Illumination device and liquid crystal display device

An illumination device includes an LED package, an LED driver including an FET, and a thermistor disposed on a substrate. A plurality of such LED packages are disposed on the substrate such that a first area and a second area, each determined by vertices corresponding to LED packages, are defined on the substrate. The thermistor is disposed in the first area, and the FET is disposed in the second area, which is outside of the first area. The thermistor detects a temperature in the first area. Such a configuration allows the thermistor to detect, in accordance with the temperature in the area, the temperature of heat transferred from the LED packages, without being affected by heat generated by the FET. This makes it possible to efficiently make temperature corrections to stabilize color temperature and luminance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to illumination devices and liquid crystal display devices, especially to an illumination device and a liquid crystal display device, each of which is stable in color temperature and luminance.

2. Description of the Related Art

Cold cathode fluorescent lamps (hereinafter referred to as “CCFLs”) have been conventionally used as backlights incorporated in back of liquid crystal panels of transmissive liquid crystal display devices used in laptop personal computers, computer monitors and television receivers. However, in recent years, due to the amelioration, among others, of the light efficiency of light-emitting diodes (hereinafter referred to as “LEDs”) and to the reduction of their cost, LEDs are increasingly being used as backlights of liquid crystal display devices.

LED backlight devices can either be of the direct type, where LEDs are arrayed below the back surface of a display panel of a liquid crystal panel or the like, or of the edge-light type, where a light guide plate is used. In general, the former is higher in efficiency in the use of light than the latter. The former also allows a reduction in weight.

LED backlight devices can, among others, either include an array of white LEDs that emits a white illuminating light, or include an array of LEDs of three colors, namely red (R), green (G), and blue (B), whose emitted lights are mixed to give a white light. It should be noted here that white LEDs are of a type that gives a white light by combining RGB fluorescent materials with a short-wavelength LED chip, of a type that generates a white light by combining a yellow fluorescent material with a blue LED chip, of a type that generates a white light as a mixture of lights emitted by LED chips of three colors (RGB), or of a type that generates a white light as a mixture of lights emitted by LED chips of two complementary colors.

In general, LEDs have characteristics such that their relative luminance tends to decrease with an increase in ambient temperature, i.e., have such a problem that their light efficiency changes depending on fluctuations in ambient temperature. In order to address this problem, the development of an LED backlight device which is not affected by fluctuations in ambient temperature and which maintains fixed light efficiency is in progress.

A specific example is disclosed in Japanese Patent Application Publication No. 2006-147373 A, discloses a backlight device including: a light source having a plurality of light-emitting diodes; a driving control section that drives the plurality of light-emitting diodes; and a temperature sensor that detects the temperatures of the light-emitting diodes. In the backlight device, a first preset upper limit temperature that is not higher than the maximum rated temperatures of the light-emitting diodes and a second preset upper limit temperature that is lower than the first preset upper limit temperature are preset in the driving control section. Japanese Patent Application Publication No. 2006-147373 A describes that the driving control section reduces an amount of driving electric current in cases where a temperature detected by the temperature sensor is not lower than the first preset upper limit temperature, fixes the amount of driving electric current at the present value in cases where the temperature detected by the temperature sensor is lower than the first preset upper limit temperature and higher than the second preset upper limit temperature, and increases the amount of driving electric current in cases where the present amount of driving electric current is lower than a preset value and in cases where the temperature detected by the temperature sensor is not higher than the second preset upper limit temperature. Further, Japanese Patent Application Publication No. 2006-147373 A mentions that the above-described configuration alleviates deterioration in characteristics of and/or failures in the light-emitting diodes used as the light source for the backlight.

Because such a conventional backlight device as disclosed in Japanese Patent Application Publication No. 2006-147373 A equally illuminates a whole area, there is a certain trend in variations in temperature among the LEDs. For this reason, the deterioration in characteristics of the LEDs can be reduced to a certain degree by presetting a temperature that is used as a benchmark when the driving control section controls the driving of the LEDs.

In recent years, however, area-active backlights have been attracting attention as illumination devices for use in display devices and the like. An area-active backlight is a backlight divided into small areas, thus allowing the control of the luminance of the backlight for each of the separate small areas in accordance with the gradations of an image displayed on a liquid crystal display device. In such an area-active backlight, the whole area is not equally illuminated; the emission of the light source (i.e., LEDs) is controlled for each area. In other words, for example, in the case of use of an area-active backlight in a display device, the LEDs of each area vary in electric power inputted thereto, depending on video signals. For this reason, the distribution of temperature within the backlight is always not constant, and varies depending on video signals. Accordingly, the following problem arises: namely, based on the preset temperature, a stable color temperature and a stable luminance cannot be maintained by merely controlling driving in accordance with a preset temperature. In other words, it is necessary to detect the temperature of each individual LED of each area in real time and to control the driving of the backlight device in accordance with that temperature.

However, a technique for appropriately detecting the temperature of each individual LED of each area in an area-active backlight and controlling the driving of the area active backlight in accordance with that temperature remains undeveloped.

SUMMARY OF THE INVENTION

In view of the above-described problems, preferred embodiments of the present invention provide an illumination device and a liquid crystal display device, each of which is stable in color temperature and luminance.

According to a preferred embodiment of the present invention, an illumination device includes a substrate, a plurality of luminous bodies disposed on the substrate, a driving section arranged to drive the plurality of luminous bodies, and a temperature detecting section disposed in an area surrounded by the plurality of luminous bodies, wherein the driving section is disposed outside of a polygonal area determined by vertices corresponding to the plurality of luminous bodies surrounding the temperature detecting section.

According to another preferred embodiment of the present invention, an illumination device includes a substrate, a plurality of luminous bodies disposed on the substrate, a driving section arranged to drive the plurality of luminous bodies, and a temperature detecting section disposed in an area surrounded by the plurality of luminous bodies, wherein a plurality of polygonal areas determined by vertices corresponding to the luminous bodies are located on the substrate, the driving section and the temperature detecting section are disposed in different ones of the polygonal areas, and the temperature detecting section is arranged to detect a temperature of the substrate in the polygonal area in which the temperature detecting section is disposed.

According to the above configuration, the luminous bodies, the driving section, and the temperature detecting section are preferably disposed on the same substrate. Further, a plurality of such luminous bodies are disposed on the substrate, whereby a plurality of polygonal areas determined by vertices corresponding to the luminous bodies are disposed on the substrate. It should be noted that the “polygonal areas determined by vertices corresponding to the luminous bodies” means that the luminous bodies are positioned at the vertices of the polygonal areas and that an area surrounded by line segments connecting the luminous bodies serving as the vertices is polygonal.

When in operation, the driving section generates heat and causes an increase in temperature of a specific area of the substrate. In the area of the substrate in which there is an increase in temperature due to the heat generated by the driving section, it is difficult to accurately detect the temperature of heat transferred from the luminous bodies. In this configuration, the driving section is disposed outside of a polygonal area determined by vertices corresponding to luminous bodies surrounding the temperature detecting section. Preferably, the driving section and the temperature detecting section are disposed in different polygonal areas (i.e., in different “polygonal areas” among the plurality of “polygonal areas”). In other words, the temperature detecting section is disposed on the substrate so as to be in an area that is relatively small in temperature change that is caused by the heat generated by the driving section during operation. Then, the temperature detecting section detects the temperature in the polygonal area in which the temperature detecting section is disposed. For this reason, the temperature detecting section can accurately detect the temperature in the polygonal area in which the temperature detecting section is disposed, without being affected by the heat generated by the driving section.

The temperature in the polygonal area in which the temperature detecting section is disposed is correlated with the temperatures of the luminous bodies. Accordingly, this configuration makes it possible to estimate the temperatures of the luminous bodies in accordance with temperature data detected by the temperature detecting section. Hence, it is possible to efficiently make temperature corrections and to exhibit a stable color temperature and luminance.

Further, the liquid crystal display device includes the illumination device as a backlight.

The illumination device can efficiently make temperature corrections, thus exhibiting a stable color temperature and luminance. Accordingly, the above configuration makes it possible to achieve a liquid crystal display device to be stable in color temperature and luminance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described below with reference toFIG. 1AthroughFIG. 11. The present invention, however, is not limited to the preferred embodiments described below.

As illustrated inFIG. 5, a liquid crystal display device3in accordance with the present preferred embodiment includes a liquid crystal panel70, a liquid crystal panel driving circuit71, a controller72, an illumination device2, an optical member (not shown) such as a diffusion plate, and a power supply control section73. The controller72controls the liquid crystal panel driving circuit71and the illumination device2in accordance with input video data. In response to the control from the controller72, the liquid crystal display panel driving circuit71drives the liquid crystal panel70, and the illumination device2radiates light. The light radiated from the illumination device2is supplied to the liquid crystal panel70through a diffusion plate (not shown) or the like. Further, the power supply control section73controls a power supply system of the liquid crystal display device3in accordance with the turning-on and turning-off of the power supply by a user.

For example, as illustrated inFIG. 6, the illumination device2includes a plurality of light source modules (each indicated as “LM” inFIG. 6) 1 (i, j) (i=1, 2 . . . n, j=1, 2 . . . m, where i and j each indicate a given integer of not less than 1) disposed in a matrix manner.FIG. 7illustrates a portion of the illumination device2(that includes three light source modules1). More specifically, as illustrated inFIG. 7, the illumination device2includes a plurality of light source modules1and an LED control section45. Each of the light source module1includes: at least one light-emitting diode package (hereinafter referred to as “LED package”)20(luminous body) equipped, for example, with one or more red light-emitting diode chips (hereinafter referred to as “red LEDs”), one or more green light-emitting diode chips (hereinafter referred to as “green LEDs”), and one or more blue light-emitting diode chips (hereinafter referred to as “blue LEDs”); at least one thermistor30(temperature detecting section, temperature detecting member); and at least one LED driver40(driving section). It should be noted that, for convenience of illustration, each of the light source modules1ofFIG. 7includes one LED package20, one thermistor30, and one LED driver40.

FIG. 1Ais a plan view (top surface view) illustrating the configuration of a light source module1that is provided in the illumination device2.FIG. 1Bis an oblique perspective view illustrating the configuration of a relevant portion of the light source module1as seen from a cross-section of the light source module1cut along the line A-A inFIG. 1A.

As shown inFIGS. 1A and 1B, the light source module1preferably includes LED packages20, thermistors30, and LED drivers40. The LED packages20, the thermistors30, and the LED drivers40are disposed on the same substrate10, the thermistors30being located on the front surface of the substrate. Details about the light source module1are omitted in the present paragraph, as they will be explained later in this specification.

Specifically, the LED packages20can each be realized by an LED package equipped with one red LED, two green LEDs, and one blue LED as indicated by the letters R (red), G (green), and B (blue) inFIG. 8. Such an LED package can emit a white light and a light of the color of each of the LEDs by adjusting the ratio of emission among the four LEDs. The present preferred embodiment describes the LED packages20as LED packages each configured to have four LEDs contained therein, for example, as shown inFIG. 8. It must be noted, however, that the present preferred embodiment is not limited to such a configuration, and that various types of LED packages disclosed in the prior art can also be used as such LED packages20. For example, four packages respectively containing the red, green, and blue LEDs can also be used as LED packages20.

As shown inFIG. 7, the LED control section45includes an LED control circuit47(LED driving circuit) and a memory46containing a look-up table from which a value for correction of the value of output of the LED package20is outputted in accordance with the value of the thermistor30. The LED control section45controls the LED driver40in accordance with an instruction from the controller72. In response to the control from the LED control section45, the LED driver40drives the red, green, and blue LEDs, mounted inside of the LED package20, individually to emit lights.

The following explains a method in accordance with the present preferred embodiment for driving the LEDs in the illumination device2. Specific examples of the LED driving method include (1) a regulator system shown inFIG. 10(hereinafter referred to as “first regulator system” for ease of explanation) and (2) a regulator system shown inFIG. 11(hereinafter referred to as “second regulator system” for ease of explanation). The following describes the LED driving method as either the first regulator system or the second regulator system; however, the present invention is not limited to these two LED driving methods.

First, in the “first regulator system”, as shown inFIG. 10, one LED or a plurality of series-connected LEDs (for example, four LEDs inFIG. 10) is/are driven by a constant electric current. At this point, an FET42(electric current control transistor, driving section) provided inside of the LED driver40is used to adjust an electric current that is applied from a control circuit41(driving circuit, driving section) to each LED, whereby the driving of each separate LED can be controlled. The following explains the amount of electric power that is consumed by the LEDs and the LED driver when the LEDs are driven by the first regulator system.

When each LED mounted inside of the LED package20is driven by the first regulator system, as shown inFIG. 10, a constant electric current (Iin) is applied to each of the series-connected LEDs. Even if it is supposed that there are no variations in voltage Vfnecessary for applying the electric current Iin, Vlossis about 0.6 V, for example. It is assumed here, for example, that the Vf's of the red LED, two green LEDs, and blue LED of the LED package20shown inFIG. 8are about 2.0 V, about 6.0 V (3.0 V×2), and about 3.0 V, respectively, and the driving currents are about 30 mA, about 25 mA, and about 20 mA, respectively, for example. Further, it is assumed that the variations in Vfof each LED fall within about ±0.1 V, for example. Furthermore, it is assumed that the light source module is realized by such a light source module as shown inFIG. 1A. The light source module1shown inFIG. 1Apreferably has 32 LED packages20, for example, disposed on the substrate10and each preferably equipped with three sets of LEDs, namely one red LED (one set), two green LEDs (one set), and one blue LED (one set), for example. In other words, the light source module1shown inFIG. 1Aincludes 96 (=32×3) sets of LEDs, for example. The light source module1shown inFIG. 1Apreferably includes six LED drivers40, for example. Accordingly, in the light source module1shown inFIG. 1A, the 96 sets of LEDs are driven by the six LED drivers40, for example. That is, one LED driver40drives sixteen sets of LEDs, for example. Under the above conditions, each LED package20consumes an electric power of about 0.27 W, for example. Accordingly, in consideration of the variations in Vfof each LED, the FET42of the LED driver40consumes an electric power of not less than about 0.27 W, for example.

Next, the “second regulator system” is explained. In the second regulator system, as shown inFIG. 11, while the plurality of series-connected LEDs (eight LEDs inFIG. 11) are being driven by a constant electric current, a driving voltage is applied only to the LEDs (one LED inFIG. 11) among the plurality of LEDs which needs to be driven to emit light. As for the LEDs that do not need to be driven to emit light, the electric current is diverted by using a switch element (not shown) provided inside of the control circuit41, whereby the driving voltage is not applied to the LEDs that do not need to be so driven. Further, the control circuit41and the FET42are separate packages. Accordingly, the driving of each separate LED can be controlled with a high degree of accuracy. The following explains the amount of electric power that is consumed by the LEDs and the LED driver when the LEDs are driven by the second regulator system.

First, it is assumed that the voltages Vfof the red LED, two green LEDs, and blue LED of the LED package20shown inFIG. 8are about 2.0 V, about 6.0 V (3.0 V×2), and about 3.0 V, respectively, and the driving currents are about 30 mA, about 25 mA, and about 20 mA, respectively, for example. Further, it is assumed that the variations in Vfof each LED fall within about ±0.1 V, for example. Furthermore, it is assumed that the light source module1is realized by such a light source module as shown inFIG. 3. The light source module1shown inFIG. 3includes such LED packages20as shown inFIG. 8, each equipped with four LEDs, namely one red LED, two green LEDs, and one blue LED, for example. Because 32 LED packages20, for example, are preferably disposed on the substrate10, a total of 128 LEDs, for example, are preferably disposed on the substrate10. The light source module shown inFIG. 3preferably includes sixteen FETs42, for example, each being mounted as a separate package from an IC (not shown) including two driving circuits. Accordingly, in the light source module1shown inFIG. 3, the 128 LEDs are preferably driven and controlled by the sixteen FETs42, for example. In other words, one FET42preferably drives and controls eight LEDs, for example. In this case, when only one of the LEDs is lighted under the second regulator system, the voltages of the remaining seven LEDs are absorbed by the FET42. In this situation, the FET42consumes, at the maximum, as much electric power as would be consumed by seven LEDs. Accordingly, under such conditions, specifically, the maximum amount of electric power that is consumed is about 0.525 W, for example.

As described above, the FET42consumes electric power no matter what driving method is used to drive the LEDs. Especially, the FET42consumes more electric power in the case of driving by the second regulator system than in the case of driving by the first regulator system. Since the FET42consumes electric power, the FET42generates heat at the time of operation. In other words, when the illumination device2in accordance with the present preferred embodiment is in operation, the LED driver40or the FET42as well as the LED package20generates heat.

Generally speaking, the luminance of an LED changes depending on the temperature. Specifically, as shown inFIG. 9, the red, green, and blue LEDs decrease in luminance with an increase in temperature. The letters R, G, and B inFIG. 9indicate the red, green, and blue LEDs, respectively. Accordingly, in order to cause the LEDs to emit light at a stable luminance in the illumination device2, it is preferable to detect the temperature of the LED package20and, based on the temperature, to control the driving of the LED package20so as to stabilize the luminance of each of the LEDs mounted in the LED package20. The illumination device in accordance with the present preferred embodiment preferably uses a thermistor30to perform a temperature correction for the luminance of each of the LEDs mounted in the LED package20.

In other words, in the present preferred embodiment, when the LED control section45receives a temperature detected by a thermistor30disposed in a polygonal area determined by vertices corresponding to LED packages20whose temperatures are to be corrected as will be mentioned later, the LED control section45controls the LED packages20, by which the polygonal area is determined, through the LED driver40in accordance with the look-up table mentioned above.

Specifically, the thermistor30first detects temperature data that is used as a benchmark for temperature correction of each LED package20. In other words, in order to obtain an index of the temperature of the LED package20, the thermistor30detects the temperature of the substrate. The thermistor30may detect the internal temperature of the substrate and the ambient temperature of the surface of the substrate as well as the surface temperature of the substrate, as long as these temperatures are correlated with the temperature of the LED package20. Then, the thermistor30transmits results of the detection, i.e., the temperature data to the LED control section45, or more specifically, to an AD conversion circuit of the memory46. Upon receiving the temperature data, the LED control section45controls the LED driver40in accordance with correction values, arranged in the look-up table determining a correction value of luminance of each LED contained in the LED package20, which correspond to the temperature data stored in the memory46, thereby adjusting the amount of emission (i.e., the luminance) of each LED. More specifically, as shown inFIGS. 10 and 11, the LED driver40includes a control circuit41and an FET42(electric current control transistor). In response to the control from the LED control section45, the control circuit41uses the FET42to adjust an electric current that is applied to each LED mounted in the LED package20, whereby the LED control section45adjusts the amount of emission of each separate LED.

A specific example of how the LED control section45adjusts the amount of emission of each LED through the LED driver40is, but is not limited to, pulse-width modulation (PWB). Specifically, the LED control section45reads, in accordance with the temperature data transmitted from the thermistor30, values stored in the memory46inside of the LED control section45, and adjusts the pulse-width of emission time, thereby making it possible to adjust an electric current that is applied to each LED. As mentioned above, the luminance of an LED decreases with an increase in temperature. Therefore, in cases where the temperature data indicates an increase in temperature of an LED, the LED control section45adjusts the pulse-width of emission time so that it becomes wider.

Thus, in the illumination device2in accordance with the present preferred embodiment, the temperature of each LED inside of the LED package20is detected by the thermistor30, and the LED control section45controls the driving of each separate LED in accordance with the temperature data. As such, when used in combination with an area-active drive system (not shown), the illumination device2can realize a backlight high in contrast and low in power consumption. In other words, the liquid crystal display device3includes the illumination device2as a backlight and allows for area-active control.

Now then, in a light source module1provided in an illumination device2, as shown inFIGS. 1AthroughFIG. 4, LED packages20, thermistors30, and LED drivers40(only FETs42by which the LED drivers40are constituted are shown inFIGS. 1AthroughFIG. 4) are disposed on the same substrate10. As mentioned previously, the LED drivers40generate heat at the time of operation of the illumination device2. For this reason, at the time of temperature detection, the thermistors30may be affected by the heat generated by the LED drivers40. Accordingly, in order for the thermistors30to be able to accurately detect the temperatures (i.e., the temperature data) to be used as a benchmark for temperature correction of the LED packages20, it is preferable that the thermistors30be disposed in such a position that they will hardly be affected by the heat generated by the FETs42.

The following describes the light source module1with emphasis on the arrangement and configuration of the thermistors30in the light source module1.

As shown inFIGS. 1A and 1B, the light source module1in accordance with the present preferred embodiment includes a substrate10, LED packages20, thermistors30, and LED drivers40(only FETs42by which the LED drivers40are constituted are shown inFIGS. 1A and 1B). The following is an explanation of a configuration preferably using a thermistor as a temperature detecting section. Thermistors are less expensive than light sensors and the like. For this reason, using a thermistor as a temperature detecting section makes it possible to reduce the production cost of the light source module1. It should be noted that the temperature detecting section (temperature detecting member) is not restricted to the thermistor, and can for example be a light sensor. In this case, it is possible to detect the temperature of an LED package by detecting the luminance of an LED with use of the light sensor.

In the light source module1, as shown inFIGS. 1A and 1B, the LED packages20and the thermistors30are disposed on one surface of the substrate10, and the LED drivers40including the FETs42(only the FETs42by which the LED drivers40are constituted are shown inFIGS. 1A and 1B) are disposed on the other surface of the substrate10. In other words, that surface of the substrate10on which the LED packages20and the thermistors30are disposed and that surface of the substrate10on which the LED drivers40are disposed are different. This makes it possible to keep the thermistors30and the LED packages20away from the LED drivers40serving as heat sources. This enables the thermistors30to more accurately detect the temperature of heat transferred from the LED packages20.

Further, it is preferable that, as shown inFIG. 1B, a heat dissipation sheet80(heat dissipation material) be provided on a surface of the substrate10opposite a surface on which the luminous LED packages20are disposed, in such a way as to be on the backside of an area in which the LED packages20are disposed. This makes it possible to efficiently dissipate the heat generated by the LED packages20, and to prevent an increase in temperature of the LED packages20.

The heat dissipation sheet80is not particularly limited as long as it has a heat dissipation effect. It is not particularly limited in shape, either.

The light source module1shown inFIG. 1Apreferably has 32 LED packages20, for example, disposed on the substrate10preferably in a 2×16 matrix, for example. Accordingly, on the substrate10,15quadrangular areas determined by vertices corresponding to the LED packages20are formed. These quadrilateral areas are disposed in such a way as to be joined together one after another in a line. The thermistors30and the FETs42or the LED drivers40including the FETs42are disposed in mutually different areas among these quadrilateral areas. In the present preferred embodiment, an area in which a thermistor30is disposed is referred to as “area50”, and an area in which an FET42or an LED driver40including the FET42is disposed is referred to as “area60”. In other words and in accordance with the above, in the present preferred embodiment, a thermistor30and an FET42or an LED driver40including the FET42are disposed in a quadrilateral area50and a quadrilateral area60, respectively.

In the light source module1, as shown inFIG. 1A, the areas50and60are adjacent to one another. More specifically, on the substrate10, the areas50and60are disposed alternately in a succession, as in the following order: “area50, area60, area50, area60, area50, . . . ”.

The thermistor30disposed in the area50may be configured so as to be able to detect the temperature of heat transferred from all of the four LED packages20respectively located at the vertices determining the quadrilateral area50. However, the thermistor30is preferably configured so as to be able to detect the temperature of heat transferred equally from all of the four LED packages20.

FIG. 12shows the results of a simulation of diffusion of heat generated by each of the LED packages20, the results being represented by isothermal lines.

From the results shown inFIG. 12, it may be understood that the temperatures of a plurality of LED packages20can be measured by a single thermistor30by disposing a thermistor30in a polygonal area surrounded by LED packages20whose temperatures are to be corrected, i.e., a polygonal area defined by a plurality of LED packages20whose temperatures are to be corrected.

Further, from the results shown inFIG. 12, it may be understood that a thermistor30disposed in an area, among the polygonal areas determined by vertices corresponding to the LED packages20, which is different from an area in which an FET42is disposed, is not affected by heat generated by the FET42. Accordingly, the above configuration enables the thermistor30to accurately detect the temperature in the polygonal area in which the thermistor30is disposed.

With the present preferred embodiment, since each thermistor30is thus arranged so as to be able to detect the temperature of heat transferred from a plurality of LED packages20, the number of thermistors30that are mounted in the light source module1may be smaller than the number of LEDs that are mounted in the light source module1. This makes it possible to reduce the production cost of the light source module1, and therefore of the illumination device2and of the liquid crystal display device3.

Further, from the results shown inFIG. 12, it may be understood that when the thermistor30is at an equal distance from each of the LED packages20, the thermistor30can equally detect the temperature of heat transferred from the four LED packages20, without being biased toward any one of the four LED packages20. Accordingly, it is preferable that the thermistor30be disposed near the circumcenter of the area50. The phrase “near the circumcenter” is intended to mean, in addition to the circumcenter, an area near the circumcenter, i.e., an area located substantially at an equal distance from each of the vertices forming the polygon. The phrase “substantially at an equal distance” is meant to encompass, in addition to an equidistant range, a range that is not exactly equidistant but can be considered as equivalent to an equidistant range.

Accordingly, when the arrangement of the LED packages20whose temperatures are to be corrected is determined, the shape of the polygon is automatically determined. As explained above, the polygon is a quadrilateral when the number of LED packages20surrounding the thermistor30(more specifically, when the number of LED packages20disposed substantially at an equal distance from one thermistor30, for example) is four, for example, and is a triangle when the number of LED packages20surrounding the thermistor30is three, for example.

However, as shown inFIG. 2, a plurality of thermistors30may be disposed in the area50. InFIG. 2, two thermistors30are disposed in the area50. In the present preferred embodiment, one to four thermistors30may be disposed in the area50. More specifically, for example, in the case of a configuration in which the temperature in the vicinity of each separate one of the four LED packages20located at the vertices of the quadrilateral determining the area50is detected separately, four thermistors30may be disposed in the area50; while in the case of a configuration in which the temperature in the vicinity of two LED packages20is detected by one thermistor30, two thermistors30may be disposed in the area50. Thus, an increase in the number of thermistors30that are disposed in the area50leads to an increase in the number of thermistor30per LED package20as compared to a situation in which one thermistor30is disposed in the area50. For this reason, the temperature of heat transferred from the LED package20can be detected more accurately. Further, one area50may be equal to or different from another in the number of thermistors30that are disposed in each area50.

As shown inFIG. 2, in the case of configuration including two thermistors30in the area50, it is preferable that the two thermistors30be configured so that one of them can detect the temperature of heat transferred from two LED packages among the four LED packages located at the vertices of the quadrilateral determining the area50and the other can detect the temperature of heat transferred from the remaining two LED packages. In this regard, it is preferable that each of the two thermistors30be disposed at an equal distance from the two LED packages whose temperatures are to be detected by that thermistor30. In addition, it is preferable that every one of the thermistors30be placed at an equal distance from an LED package20. This enables each of the two thermistors30to more accurately detect the temperature of heat transferred from the LED packages20whose temperatures are to be detected by that thermistor30.

Further, as shown inFIG. 4, a light source module1in accordance with another preferred embodiment can be configured such that a plurality of LED packages20define a deltaic configuration on the substrate10. The term “deltaic configuration” here means that each area formed by connecting adjacent LED packages together is triangular. InFIG. 4, thirty LED packages20, for example, form a deltaic configuration in two lines with a half-pitch offset, whereby thirty triangular areas determined by vertices corresponding to the LED packages20are formed, for example. In each of these triangular areas, a thermistor30or a FET42or an LED driver40including the FET42is disposed. In this preferred embodiment as well, an area50in which a thermistor30is disposed and an area60in which an FET42or an LED driver40including the FET42is disposed are adjacent to each other. Further, the thermistor30is disposed near the circumcenter of the triangular area50. Such a configuration enables the thermistor30disposed in the area50to equally detect the temperatures of all of the three LED packages located at the vertices of the triangle determining the area50. Further, in this preferred embodiment as well, a plurality of thermistors30may be disposed in the area50.

As stated above, the FET42or the LED driver40including the FET42is disposed in the area60. While the arrangement in the area60of the FET42or of the LED driver40including an FET42is not particularly limited, it is preferable that the FET42or the LED driver40including an FET42be disposed as far away as possible from the thermistor30. Specifically, for example, as shown inFIG. 1AandFIG. 2, in a configuration in which the quadrilateral areas50and60are arrayed alternately to form a line, it is preferable that the FET42or the LED driver40including the FET42be disposed near the circumcenter of the area60. Meanwhile, as shown inFIG. 4, in a configuration in which the thermistor30is disposed near the circumcenter of the triangular area50, it is preferable that the FET42or the LED driver40including an FET42be disposed near the midway point between the thermistor30and a thermistor30adjacent thereto. This makes it possible to equalize and maximize the distance between each thermistor30and an FET42on the substrate10. This enables every one of the thermistors30to accurately detect the temperature without being affected by heat generated by any FET42.

As shown inFIGS. 10 and 11, the LED driver40includes the control circuit41and the FET42. The LED driver40may be configured such that the control circuit41and the FET42are integrated, or may be configured such that the control circuit41and the FET42are separated. As stated above, during the operation of the illumination device2, the LED driver40generates heat, or more precisely, the FET42provided in the LED driver40generates heat. Accordingly, when configured such that the control circuit41and the FET42are integrated, the LED driver40is wholly disposed in the area60. Meanwhile, when configured such that the control circuit41and the FET42are separated, the LED driver40may be wholly disposed in the area60, or only the FET42serving as a heat source may be disposed in the area60.

Further, the number of LED drivers40that are disposed in each area60is not limited to one, and a plurality of LED drivers40may be disposed in each area60. Specifically, the number of LED drivers40that are disposed in one area60may be set so that as many LED drivers40as needed to drive all the LEDs mounted in the LED packages20disposed in the light source module1are disposed on the substrate10. Further, it is not necessary that one area60is equal to another in the number of LED drivers40that are disposed in each area60. One area60may be different from another in the respect. For example, as shown inFIG. 3, there may be a configuration in which two LED drivers40are disposed in one area60while three LED drivers40are disposed in another area60.

InFIG. 1AthroughFIG. 4, the light source module1is arranged such that the LED packages20form a matrix configuration or a delta configuration on the substrate10. However, the present invention is not limited to such a configuration. This being said, it is preferable that the LED packages20be arranged regularly on the substrate10. This makes it possible to place thermistors30and FETs42or LED drivers40including the FETs42at regular intervals. Such a configuration allows an improvement in optical uniformity of the illumination device2.

Each of the preferred embodiments above has been described by way of example where the areas50and60are disposed alternately in a succession. However, the present invention is not limited to such an example, and the areas50and60are not necessarily provided alternately.

For example, when the LED packages20are provided in two or more lines as shown inFIG. 13, a plurality of areas50may be provided in a succession, for example, in such a way as to be surrounded by a plurality of areas60.

Each of the preferred embodiments above has been described by way of example of configuration where, as shown inFIG. 1B, the heat dissipation sheet80is provided in a stripe shape along each line of LED packages20in such a way as to be on the back surface of the substrate10below an area in which the LED packages20are mounted, whereby each component is mounted in an area surrounded by LED packages20.

However, the present invention is not limited to such an example, as long as the thermistor30is free of the influence of heat from an FET42in detecting temperature data that is to be used as a benchmark for temperature correction of each LED package20whose temperature is to be detected. In other words, the FET42only needs to be disposed outside of an area whose temperature is detected by the thermistor30. Since the present preferred embodiment preferably uses one thermistor30for temperature correction of a plurality of LED packages20, the FET42only needs to be basically provided outside of an area surrounded by LED20packages whose temperatures are to be corrected.

As evidenced byFIG. 12, the influence of heat from an FET42is extremely small in an area, among the plurality of polygonal areas determined by vertices corresponding to the LED packages20, which is different from an area in which the FET42is disposed (i.e., outside of a polygonal area determined by vertices corresponding to the LED packages20surrounding the FET42). In other words, a polygonal area in which a thermistor30is disposed is hardly affected by heat generated by an FET42disposed outside of the polygonal area, and the polygonal area in which no FET42is disposed may be considered as an area relatively small in temperature change that is caused by heat generated by the FET42during operation.

Accordingly, it is desirable that the FET42be disposed in the polygonal area determined by the vertices corresponding to the LED packages20. However, the present invention is not limited to this configuration.

In other words, the illumination device in accordance with the present invention only needs to be configured such that the number of temperature detecting sections (e.g., thermistors30) is reduced by disposing, in an area surrounded by a plurality of luminous bodies (e.g., LED packages20) whose temperatures are to be corrected, temperature detecting sections smaller in number than the luminous bodies; no heat sources (e.g., FETs42) other than the luminous bodies are disposed in the area in which the temperature detecting section is disposed.

In any case, as described above, an illumination device in accordance with various preferred embodiments of the present invention is not configured such that a driving section arranged to drive a luminous body and a temperature detecting section arranged to detect a temperature that is used as a benchmark for temperature correction of the luminous body are disposed adjacent to each other (specifically, in the same polygonal area as described above), nor is it configured such that the driving section and the temperature detecting section are respectively disposed on the front and back sides of the same substrate so as to be superposed. This prevents the temperature detecting section from detecting a temperature higher than the actual temperature of the luminous body under the influence of heat from the driving section and thus decreasing in accuracy of feedback of detected values from the temperature detecting section. Therefore, when used in combination with an area-active drive system, the illumination device in accordance with various preferred embodiments of the present invention can drive each separate LED in accordance with a video signal. For this reason, the illumination device can be used as a backlight high in contrast and low in power consumption. Further, for example, an ultraslim television or an ultraslim monitor can be realized by mounting such a backlight in a liquid crystal television or a liquid crystal monitor. Further, the present invention also encompasses light source modules provided in the illumination device and liquid crystal display device in accordance with the present invention.

As described above, an illumination device in accordance with the present preferred embodiment is configured such that a luminous body, a driving section arranged to drive the luminous body, and a temperature detecting section are disposed on a substrate. Further, a plurality of luminous bodies are disposed on the substrate. The temperature detecting section is disposed in an area surrounded by a plurality of luminous bodies, and the driving section is disposed outside of a polygonal area determined by vertices corresponding to the luminous bodies surrounding the temperature detecting section. Further, since the plurality of luminous bodies are disposed on the substrate, a plurality of polygonal areas determined by vertices corresponding to the luminous bodies are formed on the substrate. Preferably, the driving section and the temperature detecting section are respectively disposed in different ones of the polygonal areas. In addition, the temperature detecting section detects a temperature in the polygonal area in which the temperature detecting section is disposed. Accordingly, the temperature detecting section is not affected by heat generated by the driving section and is able to accurately detect a temperature in the polygonal area in which the substrate is disposed. The temperature in the polygonal area in which the substrate is disposed is correlated with the temperature of the luminous body. For this reason, the illumination device in accordance with the present preferred embodiment makes it possible to make temperature corrections with high efficiency and to exhibit a stable color temperature and luminance.

In the illumination device in accordance with the present preferred embodiment, the polygonal area in which the driving section is disposed and the polygonal area in which the temperature detecting section is disposed are preferably adjacent to each other.

In the illumination device in accordance with the present preferred embodiment, the luminous body, the driving section, and the temperature detecting section operate as a set. For this reason, the operation of the illumination device is controlled more easily when the luminous body, the driving section, and the temperature detecting section are disposed relatively close to one another on the substrate. According to the above configuration, the area in which the driving section is disposed and the area in which the temperature detecting section is disposed are adjacent to each other; therefore, the temperature detecting section can be disposed in such a position as not to be affected by heat from the driving section, while the luminous body, the driving section, and the temperature detecting section are being kept relatively close to one another on the substrate. For this reason, in the illumination device in accordance with various preferred embodiments of the present invention, operation control is easy and, based on temperature data detected by the temperature detecting section, the driving of the luminous body can be controlled more precisely by the driving section.

In the illumination device in accordance with the present preferred embodiment, the temperature detecting section is preferably disposed near a circumcenter of the polygonal area.

According to the above configuration, the temperature detecting section is disposed at a substantially equal distance from all the luminous bodies located at the vertices of the polygon delimiting the polygonal area. This enables the temperature detecting section to detect equally the temperature of heat transferred from the luminous bodies, without being biased toward any one of the luminous bodies. In the present specification, the phrase “near the circumcenter” refers to, in addition to the circumcenter (point), an area including the circumcenter.

In the illumination device in accordance with various preferred embodiments of the present invention, the driving section preferably includes a control circuit and an electric current control transistor, the electric current control transistor being disposed in the polygonal area in which the driving section is disposed.

According to the above configuration, the driving section includes the control circuit and the electric current control transistor. The electric current control transistor controls an electric current that is applied to the luminous body. While the driving section is in operation, the electric current control transistor generates heat. In the above configuration, the electric current control transistor is disposed in an area different from the area in which the temperature detecting section is disposed. For this reason, the temperature detecting section is able to accurately estimate the temperature of the luminous body without being affected by heat generated by the electric current control transistor.

In the illumination device in accordance with the present preferred embodiment, the luminous bodies and the temperature detecting section are preferably disposed on one surface of the substrate, and the driving section is disposed on a surface of the substrate opposite the surface on which the luminous bodies and the temperature detecting section are disposed.

The above configuration makes it possible to further distance the luminous body and the temperature detecting section from the driving section. Accordingly, the temperature detecting section is able to more accurately estimate the temperature of the luminous body with less influence of heat generated by the driving section. In addition to this, the luminous body can be prevented from being heated by the heat generated by the driving section.

In the illumination device in accordance with the present preferred embodiment, a heat dissipation material is preferably arranged on the substrate in such a way as to be on a backside of an area in which the luminous bodies are disposed.

According to the above configuration, the heat from the luminous body is dissipated by passing through the heat dissipation material. This makes it possible to prevent an increase in temperature of the heat generating body.

In the liquid crystal display device in accordance with various preferred embodiments of the present invention, the illumination device is preferably provided as a backlight.

The illumination device can efficiently make temperature corrections, thus exhibiting a stable color temperature and luminance. Accordingly, the above configuration makes it possible to achieve a liquid crystal display device stable in color temperature and luminance.

As described above, in various preferred embodiments of the present invention, a temperature detecting section arranged to detect the temperature of a luminous body is disposed in a position with relatively little influence of heat generated by the driving section that is arranged to drive the luminous body (heat generating body). This makes it possible to detect the temperature of the luminous body without being affected by the heat generated by the driving section, and to efficiently perform a temperature correction of emission of the luminous body. For this reason, preferred embodiments of the present invention can be used not only in various illumination devices typified by backlight devices or in the manufacturing field of such devices, but in addition, the preferred embodiments of the present invention can also be widely applied in the field of various display devices such as liquid crystal display devices and liquid crystal televisions.

The present invention being thus described, it should be noted that the same way may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.