WO2014020870A1

WO2014020870A1 - Liquid crystal display

Info

Publication number: WO2014020870A1
Application number: PCT/JP2013/004521
Authority: WO
Inventors: 長瀬　章裕; 哲也永安; 栄二新倉
Original assignee: 三菱電機株式会社
Priority date: 2012-07-31
Filing date: 2013-07-25
Publication date: 2014-02-06
Also published as: JPWO2014020870A1; CN104487763A; JP5931199B2; TW201426129A; TWI612361B; CN104487763B

Abstract

A liquid crystal display (100) is provided with a laser light source (5), an LED light source (4), and a radiator (2). The laser light source (5) emits laser light (51). The LED light source (4) emits LED light (41). The radiator (2) holds the laser light source (5), and transmits heat produced by the laser light source (5) and releases said heat in the air. The laser light source (5) is positioned lower than the LED light source (4). The liquid crystal display (100) prevents heat from the LED light source (4), which is not easily affected by heat, from being transferred to the laser light source (5), which is easily affected by heat.

Description

Liquid crystal display

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

The liquid crystal display element included in the liquid crystal display device does not emit light by itself. For this reason, the liquid crystal display device includes a backlight device on the back surface of the liquid crystal display element as a light source for illuminating the liquid crystal display element. The liquid crystal display element receives light emitted from the backlight device and emits image light. In recent years, as the performance of blue light-emitting diodes (hereinafter referred to as LEDs (Light Emitting Diodes)) has dramatically improved, backlight devices using blue LEDs as light sources have been widely adopted.

The light source using the blue LED has, as constituent elements, a blue LED element and a phosphor that absorbs light emitted from the blue LED element and emits light having a blue complementary color. Such an LED is called a white LED. The blue complementary color is a yellow color including green and red.

White LEDs have high electro-optical conversion efficiency and are effective in reducing power consumption. “Electric-optical conversion” means conversion from electricity to light. However, on the other hand, white LEDs have the problem that their wavelength bandwidth is wide and the color reproduction range is narrow. The liquid crystal display device includes a color filter inside the liquid crystal display element. The liquid crystal display device uses this color filter to extract only the red, green, and blue spectral ranges and perform color expression. A light source having a continuous spectrum with a wide wavelength bandwidth such as a white LED needs to increase the color purity of the display color of the color filter in order to widen the color reproduction range. That is, the wavelength band that transmits the color filter is set narrow. However, if the wavelength band that passes through the color filter is set narrow, the light utilization efficiency decreases. This is because the amount of unnecessary light that is not used for image display of the liquid crystal display element increases. Further, there arises a problem that the brightness of the display surface of the liquid crystal display element is lowered and further the power consumption of the liquid crystal display device is increased.

As a measure for improving such a problem, a backlight device that employs a single color LED with higher color purity instead of a white LED has been proposed. The colors of the single color LED are red, green and blue. In addition, a backlight device using a laser having higher color purity than a single color LED has been proposed. The laser colors are red, green and blue. “High color purity” means a narrow wavelength width and excellent monochromaticity. By adopting these light sources in the backlight device, the color reproduction range of the liquid crystal display device can be expanded.

However, in some light sources composed of three primary color single-color LEDs or three primary color lasers, the electro-optical conversion efficiency decreases significantly as the element temperature increases. In particular, when a red laser continues to emit high-power light at a high temperature, the deterioration is accelerated and the lifetime of the element is shortened. Therefore, in order to obtain a desired light amount even when the environmental temperature is high, a heat dissipation mechanism is generally required. The “ambient temperature” includes the ambient temperature where the liquid crystal display device is placed and the ambient temperature of the backlight device in the liquid crystal display device where the backlight device is placed.

Patent Document 1 shows a liquid crystal display device 1 in which LED modules 9 as light sources are arranged 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 attached to the rising portion 8 of the back frame 7 (paragraph 0009, FIG. 2). The heat sink 27 is attached in thermal contact with almost the entire back side of the back frame 7 (FIG. 1). The heat sink 27 is not attached to the LED drive power supply 31 and the control board 29. The liquid crystal display panel is a liquid crystal display element.

JP 2006-267936 (paragraph 0009, paragraph 0012, FIGS. 1 and 2)

However, for example, in the case of a backlight device that employs two types of light sources in combination with a direct type and an edge light type, it is conceivable that the heat of each light source is transmitted to the light source on the other side. A “direct type” is a backlight device in which light sources are arranged side by side on the back side of a liquid crystal panel. The “edge light type” is a backlight device in which light sources are arranged in a line on the end surface of the liquid crystal panel and light is spread over the entire back side of the panel using a light guide plate. For this reason, when a light source that is easily affected by heat is employed, the temperature of the light source that is easily affected by heat rises depending on the arrangement of the two types of light sources.

The present invention has been made in view of the above, and an object of the present invention is to obtain a liquid crystal display device configured to suppress the heat of a light source that is not easily affected by heat from being transmitted to the light source that is easily affected by heat. And

The present invention has been made in view of the above, and the liquid crystal display device includes a laser light source that emits laser light, an LED light source that emits LED light, and the laser light source while holding the laser light source. And a heat radiator that transmits heat to be released into the air, and the laser light source is disposed below the LED light source.

∙ Suppresses the transfer of heat from a light source that is less susceptible to heat to a light source that is more susceptible to heat.

1 is a perspective view illustrating a configuration of a liquid crystal display device according to a first embodiment. 3 is a partial perspective view illustrating a configuration of a liquid crystal display device according to Embodiment 1. FIG. FIG. 3 is a perspective view illustrating a configuration of a radiator according to the first embodiment. 1 is a configuration diagram illustrating a configuration of a liquid crystal display device according to a first embodiment. It is a perspective view which shows the structure of the surface light source device of Embodiment 1. FIG. 1 is a configuration diagram illustrating a configuration of a liquid crystal display device according to a first embodiment. FIG. 6 is a perspective view illustrating a configuration of a liquid crystal display device according to a second embodiment. FIG. 6 is a configuration diagram illustrating a configuration of a liquid crystal display device according to a second embodiment.

Embodiment 1 FIG.
Hereinafter, in order to facilitate the explanation of the drawings, the coordinate axes of the XYZ orthogonal coordinate system are shown in the respective drawings. The short side direction of the liquid crystal display device 100 is defined as the Y-axis direction, the long side direction is defined as the X-axis direction, and the direction perpendicular to the XY plane is defined as the Z-axis direction. The display surface side of the liquid crystal display device 100 is defined as the + Z-axis direction. The upward direction of the liquid crystal display device is defined as the + Y axis direction. The left side when viewing the display surface of the liquid crystal display device 100 is defined as the + X-axis direction. “Look at the display surface” means to face the display surface.

FIG. 1 is a rear perspective view of the liquid crystal display device 100 according to the first embodiment of the present invention. The back surface portion 1 is a holding member disposed on the back side of the liquid crystal display device 100. For example, the back surface portion 1 is a plate material. For example, the back surface portion 1 is formed by pressing iron. In Embodiment 1, the back part is described as a back sheet metal. Therefore, the back portion is a member having a heat dissipation effect. The

radiators

2a, 2b, 2c, 2d, and 2e are disposed on the back side (−Z-axis direction side) of the back surface portion 1. The

radiators

2a, 2b, 2c, 2d, and 2e are disposed at the lower end portion in the Y-axis direction of the back surface portion 1. The heat radiator 2 a and the heat radiator 2 e are disposed symmetrically on the back surface of the back surface portion 1. The heat radiator 2 a and the heat radiator 2 e are disposed at both ends in the X direction on the back surface of the back surface portion 1. The radiator 2b and the radiator 2d are arranged symmetrically on the back surface of the back surface portion 1. The heat radiator 2 c is disposed at the center in the X-axis direction on the back surface of the back surface portion 1. The radiator 2b is disposed between the radiator 2a and the radiator 2c. The radiator 2d is disposed between the radiator 2e and the radiator 2c. The air paths of the

radiators

2a, 2b, 2c, 2d, and 2e are provided in the vertical direction (+ Y-axis direction). An “airway” is one that creates a path for the wind and releases heat.

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. In FIG. 2, the liquid crystal display element 13, the optical sheet 12, the diffusion plate 11, the light guide bar 10, and the first reflection unit 8 are removed. In FIG. 2, the positions where the

radiators

2 a, 2 b, 2 c, 2 d, and 2 e arranged on the back side (−Z axis direction side) of the back part 1 are shown by broken lines.

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

The LED

light source arrays

3a, 3b, 3c, 3d, 3e, and 3f are obtained by arranging a plurality of LED light sources 4 in a line on a substrate. The substrate on which the LED light sources 4 are arranged has an elongated rectangular shape. 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

3a, 3b, 3c, 3d, 3e, and 3f 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, a plurality of LED

light source arrays

3a, 3b, 3c, 3d, 3e, and 3f are arranged at equal intervals in the vertical direction (+ Y-axis direction). Thus, the LED light source 4 has a “directly-type” configuration arranged two-dimensionally on the back side of the liquid crystal display element 13.

The LED

light source arrays

3a, 3b, 3c, 3d, 3e, and 3f may 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 rectangular shape elongated 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 of pieces. For example, the LED light source array 3a may be divided into two at the central portion in the X-axis direction. Furthermore, the number of LED

light source arrays

3a, 3b, 3c, 3d, 3e, 3f is not limited to six. The number of LED

light source arrays

3a, 3b, 3c, 3d, 3e, and 3f can be set to other numbers according to the size of the liquid crystal display element 13, for example. Further, the number of

radiators

2a, 2b, 2c, 2d, and 2e is not limited to six. The number of

radiators

2 a, 2 b, 2 c, 2 d, 2 e can be set to other numbers depending on the size of the liquid crystal display element 13, for example.

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

Further, a mounting portion 22 is formed at the lower end (−Y-axis direction) of the radiator 2. The attachment portion 22 has a plate shape protruding in the + Z-axis direction. The attachment portion 22 has a plate shape parallel to the ZX plane. The attachment portion 22 is a portion to which the laser light source 5 is attached. A hole 23 is formed in the attachment portion 22. The hole 23 penetrates the attachment portion 22 and is opened in the Y-axis direction. The laser light source 5 is attached to the hole 23 so that the light beam is emitted in the + Y-axis direction. That is, the laser light source 5 is installed in the hole 23. The light emission direction of the laser light source 5 is directed to the + Y axis direction.

In FIG. 3, the attachment portion 22 has a rectangular shape, but is not limited thereto. The attachment portion 22 may have another shape such as an arc shape. Further, the laser light source 5 may be attached to the hole 23 so that the light beam is emitted in the −Y axis direction. However, in that case, the radiation fins 21 are disposed outside the liquid crystal display element 13. For this reason, there exists a fault that the bezel part (frame part) of the liquid crystal display device 100 cannot be made thin. The “bezel” is a part of a frame-shaped cabinet that surrounds the display screen. In recent years, a design in which a portion of a frame-like cabinet surrounding the display screen is narrowed is preferred. This thin bezel is called a “narrow bezel”.

The heat generated by the laser light source 5 is transmitted from the back side (−Y axis direction side) of the laser light source 5 to the back surface portion 1. The heat of the laser light source 5 transmitted to the back surface portion 1 is transmitted to the lower end surface 25 (the surface on the −Y axis direction side) of the radiator 2. The heat transmitted to the lower end surface 25 (−Y axis direction) of the radiator 2 is transmitted to the mounting portion 22. The heat transmitted to the attachment portion 22 is transmitted to the heat radiating fins 21 and released to the outside air. The radiator 2 is attached to the back surface portion 1 such that the lower end surface 25 is in contact with the back surface portion 1.

In FIG. 3, the mounting portion 22 is formed integrally with the heat radiation fin 21. However, the attachment part 22 may be comprised by another component. However, in this case, the heat radiation performance of the attachment portion 22 is slightly lowered. However, if the mounting portion 22 is configured as a separate part, the radiator 2 can be easily manufactured, and the manufacturing cost may be reduced. In FIG. 3, one laser light source 5 is attached to one radiator 2. However, a plurality of laser light sources 5 may be attached to one radiator 2.

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

Humans are highly sensitive to red color differences. Therefore, the difference in wavelength bandwidth in red is felt as a more prominent difference in human vision. Here, the difference in wavelength bandwidth is the difference in color purity. Conventionally, a white LED used as a light source in a liquid crystal display device has a small amount of energy of a red spectrum particularly in a wavelength band from 600 nm to 700 nm. That is, if the color purity is increased in the wavelength region from 630 nm to 640 nm which is preferable as red having high purity by using a color filter having a narrow wavelength band width, the amount of transmitted light is extremely reduced and the light use efficiency is lowered. Therefore, there arises a problem that the luminance is remarkably lowered. This high purity red is called “pure red”.

On the other hand, the laser light-emitting element 5 has a narrow wavelength bandwidth, and light of high color purity can be obtained while suppressing light loss. In particular, among the three primary colors, by adopting the red laser light emitting element 5 having very high monochromaticity, a high effect can be obtained for reducing power consumption and improving color purity. Therefore, in the liquid crystal display device 100 of the first embodiment, the laser light source 5 employs a light source that emits red light.

In the red laser light source 5 of 630 nm to 640 nm, which is preferable as pure red, the electro-optical conversion efficiency decreases remarkably as the temperature of the element increases. That is, the red laser light source is a light source that is easily affected by heat. “Pure red” is a high-purity red with a narrow wavelength width and a deep red color. As the deep red color, a wavelength from 630 nm to 640 nm is preferable. Further, if the laser light source 5 continues to emit high output light in a high temperature state, the deterioration of the element is accelerated and the life is shortened. For this reason, it is necessary to introduce an efficient cooling system.

On the other hand, the change in the electro-optical conversion efficiency with respect to the temperature of the LED light source 4 is very small compared to the laser light source 5. That is, the LED light source is a light source that is not easily affected by heat. However, it is necessary to efficiently dissipate heat so that heat generation is not transmitted to the laser light source 5 side.

The light emitted from the laser light source 5 has high directivity. For this reason, in order to obtain the uniformity of light as the surface light source device, the laser light source 5 is required to have high positioning accuracy. The laser light source 5 generally used has a cylindrical package shape with a diameter of about 6 mm. The laser light source 5 is fixed by press-fitting a package into a hole 23 provided in the mounting portion 22 of the radiator 2. The laser light source 5 is press-fitted into a hole 23 provided in the attachment portion 22 of the radiator 2 from the light emitting side from which the laser light 51 is emitted.

The radiator 2 in which the laser light source 5 is press-fitted into the attachment portion 22 is attached to the back portion 1. At this time, the radiating fins 21 and the base plate portion 24 need to protrude to the outer side surface (−Z axis direction) of the back surface portion 1. The mounting portion 22 is fixed by being inserted into the mounting hole 14 formed in the back surface portion 1 from the back surface side (−Z-axis direction side) of the back surface portion 1.

Further, a heat insulating portion 15 is interposed between the base plate portion 24 and the back surface portion 1. The "thermal insulation part" here needs only to be significantly lower in thermal conductivity than the thermal conductivity of the back surface part 1 and the radiator 2. For example, the heat insulating part 15 is a resin material or a rubber material. The heat insulating part may be an air layer. The air layer is preferably about several mm. Moreover, when the heat insulation part 15 is an air layer, it is desirable to provide an opening on the upper side (+ Y-axis side) so that the air in the air layer can be warmed and raised. Also, it is desirable to provide an opening on the lower side (−Y axis side) so that low-temperature air flows into the heat insulating portion 15 from the lower side (−Y axis side). In the heat insulation part 15 shown in FIG. 4, low-temperature air flows in from the X-axis direction, and the air heated in the + Y-axis direction rises.

Further, the heat insulating portion 15 may be additionally disposed between the mounting portion 22 and the back surface portion 1 in addition to the space between the base plate portion 24 and the back surface portion 1, for example. When the distance between the mounting portion 22 and the LED light source array 3a is short, the heat of the LED light source that is not easily affected by heat can be hardly transmitted to the laser light source that is easily affected by heat. In this case, the heat generated by the laser light source 5 is transmitted from the mounting portion 22 to the base plate portion 24 and is radiated from the radiation fins 21.

FIG. 4 is a configuration diagram of the liquid crystal display device 100 as viewed from the −X axis direction. FIG. 4 is a configuration diagram in which the liquid crystal display device 100 is cut along the YZ 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 bar 10 are arranged in parallel to the XY plane. These

components

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 bar 10 from the + Z-axis direction to the -Z-axis direction.

LED

light source arrays

3a, 3b, 3c, 3d, 3e, and 3f are arranged on the −Z-axis side of the light guide bar 10. The LED

light source arrays

3a, 3b, 3c, 3d, 3e, and 3f 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. The LED light source array 3 and the light guide bar 10 are arranged inside the box shape of the reflecting portion 8. A number of holes are formed in the bottom plate portion 82 of the reflecting portion 8 in accordance with the shape of the LED light source 4. The LED light source 4 is inserted into the hole of the reflecting portion 8 from the −Z axis direction. Since the reflecting portion 8 is a thin sheet, the LED light source 4 is arranged in a state of protruding from the hole to the surface in the + Z-axis direction. In addition, the reflection part 8 can also be produced with a plate-shaped member. Therefore, the

side plate portions

81a, 81b, 81c, 81d and the bottom plate portion 82 include a thin sheet shape to a plate shape.

FIG. 5 is a perspective view showing the configuration of the surface light source device 200. FIG. 5 is a perspective view of the liquid crystal display element 13 as viewed from the display surface side. 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 reflection portion 8 is in the form of a sheet and has a box shape with four sides raised 90 degrees as shown in FIG. That is, the reflecting portion 8 has

side plate portions

81a, 81b, 81c, 81d that rise in the + Z-axis direction from the four sides of the bottom plate portion 82. 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 disposed on the surface of the reflecting portion 8 in the + Z-axis direction. Then, the LED light 41 of the LED light source 4 is emitted toward the liquid crystal display element 13.

The incident surface 101 of the laser beam 51 is provided on the −Y axis direction side of the light guide rod 10. The light guide bar 10 has a bar shape. The incident surface 101 is one end surface having a bar shape. A reflection sheet 9 is attached to the end face of the light guide bar 10 on the + Y axis direction side. The surface on which the reflection sheet 9 is affixed is the other end surface of the bar shape facing the incident surface 101. Both end portions of the light guide rod 10 are passed through holes provided in the

side plate portions

81a and 81b. The light guide bar 10 is held by the reflecting portion 8. Moreover, since the reflection part 8 is produced with the thin sheet-like member, the light guide bar 10 may be hold | maintained at another component. As described above, the reflection portion 8 may be made of a plate-like member that can hold the light guide rod 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 disposed to face the incident surface 101. The laser light 51 emitted from the laser light source 5 enters the light guide rod 10 from the incident surface 101 on the −Y axis direction side of the light guide rod 10.

The laser beam 51 emitted from the laser light source 5 enters the light guide rod 10 from the incident surface 101. The incident laser beam 51 is repeatedly reflected inside the light guide rod 10 and proceeds in the + Y-axis direction. A part of the reflected laser beam 51 is emitted from the side surface of the light guide rod 10 to the outside. The laser beam 51 immediately after being emitted from the laser light source 5 was a point light. However, the laser light 51 is changed from point light to linear light by emitting a part of the laser light 51 from the side surface while the laser light 51 travels inside the light guide rod 10. Further, when the thickness of the bar is thick, the light becomes a bar-like light.

“Point light source” is a light source that emits light from a single point. Here, “one point” means that the area of a light source is treated as a point in the optical calculation in consideration of the performance of the product and has no problem. For this reason, a backlight device using a laser as a light source requires an optical system for converting the laser light of 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 uniform intensity.

The laser light 51 that has become a rod-like light is emitted into the reflecting portion 8 together with the LED light 41 emitted from the LED light sources 4 arranged in an array. The “array form” is a state in which a large number of elements are arranged in parallel. Here, “LED light source 4 arranged in an array” indicates LED light source array 3 in which LED light sources 4 are arranged. The LED light 41 and the laser light 51 that are repeatedly reflected inside the reflecting portion 8 enter the diffusion plate 11.

The laser beam 51 emitted from the light guide rod 10 is emitted in all directions with the Y axis as the central axis. The omnidirectional direction is a direction of 360 degrees. For this reason, the light emitted in the + Z-axis direction enters the diffusion plate 11. On the other hand, the light emitted in the −Z-axis direction is incident on the diffusion plate 11 after being reflected by the bottom plate portion 82 of the reflecting portion 8. The laser beam 51 emitted in the direction on the XY plane is incident on the diffusion plate 11 after being reflected by the

side plate portions

81a, 81b, 81c, and 81d raised from the four sides of the reflection portion 8.

The laser light 51 and the LED light 41 are incident on the diffusion plate 11 as planar light. 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 from the diffusion plate 11 toward the optical sheet 12 and the liquid crystal display element 13 as a uniform white surface light.

The reflection portion 8 and the light guide rod 10 are light guide portions 30 that convert the laser light 51, which is spot-like light, into planar light when emitted from the laser light source 5. The light guide rod 10 converts the laser light 51 from dot-like light to linear light (rod-like light). Then, the reflection unit 8 converts the laser light 51 from linear light (bar-shaped light) to planar light. Therefore, a light guide plate used in an edge light type can be adopted as a method for making the laser light 51 into planar light. In this case, the laser beam 51 is converted into planar light by the edge light type light guide plate. The LED light 41 is converted into planar light by the LED light source 4 arranged in a direct type. The edge 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 edge-light type light guide plate is a silk printing method in which reflective dots are printed with white ink on an acrylic plate, a molding method with irregularities on the acrylic surface, and adhesive dots in which the acrylic plate and the reflective plate are attached with a dot-like adhesive material There are a method and a method by groove processing. The light emitted from the light source enters from the side portion of the light guide plate. The light incident on the light guide plate repeats surface reflection and spreads over a wide surface of the light guide plate. At this time, if there are reflection dots or the like, the light is scattered there and goes out from the surface of the light guide plate. The light guide plate reduces the area of the reflective dots in the vicinity of the light source, and increases the area of the reflective dots as the distance from the light source increases. Thereby, the light-guide plate can form uniform planar light.

However, in the surface light source device 200 using the reflector 8 and the light guide rod 10 described in the first embodiment, the laser light 51 and the LED light 41 are mixed inside the box shape of the reflector 8. Thus, planar light with high uniformity can be generated with a simple configuration.

FIG. 6 is a configuration diagram of the liquid crystal display device 100 as viewed from the −X axis direction as in FIG. In FIG. 6, the liquid crystal display element 13, the optical sheet 12, and the diffusion plate 11 are removed. That is, FIG. 6 shows a portion of the surface light source device 200 of the liquid crystal display device 100. FIG. 6 is a configuration diagram in which the liquid crystal display device is cut along the YZ plane at the position of 100 laser light sources 5.

FIG. 6 is a diagram for explaining the flow of heat emitted from the LED light source 4 and the flow of heat emitted from the laser light source 5. The liquid crystal display element 13 is mainly composed of glass. Further, 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 reflective part 8 with low thermal conductivity is arranged in the + Z-axis direction of the LED light source 4. For this reason, the heat emitted from the LED light source 4 is hardly transmitted in the + Z-axis direction. On the other hand, a back surface portion 1 having a high thermal conductivity is disposed in the −Z-axis direction of the LED light source 4. For this reason, the heat emitted from the LED light source 4 is easily transmitted in the −Z-axis direction. From the above, it is considered that the heat emitted from the LED light source 4 is less likely to flow to the + Z axis direction side than the reflecting portion 8. This is the reason why the liquid crystal display element 13, the optical sheet 12, the diffusion plate 11, and the reflection portion 8 are excluded from FIG. 6.

In the liquid crystal display device 100 using two types of light sources, the point at which the light turns white is determined by optimizing the output ratio of the

lights

41 and 51 of the

respective light sources

4 and 5. For example, when the total radiant flux of the laser light 51 emitted from the laser light source 5 is 1 W, the total radiant flux of the LED light 41 emitted from the LED light source 4 needs to be about 3 W. Thereby, the light in which the laser light 51 and the LED light 41 are mixed becomes white. At this time, if the temperature of each of the

light sources

4 and 5 is about room temperature (about 30 degrees) from the respective electro-optical conversion efficiencies of the laser light source 5 and the LED light source 4, the calorific value is about 3 W. . If the radiant flux emitted from the

light sources

4 and 5 is increased in order to increase the luminance of the display screen, the amount of heat generated by the

light sources

4 and 5 increases accordingly. However, even if the heat generation amount of the

light sources

4 and 5 increases, if the

heat sources

4 and 5 are sufficiently radiated, the temperature of the elements of the

light sources

4 and 5 is small and the heat generation amount does not change greatly. That is, the heat generation amount of the laser light source 5 and the heat generation amount of the LED light source 4 are approximately the same 3W. On the other hand, when the heat radiation of the

light sources

4 and 5 is insufficient, the temperature of the elements of the

light sources

4 and 5 increases, and the electro-optical conversion efficiency decreases. As a result, the calorific value of each

light source

4, 5 increases, and the temperature of each

light source

4, 5 rises further. In other words, in order not to cause a thermal problem, it is necessary to correctly estimate the environmental temperature at which the apparatus is used and the amount of heat generated at the environmental temperature, and to provide an efficient heat dissipation function commensurate with it.

The heat 18 generated by the laser light source 5 is transmitted from the mounting portion 22 of the radiator 2 to the base plate portion 24 and then to the radiation fins 21 and is released to the surrounding air 16. The radiator 2 is disposed on the most bottom side (−Y axis direction) of the liquid crystal display device 100. The heat 18 released from the radiating fins 21 to the surrounding air 16 moves in the + Y axis direction. This is because the air 16 that has received the heat 18 from the radiation fins 21 rises because it is lighter than the surrounding air. For this reason, fresh air flows into the radiating fin 21 from the −Y axis direction or the −Z axis direction. “Fresh air” is air that has not received the heat 18 from the radiation fins 21 or the heat 17 from the back surface portion 1. The amount of heat transfer from the solid surface to the air increases as the difference between the temperature of the solid surface and the temperature of the air increases. That is, the cooler 2 can efficiently release the heat 18 as the temperature of the air flowing into the radiator 2 is lower. The heat 18 generated by the laser light source 5 can be efficiently released to the surrounding air 16.

On the other hand, each LED

light source array

3a, 3b, 3c, 3d, 3e, 3f is attached to the back surface portion 1. The heat 17 generated by the LED light source 4 is transmitted to the respective substrates of the LED

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 part 1 is about 2 mm. Since the cross-sectional area of the back surface portion 1 is small, the heat 17 transmitted to the back surface portion 1 is difficult to be transmitted in the direction on the XY plane.

The LED

light source arrays

3b, 3c, 3d, 3e, and 3f are arranged away from the radiator 2. For this reason, 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 on 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 close to the radiator 2 will be considered. The LED light source array 3a is arranged in the + Y-axis direction with respect to the radiator 2. For this reason, the heat 17 emitted from the LED light source array 3 a is difficult to be transmitted to the radiator 2. The first reason is that since the cross-sectional area of the back surface portion 1 is small, the heat 17 transmitted to the back surface portion 1 is difficult to be transmitted in the direction on the XY plane. The second reason is that the heat 17 released from the back surface portion 1 into the air rises as described above, and thus moves in the + Y-axis direction. The third reason is that the heat insulating portion 15 is interposed between the base plate portion 24 and the back surface portion 1 of the radiator 2.

Further, the radiator 2 is arranged on the lower side (−Y axis direction side) than the LED light source array 3a. That is, the back surface (the surface on the −Z-axis direction side) of the back surface portion 1 of the portion to which the LED light source array 3a is attached directly touches the air 16 that has risen by receiving the heat 18 from the radiator 2. For this reason, the heat 17 released into the air from the LED

light source arrays

3 a, 3 b, 3 c, 3 d, 3 e, 3 f is released from the back surface portion 1 into the air 16. Here, the air 16 is air that has risen by receiving heat 18 from the radiator 2.

The air 16 heated by receiving heat 18 from the radiation fins 21 of the radiator 2 rises. Further, the LED light source 4 is disposed above (+ Y axis direction) the radiator 2. For this reason, the heat 17 emitted from the LED light source 4 is emitted from the back surface 1 to the air 16 warmed by the radiation fins 21. That is, the cooling performance of the LED light source 4 decreases as it goes upward (in the + Y-axis direction).

However, the LED light source 4 is superior to the laser light source 5 in heat characteristics (thermal characteristics). For this reason, the tolerance with respect to the temperature of LED light source 4 is large, and it is possible to design in the range which does not become a problem in quality.

On the other hand, the laser light source 5 has inferior thermal characteristics as compared with the LED light source 4. “Inferior thermal properties” means that the tolerance to temperature is small. The radiator 2 is disposed on the most bottom side (−Y axis direction side) of the liquid crystal display device 100. For this reason, fresh air flows into the radiation fins 21. “Fresh air” is air that has not received the heat 18 from the heat radiating fins 21 or the heat 17 from the back surface portion 1. The amount of heat transfer from the solid surface to the air increases as the difference between the temperature of the solid surface and the temperature of the air increases. That is, the cooler 2 can release heat more efficiently as the temperature of the air flowing into the radiator 2 is lower. That is, the heat 18 generated by the laser light source 5 can be efficiently released to the air 16.

The liquid crystal display device 100 includes a laser light source 5, an LED light source 4, and a radiator 2. The laser light source 5 emits laser light 51. The LED light source 4 emits LED light 41. The radiator 2 holds the laser light source 5 and transmits heat generated by the laser light source 5 to be released into 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 receives the laser beam 51 from the incident end, converts it into planar light, and emits it. Laser light 51 and LED light 41 emitted from the light guide 30 are emitted from the opening 83. A plurality of LED light sources 4 are provided and are arranged two-dimensionally facing the opening 83. The opening 83 has a function as a light emitting surface. That is, the light emission surface is a virtual surface provided in the opening 30f. The incident end is the incident surface 101 in the first embodiment. In addition, when an edge light type light guide plate is employed as described above, it is a side surface on which light is incident.

The light guide unit 30 includes a light guide rod 10 and a reflection unit 8. The light guide rod 10 has an incident surface 101 and converts the laser light 51 into linear light and emits it. The reflection unit 8 converts the laser beam 51 emitted from the light guide rod 10 into light in a planar shape. The LED light source 4 is disposed on a surface facing the opening 83 of the reflection unit 8. The light guide unit 30 mixes and emits the laser light 51 and the LED light 41 converted into planar light. The incident surface 101 is an incident end. The opening 83 has a function as a light emitting 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. Further, the invention described in Embodiment 1 can provide a backlight device having a configuration in which the heat of the LED light source that is not easily affected by heat is not easily transmitted to the laser light source that is easily affected by heat.

Embodiment 2. FIG.
FIG. 7 is a rear perspective view of the liquid crystal display device 101 according to the second embodiment of the present invention. The difference from the liquid crystal display device 100 according to the first embodiment shown in FIG. 1 is that, among the

radiators

2a, 2b, 2c, 2d, and 2e, the radiator 2b disposed inside the horizontal direction (X-axis direction), The heat dissipation area of 2c, 2d is larger than the heat dissipation area of the

radiators

2a, 2e arranged outside in the horizontal direction.

Other than the above points, the second embodiment is the same as the first embodiment. That is, the back surface portion 1, the heat insulating portion 15, the LED light source array 3, the LED light source 4, the laser light source 5, the reflecting portion 8, the reflecting sheet 9, the light guide rod 10, the diffusion plate 11, the optical sheet 12, the liquid crystal display element 13, and the heat dissipation. The configuration other than the heat radiation area of the vessel 2 is the same as that of the first embodiment.

For example, in the example of FIG. 7, the

radiators

2 a and 2 e on the outer side in the horizontal direction have 14 radiation fins 21. On the other hand, the radiation fins 21 of the

radiators

2b and 2d disposed inside the

radiators

2a and 2e are fifteen. The innermost radiator 2c has 18 radiation fins 21. Thus, the number of the radiation fins 21 increases as the radiator 2 disposed inside increases the radiation area.

In the liquid crystal display device 101, peripheral devices such as a timing controller circuit board for driving liquid crystal, a driving power supply board, and a video signal processing circuit board are arranged at the arrangement position 19 of the peripheral parts on the back surface portion 1. 7 and 8, the peripheral device arrangement position 19 is indicated by a broken line.

The arrangement positions 19 of these peripheral components are determined by the wiring length of the signal lines, the design of the liquid crystal display device 101, the position of the center of gravity of each component, and the like. However, normally, the peripheral parts are collected at the center of the back part 1. Many of the peripheral parts generate heat. In addition, peripheral components are mounted with relatively tall components such as electrolytic capacitors, LSIs that generate a large amount of heat, and radiators for switching elements. That is, heat is generated on the arrangement position 19 of the peripheral parts, and a relatively high part is mounted.

FIG. 8 is a configuration diagram of the liquid crystal display device 101 viewed from the −X axis direction. FIG. 8 is a configuration diagram in which the liquid crystal display device 101 is cut along the YZ plane at the position of the laser light source 5 including the arrangement position 19 of the peripheral parts. The difference from the configuration of the liquid crystal display device 100 shown in FIG. 6 is that an arrangement position 19 of peripheral parts is added. Further, the difference from the configuration of the liquid crystal display device 100 shown in FIG. 6 is that a turbulence 20 of the airflow is generated in the lower part of the peripheral component arrangement position 19 (in the −Y axis direction).

Heat 18 is received from the radiation fins 21 of the radiator 2, and the warmed outside air 16 rises in the + Y-axis direction. However, when peripheral parts are arranged in the upper part of the radiator 2 (in the + Y-axis direction) so as to obstruct the flow path, the upward airflow is obstructed, and the turbulence of the airflow 20 such as a vortex is generated.

When the air flow turbulence 20 occurs, the pressure loss of the flow path increases, and the flow velocity of the air 16 flowing through the radiator 2 decreases. As a result, the amount of heat radiation from the radiation fins 21 to the air 16 is reduced. That is, when peripheral parts are arranged in the upper part (+ Y axis direction) of the radiator 2 so as to block the flow path, the

radiators

2b, 2c, 2d arranged at the lower part (−Y axis direction) of the peripheral parts. The heat dissipating capacity per unit heat dissipating area is lower than the heat dissipating capacity of the

heat dissipators

2a and 2e in which no peripheral parts are arranged in the upper part (+ Y-axis direction).

Further, many of the peripheral components arranged at the peripheral component arrangement position 19 have many components that generate heat. The liquid crystal display device 101 is usually housed in a resinous housing or the like when used as a product. For this reason, the temperature of the air 16 in the horizontal center where the heat sources are concentrated and the heat flux density is increased, and the back surface 1 in the center in the horizontal direction are higher than those in the peripheral part. “Heat flux density” is simply the amount of heat flux per volume.

A heat insulating part 15 is interposed between the heat radiator 2 and the back surface part 1. The heat insulating portion 15 can prevent heat conduction from the back surface portion 1 to the radiator 2. However, heat radiation from the back portion 1 cannot be avoided. The

radiators

2b, 2c, and 2d receive radiant heat from the peripheral components and the temperature rises. For this reason, the temperature of the radiation fins 21 of the

radiators

2b, 2c, and 2d arranged in the center portion in the horizontal direction is higher than the temperature of the radiation fins 21 of the

radiators

2a and 2e arranged in the peripheral portion in the horizontal direction. Get higher. The amount of heat transfer from the solid surface to the air increases as the difference between the temperature of the solid surface and the temperature of the air increases. For this reason, even if the outside air 16 having the same temperature flows into the heat radiating fins 21 of the radiator 2, the heat radiating ability of the

radiators

2b, 2c, and 2d is arranged at the peripheral portion in the horizontal direction. It is inferior to the heat dissipation capability of the

radiators

2a and 2e.

Therefore, when the

radiators

2a, 2b, 2c, 2d, and 2e are arranged near the lower end in the Y-axis direction of the back surface portion 1, the radiators 2b that are arranged inside the horizontal direction (X-axis direction), The heat dissipating areas of 2c and 2d are made larger than the heat dissipating areas of the

radiators

2a and 2e arranged outside in the horizontal direction. This improves the heat dissipating ability of the

heat dissipators

2b, 2c, 2d arranged inside in the horizontal direction. That is, regardless of the position where the laser light source 5 is disposed, the radiator 2 can efficiently release the heat 18 generated by the laser light source 5 to the air 16.

Here, as an example of increasing the heat radiation area, an example in which the number of heat radiation fins 21 is increased is shown. However, the heat radiation area can be increased by increasing the size of the heat radiation fins 21. In addition, this time, among the

radiators

2b, 2c, and 2d arranged below the peripheral component arrangement position 19 (−Y-axis direction), the heat radiation area of the innermost radiator 2c is maximized. However, the size of the heat dissipation area of the

radiators

2b and 2d and the size of the heat dissipation area of the radiator 2c may be the same depending on the arrangement of peripheral components.

A plurality of laser light sources 5 are provided and arranged along the incident end. Of the arranged laser light sources 5, the heat radiation capability of the radiator 2 of the laser light source 5 located at both ends is smaller than the heat radiation capability of the radiator 2 of the laser light source 5 located between both ends. In the first embodiment, the incident end portions are the incident surfaces 101 of the light guide rods 10 arranged in the X-axis direction. A plurality of incident surfaces 101 are arranged in the X-axis direction, and the laser light source 5 is arranged to face the incident surface 101. In addition, when an edge light type light guide plate is employed as described above, it is a side surface on which light is incident.

In each of the above-described embodiments, there are cases where terms indicating the positional relationship of parts or the shape of the parts such as “center”, “horizontal”, or “vertical” are used. These include ranges that take into account manufacturing tolerances and assembly variations.

In addition, although embodiment of this invention was described as mentioned above, this invention is not limited to these embodiment.

DESCRIPTION OF SYMBOLS 1 Back part, 15 Thermal insulation part, 2 Radiator, 21 Radiation fin, 22 Mounting part, 23 Hole, 24 Base board part, 25 Lower end surface, 3 LED light source array, 4 LED light source, 5 Laser light source, 51 Laser light, 8 Reflector, 81a, 81b, 81c, 81d side plate, 82 bottom plate, 9 reflector sheet, 10 light guide rod, 101 entrance surface, 11 diffuser plate, 12 optical sheet, 13 liquid crystal display element, 15 heat insulation unit, 16 air, 17, 18 heat, 19 peripheral component placement position, 20 air turbulence, 30 light guide, 100 liquid crystal display, 200 surface light source device.

Claims

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 transmits heat emitted from the laser light source to be released into the air,
The laser light source is a liquid crystal display device disposed below the LED light source.
The laser light is incident from the incident end, further comprising a light guide unit that converts the light into a planar light and emits it,
The laser light and the LED light emitted from the light guide unit are emitted from a light emitting surface,
The liquid crystal display device according to claim 1, wherein a plurality of the LED light sources are provided and are two-dimensionally arranged to face the light emitting surface.
A plurality of the laser light sources are provided, arranged along the incident end,
The heat radiation capability of the radiator of the laser light source located at both ends of the arranged laser light sources is smaller than the heat radiation capability of the radiator of the laser light source located between the both ends. Item 3. A liquid crystal display device according to Item 2.
The light guide unit has the incident end, converts the laser light into linear light and emits the light, and a reflection that converts the laser light emitted from the light guide rod into light in a planar shape. Part
The LED light source is disposed on a surface facing the light emitting surface of the reflecting unit,
The liquid crystal display device according to claim 2, wherein the light guide unit mixes and emits the laser light and the LED light converted into planar light.
The liquid crystal display device according to any one of claims 1 to 4, further comprising a heat insulating portion provided between the radiator and the LED light source.
The liquid crystal display device according to claim 5, wherein the heat insulating portion is an air layer.
The liquid crystal display device according to claim 5, wherein the heat insulating portion is a resin material or a rubber material.