JP2006308897A - Organic el display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately perform image display by an organic EL display panel and to make the organic EL display panel appropriately function as a mirror. <P>SOLUTION: The organic EL display device includes the organic EL display panel 2, a polarizing plate 4 arranged on a front surface side of the organic EL display panel 2, and a liquid crystal panel 3 arranged between the polarizing plate 4 and the organic EL display panel 2, in which the image display is performed by controlling each lighting of the organic EL light emitting elements disposed in a plurality in a display region of the organic EL display panel 2. At the time of a non-display mode when the image display by the organic EL display panel 2 is not performed, the display region of the organic EL display panel 2 is functioned as the mirror by switching the driving voltage applied to the liquid crystal panel 3 to the state of on or off. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic EL display device that displays an image on an organic EL display panel.

  With the recent rapid technological development in the information communication field, there is a great expectation for a flat panel display to replace CRT (Cathode-Ray Tube). In particular, organic EL (Electro Luminescence) displays are actively studied because they are excellent in terms of high-speed response, visibility, brightness, and the like.

The original organic EL device has a two-layer laminated structure of organic thin films, uses trisaluminum for the light emitting layer, emits green light when driven at a low voltage of 10 V or less, and has a luminance of 1000 cd / m ² . I was getting. In recent research, various organic EL devices have been developed in which about 1 to 10 organic layers sandwiched between a hole injection electrode (anode) and an electron injection electrode (cathode) are stacked. With respect to organic EL materials, those using low molecules and those using polymers have been studied. As a method for producing an organic EL element, an organic EL element is formed by a method of forming a thin film of a low molecular compound by a vacuum deposition method or the like, or a method of forming a thin film of a polymer compound by a spin coating method, ink jet, die coating, flexographic printing or the like. Has been proposed.

  The organic EL element emits light by current driving. As a driving method of this organic EL element, there are an active driving system using a switching element for selecting an organic EL element constituting a pixel and a passive driving system not using a switching element. As the organic EL display, there are known ones that perform display by monochromatic light emission, areas that perform partial color display, and those that perform full color display. As the monochromatic organic EL display, for example, one that emits red, blue, green, or white monochromatic light is known.

  By the way, the organic EL element is formed of a light-reflective metal film such as Al among the anode and cathode sandwiching the organic thin film layer, and the anode is formed of a transparent conductive film such as ITO (Indium-Tin Oxide). Has been. For this reason, in the organic EL display device, external light is specularly reflected by the metal film constituting the organic EL element, which causes a problem that the contrast of the image is lowered. In order to suppress a decrease in contrast due to reflection of external light, a circularly polarizing plate is usually disposed on the front side of the organic EL display panel. The circularly polarizing plate is a combination of the functions of a linearly polarizing plate and a quarter-wave plate, and has a function of blocking light incident from the outside and reflected by the organic EL element.

  On the other hand, the present applicant has proposed in Japanese Patent Application No. 2004-147142 to use the mirror reflection of the organic EL device as a mirror. Specifically, it has been proposed to divide a light emitting region by an organic EL element into a mirror surface region that functions as a mirror and an illumination region that emits illumination light. However, even in the case of this application, if a circularly polarizing plate that prevents external light reflection when an image is displayed is not used, there is a risk of causing a decrease in contrast.

Moreover, as a well-known document relevant to this invention, there exists the following patent document 1, for example. In this patent document 1, a backlight type image display device that functions as a mirror in addition to image display is proposed. However, since the backlight type image display apparatus includes the half mirror member, there is a problem that the luminance of the display image is lowered.
Japanese Patent Laid-Open No. 11-15392

  The present invention has been proposed in view of such a conventional situation, and it is possible to appropriately display an image on an organic EL display panel and to appropriately function the organic EL display panel as a mirror. An object of the present invention is to provide an organic EL display device.

In order to achieve this object, the invention according to claim 1 of the present invention includes an organic EL display panel, a polarizing plate disposed on the front side of the organic EL display panel, and between the polarizing plate and the organic EL display panel. In addition to controlling the lighting of a plurality of organic EL light emitting elements provided in the display area of the organic EL display panel, image display is performed and image display is performed by the organic EL display panel. In the non-display mode, the organic EL display device is characterized in that the display area of the organic EL display panel functions as a mirror by switching the drive voltage applied to the liquid crystal panel to an on or off state.
The invention according to claim 2 of the present invention is the organic EL display device according to claim 1, further comprising a retardation plate between the polarizing plate and the liquid crystal panel.
According to the third aspect of the present invention, by switching the driving voltage applied to a partial area of the liquid crystal panel to an on or off state, a part corresponding to the partial area of the display area is caused to function as a mirror. An organic EL display device according to claim 1 or 2.

As described above, in the organic EL display device according to the present invention, the driving voltage applied to the liquid crystal panel is switched to the on or off state, so that it is incident from the front side of the polarizing plate and reflected on the organic EL display panel side. It is possible to convert from a state where the light to be blocked is blocked by the polarizing plate to a state where it is transmitted through the polarizing plate, or from a state where it is transmitted through the polarizing plate to a state where it is blocked by the polarizing plate.
Therefore, in the display mode for displaying an image on the organic EL display panel, the driving state of the liquid crystal panel is set so that light incident from the front side of the polarizing plate and reflected on the organic EL display panel side is blocked by the polarizing plate. By switching, it is possible to perform high-contrast image display that prevents external light reflection.
On the other hand, in the non-display mode in which image display by the organic EL display panel is not performed, the driving state of the liquid crystal panel so that light incident from the front side of the polarizing plate and reflected on the organic EL display panel side is transmitted through the polarizing plate. By switching, the display area of the organic EL display panel can be appropriately functioned as a mirror.
In this non-display mode, the organic EL display is switched by switching the driving state of the liquid crystal panel so that light incident from the front side of the polarizing plate and reflected on the organic EL display panel side is blocked by the polarizing plate. The display area of the panel can be displayed in black.

  Hereinafter, an organic EL display device to which the present invention is applied will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

  As shown in FIG. 1, an organic EL display device 1 to which the present invention is applied includes an organic EL display panel 2, a liquid crystal panel 3 disposed on the front side of the organic EL display panel 2, and a front surface of the liquid crystal panel 3. And a polarizing plate 4 disposed on the side.

  The organic EL display panel 2 includes an element substrate 5 provided with a plurality of organic EL light emitting elements, and a sealing substrate 6 disposed opposite to the element substrate 5, and the peripheral portions of the substrates 5 and 6 are sealed. It has a structure sealed with a material 7.

  The element substrate 5 includes, for example, an anode 9 made of a transparent conductive film such as ITO, a thin organic EL layer 10 including an organic light emitting layer, and a cathode 11 formed of a metal conductive film such as Al on a glass substrate 8. An organic EL light-emitting element that is sequentially stacked is formed. This organic EL light emitting element emits light when current is supplied to the organic EL layer 10 disposed between the anode 9 and the cathode 11.

  The organic EL display panel 2 employs, for example, a passive matrix driving method. For this reason, a plurality of anodes 9 and cathodes 11 are arranged in stripes at predetermined intervals, and have a structure in which they are arranged orthogonal to each other with the organic EL layer 10 interposed therebetween. In addition, an organic EL light emitting element (pixel) is formed at each position where the electrodes 9 and 11 intersect, and a plurality of these organic EL light emitting elements are arranged in a matrix, thereby displaying an image. Is configured. The element substrate 5 is provided with a drive driver 12 for controlling a drive voltage applied between the electrodes 9 and 11.

  The organic EL display panel 2 is not limited to the above-described passive matrix driving method, but may be an active matrix driving method (for example, a TFT method). In this case, lighting of each organic EL light emitting element is controlled by providing an active element such as a TFT (Thin Film Transistor) for each organic EL light emitting element.

  The sealing substrate 6 is made of, for example, a metal material such as stainless steel, aluminum, or an alloy thereof, glass, acrylic resin, or the like. The sealing substrate 6 covers the organic EL light-emitting element on the element substrate 5 and has a peripheral space bonded to the glass substrate 8 by the sealing material 7 to form a sealed space that prevents entry of moisture from the outside. Forming. Furthermore, a water catching material 13 for collecting moisture that causes deterioration of the organic EL light emitting element is provided on the inner surface of the sealing substrate.

  The liquid crystal panel 3 includes a back side substrate 14 and a front side substrate 15 that are disposed to face each other, and a liquid crystal layer 16 that is sandwiched between the back side substrate 14 and the front side substrate 15. The back side substrate 14 and the front side substrate 15 are made of transparent glass or the like. Further, between the back side substrate 14 and the front side substrate 15, the opposing distance is uniformly maintained by the spacers 17 dispersed in the liquid crystal layer 16, and the peripheral portions are sealed by the sealing material 18. Has been.

  Transparent electrodes 19 and 20 are provided on the mutually opposing surfaces (inner surfaces) of the back side substrate 14 and the front side substrate 15, respectively. These transparent electrodes 19 and 20 are made of a transparent conductive material such as ITO. Although not shown, alignment films are provided on the inner surfaces of the rear substrate 14 and the front substrate 15 to cover the transparent electrodes 19 and 20, respectively. These alignment films control the alignment of the liquid crystal layer 16. For example, when a TN (Twisted Nematic) system is adopted, the alignment film has an alignment state in which the liquid crystal molecules of the liquid crystal layer 16 are twisted by about 90 °. Become. Further, when an STN (Super Twisted Nematic) system is adopted, the alignment film causes the liquid crystal molecules of the liquid crystal layer 16 to be in an alignment state twisted by about 180 ° to 270 °.

  The liquid crystal layer 16 is made of nematic liquid crystal containing an optical rotatory material. The alignment state of the liquid crystal layer 16 changes in response to an electric field due to the dielectric anisotropy of the liquid crystal molecules. Therefore, the polarization state of the light passing through the liquid crystal panel 3 can be changed by switching the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3 to an on or off state.

  The liquid crystal panel 3 employs, for example, a segment drive system, and the transparent electrodes 19 and 20 are solid electrodes on the inner surfaces of the back side substrate 14 and the front side substrate 15, respectively, in the display area of the organic EL display panel 2. It is formed over the corresponding region. The back side substrate 14 is provided with a drive driver 21 for controlling a drive voltage applied between the electrodes 19 and 20.

  The liquid crystal panel 3 is not limited to the one using the segment driving method described above, but may be one using a full dot driving method such as a passive matrix driving method or an active matrix driving method. For example, when the passive matrix driving method is adopted, the transparent electrodes 19 and 20 are arranged in a plurality of stripes at predetermined intervals, and are orthogonal to each other between the back side substrate 14 and the front side substrate 15. Structure. In this case, dots are formed at each position where the transparent electrodes 19 and 20 intersect, and a plurality of these dots are arranged in a matrix. On the other hand, when an active matrix driving method (for example, TFT method) is adopted, one of the transparent electrodes 19 and 20 described above is a solid electrode formed over the entire surface of the substrate, and the other corresponds to each dot. The pixel electrodes are arranged in a matrix. Further, each dot is provided with an active element such as a TFT (Thin Film Transistor).

  The polarizing plate 4 is for preventing reflection of the external light L by the cathode 11 of the organic EL light emitting element in the display mode for displaying an image on the organic EL display panel 2. Specifically, the polarizing plate 4 includes a linear polarizing plate that transmits only linear polarized light in a specific direction, a circular polarizing plate in which the functions of the linear polarizing plate and a quarter wavelength plate (retardation plate) are combined, or It consists of an elliptically polarizing plate and is affixed to the front surface (outer surface) of the front-side substrate 15 constituting the liquid crystal panel 3.

  In the organic EL display device 1 having the above-described structure, image display is performed by controlling the lighting of each organic EL light emitting element provided in the display area of the organic EL display panel 2 by the drive driver 12. Specifically, in the organic EL display device 1, in the display mode for displaying an image on the organic EL display panel 2, as shown in FIG. 2A, the drive voltage is applied between the electrodes 9 and 11 of the selected organic EL light emitting element. Is applied, and an electric current is supplied to the organic EL layer 10 sandwiched between the electrodes 9 and 11 to display an image by light OL from the organic EL light emitting element that emits light.

  In this display mode, the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3 is turned off. At this time, the liquid crystal panel 3 is blocked by the polarizing plate 4 while modulating the external light L that is incident from the front side of the polarizing plate 4 and reflected by the organic EL display panel 2 side while passing through the liquid crystal layer 16. The light is converted into light having a polarization state. Therefore, in the organic EL display device 1, in the display mode, the liquid crystal panel 3 is turned off to display an image with a high contrast that prevents reflection of external light.

  On the other hand, in the non-display mode in which image display by the organic EL display panel 2 is not performed, the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3 is turned on as shown in FIG. 2B. At this time, the liquid crystal panel 3 modulates the external light L incident from the front side of the polarizing plate 4 and reflected on the organic EL display panel 2 side while passing through the liquid crystal layer 16, while the polarizing plate 4 described above. The light in the polarization state blocked by the light is converted into the light in the polarization state transmitted through the polarizing plate 4. Therefore, in the organic EL display device 1, when the liquid crystal panel 3 is turned on in the non-display mode, the display area of the organic EL display panel 2 can function as a mirror (hereinafter referred to as mirror mode). That said.)

  In the non-display mode, as shown in FIG. 2C, the liquid crystal panel 3 is turned off so that the light is incident from the front side of the polarizing plate 4 and reflected on the organic EL display panel 2 side. Since the light L is blocked by the polarizing plate 4, the display area of the organic EL display panel 2 can be set to black display (hereinafter referred to as black mode).

  As described above, in the organic EL display device 1, the driving voltage applied to the liquid crystal panel 3 is switched to the on or off state, so that the light is incident from the front side of the polarizing plate 4 on the organic EL display panel 2 side. The reflected external light L can be converted from a state where it is blocked by the polarizing plate 4 to a state where it is transmitted through the polarizing plate 4, or from a state where it is transmitted through the polarizing plate 4 to a state where it is blocked by the polarizing plate 4. Therefore, in this organic EL display device 1, image display by the organic EL display panel 2 can be performed appropriately, and the organic EL display panel 2 can function properly as a mirror.

  In the organic EL display device 1, when the driving of the liquid crystal panel 3 is turned on, the light L that is incident from the front side of the polarizing plate 4 and is reflected on the organic EL display panel 2 side is the polarizing plate 4. The polarizing plate 4 (specifically, the polarization direction of a linearly polarizing plate, a circularly polarizing plate, or an elliptically polarizing plate) and the liquid crystal panel 3 ( Specifically, the alignment direction of the liquid crystal layer 16 is set.

  On the other hand, in the organic EL display device 1, when the driving of the liquid crystal panel 3 is turned off, the light L incident from the front side of the polarizing plate 4 and reflected on the organic EL display panel 2 side is reflected on the polarizing plate 4. It is also possible to set the polarizing plate 4 and the liquid crystal panel 3 so as to switch from a state blocked by the state to a state where the polarizing plate 4 is transmitted.

  In this case, in the display mode, as shown in FIG. 3A, the liquid crystal panel 3 is switched to the front side of the polarizing plate 4 by turning on the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3. The external light L that is incident on the organic EL display panel 2 and is reflected on the organic EL display panel 2 side is converted into light in a polarization state blocked by the polarizing plate 4 while being modulated while passing through the liquid crystal layer 16. Therefore, in this display mode, by turning off the driving of the liquid crystal panel 3, it is possible to display an image with high contrast while preventing external light reflection.

  On the other hand, in the non-display mode, as shown in FIG. 3B, the liquid crystal panel 3 is viewed from the front side of the polarizing plate 4 by turning off the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3. The external light L that is incident and reflected on the organic EL display panel 2 side is modulated while passing through the liquid crystal layer 16, and is transmitted through the polarizing plate 4 from the polarized light blocked by the polarizing plate 4 described above. Convert to polarized light. Therefore, in the non-display mode, the mirror mode can be set by turning off the driving of the liquid crystal panel 3.

  Further, in the non-display mode, as shown in FIG. 3C, the black mode can be set by turning on the liquid crystal panel 3.

  In addition, although the said setting can also be performed by the combination of the polarizing plate 4 and the liquid crystal panel 3 mentioned above, it can also be performed by arrange | positioning a phase difference plate between these polarizing plates 4 and the liquid crystal panel 3. FIG. .

  Further, the organic EL display device 1 has a configuration in which the entire display area is switched to the display mode, the mirror mode, and the black mode, but is not necessarily limited to such a configuration. For example, as shown in FIG. 4, the display area S can be divided into two partial areas S1 and S2, and the display mode, mirror mode, and black mode can be switched for each of the partial areas S1 and S2.

In this case, the liquid crystal panel 3 has a configuration in which the transparent electrodes 19 and 20 formed on the inner surfaces of the back side substrate 14 and the front side substrate 15 are divided corresponding to the partial regions S1 and S2. Among these, by patterning the electrodes 19 and 20 corresponding to the partial region S1 into a predetermined shape, the partial region S1 is used as a segment display region for displaying segments such as characters, graphics, and symbols. On the other hand, the electrodes 19 and 20 corresponding to the partial region S2 of the liquid crystal panel 3 are solid electrodes.
In this case, as shown in FIG. 4A, in the partial area S1, by controlling the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3 corresponding to the partial area S1, segment display such as time display is performed. It can be performed. On the other hand, in the partial region S2, the driving voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3 corresponding to the partial region S2 is switched to the on or off state, thereby switching between the display mode, the mirror mode, and the black mode. Can be switched. Furthermore, in the display area S, as shown in FIG. 4B, the entire surface of the display area S can be set to the display mode by the organic EL display panel 2 by turning off the liquid crystal panel 3.

Further, in the organic EL display device 1, for example, as shown in FIG. 5, the display area S is divided into three partial areas S1, S2, and S3, and the display mode and the mirror mode are divided into the partial areas S1, S2, and S3. It is also possible to switch to the black mode.
In this case, the liquid crystal panel 3 is configured to adopt the above-described full dot driving method, and displays any one or more of the partial areas S1, S2, S3, for example, for an arbitrary image. A full dot display area can be obtained.
Further, in these partial regions S1, S2, and S3, as shown in FIGS. 4A, 4B, and 4C, the drive voltage applied between the electrodes 19 and 20 of the liquid crystal panel 3 corresponding to each region is turned on or off. By switching, it is possible to individually switch to the above-described display mode, mirror mode, and black mode.

  In the organic EL display device 1, the element substrate 5 of the organic EL display panel 2 and the back side substrate 14 of the liquid crystal panel 3 may be integrated. And when it is set as such a structure, the whole apparatus can be further reduced in thickness.

FIG. 1 is a cross-sectional view showing a configuration of an organic EL display device to which the present invention is applied. FIG. 2 is a diagram for explaining operation switching in the organic EL display device shown in FIG. FIG. 3 is a diagram for explaining another operation switching in the organic EL display device shown in FIG. 1. FIG. 4 is a diagram for explaining a state in which the display area is divided into two partial areas and the operation is switched. A shows a state in which the two partial areas are operated in different modes, and B shows It is a top view which shows the state which operate | moved two partial area | regions in the same mode. FIG. 5 is a diagram for explaining a state in which the display area is divided into three partial areas and the operation is switched. A is a state in which the three partial areas are operated in different modes, and B is A state where three partial regions are operated in the same mode is shown, and C is a plan view showing a state where two partial regions are operated in the same mode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic EL display device, 2 ... Organic EL display panel, 3 ... Liquid crystal panel, 4 ... Polarizing plate, 5 ... Element substrate, 6 ... Sealing substrate, 7 ... Sealing material, 8 ... Glass substrate, 9 ... Anode, 10 DESCRIPTION OF SYMBOLS ... Organic EL layer, 11 ... Cathode, 12 ... Drive driver, 13 ... Water catching material, 14 ... Back side substrate, 15 ... Front side substrate, 16 ... Liquid crystal layer, 17 ... Spacer, 18 ... Sealing material, 19, 20 ... Transparent electrode, 21 ... Drive driver

Claims (3)

An organic EL display panel;
A polarizing plate disposed on the front side of the organic EL display panel;
A liquid crystal panel disposed between the polarizing plate and the organic EL display panel;
Image display is performed by controlling each lighting of a plurality of organic EL light emitting elements provided in the display area of the organic EL display panel, and in the non-display mode in which image display by the organic EL display panel is not performed, An organic EL display device that causes a display region of the organic EL display panel to function as a mirror by switching a driving voltage applied to the liquid crystal panel to an on or off state.   The organic EL display device according to claim 1, further comprising a retardation plate between the polarizing plate and the liquid crystal panel.   2. The part corresponding to the partial area of the display area is caused to function as the mirror by switching a driving voltage applied to the partial area of the liquid crystal panel to an on or off state. Or the organic electroluminescence display of 2.

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