JP3680395B2 - Planar light emitting device and driving method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a surface light-emitting device used for a backlight of a liquid crystal display, an illumination operation switch, and the like that emit light by a battery power source and a driving method thereof, and more particularly, a surface for controlling a surface light source driven by a remaining battery power. The present invention relates to a light emitting device and a driving method thereof.
[0002]
[Prior art]
Today, portable electronic devices such as notebook computers, electronic notebooks, and mobile phones using secondary batteries that are battery power sources are rapidly spreading. Along with this, there is an increasing demand for society for a method for driving a portable electronic device for a long time and a display device for displaying the remaining power of a secondary battery or the like. In particular, in a notebook computer or the like, the remaining amount of power storage varies greatly depending on the usage status of the hardware device used and the state of charge of the secondary battery. In addition, hardware devices mounted on notebook computers to be used tend to increase year by year. If the battery capacity is low, data in use may be lost. Therefore, the power storage remaining amount that is the remaining amount of power is always displayed and warned, or the use is restricted by sounding a warning sound according to the remaining amount of the battery. However, the above warning method and the like consume battery power although the amount of remaining power is low. For this reason, there is a problem that the remaining amount of power storage is accelerated. In addition, there is a problem that the warning sound cannot be erased midway because the remaining amount of power storage is unknown.
[0003]
On the other hand, the display screen of the portable electronic device is caused to emit light by a planar light source for backlight, which is one of the most power consuming ones. Examples of such a light source for backlight include a cold cathode tube using a side light system. A light source for a backlight using a cold cathode tube is used as a relatively bright planar light source that can be used for a color liquid crystal or the like. However, the fluorescent tube which is a cold cathode tube to be used has a small outer shape, and the apparatus structure is greatly increased to 4 to 8 mm. In addition, there is a problem in that the lifetime is short, a booster circuit, a stabilization circuit, and the like are required, and the drive circuit is complicated and large in size and consumes a large amount of power. In addition, there has been a problem that the light emission luminance cannot be easily changed with good uniformity.
[0004]
[Problems to be solved by the invention]
Accordingly, the present invention solves the above-described problem, suppresses the battery power from being consumed at an accelerated rate when the remaining amount of power of the battery power source is low, and a planar light emitting device capable of displaying the remaining power source and its driving It is to provide a method.
[0005]
[Means for Solving the Problems]
The present invention includes a battery power source, a light emitting element that emits two or more emission wavelengths using electric power from the battery power source, and a reflector that is optically connected to the light emitting element and provided on at least one main surface. In a planar light emitting device having a light guide plate, a detection unit that detects a remaining amount of power of the battery power source, a comparison unit that compares the detected remaining amount of power with a predetermined amount and determines a predetermined level or less, and a predetermined level or less A planar light emitting device having control means for reducing or stopping power supply to the light emitting element for each emission wavelength. A plurality of light emitting elements that emit two or more emission wavelengths are provided for each emission wavelength, a semiconductor having an emission wavelength of at least 450 to 490 nm, a semiconductor having an emission wavelength of 495 nm to 530 nm, and an emission wavelength of 610 nm to 700 nm. Each of the planar light emitting devices has a semiconductor having the same. Furthermore, it is a planar light emitting device having a liquid crystal device on the planar light emitting device, and is also a planar light emitting device having a color filter on the liquid crystal device.
[0006]
Furthermore, the present invention provides a detection method for detecting the remaining power of a battery power source in a driving method of a planar light emitting device that emits light through a light guide plate with a light emitting element having two or more emission wavelengths by electric power from the battery power source. A comparison step of comparing a value detected by the detection step with a predetermined value stored in advance and outputting a signal when the value is less than or equal to a predetermined value; and controlling power to the light emitting element for each emission wavelength based on the signal A planar light emitting device having a control step.
[0007]
【effect】
According to the configuration of the first aspect, even when the remaining amount of power is small, the remaining amount of power in the battery usage state can be shown without consuming the power of the battery power at an accelerated rate.
With the configuration of claim 2, a planar light emitting device capable of full color display can be obtained.
With the configuration of claim 3, it is possible to provide a planar light emitting device that can be used for a liquid crystal display with reduced power consumption even when the remaining amount of power is low.
With the configuration of the fourth aspect, a planar light emitting device using a liquid crystal display device capable of full color display can be obtained.
According to the driving method of the fifth aspect, even when the remaining amount of power is low, the remaining amount of power can be indicated without increasing battery usage at an accelerated rate.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The inventor of the present application displays the remaining amount of battery power by accelerating consumption by displaying the remaining amount of battery power using a light emitting element having a different emission wavelength used in a backlight or the like. I found that it can be prevented.
[0009]
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the basic configuration of the present invention, and the operation is shown in the flowchart shown in FIG. In FIG. 1, the remaining power of the battery power supply 101 is detected from the voltage and / or current value and compared with a desired value stored. If the compared battery capacity, which is the remaining power level, is less than or equal to a predetermined value stored in advance (less than), a warning pulse is output from the comparing means 103 as the remaining power level is low. The outputted warning pulse is introduced into the control means 104, and the amount of power of the LED for emitting the planar light source is controlled for each emission wavelength of the LED in accordance with the warning pulse to reduce or turn off the light. Therefore, control is performed so as to suppress the power consumption of the white planar light source that is the display 105 that is normally used.
[0010]
More specifically, LEDs 402 that individually emit light emission wavelengths of R (red), G (green), and B (blue) are provided at end portions of the light guide plate 401 having the reflection plate 403, respectively. A planar light source capable of emitting white light by causing each of the RGB LEDs to emit light is used as a backlight light source. The backlight light source is supplied with electric power from a battery power source such as lithium ion or nickel metal hydride as the electronic device is driven. When the remaining amount of the battery power source is sufficient, each of the light emitting LEDs is turned on to emit white light, and a white planar light source that can emit light in a planar manner through the light guide plate. For example, a liquid crystal device, a color filter, and the like are provided on the backlight light source, which is a planar light source, and various data and the like are displayed in color on the display screen using white light emitted from the backlight light source.
[0011]
The remaining amount of power is detected by the detection means 102 using an ammeter and / or a voltmeter connected between terminals of the battery power supply 101 while using the electronic device. If the detected remaining power level is, for example, one tenth or less when the secondary battery is fully charged, it is determined that the remaining power level is low and a warning pulse is issued from the comparison means 103. The control means 104 to which the warning pulse has been input turns off the LED emitting blue light from the white planar light source that has emitted all of RGB, and emits only the green and red LEDs. Thereby, the color can be changed from a white planar light source to a planar light source emitting orange light. Therefore, by turning off the blue LED, the power consumption can be reduced and the light source color of the planar light source can be changed from white to orange to show a warning of the remaining amount of electricity to the viewer.
[0012]
Similarly, when the detected remaining power level is, for example, less than one-twentieth or less at the time of full charge, it is determined that the remaining power level is extremely small, and a further warning pulse is issued from the comparison unit 103. The control means 104 to which the warning pulse is input turns off the LED that emits green light from the planar light source that emits RG and emits orange light. As a result, only the red LED emits light, and the color can be changed from an orange planar light source to a planar light source emitting red light. Therefore, even when the remaining amount of power is extremely low, it is possible to reduce the power consumption of the battery power supply and to extend the use of the electronic device while issuing a warning to a viewer or the like.
[0013]
The constituent members of the present application will be described in detail below.
(Battery power supply 101)
The battery power source 101 used in the present invention is used as a power source for a display 105 or the like used as a backlight for driving and displaying electronic equipment. As the battery power source 101, various types of primary batteries and secondary batteries are used. However, when a portable electronic device is used, it is preferable to use a secondary battery that can be used repeatedly. Examples of such secondary batteries include lithium ion batteries, lithium batteries, nickel metal hydride batteries, nickel cadmium batteries, and the like.
[0014]
The remaining amount of power of the battery power source 101 used in the present application means the remaining amount of battery power that can be used for an electronic device or the like in the case of a primary battery, and is charged in an electronic device or the like in the case of a secondary battery. This means the remaining amount of power that can be used.
[0015]
(Detecting means 102)
The detection means 102 used in the present invention detects the remaining power of the battery power supply 101 in order to use it as basic data used in the comparison means 103. The remaining amount of power of the battery power source 101 may be detected at all times or may be detected at regular intervals. The remaining amount of power of the battery power source 101 can be detected using an ammeter and / or a voltmeter.
[0016]
(Comparison means 103)
As the comparison means 103 used in the present invention, a control for controlling the power of the planar light source if the remaining amount of power detected by the detection means 102 is compared with a predetermined value stored in advance and if it is less than the predetermined value. A signal is sent to the means 104. The predetermined value can be determined as desired according to the device used, the battery, the battery usage state, and the like. When a warning sound is emitted by a speaker, a buzzer, or the like and the remaining amount of power is low, the predetermined value can be made relatively low because it is different from the conventional one that consumes new power. Specifically, it is determined by the device used, the battery power source used, etc., but preferably 10% of full charge can be set to a predetermined value, more preferably 5%. Further, a plurality of predetermined values used in the present invention can be set in stages. Specifically, when there are two types of LEDs having different emission wavelengths constituting the planar light emitting device, the predetermined value is set to one, and the LED having one type of emission wavelength is turned off when the predetermined value or less is reached. When there are three types of LEDs having different emission wavelengths constituting the planar light emitting device, the predetermined value is set to two, and the emission of one type of LED is stopped when the value is equal to or less than the first predetermined value. Further, when the battery power is consumed and becomes equal to or lower than the second predetermined value, the light emission of the other type of LED is stopped. Note that when the number of light-emitting elements is small or the light-emitting output of the light-emitting elements is low, the display luminance is greatly reduced when the LED light emission is stopped for each emission wavelength. Accordingly, the power to the light emitting element is not completely stopped for each emission wavelength, but the display color can be changed by reducing the power to the light emitting element for each emission wavelength. Furthermore, as long as the power consumption in the previous stage is not exceeded, the supply power is stopped for each emission wavelength, and at the same time, the amount of power to the remaining light emitting elements that are not turned off may be increased to alleviate a significant decrease in luminance. Further, in the case of using light emitting elements capable of emitting three colors of RGB, it is preferable to turn off or turn off the lights in order of B (blue), G (green), and R (red). In terms of human vision, it is more difficult to see a decrease in luminance when RG, that is, blue, which is B, is turned off or turned off first, rather than red and green. Similarly, it is difficult to see the decrease in luminance when B is turned off or turned off before R. In particular, it is more preferable to turn off the light in the order of B, G, and R, and to improve the light emission luminance below the total power consumption in the previous stage, since the warning feeling is visually enhanced.
[0017]
In addition, when the electronic device is connected to an external power source such as commercial power, the comparison means is consumed even if the signal from the detection means indicates that the remaining power is low compared to the stored desired value. The planar light source can be controlled using the control means so as to emit white light when there is sufficient power to satisfy the power.
[0018]
The predetermined value described above may be selected as desired according to the electronic device or battery power source and stored in a ROM, RAM, or the like. Further, the comparison judgment between the detected value and the predetermined value can be configured by a circuit using a CPU or a circuit using a comparator IC. In addition, another driver circuit that constitutes an electronic device such as a liquid crystal device and a circuit that constitutes a comparison unit can be configured as a driver device 406 on one substrate for simplification.
[0019]
(Control means 104)
The control means 104 used in the present invention is for stopping or reducing the power supplied from the battery power supply 101 to the planar light source based on the signal from the comparison means 103 for each emission wavelength. When the power supply to the light emitting element 402 is supplied with constant power, the current and / or voltage to the light emitting element is controlled by decreasing or stopping. Further, when the power supply to the light emitting element is performed by pulses, it can be controlled by increasing or stopping the pulse interval. Specifically, a transistor, a relay, or the like can be used.
[0020]
(External power supply 301)
The external power source 301 of the present invention drives a planar light source or the like in combination with a battery power source. Another example of the present invention is shown in FIG. Examples of the external power source 301 include a solar cell or a commercial power source that uses an inverter. When the electronic device is connected to an external power source such as commercial power during the use of the electronic device, it is desirable to control using a control means so that the remaining power can be at least a white planar light source. That is, when these external power supplies 301 are connected, the planar light source is used in a state where all the light emitting elements 401 emit light with the external power supply 301 as long as the power consumption is sufficiently satisfied with only the external power supply. On the other hand, if the power consumption is not sufficiently satisfied even if an external power source or an external power source and a battery power source are used, the present invention will work effectively. Accordingly, the battery power source and the external power source may be connected in parallel and then detected by the detection means.
[0021]
(Light guide plate 401)
The light guide plate 401 used in the present invention is required to efficiently guide the light from the light emitting element 402 into a planar shape and to be excellent in transmittance and heat resistance and to be formed uniformly. The shape of the light guide plate 401 can be various shapes such as a rectangle and a polygon as desired. Specific examples of the constituent material include acrylic resin, glass, and polycarbonate resin. The light guide plate 401 has a thickness of 10 mm or less in view of the arrangement and type of the light emitting elements 402, although the light utilization efficiency increases as the plate thickness increases. By embedding the light emitting element 402 in the end surface of the light guide plate 401, the light guide plate 401 and the light emitting element 402 are optically connected. In addition, if the light guide plate is square, it goes without saying that the light emitting elements may be connected to all four end surfaces, and the number of LEDs that are light emitting elements is not limited. Moreover, the light from the light guide plate can be made uniform by providing a diffusion film on the light guide plate. Further, when a light emitting element that emits three colors of RGB is used, a white pigment is contained in the diffusion film to obtain a multicolor planar light emitting device capable of displaying white. In the case of using a diffusion film that contains white pigment in inverse proportion to the distance from the light emitting element and is shaded, a multicolor planar light emitting device capable of displaying white with improved uniformity can be obtained. Moreover, you may provide a reflective layer partially in a light-guide plate edge part in which the light emitting element was provided through a reflector and a light-guide plate. The reflection layer reflects light emitted from the light emitting element capable of emitting multicolor light or light reflected through the reflection material to the reflection material side again, thereby mixing individual emission colors and improving color mixing. Those having a reflectance of 95% or more with respect to light emitted from the light emitting element are preferable, and those having a reflectance of 98% or more are more preferable. In addition, since it is provided on the light guide plate, it is preferably 3 mm or less, more preferably 1 mm or less in consideration of the arrangement with a liquid crystal device or the like provided thereon.
[0022]
While the reflective layer improves the color mixing property, it is provided on the light emitting surface side of the planar light source. Therefore, if the reflective layer is too large, the area ratio of the surface emitting light source decreases. Accordingly, although it varies depending on the light emitting element, the light guide plate, etc., it is preferably 15 mm or less from the end of the light guide plate.
[0023]
As a material of the reflective layer satisfying the above reflectivity, it was formed by containing barium titanate, aluminum oxide, titanium oxide, silicon oxide, calcium phosphate, etc. as a reflective material in a resin such as polyethylene terephthalate resin, polycarbonate resin, and polypropylene resin. A film-like member is mentioned. Further, a metal film such as Al, Ag, or Cu may be formed on the light guide plate by plating or sputtering. In addition, the surface of the reflective layer may be provided with unevenness to further improve color mixing, and may be configured to scatter light emitted from a light emitting element capable of emitting multiple colors, and may have a multilayer structure to improve reflectivity and scattering. It is also possible. Specifically, the thing which carried out the metal coating on the glass nonwoven fabric for a scattering improvement etc. is mentioned. These reflective layers are attached to the light guide plate by silicon resin, epoxy resin, or the like.
[0024]
In the present invention, the phrase “the light emitting element and the light guide plate are optically connected” means that light emitted from the light emitting element is introduced from the end of the light guide plate. Specifically, the light emitting element is not only embedded in the light guide plate, but also the light emitting element is bonded with a light transmitting resin or the like, or the light emission of the light emitting element is guided to the end face of the light guide plate using an optical fiber or the like. .
[0025]
(Light emitting element 402)
The light-emitting element 402 used in the present invention emits a planar light source using two or more semiconductors having different emission wavelengths. As such a light emitting element, a semiconductor in which a semiconductor such as GaAlN, ZnS, ZnSe, SiC, GaP, GaAlAs, AlInGaP, InGaN, GaN, and AlInGaN is formed as a light emitting layer on a substrate by a liquid phase growth method, an MOCVD method, or the like. Is used. Examples of the semiconductor structure include a homo structure having a MIS junction and a PN junction, a hetero structure, and a double hetero structure. Depending on the material of the semiconductor layer and the degree of mixed crystal, the emission wavelength can be selected from ultraviolet light to infrared light.
[0026]
The light-emitting element can be a light-emitting element capable of emitting a plurality of emission wavelengths by forming a plurality of different light-emitting layers over one semiconductor. Moreover, it can also be set as the light emitting element which has two or more light emission wavelengths by arrange | positioning the several LED chip from which light emission wavelengths differ on a common support body, respectively. Specifically, an LED chip that emits RGB light is arranged on a common substrate, and a light emitting element capable of emitting a plurality of light emission wavelengths can be obtained.
[0027]
The light emission output of the light emission wavelength of the LED is 200 μW or more, more preferably 300 μW or more, although it depends on the area and material of the planar light emitter. If the light emission output of the LED is less than 200 μW, even if the number of LEDs optically connected to the end face of the light guide plate is increased, it is difficult to obtain a light source of uniform planar light emission with sufficient brightness. It is.
[0028]
As a specific material for improving the luminance of the planar light source, it is preferable to use a gallium nitride-based compound semiconductor as a semiconductor emitting green and blue, and in the red, gallium, aluminum, arsenic semiconductors, aluminum, and indium are used. It is preferable to use a gallium, phosphorus based semiconductor. Further, a plurality of LED chips having different wavelengths can be used as desired, and it is not necessary to have the same number for each wavelength. For example, two blue colors and one green color and one red color can be used. Further, the emission wavelength is not necessarily limited to blue, green, and red, and the semiconductor band gap may be adjusted so that yellow or the like can emit light as desired. As a specific example, white light can be emitted using a yellow LED chip sandwiched between blue-green LED chips. For use as a light emitting element of a planar light emitting device capable of emitting multicolor light, the emission wavelength of R (red) is 610 nm to 700 nm, G (green) is 495 nm to 560 nm, and the emission wavelength of B (blue) is 450 nm. To 490 nm.
[0029]
The light emitting element may be directly adhered to the end portion of the light guide plate with a resin or the like, or may be connected to the light guide plate using a support. It is preferable that the support is disposed with no gap from the end face of the light guide plate and is formed with a groove into which each LED chip of the light emitting element can be inserted. Specifically, polycarbonate, polyethylene, acrylic, urethane, vinyl chloride, nylon, and polyethylene terephthalate are preferable as materials that can be formed by heat welding. Furthermore, it is preferable that the support is colored white in order to efficiently reflect the light directed to the end face support of the light guide plate and enter the light guide plate. Further, in a light emitting element capable of emitting multicolor light, the amount of heat generated from the LED increases, and therefore the light emitting element may be disposed on the common support through a heat conducting member. The heat conducting member is required to have good heat conductivity. Specifically, 0.01 cal / cm ² / Cm / ° C. or higher is preferable, more preferably 0.5 cal / cm ² / Cm / ° C. or higher. Examples of materials that satisfy these conditions include iron, copper, aluminum, iron-containing copper, tin-containing copper, and metallized pattern ceramic.
[0030]
(Reflective material 403)
The reflecting material 403 used in the present invention is arranged on the lower side and the side surface of the light guide plate 401 and functions to reflect the light traveling while reflecting the inside of the light guide plate toward the light emitting surface without waste. Accordingly, the shape and size are not specified as long as the light from the light emitting element 402 is scattered in the light guide plate, and the shape and size are not specified, and the case-like member that holds the light guide plate is used or processed on the surface of the light guide plate. You can also. In addition, in order to uniformly emit the planar light source, the reflective material is striped, and the pattern that reduces the area of the reflective material per unit area as it approaches the light emitting element so that the surface brightness is constant. can do. Furthermore, the shape of the reflective material can be changed as appropriate so that the light emission is uniform in plane by the arrangement of the light emitting elements.
[0031]
Examples of such a reflective material include those obtained by processing foamed polyester containing a white pigment into a film. These reflective materials can be attached to the light guide plate by silicon resin or epoxy resin.
[0032]
(Liquid crystal device 404)
The liquid crystal device 404 used in the present invention may be any device as long as it can use light from a light emitting element as a backlight light source, and various liquid crystal molecules are disposed between a transparent glass substrate or a film on which a transparent electrode is formed. The one enclosed and electrically connected is used. Since the present invention reduces the power consumption of the backlight light source in accordance with the remaining power, the liquid crystal device 404 with good transmission efficiency is preferable. Specifically, a liquid crystal device 404 using a TFT (thin film transistor) is preferable. The display 105 can display the liquid crystal device of the planar light emitting device and the planar light source together.
[0033]
(Color filter 405)
The color filter 405 used in the present invention displays RGB emission colors through a filter, and can be a color display device provided on the liquid crystal device 404. Specifically, it can be formed by applying a pigment according to RGB.
Specific examples of the present invention will be described below, but it goes without saying that the present invention is not limited to these examples.
[0034]
【Example】
[Example 1]
A white reflective member, barium titanate dispersed in an acrylic binder, was screen printed on one side of a 2 mm thick acrylic plate and cured to form a back reflector. Next, the acrylic plate on which the back reflector is formed is cut into a 10 × 3 cm rectangle, and the end surface (cut surface) of the acrylic plate is completely polished, and then polished except for the end surface to which the light emitting element is optically connected. A light guide plate on which a reflective material was formed was obtained by forming an Al side reflective material on the surface.
[0035]
On the other hand, each LED chip of the light emitting element used for the planar light source uses InGaN (emission wavelength 525 nm), InGaN (emission wavelength 470 nm), and GaAlAs (emission wavelength 660 nm) as semiconductors of the green, blue and red light emitting layers, respectively. And configured.
[0036]
Specifically, a semiconductor wafer for LED chips that emits red light continuously grows P-type GaAlAs on a P-type gallium arsenide substrate by a temperature difference liquid crystal growth method, and grows N-type GaAlAs thereon, P-type GaAlAs which is a light emitting region is formed. The semiconductor wafer that emits blue and green light is formed by depositing an N-type and P-type gallium nitride compound semiconductor on a 400 μm thick sapphire substrate by MOCVD growth, respectively, to form a heterostructure PN junction. The P-type gallium nitride semiconductor is formed by doping Mg, which is a P-type dopant, and then annealing.
[0037]
Each of the wafers thus formed was 350 μ square, and the RGB LED chip was fixed on a common support as a light emitting element of one pixel by using Ag paste, and electrical connection was performed. The support is formed in a rectangular parallelepiped according to the size of the end face of the light guide plate, and is provided with three holes so that the light emitting elements of one pixel can be arranged respectively. After optically connecting the light guide plate and the support using a translucent resin, a reflective layer was disposed on the end surface of the light guide plate provided with the light emitting elements so as to partially cover the light emitting surface. The reflection layer obtained a reflectance of 99% by incorporating 60 g of barium titanate in 100 g of polycarbonate resin. A TFT liquid crystal device driven by a battery power source and a color filter are arranged on the light guide plate.
[0038]
Control means for controlling the light emission of the LEDs emitting red, green, and blue for each emission color using a transistor is electrically connected between the planar light source thus formed and the lithium ion battery as the battery power source. On the other hand, an ammeter and a voltmeter are connected to the output terminal of the lithium ion battery so that the data flows to the comparison means. The comparison means uses Z80 as the CPU, and the memory IC stores 10% of the power value when the lithium ion battery is fully charged as the first predetermined value, and 5% of the power when the lithium ion battery is fully charged. The value is stored as a second predetermined value. The CPU is electrically connected to the control means so as to stop the power flowing in the blue LED when the remaining amount of charge of the lithium ion battery becomes equal to or less than the first predetermined value. Further, when the remaining battery level of the lithium ion battery becomes equal to or less than the second predetermined value, the green LED is also turned off.
[0039]
When the planar light emitting device formed in this way was made to emit light with a sufficiently charged battery power source, completely uniform planar white light emission was obtained. Brightness is about 81 cd / m ² Met. After 3 hours in this state, the planar light source automatically turned from white to yellow. The remaining amount of electricity stored in the battery power source at this time was measured from an ammeter and a voltmeter connected to the battery power source. The remaining amount of electricity stored in the battery power source was about 10% at full charge, and the power consumption was reduced by about 20%. Brightness is about 70 cd / m ² Met. After an additional 13 minutes, the planar light emitting device automatically changed from yellow to red. Similarly, the result of measuring the remaining amount of electricity is about 5% and the luminance is 31 cd / m. ² Met. After 23 minutes, the brightness dropped significantly, making it unusable.
[0040]
[Comparative Example 1]
The surface light emitting device was driven in exactly the same manner as in Example 1 except that the LED of the surface light emitting device was not turned off by the control means. The brightness was the same as in Example 1. In this state, the remaining amount of electricity stored in the battery power source after 3 hours was measured from an ammeter and a voltmeter connected to the battery power source. The remaining amount of electricity stored in the battery power source was about 10% as in Example 1. The brightness is about 82 cd / m ² Met. After 16 minutes, the brightness was greatly reduced, so it became unusable.
[0041]
[Example 2]
The planar light emitting device has the same configuration as that of the first embodiment except that the light emitting element emitting three colors of red, green, and blue is changed to the light emitting element emitting two colors of yellow and blue. However, after the detection means detects that the remaining amount of battery power is reduced to 10% or less, the comparison means turns off the blue light-emitting element, while the yellow light-emitting element uses comparison means so that the luminance is improved by 50%. It is configured. Further, when commercial power and battery power are electrically connected via an inverter as an external power source, the external power source is configured to drive regardless of the remaining amount of power stored in the battery power source. With this configuration, it is possible to display the remaining amount of electricity while preventing a decrease in luminance and an increase in power consumption.
[0042]
【The invention's effect】
As described above, the planar light emitting device of the present invention can indicate the remaining power level in the battery usage state without consuming battery power at an accelerated rate even when the remaining power level is low. Further, a planar light emitting device capable of full color display can be obtained. Even when the remaining amount of power is small, a planar light emitting device that can be used for a liquid crystal display device with reduced power consumption can be obtained. Furthermore, a planar light emitting device using a liquid crystal display device capable of full color display can be obtained.
The planar light emitting device of the present invention can be used not only as a backlight light source but also as an illumination operation switch.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a planar light emitting device according to the present invention.
FIG. 2 is a flowchart showing driving of the planar light emitting device of the present invention.
FIG. 3 is a block diagram showing an example of another planar light emitting device of the present invention.
FIG. 4 is a schematic cross-sectional view of a planar light emitting device of the present invention.
[Explanation of symbols]
101 ... Battery power
102... Detection means
103 ... Comparison means
104... Control means
105 ... Display
301 ・ ・ ・ ・ ・ External power supply
401 .. Light guide plate
402 ... LED
403 ... Reflector
404 ... Liquid crystal device
405 ... Color filter
406... Drive device

Claims (2)

A battery power source, a light emitting element that emits two or more emission wavelengths using power from the battery power source, a light guide plate optically connected to the light emitting element and provided with a reflective material on at least one main surface, Detecting means for detecting the remaining amount of power of the battery power source, comparing means for comparing the detected remaining amount of power with a predetermined value and determining whether or not the predetermined value is less than the predetermined value, Control means for reducing or stopping power supply to the elements for each emission wavelength, and at the same time increasing the amount of power to the remaining light emitting elements that are not reduced or stopped unless the power consumption of the previous stage is exceeded. Light emitting device. A battery power source, a light emitting element that emits two or more emission wavelengths using power from the battery power source, a light guide plate optically connected to the light emitting element and provided with a reflective material on at least one main surface, In a planar light emitting device having
A plurality of light-emitting elements that emit two or more emission wavelengths are provided for each emission wavelength, and have a semiconductor having an emission wavelength of at least 450 to 490 nm, a semiconductor having an emission wavelength of 495 to 530 nm, and an emission wavelength of 610 to 700 nm. Each has a semiconductor,
Detecting means for detecting the remaining amount of power of the battery power source; comparing means for comparing the detected remaining power amount with a predetermined value to determine whether it is less than a predetermined value; The power to the remaining light emitting elements that have been reduced or stopped in the order of the emission wavelength of ˜490 nm, the emission wavelength of 495 to 530 nm, and the emission wavelength of 610 to 700 nm and not reduced or stopped unless the power consumption of the previous stage is exceeded. A planar light emitting device having control means for increasing the amount.

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