TWI612361B - Surface light source device and liquid crystal display device - Google Patents

Abstract

The liquid crystal display device 100 includes a laser light source 5, an LED light source 4, and a heat sink 2. The laser light source 5 emits laser light 51. The LED light source 4 emits LED light 41. The heat sink 2 holds the laser light source 5 and transfers heat generated by the laser light source 5 to the air. The laser light source 5 is disposed at a position lower than the LED light source 4. The liquid crystal display device 100 suppresses heat of the LED light source 4 that is not easily affected by heat from being transmitted to the laser light source 5 that is easily affected by heat.

Description

Surface light source device and liquid crystal display device

The present invention relates to a cooling structure of a liquid crystal display device having two types of light sources.

The liquid crystal display element included in the liquid crystal display device itself does not emit light. Therefore, the liquid crystal display device is provided with a backlight device on the back of the liquid crystal display element as a light source for illuminating the liquid crystal display element. The light emitted from the backlight device enters the liquid crystal display element and then emits image light. In recent years, as the performance of blue light emitting diodes (hereinafter referred to as LEDs (Light Emitting Diodes)) has improved dramatically, backlight devices using blue LEDs as light sources have been widely used.

The constituent elements of a light source using a blue LED include a blue LED element and a phosphor. The phosphor absorbs light emitted by the blue LED element and emits blue complementary color light. This kind of LED is called white LED, and the complementary color of blue is yellow including green and red.

The white LED has high electro-optical conversion efficiency and can effectively reduce power consumption. "Electro-optical conversion" refers to the conversion of electricity into light. However, white LEDs have problems with a wide wavelength band and a narrow color reproduction range. The liquid crystal display device includes a color filter inside the liquid crystal display element. The liquid crystal display device extracts light in the red, green, and blue spectral ranges through a color filter, and presents colors. Light sources such as white LEDs have a continuous spectrum with a wide wavelength band. It is necessary to improve the color purity of the display color of the color filter. In other words, it is necessary to narrow the wavelength band of the color filter. However, if the wavelength band of the color filter is set to be narrow, the use efficiency of light is reduced. This is because the amount of light that is not used for liquid crystal display elements to display images increases. In addition, there is a problem that the brightness of the display surface of the liquid crystal display element is reduced, and the power consumption of the liquid crystal display device is increased.

In order to improve these problems, there is a backlight device that replaces white LEDs with monochromatic LEDs with higher color purity. Monochrome LEDs are red, green, and blue. In addition, there is also a backlight device using a laser having a higher color purity than a monochromatic LED. Laser colors are red, green, and blue. "High color purity" refers to a narrow wavelength band and good monochromaticity. By using these light sources as the backlight device, the color reproduction range of the liquid crystal display device can be expanded.

However, some elements in light sources composed of LEDs of three primary colors or lasers of three primary colors will have a significant decrease in the electro-optical conversion efficiency with increasing temperature. In particular, red lasers continue to emit high-intensity light at high temperatures, which accelerates degradation and shortens the life of the device. Therefore, in order to obtain a desired amount of light even at high ambient temperature, a heat dissipation mechanism is generally required. "Ambient temperature" includes the ambient temperature at which the liquid crystal display device is placed, and the ambient temperature of the backlight device in the liquid crystal display device.

Patent Document 1 shows a liquid crystal display device 1 in which LED modules 9 are arranged as light sources along two long sides of a liquid crystal display panel 3. The two long sides are the long sides of the upper side and the lower side of the liquid crystal display panel 3. The LED module 9 is mounted on a rising portion 8 of the back frame 7 (paragraph 0009, FIG. 2). The heat sink 27 is attached so as to thermally contact almost the entire back surface of the back frame 7 (FIG. 1). The heat sink 27 is not attached to the LED driving power source 31 and the control board 29. Here, the liquid crystal display The panel is a liquid crystal display element.

Advance technical literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2006-267936 (paragraphs 0009, 0012, Figs. 1, 2).

However, when the backlight device uses two types of light sources such as a direct type and an edge type, it is necessary to consider that the heat of the two light sources is transmitted to each other's light sources. The "direct type" refers to a backlight device in which light sources are arranged on the back of a liquid crystal panel. "Side-light type" refers to a backlight device in which light sources are lined up on the end face of a liquid crystal panel, and then the light guide plate is used to diffuse the light to the entire back of the panel. Therefore, when using a light source that is easily affected by heat, depending on the arrangement of the two light sources, there may be a problem that the temperature of the light source that is easily affected by heat rises.

In view of this, the present invention proposes a liquid crystal display device having a structure capable of suppressing the transfer of heat from a light source that is not easily affected to heat to a light source that is easily affected by heat.

In view of the above problems, the present invention provides a liquid crystal display device including: a laser light source that emits laser light; an LED light source that emits LED light; and a radiator that holds the laser light source and transfers heat generated by the laser light source to In the air, the laser light source is disposed at a position lower than the LED light source.

According to the invention described above, it is possible to suppress heat from being transmitted from a light source that is not easily affected by heat to a light source that is easily affected by heat.

1‧‧‧ back

2, 2a, 2b, 2c, 2d, 2e‧‧‧ radiator

3, 3a, 3b, 3c, 3d, 3e, 3f‧‧‧LED light source array

4‧‧‧LED light source

41‧‧‧LED light

5‧‧‧laser light source

51‧‧‧laser light

8‧‧‧Reflection

81a, 81b, 81c, 81d

82‧‧‧ floor

83‧‧‧ opening

9‧‧‧Reflector

10‧‧‧light guide

11‧‧‧ diffuser

12‧‧‧ Optical Sheet

13‧‧‧LCD display element

14‧‧‧Mounting holes

15‧‧‧Insulation

16‧‧‧ air

17, 18‧‧‧ heat

19‧‧‧ Peripheral component placement

20‧‧‧ air turbulence

21‧‧‧Cooling Fin

22‧‧‧Mounting Department

23‧‧‧hole

24‧‧‧ base plate

25‧‧‧ bottom face

30‧‧‧light guide

100, 102‧‧‧ LCD display device

101‧‧‧ incident surface

200‧‧‧area light source device

FIG. 1 is a perspective view showing the structure of the liquid crystal display device of the first embodiment.

FIG. 2 is a partial perspective view showing the structure of the liquid crystal display device of Example 1. FIG.

FIG. 3 is a perspective view showing the structure of the heat sink of the first embodiment.

FIG. 4 is a block diagram showing the structure of the liquid crystal display device of the first embodiment.

Fig. 5 is a perspective view showing the surface light source device of the first embodiment.

Fig. 6 is a block diagram showing the structure of the liquid crystal display device of the first embodiment.

FIG. 7 is a block diagram showing a structure of a liquid crystal display device of Example 2. FIG.

FIG. 8 is a block diagram showing a structure of a liquid crystal display device of Example 2. FIG.

Example 1

In the following, for easy explanation of the drawings, the coordinate axes of the rectangular coordinate system of XYZ are shown in each drawing. It is assumed that the short-side direction of the liquid crystal display device 100 is the Y-axis direction, the long-side direction is the X-axis direction, and the direction perpendicular to the X-Y plane is the Z-axis direction. It is assumed that the display surface side of the liquid crystal display device 100 is the + Z axis direction, the upper direction of the liquid crystal display device is the + Y axis direction, and the left side when viewing the display surface of the liquid crystal display device 100 is the + X axis direction. "Viewing display surface" means facing the display surface.

FIG. 1 is a rear perspective view of the liquid crystal display device 100 according to the first embodiment. The back surface portion 1 is a holding member arranged on the back surface of the liquid crystal display device 100. For example, the back surface portion 1 is a plate material. The back surface portion 1 is formed by, for example, applying pressure to iron. In Example 1, the back part is also described as a back sheet metal. Therefore, the back surface portion is a member having a heat radiation effect. The heat sinks 2a, 2b, 2c, 2d, and 2e are arranged on the back surface (-Z axis direction side) of the back surface portion 1. The heat sinks 2a, 2b, 2c, 2d, and 2e are arranged at the lower ends in the Y-axis direction of the back surface portion 1. The radiators 2a and 2e are arranged symmetrically on the back side The back of the part 1. The heat sinks 2 a and 2 e are arranged at both ends in the X-axis direction of the back surface of the back surface portion 1. The heat sinks 2 b and 2 d are arranged symmetrically on the back surface of the back surface portion 1. The heat sink 2 c is arranged at the center in the X-axis direction of the back surface of the back surface portion 1. The heat sink 2b is disposed between the heat sink 2a and the heat sink 2c. The heat sink 2d is disposed between the heat sink 2e and the heat sink 2c. The air paths of the radiators 2a, 2b, 2c, 2d, and 2e are provided in a vertical direction (+ Y-axis direction). "Wind path" refers to the path through which the wind circulates to allow heat to escape.

FIG. 2 is a perspective view of the internal structure of the liquid crystal display device 100 as viewed from the liquid crystal display surface side. FIG. 2 shows a state where the liquid crystal display element 13, the optical sheet 12, the diffusion plate 11, the light guide rod 10, and the reflection portion 8 are removed. In FIG. 2, the positions of the heat sinks 2 a, 2 b, 2 c, 2 d, and 2 e arranged on the back surface (-Z axis direction side) of the back surface portion 1 are indicated by broken lines.

The liquid crystal display device 100 of the first embodiment includes a surface light source device 200 that combines an LED light source 4 and a laser light source 5. As shown in FIG. 4, the surface light source device 200 includes a back surface portion 1, a heat sink 2, an LED light source array 3, and a laser light source 5. The surface light source device 200 can include a reflection portion 8, a light guide rod 10, and a diffusion plate 11. An optical sheet 12 and a liquid crystal display element 13 are housed inside the back surface portion 1.

The LED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f are plural LED light sources 4 arranged in a row on a substrate. The substrate on which the LED light sources 4 are arranged is an elongated rectangle. In the first embodiment, the LED light sources 4 of the LED light source array 3 are arranged in the X-axis direction. The LED light source arrays 3 a, 3 b, 3 c, 3 d, 3 e, and 3 f are arranged on the surface in the + Z axis direction of the back surface portion 1. The LED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f are arranged in the Y-axis direction. That is, the plurality of LED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f are arranged at regular intervals in the vertical direction (+ Y-axis direction). As a result, the LED light source 4 has a “straight-down” structure that is two-dimensionally arranged on the back surface of the liquid crystal display element 13.

The LLED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f may also be arranged in the horizontal direction (+ X-axis direction). In this case, the substrates of the LED light source array 3 are arranged in a state of an elongated rectangle with the long side in the Y-axis direction. That is, the LED light sources 4 of the LED light source array 3 may be arranged in the Y-axis direction. One LED light source array 3 may be divided into a plurality. For example, the central portion of the LED light source array 3a in the x-axis direction is divided into two. Furthermore, the number of the LED light source arrays 3a, 3b, 3c, 3d, 3e, 3f is not limited to six. The number of the LED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f can be set to another number according to the size of the liquid crystal display element 13, for example. The number of the radiators 2a, 2b, 2c, 2d, and 2e is also not limited to six. The number of the heat sinks 2a, 2b, 2c, 2d, and 2e can be set to another number according to the size of the liquid crystal display element 13, for example.

FIG. 3 is a perspective view showing the shape of the heat sink 2. The heat sink 2 is made of a material having a high thermal conductivity. For example, the heat sink 2 is made of aluminum. The heat sink 2 includes a heat radiation fin 21. The heat radiating fins 21 are arranged so that the air path faces the vertical direction (+ Y-axis direction). The heat radiating fins 21 are formed on the surface in the −Z axis direction of the base plate portion 24. The base plate portion 24 has a plate shape parallel to the X-Y plane. The heat radiation fins 21 are formed perpendicularly to the base plate portion 24. That is, the heat radiation fin 21 is a plate-like member parallel to the Y-Z plane. The plurality of heat radiation fins 21 are arranged in the X-axis direction.

A mounting portion 22 is formed at the lower end (-Y axis direction) of the heat sink 2. The mounting portion 22 has a plate shape protruding in the + Z axis direction. The mounting portion 22 has a plate shape parallel to the Z-X plane. The mounting portion 22 is a portion where the laser light source 5 is mounted. The mounting portion 22 is formed with a hole 23. The hole 23 penetrates the mounting portion 22 and opens in the Y-axis direction. The laser light source 5 is attached to the hole 23 so as to emit light in the + Y-axis direction. That is, the laser light source 5 is installed in the hole 23. The emission direction of the light from the laser light source 5 faces the + Y axis direction.

In FIG. 3, the mounting portion 22 is rectangular, but is not limited thereto. The mounting portion 22 may have other shapes, such as a circular arc shape. The laser light source 5 may be attached to the hole 23 so that light is emitted in the −Y axis direction. However, in this case, the heat radiation fins 21 are arranged outside the liquid crystal display element 13. Therefore, there is a disadvantage that the frame portion (edge portion) of the liquid crystal display device 100 cannot be made thin. "Border" refers to the part of the frame-shaped casing that surrounds the display screen. In recent years, it has been a popular design to make a portion of a frame-shaped casing that surrounds a display screen thinner. A thin border is also called a "narrow border."

The heat generated by the laser light source 5 is transmitted from the back surface (the side in the -Y axis direction) of the laser light source 5 to the back surface portion 1. The heat transmitted to the laser light source 5 to the back surface portion 1 is transmitted to the lower end surface 25 (the surface on the -Y axis direction side) of the heat sink 2 again. The heat transmitted to the lower end surface 25 (-Y axis direction) of the heat sink 2 is transmitted to the mounting portion 22. The heat transmitted to the mounting portion 22 is transmitted to the heat radiating fin 21 and discharged to the outside air. The heat sink 2 is attached to the back surface portion 1 so that the lower end surface 25 contacts the back surface portion 1.

In FIG. 3, the mounting portion 22 and the heat radiation fin 21 are integrally formed. However, the mounting portion 22 may be other parts, but in this case, the heat dissipation efficiency of the mounting portion 22 may be slightly reduced. However, if the mounting portion 22 is configured by other components, the manufacturing of the heat sink 2 can be facilitated, and the manufacturing cost can be suppressed. In addition, although one laser light source 5 is mounted on one heat sink 2 in FIG. 3, a plurality of laser light sources 5 may be mounted on one heat sink 2.

The LED light source 4 includes a blue LED element and a phosphor. Specifically, the LED light source 4 is a package including a blue LED element that emits blue light, and is filled with a phosphor that absorbs the blue light and mainly emits green light.

The human eye has a higher sensitivity to red color difference. Therefore, the difference in the red wavelength band can make a significant difference in human vision. Here, the wavelength band The difference is a difference in color purity. In the past, a white LED used as a light source of a liquid crystal display device has a low red spectrum energy in a wavelength band of 600 nm to 700 nm. In other words, if a color filter with a narrow wavelength band is used to improve the color purity, the wavelength is limited to a wavelength range of 630nm to 640nm, which is an excellent high purity red. Reduced efficiency. Therefore, there is a problem that the brightness is significantly reduced. Here, high-purity red is called "pure red".

On the other hand, the laser light emitting element 5 has a narrow wavelength band, and can suppress light loss to obtain light with high color purity. The use of a red laser light emitting element 5 having particularly high monochromaticity among the three primary colors has an excellent effect on reducing power consumption and improving color purity. Therefore, in the liquid crystal display device 100 of the first embodiment, the laser light source 5 is a light source that emits red light.

The red laser light source 5 which can emit an excellent pure red in the wavelength range of 630nm to 640nm will significantly decrease the electro-optical conversion efficiency as the temperature of the element rises. In other words, the red laser light source is a light source that is easily affected by heat. "Pure red" refers to high-purity red with a narrow wavelength range and deep red. The dark red is preferably in the wavelength range of 630 ~ 640nm. If the laser light source 5 continues to output high-intensity light in a high-temperature state, the degradation of the element will be accelerated, and the life will be shortened. Therefore, an efficient cooling system must be introduced.

On the other hand, the electro-optical conversion efficiency of the LED light source 4 has less change in temperature than the laser light source 5. In other words, LED light sources are light sources that are not easily affected by heat. However, efficient heat dissipation is also required to prevent heat from being transmitted to the laser light source 5 side.

The light emitted from the laser light source 5 has high directivity. So in order to get noodles The light source device emits light uniformly, and the laser light source 5 requires higher position accuracy. The laser light source 5 generally used is a cylindrical package having a diameter of about 6 mm. The laser light source 5 presses the package into a hole 23 in the mounting portion 22 of the heat sink 2 and fixes it. The light emitting side of the laser light source 5 from the laser light 51 is pressed into a hole 23 in the mounting portion 22 of the heat sink 2.

The heat sink 2 after the laser light source 5 is pressed into the mounting portion 22 is mounted on the back portion 1. At this time, the heat radiation fins 21 and the base plate portion 24 need to protrude from the outer side surface (-Z axis direction) of the back surface portion 1. The mounting portion 22 is inserted into the mounting hole 14 opened in the back surface portion 1 from the back surface side (-Z axis direction side) of the back surface portion 1 and fixed.

A heat-insulating portion 15 is provided between the base plate portion 24 and the back surface portion 1. Here, the thermal conductivity of the “heat-cutting portion” can be significantly lower than the thermal conductivity of the back surface portion 1 and the heat radiation portion 2. For example, the thermal cutoff portion 15 is a resin material or a rubber material. The thermal insulation section 15 may be an air layer. The thickness of the air layer is desirably about several mm. When the heat insulation part 15 is an air layer, it is desirable to provide an opening part on the upper side (+ Y-axis side) so that the air in the air layer can rise after warming. In addition, it is also desirable to provide an opening portion on the lower side (-Y axis side) so that low-temperature air can flow from the lower side (-Y axis side) to the heat insulation portion. In the thermal insulation section 15 shown in FIG. 4, low-temperature air flows in from the X-axis direction, and warmed air rises in the + Y-axis direction.

The heat-insulating portion 15 may be added between the base plate portion 24 and the back surface portion 1, for example, between the mounting portion 22 and the back surface portion 1. For example, when the distance between the mounting portion 22 and the LED light source array 3 a is short, it is possible to make it difficult for the heat of the LED light source that is not easily affected by heat to be transmitted to the laser light source that is easily affected by heat. In this case, the heat emitted from the laser light source 5 is transferred from the mounting portion 22 to the base plate portion 24 and is then radiated from the heat radiation fin 21.

FIG. 4 is a structural diagram of the liquid crystal display device 100 as viewed from the −X axis direction. FIG. 4 is a structural diagram of cutting the liquid crystal display device 100 in the Y-Z plane at the position of the laser light source 5. The liquid crystal display element 13, the optical sheet 12, the diffusion plate 11, and the light guide rod 10 are arranged parallel to the X-Y plane. These constituent elements 10, 11, 12, and 13 are arranged in the order of the liquid crystal display element 13, the optical sheet 12, the diffusion plate 11, and the light guide rod 10 from the + Z axis direction to the −Z axis direction.

LED light source arrays 3a, 3b, 3c, 3d, 3e, 3f are arranged on the -Z axis side of the light guide rod 10. The LED light source arrays 3 a, 3 b, 3 c, 3 d, 3 e, and 3 f are arranged on the surface on the + Z axis direction side of the back surface portion 1. The reflecting portion 8 has a box shape having an opening in the + Z axis direction. An LED light source array 3 and a light guide rod 10 are arranged inside the box shape of the reflection portion 8. The bottom plate portion 82 of the reflection portion 8 is formed with a plurality of holes in accordance with the shape of the LED light source 4. The LED light source 4 is inserted into the hole of the reflection portion 8 from the −Z axis direction. Since the reflecting portion 8 is thin, the LED light source 4 is arranged in a state of protruding from the hole in the + Z axis direction. The reflection portion 8 may be made of a plate-like member. Therefore, the side plate portions 81a, 81b, 81c, and 81d and the bottom plate portion 82 include shapes having extremely thin sheet shapes to plate shapes.

FIG. 5 is a perspective view of the structure of the surface light source device 200. FIG. 5 is a perspective view viewed from the display surface side of the liquid crystal display element 13. In FIG. 5, the liquid crystal display element 13, the optical sheet 12, and the diffusion plate 11 of the liquid crystal display device 100 are removed. The reflecting plate 8 has a sheet shape, and as shown in FIG. 5, the box shape has four sides extending upward at 90 degrees. That is, the reflection plate 8 includes side plate portions 81a, 81b, 81c, and 81d extending from the four sides of the bottom plate portion 82 in the + Z-axis direction. The box-shaped inner surface of the reflecting portion 8 is a reflecting surface. The light emitting point of the LED light source 4 is arranged on a surface in the + Z axis direction of the reflecting portion 8. The LED light 41 of the LED light source 4 is emitted toward the liquid crystal display element 13.

Incident of the laser light 51 is provided on the -Y axis direction side of the light guide rod 10 面 101。 Surface 101. The light guide rod 10 has a rod shape. The incident surface 101 is a rod-shaped one end surface. A reflection sheet 9 is attached to an end surface of the light guide rod 10 on the + Y-axis direction side. The plane to which the reflection sheet 9 is attached is the other end surface having a rod shape opposite to the incident surface. Both ends of the light guide rod 10 pass through holes provided in the side plate portions 81a and 81b. The light guide rod 10 is held by the reflection portion 8. Since the reflecting plate 8 is made of a sheet-like member, the light guide rod 10 can also be held on other members. In addition, as described above, the reflecting portion 8 may be made of a plate-like member sufficient to hold the light guide plate 10.

A laser light source 5 is disposed on the -Y axis direction side of the light guide rod 10. The laser light source 5 is arranged facing the incident surface 101. The laser light 51 emitted from the laser light source 5 passes through the incident surface 101 on the −Y-axis direction side of the light guide rod 10 and enters the light guide rod 10.

The laser light 51 emitted from the laser light source 5 enters the inside of the light guide rod 10 from the incident surface 101. The incident laser light 51 is repeatedly reflected inside the light guide rod 10 and advances in the + Y-axis direction. A part of the reflected laser light 51 is emitted from the side of the light guide rod 10 to the outside. The laser light 51 immediately after being emitted from the laser light source 5 is point light. However, while the laser light 51 is advancing inside the light guide rod 10, a part of the laser light 51 is emitted from the side, whereby the laser light 51 is changed from point light to linear light. When the light guide rod is thick, the laser light 51 is converted into rod-shaped light.

A "point light source" is a light source that emits light from only one point. Here, "a point" still has a certain degree of area, which can be treated as a point under optical calculation without causing problems in consideration of the performance of the product. Therefore, a backlight device using a laser as a light source requires an optical element that converts laser light from a point light source into a surface light source. This surface light source is a light source that illuminates the liquid crystal display element 13 with a uniform intensity.

Laser light 51 as rod-shaped light and LED light arranged in an array The LED light 41 emitted from the source 4 is also emitted to the inside of the reflection portion 8 together. "Array-like" refers to a state in which many elements are arranged side by side. Here, “the LED light sources 4 arranged in an array” means the LED light source array 3 in which the LED light sources 4 are arranged. The LED light 41 and the laser light 51 that are repeatedly reflected inside the reflection section 8 enter the diffusion plate 11.

The laser light 51 emitted from the light guide rod 10 is emitted in all directions with the Y axis as the central axis. The omnidirectional direction refers to a 360-degree direction. Therefore, the light emitted in the + Z axis direction enters the diffusion plate 11. On the other hand, light emitted in the -Z axis direction is reflected by the bottom plate portion 82 of the reflection portion 8 and enters the diffusion plate 11. The laser light 51 emitted toward the X-Y plane is reflected by the side plate portions 81 a, 81 b, 81 c, and 81 d extending upward on the four sides of the reflection portion 8 and enters the diffusion plate 11.

The laser light 51 and the LED light 41 are converted into planar light and enter the diffusion plate 11. The diffusion plate 11 further uniformizes the laser light 51 and the LED light 41. The laser light 51 and the LED light 41 are emitted toward the optical sheet 12 and the liquid crystal display element 13 as white planar light uniformized by the diffusion plate 11.

The reflecting portion 8 and the light guiding rod 10 are light guiding portions 30 that convert the laser light 51 that is point light when emitted from the laser light source 5 into planar light. The light guide rod 10 converts the laser light 51 from a point light into a linear light (rod light). The reflection unit 8 converts the laser light 51 from linear light (rod light) to planar light. Therefore, as a method of converting the laser light 51 into planar light, a side-light type light guide plate can also be used. In this case, the laser light 51 is converted into planar light by a side-light type light guide plate. The LED light 41 is converted into planar light by the LED light sources 4 arranged in a direct type. The side light type light guide plate is disposed on the light emitting surface side of the surface light source device with respect to the LED light source 4.

The method of making a side-light type light guide plate is, for example, a screen printing method in which white dots are used to print reflection dots on an acrylic plate, and an acrylic plate is provided with irregularities. Structure forming method, point-type adhesive material sticking to acrylic plate and reflective plate, point-of-adhesion method, groove processing method, etc. The light emitted from the light source is incident from the side of the light guide plate. The light incident on the light guide plate is reflected repeatedly on the ground surface and spreads out on a wide plane of the light guide plate. At this time, if there is a reflection point or the like, light is scattered and emitted outward from the surface of the light guide plate. The area of the light guide plate near the reflection point of the light source is small, and the area farther from the light source reflection point is larger. Thereby, the light guide plate can form uniform planar light.

However, the surface light source device 200 using the reflection portion 8 and the light guide rod 10 described in the first embodiment can generate the light with a simple structure because the laser light 51 and the LED light 41 are mixed inside the case of the reflection portion 8. Planar light with high uniformity.

6 is a structural view of the liquid crystal display device 100 as viewed from the −X axis direction, similarly to FIG. 4. FIG. 6 excludes the liquid crystal display element 13, the optical sheet 12, and the diffusion plate 11. That is, FIG. 6 shows only a part of the surface light source device 200 in the liquid crystal display device 100. FIG. 6 is a structural diagram of cutting the liquid crystal display device 100 in the Y-Z plane at the position of the laser light source 5.

FIG. 6 illustrates the flow of heat generated by the LED light source 4 and the flow of heat generated by the laser light source 5. The liquid crystal display element 13 is mainly composed of glass. The diffusion plate 11, the optical sheet 12, and the reflection portion 8 are mainly made of resin. These materials made of resin or glass have low thermal conductivity.

The LED light source 4 is provided with a reflecting portion 8 having a low thermal conductivity in the + Z axis direction. Therefore, the heat generated by the LED light source 4 is not easily transmitted to the + Z axis direction. On the other hand, in the -Z axis direction of the LED light source 4, a back surface portion 1 having high thermal conductivity is arranged. Therefore, the heat generated by the LED light source 4 is easily transmitted to the -Z axis direction. As described above, it is relatively difficult for the heat generated by the LED light source 4 to flow through the reflecting portion 8 to the + Z axis direction. This is FIG. 6 except that the liquid crystal display element 13, the optical film 12, the diffusion plate 11, and the reflection portion 8 are removed. Reason.

In the liquid crystal display device 100 using two types of light sources, the output of the light 41 and 51 of each of the light sources 4 and 5 is optimized so that the light output is white. For example, when the total radiation beam of the laser light 51 emitted from the laser light source 5 is 1W, the total radiation beam of the LED light 41 emitted from the LED light source 4 must be about 3W. Thereby, the light mixed with the laser light 51 and the LED light 41 becomes white. At this time, according to the respective electro-optical conversion efficiencies of the laser light source 5 and the LED light source 4, if the temperature of each of the light sources 4, 5 is about room temperature (about 30 degrees), the calorific value is equivalent to about 3W. In order to increase the brightness of the display screen, if the radiation beams emitted from the light sources 4 and 5 are increased, the heat generation of the light sources 4 and 5 will also increase accordingly. However, even if the amount of heat generated by the light sources 4 and 5 is increased, if the light sources 4 and 5 can be sufficiently radiated, the temperature change of the elements of each of the light sources 4 and 5 will be reduced, and the amount of heat generated will not change significantly. In other words, the amount of heat generated by the laser light source 5 and the amount of heat generated by the LED light source 4 are approximately 3W. Conversely, if the heat radiation of the light sources 4 and 5 is insufficient, the temperature of the elements of each of the light sources 4 and 5 increases, and the electro-optical conversion efficiency decreases. As a result, the amount of heat generated by each of the light sources 4 and 5 increases, and a vicious cycle in which the temperature of each of the light sources 4 and 5 gradually rises is caused. In other words, in order not to cause problems caused by heat, it is necessary to accurately estimate the ambient temperature used by the device and the amount of heat generated at the ambient temperature, and to provide a suitable and efficient heat dissipation function.

The heat 18 generated by the laser light source 5 is transmitted from the mounting portion 22 of the heat sink 2 to the base plate portion 24 and then to the heat radiation fins 21 and is released to the surrounding air 16. The heat sink 2 is disposed on the bottommost surface side (-Y axis side) of the liquid crystal display device 100. The heat radiating fin 21 emits heat 18 from the surrounding air 16 to the + Y axis direction. This is because the air 16 which receives the heat 18 from the heat radiation fin 21 rises lighter than the surrounding air. Therefore, the cooling fin 21 has a fresh air flow from the -Y axis direction or the -Z axis direction. Into. “Fresh air” means air that does not receive heat 18 from the heat dissipation fins 21 or heat 17 from the back surface portion 1. The amount of heat transfer from the solid surface to the air will increase as the temperature difference between the solid surface and air increases. That is, the lower the temperature of the air flowing into the radiator 2, the more efficiently the radiator 18 can release the heat 18. In addition, the heat 18 generated by the laser light source 5 can also be efficiently released into the surrounding air 16.

On the other hand, each of the LED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f is mounted on the back surface portion 1. The heat 17 generated by the LED light source 4 is transmitted to the respective substrates of the light source arrays 3a, 3b, 3c, 3d, 3e, and 3f, and then is transmitted to the back surface portion 1. The thickness of the back surface portion 1 is about 2 mm. Since the cross-sectional area of the back surface portion 1 is small, the heat transmitted to the back surface portion 1 is not easily transmitted in the X-Y plane direction.

The LED light source arrays 3b, 3c, 3d, 3e, and 3f are arranged away from the heat sink 2. Therefore, most of the heat 17 of the LED light source arrays 3b, 3c, 3d, 3e, and 3f is released into the air from the surface of the back surface side (the -Z axis direction side) of the back surface portion 1.

Here, the heat 17 emitted from the LED light source array 3a near the heat sink 2 will be discussed. The LED light source array 3 a is arranged in the + Y-axis direction of the heat sink 2. Therefore, the heat 17 emitted from the LED light source array 3 a is not easily transmitted to the heat sink 2. The first reason is that the cross-sectional area of the back surface portion 1 is small, and therefore the heat 17 transmitted to the back surface portion 1 is not easily transmitted in the X-Y plane direction. The second reason is that the heat 17 released into the air from the back surface portion 1 rises as described above and moves in the + Y-axis direction. The third reason is that there is a thermal break 15 between the base plate portion 24 and the back surface portion 1 of the heat sink 2.

The heat sink 2 is disposed below the LED light source 3a (-Y-axis direction side). That is, the back surface (the surface on the -Z axis side) of the back surface portion 1 of the portion where the LED light source array 3a is mounted directly contacts the heat sink 18 and rises Coming air 16. Therefore, the heat 17 emitted from the LED light source arrays 3a, 3b, 3c, 3d, 3e, and 3f into the air is released from the back surface portion 1 to the air 16. Here, the air 16 is air that has risen after receiving heat 18 from the radiator 2.

The warmed air 16 rises as it receives heat 18 from the radiating fins 21 of the heat sink 2. The LED light source 4 is disposed above the heat sink 2 (+ Y-axis direction). Therefore, the heat 17 emitted from the LED light source 4 is released from the back surface portion 1 to the air 16 warmed by the heat radiation fins 21. In other words, the cooling performance of the LED light source 4 decreases as it goes upward (+ Y-axis direction).

However, the LED light source 4 has better thermal characteristics (thermal characteristics) than the laser light source 5. Therefore, the LED light source 4 has a large tolerance for temperature, and can be designed within a range that does not cause a problem in quality.

In contrast, the laser light source 5 has worse thermal characteristics than the LED light source 4. "Poor thermal characteristics" means that the tolerance to temperature is low. The heat sink 2 is disposed on the bottommost surface side (-Y axis side) of the liquid crystal display device 100. Therefore, fresh air will flow into the heat dissipation fins 21. “Fresh air” means air that does not receive heat 18 from the heat dissipation fins 21 or heat 17 from the back surface portion 1. The amount of heat transfer from the solid surface to the air will increase as the temperature difference between the solid surface and air increases. That is, the lower the temperature of the air flowing into the radiator 2, the more efficiently the radiator 18 can release the heat 18. In addition, the heat 18 generated by the laser light source 5 can also be efficiently released into the surrounding air 16.

The liquid crystal display device 100 includes a laser light source 5, an LED light source 4, and a heat sink 2. The laser light source 5 emits laser light 51. The LED light source 4 emits LED light 41. The heat sink 2 holds the laser light source 5 and at the same time transfers heat generated by the laser light source 5 to the air. The laser light source 5 is disposed below the LED light source 4.

The liquid crystal display device 100 includes a light guide unit 30. The light guide unit 30 enters the laser light 51 from the incident end portion, converts it into planar light, and emits it. The laser light 51 and the LED light 41 emitted from the light guide 30 are emitted from the opening 83. The LED light source 4 includes a plurality of LED light sources 4 and is arranged two-dimensionally toward the opening 83. The opening portion 83 functions as a light exit surface. That is, the light exit surface is an imaginary surface that hits the opening 30f. The incident end portion is the incident surface 101 in the first embodiment. When an edge-light type light guide plate as described above is used, it is the side where light is incident.

The light guide section 30 includes a light guide rod 10 and a reflection section 8. The light guide rod 10 has an incident surface 101, and converts the aforementioned laser light 51 into linear light and emits the same. The reflection section 8 converts the laser light 51 emitted from the light guide rod 10 into planar light. The LED light source 4 is disposed on a surface facing the opening portion 83 of the reflection portion 8. The light guide unit 30 mixes the laser light 51 converted into the planar light with the LED light 41 and outputs the mixed light. The incident surface 101 is an incident end portion. The opening portion 83 functions as a light exit surface.

As described above, the invention described in Embodiment 1 can realize a wide color reproduction range by using a red laser light emitting element as a light source. In contrast, the invention described in Embodiment 1 can provide a backlight device having a structure that makes it difficult for the heat of the LED light source that is not easily affected by heat to be transmitted toward the laser light source that is easily affected by heat.

Example 2

FIG. 7 is a rear perspective view of a liquid crystal display device 102 according to Embodiment 2 of the present invention. The difference from the liquid crystal display device 100 of the first embodiment shown in FIG. 1 is the heat sinks 2a, 2b, 2c, 2d, and 2e, which are arranged inside the horizontal direction (X-axis direction). The scattering area is larger than the radiation area of the heat sinks 2a and 2e arranged on the outer side in the horizontal direction.

Except for the differences, the second embodiment is the same as the first embodiment. In other words, the rear portion 1, the heat-dissipating portion 15, the LED light source array 3, the LED light source 4, the laser light source 5, the reflection portion 8, the reflection sheet 9, the light guide rod 10, the diffusion plate 11, the optical sheet 12, the liquid crystal display Structures other than the heat radiation area of the element 13 and the heat sink 2 are the same as those of the first embodiment.

For example, in the example of FIG. 7, there are 14 radiating fins 21 of the heat sinks 2 a and 2 e located on the outer side in the horizontal direction. However, there are 15 radiating fins of the heat sinks 2b and 2d arranged inside the heat sinks 2a and 2e. There are 18 heat radiating fins 21 on the innermost heat radiating fin 2c. In this way, the closer the heat sink 2 is arranged to the inside, the larger the number of the heat radiation fins 21, and the heat radiation area increases.

In the liquid crystal display device 102, peripheral elements such as a timing controller circuit substrate for a liquid crystal drive, a driving power source substrate, and a video signal processing circuit substrate are arranged at a peripheral element placement position 19 on the rear portion 1. In FIGS. 7 and 8, the peripheral element arrangement position 19 is indicated by a dotted line.

The arrangement position 19 of these peripheral elements is determined according to the wiring length of the signal line, the design of the liquid crystal display device 102, and the position of the center of gravity of each element. However, the peripheral elements are usually concentrated at the center of the back surface portion 1. Most peripheral components generate heat. Peripheral components are mounted with relatively high height components such as electrolytic capacitors, LSIs with high heat generation, and heat sinks for switching elements. In other words, heat is generated at the peripheral element arrangement position 19, and parts with a relatively high height are mounted.

FIG. 8 is a configuration diagram of the liquid crystal display device 102 viewed from the −X axis direction. FIG. 8 is a structural diagram of the liquid crystal display device 102 cut in the Y-Z plane at the position of the laser light source 5 including the peripheral element arrangement position 19. The difference from the structure of the liquid crystal display device 100 shown in FIG. 6 is that a peripheral element arrangement position is added. 19. The structure of the liquid crystal display device 100 is different from that of the liquid crystal display device 100 shown in FIG. 6 in that a turbulent flow 20 of airflow is generated below the peripheral element placement position 19 (-Y axis direction).

The warmed external air 16 receives heat 18 from the radiating fins 21 of the heat sink 2 and rises in the + Y-axis direction. However, the arrangement of peripheral elements above the heat sink 2 (+ Y-axis direction) obstructs the flow path. In this case, the updraft is blocked, and a turbulent flow 20 of airflow such as a vortex is generated.

When the turbulent flow 20 of the air flow is generated, the pressure loss in the flow path increases, and the flow velocity of the air 16 flowing through the radiator 2 decreases. As a result, the heat radiation amount of the heat radiation fins 21 to the air 16 is reduced. That is, when the peripheral elements are arranged above the heat sink 2 (+ Y-axis direction) hinder the flow path, the heat dissipation capabilities of the heat sinks 2b, 2c, and 2d arranged below the peripheral elements (-Y-axis direction) are compared with There is no heat dissipation capability of the heat sinks 2a, 2e provided with peripheral elements above (+ Y-axis direction), and the heat dissipation capability per unit of heat dissipation area is low.

Many of the peripheral elements arranged at the peripheral element arrangement position 19 generate heat. When the liquid crystal display device 102 is used as a general product, it is usually stored in a resin case or the like. Therefore, the air 16 in the horizontal central portion and the back surface portion 1 in the horizontal central portion where the heat source is concentrated and the heat flux density increases are higher in temperature than the peripheral portions. "Heat flux density" simply refers to the amount of heat flux per unit volume.

A heat-insulating portion 15 is provided between the heat sink 2 and the back surface portion 1. The heat interruption portion 15 can prevent heat conduction from the back surface portion 1 to the heat sink 2. However, heat radiation and the like from the back surface portion 1 cannot be prevented. The heat sinks 2b, 2c, and 2d are subjected to radiant heat from peripheral elements, and their temperature rises. Therefore, the heat sinks 2b, 2c, and The temperature of the heat radiating fins 2d of 2d is higher than the temperature of the heat radiating fins 21 of the heat radiating gases 2a and 2e arranged in the horizontal peripheral portion. The amount of heat transfer from the solid surface to the air will increase as the difference between the temperature of the solid surface and the temperature of the air increases. Therefore, even if the outside air 16 having the same temperature flows into the radiating fins 21 of the radiator 2, the heat dissipating capacity of the radiators 2b, 2c, and 2d disposed in the horizontal central portion is greater than that of the heat radiating gas 2a, 2e disposed in the horizontal peripheral portion. The heat-dissipating fin 21 has a poor heat-dissipating capability.

Here, when the heat sinks 2a, 2b, 2c, 2d, and 2e are arranged near the lower side in the Y-axis direction of the back portion 1, the heat sinks 2b, 2c, which are arranged inside the horizontal direction (X-axis direction) The heat radiation area of 2d is larger than the heat radiation area of the heat sinks 2a and 2e arrange | positioned on the outer side in a horizontal direction. Thereby, the heat radiation ability of the heat sinks 2b, 2c, and 2d arrange | positioned inside the horizontal direction is improved. That is, the heat sink 2 can efficiently release the heat 18 generated by the laser light source 5 into the air 16 without relying on the position where the laser light source 5 is arranged.

Here, the method of increasing the heat radiation area has been described as an example of increasing the number of heat radiation fins 21. However, the size of the heat dissipation fins 21 can also be increased to increase the heat dissipation area. This time, the heat radiation area of the innermost heat sink 2c among the heat sinks 2b, 2c, and 2d arranged below (-Y axis direction) the peripheral element placement position 19 is maximized. However, the size of the heat radiation area of the heat sinks 2b and 2d may be the same as the size of the heat radiation area of the heat sink 2c according to the condition of the arrangement of the peripheral elements.

A plurality of laser light sources 5 are arranged along the incident end. Among the arrayed laser light sources 5, the heat radiation capability of the heat sink 2 of the laser light source 5 located at both end portions is smaller than that of the heat sink 2 of the laser light source 5 sandwiched between the two end portions. The incident end is a plurality of light guide rods 10 arranged in the X-axis direction in Example 1. The incidence surface 101. A plurality of incident surfaces 101 are arranged in the X-axis direction, and the laser light source 5 is arranged facing the incident surface 101. On the other hand, in the case of using the above-mentioned side-light type light guide plate, the incident surface is the side where the light is incident.

In each of the above-mentioned embodiments, terms such as "center", "horizontal", or "vertical" are used to indicate the positional relationship of the elements or terms to indicate the shape of the elements. These terms cover the range from manufacturing tolerances to assembly tolerances.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments.

1‧‧‧ back

2‧‧‧ radiator

3, 3a, 3b, 3c, 3d, 3e, 3f‧‧‧LED light source array

4‧‧‧LED light source

41‧‧‧LED light

5‧‧‧laser light source

51‧‧‧laser light

8‧‧‧Reflection

9‧‧‧Reflector

10‧‧‧light guide

11‧‧‧ diffuser

12‧‧‧ Optical Sheet

13‧‧‧LCD display element

15‧‧‧Insulation

22‧‧‧Mounting Department

24‧‧‧ base plate

30‧‧‧light guide

83‧‧‧ opening

100‧‧‧LCD display device

101‧‧‧incident face

Claims (6)

A surface light source device that emits planar light toward a predetermined emission direction includes: a laser light source that emits laser light; an LED light source that emits LED light; a radiator that holds the laser light source and generates the light from the laser light source. The heat is transmitted to the air; and the light guide part, the laser light is incident from the incident end, converted into planar light, and then emitted from the light emitting surface. If the upward direction of the warmed air is determined as the upper side, the laser The light source is disposed at a lower position than the LED light source, the LED light is emitted from the light emitting surface, the LED light source has a plurality and is arranged two-dimensionally toward the light emitting surface, and the laser light source has a plurality of and follows The incident end portions are aligned, and the heat dissipation capability of the heat sink of the laser light source at the two ends of the arrayed laser light sources is smaller than that of the heat sink of the laser light source located between the two end portions. . The surface light source device according to item 1 of the scope of patent application, wherein the light guiding portion includes: a light guiding rod having the incident end portion and converting the laser light into linear light and emitting; and a reflecting portion, which guides the light The laser light emitted from the rod is converted into planar light, wherein the LED light source is disposed on a surface facing the light exit surface of the reflection portion, and the light guide portion mixes the laser light converted into planar light and the LED light afterwards Out. The surface light source device according to item 1 of the scope of patent application, further comprising: a heat-dissipating portion, disposed between the heat sink and the LED light source. The surface light source device according to item 3 of the scope of application for a patent, wherein the heat insulation portion is an air layer. The surface light source device according to item 3 of the scope of application for a patent, wherein the heat insulation portion is a resin material or a rubber material. A liquid crystal display device includes the surface light source device according to any one of claims 1 to 5 of the scope of patent application; and a liquid crystal display element that makes the planar light emitted by the surface light source device incident to form image light.