JP2008078410A - Backlight device and display device using the same - Google Patents

Abstract

A backlight device and a display device using the backlight device that can prevent the light emission quality from being deteriorated at the beginning of lighting are provided.
An LED module including a plurality of light emitting diodes connected in series and a lighting drive circuit (driving unit) for lighting the light emitting diodes of the LED module. In the module, the lighting stable time from the start of lighting to the stable operation is obtained in advance, and the lighting drive circuit 11 drives the light emitting diode 4 to light using the lighting stable time.
[Selection] Figure 1

Description

  The present invention relates to a backlight device, in particular, a backlight device having a light emitting diode as a light source, and a display device using the backlight device.

  In recent years, for example, liquid crystal display devices have been widely used in liquid crystal televisions, monitors, mobile phones, and the like as flat panel displays having features such as thinness and light weight compared to conventional cathode ray tubes. Such a liquid crystal display device includes a backlight device that emits light, and a liquid crystal panel that displays a desired image by acting as a shutter for light from a light source provided in the backlight device. Yes.

  In addition, as the backlight device, an edge light type or a direct type is provided in which a linear light source composed of a cold cathode tube or a hot cathode tube is disposed on the side or below the liquid crystal panel. However, the above-described cold cathode tubes and the like contain mercury, and it is difficult to recycle the discarded cold cathode tubes. Therefore, a backlight device using a light emitting diode (LED) that does not use mercury as a light source has been developed and put into practical use.

  Further, in the conventional backlight device as described above, usually, white light is obtained using a white light emitting diode, or light of each color of red (R), green (G), and blue (B) is emitted. A light emitting diode of a color is provided, and white light is obtained by mixing these three colors of light and emitted as illumination light to the liquid crystal panel.

  However, in the light emitting diode as described above, the luminous efficiency generally decreases as the ambient temperature increases. For this reason, the light quantity balance of RGB color light becomes inadequate, white light cannot be obtained appropriately, or luminance unevenness occurs, resulting in a reduction in light emission quality.

Therefore, in the conventional backlight device, for example, as described in Patent Document 1 below, the distribution of the red light emitted from the red light emitting diode is larger than the light distribution range of the green light emitted from the green light emitting diode. By increasing the light range or increasing the light distribution range of the blue light emitted from the blue light emitting diodes than the light distribution range of the green light, the light quantity balance of the RGB color light can be made appropriate, It was possible to prevent the occurrence of unevenness (decrease in luminous quality).
JP 2005-196989 A

  However, in the conventional backlight device as described above, there is a problem that color unevenness and luminance unevenness occur at the beginning of lighting after starting the lighting driving of the light emitting diode, and it is not possible to prevent deterioration in light emitting quality. there were.

  Specifically, in the conventional backlight device described above, the light distribution range of each color light emitted from each RGB light emitting diode is specified so that the RGB color light is appropriately mixed with the white light. Light emitting diodes were appropriately arranged.

  However, in the light emitting diode, the luminous efficiency may be unnecessarily high until a time of several tens of minutes to about one hour has elapsed since the start of lighting, and a light amount exceeding a desired value (design value) is emitted. There was. That is, at the initial lighting of the light emitting diode, the light amount may increase excessively because the light emitting amount of the light emitting diode itself is small and the ambient temperature is not increased.

  As described above, in the light emitting diode, the initial lighting characteristic at the initial lighting stage is usually an unstable operation state in which the light amount is not stable at a desired value. In addition, light emitting diodes have a greater variation in the initial lighting characteristics of each product than conventional discharge tubes such as cold cathode fluorescent lamps, and even if the light emitting diodes of the same product are the same color, Depending on the characteristics, the initial lighting characteristics of each product may differ significantly. As a result, in the conventional backlight device, the amount of light from each light emitting diode does not become the desired amount of light, uneven luminance occurs, or appropriate white light cannot be obtained, resulting in uneven color, Luminous quality deteriorated.

  In view of the above-described problems, an object of the present invention is to provide a backlight device that can prevent the light emission quality from being deteriorated at the beginning of lighting, and a display device using the backlight device.

To achieve the above object, a backlight device according to the present invention includes an LED module including at least one light emitting diode,
A drive unit for lighting and driving the light emitting diode of the LED module;
In the LED module, the lighting stable time from the start of lighting to the stable operation is obtained in advance, and
The driving unit performs lighting driving of the light emitting diode of the LED module using the lighting stabilization time.

  In the LED module in the backlight device configured as described above, the lighting stabilization time is obtained in advance, and the light-emitting diode included in the LED module is used by the driving unit for the lighting stabilization time obtained. Is driven to light. As a result, the light emitting diode can be driven to be lit while the initial lighting characteristics are known. As a result, unlike the conventional example, it is possible to prevent the light emission quality from deteriorating at the initial lighting stage.

  In the backlight device, in the LED module, the light amount of the emitted light from the LED module is within a predetermined light amount range from the start of lighting, and has continued for a predetermined time within the light amount range. It is preferable that the time until the time is determined as the lighting stabilization time.

  In this case, in the light emitting diode, the lighting initial characteristics can be grasped more accurately, and the amount of light from the LED module at the initial lighting time can be made more appropriate.

  In the backlight device, it is preferable that the drive unit changes an output voltage to the light emitting diode of the LED module according to the lighting stabilization time.

  In this case, the drive unit can drive the light-emitting diode with the output voltage corresponding to the initial lighting characteristic of the light-emitting diode from the start of lighting to stable operation, and reliably prevent the display quality from deteriorating at the initial lighting stage. be able to.

Further, in the backlight device, the driving unit is configured to be able to drive and drive the light emitting diode of the LED module using PWM dimming, and
The driving unit may change the on / off duty ratio of the PWM dimming so that the light emitting diode of the LED module performs a blinking operation according to the lighting stabilization time.

  In this case, the drive unit blinks the light emitting diode by changing the on / off duty ratio of PWM dimming from the start of lighting until stable operation, so compared with the case where the output voltage is changed linearly Thus, it is possible to smoothly change the amount of light at the beginning of lighting, and it is possible to more reliably prevent the display quality from being deteriorated at the beginning of lighting. Moreover, since the drive unit is configured to be able to drive the light emitting diodes using PWM dimming, a backlight device having a wide dimming range can be easily configured.

The backlight device includes a temperature detection unit that detects a temperature in the vicinity of the LED module,
Preferably, the driving unit changes an output voltage to the light emitting diode of the LED module using a detection result from the temperature detection unit.

  In this case, since the drive unit lights and drives the light emitting diode of the LED module in a state where the temperature in the vicinity of the LED module (ambient temperature) is grasped, even when the ambient temperature changes, the drive unit changes the ambient temperature. Accordingly, the light emitting diode can be driven to light. Therefore, it is possible to prevent the light emitting diode from performing an unstable lighting operation as much as possible.

Further, in the backlight device, a plurality of the LED modules having different emission colors are provided,
In the plurality of LED modules, the lighting stabilization time is obtained for each emission color based on a change in chromaticity from the time of starting lighting, and
The driving unit may perform lighting driving of the light emitting diode of the corresponding LED module using the lighting stabilization time for each emission color.

  In this case, in the plurality of LED modules, since the lighting stable time for each emission color is obtained based on the chromaticity change of the entire light emitting surface of the backlight device, each lighting stability time of the plurality of LED modules can be easily obtained. Can do.

  In the backlight device, the LED module may be provided for each of red (R), green (G), and blue (B) RGB colors.

  In this case, the amount of light of each color of RGB can be made appropriate more easily, the color purity of each color light of RGB can be improved, and a backlight device with better light emission quality can be easily configured. be able to.

  Further, in the backlight device, the driving unit changes an output voltage to a light emitting diode of the red LED module according to the lighting stabilization time for the red LED module among the RGB LED modules. It is preferable.

  In this case, the drive unit turns on the red light emitting diode with the output voltage corresponding to the grasped initial lighting characteristics for the red light emitting diode whose lighting operation is the most unstable among the RGB light emitting diodes. Since it is driven, it is possible to more effectively prevent a reduction in light emission quality at the initial lighting stage.

The display device of the present invention is a display device including a display unit,
The display unit is irradiated with light from any one of the backlight devices.

  In the display device configured as described above, the display unit is irradiated with light from the backlight device that can prevent the light emission quality from deteriorating at the beginning of lighting, so that excellent display quality is stably maintained. Thus, a high-performance display device that can be configured can be easily configured.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the backlight apparatus which can prevent that the light emission quality falls at the time of lighting initial stage, and a display apparatus using the same.

  Hereinafter, preferred embodiments of a backlight device of the present invention and a display device using the backlight device will be described with reference to the drawings. In the following description, the case where the present invention is applied to a transmissive liquid crystal display device will be described as an example.

[First Embodiment]
FIG. 1 is a diagram for explaining a backlight device and a liquid crystal display device according to a first embodiment of the present invention. In FIG. 1, in this embodiment, a backlight device 2 of the present invention and a liquid crystal panel 3 as a display unit irradiated with light from the backlight device 2 are provided. The panel 3 is integrated as a transmissive liquid crystal display device 1.

  The backlight device 2 is of an edge light type and includes a plurality of light emitting diodes 4 as light sources and a light guide 5 into which light from each of the plurality of light emitting diodes 4 is introduced. Further, in the backlight device 2, as illustrated in FIG. 1, the plurality of light emitting diodes 4 are provided with either one of the light emitting diodes 4 set on the left side and the right side of FIG. Arranged in the area. In the backlight device 2, planar illumination light is irradiated from the light guide 5 to the liquid crystal panel 3 side.

  The plurality of light emitting diodes 4 include red, green, and blue light emitting diodes that emit red (R), green (G), and blue (B) light, respectively. Are provided with 2-channel LED modules (details will be described later).

  For the light guide 5, for example, a synthetic resin such as a transparent acrylic resin is used. In addition, as illustrated in FIG. 1, the light guide 5 has a rectangular cross section, and the light guides 5 are arranged on the left and right sides of FIG. Light is incident. And in the light guide 5, illumination light is radiate | emitted toward the liquid crystal panel 3 from the light emission surface arrange | positioned facing the diffusion sheet 8 mentioned later.

  Specifically, the left and right light emitting diodes 4 and the light guide 5 are housed in a housing (not shown), and light from each light emitting diode 4 is in a state where light leakage to the outside is prevented as much as possible. It is efficiently introduced directly into the light guide 5 from the corresponding left side surface or right side surface, or indirectly through a reflector. Thereby, in the backlight apparatus 2, the light utilization efficiency of each light emitting diode 4 can be improved easily, and the high brightness | luminance of the said illumination light can be achieved easily.

  In the liquid crystal display device 1, for example, a polarizing sheet 6, a prism (light condensing) sheet 7, and a diffusion sheet 8 are installed between the liquid crystal panel 3 and the light guide 5. With these optical sheets, The brightness of the illumination light from the backlight device 2 is appropriately increased to improve the display performance of the liquid crystal panel 3.

  In the liquid crystal display device 1, a liquid crystal layer (not shown) included in the liquid crystal panel 3 is connected to a drive control circuit 10 with an FPC (Flexible Printed Circuit) 9 interposed therebetween. The liquid crystal layer can be driven pixel by pixel. Further, the drive control circuit 10 is attached on the back side of the light guide 5 of the backlight device 2, for example, in the vicinity of the installation region of the left light emitting diode 4. Further, in the vicinity of the drive control circuit 10, a lighting drive circuit 11 is installed as a drive unit that drives and drives the plurality of light emitting diodes 4.

  Here, the LED module including the plurality of light-emitting diodes 4 will be specifically described with reference to FIG.

  FIG. 2 is a plan view showing a main configuration of the backlight device. As shown in FIG. 2, the plurality of light emitting diodes 4 include light emitting diodes 4 r, 4 g, and 4 b that emit light of each color of RGB as described above. It has come to introduce. In the light guide 5, the introduced RGB color lights are mixed with white light, and the white light is emitted from the light emitting surface as illumination light. Thereby, in the backlight device 2, it becomes possible to improve the light emission quality of the illumination light, and to make the illumination light appropriate for the full-color image incident on the liquid crystal panel 3, so that the display quality of the liquid crystal panel 3 can be easily improved.

  In addition, in the plurality of light emitting diodes 4, the number of RGB light emitting diodes 4 r, 4 g, and 4 b installed according to the size of the liquid crystal panel 3, display performance such as luminance and display quality required for the liquid crystal panel 3, Type, size, etc. are selected.

  Further, as illustrated in FIG. 2, four light emitting diodes 4r, 4g, and 4b for each color of RGB are connected in series on the substrates 12u and 12d, and the corresponding LED modules 4R1, 4G1 for RGB are connected. 4B1, 4R2, 4G2, and 4B2 are formed on the corresponding substrates 12u and 12d. That is, two-channel LED modules 4R1, 4G1, 4B1, 4R2, 4G2, and 4B2 are provided for each RGB color.

  The substrates 12u and 12d are respectively arranged on the upper side and the lower side in the vertical direction where gravity acts when the liquid crystal display device 1 is used, and the side surfaces of the light guide 5 facing each other (see FIG. 1 is installed on the outer peripheral outer side of the corresponding side surface so that the light of the light emitting diode 4 is introduced into the left side surface and the right side surface.

  Further, in each of the LED modules 4R1, 4G1, 4B1, 4R2, 4G2, and 4B2, a lighting stable time from the start of lighting until stable operation is obtained in advance. Further, the lighting driving circuit 11 performs lighting driving of the light emitting diodes 4r, 4g, and 4b of the corresponding LED modules 4R1, 4G1, 4B1, 4R2, 4G2, and 4B2 using the obtained lighting stabilization time. (Details will be described later).

  Further, the plurality of light emitting diodes 4 are driven by being supplied with power from the LED drive power supply unit 11a included in the lighting drive circuit 11 for each of RGB colors. The LED drive power supply unit 11a is configured using a data processing device such as a microcomputer or a PIC (Peripheral Interface Controller), and is connected to a DC power supply (not shown) to drive the light emitting diode 4 at a constant current. Yes.

  Specifically, the LED module 4R1 and the LED module 4R2 are connected to each other in parallel by the wiring 11br. The light emitting diodes 4r of the LED modules 4R1, 4R2 are driven by being supplied with DC power from the R-LED power supply circuit 11ar provided in the LED drive power supply unit 11a.

  Similarly, the LED module 4G1 and the LED module 4G2 are connected to each other in parallel by the wiring 11bg. The light emitting diodes 4g of the LED modules 4G1 and 4G2 are driven by supplying DC power from the G-LED power supply circuit 11ag provided in the LED drive power supply unit 11a.

  Similarly, the LED module 4B1 and the LED module 4B2 are connected to each other in parallel by the wiring 11bb. The light emitting diodes 4b of the LED modules 4B1 and 4B2 are driven by being supplied with DC power from the B-LED power supply circuit 11ab provided in the LED drive power supply unit 11a.

  In addition, a dimming instruction signal is input to the LED drive power supply unit 11 a via an operation input device (not shown) such as a remote controller provided in the liquid crystal display device 1. The LED drive power supply unit 11a is configured to be able to change the luminance for each RGB color in accordance with the input dimming instruction signal.

  As described above, the LED drive power supply unit 11a is provided with the power supply circuit for each color of RGB, and can be configured to drive the light emitting diodes 4r, 4g, and 4b of RGB independently of each other. Has been. Thereby, the light quantity of each color of RGB can be made appropriate more easily.

  Here, the lighting stabilization time will be specifically described with reference to FIG.

  In the present embodiment, the lighting initial characteristics including the lighting stabilization time at the initial lighting are grasped by measuring the illumination light from the light emitting surface of the backlight device 2 with a chromaticity meter.

  Specifically, in the present embodiment, all light emission is performed under a predetermined measurement condition such as an ambient temperature (for example, 25 ° C. (normal temperature)) and a driving condition that is normally driven by the backlight device 2. The diode 4 is turned on. Then, the change over time of the measured data of chromaticity x and y (indicated by curves 51 and 52 in FIG. 3) is obtained from the chromaticity meter, and the LED modules 4R1, 4G1, 4B1, 4R2 are obtained based on the measured data. The lighting stabilization time of 4G2, 4B2 is obtained for each RGB color.

  Specifically, as is apparent from the curves 51 and 52, immediately after the lighting is started, the illumination light emitted from the light emitting surface is reddish white light containing a large amount of red light. The values of chromaticity x and y vary due to variations in the initial lighting characteristics of each product. As the lighting time elapses, each light emitting diode 4 shifts to a stable operation in which the light amount becomes a predetermined value as the ambient temperature rises due to heat generation of the light emitting diode 4 itself.

  More specifically, the chromaticity y becomes substantially a predetermined value after t1 (minutes) from the lighting start time, and the chromaticity x becomes almost predetermined value after t2 (minutes) from the lighting start time. The lighting operation of becomes stable. Further, when the lighting operation of the light emitting diode 4 is in a stable state, the illumination light is mixed with desired white light.

  Further, by applying the time t1 and the actual measurement data of the chromaticity y at the time point and the time t2 and the actual measurement data of the chromaticity x at the time point to a predetermined arithmetic expression, the LED modules 4R1, 4R2, and 4G1 The lighting stabilization time for each of RGB colors 4G2 and 4B1 and 4B2 is calculated.

  Further, in the LED drive power supply unit 11a, the data of the lighting stable time obtained in advance is stored in a memory not shown. The LED drive power supply unit 11a is configured to perform lighting driving of the light emitting diode 4 by appropriately referring to data of the lighting stabilization time. Thereby, in the backlight apparatus 2, the variation in the lighting initial characteristic for every product of the light emitting diode 4 can be eliminated in the lighting initial stage.

  Hereinafter, the operation of the present embodiment configured as described above will be specifically described with reference to FIG. In the following description, the driving operation in the initial lighting after the lighting driving of the light emitting diode 4 is started will be mainly described. In the following description, for the sake of simplicity, the output voltage to the light emitting diode 4r included in the red LED modules 4R1 and 4R2 is changed according to the lighting stabilization time for the light emitting diode 4r. An example will be described.

  In the present embodiment, the LED drive power supply unit 11a applies a constant output voltage from the start of lighting to the light emitting diodes 4g of the green LED modules 4G1 and 4G2, as indicated by a solid line 50g in FIG. Similarly, as indicated by a solid line 50b in FIG. 4, the LED drive power supply unit 11a applies a constant output voltage to the light emitting diodes 4b of the blue LED modules 4B1 and 4B2 from the start of lighting.

  On the other hand, with respect to the light emitting diodes 4r of the red LED modules 4R1 and 4R2, as indicated by a dotted line 50r in FIG. 4, the LED drive power supply unit 11a outputs from the lighting start time to the lighting stabilization time t3. Increase voltage gradually. Then, the LED drive power supply unit 11a is changed to a constant output voltage at the time of the lighting stable time t3 and applies the constant output voltage after the time of the lighting stable time t3.

  Further, the solid lines 50g and 50b, the dotted line 50r, and the lighting stable time t3 indicate the lighting of the LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2, which are obtained based on the chromaticity measurement results illustrated in FIG. This data is determined based on the stabilization time and is stored in advance in the memory. And LED drive power supply part 11a prevents generation | occurrence | production of the red nonuniformity (color nonuniformity) in the lighting initial stage by lighting driving corresponding light emitting diode 4r, 4g, and 4b using these data. Can do.

  When a dimming instruction signal is input via the operation input device, the output voltage to one of the light-emitting diodes 4r, 4g, 4b is changed according to the input dimming instruction signal. (The same applies to each embodiment described later.)

  In the backlight device 2 of the present embodiment configured as described above, the lighting stabilization time is obtained in advance for the LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2. Further, the lighting drive circuit (driving unit) 11 drives the light emitting diodes 4r, 4g, and 4b of the corresponding LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2 using the obtained lighting stabilization time. To do. Thereby, in the backlight device 2 of the present embodiment, the light emitting diode 4 can be driven to be lit in a state where the lighting drive circuit 11 grasps the lighting initial characteristics of the light emitting diode 4. As a result, in the backlight device 2 of the present embodiment, unlike the conventional example, it is possible to prevent the occurrence of color unevenness at the beginning of lighting, and the light emission quality can be prevented from deteriorating.

  In the backlight device 2 of the present embodiment, the LED drive power supply unit (drive unit) 11a changes the output voltage to the red light emitting diode 4r according to the lighting stabilization time, as illustrated in FIG. ing. Thereby, the LED drive power supply unit 11a can drive the light emitting diode 4r with an output voltage corresponding to the initial lighting characteristics of the light emitting diode 4r from the start of lighting to stable operation. That is, the amount of red light is reduced from the start of lighting until stable operation. As a result, in the backlight device 2 of the present embodiment, it is possible to reliably prevent the occurrence of red unevenness (color unevenness) at the initial lighting time and the display quality associated therewith.

  In addition, as described above, in the present embodiment, since the display quality of the backlight device 2 can be reliably prevented from being lowered at the beginning of lighting, the display device exhibits excellent display quality immediately after the start of the display operation, and Therefore, a high-performance display device that can stably maintain the excellent display quality can be easily configured.

[Second Embodiment]
FIG. 5 is a plan view showing a main configuration of a backlight device according to the second embodiment of the present invention. In the figure, the main difference between the present embodiment and the first embodiment is that the LED drive power supply unit is configured to be able to light up and drive the light emitting diode of the LED module using PWM dimming. In addition, about the element which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

  That is, as illustrated in FIG. 5, in the backlight device 2 of the present embodiment, the LED drive power supply unit 11a uses the PWM dimming, and the LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2 light emitting diodes. 4r, 4g, and 4b are configured to be lit.

  Specifically, power is supplied to each light emitting diode 4r of the LED modules 4R1 and 4R2 from an R-LED inverter power supply circuit 21ar provided in the LED drive power supply unit 11a. Is configured to be able to blink by PWM dimming.

  Similarly, power is supplied to each light emitting diode 4g of the LED modules 4G1 and 4G2 from the G-LED inverter power supply circuit 21ag provided in the LED drive power supply unit 11a. It is configured to be able to blink by PWM dimming.

  Similarly, power is supplied to the light emitting diodes 4b of the LED modules 4B1 and 4B2 from the B-LED inverter power supply circuit 21ab provided in the LED drive power supply unit 11a. It is configured to be able to blink by PWM dimming.

  In addition, a predetermined reference voltage having a triangular wave shape, for example, is applied to the LED drive power supply unit 11a for the R-LED inverter power supply circuit 21ar, the G-LED inverter power supply circuit 21ag, and the B-LED inverter power supply circuit 21ab. A reference power supply circuit 21aa to be supplied is provided. In the LED drive power supply unit 11a, as illustrated in FIG. 6, a blinking operation by PWM dimming is performed in the light emitting diodes 4r, 4g, and 4b.

  That is, as shown in FIG. 6A, when the reference power supply circuit 21aa supplies a triangular-wave reference voltage 70a, the R-LED inverter power supply circuit 21ar uses the comparison voltage Cr in FIG. 6B. An exemplary PWM dimming voltage 70r is generated. Then, the R-LED inverter power supply circuit 21ar supplies the PWM dimming voltage 70r to the light emitting diode 4r.

  In addition, the G-LED inverter power supply circuit 21ag generates the PWM dimming voltage 70g illustrated in FIG. 6C using the comparison voltage Cg. The G-LED inverter power supply circuit 21ag supplies the PWM dimming voltage 70g to the light emitting diode 4g.

  Further, the B-LED inverter power supply circuit 21ab generates the PWM dimming voltage 70b illustrated in FIG. 6D by using the comparison voltage Cb. Then, the B-LED inverter power supply circuit 21ab supplies the PWM dimming voltage 70b to the light emitting diode 4b.

  Further, the LED drive power supply unit 11a performs the blinking operation of the light emitting diodes 4r, 4g, and 4b of the corresponding LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2 according to the lighting stabilization time. The on / off duty ratio of PWM dimming is changed.

  Specifically, in the backlight device 2 of the present embodiment, as illustrated by the curve 80 in FIG. 7, the LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2 light emitting diodes 4r and 4g, and The temperature at which 4b performs stable operation, for example, 70 ° C., is measured in advance. The temperature of 70 ° C. at which this stable operation is performed is a measured temperature in the casing of the backlight device 2, and the above-described red unevenness is eliminated and desired white light is emitted as illumination light of the backlight device 2. When the temperature.

  Further, in the backlight device 2 of the present embodiment, the time t4 from the start of lighting until the measured temperature at the housing reaches 70 ° C. is obtained as the lighting stable time, and PWM is based on this lighting stable time. Dimming on / off duty ratio is changed. In the following description, for simplification of description, a case where the on / off duty ratio of PWM dimming to the light emitting diode 4r included in the red LED modules 4R1, 4R2 is changed will be described as an example. .

  Specifically, the reference power supply circuit 21aa supplies the R-LED inverter power supply circuit 21ar with the triangular-wave reference voltage 70a shown in FIG. 8A from the lighting start time to the lighting stabilization time t4. The R-LED inverter power supply circuit 21ar supplies the PWM dimming voltage 70r shown in FIG. 8B to the light emitting diode 4r.

  When the lighting stabilization time t4 is reached, the reference power supply circuit 21aa supplies the triangular-wave reference voltage 70a 'shown in FIG. 8C to the R-LED inverter power supply circuit 21ar. The frequency of the reference voltage 70a 'is smaller than the frequency of the reference voltage 70a. For this reason, as shown in FIG. 8D, the R-LED inverter power supply circuit 21ar supplies the PWM dimming voltage 70r ′ whose on period is longer than the PWM dimming voltage 70r to the light emitting diode 4r. To do. Thereby, in the backlight device 2 of the present embodiment, the amount of red light can be reduced from the start of lighting until the stable operation, as in the first embodiment.

  With the configuration described above, in the backlight device 2 of the present embodiment, it is possible to prevent a decrease in the light emission quality at the initial lighting time, as in the first embodiment. Therefore, in this embodiment, as in the first embodiment, a high-performance display device that exhibits excellent display quality immediately after the start of the display operation and can maintain the excellent display quality stably. Can be configured easily.

  Further, in the backlight device 2 according to the present embodiment, the LED drive power supply unit (drive unit) 11a changes the on / off duty ratio of the PWM dimming until the LED drive power supply unit (drive unit) 11a stably operates from the start of lighting, thereby blinking the light emitting diode 4 Therefore, compared with the case where the output voltage is changed linearly, it is possible to smoothly change the amount of light at the beginning of lighting. As a result, in the backlight device 2 of the present embodiment, it is possible to more reliably prevent the display quality from being deteriorated at the initial lighting stage.

  Further, in the present embodiment, the LED drive power supply unit 11a is configured to be able to drive the light-emitting diode 4 using PWM dimming, so that the backlight device 2 having a wide dimming range can be easily configured. Can do.

[Third Embodiment]
FIG. 9 is a plan view showing the main configuration of a backlight device according to the third embodiment of the present invention. In the figure, the main difference between the present embodiment and the first embodiment is that a temperature sensor for detecting the temperature in the vicinity of the LED module is provided, and the LED driving power source unit is a light emitting diode using the detection result. It is a point to change the output voltage to. In addition, about the element which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

  That is, as shown in FIG. 9, the backlight device 2 of the present embodiment is provided with a temperature sensor 13 as a temperature detection unit. The temperature sensor 13 measures the temperature in the vicinity of the LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2, and is configured to output the detection result to the LED drive power supply unit 11a. .

  Further, the LED drive power supply unit 11a changes the output voltages to the light emitting diodes 4r, 4g, and 4b of the LED modules 4R1 and 4R2, 4G1 and 4G2, and 4B1 and 4B2, using the detection result from the temperature sensor 13. Is configured to do.

  With the configuration described above, in the backlight device 2 of the present embodiment, it is possible to prevent a decrease in the light emission quality at the initial lighting time, as in the first embodiment. Therefore, in this embodiment, as in the first embodiment, a high-performance display device that exhibits excellent display quality immediately after the start of the display operation and can maintain the excellent display quality stably. Can be configured easily.

  Further, in the backlight device 2 of the present embodiment, the LED drive power supply unit (drive unit) 11a uses the detection result from the temperature sensor (temperature detection unit) 13 so that the LED modules 4R1 and 4R2, 4G1 and 4G2, and The light emitting diodes 4r, 4g, and 4b can be driven to turn on in a state where the temperature (ambient temperature) in the vicinity of 4B1 and 4B2 is grasped. As a result, even when the ambient temperature changes, the LED drive power supply unit 11a can drive the light emitting diodes 4r, 4g, and 4b in accordance with the change in the ambient temperature, and the light emitting diodes 4r, 4g, and 4b. Can prevent unstable lighting operation as much as possible.

  In addition to the above description, the temperature sensor 13 is installed in the second embodiment, and the LED drive power supply unit 11a changes the on / off duty ratio of PWM dimming using the detection result of the temperature sensor 13. Thus, the output voltage to the light emitting diode 4 can be changed.

  Specifically, the blinking operation of the light emitting diode 4 may be changed by changing the on / off duty ratio of PWM dimming based on the temperature 70 ° C. at which the stable operation illustrated in FIG.

  In addition to the above description, 2 measures the temperature near the LED modules 4R1, 4G1, 4B1 mounted on the substrate 12u and the temperature near the LED modules 4R2, 4G2, 4B2 mounted on the substrate 12d, respectively. Two temperature sensors are provided. Furthermore, the LED modules 4R1, 4G1, and 4B1 are configured such that the output voltages can be applied to the light emitting diodes 4r, 4g, and 4b of the LED modules 4R2, 4G2, and 4B2 independently of each other. Then, using the detection result of the corresponding temperature sensor, the output voltage to the light emitting diodes 4r, 4g, 4b of the LED modules 4R1, 4G1, 4B1 or the light emitting diodes 4r, 4g, 4b of the LED modules 4R2, 4G2, 4B2 is changed. You can also

  The above embodiments are all illustrative and not restrictive. The technical scope of the present invention is defined by the claims, and all modifications within the scope equivalent to the configurations described therein are also included in the technical scope of the present invention.

  For example, in the above description, the case where the present invention is applied to a transmissive liquid crystal display device has been described. However, the backlight device of the present invention is not limited to this, and an image using light from a light source is used. The present invention can be applied to various display devices including a non-light emitting display unit that displays information such as characters. Specifically, the backlight device of the present invention can be suitably used for a transflective liquid crystal display device or a projection display device.

  In addition to the above explanation, the present invention is installed on a light box for illuminating X-ray film or photographic negatives for irradiating light to make it easy to see, or on a signboard or a wall in a station. It can be suitably used as a backlight device of a light emitting device that illuminates advertisements and the like.

  In the above description, for each of the RGB colors, two LED modules each including four light-emitting diodes connected in series are connected in parallel to each other to constitute a backlight device having a two-channel LED module. However, the present invention includes an LED module including at least one light-emitting diode and a drive unit that drives the light-emitting diode of the LED module to light, and the LED module is lit from the start of lighting until stable operation is performed. The stable time is obtained in advance, and the drive unit may be any device that drives the light emitting diode of the LED module using the obtained lighting stable time, and the number and connection of the light emitting diodes in the LED module. The method is not limited to the above.

  In the above description, the case where two-channel LED modules respectively mounted on two substrates are connected in parallel in each color of RGB has been described, but the present invention is not limited to this. A backlight device in which LED modules of three or more channels mounted respectively on two or more substrates are connected in parallel to each other, or a backlight device in which the LED modules of the plurality of channels are sequentially connected in series can be configured.

  In the above description, the case where red, green, and blue light emitting diodes that emit RGB corresponding color lights are used is described. However, the present invention is not limited to this, and emits white light. The present invention can also be applied to a backlight device including only a white light emitting diode as a light source.

  In the case where the present invention is applied to the backlight device having only the monochromatic light emitting diode as described above, the occurrence of uneven brightness at the beginning of lighting is prevented while eliminating the variation in the individual light amount of the monochromatic light emitting diode, A backlight device capable of preventing a reduction in light emission quality can be configured.

  Furthermore, the present invention can also be applied to a backlight device using light emitting diodes that emit light of different colors and can be mixed with white light, for example, yellow and blue light emitting diodes.

  However, when the red, green, and blue light emitting diodes are used as in the above embodiment, the color purity of each of the red, green, and blue emission colors included in the illumination light can be improved. It is preferable in that the light emission quality of the backlight device can be easily improved and a display device with improved display quality (display performance) can be easily configured.

  In the above description, among the RGB LED modules, the case where the output voltage to the light emitting diode of the red LED module is changed according to the lighting stabilization time for the LED module whose drive unit is red is described. The present invention is not limited to this, and for the green or blue LED module, the output voltage to the light emitting diode of the corresponding LED module may be changed according to the required lighting stabilization time.

  However, as described above, when the output voltage to the light emitting diode of at least the red LED module is changed, the initial lighting characteristics obtained for the red light emitting diode with the most unstable lighting operation at the initial lighting time are obtained. This is preferable in that the red light emitting diode can be driven to light with a corresponding output voltage, and the occurrence of red unevenness can be surely prevented at the initial lighting time and the deterioration of the light emission quality can be more effectively prevented.

  In the above description, as illustrated in FIG. 3, when the entire backlight device is driven to turn on, a plurality of (RGB) light emission colors different from each other based on a change in chromaticity from the start of lighting. Each lighting stable time of the LED module for each color was determined.

  However, the present invention is not limited to this, and the lighting stabilization time of the LED module can also be obtained by directly measuring the amount of light (light quantity) using a light flux meter from the start of lighting. . Specifically, the time until the point when the light amount of the emitted light from the LED module falls within a predetermined light amount range and continues for a predetermined time within the light amount range may be obtained as the lighting stabilization time. Thus, in the case of obtaining the lighting stabilization time using the light amount of the LED module, it is possible to more accurately grasp the initial lighting characteristics of the light emitting diodes included in the LED module, and from the LED module at the initial lighting time. Therefore, it is possible to more reliably prevent the light emission quality from deteriorating.

  In addition to the above description, the lighting stabilization time can be obtained by measuring the luminous intensity of the LED module using a photometer. Furthermore, lighting stable time can also be calculated | required by measuring a light quantity or luminous intensity for the light emitting diode unit contained in the LED module.

  However, as illustrated in FIG. 3, for a plurality of LED modules, when the lighting stabilization time for each emission color is obtained based on the chromaticity change in the entire light emitting surface of the backlight device, the plurality of LED modules It is possible to easily obtain each lighting stable time.

  Further, in the above description, the case where the present invention is applied to the edge light type backlight device has been described, but the present invention is not limited to this, and the lower side (non-display surface) of the display unit (liquid crystal panel) It can also be applied to a direct type backlight device in which a plurality of light emitting diodes are installed on the side). In the case of application to such a direct type backlight device, for example, the LED modules may be arranged so as to be parallel to the vertical direction or the horizontal direction of the display unit.

  Since the backlight device according to the present invention and the display device using the backlight device can prevent the light emission quality from deteriorating at the beginning of lighting, the backlight device can exhibit and maintain excellent light emission quality even immediately after the start of operation. This is effective for a light device and a high-performance display device.

It is a figure explaining the backlight apparatus and liquid crystal display device concerning the 1st Embodiment of this invention. It is a top view which shows the principal part structure of the said backlight apparatus. It is a graph which shows the specific measurement example of lighting time and chromaticity in the said backlight apparatus. 3 is a graph showing a specific example of a relationship between a lighting time and an output voltage in each of the RGB light emitting diodes shown in FIG. 2. It is a top view which shows the principal part structure of the backlight apparatus concerning the 2nd Embodiment of this invention. FIG. 6 is a waveform diagram illustrating an example of lighting operation in each of the RGB light emitting diodes illustrated in FIG. 5, (a) is a waveform diagram illustrating a voltage waveform of a reference voltage, and (b), (c), and (d). These are waveform diagrams showing voltage waveforms of output voltages to the respective RGB light emitting diodes. 6 is a graph showing a specific example of a relationship between a lighting time and a measured temperature in the backlight device shown in FIG. 5. FIGS. 6A and 6B are waveform diagrams showing an example of a lighting operation in the R light emitting diode shown in FIG. 5, and FIGS. (C) and (d) are waveform diagrams showing another specific example of the voltage waveform of the reference voltage and the voltage waveform to the R light emitting diode, respectively. It is a top view which shows the principal part structure of the backlight apparatus concerning the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Backlight apparatus 3 Liquid crystal panel (display part)
4 Light-emitting diode 4r Red light-emitting diode 4g Green light-emitting diode 4b Blue light-emitting diode 4R1, 4R2, 4G1, 4G2, 4B1, 4B2 LED module 11 Lighting drive circuit (drive unit)
11a LED drive power supply unit (drive unit)
13 Temperature sensor (temperature detector)

Claims (9)

An LED module including at least one light emitting diode;
A drive unit for lighting and driving the light emitting diode of the LED module;
In the LED module, the lighting stable time from the start of lighting to the stable operation is obtained in advance, and
The backlight unit characterized in that the driving unit performs lighting driving of the light emitting diode of the LED module using the lighting stabilization time. In the LED module, the time from the start of lighting to the time when the amount of light emitted from the LED module falls within a predetermined light amount range and continues for a predetermined time within the light amount range is the stable lighting state. The backlight device according to claim 1, which is obtained as time. The backlight device according to claim 1, wherein the driving unit changes an output voltage to a light emitting diode of the LED module according to the lighting stabilization time. The drive unit is configured to be capable of lighting and driving the light emitting diode of the LED module using PWM dimming, and
The said drive part changes the on / off duty ratio of PWM dimming so that the light emitting diode of the said LED module may perform blink operation | movement according to the said lighting stable time. The backlight device described. While having a temperature detection unit for detecting the temperature in the vicinity of the LED module,
The backlight device according to any one of claims 1 to 4, wherein the drive unit changes an output voltage to the light emitting diode of the LED module using a detection result from the temperature detection unit. A plurality of the LED modules having different emission colors are provided,
In the plurality of LED modules, the lighting stabilization time is obtained for each emission color based on a change in chromaticity from the time of starting lighting, and
The said drive part is a backlight apparatus of any one of Claims 1-5 which performs the lighting drive of the light emitting diode of a corresponding LED module using the said lighting stable time for every luminescent color. The backlight device according to claim 1, wherein the LED module is provided for each of RGB colors of red (R), green (G), and blue (B). The backlight according to claim 7, wherein the driving unit changes an output voltage to a light emitting diode of the red LED module according to the lighting stabilization time of the red LED module among the RGB LED modules. apparatus. A display device including a display unit,
The display device, wherein the display unit is irradiated with light from the backlight device according to claim 1.

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