JP2007071948A - Display device and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device and an electronic device excellent in display quality and excellent in information concealment.
A display device includes a pair of transparent electrodes, an electroluminescent display unit capable of double-sided display having a light emitting layer sandwiched between the pair of transparent electrodes, and adjacent to at least one surface of the display unit. And a liquid crystal light control sheet that can be switched between a transparent state and a non-transparent state. In addition, the electronic device controls the display device, a casing to which the display device is attached, and an operation for inverting information displayed on the display device so that both sides of the display device can be visually recognized. Means and switching means for switching between the transparent state and the non-transparent state of the liquid crystal light control sheet.
[Selection] Figure 1

Description

  The present invention relates to a display device that displays information by light emission of a plurality of electroluminescence (hereinafter abbreviated as EL) displays, and an electronic device including the display device.

  In recent years, an electroluminescence (EL) display device has been expected among flat display devices. Compared with liquid crystal display devices, this EL display device has many characteristics suitable for a display, such as high response speed, wide viewing angle, good visibility unique to a self-luminous element, and a wide temperature range that can be driven. Currently, adoption of organic EL display devices is being studied in electronic devices that require many display devices.

  Among EL display devices currently in practical use, there are an inorganic EL display device using an inorganic material as a light emitting material and an organic EL display device using an organic material as a light emitting material. As a conventional technique using an inorganic EL display device as a display device of an electronic apparatus, Patent Document 1 can be cited. The double-insulated inorganic EL display element described in this publication has a high luminance and a long life, and has been put to practical use in a vehicle-mounted display. On the other hand, Patent Document 2 can be cited as a conventional technique using an organic EL display device as a display device of an electronic device. In this publication, an organic EL display device is used in an electronic device such as a portable terminal device, and a technique for displaying only the minimum necessary information when the device is not used or in the case of a portable terminal device is disclosed. .

  For example, Patent Document 3 proposes a new practical example of a transparent display device by making a pair of electrodes and a support substrate forming an inorganic EL display element transparent. Since an inorganic EL display element which is a self-luminous element does not require a backlight unlike a liquid crystal display device, a transparent display device can be easily provided with a simple structure. Furthermore, for example, Non-Patent Document 1 discloses a foldable portable terminal provided with a transparent organic EL display device. This portable terminal displays information on the front and back two screens using a single transparent organic EL display device. Conventional folding used as a main / sub display using two liquid crystal display devices. Compared to a portable mobile terminal, it can be expected to be smaller and lighter.

JP 7-263140 A JP-A-12-105573 JP 7-263140 A SID 2004 51.3: 2.1-inch QCIF + Dual Emission AMOLED Display having Transparent Cathode Electrode

  However, when the EL display device is used as a transparent display device, transmitted light from the back surface must be taken into consideration. Since the transmitted light incident from the back surface is transmitted to the EL display device and visually recognized by the user, it has an important influence on display quality such as a decrease in contrast and a chromaticity shift. Further, the display information that can be visually recognized by the user can be visually recognized by other observers from the back side, and there is a problem in terms of information leakage. For example, Non-Patent Document 1 proposes improving the display quality by attaching a circularly polarizing plate to an organic EL display device to shield transmitted light from the back surface. However, currently used circularly polarizing plates have a transmittance of about 50%, so that the light emitted from the EL display device is attenuated as well as the transmitted light from the back surface. A new problem of lowering brightness occurs.

  An object of the present invention is to solve the problems of a conventional transparent EL display device and an electronic device provided with the same as a display unit, and to provide a display device and an electronic device excellent in display quality and excellent in information concealment. That is.

A display device according to the present invention includes:
An electroluminescence display unit capable of double-sided display having a pair of transparent electrodes and a light emitting layer sandwiched between the pair of transparent electrodes;
And a liquid crystal light control sheet arranged adjacent to at least one surface of the display unit and capable of switching between a transparent state and a non-transparent state.

  Further, the display unit is composed of an organic electroluminescence element capable of displaying both front and back sides.

  Furthermore, the display unit is composed of an inorganic electroluminescence element capable of displaying both front and back sides.

  The liquid crystal light control sheet may include a pair of transparent electrodes and a liquid crystal layer sandwiched between the pair of transparent electrodes.

  Furthermore, the voltage applied between the pair of transparent electrodes of the liquid crystal light control sheet is controlled to change the transparent state / non-transparent state of the liquid crystal layer, so that the liquid crystal light control sheet is transparent / non-transparent. The state can be switched.

The electronic device according to the present invention is
The display device;
A housing to which the display device is attached so that both sides of the display device are visible;
Control means for controlling an operation of inverting information displayed on the display device;
Switching means for switching the transparent state / non-transparent state of the liquid crystal light control sheet;
It is characterized by having.

A lid covering one surface of both surfaces of the display device;
You may further provide the detection part which detects that the said one surface of the said display apparatus was covered with the said cover body.
In this case, when the one surface of the display device is covered with the lid, the control unit reverses information displayed on the display device, and the switching unit includes the display device. When the one surface is covered with the lid, the liquid crystal light control sheet can be switched between a transparent state and a non-transparent state.

  According to the display device and the electronic apparatus according to the present invention, the transmitted light from the back surface is controlled by the liquid crystal light control device by combining the EL display unit (hereinafter abbreviated as EL panel) and the liquid crystal light control sheet. Shield with light sheet to improve surface display quality, especially contrast. In addition, since information that should be visually recognized on the front side cannot be observed from the back side, it is effective in concealing information. Furthermore, it is possible to provide a display device and an electronic device that are superior in display quality and conceal information more than a conventional double-sided display EL display device.

  Hereinafter, a display device and an electronic apparatus using the display device according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(Embodiment 1)
A display device according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is an example of the display device of this embodiment, and is a cross-sectional view perpendicular to the light emitting surface. The display device 100 has a structure in which an EL panel 110 and a liquid crystal light control sheet 120 are bonded together with a bonding region 130 having transparency.

  The EL panel 110 can be of any structure in which at least the light emitting layer 112 is sandwiched between a pair of transparent substrates 111a and 111b. The EL panel 110 may be an EL display element that can extract light from both the front and back surfaces, and may be an organic EL element or an inorganic EL element. FIG. 2 is a schematic plan view of the display device according to Embodiment 1 of the present invention, showing a passive matrix drive type EL panel. In this case, on the transparent substrates 111a and 111b, a plurality of transparent electrodes 113a parallel to the light emitting surface and extending in parallel to the first direction, and parallel to the light emitting surface and extending in the first direction A plurality of transparent electrodes 113b extending in parallel to a second direction orthogonal to each other and provided to face the transparent electrodes 113a. The EL panel 110 may be an active matrix drive system. In the case of the active matrix driving method, one of the transparent substrates 111a and 111b is connected to a thin film transistor. As this thin film transistor, a low temperature polysilicon, an amorphous silicon thin film transistor or the like is used. Furthermore, the organic thin-film transistor comprised by the thin film containing an organic material may be sufficient. Furthermore, a color display device can be obtained by forming the light emitting layer 112 by color-coding the phosphors showing the respective emission colors of RGB at each intersection (pixel) between the transparent electrodes 113a and 113b. Alternatively, in the case of a color display device according to another example, RGB light emitting layers may be stacked. Further, in the case of another color display device, RGB can be displayed using a color filter and / or a color conversion filter after creating a display device with a single color or two color light emitting layers.

  FIG. 3 shows an example of the basic structure of the organic EL element. The organic EL element 200 is formed by laminating a transparent hole injection electrode 202, a hole transport layer 203, a light emitting layer 204, and an electron injection electrode 205 in this order on a transparent substrate 201. When a DC voltage of several volts is applied between the hole injection electrode 202 and the electron injection electrode 205, holes injected from the hole injection electrode 202 into the light emitting layer 204 through the hole transport layer 203 and electron injection The holes injected from the electrode 205 into the light-emitting layer 204 are recombined in the light-emitting layer 204 to emit light. In addition, the said layer structure is an example, Comprising: It is not limited to these, Conventionally a well-known layer structure can be used suitably as an organic EL element.

  As the hole injection electrode 202, an ITO (indium tin oxide) film which is a transparent conductive film is used. The ITO film is formed by sputtering, electron beam evaporation, ion plating or the like for the purpose of improving the transparency or reducing the resistivity. As the hole transport layer 203, a diamine derivative used by Tang et al., Such as N, N′-bis (3-methylphenyl) -N, N′-diphenylbenzidine (TPD), is used. These materials are generally excellent in transparency, and are almost transparent even with a film thickness of about 80 nm. The light-emitting layer 204 is generally configured to use an electron-transporting light-emitting material such as tris (8-quinolinolato) aluminum (Alq3) formed to a thickness of several tens of nm by vacuum deposition. For the purpose of realizing various emission colors, a so-called double hetero structure in which the light-emitting layer 204 is a relatively thin film and an electron transport layer is stacked by about 20 nm may be employed. Further, as the electron injection electrode 205, an alloy of a metal having a low work function and a low electron injection barrier, such as an MgAg alloy or an AlLi alloy, and a metal having a relatively large work function and a stable property is transmitted to a thickness of about 10 nm. Often used is a laminate in which a transparent electrode such as an ITO film is laminated. Note that the constituent materials of the hole injection electrode 202, the hole transport layer 203, the light emitting layer 204, and the electron injection electrode 205 are only examples, and are not limited thereto. A known material used for manufacturing the element can be appropriately used.

FIG. 4 shows an example of a basic structure of the inorganic EL element. In the inorganic EL element 210, a first transparent electrode 212a, a first insulating layer 213a, a light emitting layer 214, a second insulating layer 213b, and a second transparent electrode 212a are laminated in this order on a transparent substrate 211. Is formed. When an AC voltage of about 10 ⁶ V / cm is applied between the first transparent electrode 212a and the second transparent electrode 212b, electrons accelerated by a high electric field collide and excite the emission center of the phosphor in the light emitting layer 214. , Emit light when they relax. The insulating layers 213a and 213b have a function of limiting the current flowing through the light emitting layer 214, can suppress the dielectric breakdown of the inorganic EL element 210, and function to obtain stable light emission characteristics. In addition, the said layer structure is an example, Comprising: It is not limited to these, Conventionally a well-known layer structure can be used suitably as an inorganic EL element.

Examples of the dielectric used as the insulating layers 213a and 213b include Y ₂ O ₃ , Ta ₂ O ₅ , Al ₂ O ₃ , Si ₃ N ₄ , BaTiO ₃ and SrTiO _3. Be filmed. The inorganic phosphor used as the light emitting layer 214 is generally an insulating crystal as a base crystal and doped with an inorganic material serving as a light emission center. A preferred example is mainly composed of ZnS. , Mn, Cr, Tb, Eu, Tm, Yb and other transition metal elements and those doped with rare earth elements. The constituent materials of the insulating layers 213a, 213b, and the light emitting layer 214 are examples, and are not limited to these. Known materials that have been conventionally used for manufacturing inorganic EL elements capable of taking out double-sided light. Can be used as appropriate.

  Next, the liquid crystal light control sheet will be described. As the liquid crystal light control sheet 120, a liquid crystal light control sheet 120 having an arbitrary configuration in which a liquid crystal layer 122 is sandwiched between a pair of transparent substrates 121 a and 121 b can be used. The liquid crystal light control sheet 120 is provided with transparent electrodes 123a and 123b facing the inner surfaces of the transparent substrates 121a and 121b, and a spacer (not shown) is provided in the interior to arrange the transparent substrates 121a and 121b in parallel. And a liquid crystal material is injected between them and sealed with a sealing member 124. The liquid crystal layer 122 is transparent when no voltage is applied, and is a liquid crystal substance that becomes cloudy and non-transparent when a voltage is applied, or is transparent when a voltage is applied and becomes cloudy and non-transparent when no voltage is applied. A liquid crystal substance that is in a state is used. The transparent substrates 121a and 121b may be transparent resin sheets, and the transparent electrodes 123a and 123b may be transparent or semitransparent electrodes made of a conductive polymer. In this case, it becomes a flexible liquid crystal light control sheet, and further weight reduction can be realized.

  Next, the operation of the structure of the display device 100 will be described. When the user visually recognizes arbitrary information displayed on the EL panel 110 from the direction of arrow A, the user can recognize the light emission from the light emitting layer 112 via the transparent electrode 113a and the transparent substrate 111a. On the other hand, since the EL panel 110 can extract light from both sides, part of the external light incident from the direction of arrow B passes through the transparent substrate 111b, the transparent electrodes 113b and 113a, and the transparent substrate 111a to the user. Be recognized. As a result, the display visually recognized by the user has a reduced contrast. Therefore, by making the liquid crystal light control sheet 120 disposed adjacent to the EL panel 110 non-transparent, external light incident from the direction of the arrow B is shielded by the liquid crystal layer 122. Contrast does not decrease. In the liquid crystal light control sheet 120, the parallel light transmittance in a non-transparent state is 20% or less, and more preferably 10% or less, so that sufficiently good display quality can be realized. At the same time, even if an observer other than the user tries to visually recognize the display on the EL panel 110 from the direction of the arrow B, the liquid crystal light control sheet 120 is not visible because it is in a non-transparent state, and the confidentiality of information is ensured. . On the other hand, when the user visually recognizes arbitrary information displayed on the EL panel 110 from the direction of the arrow B, the liquid crystal light control sheet 120 is set in a transparent state so that light emission from the light emitting layer 112 is transmitted to the transparent electrode 113b and the transparent substrate 111b. Further, the user can recognize through the liquid crystal light control sheet 120. For example, the case where a conventional circularly polarizing plate is used will be described with reference to FIG. FIG. 9 is a cross-sectional view of a main part of a foldable portable terminal 400 provided with a circularly polarizing plate 413. The portable terminal 400 includes a substantially plate-like display unit housing 410 having a display unit 412 and a substantially plate-like operation unit housing 420 having switches and a transmitter as input keys for various operations. The display unit housing 410 and the operation unit housing 420 are foldable so as to overlap each other. The circularly polarizing plate 413 is provided adjacent to the display portion 412 and has a parallel light transmittance of about 50%. The transmitted light from the back surface of the display unit 412 is attenuated to 50% by the circularly polarizing plate 413, so that the display observed from the front of the display unit 412 can improve display quality to a certain degree. Since the display observed from the back side is similarly attenuated by the circularly polarizing plate 413, the luminance decreases. On the other hand, in the liquid crystal light control sheet 120, the parallel light transmittance in the transparent state is 60% or more, and more preferably 70% or more, so that the brightness is increased by about 50% compared to the conventional example. be able to.

  The above-described embodiment shows an example of the present invention, and the configuration of the present invention is not limited to these. Even if the liquid crystal light control sheets are arranged on both sides of the EL panel, it is possible to obtain the same effect as in the present embodiment.

(Embodiment 2)
An electronic apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. 5 and 6 to 8. FIG. 5 is a main part sectional view showing an example in which the configuration of the electronic apparatus using the display device according to Embodiment 1 of the present invention as a display unit is applied to a foldable portable terminal. 6 is a perspective view seen from the side indicated by the arrow C when the portable terminal is opened, and FIG. 7 is shown by the arrow D when the portable terminal is opened as in FIG. FIG. Furthermore, FIG. 8 is a perspective view of the portable terminal in a folded state. This mobile terminal 300 is a substantially plate-like display unit housing 310 having display units 311a, 311b and a receiver unit 314, a switch 321 as an input key for various operations, and a transmitter unit 322. The operation unit housing 320 is connected to each other by a hinge unit 330 so as to be openable and closable, and the display unit housing 310 and the operation unit housing 320 can be folded so as to overlap each other. When the display unit housing 310 and the operation unit housing 320 are folded, the surface of the display unit 311 a is covered with the operation unit housing 320. In this case, the operation unit housing 320 functions as a lid.

  The display unit housing 310 is formed in a frame shape with a central portion cut out, and the display device according to the first embodiment is incorporated and fixed therein. Therefore, as shown in FIG. 6, the information displayed on the display unit 311a can be visually recognized from the direction of the arrow C, and the information displayed on the display unit 311b is displayed as the arrow D as shown in FIG. It becomes visible even from the direction of. Although not shown, the portable terminal 300 includes a control circuit that displays the information displayed on the display unit 311 in a normal rotation display or a reverse display, and a switching that switches between a transparent state and a non-transparent state of the liquid crystal light control sheet 313. Means and detecting means for detecting the open / closed state of the mobile terminal 300. The control circuit of the display unit 311 displays information displayed on the display unit 311 according to the direction (C direction or D direction) in which the user visually recognizes the display unit 311 when the portable terminal is folded or opened. Display in normal or reverse display. Further, the switching unit of the liquid crystal light control sheet 313 is configured to adjust the liquid crystal light control depending on the direction (arrow C direction or arrow D direction) in which the user visually recognizes the display unit 311 when the portable terminal is folded or opened. The sheet 313 is set to a transparent state or a non-transparent state. Further, the display device is fixed to the display unit housing 310 such that the liquid crystal light control sheet 313 is disposed on the outer surface when the portable terminal 300 is folded and the EL panel 312 is disposed on the inner surface. ing. In addition, the other structure of this portable terminal 300 is the same as that of the conventional general foldable portable terminal.

  Next, the operation of this embodiment will be described below. When the user visually recognizes information displayed on the display unit 311 from the C direction with the portable terminal 300 opened, the liquid crystal light control sheet 313 is in a non-transparent state. Accordingly, since external light incident on the display unit 311b from the D direction is shielded in front of the EL panel 312, the display visually recognized by the user can realize good display quality without lowering the contrast. Furthermore, even if a person other than the user tries to visually recognize the information displayed on the display unit 311 from the D direction, the liquid crystal light control sheet 313 is not transparent and cannot be visually recognized, and the confidentiality of the information is ensured. The On the other hand, as shown in FIG. 8, when the portable terminal 300 is closed, the liquid crystal light control sheet 313 is set in a transparent state so that information (light emission) displayed on the EL panel 312 is transparent liquid crystal light control. It can be seen by the user from the D direction through the sheet 313. In this case, since the display unit housing 310 and the operation unit 320 are folded so as to overlap each other, the influence of external light from the C direction on the display quality can be ignored.

  The above-described embodiment shows an example of the configuration of the present invention, and the configuration of the present invention is not limited to these. Even if the liquid crystal light control sheet is arranged so as to be inside when the portable terminal is folded, even if the liquid crystal light control sheet is arranged on both sides of the EL panel, the same effect as in the present embodiment can be obtained.

  The display device and the electronic device according to the present invention are useful as a display device and an electronic device using an EL panel capable of taking out double-sided light, particularly as a mobile terminal such as a mobile phone.

It is sectional drawing perpendicular | vertical to the light emission surface of the display apparatus which concerns on Embodiment 1 of this invention. 1 is a schematic plan view of a display device according to Embodiment 1 of the present invention. It is sectional drawing perpendicular | vertical to the light emission surface of an organic EL element. It is sectional drawing perpendicular | vertical to the light emission surface of an inorganic EL element. It is principal part sectional drawing perpendicular | vertical to the light emission surface of the electronic device which concerns on Embodiment 2 of this invention. It is a perspective view which shows the display surface seen from the C direction of FIG. It is a perspective view which shows the display surface seen from the D direction of FIG. It is a perspective view which shows the state which folded the electronic device of FIG. It is principal part sectional drawing perpendicular | vertical to the light emission surface of the conventional foldable mobile communication terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Display apparatus, 110 EL panel, 111a, 111b Transparent substrate, 112 Light emitting layer, 113a, 113b Transparent electrode, 120 Liquid crystal light control sheet, 121a, 121b Transparent substrate, 122 Liquid crystal layer, 123a, 123b Transparent electrode, 124 Sealing material , 130 adhesive region, 200 organic EL element, 201 transparent substrate, 202 hole injection electrode, 203 hole transport layer, 204 light emitting layer, 205 electron injection electrode, 210 inorganic EL element, 211 transparent substrate, 212a, 212b transparent electrode, 213a, 213b Insulating layer, 214 Light emitting layer, 300 Electronic device, 310 Display housing, 311a, 311b Display, 312 EL panel, 313 Liquid crystal light control sheet, 314 Receiver, 320 Operation housing, 321 switch, 322 Transmitter, 330 Hinge, 400 Electronic equipment, 412 EL , 413 circularly polarizing plate, 420 operation part housing, 430 hinge part

Claims (7)

An electroluminescence display unit capable of double-sided display having a pair of transparent electrodes and a light emitting layer sandwiched between the pair of transparent electrodes;
A display device comprising: a liquid crystal light control sheet disposed adjacent to at least one surface of the display unit and capable of switching between a transparent state and a non-transparent state.   The display device according to claim 1, wherein the display unit includes an organic electroluminescence element.   The display device according to claim 1, wherein the display unit includes an inorganic electroluminescent element. The liquid crystal light control sheet is
A pair of transparent electrodes;
The display device according to claim 1, further comprising: a liquid crystal layer sandwiched between the pair of transparent electrodes.   The voltage applied between the pair of transparent electrodes of the liquid crystal light control sheet is controlled to change the transparent / non-transparent state of the liquid crystal layer, thereby changing the transparent / non-transparent state of the liquid crystal light control sheet. The display device according to claim 4, wherein the display device is switched. The display device according to any one of claims 1 to 5,
A housing to which the display device is attached so that both sides of the display device are visible;
Control means for controlling an operation of inverting information displayed on the display device;
Switching means for switching the transparent state / non-transparent state of the liquid crystal light control sheet;
An electronic device comprising: A lid that covers one of both surfaces of the display device;
A detection unit that detects that the one surface of the display device is covered with the lid,
The control means reverses the information displayed on the display device when the one surface of the display device is covered with the lid.
The said switching means switches the transparent state / non-transparent state of the said liquid-crystal light control sheet, when the said one surface of the said display apparatus is covered with the said cover body. Electronics.

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