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    • 专利摘要:
    The invention relates to a display unit for a portable object, said display unit (1) comprising a first at least partially transparent emitting display device (2) located on the side of an observer, a second device for reflective display (6) being arranged under the first emissive display device (2), said second reflective display device (6) being able to switch between a transparent state in which it displays no information and a reflective state when it is activated.
    公开号:CH710225A2
    申请号:CH01545/14
    申请日:2014-10-10
    公开日:2016-04-15
    发明作者:Sagardoyburu Michel
    申请人:Swatch Group Res & Dev Ltd；
    IPC主号:
    专利说明:

    Field of the invention
    The present invention relates to a display assembly comprising two superimposed display devices. More specifically, the present invention relates to such a display assembly intended to be housed in a portable object such as a wristwatch.
    Technological background of the invention
    The readability of the information displayed by the display devices such as LCD display cells or display devices with organic electroluminescent diodes is very dependent on ambient light conditions. With some display devices, the information displayed can be read in good conditions in a bright environment, but are difficult to read in a dark environment. Conversely, other categories of display devices provide a good quality display in dim light or dark, but are difficult to read in daylight.
    By way of example, consider the liquid crystal display cells of transflective type, that is to say liquid crystal display cells capable of displaying information that will be visible by day thanks to to the exploitation of the phenomenon of reflection of ambient light, and which will also be visible in the dark by transmission using a backlighting device. Such transflective type liquid crystal display cells are optimized to be able to best reflect the sunlight and thus ensure good readability of the information displayed under conditions of high ambient light. However, so that such transflective liquid crystal display cells can best reflect sunlight, their transmission efficiency is greatly limited. Thus, when the backlighting device is activated in order to read the information displayed in the penumbra, a major part of the light emitted by the backlighting device is lost in absorption phenomena. The energy efficiency in this situation is therefore bad. In addition, the optical qualities of the information displayed by the liquid crystal cell are strongly dependent on the angle of view.
    With regard to the emissive-type display devices such as organic electroluminescent diode display devices, they have optical qualities that are superior to those of liquid crystal display cells, these optical qualities such as that the luminance and the color do not depend in particular on the angle of view. Nevertheless, these high quality emissive type display devices do not allow operation in reflective mode. The information they display is therefore very readable in the dark or dark, but become difficult to read as soon as they are observed outdoors. To remedy this problem, it is possible to increase the amount of current supplied to the emissive display devices to ensure a minimum of readability. However, even under normal use conditions, these emissive display devices consume more than a reflective type liquid crystal cell. Their power consumption is such that it is difficult to imagine keeping them on permanently, especially when they are embedded in a portable object of small dimensions such as a wristwatch whose only source of energy is a battery which is usually expected to last at least a year.
    Summary of the invention
    The present invention aims to remedy the aforementioned problems as well as others by providing a display assembly for a portable object such as a wristwatch whose operation is suitable both in an environment strongly lit only in a dark environment.
    For this purpose, the present invention relates to a display assembly for a portable object, this display assembly comprising a first at least partially transparent emitting display device located on the side of an observer, a second device reflective display being disposed under the first emissive display device, said second reflective display device being capable of switching between a transparent state when at rest and a reflective state when activated.
    According to an additional characteristic of the invention, the transparent emissive display device is fixed on the reflective display device.
    According to another characteristic of the invention, the transparent emissive display device is glued to the reflective display device by means of a film adhesive or a layer of liquid glue.
    With these features, the present invention provides a display assembly for a portable object such as a wristwatch whose operation is optimal regardless of ambient lighting conditions. In broad daylight, the information will preferably be displayed by the reflective display device. Indeed, this reflective display device, taking advantage of a reflection phenomenon of sunlight to display information, is energy efficient. It can therefore remain permanently lit and offers good readability of the information. Conversely, in dim light or darkness, the information will be displayed by the emissive display device. Such an emissive display device consumes more current than a reflective display device, but the information it displays is visible at night or in the dark with very good optical properties which are in particular independent of the angle of view. Thus, unlike a transflective liquid crystal display cell which seeks to achieve a compromise between the reflectivity of its reflective mode, and the electrical energy consumption of its transmissive backlight device, the display assembly according to the invention proposes to combine two display devices, one purely reflective and the other purely emissive, without compromising the performance of either of these two devices. display.
    According to a first embodiment of the invention, the first display device comprises a transparent emissive display cell with organic electroluminescent diodes, and the second display device comprises a reflective liquid crystal display cell. of nematic helical or super-nematic type helical or even vertical alignment.
    According to a complementary feature of the invention, the electroluminescent organic diode display cell is disposed between a circular polarizer and a quarter wave plate, the circular polarizer being placed on the side of the observer.
    Addressing the electroluminescent zones of electroluminescent organic diode display cells is provided by transparent electrodes most often made using a metallic material or a metal oxide. These electrodes therefore often cause slight optical reflection phenomena that induce a degradation of the contrast, which affects the readability of the information displayed by the display cells with organic electroluminescent diodes. To overcome this drawback, the present invention teaches arranging the electroluminescent organic diode display cell between a circular polarizer and a quarter wave plate, the circular polarizer being placed on the observer side. Thus, one of the polarization components of the ambient light that enters the display assembly according to the invention is absorbed by the circular polarizer, while the other polarization component of the light is circularly polarized. When passing through the organic electroluminescent diode display cell, the circularly polarized ambient light is partially reflected by the transparent electrodes of the organic electroluminescent diode display cell, this reflected light is phase shifted, which has the effect of transforming its circular polarization into circular polarization of opposite direction of rotation. Thus, when the reflected light crosses again the circular polarizer, it is absorbed by the latter. In this way, it is possible to eliminate the stray light reflected on the electrodes of the organic electroluminescent diode display cell, and to retain only light passing through the electroluminescent organic diode display cell without modification. . As a result, the light is again linearly polarized after passing through the quarter-wave plate placed beneath the organic electroluminescent diode display cell and will eventually be absorbed or reflected by the reflective liquid crystal display cell according to that one looks for a display with positive or negative contrast.
    According to a second embodiment of the invention, the first display device comprises a transparent emissive display cell with organic electroluminescent diodes, and the second display device comprises a reflective display cell devoid of polarizers. . The reflective display cell may be an electrophoretic display cell, a dichroic liquid crystal display cell, or a cholesteric liquid crystal display cell.
    The advantage of such an embodiment lies in the fact that we use the inherently reflective character for example of an electrophoretic display cell to obtain a display assembly according to the invention. whose operation is suitable both in a highly illuminated environment and in a dark environment. In this way, reflective and absorbent films can be dispensed with, thereby saving in terms of components and assembly time. In addition, the resulting display assembly is thinner, which is very advantageous especially in the case where it is desired to integrate such a display assembly for example in a wristwatch in which the available space is necessarily limited.
    Brief description of the figures
    Other features and advantages of the present invention will emerge more clearly from the detailed description which follows of an embodiment of the display assembly according to the invention, this example being given purely by way of illustration and not by way of example. limiting only in connection with the appended drawing in which:<tb> Fig. 1 <SEP> is a schematic sectional view illustrating a display assembly according to the invention comprising a first at least partially transparent emitting display device located on the side of an observer, a second reflective display device being disposed under the first emissive display device;<tb> fig. 2 <SEP> is a sectional view of an exemplary embodiment of a display assembly according to the invention in which the first display device is a transparent emissive display cell with organic electroluminescent diodes, and the second display device is a reflective liquid crystal display cell of helical nematic type;<tb> figs. 3A to 3D <SEP> schematically illustrate the operating mode of the display assembly illustrated in FIG. 2 according to whether the electroluminescent organic diode display cell and the helical nematic liquid crystal display cell are active or passive;<tb> fig. 4 <SEP> is a view similar to that of FIG. Wherein the second display device is a vertically aligned reflective liquid crystal display cell;<tb> figs. 5A to 5D <SEP> schematically illustrate the operating mode of the display assembly illustrated in FIG. 4 depending on whether the organic light emitting diode display cell and the vertically aligned liquid crystal display cell are active or passive;<tb> fig. 6 <SEP> is a detailed sectional view of an alternative embodiment of the display assembly according to the invention illustrated in FIG. 4 in which is placed above the light-emitting organic diode transparent display cell a circular polarizer which consists of an absorbing polarizer and a quarter-wave plate;<tb> fig. FIG. 7 is a schematic sectional view illustrating a display assembly according to the invention comprising a transparent emissive display cell with organic electroluminescent diodes, and the second display device is a reflective liquid crystal display cell. the organic electroluminescent diode display cell being disposed between a circular polarizer and a quarter wave plate, the circular polarizer being placed on the observer side;<tb> fig. <SEP> is a schematic sectional view illustrating a display assembly according to the invention comprising an OLED transparent display cell disposed above an electrophoretic reflective display cell, and<tb> fig. <SEP> is a schematic view illustrating a display assembly according to the invention comprising in which the reflective display cell is an electrophoretic display cell glued under the light emitting organic electroluminescent diode display cell by means of an adhesive layer.
    Detailed description of an embodiment of the invention
    The present invention proceeds from the general inventive idea of providing a display assembly that is able to legibly display information both in broad daylight and in dim light or darkness and whose electrical energy consumption is optimal. To achieve this objective, the present invention teaches combining an emissive type display device with a display device which is arranged to be able to switch between a state of rest in which it is transparent and an active state in which it is capable of to reflect the ambient light. The emissive type display device is typically an organic electroluminescent diode display cell, while the reflective type display device is typically a liquid crystal display cell. For displaying information in broad daylight, the use of the reflective type of display device which, by reflection of sunlight, makes it possible to display the information in a clear and readable manner while consuming few electric energy. For the display of information in dim light or darkness, the use of the emissive display device is preferred. Thanks to its excellent optical properties, especially in terms of contrast and color reproduction, such an emissive display device makes it possible to display a large amount of information in a very readable manner. In particular, the readability of the information displayed is not dependent on the angle of view. In addition, despite the penumbra or darkness, it is possible to significantly reduce the power consumption of such an emissive display device while ensuring good readability of the information displayed. There is thus a display assembly that includes a reflective display device placed at the base of the stack and which is capable of displaying information continuously while consuming very little energy, and a device for emissive display placed on the top of the stack and which is able to display information on demand in a very readable way in dim light or darkness.
    FIG. 1 is a schematic sectional view of a display assembly according to the invention. Designated as a whole by the general numerical reference 1, this display assembly comprises a first at least partially transparent emitting display device 2 arranged on the side of an observer 4, and a second reflective display device 6 also at the less partially transparent disposed under the first emissive display device 2. For the purposes of the present invention, the first emissive display device 2 is capable of switching between a passive state in which it is at least partially transparent, and an active state in which it emits light to display information. As for the second reflective display device 6, it is able to switch between a passive state in which it is absorbent and an active state in which it is able to reflect the ambient light.
    Preferably, but not absolutely, the first emissive display device 2 is secured to the second reflective display device 6 by means of a transparent adhesive layer 8. This transparent adhesive layer 8 may be formed of an adhesive film transparent optical adhesive type (also known as Optical Clear Adhesive or OCA) or a layer of acrylic liquid glue or silicone. This transparent adhesive layer 8 is intended to avoid the problems of spurious reflections that would occur if the two display devices 2, 6 were separated by a layer of air and which would degrade the optical quality of the display assembly 1 according to the invention.
    FIG. 2 is a detailed sectional view of an exemplary embodiment of the display assembly 1 according to the invention in the case where the first emissive display device 2 comprises a transparent emissive display cell 20 with organic electroluminescent diodes. which will be referred to in the following as each transparent TOLED display cell (Transparent Organic Light Emitting Diode). As for the second reflective display device 6, it comprises a reflective liquid crystal display cell 60 of helical nematic type, also known by its Anglo-Saxon name Twist Nematic or TN.
    More specifically, the transparent display unit TOLED 20 comprises a transparent substrate 21 made of glass or a plastic material and an encapsulation cover 22 which extends parallel to and away from the transparent substrate 21. The substrate 21 and the encapsulation cover 22 are joined together by a sealing frame 23 which delimits a closed volume protected from air and moisture for the confinement of a stack of electroluminescent layers generally designated by 24. A transparent upper electrode 25 made for example of tin-indium oxide or ITO and a transparent lower electrode 26 made for example by means of a metallic material such as aluminum or gold or of a metal oxide such as ITO or zinc-indium oxide are structured on either side of the stack of electroluminescent layers 24. These elec trodes 25, 26, made of a metallic material, are slightly reflective. The organic electroluminescent light-emitting diode display cells are available either with direct addressing in cases where it is simply a question of displaying icons or segments, or with a passive matrix type addressing in the case of a dot matrix display. In the case of a dot matrix display, it may also be necessary to make an active matrix type addressing combined with transparent transistors of the Thin Film Transistor or TFT type intended to control the current and which are formed in the pixels. on the side of the transparent substrate 21 of the transparent display cell TOLED 20.
    On the other hand, the reflective liquid crystal display cell 60 comprises a front substrate 61 disposed on the side of the observer 4 and a rear substrate 62 which extends parallel to and away from the front substrate 61. The front 61 and rear 62 substrates are joined together by a sealing frame 63 which delimits a sealed enclosure 64 for the confinement of a liquid crystal whose optical properties are modified by applying an appropriate voltage to a crossover point considered. between transparent electrodes 65a formed on a lower face of the front substrate 61 and transparent counter-electrodes 65b formed on an upper face of the rear substrate 62. The electrodes 65a and the counter-electrodes 65b are made of an electrically conductive transparent material such that indium-zinc oxide or indium-tin oxide, the latter material being better known as appointment Anglo-Saxon Indium Tin Oxide or ITO.
    In the case of the present invention, all the liquid crystal phases such as helical nematic (Twist Nematic or TN in English terminology), super-nematic helix (Super Twist Nematic or STN in English terminology). ) or else vertically aligned (Vertically Aligned or VA in English terminology) can be envisaged. Similarly, all types of addressing such as direct addressing, addressing by active matrix or multiplex addressing of a passive matrix can be envisaged.
    An absorbent polarizer 30 is adhered to an upper face of the front substrate 61 of the reflective liquid crystal display cell 60 by means of an adhesive layer 32. This adhesive layer 32 may be formed of a film adhesive or a layer of liquid glue. The adhesive used to secure the absorbing polarizer 30 on the reflective liquid crystal display cell 60 may be transparent or slightly diffusing depending on whether one seeks to obtain specular or diffuse reflection. As for the absorbing polarizer 30, it may be, for example, of the iodine or dye type.
    An absorbent reflective polarizer 34 is bonded to a lower face of the rear substrate 62 of the reflective liquid crystal display cell 60 by means of an adhesive layer 36 which may be transparent or slightly diffusing depending on whether one is looking for to obtain specular or diffuse reflection.
    For the purposes of the present invention, the term absorbing reflective polarizer 34 is understood to mean a polarizer which reflects the component of the light whose polarization direction is parallel to the axis of reflection of the absorbent reflective polarizer, and which absorbs the other component of the light whose direction of polarization is transverse to the direction of polarization of the component of the light reflected by the absorbent reflective polarizer 34.
    By way of a preferred but in no way limiting example, the absorbent reflective polarizer 34 may consist of an absorbing polarizer disposed above a reflector b, or of a transmissive reflective polarizer disposed above an absorption layer d. For the purposes of the present invention, the term reflective-transmissive polarizer means a polarizer which reflects one of the components of the light and passes without modification the other component of the light whose direction of polarization is transverse to the direction of light. polarization of the component of the light reflected by the transmissive reflective polarizer d.
    We now examine in conjunction with FIGS. 3A to 3D the operating principles of the display assembly 1 according to the invention according to whether the TOLED transparent display cell 20 and the reflective liquid crystal display cell 60 are in use or not. It will be assumed, by way of purely illustrative and in no way limiting example, that the reflective liquid crystal display cell 60 is a nematic TN helical liquid crystal cell and that the transmission axis of the absorbing polarizer 30 and the reflective axis of the absorbent reflective polarizer 34 are parallel.
    In FIG. 3A, the TOLED transparent display cell 20 and the TN 60 reflective liquid crystal display cell are both turned off. The ambient light, denoted by the numeral 46, passes through the transparent display cell TOLED 20 without modification, and is then polarized linearly by the absorbing polarizer 30. The ambient light 46 is then rotated by 90 ° as it passes through the cell reflective liquid crystal display TN 60, so that when it falls on the reflective reflective polarizer 34, its direction of polarization is perpendicular to the axis of reflection of the reflective reflective polarizer 34 and is therefore absorbed by the latter. The reflective liquid crystal display cell TN 60 therefore appears dark when it is off, which means that the information it will display will appear in the light on a dark background. The display of information is therefore in negative contrast. Of course, a display of information in positive contrast can be achieved simply by ensuring that the transmission axis of the absorbing polarizer 30 and the reflection axis of the reflective reflective polarizer 34 are perpendicular.
    In FIG. 3B, the transparent display unit TOLED 20 is activated, while the reflective liquid crystal display unit TN 60 is deactivated. The light emitted by the TOLED transparent display cell 20 reaches the observer 4 without modification, while the TN 60 reflective liquid crystal display cell appears dark. The information displayed by the transparent display unit TOLED 20 therefore stands out against a dark background.
    In FIG. 3C, the transparent display unit TOLED 20 is off, while the reflective liquid crystal display unit TN 60 is activated. As already explained above, the unswitched areas of the TN 60 reflective liquid crystal display cell appear dark. On the other hand, in switched areas of the TN 60 reflective liquid crystal display cell, ambient light 46 passes through these areas without modification, so that ambient light 46 falls on the absorbing reflective polarizer 34 with a parallel polarization direction. to the reflection axis of this absorbent reflective polarizer 34. The ambient light 46 is thus reflected back and passes successively through the TN 60 reflective liquid crystal display cell, the absorbing polarizer 30 and the transparent display cell TOLED 20 without modification, so that it is perceptible by the observer 4. The information is displayed in clear on a dark background.
    In FIG. 3D, the TOLED transparent display cell 20 and the TN 60 reflective liquid crystal display cell are both activated. The light emitted by the transparent display unit TOLED 20 is directly perceptible by the observer 4. The ambient light 46 which passes through the unswitched areas of the TN 60 reflective liquid crystal display cell is absorbed by the absorbing reflective polarizer. 34, so these areas appear dark. Finally, the ambient light 46 which passes through the switched areas of the TN 60 reflective liquid crystal display cell is reflected by the absorbent reflective polarizer 34 so that these areas appear clear.
    FIG. 4 is a sectional view of an exemplary embodiment of the display assembly 1 according to the invention in the case where the first display device 2 comprises the TOLED transparent emissive display cell 20. As for the second device 6, it comprises a vertically aligned reflective liquid crystal display 600, also known by its Anglo-Saxon Vertically Aligned or VA. The reflective liquid crystal display unit VA 600 comprises a front substrate 601 disposed on the observer's side 4, and a rear substrate 602 which extends parallel to and away from the front substrate 601. The substrates before 601 and rear 602 are joined together by a sealing frame 603 which delimits a sealed enclosure 604 for the confinement of a liquid crystal whose optical properties are modified by applying a suitable voltage to a crossover point considered between transparent electrodes 605a arranged on a lower face of the front substrate 601 and against transparent electrodes 605b formed on an upper face of the rear substrate 602. The electrodes 605a and the counter electrodes 605b are for example made of indium tin oxide or ITO. The absorbent polarizer 30 is attached to an upper face of the front substrate 601 of the VA 600 reflective liquid crystal display cell. The reflective reflective polarizer 34 is attached to a bottom face of the rear substrate 602 of the crystal display cell. reflective liquid VA 600.
    We now examine in conjunction with FIGS. 5A to 5D the principles of operation of the display unit 1 according to the invention according to whether the transparent display unit TOLED 20 and the reflective liquid crystal display unit VA 600 are in use or not. It will be assumed, by way of a purely illustrative and in no way limiting example, that the transmission axis of the absorbing polarizer 30 and the axis of reflection of the absorbent reflective polarizer 34 are perpendicular.
    In FIG. 5A, the TOLED transparent display cell 20 and the VA 600 reflective liquid crystal display cell are both turned off. The ambient light, denoted by the numeral 46, passes successively through the transparent display unit TOLED 20 and the reflective liquid crystal display unit VA 600, so that when it falls on the absorbent reflective polarizer 34, its direction of polarization is perpendicular to the axis of reflection of the reflective polarizer absorbent 34 and is absorbed by the latter. The reflective liquid crystal display unit VA 600 therefore appears dark when it is off, which means that the information it will display will appear in light on a dark background. The display of information is therefore in negative contrast. Of course, a display of the information in positive contrast can be obtained simply by ensuring that the transmission axis of the absorbing polarizer 30 and the reflection axis of the absorbent reflective polarizer 34 are parallel.
    In FIG. 5B, the transparent display unit TOLED 20 is activated, while the reflective liquid crystal display unit VA 600 is deactivated. The light emitted by the transparent display unit TOLED 20 reaches the observer 4 without modification, while the reflective liquid crystal display unit VA 600 appears dark. The information displayed by the transparent display unit TOLED 20 therefore stands out against a dark background.
    In FIG. 5C, the transparent display unit TOLED 20 is off, while the reflective liquid crystal display unit VA 600 is activated.
    In a vertically aligned liquid crystal cell, the alignment layers are oriented at 45 ° with respect to the polarization axes of the polarizers. On the other hand, the product result between the birefringence of the liquid crystal molecules and the distance between the front and back substrates is chosen so that, when the liquid crystal is switched, it behaves vis-à-vis the direction polarization of light as a half-wave plate. Therefore, since this half-wave plate is placed at 45 ° with respect to the polarization axis of the absorbing polarizer, it causes a 90 ° rotation of the polarization direction of the light. Thus, the ambient light 46 is rotated by 90 ° as it passes through the switched areas of the VA 600 reflective liquid crystal display cell, so that when it falls on the absorbing reflective polarizer 34, its polarization direction is parallel to the reflection axis of the reflective reflective polarizer 34 and is therefore reflected by the latter. As for the ambient light 46 which passes through the unswitched areas of the VA 600 reflective liquid crystal display cell, it is absorbed by the absorbent reflective polarizer 34. The information is thus displayed in the light on a dark background, it is that is, with a negative contrast.
    In FIG. 5D, the transparent display unit TOLED 20 and the reflective liquid crystal display unit VA 600 are both activated. The light emitted by the transparent display unit TOLED 20 is directly perceptible by the observer 4. The ambient light 46 which passes through the unswitched areas of the VA 600 reflective liquid crystal display cell is absorbed by the absorbing reflective polarizer. 34, so these areas appear dark. Finally, the ambient light 46 which passes through the switched areas of the VA 600 reflective liquid crystal display cell is reflected by the absorbent reflective polarizer 34 so that these areas appear clear.
    FIG. 6 is a detailed sectional view of an alternative embodiment of the display assembly t according to the invention illustrated in FIG. 4. In order to suppress the parasitic reflections and thus improve the display contrast, a circular polarizer 38 is placed above the transparent display unit TOLED 20, on the observer's side 4, which consists of a second absorbing polarizer 40 and a first quarter-wave plate 42. On the other hand, the absorbent reflective polarizer 34 is replaced by a metal mirror 44. This variant also makes it possible to reduce the number of components and reduce the parallax effect because the metal mirror 44 can be placed as close to the switching plane of the liquid crystal.
    Addressing the electroluminescent zones of electroluminescent organic diode display cells is provided by transparent electrodes most often made using a metallic material or a metal oxide. These electrodes therefore often cause optical reflection phenomena which induce a degradation of the contrast, which affects the readability of the information displayed by the organic light emitting diode display cells.
    To overcome this drawback, the present invention teaches to have a circular polarizer 38 above the transparent display cell TOLED 20 and a metal mirror 44 under the transparent display cell TOLED 20. Thus, the light ambient 46 which enters the display assembly 1 according to the invention is polarized linearly by the second absorbing polarizer 40, and then circularly polarized by the first quarter wave plate 42. When crossing the transparent display cell TOLED 20, the ambient light 46, circularly polarized, is partially reflected by the transparent upper and lower electrodes 25, 26 of the transparent display cell TOLED 20, this reflected light is phase-shifted, which has the effect of transforming its circular polarization in circular polarization of opposite direction of rotation. Thus, when the reflected light crosses again the circular polarizer 38, it is absorbed by the latter. In this way, it is possible to eliminate the stray light that is reflected on the electrodes 25, 26 of the transparent display cell TOLED 20. The remaining ambient light 46 passes through the transparent display cell TOLED 20, and then the reflective liquid crystal display unit VA 600 and is finally reflected by the metal mirror 44 which reverses the direction of circular polarization. Thus, after having crossed again without modification the reflective liquid crystal display unit VA 600 and the transparent display cell TOLED 20, the ambient light 46 is finally absorbed by the circular polarizer 38.
    The display is done in clear on a dark background. In other words, the display unit 1 is in negative contrast. Indeed, when it passes through the switched areas of the reflective liquid crystal display unit VA 600, the ambient light 46 which has been circularly polarized by the circular polarizer 38 and which then passes through the transparent display cell TOLED 20 without modification, is polarized linearly. Therefore, when the ambient light 46 is reflected on the metal mirror 44, its polarization direction remains linear. On the other hand, when it crosses again the reflective liquid crystal display unit VA 600, the ambient light 46 is circularly polarized in the same direction as the circular polarization which has been printed to it by the circular polarizer 38 when has penetrated the display assembly 1. Therefore, it can pass through the circular polarizer 38 without being absorbed and is finally perceptible by the observer 4.
    FIG. 7 is a view similar to that of FIG. 6 except that a second quarter-wave plate 48 is placed between the transparent display unit TOLED 20 and the reflective liquid crystal display unit VA 600. This second quarter-wave plate 48 is parallel to the first quarter wave plate 42 or disposed at 90 ° relative to the first quarter wave plate 42.
    Circularly polarized by the circular polarizer 38, the ambient light 46 which enters the display assembly 1 passes through the transparent display cell TOLED 20 without modification, then is converted to light linear polarization after its passage to through the second quarter-wave plate 48. Polarized linearly, the ambient light 46 then passes unchanged through the unswitched zones of the VA 600 reflective liquid crystal display cell and is finally reflected without modification by the metal mirror 44. back, the ambient light 46 follows the same path and is finally perceptible by the observer 4. In the switched areas of the reflective liquid crystal display unit VA 600, the ambient light 46, initially linearly polarized after passing through the second quarter-wave plate 48 is circularly polarized by the display cell at Reflective liquid crystal VA 600. The ambient light 46 is then reflected by the metal mirror 44, so that it undergoes a phase shift which has the effect of transforming its circular polarization circular polarization opposite direction of rotation. While passing through the switched areas of the reflective liquid crystal display unit VA 600, the ambient light 46 returns to a linear polarization oriented at 90 ° with respect to the linear polarization which was its in the forward direction. It then passes through the second quarter wave plate 48 and is circularly polarized in a direction of rotation opposite to that which was its in the forward direction. The ambient light 46 passes through the transparent display cell TOLED 20 without modification and is finally linearly polarized by the first quarter wave plate 42 in a 90 ° orientation with respect to the linear polarization which was its in the forward direction. It is therefore absorbed by the linear absorbing polarizer 40. The display is therefore dark on a light background. In other words, the display unit 1 is of the positive contrast type.
    FIG. 8 is a view similar to that of FIG. 2 except that, for the purpose of suppressing parasitic reflections and thereby improving the display contrast, the polarizer is placed above the transparent display cell TOLED 20, on the observer's side 4 circular circular 38 which consists of the second absorbing polarizer 40 and the first quarter wave plate 42. On the other hand, the second quarter wave plate 48 is placed under the transparent display cell TOLED 20. This second quarter blade 48 is parallel to the first quarter wave plate 42 or disposed at 90 ° relative to the first quarter wave plate 42. It will be assumed that the transmission axis of the second absorbing polarizer 40 and the axis reflective reflective reflective polarizer 34 are perpendicular.
    Thus, the ambient light 46 which enters the display unit 1 according to the invention is polarized linearly by the second absorbing polarizer 40, and then circularly polarized by the first quarter wave plate 42. When crossing the TOLED transparent display cell 20, the circularly polarized ambient light 46 is partially reflected by the transparent upper and lower electrodes 25, 26 of the transparent display cell TOLED 20, this reflected light is phase shifted, which has the effect of to convert its circular polarization into circular polarization of opposite direction of rotation. Thus, when the reflected light crosses again the circular polarizer 38, it is absorbed by the latter. In this way, it is possible to eliminate the stray light that is reflected on the electrodes 25, 26 of the transparent display cell TOLED 20. The remaining ambient light 46 passes through the transparent display cell TOLED 20, and then is linearly polarized during its passage through the second quarter wave plate 48 in a direction perpendicular to the transmission axis of the second absorbing polarizer 40. It is assumed that the first and second quarter wave plates 42 and 48 are parallel to each other. As ambient light 46 passes through the reflective liquid crystal display cell 60, the direction of polarization of the ambient light 46 is rotated 90 °, so that it is finally absorbed by the absorbing reflective polarizer 34. .
    The display is done in clear on a dark background. In other words, the display unit 1 is in negative contrast. Indeed, in the switched areas of the reflective liquid crystal display cell 60, the ambient light 46 passes through the reflective liquid crystal display cell 60 without modification, so that it falls on the absorbent reflective polarizer 34 according to a polarization direction which is parallel to the axis of reflection of the latter. The ambient light 46 is thus reflected by the absorbent reflective polarizer 34, then passes through the reflective liquid crystal display cell 60 without modification. The ambient light 46 is then circularly polarized by the second quarter-wave plate 48, then passes through without modification the circular polarizer 38 and is perceptible by the observer 4.
    As a variant, it is possible to envisage arranging the second quarter-wave plate 48 between the reflective liquid crystal display cell 60 and the absorbent reflective polarizer 34.
    According to a second embodiment of the invention, the first display device comprises the electroluminescent organic diode transparent emissive display cell 20, and the second display device comprises a reflective display cell devoid of polarizers. The reflective display cell may be an electrophoretic display cell, a dichroic liquid crystal display cell, or a cholesteric liquid crystal display cell (e.g., electronic ink or e-ink). In the example illustrated in FIG. 9, the reflective display cell is an electrophoretic display cell 70 bonded under the organic electroluminescent diode transparent emissive display cell 20 by means of an adhesive layer 50. This electrophoretic display cell 70 comprises a front substrate. 71 and a rear substrate 72 between which is arranged the optically active layer 73 which results from the mixing of two powders of different colors, typically white and black. The front substrate 71 is a transparent substrate on the underside of which is formed an electrode. As for the rear substrate 72, it may be a printed circuit board on the upper face of which are structured against the electrodes.
    According to one variant, the reflective display cell is of the cholesteric liquid crystal type and a circular polarizer is disposed above the transparent electroluminescent organic diode display cell in order to absorb the parasitic reflections produced by the electrodes of the latter. Indeed, a cholesteric type liquid crystal display cell has the particularity of reflecting a circular polarization of light. This circular polarization can therefore pass through the circular polarizer without being absorbed.
    It goes without saying that the present invention is not limited to the embodiments that have just been described and that various modifications and simple variants can be envisaged by those skilled in the art without departing from the scope of the invention. as defined by the appended claims. In particular, in the case of a dichroic liquid crystal display cell, the presence of dichroic dyes (black or colored) dispersed in the liquid crystal makes it possible to absorb the ambient light without having to resort to polarizers.
    Nomenclature
    [0052]<tb> Display Set <SEP> 1<tb> First emissive display device <SEP> 2<Tb> Observer <September> 4<tb> Second Reflective Display <SEP> 6<tb> Transparent adhesive layer <SEP> 8<tb> TOLED Transparent Display Cell <SEP> 20<tb> Transparent Substrate <SEP> 21<tb> Encapsulation cap <SEP> 22<tb> Sealing framework <SEP> 23<tb> Stack of electroluminescent layers <SEP> 24<tb> Transparent Upper Electrode <SEP> 25<tb> Transparent lower electrode <SEP> 26<tb> Absorbent polarizer <SEP> 30<tb> Adhesive layer <SEP> 32<tb> Reflective Reflective Polarizer <SEP> 34<tb> Adhesive layer <SEP> 36<tb> Absorbent Polarizer <SEP> a<Tb> reflector <September> b<tb> Transmissive Reflective Polarizer <SEP> c<tb> Absorption layer <SEP> d<tb> Circular Polarizer <SEP> 38<tb> Second Absorbing Polarizer <SEP> 40<tb> First quarter-wave plate <SEP> 42<tb> Metal mirror <SEP> 44<tb> Ambient light <SEP> 46<tb> Second quarter wave plate <SEP> 48<tb> Adhesive layer <SEP> 50<tb> Reflective liquid crystal display panel TN <SEP> 60<tb> Substrate before <SEP> 61<tb> Rear Substrate <SEP> 62<tb> Sealing framework <SEP> 63<tb> Watertight enclosure <SEP> 64<tb> Transparent electrodes <SEP> 65a<tb> Transparent counter electrodes <SEP> 65b<tb> Reflective liquid crystal display panel VA <SEP> 600<tb> Electrophoretic Display Cell <SEP> 70<tb> Substrate before <SEP> 71<tb> Rear Substrate <SEP> 72<tb> Optically active layer <SEP> 73
    权利要求:
    Claims (12)
    [1]
    1. A display unit for a portable object, said display unit (1) comprising a first at least partially transparent emitting display device (2) located on the side of an observer (4), a second device reflective display (6) being arranged under the first emissive display device (2), said second reflective display device (6) being able to switch between a transparent state in which it displays no information and a reflective state when it is activated.
    [2]
    2. Display assembly according to claim 1, characterized in that the emissive display device (2) is fixed on the reflective display device (6).
    [3]
    Display assembly according to claim 2, characterized in that the emissive display device (2) is adhered to the reflective display device (6) by means of a film adhesive or a film coating. liquid glue.
    [4]
    Display assembly according to any one of claims 1 to 3, characterized in that the first emissive display device (2) comprises a transparent emissive display cell with organic electroluminescent diodes (20), and in that the second reflective display device (6) comprises a reflective liquid crystal display cell (60).
    [5]
    5. Display assembly according to claim 4, characterized in that the electroluminescent organic diode transparent emissive display cell (20) comprises a stack of electroluminescent layers (24) sandwiched between a transparent upper electrode (25) and a transparent lower electrode (26)
    [6]
    6. Display assembly according to any one of claims 4 or 5, characterized in that the reflective liquid crystal display cell (60) is selected from the group formed by helical nematic type liquid crystal cells , the helical super-magnetic type liquid crystal cells and the vertically aligned liquid crystal display cells, and that the addressing of these liquid crystal display cells can be direct type, such as active matrix or multiplex addressing type of a passive matrix.
    [7]
    Display assembly according to one of Claims 4 to 6, characterized in that an absorbing polariser (30) is arranged on an upper face of the reflective liquid crystal display cell (60), and a reflective reflective polarizer (34) is disposed under a bottom face of the rear substrate (62) of the reflective liquid crystal display cell (60).
    [8]
    8. Display assembly according to claim 7, characterized in that the absorbent reflective polarizer (34) consists of an absorbing polarizer (a) disposed above a reflector (b), or a polarizer transmissive reflective material (c) disposed above an absorption layer (d).
    [9]
    9. Display assembly according to any one of claims 4 to 6, characterized in that a circular polarizer (38) which consists of a second absorbing polarizer (40) and a first quarter wave plate (42) is placed above the light emitting organic electroluminescent diode emissive display cell (20), and that a second quarter wave plate (48) is placed under the transparent emissive display cell at organic electroluminescent diodes (20).
    [10]
    10. Display assembly according to any one of claims 1 to 3, characterized in that the first emissive display device (2) comprises a transparent emissive display cell with organic electroluminescent diodes (20), and in that the second reflective display device (60) comprises a reflective display cell devoid of polarizers.
    [11]
    Display assembly according to claim 10, characterized in that the reflective display cell is an electrophoretic display cell, a dichroic liquid crystal display cell or a cholesteric liquid crystal display cell.
    [12]
    12. Display assembly according to claim 11, characterized in that, in the case where the liquid crystal display cell is of the cholesteric type, a circular polarizer (38) is disposed above the display cell. transparent organic diode electroluminescent.
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    同族专利:
    公开号 | 公开日
    CH710225B1|2020-12-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CH01545/14A|CH710225B1|2014-10-10|2014-10-10|Display assembly for portable object comprising two superimposed display devices.|CH01545/14A| CH710225B1|2014-10-10|2014-10-10|Display assembly for portable object comprising two superimposed display devices.|
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