JP4504032B2 - Dual mode display device and display method - Google Patents

Description

  The present invention relates to a display device using a dual mode display element having both display functions of liquid crystal and organic electroluminescence (hereinafter simply referred to as “organic EL”), a display method thereof, and the like.

  Patent Document 1 discloses a dual mode display element that exhibits either a liquid crystal mode or an organic EL mode depending on the value of a voltage applied to the display element.

  The dual mode display element is a liquid crystal layer such as a nematic liquid crystal mixed with a carrier transport material or an organic light emitting material known as an organic EL material, or a liquid crystal layer is laminated on a carrier transport layer or an organic light emitting layer. Is generated by A schematic structure of the dual mode display element is shown in FIG. As is clear from the figure, the element is composed of a carrier transport layer 13 and an organic light emitting layer 14 sandwiched between transparent electrodes 12 on a transparent substrate 11 in the same manner as a normal organic EL element.

  When the carrier transport layer 13 has a liquid crystal function, the carrier transport layer 13 is formed of at least one liquid crystal layer in which a low molecular carrier transport material is dispersed in a nematic liquid crystal layer, and the organic light emitting layer 14 is formed of at least one layer. It is formed of a polymer or a low molecular dispersion polymer. On the other hand, when the organic light emitting layer 14 has a liquid crystal function, the organic light emitting layer 14 is formed of at least one organic light emitting material including a nematic liquid crystal layer, and the carrier transport layer 13 is at least one layer of polymer or low molecular weight material. Formed with a dispersed polymer. Note that a liquid crystal layer may be provided on both the carrier transport layer 13 and the organic light emitting layer 14.

The display mode of the dual mode display element shown in FIG. 1 changes according to the voltage applied by the drive power supply 15. That is, when the voltage applied to the element is lower than the light emission start voltage of the organic EL material, the contrast of the liquid crystal layer included in the carrier transport layer 13 or (and) the organic light emitting layer 14 changes depending on the applied voltage, so the element Presents a liquid crystal function. On the other hand, when the applied voltage exceeds the light emission start voltage, the organic EL element starts to emit light by itself, and thus the element functions as an organic EL display element. As described above, the dual mode display element can freely select the display mode depending on the applied voltage. For example, the display mode can be switched according to the ambient brightness, usage status, or power saving. It is suitable as a display element for a display display panel such as a POS terminal.
JP 2002-25779 A

  An example of the problem to be solved by the present invention is to provide a dual mode display device and a display method in which the configuration of the display element driving circuit is simplified and the adjustment of the display mode switching voltage is facilitated.

  According to the first aspect of the present invention, an organic electroluminescent element including a liquid crystal layer in at least one of the organic light emitting layer and the carrier transport layer, and a plurality of the organic electroluminescent elements sandwiched between the organic electroluminescent elements on the panel. Address lines and data lines, an address line driving circuit for driving each of the address lines, a data line driving circuit for driving each of the data lines with a grayscale potential corresponding to image data in response to a timing signal, Including a mode designation command generation circuit that generates a mode designation command in response to a command input, wherein the address line driving circuit supplies a bias potential to each of the address lines, and The address line is selectively selected according to the timing signal, and the mode is replaced with the bias potential instead of the bias potential. And supplying a driving voltage having a magnitude corresponding to a constant command.

  The invention according to claim 5 is provided by crossing each other with an organic electroluminescent element including a liquid crystal layer in at least one of the organic light emitting layer and the carrier transporting layer and sandwiching the organic electroluminescent element on the panel. A plurality of address lines and data lines, an address line driving circuit for driving each of the address lines, and a data line driving circuit for driving each of the data lines with a gradation potential corresponding to image data in accordance with a timing signal. Including a step of generating a mode designation command in response to a command input, supplying a bias potential to each of the address lines, and the address in response to the timing signal. A line is alternatively selected and the magnitude corresponding to the mode designation command is used instead of the bias potential. Characterized in that it comprises a and supplying the driving voltage.

  A configuration example of a display device using a dual mode display element according to this embodiment is shown in FIG. The display device according to this embodiment includes a display panel 10, an address line group 20, a data line group 30, an address line drive circuit 40, a data line drive circuit 50, and a mode designation command generation circuit 60 as shown in FIG. It is configured.

  In the display panel 10, each address line (A1, A2, A3,...) Constituting the address line group 20 and each data line (D1, D2, D3,...) Constituting the data line group 30 are mutually connected. Crossed and laid. A dual mode display element 10a connected to each of the address line and the data line is provided for each crossing portion.

  The dual mode display element 10a is, for example, an organic EL material having a liquid crystal display function, and a liquid crystal display function is imparted to the organic EL element by incorporating a liquid crystal layer in the carrier transport layer and / or the organic light emitting layer. is there. The element exhibits a liquid crystal display function if the voltage value applied by the address line and the data line is equal to or less than a predetermined threshold value, and exhibits an organic EL display function if the voltage value is equal to or greater than the threshold value. In the present embodiment, the threshold voltage is assumed to be 5 V, but it goes without saying that the present invention is not limited to such a case.

  On the other hand, each address line (A1, A2, A3,...) Constituting the address line group 20 is connected to the address line driving circuit 40, and each data line (D1, D2, D3,. Each is connected to the data line driving circuit 50. The address line drive circuit 40 includes a scan selection switch 40a and a display mode changeover switch 40b for each address line, and the data line drive circuit 50 includes a gradation potential supply circuit 50a for each data line. Yes.

  The mode designation command generation circuit 60 is a circuit that generates a mode switching signal for designating a liquid crystal display mode or an organic EL display mode in accordance with a predetermined command input.

  Next, the operation of the display device according to the present embodiment will be described with reference to FIG. Each of the address lines (A1, A2, A3,...) Connected to the address line driving circuit 40 is normally connected to + 5V through the switch 40a, and is in a so-called non-selected state. When the display operation is started, the switch 40a is sequentially scanned and selected by a scan selection signal supplied from a control circuit (not shown), and the switch is switched in the selected switch 40a, and the contact of the switch becomes + 5V. From the side to the switch 40b side. That is, one address line in the address line group 20 is sequentially selected according to the scanning selection signal, and the selected address line is connected from the + 5V side to the switch 40b side via the switch 40a. Incidentally, in FIG. 2, the address line A2 is selected, and the other address lines are not selected.

  The address line driving circuit 40 is supplied with a mode switching signal from the mode designation command generating circuit 60. When the signal instructs the liquid crystal display mode, the switch 40b is switched to the ground potential side, In the EL display mode, the switch is switched to the -5V side. In FIG. 2, it is assumed that the liquid crystal display mode command is supplied from the mode designation command generation circuit 60, and the switch 40b is switched to the ground side.

  Meanwhile, pixel data signals for one line, one screen, or several screens are supplied to the data line driving circuit 50 from a control circuit (not shown) at a predetermined timing. Based on this, the gradation potential supply circuit 50a generates a gradation potential corresponding to the luminance gradation of the pixels for one line in the range of 0 to 5V, and generates the gradation potential for each data line (D1, D2, D3). , ...).

  That is, in the display device of FIG. 2, the address line A2 is selected by the scanning selection signal, and the address line side of the dual mode display element 10a connected to the same line is connected to the ground potential via the switch 40a and the switch 40b. It is connected to the. On the other hand, the gradation potential corresponding to the gradation of the pixel superimposed for each data line is applied from the data line driving circuit 50 to the data line side of the dual mode display element 10a in the range of 0 to 5V. . Therefore, the drive voltage is applied to the dual mode display element 10a connected to the selection line A2 in the range of 0 to 5V with respect to the ground potential. And since this drive voltage is lower than the threshold voltage (5V) by display mode discrimination mentioned above, these elements function as a liquid crystal display mode.

  Note that the non-selected lines other than the address line A2 are connected to + 5V, which is equal to the maximum potential of the drive voltage (0 to 5V), via the switch 40a of the address line driving circuit 40. No drive current flows through the connected dual mode display element 10a, and there is no possibility that these elements emit light.

On the other hand, when a command for the organic EL display mode is supplied as a mode switching signal from the mode designation command generation circuit 60, the contact of the switch 40b of the address line driving circuit 40 is switched from the ground potential side to the −5V side. Thus, the dual mode display element 10a connected to the selection line A2 has a potential of −5V on the address line side, and a gradation potential of 0 to 5V is applied to the data line side. That is, as a result, the dual mode display element 10a connected to the selection line A2 has
(0-5) V-(-5) V = (5-10) V
This potential difference is added.

  That is, since the dual mode display element 10a connected to the selection line A2 is driven with a voltage of 5 to 10V exceeding 5V which is the discrimination threshold potential in the display mode, the element functions as an organic EL display mode.

  Even in the organic EL display mode, a non-selected line other than A2 is applied with a potential of 5 V equal to the maximum value of the drive voltage as a reverse bias via the switch 40a of the address line drive circuit 40. The dual mode display element 10a connected to these lines does not emit light.

  As described above, in this embodiment, the organic electroluminescent element 10a including the liquid crystal layer in at least one of the organic light emitting layer and the carrier transport layer and the panel 10 are sandwiched between the organic electroluminescent elements and cross each other. A plurality of address line groups 20 and data line groups 30 provided, an address line driving circuit 40 for driving each of the address lines, and a gradation potential corresponding to the image data in accordance with the timing signal. The data line driving circuit 50 supplies a gray-scale potential superimposed on the data line for each data line included in the data line group 30. The address line driving circuit 40 includes a gradation potential supply circuit 50a, and the address line driving circuit 40 is provided for each address line included in the address line group 20. A scan selection switch that supplies a bias potential having the same polarity as the potential, and alternatively selects the address line according to a scan signal and supplies a drive potential according to a mode designation command instead of the bias potential. 40a and a display mode changeover switch 40b.

  Therefore, according to the present embodiment, a driving voltage in the range of 0 to 5 V corresponding to the degree of gradation may be uniformly applied to each data line regardless of the display mode. That is, it is not necessary to provide a display mode changeover switch for each gradation potential supply circuit 50a included in the data line driving circuit 50, and the configuration of the data line driving circuit 50 can be simplified.

  On the other hand, the address line drive circuit 40 can be easily configured because it is only a subordinate connection circuit of the scan selection switch 40a and the display mode changeover switch 40b.

  Furthermore, since the power supply circuit included in the display device does not require the 10 V voltage that has been required in the past, it can be reduced in size and capacity.

  In general, the threshold voltage at which the dual mode display element switches from the liquid crystal display mode to the organic EL display mode often varies due to variations in various parameters in the manufacturing process of the element. In such a case, in this embodiment, the voltage value of −5V supplied to the selection line of the address line driving circuit 40 via the switch 40b is adjusted by, for example, the variable resistor R included in the address line driving circuit 40. By doing so, it becomes possible to cope easily.

FIG. 1 is a configuration diagram showing a schematic structure of a dual mode display element. FIG. 2 is a block diagram showing a configuration of a display device using a dual mode display element according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display panel 10a Dual mode display element 11 Transparent substrate 12 Transparent electrode 13 Carrier transport layer 14 Organic light emitting layer 15 Drive power supply 20 Address line 30 Data line 40 Address line drive circuit 40a Scan selection switch 40b Display mode changeover switch 50 Data line drive circuit 50a gradation potential supply circuit 60 mode designation command generation circuit

Claims (5)

An organic electroluminescent device including a liquid crystal layer in at least one of the organic light emitting layer and the carrier transport layer, a plurality of address lines and data lines provided across the organic electroluminescent device on the panel and crossing each other; A dual mode display device comprising: an address line driving circuit for driving each of the address lines; and a data line driving circuit for driving each of the data lines with a gradation potential corresponding to image data in accordance with a timing signal. ,
Including a mode designation command generation circuit for generating a mode designation command in response to a command input,
The address line driving circuit supplies a bias potential to each of the address lines, and alternatively selects the address line according to the timing signal, and replaces the address line with the mode designation command instead of the bias potential. A dual mode display device characterized by supplying a driving potential of a corresponding magnitude.   The dual mode display device according to claim 1, wherein the address line driving circuit can freely adjust the driving potential.   The address line drive circuit includes a mode designation switch that sets the drive potential in response to the mode designation command, a scan selection switch that selectively supplies the drive potential to the address line in accordance with the timing signal, The dual mode display device according to claim 1, further comprising:   The mode designation switch uses the drive potential as a reference potential of the gradation potential when the mode designation command is a liquid crystal operation mode designation, and sets the drive potential when the mode designation command is an organic electroluminescence operation mode designation. The dual mode display device according to claim 3, wherein the polarity is opposite to the gradation potential. An organic electroluminescent device including a liquid crystal layer in at least one of the organic light emitting layer and the carrier transport layer, a plurality of address lines and data lines provided across the organic electroluminescent device on the panel and crossing each other; A dual mode display method in a display device, comprising: an address line driving circuit for driving each of the address lines; and a data line driving circuit for driving each of the data lines with a gradation potential corresponding to image data in accordance with a timing signal Because
Generating a mode designation command in response to the command input;
A bias potential is supplied to each of the address lines, and the address line is selectively selected according to the timing signal, and a drive potential having a magnitude according to the mode designation command is used instead of the bias potential. Providing a dual mode display method.

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