WO2021049566A1

WO2021049566A1 - Display device

Info

Publication number: WO2021049566A1
Application number: PCT/JP2020/034270
Authority: WO
Inventors: 慶成岩浪; 鈴木　剛; 安藤　伸也
Original assignee: 凸版印刷株式会社
Priority date: 2019-09-12
Filing date: 2020-09-10
Publication date: 2021-03-18
Also published as: JP2021043365A

Abstract

Provided is a display device configured by superposing, from the display viewing side, a first display panel (10) comprising a non-light emitting display element in which a light modulation element performs display by reflecting external light, an opaque light diffusion layer (30) having light transparency, and a second display panel (20) comprising a light emitting display element in which a light emitting element performs display by performing direct modulation.

Description

Display device

The present invention relates to a display device capable of selectively using different methods of different power consumption.

Thin display devices equipped with liquid crystal display panels and organic EL display panels are widely used as the main elements of personal digital assistants (PDAs) such as smartphones, tablet PCs, and wearable terminals. For small terminals such as wristwatches that are worn on the wrist, the capacity of the battery that can be installed is small, and it is difficult to operate for a long time with a display method that consumes a lot of power. It is requested.

A proposal relating to a type of device in which a non-emission display element (liquid crystal: LCD) and a light emission display element (organic electroluminescence: OLED) having different display methods are provided in the same display device is known.

The present invention does not switch different display methods using the same pixel according to the brightness of the usage environment, but selects a display method having different pixels with different arrangements and resolutions according to the difference in the display target. Provided is a display device suitable for a usage pattern in which power consumption is reduced.

The display device according to one aspect of the present invention is a first display panel composed of a non-emission display element in which a light modulation element reflects external light to display from the observation side of the display, and an opaque light diffusion having translucency. The layer and the second display panel composed of a light emitting display element in which the light emitting element directly modulates and displays are superimposed.

According to the present invention, it is possible to provide a display device suitable for a usage mode in which power consumption is reduced by selecting a display method having different pixels having different arrangements and resolutions according to a difference in display target.

FIG. 1 is a cross-sectional view showing a schematic configuration of the display device 100 according to the first embodiment. FIG. 2 is a cross-sectional view showing a schematic structural example of a transflective liquid crystal display device (first display panel 10). FIG. 3 is an explanatory diagram showing a display example by the first display panel 10. FIG. 4 is a cross-sectional view showing a schematic structural example of the second display panel 20. FIG. 5 is a cross-sectional view showing a schematic configuration of the display device 100 according to the second embodiment. FIG. 6 is an enlarged cross-sectional view of an example of the dimming panel 50. FIG. 7 is a diagram showing an axial direction (vibration direction) exhibited by the incident light to the display light in the usage mode (1) of the display device. FIG. 8 is a diagram showing an axial direction (vibration direction) exhibited by the incident light to the display light in the usage mode (2) of the display device. FIG. 9 is a diagram showing an axial direction (vibration direction) exhibited by the incident light to the display light in the usage mode (3) of the display device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, the drawings are schematic, and for convenience of explanation, the relationship with the plane dimensions, the ratio of the thickness of each layer, and the like may be exaggerated to a size different from the actual scale. Further, the embodiments shown below exemplify a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention describes the materials, shapes, structures, etc. of the constituent parts as follows. It is not specific to anything. The technical idea of the present invention may be modified in various ways within the technical scope specified by the claims stated in the claims.

<Embodiment 1>
FIG. 1 is a cross-sectional view showing a schematic configuration of the display device 100 according to the first embodiment.

The display device 100 is a first display panel 10 composed of a non-emission display element in which a light modulation element reflects external light to display from the observation side of the upper display in the figure, and opaque light diffusion having translucency. Layer 30, a second display panel 20 composed of a light emitting display element in which the light emitting element directly modulates and displays.
Is superimposed.

<First display panel 10>
A typical example of the first display panel 10 composed of a non-emission display element is a liquid crystal display device. The liquid crystal display device is a reflective liquid crystal display device that does not require a special observation light source such as a backlight or edge light, and the back light is radiated from the back of the liquid crystal panel (opposite to the observer). There are usage patterns such as a transmissive liquid crystal display device of a type that uses display light and a semi-transmissive liquid crystal display device of a type that selectively switches and adopts them.

Of the power consumption of liquid crystal display devices, special observation light sources such as backlights and edge lights occupy a very high weight, and reflection display using external light (illumination light, ambient light such as sunlight) saves energy. It is effective in terms of points. However, when using the display device in a dark place, vision that depends on the observation light source is required. Hereinafter, the semitransmissive liquid crystal display device will be mainly described.

FIG. 2 is a cross-sectional view showing a schematic structural example of the antitransmissive liquid crystal display device (first display panel 10). The structure is such that a reflector 13 also serving as an electrode, a liquid crystal element 12, a transparent electrode 14, a glass substrate 11, and a polarizing plate 15 are stacked in this order on a glass substrate 11. Depending on the type of liquid crystal and the specifications of the device, a color filter, a retardation film, an optical path modulation film having a prism array, and other optical films may be used together. Further, in FIG. 2, the back side (opposite side to the observer) of the liquid crystal element 12 is not the same member as the transparent electrode 14 having high translucency represented by ITO, but an electrode (referred to as a reflective electrode) made of a semitransmissive reflective film. However, there is also a configuration in which the back side of the liquid crystal element 12 is also used as the transparent electrode 14, and a reflecting plate (semi-transmissive reflecting film) as a separate member is placed on the back side of the glass substrate 11.

In the usage mode as a reflective liquid crystal display device, the external light a incident on the device is reflected by the reflector 13 and emitted to the observer side as the display light b. In FIG. 2, the display light b is shown as scattered light centered on the specular reflection direction of the external light a, but an optical path control member for appropriately controlling the emission direction and range of the display light b is used. In some cases. Further, in order to appropriately set the resolution of the display light b, the ratio of forward scattering and backward scattering is such that a large amount of light scattering occurs when the external light a is incident and no light scattering occurs when the display light b is emitted. Is also controlled as appropriate.

In the usage mode as a transmissive liquid crystal display device, the second display panel 20 composed of the light emitting display element of FIG. 1 is not used as an image display by itself, but as a backlight (surface light source) of the liquid crystal display device that defines an image display pattern. use. In this case, the second display panel 20 does not form a specific pattern by selecting light emission / non-light emission, brightness, and hue for each pixel, but exhibits a uniform single color (white) light emission state over the entire screen. Drive to.

When a TN type liquid crystal, which is a typical liquid crystal element, is used in a transmissive liquid crystal display device, a liquid crystal in which the molecules are twisted by 90 degrees is sandwiched between two polarizing plates. Arrangement of two polarizing plates with the directions of the linear polarization axes orthogonal to each other so that light can pass through when no voltage is applied and light is blocked when voltage is applied (and vice versa). By appropriately setting the relationship of the phase difference accompanying the behavior of the liquid crystal molecules according to the application / non-application of voltage, the liquid crystal functions as a light shutter.

In the reflective liquid crystal display device, the incident light (external light a) that has passed through the polarizing plate 15 is modulated by the liquid crystal element 12 in phase difference, reflected by the reflecting plate 13, and displayed again through the liquid crystal elements 12 to the polarizing plate 15. It emits as light b. When two polarizing plates are arranged on the front and back sides of the liquid crystal element 12, if the two polarizing plates are passed through each of the two polarizing plates at the time of incident to the time of reflection a total of 4 degrees, the light absorption at the time of passing is large and the harmful effect of light loss is remarkable. Therefore, two polarizing plates are not required on the front and back sides of the liquid crystal element 12, and the liquid crystal molecules when passing through one polarizing plate 15 having the same direction of the linear polarization axes twice (at the time of incident and at the time of exit). A reflective liquid crystal display device of a type in which the phase difference between the outside light a and the display light b is set according to the behavior of the above has also been developed. On the other hand, strict control (contrast) of the direction of the linear polarization axis is prioritized over the problem of light loss, and two polarizing plates are still used on the front and back of the liquid crystal element 12, and the back side (for the observer). As a polarizing plate on the opposite side), there is also a type of reflective liquid crystal display device that employs a reflective polarizing plate having a function of reflecting light other than a specific transmission axis (or reflecting only light of a specific reflection axis). To do.

In the usage mode as a transmissive liquid crystal display device, when the incident light c from the backlight (surface light source) is pattern-modulated and emitted as display light in FIG. 2, the polarizing plate 15 passes through the polarizing plate 15 once, but the liquid crystal. In order to impart a shutter function to the element, it is required that the light emitted from the second display panel 20 has a linearly polarized light component. In this case, it is necessary to dispose the polarizing plate on the back surface side of the liquid crystal element 12.

FIG. 3 is a display example by the first display panel 10. It is preferable to easily display characters with a small number of pixels, and in the illustrated example, numbers and alphabets with 7 segments are displayed. The black and white may be inverted in the figure. In the display example, the time display as a wristwatch can be considered, but a static display with less movement may be used. In terms of saving power consumption, it is preferable to use it as a reflective liquid crystal display device that does not use a backlight.

<Opaque light diffusion layer 30 with translucency>
The light diffusion layer 30 is colorless in order to clarify the contrast between the portion where the liquid crystal element shows a light-shielding state (black) and the portion showing a light-transmitting state (white) in the visual sense of the display image by the reflective liquid crystal display device. Make the transparent background opaque white. Further, when a transparent electrode 14 made of ITO or the like is used instead of the reflector 13 that also serves as an electrode on the back side of the liquid crystal element 12, it also functions as a reflecting layer for generating reflected light as display light. Therefore, it also has a function of controlling the range of diffuse reflection according to the light diffusivity.

In the visual sense of the display image by the transmissive liquid crystal display device (or the second display panel 20), the light rays serving as the display light source incident from the back side (opposite side to the observer) of the light diffusion layer 30 are not blocked. Responsible for the function of spreading and transmitting. It also has a function of forming an image display pattern light generated by the second display panel 20 and visualizing it to the observer. By dispersing the light diffusing agent in the adhesive to give the light diffusing layer 30 an adhesive function, the light diffusing layer 30 also serves as an adhesive layer, so that the first display panel 10 and the second display panel 20 are laminated at the same time. Can be integrated.

The light diffusion layer that also serves as the adhesive layer is a filler containing polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, ethyl polyacrylate resin, polymethyl methacrylate resin, etc., which are widely used as adhesives. It is prepared by dispersing a diffusing agent such as glass sphere, titanium oxide, silica, or calcium carbonate with an alcohol-based solvent such as acetone, ethyl acetate, or ethanol.

<Second display panel 20>
A typical example of the second display panel 20 including a light emitting display element in which the light emitting element directly modulates and displays is an organic EL (OLED) display. The organic EL display panel includes a substrate provided with a thin film transistor (TFT), a pixel electrode provided with a thin film transistor for each pixel, a partition wall formed by partitioning the pixel electrode, and a light emitting medium layer formed above the pixel electrode. , A counter electrode formed above the light emitting medium layer is provided. The light emitting medium layer includes, for example, a hole transport layer, an interlayer, and a light emitting layer.

Organic EL display panels are prone to problems such as reflection of external light and reflection of the background. Therefore, it is known that these problems can be prevented by providing a circular polarizing plate having a λ / 4 plate on the observation side (visual recognition side). As a general circular polarizing plate, a retardation film (typically, a λ / 4 plate) typified by a cycloolefin (COP) resin film is used, and its slow phase axis is approximately relative to the absorber absorption axis. Those laminated so as to form an angle of 45 ° are known.

In the present invention, the organic EL display panel as the second display panel 20 is not arranged on the observation side (visual side) of the display device 100, but is arranged on the back side of the first display panel 10 and the light diffusion layer 30. Therefore, there is no influence of external light reflection or background reflection.

When the second display panel 20 (organic EL display panel) is used as a backlight as a surface light source of the first display panel 10 (transmissive liquid crystal display device), not for defining an image display pattern, it is mainly a reflective type. Since the first display panel 10 used in the form of the liquid crystal display device has only one polarizing plate 15 corresponding to the front polarizing plate, it is assumed that the light emitted from the second display panel 20 has passed through the rear polarizing plate. It is required to have the same characteristics.

The surface light source is not a form in which the edge light light incident from the incident end surface of the light guide plate is propagated and emitted from the entire emission surface toward the liquid crystal display device, but for each pixel arranged in a matrix in the emission surface. The light emitting medium layer functions as a direct backlight.

When the light emitted from the second display panel 20 is incident on the first display panel 10 (transmissive liquid crystal display device) as incident light c from the backlight (surface light source) shown in FIG. 2, it functions as a front polarizing plate. A retardation film and a polarizing plate are arranged on the exit surface of the second display panel 20 in order to modulate the light emitted from the second display panel 20 so that the polarization is orthogonal to the transmission axis of the polarizing plate 15.

FIG. 4 is a cross-sectional view showing a schematic structural example of the second display panel 20 (organic EL display panel). The organic EL display panel is formed above the substrate 25a provided with the thin film transistor (TFT), the pixel electrode 23 provided with the thin film transistor for each pixel, the partition wall 24 formed by partitioning the pixel electrode 23, and the pixel electrode 23. The light emitting medium layer and the counter electrode 26 formed above the light emitting medium layer are provided. Here, the light emitting medium layer includes, for example, a hole transport layer 21, an interlayer (not shown), and a light emitting layer 22.

The circularly polarizing plate 29 is laminated on the surface (diffusion layer 30 side) of the glass substrate 25b on the upper side of the second display panel 20 (organic EL display panel). The circular polarizing plate 29 of the present embodiment includes a polarizing plate 28 and a retardation plate 27 arranged on one side of the polarizing plate 28. If necessary, protective films may be arranged on both sides of the polarizing plate 28. Further, light diffusion layers may be arranged on both sides of the retardation plate 27 (not shown).

The retardation plate 27 has a refractive index characteristic of nx> ny and has a slow phase axis. nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and ny is the refractive index in the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advancing axis direction). is there. The polarizing plate 28 and the retardation plate 27 are laminated so that the absorption axis of the polarizing plate 28 and the slow axis of the retardation plate 27 form a predetermined angle. As the retardation plate 27, λ / 4 capable of converting linearly polarized light ⇔ circularly polarized light is preferable.

The polarizing plate 28 may be a reflective polarizing plate having a transmission axis and a reflection axis. The reflective polarizing plate is arranged so that its transmission axis is substantially perpendicular to the transmission axis of the polarizing plate 15 corresponding to the front polarizing plate in the first display panel 10 (transmissive liquid crystal display device).

<Embodiment 2>
FIG. 5 is a cross-sectional view showing a schematic configuration of the display device 100 according to the second embodiment.

In the light diffusing layer 30 in the display device 100 of the first embodiment, the light diffusing property, the light reflecting property, and the light transmitting property are fixed and invariant, and the light diffusing layer of another design (formulation, composition) is used for modulating the optical characteristics. It is necessary to prepare 30. In the second embodiment, instead of the light diffusion layer 30, a dimming panel 50 including a dimming element capable of switching between a transparent state and an opaque state is arranged.

FIG. 6 is an enlarged cross-sectional view of an example of the dimming panel 50.

The dimming layer 52 is sandwiched between a transparent base material 55 having a dimming layer 52 including a liquid crystal material capable of switching haze in two or more stages according to an applied voltage and having a transparent electrode 56 for applying a voltage to the dimming layer 52. It is a configured configuration.

In the present embodiment, as a liquid crystal display element having high light utilization efficiency without using a polarizing plate, instead of switching between a translucent state and a light-shielding state, a liquid crystal transmissive state (transparent state) and a scattered state (opaque state) are used. It is preferable to use a liquid crystal display element that switches between the two. A polymer network liquid crystal (PNLC) having liquid crystal molecules arranged in voids formed inside a polymer network made of a resin formed in a three-dimensional network, or a polymer network liquid crystal (PNLC), or a polymer in which liquid crystal molecules are polymers. A typical one using a polymer dispersed liquid crystal (PDLC: Polymer Dispersed Liquid Crystal) having a configuration dispersed inside is described, and PNLC will be described below.

In manufacturing the light control panel 50 provided with the light control layer 52 made of PNLC, a mixture of a liquid crystal and a photopolymerizable compound (monomer) is sandwiched between a pair of transparent electrode substrates 53, and ultraviolet rays are emitted under certain conditions. Upon irradiation, the photopolymerizable compound is transformed into a polymer by photopolymerization, and a polymer network having innumerable fine domains (polymer voids) is formed in the liquid crystal by photopolymerization and cross-linking.

The drive voltage of the PNLC generally depends on the structural characteristics of the polymer network (domain size and shape, film thickness of the polymer network, etc.), and the relationship between the structure of the polymer network and the obtained light transmission and scattering degree. In, the drive voltage is determined. In order to construct a PNLC that can obtain sufficient light transmission and scattering degree in a voltage region of 100 V or less, each domain must have an appropriate size and be uniform, and the shape must be uniform. It is necessary to form a polymer network so as to. In the present invention, the domain size depending on the polymer network structure is controlled to be 3 μm or less, preferably 2 μm or less, and more preferably about 1 μm.

The light control panel 50 includes a light control layer 52 made of PNLC and a transparent conductive film 53 (a, b). The transparent conductive film 53 (a, b) sandwiches the dimming layer 52 (PNLC), and a voltage is applied from the feeding portion (not shown) to the dimming layer 52 (PNLC) to achieve a high haze (scattering state). ), Low haze (transparency state) is changed.

The dimming layer 52 is preferably manufactured with a thickness of 5 μm to 50 μm (preferably about 10 μm to 25 μm). In the transparent conductive film 53, a transparent conductive film 53 formed by forming a transparent electrode 56 made of a transparent conductive material such as ITO, IZO, or an organic conductive material on a transparent base material 55 is opposed to each other on the transparent electrode 56 side. The dimming layer 52 is sandwiched between the two. The suitable thickness of the transparent electrode 56 is approximately 80 nm or more and 150 nm or less. In PNLC, it is also possible to express an arbitrary halftone haze state according to the applied voltage.

There are two known dimming layers 52 made of liquid crystal elements, a normal mode and a reverse mode, depending on the mode of use. The normal mode refers to a mode in which a transmission state is obtained by applying a voltage (ON) and a scattering state is obtained by removing a voltage (OFF). Further, the reverse mode refers to a mode in which a transmission state is established by voltage removal (OFF) and a scattering state is achieved by voltage application (ON). In the case of the reverse mode, a film base material having an alignment film formed on the transparent electrode 56 is required. As the alignment film, either a horizontal alignment film or a vertical alignment film may be used as long as it is a conventionally known alignment film, and it can be appropriately selected according to the application.

A polyethylene terephthalate (PET) film, a polyethylene (PE) film, a polycarbonate (PC) film, or the like can be used as the transparent base material 55 constituting the transparent conductive film 53. The thickness of the transparent base material 55 is preferably about 50 to 200 μm.

A metal oxide such as ITO is generally used for the transparent conductive layer 56 constituting the transparent conductive film 53, but a low-resistance conductive polymer can be used instead of ITO. As the conductive polymer, it is preferable to use a material containing a polyanion doped in a π-conjugated conductive polymer exemplified by PEDOT / PSS.

The dimming panel 50 is in an opaque state (high haze scattering state) when displayed by the first display panel 10, and is in a transparent state (or low haze scattering state) when displayed by the second display panel 20. It is desirable to switch and use it so that it becomes (state). In consideration of power saving, when the display state by the first display panel 10 occupies most of the display state, the light control panel 50 is adjusted so that an opaque state (high haze scattering state) is maintained without applying a voltage (ON). The optical panel 50 is preferably in the normal mode.

<Usage form of display device 10>
Hereinafter, various usage patterns of the display device 10 will be described.

(1) Using the first display panel 10 as a reflective liquid crystal display device The usage pattern of the display device 10 in which the resolution of the display image is low and the power consumption is the lowest is the first method in which the second display panel is turned off in a bright place. The display panel 10 is used as a reflective liquid crystal display device. The display image by the reflective liquid crystal display device has a small amount of information in a 7-segment display with few dynamic elements such as a time display of a digital clock, and is suitable for suppressing battery consumption. At this time, the light diffusion layer 30 (or the light control panel 50) is in an opaque state (high haze scattering state).

(2) Using the first display panel 10 as a transmissive liquid crystal display device When confirming the display by the first display panel 10 (liquid crystal display device) in a dark place, the front light component that illuminates the liquid crystal display screen from the observer side. Since there is no such situation, the second display panel 20 is used as the backlight (surface light source) of the liquid crystal display device. Both the first display panel 10 and the second display panel 20 are in the ON state, but the second display panel 20 is also driven so as to exhibit a uniformly solid single color (white) light emitting state with few dynamic elements. Is fine. At this time, the light diffusing layer 30 (or the dimming panel 50) is in a scattered state that is not excessively high haze so that the liquid crystal display screen can be evenly illuminated without reducing the irradiation brightness by blocking the backlight. It is desirable to present.

(3) Using the Second Display Panel 10 as an Organic EL (OLED) Display The usage pattern of the display device 10 which has a high resolution of the display image and consumes a lot of power including full-color display and dynamic display is the second display panel 20. It is a form used as an organic EL (OLED) display. The first display panel 10 is turned off to make it transparent, and the light diffusing layer 30 (or the dimming panel 50) shields the display light by the organic EL (OLED) to block the display light and does not reduce the irradiation brightness. It is desired to exhibit a transparent state (or a low-haze scattering state) so as not to reduce the resolution of the display by (OLED).

Table 1 shows a summary of the above usage patterns (1) to (3).

The axial directions (vibration directions) of the incident light to the display light in the above usage modes (1) to (3) are shown in FIGS. 7 to 9, respectively. FIG. 7 is a diagram showing an axial direction (vibration direction) exhibited by the incident light to the display light in the usage mode (1) of the display device. FIG. 8 is a diagram showing an axial direction (vibration direction) exhibited by the incident light to the display light in the usage mode (2) of the display device. FIG. 9 is a diagram showing an axial direction (vibration direction) exhibited by the incident light to the display light in the usage mode (3) of the display device.

In FIGS. 7 to 9, the display device assumed for the sample is LCD (polarizing plate, liquid crystal,) 10 → diffusion layer 30 (polarizing plate panel 50) → reflective polarizing plate → OLED (polarizing plate) from the observation side (top). , Phase difference plate) 20 is provided, and the amount of phase modulation associated with the passage of light rays from the liquid crystal display and the retardation plate is assumed to be λ / 2 and λ / 4, respectively. The arrows indicating the axial direction (vibration direction) are black (when the traveling direction of the light beam is "up → down") and white (when the traveling direction of the light beam is "down → up") according to the traveling direction of the light beam. ).

External light and light emitted from an organic EL (OLED) display panel are light (omnidirectional light) having components in all vibration directions. Since omnidirectional light can be divided into two orthogonal components, it is indicated by a cross arrow in the figure.

Normally, the display state should be set according to the usage mode (1), which consumes less information and power consumption, such as the time display of a wristwatch with a reflective liquid crystal display, and the usage mode (2) should be used when checking the time in a dark place. ) Is adopted, and the usage mode (3) is appropriately adopted only when it is desired to confirm image information (moving image) having a large amount of information, thereby saving battery power in a small terminal.

Not limited to the sample display devices illustrated in FIGS. 7 to 9, the liquid crystal mode (TN, STN, VA, IPS) in the liquid crystal display device and the combination with the corresponding retardation film and polarizing film are adopted. Various changes can be made to the display device of the type corresponding to the displayed display method within a range that does not deviate from the gist of the present invention.

The present invention is not limited to the above embodiment, and can be variously modified at the implementation stage without departing from the gist thereof. In addition, each embodiment may be carried out in combination as appropriate, and in that case, the combined effect can be obtained. Further, the above-described embodiment includes various inventions, and various inventions can be extracted by a combination selected from a plurality of disclosed constituent requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, if the problem can be solved and the effect is obtained, the configuration in which the constituent requirements are deleted can be extracted as an invention.

Claims

From the observation side of the display
A first display panel (10) composed of a non-emission display element in which a light modulation element reflects external light for display.
Opaque light diffusing layer (30) with translucency,
A second display panel (20) composed of a light emitting display element in which the light emitting element directly modulates and displays.
A display device having a structure in which the above are superimposed.
The display device according to claim 1, wherein the first display panel (10) is a reflective or semi-transmissive liquid crystal display device.
The display device according to claim 1 or 2, wherein the first display panel (10) is a 7-segment display.
The display device according to claim 1, wherein the second display panel (20) is an organic electroluminescence element.
The display device according to claim 2, wherein the second display panel (20) functions as a backlight of the liquid crystal display device.
A reflective polarizing plate (28) is provided on the second display panel (20) side of the light diffusion layer (30).
The reflective polarizing plate (28) has a transmission axis that transmits one of the two linearly polarized light having vibration planes of light in directions orthogonal to each other and a reflection axis that reflects the other linearly polarized light. Polarized light
A retardation film and a polarizing plate are provided on the light diffusion layer (30) side of the second display panel (20).
The polarizing plate has a transmission axis that transmits linearly polarized light of one of two linearly polarized light having vibration planes of light in directions orthogonal to each other.
The display device according to claim 1, wherein the reflective polarizing plate (28) and the transmission axis of the polarizing plate are in the same direction.
The display device according to claim 1, wherein the light diffusion layer (30) is a layer having adhesiveness for joining the first display panel (10) and the second display panel (20).
The display device according to claim 1, wherein a dimming panel (50) including a dimming element capable of switching between a transparent state and an opaque state is arranged in place of the light diffusing layer (30).
The dimming panel (50) is
A transparent base material (55) provided with a dimming layer (52) containing a liquid crystal material capable of switching haze in two or more stages according to an applied voltage, and having a transparent electrode for applying a voltage to the dimming layer (52). The display device according to claim 8, wherein the dimming layer (52) is sandwiched between the display devices.
The dimming panel (50) is switched so as to be in an opaque state when displaying by the first display panel (10) and to be in a transparent state when displaying by the second display panel (20). , The display device according to claim 8 or 9.