JP3935045B2 - Lighting device, backlight device, liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lighting device, a backlight device using the lighting device, and a liquid crystal display device using the backlight device.
[0002]
[Prior art]
As a technique for improving the color reproducibility of the image of the liquid crystal display device, as shown in FIG. 9, the fluorescent lamp unit 112 and each color of red R111-R, green G111-G, and blue B111-B are made into one set. A technique is disclosed in which two types of light source units of a plurality of LED lamp units 111 are arranged on both side surfaces (both end surfaces) 115a and 115b of a light guide 115 and chromaticity adjustment is performed using a color mixture light guide (for example, Patent Document 1).
[0003]
Further, in Japanese Patent Laid-Open No. 4-362919, as shown in FIG. 10, a plurality of types of color filters having different spectral characteristics, for example, red R, green G, and blue B, are arranged to face each color filter. A technique for improving color reproducibility by changing the thicknesses dR, dG, and dB of the liquid crystal layer 101 sandwiched between two glass plates 100a and 100b is disclosed (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP 2001-135118 A [Patent Document 2]
JP-A-4-362919
[Problems to be solved by the invention]
However, in the technique described in Patent Document 1, the chromaticity correction is performed by increasing the drive current value to be supplied to the LED of the color to be corrected out of the R, G, and B LEDs than the current value of the other color LED. The duty of the drive pulse is increased, but complicated control of the drive circuit is required for each color or chromaticity, and the light of the three colors of LED and the light of the fluorescent lamp are efficiently mixed. Therefore, there is a problem that the dimming control means becomes complicated, for example, the prism sheet has a special cross section (sawtooth shape).
[0006]
Moreover, even if the technique described in Patent Document 2 is used, there is a problem in that a large effect regarding improvement in color reproducibility cannot be obtained. This is because no measures are taken regarding the color purity of the light source itself. In order to improve color reproducibility, it is first necessary to improve the color purity of the light source, which is an essential problem.
[0007]
An object of the present invention is to improve color reproducibility on a screen of a backlight device using the illumination device and a liquid crystal display device using the backlight device by improving the color purity of the illumination device itself.
[0008]
[Means for Solving the Invention]
According to one aspect of the present invention, there is provided a lighting device including a first light source and a second light source having a spectral characteristic different from the spectral characteristic of the first light source, wherein the spectral characteristic of the first light source is The second light source has a maximum wavelength of emission intensity of 1 or 2 in the visible light wavelength range, and has a maximum wavelength of emission intensity of 1 or 2 in the visible light wavelength range; There is provided an illuminating device characterized in that the 1 or 2 maximum wavelength of the spectral characteristic of the light source and the 1 or 2 maximum wavelength of the spectral characteristic of the first light source are substantially the same. The first light source and the second light source are light sources having different driving methods, for example.
[0009]
According to the illuminating device, one or two maximum wavelength wavelengths selected from the maximum wavelength wavelengths of the spectral characteristics of the second light source and the maximum wavelength wavelengths of the spectral characteristics of the first light source are selected. By making the 1 or 2 maximum wavelength to be substantially the same wavelength, the color purity at the maximum wavelength common to both light sources can be increased.
[0010]
According to another aspect of the present invention, there is provided an illumination device including a first light source and a second light source having a spectral characteristic different from the spectral characteristic of the first light source, wherein the spectral characteristic of the first light source is And having a maximum wavelength of at least two in the visible light wavelength range, the spectral characteristics of the second light source have at least one maximum wavelength in the visible light wavelength range, and the spectral characteristics of the second light source are There is provided an illuminating device characterized in that a maximum wavelength that the maximum wavelength has and a maximum wavelength that the spectral characteristics of the first light source have differ.
[0011]
In the illuminating device, the color purity in a plurality of main wavelength ranges can be increased as a whole by using a light source having spectral characteristics with high color purity at each maximum wavelength.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In order to improve the color purity of the light source for the illumination device, the following two requirements (1) and (2) must be satisfied. (1) The light source is a light emitter whose primary colors are three wavelengths of red, blue and green. (2) The spectral distribution of each color is monodisperse. Further, as another requirement for improving color reproducibility, it is preferable to design red as a long wavelength and blue as a short wavelength among the above three wavelengths within the range of the visible light region. When red is designed to have a long wavelength, the brightness is lowered and the luminous efficiency of the light source is lowered. However, this is indispensable from the viewpoint of faithfully reproducing red.
[0013]
The inventor considered that a light source of a preferable illumination device can be obtained by using a plurality of types of light sources having different emission wavelengths and appropriately designing in consideration of the emission wavelengths of the plurality of types of light sources. The plural types of light sources are, for example, two types of light sources having different driving methods (hereinafter referred to as “first type light source (first light source) and second type light source (second light source)”), and will be described below. We thought about designing the light source of the lighting device based on this idea. In the following description, for the sake of simplicity, a method for increasing the color purity of red will be described as an example. However, the same idea can be applied to increase the color purity of other colors, for example, blue or green. Needless to say.
[0014]
First, the concept regarding the selection of the light source will be described. The first type light source may be a fluorescent tube with high power efficiency. On the other hand, as the second type light source, an LED (Light Emitting Diode), an organic EL (Electro-Luminescence), or the like may be used. The first type light source includes a phosphor having two colors including at least blue and green among red, blue, and green constituting the three primary colors of light. On the other hand, the second type light source has a red light emitting element.
[0015]
The reason why the fluorescent tube is not included in the second type light source is that power use efficiency is taken into consideration. In other words, when a fluorescent tube is used as a red auxiliary light source, it cannot function as an original auxiliary light source unless it is a fluorescent tube into which a red phosphor is introduced. However, a fluorescent tube incorporating a red phosphor originally emits only red monochromatic light with power equivalent to the power of emitting the three color phosphors together, which has a disadvantage in terms of power. large. As long as the second type light source has one target color whose purity is to be increased, a monochromatic light emitter such as an LED may be used, and this is more rational in terms of power. The inventor proposes the following new technology as a technology for improving the red color purity of the lighting device.
[0016]
(1) When a light source that emits at least red light is used as the first type light source, the red maximum wavelength of the spectral characteristics of each of the first type light source and the second type light source is made closer (set to the same value). Alternatively, (2) when a light source that does not emit red light (the spectral characteristic does not have a red maximum wavelength) is used as the first type light source, the second type light source emits red light (the spectral characteristic has a red maximum value). Use a light source (having a wavelength).
[0017]
The intent of (1) is to improve the color purity of red by bringing the maximum wavelength of red in the spectral characteristics of the first-type light source and the second-type light source closer. Thereby, red color purity can be raised as the whole illuminating device. The intent of (2) is to add a second type light source having a spectral characteristic of red to a first type light source having a spectral characteristic that does not have a red maximum wavelength, thereby improving the red color purity of the entire lighting device. It is to improve. The above concept will be described more specifically with reference to the drawings.
[0018]
FIG. 1 is a diagram showing an example of the spectral distribution (wavelength dependence of emission intensity) of the entire backlight in the case of (1). As shown in FIG. 1, the spectral distribution characteristics of the entire backlight mainly have a blue maximum wavelength λb, a green maximum wavelength λg, and a red maximum wavelength λr in the visible light wavelength range. Here, with respect to the red wavelength, the maximum wavelength λr1 and λr2 of the red spectrum characteristic (solid line) P3 by the fluorescent tube and the red spectrum characteristic (dashed line) P4 by the LED are preferably the same so as to approach each other. Set. In this way, by setting the both maximum wavelengths to be substantially the same, even if the red spectrum (solid line) P3 due to the fluorescent tube and the red spectrum (dashed line) due to the LED are mixed, the color purity of the entire lighting device can be improved. A high lighting device can be designed.
[0019]
Here, the fluorescent tube and the LED may not necessarily match the red maximum wavelength in the spectral characteristics of the two light sources due to the difference in the material, etc. By designing the lighting device based on this, a desired effect can be expected. That is, as shown in FIG. 2, the half width of the red spectrum characteristic (solid line) P5 by the fluorescent tube (the wavelength width corresponding to ½ of the maximum value is indicated by the region A) and the red spectrum by the LED. Each of the spectral characteristics of the fluorescent tube and the LED has a half width of the characteristic (broken line) P6 (a wavelength width corresponding to half the maximum emission intensity is indicated by a region B) overlapping each other. Sets the maximum wavelength.
[0020]
As described above, the red maximum spectral wavelength of the spectral characteristics of the two light sources is adjusted so that the half-value widths of the red spectral characteristics of the light sources overlap each other, whereby the red spectral characteristics (thick solid line) P7 in the entire lighting device. It is possible to suppress a decrease in color purity. Therefore, in the illumination device of the present invention, the red maximum wavelength of the spectral characteristics of both light sources may be “substantially the same” in the range where the half-value widths of the red spectral characteristics of the light sources overlap each other as described above.
[0021]
The definition of the “maximum wavelength” may be defined as a so-called peak wavelength, or may be defined as a dominant wavelength in consideration of the relative luminous sensitivity to red of the human eye.
[0022]
With respect to the above (2), the red phosphor is excluded from the first type light source fluorescent tube, and only the blue spectrum characteristic P1 and the green spectrum characteristic P2 are obtained (as shown in FIG. 3). A fluorescent tube with spectral characteristics is not used. Instead, an LED having a spectral characteristic (having a red maximum wavelength λr2) having a red spectral characteristic P8 (similar to the red spectral characteristic P4 (FIG. 1) and P6 (FIG. 2)) may be used as the second type light source. Use.
[0023]
When red light emission is excluded in the first type light source, unnecessary light emission in a wavelength region corresponding to yellow to orange light incidentally emitted by the red phosphor of the fluorescent tube can be excluded. Then, instead of eliminating the red phosphor in the fluorescent tube, red color is improved in the illumination device by emitting red light with the second type light source.
[0024]
More specifically, as shown in FIG. 3, the spectral distribution in the illuminating device is formed by a color mixture of the light emission spectrum component by the fluorescent tube and the light emission spectrum component by the LED, and yellow due to the red light emitter of the fluorescent tube. By eliminating unnecessary light emission in the orange wavelength region, it is possible to increase the red color purity of the entire lighting device. Needless to say, the number of light sources used is not limited to a single first-type light source, but a plurality of first-type light sources may be used in order to obtain a desired brightness.
[0025]
Next, the driving circuit for each light source will be described. It is preferable that the driving circuit is provided independently for the first-type light source and the second-type light source. It can also be assigned for each number of light sources used. FIG. 4A is a diagram illustrating an example of a circuit diagram of a fluorescent tube driving circuit. FIG. 4B is a circuit diagram illustrating an example of an LED lighting circuit. When the first-type light source is a fluorescent tube, a self-excited or separately-excited inverter circuit can be used. As shown in FIG. 4A, a transformer 3A is used to apply a high AC voltage (several hundreds to thousands of volts) to the fluorescent tube 1 that is a first type light source. The fluorescent tube is turned on by converting a DC input voltage of about 10 V to an AC voltage of about several thousand volts.
[0026]
When the second type light source is the LED 2, a normal LED lighting circuit (constant current circuit) or the like can be used. As shown in FIG. 4B, the LED lighting circuit generally has a configuration in which a resistor 3B is connected in series for each LED element. The resistor 3B is connected to the LED 2 in series. When a power supply voltage Vin (DC) such as a battery (DC voltage is 5 V or more) is directly applied to the LED 2, an excessive current flows through the LED 2 and the LED 2 is destroyed. Because. Therefore, the resistor 3B is inserted between the LED 2 and the power source VinDC to make it difficult for the current to flow, and the destruction of the LED 2 is prevented. Note that the resistance value of the resistor 3B used in the circuit shown in FIG. 4B is set based on the design current value flowing through the LED 2 and various rated values of the resistor 3B.
[0027]
The input voltage lines of the circuits in FIGS. 4A and 4B are provided individually. Since the input voltages required for various light sources differ depending on the rating, it is difficult to make both voltages common, but it is difficult to reduce the supply voltage to the LED drive circuit using a common power supply and a regulator etc. Is possible. Although it depends on the length of the fluorescent tube, the inverter circuit for the fluorescent tube is set to an input voltage of about 8V to several tens of volts, and the lighting circuit for the LED is a value up to about 5V at the maximum specified by the rating of the LED. Set to.
[0028]
The dimming control means is used to control these drive circuits, and can adjust the brightness of at least one of the first-type light source and the second-type light source. As the dimming control means, either a voltage (current) dimming method or a duty dimming method in which brightness is time-divided may be used. In addition, when the illuminating device which can respond to the high-speed response suitable for a moving image display is required, it is preferable to use the latter duty light control system.
[0029]
Next, a lighting device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 5 is a block diagram illustrating a configuration example of a lighting device using a voltage (current) dimming method. As shown in FIG. 5, the lighting device A includes a fluorescent tube 1, an LED 2, an inverter circuit 3, an LED lighting circuit 4, a dimming control means 5, and a power supply circuit 6 as main components. In the voltage (current) dimming type lighting apparatus configured as described above, the dimming control means 5 changes the input voltage or input current from the power supply circuit 6 with a DC-DC converter or the like and drives it. Dimming is performed by changing the currents of the fluorescent tube 1 and the LED 2 directly connected as loads of the inverter circuit 3 and the LED lighting circuit 4 according to the magnitude of the voltage (current).
[0030]
FIG. 6 is a block diagram illustrating a configuration example of a lighting device using a duty dimming method. As shown in FIG. 6, the lighting device B includes a fluorescent tube 11, an LED 12, an inverter circuit 13, an LED lighting circuit 14, a dimming control unit 15, and a power supply circuit 16 as main components. In the duty dimming type lighting device configured as described above, the dimming control means 15 creates two types of dimming pulses (PWM signals) for driving the inverter circuit 13 and the LED lighting circuit 14, and The brightness of the fluorescent tube 11 and the LED 12 is dimmed by changing the pulse width so as to have a duty ratio according to the PWM ratio setting data.
[0031]
When the lighting device A or B shown in FIG. 5 or 6 is used as a backlight device for a liquid crystal display device, for example, in addition to the lighting device A or B, the light distribution characteristics and the illumination light of the lighting device A or B and As an optical member having luminance distribution characteristics, an optical member including a reflection sheet or a reflection plate, a diffusion plate or a light guide plate, a diffusion sheet, a prism sheet, and a reflection polarizing plate is appropriately disposed on the casing. To do. Further, when used as a liquid crystal display device, a liquid crystal panel for displaying an image is arranged on the backlight device.
[0032]
An example of the backlight device according to this embodiment will be described with reference to FIGS.
A first embodiment will be described with reference to FIG. 7A and 7B are a front view and a side view showing a configuration example of the liquid crystal display device according to this embodiment. As shown in FIGS. 7A and 7B, the liquid crystal display device C according to this embodiment includes a fluorescent tube 31, an LED 32, an inverter circuit 33, an LED lighting circuit 34, a dimming control means 35, The power supply circuit unit 36, various optical members 37, a casing 38, and a liquid crystal panel 39 are included. Note that various electric circuit components indicated by reference numerals 33 to 36 are configured to be collectively arranged on the back surface of the lighting device, but the detailed positional relationship is not particularly limited.
[0033]
However, the power supply circuit unit 36 may be built in the housing 38 of the liquid crystal display device C. In the present embodiment, a plurality of fluorescent tubes 31 and LEDs 32 can be used. The inverter circuit 33, the LED lighting circuit 34, and the dimming control means 35 may be provided in accordance with the number of light sources. The various optical members 37 mainly include a reflection sheet or reflection plate 37A, a diffusion plate 37C, a diffusion sheet 37D, a prism sheet 37E, and a reflective polarizing sheet 37F. The backlight system is a so-called direct type backlight system.
[0034]
In this embodiment, a plurality of LEDs 32 are arranged between adjacent fluorescent tubes 31 in the direction in which the fluorescent tubes 31 extend. However, the spectral distribution of the entire backlight is determined by the positions of the fluorescent tubes 31 and the LEDs 32. The arrangement method is not limited to the above method because it is not greatly affected by the relationship. However, in order to make the in-plane distribution of the emission characteristics as uniform as possible, it is preferable to arrange the fluorescent tubes 31 and the LEDs 32 as evenly as possible. With a simple arrangement as shown in FIG. 7, a liquid crystal display device with high color purity can be designed.
[0035]
Next, Example 2 will be described with reference to FIG. FIG. 8 is a diagram illustrating a configuration of a backlight device using a light guide plate method (also referred to as an edge light method or a side light method) as a backlight method. As shown in FIG. 8, the backlight device D according to this embodiment includes a fluorescent tube 51, an LED 52, an inverter circuit, an LED lighting circuit, a dimming control means, a power supply circuit section (not shown), and various optical members. 57 and a housing 58. The various optical members 57 mainly include a reflection sheet or reflection plate 57A, a light guide plate 57B, a diffusion sheet 57D, a prism sheet 57E, and a reflection polarizing sheet 57F.
[0036]
The liquid crystal panel is not shown, but is mounted on the surface side of the reflective polarizing sheet 57F, for example. The number of various members may be the same as in the first embodiment. A light source including the fluorescent tube 51 and the LED 52 is disposed on the end face of the light guide plate 57B, and light introduced from the light source to the light guide plate 57B travels toward the surface direction (upward in the drawing) of the light guide plate 57B. In the illumination device according to the present embodiment, the LEDs 52 are arranged in the vicinity of the fluorescent tube 51 and at equal intervals along the direction in which the fluorescent tube 51 extends.
[0037]
However, since the spectral distribution of the entire backlight does not vary greatly depending on the arrangement method of the fluorescent tube 51 and the LED 52, the arrangement of the LED 52 can be arranged at a position that seems to be optimal from various viewpoints. In addition, since the light guide plate method does not take much space as compared with the direct type, it is mounted at a position where the fluorescent tube 51 and the light guide plate 57B are not arranged, or along the fluorescent tube 51 as shown in the figure. A method of arranging in the vicinity (parallel) is preferable.
[0038]
As described above, when the illumination device according to the present embodiment is used, an LED that emits a color whose color reproducibility is to be emphasized is provided in the vicinity of the fluorescent tube, the emission maximum wavelength is appropriately set, and a predetermined value is set. The color purity of the backlight device can be increased with a very simple configuration of driving with a current value. Furthermore, the color reproducibility can be effectively improved by designing the peak wavelength or dominant wavelength of the red light emission color on the longer wavelength side.
[0039]
That is, in the illumination device according to the present embodiment, unlike the above-described conventional technique, the light emission amounts of the R, G, and B LED lamps are not complicatedly controlled, and the liquid crystal layer of the liquid crystal panel itself is used. The color reproducibility can be improved with a very simple configuration without changing the thickness or having a special configuration of the color filter, the reflection sheet, or the dimming control means.
[0040]
In the above-described embodiment, the red color purity is improved. Needless to say, a desired color reproducibility can be obtained on the chromaticity diagram for blue and green as well. Alternatively, a light source having a spectral characteristic of a complementary color system may be used instead of the primary color system. The same applies to wavelength ranges other than the three colors.
[0041]
As mentioned above, although demonstrated along this Embodiment, it cannot be overemphasized that this invention is not limited to these examples, and various deformation | transformation are possible. The lighting device according to this embodiment can be applied to various electronic devices including a liquid crystal television, a liquid crystal monitor of a digital still camera and a digital video camera, a notebook personal computer including a liquid crystal display device, a mobile phone, and the like.
[0042]
【The invention's effect】
According to the illumination device of the present invention, by appropriately setting the maximum wavelength in each of the spectral characteristics of the two types of light sources, the color purity of the illumination device as a whole is improved, and color reproducibility is achieved with an extremely simple configuration. It becomes possible to improve.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first example of a spectral distribution of an illumination device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a second example of the spectral distribution of the illumination device according to the embodiment of the present invention.
FIG. 3 is a diagram showing a third example of the spectral distribution of the illumination device according to the embodiment of the present invention.
4A and 4B are examples of lighting circuits for various light sources in the lighting device according to the embodiment of the present invention, FIG. 4A is an example of a fluorescent tube, and FIG. 4B is an example of an LED lighting circuit.
FIG. 5 is a functional block diagram illustrating a configuration example of a lighting device using a voltage dimming method according to an embodiment of the present invention.
FIG. 6 is a functional block diagram illustrating a configuration example of a lighting device using a duty dimming method according to an embodiment of the present invention.
FIGS. 7A and 7B are a front view and a side view of a liquid crystal display device using a backlight device (backlight system) according to a first example of an embodiment of the present invention. FIGS.
FIGS. 8A and 8B are a front view and a side view of a liquid crystal display device using a backlight device (light guide plate type) according to a second example of one embodiment of the present invention. FIGS.
FIG. 9 is a diagram illustrating an example of a conventional technique for improving color reproducibility.
FIG. 10 is a diagram illustrating an example of a conventional technique for improving color reproducibility.
[Explanation of symbols]
1: fluorescent tube, 2: LED, 3: inverter circuit, 4: LED lighting circuit, 5: dimming control means, 6: power supply device, 37: various optical members, 37A: reflection sheet or reflection plate, 57B: light guide plate 37C: diffusion plate, 37D: diffusion sheet, 37E: prism sheet, 37F: reflective polarizing sheet, 38: housing, 39: liquid crystal panel.

Claims (10)

An illumination device having a first light source and a second light source having spectral characteristics different from the spectral characteristics of the first light source,
The spectral characteristic of the first light source has a maximum wavelength of at least 3 or more in the visible light wavelength range,
The spectral characteristic of the second light source has a maximum wavelength of emission intensity of 1 or 2 in the visible light wavelength range,
The illumination device according to claim 1, wherein the 1 or 2 maximum wavelength of the spectral characteristics of the second light source and the 1 or 2 maximum wavelength of the spectral characteristics of the first light source are substantially the same. The lighting device according to claim 1.
One of the local maximum wavelengths of the spectral characteristics of the first light source is present in the green wavelength range, and the local maximum wavelength of the spectral characteristics of the second light source is the red wavelength range or the blue wavelength range or both of them. An illumination device characterized by being in the wavelength range of. The lighting device according to claim 1 or 2,
The half-width range of the spectrum characteristic due to the spectral characteristic of the first light source and the half-width of the spectral characteristic due to the maximum wavelength of 1 or 2 and the half-value width of the spectral characteristic due to the spectral characteristic of the first light source due to the maximum wavelength of 1 or 2 . An illumination device characterized in that there is a region overlapping with a wavelength range . In the illuminating device of any one of Claim 1 to 3,
The maximum wavelength of the first and second light sources is a wavelength region exhibiting a red color. In the illuminating device of any one of Claim 1 to 4,
An illuminating device comprising a dimming control means for adjusting the brightness of at least one of the first light source and the second light source. The lighting device according to claim 5.
The dimming control means creates two types of PWM signals to dimm the brightness of the first light source and the second light source. In the illuminating device of any one of Claim 1-6,
The first light source is a fluorescent tube light source, and the second light source is a light emitting diode light source or an electroluminescence light source. In addition to the lighting device according to any one of claims 1 to 7,
A backlight device comprising an optical member for imparting light distribution characteristics and luminance distribution characteristics to illumination light of the illumination apparatus. In addition to the backlight device according to claim 8,
A display device comprising a non-self-luminous display panel that can be displayed by the backlight device.   The display device according to claim 9, wherein the non-self-luminous display panel is a liquid crystal display panel.

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