This application claims priority of Taiwanese Patent Application No. 105121322, filed on Jul. 6, 2016.
The disclosure relates to a light emitting device, and more particularly to a light emitting device with micro light emitting diode (micro-LED/μLED) chips.
Compared to conventional light emitting technologies (e.g., liquid crystal display), micro-LED is advantageous in its self-emissive property, low optical loss, and high luminance, and is thus expected to solve the problem of low battery life in portable electronic devices, which may result from high power consumption of displays thereof.
In a printing process for manufacturing micro-LEDs, LED wafers are cut into micro-LED chips, followed by forming semiconductor ink with the micro-LED chips mixed therein, and then a printer device may be used to perform layout of the semiconductor ink on a substrate by, for example, screen printing or inkjet printing, resulting in advantages of low equipment cost compared to conventional packaging process, and being applicable to flexible displays. However, since the orientations of the micro-LED chips disposed on the substrate by such process would be random and irregular, it would hardly be possible to make all of the micro-LED chips conduct in practice, leading to low utilization rate of the micro-LED chips.
According to the disclosure, a method for driving light emission of a light emitting device which may alleviate at least one drawback of the prior art includes: providing a light emitting device which includes a plurality of electrode layers that include a first electrode layer and a second electrode layer, and a plurality of light emitting diodes that are disposed between the first and second electrode layers, wherein each of the light emitting diodes has an anode and a cathode, the light emitting diodes include a first group of light emitting diodes and a second group of light emitting diodes, and a voltage resulting from an AC driving voltage signal across the anode and the cathode of each of the light emitting diodes in the first group has a polarity opposite to that of a voltage resulting from the AC driving voltage signal across the anode and the cathode of each of the light emitting diodes in the second group; providing, to the first and second electrode layers, a first electrode voltage signal across the first and second electrode layers to form, between the first and second electrode layers, a first driving voltage signal in such a way that the light emitting diodes in the first group conduct; and providing, to the first and second electrode layers after the provision of the first electrode voltage signal ends, a second electrode voltage signal across the first and second electrode layers to form, between the first and second electrode layers, a second driving voltage signal in such a way that the light emitting diodes in the second group conduct.
According to the disclosure, a light emitting device which may alleviate at least one drawback of the prior art includes a plurality of electrode layers which include a first electrode layer and a second electrode layer, and a plurality of light emitting diodes disposed between the first and second electrode layers. The first electrode layer and the second electrode layer are disposed to receive an AC electrode voltage signal thereacross to form an AC driving voltage signal having a magnitude proportional to that of the AC electrode voltage signal therebetween. Each of the light emitting diodes has an anode and a cathode. The light emitting diodes includes a first group of light emitting diodes and a second group of light emitting diodes. A voltage resulting from the AC driving voltage signal across the anode and the cathode of each of the light emitting diodes in the first group has a polarity opposite to that of a voltage resulting from the AC driving voltage signal across the anode and the cathode of each of the light emitting diodes in the second group. The AC electrode voltage signal is provided in such a way that the light emitting diodes in the first group conduct in positive half-cycles of the AC electrode voltage signal, and that the light emitting diodes in the second group conduct in negative half-cycles of the AC electrode voltage signal.
According to the disclosure, a method for driving light emission of a light emitting device is proposed. The light emitting device includes a plurality of electrode layers which include a first electrode layer and a second electrode layer, a plurality of light emitting diodes disposed between the first and second electrode layers, and an AC voltage generator coupled to the first and second electrode layers. The first electrode layer and the second electrode layer are disposed to receive an AC electrode voltage signal thereacross to form an AC driving voltage signal having a magnitude proportional to that of the AC electrode voltage signal therebetween. Each of the light emitting diodes has an anode and a cathode. The light emitting diodes includes a first group of light emitting diodes and a second group of light emitting diodes. A voltage resulting from the AC driving voltage signal across the anode and the cathode of each of the light emitting diodes in the first group has a polarity opposite to that of a voltage resulting from the AC driving voltage signal across the anode and the cathode of each of the light emitting diodes in the second group. The method includes: by the AC voltage generator, generating an AC electrode voltage signal and providing the AC electrode voltage signal to the first and second electrode layers to form an AC driving voltage signal having a magnitude proportional to that of the AC electrode voltage signal therebetween. The AC electrode voltage signal is a periodic signal that has a waveform alternating between a positive half-cycle state and a negative half-cycle state at a predetermined frequency.
According to the disclosure, a lighting method which may alleviate at least one drawback of the prior art includes: disposing a first group of micro light emitting diodes and a second group of micro light emitting diodes between at least two electrode layers; and providing an AC electrode voltage signal to the at least two electrode layers to drive light emission by the first group of micro light emitting diodes in positive half-cycles of the AC electrode voltage signal, and drive light emission by the second group of micro light emitting diodes in negative half-cycles of the AC electrode voltage signal.
According to the disclosure, a lighting method which may alleviate at least one drawback of the prior art includes: disposing a plurality of first light emitting diodes and a plurality of second light emitting diodes between at least two electrode layers, wherein each of the first and second light emitting diodes has a cathode and an anode that are disposed at opposite ends thereof; and providing an AC electrode voltage signal to the at least two electrode layers to conduct the first light emitting diodes in positive half-cycles of the AC electrode voltage signal, and conduct the second light emitting diodes in negative half-cycles of the AC electrode voltage signal.
According to the disclosure, a lighting method which may alleviate at least one drawback of the prior art includes: randomly disposing a plurality of micro light emitting diodes each having a cathode and an anode such that the micro light emitting diodes include a first group of micro light emitting diodes and a second group of micro light emitting diodes, the cathodes and the anodes of the micro light emitting diodes of the second group having orientations different from orientations of the cathode and the anode of the micro light emitting diodes of the first group; and providing an AC voltage signal to the micro light emitting diodes in such a manner as to conduct the first group of micro light emitting diodes in positive half-cycles of the AC voltage signal, and conduct the second group of micro light emitting diodes in negative half-cycles of the AC voltage signal.
Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment(s) with reference to the accompanying drawings, of which:
Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.
Referring to
The light emitting diodes 12a, 12b are arranged between the first and second electrode layers 10, 11 by for example, but not limited to, screen printing, inkjet printing, etc. Referring to
In this embodiment, due to use of the printing electronics manufacturing process, the micro-LED chips are disposed between the electrode layers 10, 11 in a random manner, and orientations of the same thus vary (i.e., the anodes and the cathodes of the micro-LED chips may face towards different directions). In this embodiment, the light emitting diodes 12a of the first group refers to the micro-LED chips having the cathode (−) and anode (+) respectively coupled to the first and second electrode layers 10, 11, and the light emitting diodes 12b of the second group refers to the micro-LED chips having the anode (+) and cathode (−) respectively coupled to the first and second electrode layers 10, 11. There may still be other micro-LED chips which may be laterally disposed such that at least one of the cathode (−) and the anode (+) thereof is not coupled to either one of the first and second electrode layers 10, 11 (not shown).
In this embodiment, the AC voltage generator 13 is an inverter, such as a half bridge inverter or a full bridge inverter, but this disclosure is not limited thereto.
In
In
The AC voltage generator 13 generates the AC electrode voltage signal (Vac) across the electrode layers 10, 11 with the predetermined frequency of, for example but not limited to, between 400 Hz and 1000 Hz. The AC driving voltage signal has a peak voltage of which an absolute value is greater than a threshold voltage of the micro-LED chips, such that the light emitting diodes 12a of the first group conduct (i.e., in a forward bias state where a voltage between the anode and the cathode is positive) and the light emitting diodes 12b of the second group do not conduct (i.e., in a reverse bias state where the voltage between the anode and the cathode is negative) in positive half-cycles of the AC electrode voltage signal (Vac), and the light emitting diodes 12b of the second group conduct and the light emitting diodes 12a of the first group do not conduct in negative half-cycles of the AC electrode voltage signal (Vac). As a result, the light emitting diodes 12a of the first group emit light in the positive half-cycles of the AC electrode voltage signal (Vac), and the light emitting diodes 12b of the second group emit light in the negative half-cycles of the AC electrode voltage signal (Vac), with the first and second groups alternating in the light emission, resulting in a relatively higher utilization rate of the micro-LED chips, and subjectively, higher perception of brightness to the user. It should be noted that, since the predetermined frequency is set to be much higher than that detectable by human eyes, users may not be aware of the alternate light emission of the first and second groups of the light emitting diodes 12a, 12b.
Referring to
In summary, by virtue of providing the AC electrode voltage signal (Vac) to the electrode layers of the light emitting device 1, two groups of the micro-LED chips may alternately emit light at a predetermined high frequency, resulting in a relatively higher utilization rate of the micro-LED chips while the light flickering is unnoticeable by the users.
In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects.
While the disclosure has been described in connection with what is (are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Number | Date | Country | Kind |
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105121322 | Jul 2016 | TW | national |