Patent Application
20180157120
The present invention relates to a backlight device, particularly, to a backlight device for a liquid crystal display device using an LED (light emitting diode) as a light source.
In recent years, digital devices have become more sophisticated and have higher performance, and demands for higher quality of various types of images are increasing. Therefore, color reproduction range (also referred to as “color gamut”) has been expanded in the fields of display devices, printing devices, imaging devices, and the like. With respect to liquid crystal display devices such as liquid crystal televisions, for example, backlight devices and color filters have been improved to expand the color reproduction range.
In liquid crystal display devices, colors are displayed by additive color mixing of three primary colors. For this reason, a transmissive liquid crystal display device requires a backlight device capable of irradiating a liquid crystal panel with white light including a red component, a green component, and a blue component. In the related art, cold cathode tubes called CCFLs have been widely adopted as the light source of the backlight device. In recent years, however, the adoption of LEDs has been increasing from the perspective of low power consumption and ease of luminance control.
In general, in addition to a chip state LED (LED element), those in which LED elements (LED chip) are covered with lenses (packaged state) are also called “LEDs”. However, in this specification, in order to clearly distinguish the “LED element” and “the one in which the LED element is covered with lens”, “one in which the LED element is covered with lens” is referred to as a “light emitter.”
As described above, a transmission liquid crystal display device requires a backlight device capable of irradiating a liquid crystal panel with white light. Therefore, for example, a backlight device (see
The appearance of an image displayed on the display device such as the liquid crystal display device or the like changes largely depending on the color temperature (the white color temperature when white is displayed). For this reason, the viewer being capable of selecting a desired color temperature according to the type of video to be viewed is preferable, for example. Generally, a function of adjusting the color temperature is provided in display devices in recent years.
Note, the following related art literature are known in relation to the present invention. JP 2008-283155 A discloses an invention of a light emitting device provided with two or more types of light source modules (each light source module including an LED element and a phosphor) that emit lights of mutually different color temperatures. According to this light emitting device, it is possible to change the color temperature along the blackbody locus (locus of blackbody radiation). Further, JP 2008-205133 A discloses an invention of a backlight device having a configuration in which a small size LED element for color adjustment is incorporated in a light emitter composed of a large size LED element and a phosphor excited to emit light by the light emitted from the LED element. According to this backlight device, it is possible to adjust the color temperature by controlling the luminance of the light emitted from the small size LED element.
PTL 1: JP 2008-283155 A
PTL 2: JP 2008-205133 A
When the configuration illustrated in
In the case where the configuration illustrated in
With regards to the configuration disclosed in JP 2008-283155 A, it is possible to generate light having high color rendering properties close to natural light by constructing a white light source with two or more kinds of light source modules. Therefore, the configuration is suitable for lighting. However, with regard to light obtained by this configuration, the half-value width of the light emission spectrum becomes large. Therefore, the color purity decreases. Therefore, the structure disclosed in JP 2008-283155 A is unsuitable as a backlight for a display device.
Accordingly, an object of the present invention is to realize a backlight device capable of adjusting and changing the color temperature without lowering the color purity. Further, an object of the present invention is to enhance the reliability of such a backlight device.
A first aspect of the present invention, including:
a backlight device using a first type light emitter having a light emitting element and a wavelength conversion element for converting a wavelength of light emitted from the light emitting element, the backlight device including
a plurality of kinds of light emitters including at least two kinds of first type light emitters having the same kind of light emitting elements and having the same kind of wavelength conversion elements of the same kind, wherein
the two or more first type light emitters emit lights having mutually different chromaticities and the plurality of kinds of light emitters are configured so that the light emission intensity of the light emitting element included in each light emitter is controlled independently for each kind of light emitters.
According to a second aspect of the present invention, in the first aspect of the present invention, the plurality of kinds of light emitters are three kinds of light emitters.
According to a third aspect of the present invention, in the second aspect of the present invention, a second type light emitter having only a light emitting element is further used as a light source, and the three kinds of light emitters are composed of two kinds of first type light emitters and one kind of second type light emitters.
According to a fourth aspect of the present invention, in the third aspect of the present invention,
the amount of wavelength conversion element included in a first type light emitter of the two types is adjusted so that chromaticity coordinates corresponding to a target color temperature on an xy chromaticity diagram are within in the range of a triangle connecting chromaticity coordinates of light emitted from each of the three kinds of light emitters.
According to a fifth aspect of the present invention, in the third aspect of the present invention, the amount of wavelength conversion element included in the two kinds of first type light emitters is adjusted so that chromaticity coordinates on a blackbody locus corresponding to a color temperature ranging from 4000 K to 14000 K on an xy chromaticity diagram are within the range of a triangle connecting chromaticity coordinates of light emitted from each of the three kinds of light emitters.
According to a sixth aspect of the present invention, in the third aspect of the present invention, the three kinds of light emitters includes:
a first magenta light emitter including a blue light emitting diode element as a light emitting element, and a relatively large amount of red phosphor as a wavelength converting element;
a second magenta light emitter including a blue light emitting diode element as a light emitting element, and a relatively small amount of red phosphor as a wavelength conversion element; and
a green light emitter having a green light emitting diode element as a light emitting element.
According a seventh aspect of the present invention, in the second aspect of the present invention, the three kinds of light emitters are all first type light emitters.
According to an eighth aspect of the present invention, in the seventh aspect of the present invention, on an xy chromaticity diagram, the amount of wavelength conversion elements included in the three kinds of light emitters is adjusted so that chromaticity coordinates corresponding to a target color temperature are within the range of a triangle connecting chromaticity coordinates of light emitted from each of the three kinds of light emitters.
According to a ninth aspect of the present invention, in the seventh aspect of the present invention, the three kinds of light emitters include:
a first white light emitter including a blue light emitting diode element as a light emitting element, a relatively large amount of red phosphor as a wavelength conversion element, and a relatively small amount of green phosphor as a wavelength conversion element;
a second white light emitter including a blue light emitting diode element as a light emitting element, a relatively small amount of red phosphor as a wavelength conversion element, and a relatively large amount of green phosphor as a wavelength conversion element; and
a third white light emitter including a blue light emitting diode element as a light emitting element, a relatively small amount of red phosphor as a wavelength conversion element, and a relatively small amount of green phosphor as a wavelength conversion element.
According to a tenth aspect of the present invention, in the first aspect of the present invention, the plurality of kinds of light emitters are two kinds of first type light emitters, and
the amount of wavelength conversion elements included in the two kinds of first type of light emitters is adjusted so that chromaticity coordinates corresponding to a target color temperature on an xy chromaticity diagram are positioned on a line segment connecting chromaticity coordinates of light emitted from each of the kinds of first type light emitters.
According to an eleventh aspect of the present invention, in the first aspect of the present invention,
the plurality of kinds of light emitters are two kinds of first type light emitters, and include:
a first white light emitter including a blue light emitting diode element as a light emitting element, and a relatively large amount of yellow phosphor as a wavelength conversion element; and
a second white light emitter including a blue light emitting diode element as a light emitting element, and a relatively small amount of yellow phosphor as a wavelength conversion element.
In a twelfth aspect of the present invention, in the first aspect of the present invention, the plurality of kinds of light emitters are two kinds of first type light emitters, and include:
a first white light emitter including a blue light emitting diode element as a light emitting element, a relatively large amount of red phosphor as a wavelength conversion element, and a relatively large amount of green phosphor as a wavelength conversion element; and
a second white light emitter including a blue light emitting diode element as a light emitting element, a relatively small amount of red phosphor as a wavelength conversion element, and a relatively small amount of green phosphor as a wavelength conversion element.
In a thirteenth aspect of the present invention, in the first aspect of the present invention, the light emitting element is a light emitting diode element or a laser diode element.
According to a fourteenth aspect of the present invention, in the first aspect of the present invention, the light emitting element is a light emitting diode element other than a red light emitting diode element.
According to a fifteenth aspect of the present invention, in the first aspect of the present invention, the wavelength conversion element is a phosphor or a quantum dot.
The sixteenth aspect of the present invention is a liquid crystal display device having a liquid crystal panel including a display unit for displaying an image, the backlight device according to the first aspect of the present invention for irradiating light on a backside of the liquid crystal panel, and a backlight control unit for controlling light emission intensity of the plurality of kinds of light emitters for each kind of light emitter.
According to a first aspect of the present invention, the light source is composed of a plurality of kinds of light emitters, and the light emission intensity of the light emitting elements included in each light emitter is controlled independently for each kind of light emitter. Therefore, since the luminance of the light of a plurality of colors can be independently controlled, it is possible to adjust and change the color temperature. Moreover, at least two kinds of light emitters among the plurality of kinds of light emitters have light emitting elements of the same kind and have wavelength conversion elements of the same kind. Regardless of how the light emission intensity of the light emitting element included in each light emitter is controlled, the peak wavelength of the combined light does not change and the color purity does not decrease. Therefore, a backlight device capable of adjusting and changing the color temperature without lowering the color purity is realized.
According to a second aspect of the present invention, the chromaticity coordinates within the range of the triangle connecting the chromaticity coordinates of the three kinds of light emitters can be selected as a white point on the xy chromaticity diagram. For this reason, the white point can be adjusted more suitably.
According to a third aspect of the present invention, effects similar to those of the first aspect of the present invention and the second aspect of the present invention can be obtained.
According to a fourth aspect of the present invention, by controlling the light emission intensity of two kinds of first type light emitters (light emitters including light emitting elements and wavelength conversion elements), it is possible to reliably set the color temperature to a desired color temperature.
According to a fifth aspect of the present invention, the range of color temperatures capable of being set is widened. Further, when the color temperature is set to 6500 K, 9300 K, which are general temperature settings, the probability of occurrence of a light emitter in an unlit state is reduced. Therefore, occurrence of unevenness in luminance is suppressed.
According to a sixth aspect of the present invention, effects similar to those of the first aspect of the present invention and the second aspect of the present invention can be obtained. Further, as a light source, a red light emitting diode element having an output greatly changing according to temperature and a green light emitting diode element having an emission wavelength changing due to a piezo effect are not used. For this reason, luminance can be easily and suitably controlled whereby high reliability can be obtained. Therefore, a highly reliable backlight device capable of adjusting and changing the color temperature without lowering the color purity is realized.
According to a seventh aspect of the present invention, effects similar to those of the first aspect of the present invention and the second aspect of the present invention can be obtained.
According to an eighth aspect of the present invention, by controlling the light emission intensity of three kinds of first type light emitters (the light emitters including the light emitting elements and the wavelength conversion elements), it is possible to reliably set a desired color temperature.
According to a ninth aspect of the present invention, similarly to the sixth aspect of the present invention, a highly reliable backlight device capable of adjusting and changing the color temperature without lowering the color purity is realized.
According to a tenth invention of the present invention, by controlling the light emission intensity of two kinds of first type light emitters (light emitters including light emitting elements and wavelength conversion elements), it is possible to reliably set to a desired color temperature.
According to an eleventh aspect of the present invention, similarly to the sixth aspect of the present invention, a highly reliable backlight device capable of adjusting and changing the color temperature without lowering the color purity is realized
According to the twelfth aspect of the present invention, similarly to the sixth aspect of the present invention, a highly reliable backlight device capable of adjusting and changing the color temperature without lowering the color purity is realized. Further, by adjusting the amounts of red phosphor and green phosphor contained in the first white light emitter and the second white light emitter, it is possible to more precisely adjust and change the color temperature.
According a thirteenth aspect of the present invention, effect similar to the first aspect of the present invention can be obtained.
According to a fourteenth aspect of the present invention, a red light emitting diode element is not used in the light source constituting a backlight device. Since the red light emitting diode element has an output changing largely depending on the temperature, according to the fourteenth aspect of the present invention in which the red light emitting diode element is not used as the light source, reliability is improved and costs are reduced because the light source becomes easy to control. In addition, since the red light emitting diode element has poor emission efficiency, using the red light emitting diode element as the light source can reduce power consumption.
According to the fifteenth aspect of the present invention, effects similar to the first aspect of the present invention can be obtained.
According to the sixteenth aspect of the present invention, a liquid crystal display device capable of adjusting and changing the color temperature without lowering the color purity is realized.
Embodiments of the present invention will be described with reference to the accompanying drawings. Note, descriptions of the same points as those of the first embodiment are omitted as appropriate with respect to the second embodiment and the third embodiment. Further, in the present specification, a light emitter having a light emitting element (LED element or the like) and a wavelength conversion element (phosphor or the like) for converting the wavelength of light emitted from the light emitting element is referred to as “first type light emitter,” and a light emitter having only a light emitting element is referred to as “second type light emitter”.
Referring to
a pixel electrode 41 connected to the drain terminal of the TFT 40;
a common electrode 44 and an auxiliary capacitance electrode 45 commonly provided in the plurality of pixel forming units 4;
a liquid crystal capacitor 42 formed by the pixel electrode 41 and the common electrode 44; and
an auxiliary capacitor 43 formed by the pixel electrode 41 and the auxiliary capacitance electrode 45.
The pixel capacitor 46 is composed of the liquid crystal capacitor 42 and the auxiliary capacitor 43. In the display unit 410 in
An oxide TFT (a thin film transistor using an oxide semiconductor for a channel layer) can be adopted as the TFT 40 in the display unit 410, for example. More specifically, a TFT (hereinafter also referred to as “In—Ga—Zn—O-TFT”) can be adopted as the TFT 40 with In—Ga—Zn—O (indium gallium zinc oxide), which is an oxide semiconductor containing the main components indium (In), gallium (Ga), zinc (Zn), and oxygen (O) that forms the channel layer. By adopting this In—Ga—Zn—O-TFT, in addition to the effect of achieving high definition and low power consumption, the writing speed can be increased beyond conventional levels. Alternatively, a transistor including an oxide semiconductor other than In—Ga—Zn—O (indium gallium zinc oxide) as a channel layer can be adopted. For example, the same effect can be obtained also when a transistor using an oxide semiconductor for a channel layer is adopted containing at least one of indium, gallium, zinc, copper (Cu), silicon (Si), tin (Sn), aluminum (Al), calcium (Ca), germanium (Ge), and lead (Pb). Note, the present invention does not exclude the use of TFTs other than oxide TFTs.
Next, the operation of the components illustrated in
a digital video signal DV, a gate start pulse signal GSP and a gate clock signal GCK for controlling the operation of the gate driver 200;
a source start pulse signal SSP, a source clock signal SCK, and a latch strobe signal LS for controlling the operation of the source driver 300; and
a backlight control signal BS for controlling the operation of the backlight control unit 500.
Based on the gate start pulse signal GSP and the gate clock signal GCK sent from the display control circuit 100, the gate driver 200 outputs the active scan signals G(1) to G(m) to the respective gate bus lines GL1 to GLm, which is repeated with one vertical scanning period as one cycle.
The source driver 300 receives the digital video signal DV, the source start pulse signal SSP, the source clock signal SCK, and the latch strobe signal LS sent from the display control circuit 100 and supplies the driving video signal S(1) to S(n) to the source bus lines SL1 to SLn. At this time, in the source driver 300, at the timing when the pulse of the source clock signal SCK is generated, the digital video signal DV indicating the voltage to be applied to each of the source bus lines SL1 to SLn is sequentially held. Then, at the timing when the pulse of the latch strobe signal LS is generated, the held digital video signal DV is converted into an analog voltage. The converted analog voltage is simultaneously applied to all the source bus lines SL1 to SLn as the driving video signals S(1) to S(n).
The backlight control unit 500 controls the luminance (light emission intensity) of the light source in the backlight device 600 based on the backlight control signal BS sent from the display control circuit 100.
As described above, the scanning signals G(1) to G(m) are applied to the respective gate bus lines GL1 to GLm, and the driving video signal driving video signals S(1) to S(n) are applied to the respective source bus lines SL1 to SLn, and the luminance of the light source in the backlight device 600 is controlled, whereby an image corresponding to the image signal DAT sent from the outside is displayed on the display unit 410.
Blue light is emitted from the blue LED element 6 (B), and green light is emitted from the green LED element 6 (G). Red light is emitted from the red phosphor 7 (R). The red phosphor 7 (R) is excited by light emitted from the blue LED element 6 (B) to emit light. That is, the red phosphor 7 (R) functions as a wavelength conversion element that converts the wavelength of blue light into the wavelength of red light. As described above, the first magenta light emitter 60 (M1) contains a relatively large amount of the red phosphor 7 (R), and the second magenta emitter 60 (M2) contains a relatively small amount of the red phosphor 7 (R). As described above, the first magenta light emitter 60 (M1) emits reddish magenta light, the second magenta emitter 60 (M2) emits bluish magenta light, and the green light emitter 60 (G) emits green light. Reddish magenta light, bluish magenta light, and green light are synthesized, and white light is irradiated to the liquid crystal panel 400.
The chromaticity of the first magenta light emitter 60 (M1), the second magenta emitter 60 (M2) and the green light emitter 60 (G) are different from each other. Depending on the color temperature to be displayed, deviations occur in their light emission intensities. From the foregoing, there is concern that color unevenness and luminance unevenness may occur depending on the arrangement of the light source. Therefore, the four light emitters 60 included in each group are arranged close to each other so as to suppress occurrence of color unevenness and luminance unevenness is preferable.
Next, the control of the light emission intensity of the light emitter 60 will be described.
As illustrated in
As described above, as illustrated in
Next, how color temperature is switched in this embodiment will be described. In the following description, an example will be described in which the color temperature is switched between 6500 K and 9300 K. As described above, in the present embodiment, the light emission intensity of the first magenta light emitter 60 (M1), the light emission intensity of the second magenta emitter 60 (M2), and the light emission intensity of the green light emitters 60 (G) are independently controlled by the backlight control unit 500. That is, the luminance of the three colors of reddish magenta, bluish magenta, and green are independently controlled. Therefore, on the xy chromaticity diagram, chromaticity coordinates within the range of a triangle 81 connecting the chromaticity coordinates (green chromaticity coordinates) G for the green light emitter 60, chromaticity coordinates (chromaticity coordinates of reddish magenta color) M1 for the first magenta light emitter 60 (M1), and chromaticity coordinates (bluish magenta chromaticity coordinates) M2 for the second magenta light emitter 60 (M2) can be selected as a white point (see
It is assumed that the light emitter 60 constituting the light source is selected so that chromaticity coordinates corresponding to the target color temperature are included within the range of the triangle 81. In the example illustrated in
When the light emission intensity of the first magenta light emitter 60 (M1) and the light emission intensity of the second magenta light emitter 60 (M2) are equalized, the light emission spectrum of the light emitted from the first magenta light emitter 60 (M1) is represented by a curve indicated by reference numeral 801 in
Under the above assumption, when setting the color temperature to 6500 K, the light emission intensity of the first magenta light emitter 60 (M1) is relatively strengthened and the light emission intensity of the second magenta light emitter 60 (M2) is relatively weakened. As a result, the light emission spectrum 801 of the light emitted from the first magenta light emitter 60 (M1) and the light emission spectrum 802 of the light emitted from the second magenta light emitter 60 (M2) are as illustrated in
When setting the color temperature to 9300 K, the light emission intensity of the first magenta light emitter 60 (M1) is relatively weakened and the light emission intensity of the second magenta emitter 60 (M2) is relatively strengthened. As a result, the light emission spectrum 801 of the light emitted from the first magenta light emitter 60 (M1) and the light emission spectrum 802 of the light emitted from the second magenta light emitter 60 (M2) are as illustrated in
Further, the light emission intensity of the green light emitter 60 (G) is adjusted so that the white point is located on the blackbody locus 8 on the xy chromaticity diagram. As described above, the color temperature is set to 9300 K.
In the present embodiment, the light source constituting the backlight device 600 is composed of:
a green light emitter 60 (G) having a green LED element 6 (G);
a first magenta light emitter 60 (M1) having a structure in which the blue LED element 6 (B) is covered with a relatively large amount of the red phosphor 7 (R); and
a second magenta light emitter 60 (M2) having a structure in which the blue LED element 6 (B) is covered with a relatively small amount of red phosphor 7 (R) (See
Two types of light emitters (the first magenta light emitter 60 (M1) and the second magenta light emitter (M2)) out of the above three types of light emitters 60 include the same type of LED element (LED chip) as the light emitting element and the same type of phosphor as the wavelength conversion element. In this regard, if two kinds of light emitters (two kinds of magenta light emitters) are configured by using two kinds of red phosphors having mutually different light emission wavelengths, that is, assuming two kinds of magenta light emitters are formed by a magenta light emitter having a light emission spectrum represented by a curve indicated by reference numeral 811 in
Further, in the present embodiment, the light source does not include a red LED element. As described above, since the red LED element has an output largely changing depending on the temperature, reliability is improved by adopting a configuration that does not use the red LED element.
As described above, according to the present embodiment, it is possible to realize a highly reliable backlight device capable of adjusting and changing the color temperature without lowering the color purity.
Further, according to the present embodiment, as described above, since the configuration without using the red LED element is adopted, the backlight device with low power consumption can be realized at low costs. This will be described below. Red LED elements are less efficient than blue LED elements. Therefore, power consumption is reduced by adopting a configuration that does not use a red LED element. In addition, white LEDs are often realized by using blue LED elements. For this reason, improvements have been made with respect to the blue LED element and mass production is being carried out, thereby lowering the unit price of the chip. Further, in the present embodiment, unlike the configuration illustrated in
Hereinafter, a modified example of the first embodiment will be described.
In the first embodiment, when the color temperature is set to 6500 K, the second magenta light emitter 60 (M2) is in a state close to the turned off state, and when the color temperature is set to 9300 K, the first magenta light emitter 60 (M1) is brought into a state close to the turned off state. When the state of the light emitter 60 close to the turned off state occurs in this way, luminance unevenness tends to occur on the screen. In this modified example (first modified example), the amount of the red phosphor 7 (R) included in each of the first magenta light emitter 60 (M1) and the second magenta light emitter 60 (M2) is adjusted so that the distance between the chromaticity coordinates M1 for the first magenta light emitter 60 (M1) and the chromaticity coordinates M2 of the second magenta light emitter 60 (M2) is longer than the distance in the first embodiment (see
In this modified example, when the light emission intensity of the first magenta light emitter 60 (M1) and the light emission intensity of the second magenta light emitter 60 (M2) are equalized, the light emission spectrum of the light emitted from the first magenta light emitter 60 (M1) is represented by a curve indicated by reference numeral 821 in
When setting the color temperature to 6500 K, the light emission intensity of the first magenta light emitter 60 (M1) and the light emission intensity of the second magenta light emitter 60 (M2) are controlled so that the light emission spectrum 821 of the light emitted from the first magenta color light emitter 60 (M1) and the emission spectrum 822 of the light emitted from the second magenta light emitter 60 (M2) are as illustrated in
When setting the color temperature to 9300 K, the light emission intensity of the first magenta light emitter 60 (M1) and the light emission intensity of the second magenta light emitter 60 (M2) are controlled so that the light emission spectrum 821 of the light emitted from the first magenta light emitter 60 (M1) and the emission spectrum 822 of the light emitted from the second magenta light emitter 60 (M2) are as illustrated in
As described above, in this modified example, even when the color temperature is set to either 6500 K or 9300 K, the first magenta light emitter 60 (M1) and the second magenta light emitter 60 (M2) are not in a state close to the turned off state. Therefore, occurrence of unevenness in luminance is suppressed. Further, on the xy chromaticity diagram, the range (see
The chromaticity coordinates of the light emitted from the first magenta light emitter 60 (M1) and the second magenta light emitter 60 (M2) varies according to the amount of the red phosphor 7 (R) included in each light emitter 60. Therefore, the range of the triangle connecting the chromaticity coordinates G for the green light emitter 60 (G), the chromaticity coordinates M1 for the first magenta light emitter 60 (M1) and the chromaticity coordinates for the second magenta light emitter 60 (M2) varies depending on the amount of red phosphor 7 (R) contained in each of the first magenta light emitter 60 (M1) and the second magenta light emitter 60 (M2). For example, the amount of the red phosphor 7 (R) included in the two kinds of the first type light emitters (the first magenta light emitter 60 (M1) and the second magenta light emitter 60 (M2)) is adjusted so that the chromaticity coordinates on the blackbody locus 8 corresponding to the color temperature in the range of 4000 K to 14000 K is included within the range of the triangle connecting the chromaticity coordinates of the light emitted from each of the three kinds of light emitters 60 described above. By performing such adjustment, the displayable color temperature range is 4000 K to 14000 K.
In the first embodiment, the light source on the LED substrate 62 is arranged as illustrated in
However, according to the configuration illustrated in
In the first embodiment, as illustrated in
The first cyan light emitter 60 (C1) emits a greenish cyan light, the second cyan light emitter 60 (C2) emits a bluish cyan light, and the red light emitter 60 (R) emits a red light. As a result of the greenish cyan light, the bluish cyan light, and the red light combining, the liquid crystal panel 400 is irradiated with white light.
In the present modified example, the light emission intensity of the first cyan light emitter 60 (C1), the light emission intensity of the second cyan light emitter 60 (C2), and the light emission intensity of the red light emitter 60 (R) are independently controlled by the backlight control unit 500. That is, the luminance of the three colors of greenish cyan, bluish cyan and red is controlled independently. Therefore, on the xy chromaticity diagram, the chromaticity coordinates within the range of the triangle 85 connecting the chromaticity coordinates (red chromaticity coordinates) R for the red light emitter 60 (R), the chromaticity coordinates (chromaticity coordinates of greenish cyan) C1 for the first cyan light emitter 60 (C1), and the chromaticity coordinates (chromaticity coordinates of bluish cyan) C2 for the second cyan light emitter 60 (C2) can be selected as a white point (see
The first yellow light emitter 60 (Y1) emits reddish yellow light, the second yellow light emitter 60 (Y2) emits greenish yellow light, and the blue light emitter 60 (B) emits blue light. Reddish yellow light, greenish yellow light, and blue light are combined, and white light is irradiated on the liquid crystal panel 400.
In this modified example, the light emission intensity of the first yellow light emitter 60 (Y1), the light emission intensity of the second yellow light emitter 60 (Y2), and the light emission intensity of the blue light emitter 60 (B) are independently controlled by the backlight control unit 500. That is, the luminance of the three colors of reddish yellow, greenish yellow, and blue are independently controlled. Accordingly, on the xy chromaticity diagram, the chromaticity coordinates within the range of the triangle 86 connecting the chromaticity coordinates (blue chromaticity coordinates) B for the blue light emitter 60 (B), chromaticity coordinates (reddish yellow chromaticity coordinates) Y1 for the first yellow light emitter 60 (Y1) and chromaticity coordinates (greenish yellow chromaticity coordinates) Y2 for the second yellow light emitter 60 (Y2) can be selected as a white point (see
As described above, also in this modified example, it is possible to adjust and change the color temperature.
A second embodiment of the present invention will be described. The overall configuration (see
a first white light emitter 60 (W1) having a structure in which the blue LED element 6 (B) is covered with a relatively large amount of the red phosphor 7 (R) and a relatively small amount of the green phosphor 7 (G);
a second white light emitter 60 (W2) having a structure in which the blue LED element 6 (B) is covered with a relatively small amount of the red phosphor 7 (R) and a relatively large amount of the green phosphor 7 (G); and
a third white light emitter 60 (W3) having a structure in which the blue LED element 6 (B) is covered with a relatively small amount of the red phosphor 7 (R) and a relatively small amount of the green phosphor 7 (G). The first white light emitter 60 (W1), the second white light emitter 60 (W2), and the third white light emitter 60 (W3) are first type light emitters. As described above, in the present embodiment, the light source is composed of three kinds of first type light emitters.
Blue light is emitted from the blue LED element 6 (B). Red light is emitted from the red phosphor 7 (R), and green light is emitted from the green phosphor 7 (G). The red phosphor 7 (R) and the green phosphor 7 (G) are excited by light emitted from the blue LED element 6 (B) to emit light. That is, the red phosphor 7 (R) functions as a wavelength conversion element that converts the wavelength of blue light into the wavelength of red light and the green phosphor 7 (G) functions as a wavelength conversion element that converts the wavelength of blue light into the wavelength of green light.
Since the first white light emitter 60 (W1) contains a relatively large amount of red phosphor 7 (R), the first white light emitter 60 (W1) emits reddish white light. Since the second white light emitter 60 (W2) contains a relatively large amount of the green phosphor 7 (G), the second white light emitter 60 (W2) emits greenish white light. Since the third white light emitter 60 (W3) contains a relatively small amount of red phosphor 7 (R) and a relatively small amount of green phosphor 7 (G), the third white light emitter 60 (W3) emits bluish white light. Reddish white light, greenish white light, and bluish white light are combined, and white light is irradiated on the liquid crystal panel 400.
The arrangement of the light sources on the LED substrate 62 can be similar to the first embodiment (see
Also in the present embodiment as in the first embodiment, the light emission intensity of the light emitter 60 on the LED substrate 62 is adjusted for each kind. That is, the light emission intensity of the first white light emitter 60 (W1), the light emission intensity of the second white light emitter 60 (W2), and the light emission intensity of the third white light emitter 60 (W3) are independently controlled by the backlight control unit 500.
As described above, the luminance of the reddish white is controlled by controlling the light emission intensity of the first white light emitter 60 (W1), the luminance of greenish white is controlled by controlling the light emission intensity of the second white light emitter 60 (W2), and the luminance of bluish white is controlled by controlling the light emission intensity of the third white light emitter 60 (W3). As a result, white adjustment (adjustment and change of color temperature) is performed.
Next, how color temperature is switched in this embodiment will be described. Here too, an example in which the color temperature is switched between 6500 K and 9300 K will be described. In the present embodiment, the light emission intensity of the first white light emitter 60 (W1), the light emission intensity of the second white light emitter 60 (W2), and the light emission intensity of the third white light emitter 60 (W3) are independently controlled by the backlight control unit 500. That is, the luminance of the three colors of reddish white, greenish white, and bluish white are independently controlled. Accordingly, on the xy chromaticity diagram, chromaticity coordinates within the range of the triangle 83 connecting the chromaticity coordinates (chromaticity coordinates of reddish white) W1 for the first white light emitter 60 (W1), the chromaticity coordinates (chromaticity coordinate of greenish white) W2 for the second white light emitter 60 (W2) and the chromaticity coordinates (bluish white chromaticity coordinates) W3 for the third white light emitter 60 (W3) can be selected as a white point (see
When the light emission intensities of the first white light emitter 60 (W1), the second white light emitter 60 (W2), and the third white light emitter 60 (W3) are equalized, the light emission spectrum of the light emitted from the first white light emitter 60 (W1) is represented by a curve indicated by reference numeral 831 in
Under the above assumption, when setting the color temperature to 6500 K, the light emission intensity of the first white light emitter 60 (W1) is relatively increased, and the light emission intensity of the third white light emitter 60 (W3) relatively weakened. In addition, the light emission intensity of the second white light emitter 60 (W2) is adjusted so that the white point is located on the blackbody locus 8 on the xy chromaticity diagram. Thus, the light emission spectrum 831 of the light emitted from the first white light emitter 60 (W1), the light emission spectrum 832 of the light emitted from the second white light emitter 60 (W2), and the light emission spectrum 833 of the light emitted from the third white light emitter 60 (W3) is as illustrated in
When setting the color temperature to 9300 K, the light emission intensity of the first white light emitter 60 (W1) is relatively weakened and the light emission intensity of the third white light emitter 60 (W3) is relatively strengthened. In addition, the light emission intensity of the second white light emitter 60 (W2) is adjusted so that the white point is located on the blackbody locus 8 on the xy chromaticity diagram. Thus, the light emission spectrum 831 of the light emitted from the first white light emitter 60 (W1), the light emission spectrum 832 of the light emitted from the second white light emitter 60 (W2), and the light emission spectrum 833 of the light emitted from the third white light emitter 60 (W3) is as illustrated in
In the present embodiment, the light source constituting the backlight device 600 is composed of:
a first white light emitter 60 (W1) having a structure in which the blue LED element 6 (B) is covered with a relatively large amount of the red phosphor 7 (R) and a relatively small amount of the green phosphor 7 (G);
a second white light emitter 60 (W2) having a structure in which the blue LED element 6 (B) is covered with a relatively small amount of the red phosphor 7 (R) and a relatively large amount of the green phosphor 7 (G); and
a third white light emitter 60 (W3) having a structure in which the blue LED element 6 (B) is covered with a relatively small amount of the red phosphor 7 (R) and a relatively small amount of the green phosphor 7 (G) (see
In this manner, the light source is composed of three kinds of light emitters 60. In addition, the three kinds of light emitters 60 are configured so that the light emission intensities are independently controlled. As a result, since the luminance of light of three colors can be independently controlled, it is possible to adjust and change the color temperature. The three kinds of light emitters 60 include LED elements (LED chips) of the same kind as light emitting elements, and also contain phosphors of the same kind as wavelength conversion elements. Therefore, regardless of how the light emission intensities of the three kinds of light emitters 60 are controlled, the dominant wavelength of the combined light is not changed, and the half-value width of the combined light is maintained at a relatively narrow width. Therefore, even when the color temperature is adjusted or changed, the color purity does not decrease. Also, as in the first embodiment, the light source does not include a red LED element. As described above, according to the present embodiment, as in the first embodiment, realization of a highly reliable backlight device capable of adjusting and changing the color temperature without lowering the color purity is realized. Further, like the first embodiment, effects of lower power consumption and lower costs can be obtained.
A third embodiment of the present invention will be described. The overall configuration (see
The first white light emitter 60 (Wa) and the second white light emitter 60 (Wb) are first type light emitters. As described above, in the present embodiment, the light source is composed of two types of first type light emitters.
Blue light is emitted from the blue LED element 6 (B). Yellow light is emitted from the yellow phosphor 7 (Y). Note, the yellow phosphor 7 (Y) is excited by light emitted from the blue LED element 6 (B) and emits light. That is, the yellow phosphor 7 (Y) functions as a wavelength conversion element that converts the wavelength of blue light into the wavelength of yellow light. YAG (Yttirum Aluminum Garnet) phosphor can be used as the yellow phosphor 7 (Y), for example.
Since the first white light emitter 60 (Wa) contains a relatively large amount of the yellow phosphor 7 (Y), the first white light emitter 60 (Wa) emits yellowish white light. Since the second white light emitter 60 (Wb) contains a relatively small amount of the yellow phosphor 7 (Y), the second white light emitter 60 (Wb) emits bluish white light. As a result of combining yellowish white light and bluish white light, white light is irradiated on the liquid crystal panel 400.
Moreover, similar to the first embodiment, in the present embodiment, the light emission intensity of the light emitter 60 on the LED substrate 62 is adjusted for each kind. That is, the light emission intensity of the first white light emitter 60 (Wa) and the light emission intensity of the second white light emitter 60 (Wb) are independently controlled by the backlight controller 500.
From the above, by controlling the light emission intensity of the first white light emitter 60 (Wa), the luminance of yellowish white is controlled, and by controlling the light emission intensity of the second white light emitter 60 (Wb), the luminance of bluish white is controlled. As a result, white adjustment (adjustment and change of color temperature) is performed.
Next, how color temperature is switched in this embodiment will be described. Here too, an example in which the color temperature is switched between 6500 K and 9300 K will be described. In the present embodiment, the light emission intensity of the first white light emitter 60 (Wa) and the emission intensity of the second white light emitter 60 (Wb) are independently controlled by the backlight controller 500. That is, the luminance of the two colors of yellowish white and bluish white is independently controlled. Accordingly, on the xy chromaticity diagram, chromaticity coordinates on a line segment 84 connecting chromaticity coordinates (chromaticity coordinates of yellowish white) Wa for the first white light emitter 60 (Wa) and chromaticity coordinates (bluish white chromaticity coordinates) Wb for the second white light emitter 60 (Wb) are set as a white point (see
When the light emission intensity of the first white light emitter 60 (Wa) and the light emission intensity of the second white light emitter 60 (Wb) are equalized, the light emission spectrum of the light emitted from the first white light emitter 60 (Wa) is represented by a curve indicated by reference numeral 841 in
Under the above assumption, when setting the color temperature to 6500 K, the light emission intensity of the first white light emitter 60 (Wa) is relatively strengthened, and the light emission intensity of the second white light emitter 60 (Wb) is relatively weakened. As a result, the light emission spectrum 841 of the light emitted from the first white light emitter 60 (Wa) and the light emission spectrum 842 of the light emitted from the second white light emitter 60 (Wb) are as illustrated in
When setting the color temperature to 9300 K, the light emission intensity of the first white light emitter 60 (Wa) is relatively weakened and the light emission intensity of the second white light emitter 60 (Wb) is relatively strengthened. As a result, the light emission spectrum 841 of the light emitted from the first white light emitter 60 (Wa) and the light emission spectrum 842 of the light emitted from the second white light emitter 60 (Wb) are as illustrated in
In the present embodiment, the light source constituting the backlight device 600 includes a first white light emitter 60 (Wa) having a structure in which the blue LED element 6 (B) is covered with a relatively large amount of the yellow phosphor 7 (Y) and a second white light emitter 60 (Wb) having a structure in which the blue LED element 6 (B) is covered with a relatively small amount of the yellow phosphor 7 (Y) (see
Hereinafter, a modified example of the third embodiment will be described.
In the third embodiment, the light source on the LED substrate 62 is arranged as illustrated in
In the third embodiment, as illustrated in
Blue light is emitted from the blue LED element 6 (B). Red light is emitted from the red phosphor 7 (R), and green light is emitted from the green phosphor 7 (G). The red phosphor 7 (R) and the green phosphor 7 (G) are excited by light emitted from the blue LED element 6 (B) to emit light. That is, the red phosphor 7 (R) functions as a wavelength conversion element that converts the wavelength of blue light into the wavelength of red light and the green phosphor 7 (G) functions as a wavelength conversion element that converts the wavelength of blue light into the wavelength of green light.
Since the first white light emitter 60 (Wa) contains a relatively large amount of the red phosphor 7 (R) and a relatively large amount of the green phosphor 7 (G), the first white light emitter 60 (Wa) emits a yellowish white light. Since the second white light emitter 60 (Wb) contains a relatively small amount of the red phosphor 7 (R) and a relatively small amount of the green phosphor 7 (G), the second white light emitter 60 (Wb) emits a bluish white light. As a result of combining yellowish white light and bluish white light, white light is irradiated on the liquid crystal panel 400.
Next, how color temperature is switched in this modified example will be described. Here too, an example in which the color temperature is switched between 6500 K and 9300 K will be described. Also in this modified example, the light emission intensity of the first white light emitter 60 (Wa) and the light emission intensity of the second white light emitter 60 (Wb) are independently controlled by the backlight controller 500. That is, the luminance of the two colors of yellowish white and bluish white is independently controlled. Accordingly, on the xy chromaticity diagram, chromaticity coordinates on the line segment 87 connecting chromaticity coordinates (chromaticity coordinates of yellowish white) Wa for the first white light emitter 60 (Wa) and chromaticity coordinates (bluish white chromaticity coordinates) Wb for the second white light emitter 60 (Wb) can be selected as a white point (see
When setting the color temperature to 6500 K, the light emission intensity of the first white light emitter 60 (Wa) is relatively strengthened and the light emission intensity of the second white light emitter 60 (Wb) is relatively weakened. On the other hand, when setting the color temperature to 9300 K, the light emission intensity of the first white light emitter 60 (Wa) is relatively weakened and the light emission intensity of the second white light emitter 60 (Wb) is relatively strengthened. In this way, color temperature is adjusted and changed in the same manner as in the third embodiment.
In the third embodiment, one type of phosphor (yellow phosphor 7 (Y)) is contained in the first white light emitter 60 (Wa) and the second white light emitter 60 (Wb). On the other hand, in this modified example, two kinds of phosphors (a red phosphor 7 (R) and a green phosphor 7 (G) are included in the first white light emitter 60 (Wa) and the second white light emitter 60 (Wb). Therefore, by adjusting the amounts of the two kinds of phosphors, the chromaticity coordinates Wa, Wb of each of the first white light emitter 60 (Wa) and the second white light emitter 60 (Wb) can be precisely controlled. That is, the chromaticity of the light emitted from each of the first white light emitter 60 (Wa) and the second white light emitter 60 (Wb) can be more precisely controlled. Therefore, as compared with the third embodiment, it is possible to more precisely adjust and change the color temperature.
In each of the above embodiments and modified examples, examples in which an LED element (light emitting diode element) is used as a light emitting element in the light emitting body 60 have been described, but the present invention is not limited thereto. A laser diode element can also be used as the light emitting element. For example, in the configuration of the first embodiment, a laser diode element emitting blue light may be used instead of the blue LED element 6 (B).
In each of the above embodiments and modified examples, examples in which a phosphor is used as a wavelength conversion element in the light emitter 60 have been described, but the present invention is not limited thereto. Quantum dots can also be used as wavelength conversion elements. For example, in the configuration of the first embodiment, a quantum dot that converts a part of the light emitted from the blue LED element 6 (B) to the red spectrum may be used instead of the red phosphor 7 (R).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-105128 | May 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/062070 | 4/15/2016 | WO | 00 |
