and 301d of the fourth image 305 are images that include the pattern of the first image 301, the areas 301a, 301b, 301c, and 301d are entirely a specific gradation, such as a gray image. Therefore, when the observer A is not wearing the polarized glasses 200, the observer A does not perceive the first image 301. This makes it possible to ensure the confidentiality of the first image 301.

[0127] The areas 301a, 301b, 301c, and 301d may have any size and shape that makes the pattern of the first image 301 difficult to perceive even when blinking or a sudden line of sight is shifted. Preferably, the areas 301a, 301b, 301c, and 301d are smaller than the first image 301 and are discontinuous. In the example of FIG. 16, the areas 301a, 301b, 301c, and 301d are arranged in a houndstooth pattern in the first image 301. This makes it more difficult for the viewer A to perceive the pattern of the first image 301 when he or she is not wearing the polarized glasses 200. In addition, the area in which pixel values ​​are converted is smaller than the entire first image 301, so that the amount of calculation in the image generating unit 23 is reduced.

[0128] The sizes of the areas 301a, 301b, 301c, and 301d do not necessarily have to be constant (the same). As another example, the sizes of the areas 301a, 301b, 301c, and 301d may be determined according to the content included in the first image 301. As an example, when the first image 301 includes characters, the sizes may correspond to the font sizes. In this case, the image generating unit 23 may, for example, identify the font size from the information included in the image signal Sg1, and determine the sizes of the areas 301a, 301b, 301c, and 301d based on the correspondence between the font sizes and the area sizes stored in advance.

[0129] [Fourth embodiment] As another example, generating the second image data D2 from the first image data D1 in the image generating unit 23 may involve dividing the first image 301 into a plurality of areas and changing the pixel values ​​of the pixels belonging to each area to predefined pixel values. In this case, the LUT 24 defines the correspondence of pixel values ​​for each pixel value of the pixels belonging to the area. The pixel values ​​of the pixels belonging to the area may be, for example, the range of gradation for each area, that is, the minimum and maximum values ​​of gradation. As another example, other characteristics such as the average value of gradation may be used.

[0130] 18 is a diagram showing another example of the LUT 24. The LUT 24 according to the fourth embodiment defines a plurality of data sets 243, 244, 245 of pixel values ​​of the second image data D2 corresponding to a pixel value 241 of the first image data D1. Specifically, the LUT 24 according to the fourth embodiment defines a data set (data set A) 243 of pixel values ​​127, ..., 0 of the second image corresponding to each pixel value in the range of pixel values ​​0 to 127 of the first image data D1, a data set (data set B) 244 of pixel values ​​255, ..., 0 of the second image corresponding to each pixel value in the range of pixel values ​​0 to 255 of the first image data D1, and a data set (data set C) 245 of pixel values ​​255, ..., 64 of the second image corresponding to each pixel value in the range of pixel values ​​64 to 255 of the first image data D1.

[0131] The relationship between the pixel values ​​of the first image data D1 and the pixel values ​​of the second image data D2 is not limited to the table format shown in FIG. 18. As another example, it may be a plurality of tables prepared for each range of pixel values ​​of the first image data D1, or a plurality of arithmetic expressions. Furthermore, the LUT 24 may be one that defines the relationship between the pixel values ​​of the first image data D1 and the pixel values ​​of the second image data D2 for each of the R, G, and B color pixels, or may be one that defines the relationship between the pixel values ​​of the first image data D1 and the pixel values ​​of the second image data D2 commonly for each of the R, G, and B color pixels.

[0132] The number of areas may be two or more. As an example, the image generating unit 23 divides the first image 301 into predefined areas, such as 10 pixels by 10 pixels. The size of the area is not limited to a specific size and may be determined according to predefined conditions. The image generating unit 23 determines a data set of pixel values ​​of the second image for each area by calculating the maximum and minimum pixel values ​​for each area. The image generating unit 23 converts the pixel values ​​of each pixel belonging to each area of ​​the first image data D1 using the data set of pixel values ​​of the second image determined for that area, thereby generating the second image data D2.

[0133] 18 is used, for an area in which the minimum and maximum pixel values ​​are between 0 and 127, the image generating unit 23 can select either data set A or data set B. Similarly, for an area in which the minimum and maximum pixel values ​​are between 64 and 255, the image generating unit 23 can select either data set B or data set C. In such a case, the image generating unit 23 may select a data set that is specified in advance, may select randomly, or may select in accordance with a specific user operation.

[0134] Preferably, a data set is selected in which the difference between the pixel values ​​of the first image data D1 and the pixel values ​​of the second image data D2 is small. This makes it possible to suppress the influence of crosstalk due to responses and to make it easier for the observer A to view the first image 301 when wearing the polarized glasses 200.

[0135] In the display system 100 according to the fourth embodiment, it becomes possible to use a different data set of pixel values ​​of the second image for each area of ​​the first image 301. By generating the second image data D2 in this manner, the gradation may differ for each area in the composite image of the first image 301 and the second image perceived by the viewer A when he / she is not wearing the polarized glasses 200. In other words, by generating the second image data D2 in this manner, it is possible to make the viewer A perceive a third image including a plurality of gradations when he / she is not wearing the polarized glasses 200.

[0136] <3. Notes> The present invention is not limited to the above-described embodiment, and various modifications are possible. [Explanation of symbols]

[0137] 10: display device, 11: polarization module, 12: display panel, 20: controller, 30: display, 100: display system, 200: polarized glasses, D1: first image data (image data), D2: second image data

Claims

1. A display and a polarization module overlaid on the display, the polarization module being capable of actively switching a polarization state between a first polarization state and a second polarization state; A controller, The controller: generating second image data from the first image data; displaying a first image based on the first image data and a second image based on the second image data on the display in a time-division manner; and switching the polarization state of the polarization module in synchronization with the timing of the time division so that the polarization state is the first polarization state when the first image is displayed and the second polarization state is the second polarization state when the second image is displayed. Display device.

2. the first polarization state causes the first image to be viewed by an observer through polarized glasses worn by the observer; The second polarization state does not allow the observer to view the second image through the polarized glasses. The display device according to claim 1 .

3. generating the second image data includes converting the second image data into a grayscale having a predefined relationship to the grayscale of the image data; The display device according to claim 1 .

4. Generating the second image data includes converting the gradation of pixels belonging to at least a partial area of ​​the image data into a different gradation having a predefined relationship according to the gradation, and setting the gradation of pixels belonging to an area other than the partial area to a specific gradation that is predefined regardless of the gradation. The display device according to claim 1 .

5. The generating of the second image data includes dividing the image data into a plurality of areas, and changing the gradation of each area to a gradation having a predetermined relationship according to the gradation of pixels belonging to each area. The display device according to claim 1 .

6. Switching the polarization state of the polarization module includes dividing the polarization module into a plurality of segments along a scanning direction of the display, and switching the polarization states of the plurality of segments with a time difference in order along the scanning direction. The display device according to claim 1 .

Images