JP2005353507A - Backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device (light source) capable of generating light having high luminance and low unevenness of emission, and excellent in driving stability. <P>SOLUTION: A plurality of LED's are almost linearly arranged on a heat dissipating substrate. A reflector to collectively surround two or more LEDs continuously arranged is disposed on the substrate, and furthermore, a light guide plate is disposed on the reflector to form a backlight light source. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a backlight device used for liquid crystal panels such as a mobile phone, a portable information terminal, a car navigation system, a laptop (notebook) PC, and a liquid crystal television.

  Cold cathode tubes are generally used as light sources for backlights of liquid crystal panels, but many problems have been pointed out, such as cold cathode tubes, which consume a lot of power, generate a large amount of heat, and have low impact durability. Yes. On the other hand, LEDs are attracting attention as light sources that can improve or solve these problems associated with the use of cold-cathode tubes. For example, Japanese Unexamined Patent Application Publication No. 2000-275636 discloses a backlight unit using LEDs.

JP 2000-275636 A

When an LED is used as a light source of a liquid crystal panel, there is a problem that uneven light emission tends to occur. That is, the problem is how to convert the light of the LED, which is originally a point light source, into uniform planar light. In this regard, a light guide plate used to convert LED light into planar light is provided with a reflecting surface or a diffusing surface, or a light guide surface of the light guide plate is provided with a V-shaped groove to transmit light during introduction. Measures are taken to promote diffusion and mixing of light within the light guide plate by, for example, diffusing (see, for example, Patent Document 1). Incidentally, at present, there is a demand for providing a larger liquid crystal panel, but the problem of unevenness in light emission becomes more apparent as the liquid crystal panel becomes larger.
On the other hand, the LED has a feature that the amount of heat generated is small. However, if the amount of use of the LED increases with an increase in the size of the liquid crystal panel, the total amount of heat generated increases accordingly, resulting in a decrease in driving stability.
On the other hand, there has been a demand for higher brightness and higher color reproducibility of liquid crystal panels against the background of improving living standards and expanding the applications of liquid crystal panels.
In view of the above problems, an object of the present invention is to provide a backlight device capable of generating planar light with more uniform luminance. It is another object of the present invention to provide a backlight device having excellent driving stability. Furthermore, it aims at providing the backlight apparatus which can produce | generate the planar light of high brightness | luminance. In addition, another object is to provide a backlight device capable of forming a liquid crystal panel with high color reproducibility.

The present invention provides the following configuration in order to achieve at least one of the above objects. That is, the present invention
A heat dissipation substrate;
A plurality of LEDs arranged substantially linearly on the heat dissipating substrate;
A reflector that collectively surrounds two or more LEDs that are continuously arranged in the LED, a light introduction surface that introduces light of the LED, and a light emission surface that emits the introduction light. A light guide plate;
Is a backlight device.

In the present invention, by arranging the LEDs in a substantially linear shape, the lights of the LEDs overlap or interfere with each other to generate linear light. The light distribution of each LED is controlled by the reflector, but the distance between the LEDs is shortened by providing a reflector so as to collectively surround a group of LEDs instead of providing a reflector for each LED. be able to. That is, LEDs can be arranged with high density. As a result, not only high brightness can be achieved, but also light emission unevenness (luminance unevenness) can be reduced. On the other hand, by adopting a heat dissipation substrate, a good heat dissipation effect is obtained, and the heat dissipation is excellent. Therefore, even if the amount of heat generation increases as the LEDs are arranged at a high density, high driving stability can be maintained.
As described above, the backlight device of the present invention can generate light with high luminance and low light emission unevenness, and has excellent driving stability.

(substrate)
In the present invention, a heat dissipating substrate is employed as a substrate for mounting the LED. An LED is mounted on the substrate, and a reflector described later is disposed so as to surround the LED.
The material of the substrate is not particularly limited as long as high heat dissipation is obtained. For example, a substrate made of aluminum, an aluminum alloy, copper, or a copper alloy can be used. A ceramic substrate may also be used.
The size of the substrate is not particularly limited. By using a relatively large substrate, the heat dissipation is improved and the design and formation of the wiring pattern is facilitated (particularly, a sufficiently large electrode pad can be secured and the formation thereof is facilitated). In addition, it is possible to firmly connect the reflector described later, the heat sink described later, or both of them and the substrate with screws or the like by using an area other than the LED mounting area or the area necessary for forming the wiring pattern. Thus, the impact stability and the reliability are improved. Also, the connecting work is easy. Furthermore, a high heat dissipation effect can be obtained by forming a good contact state between the substrate and the heat sink.

Although an efficient heat dissipation action is achieved by employing a heat dissipation substrate, it is preferable to use a heat sink for the purpose of further improving heat dissipation. Specifically, for example, a heat sink that contacts the back surface of the substrate is used. Since a higher heat dissipation effect is obtained as the contact area between the substrate and the heat sink increases, it is preferable that substantially the entire back surface of the substrate is in contact with the heat sink. For example, if a concave portion or a groove (including a step) into which the substrate is inserted is provided in a part of the heat sink, a good contact state between the back surface of the substrate and the heat sink as described above can be created. In this case, since the substrate is embedded in the heat sink, the thickness can be reduced.
The heat sink is required to have a large heat capacity. For example, the material is copper or aluminum.
Note that a separate heat sink may not be provided if sufficient heat dissipation characteristics can be obtained by using a relatively large substrate. In this case, the substrate also has a heat sink function.

(LED)
The type of LED to be used is not particularly limited, but an LED of a type in which an LED chip is directly mounted on a substrate (chip on board (COB) type) is preferably used. This is because the light source unit can be configured compactly integrally with the substrate.
In the present invention, a plurality of LEDs are used, and they are arranged on the substrate in a substantially linear shape. By adopting such an arrangement mode, linear light can be generated, and the incidence efficiency is improved even for a thin light guide plate (matching with the light guide plate is facilitated). In addition, it is possible to suppress the occurrence of luminance unevenness in the light guide plate. Here, “substantially linear” in the present invention refers to a state in which LEDs are arranged in a line in one or a plurality of lines. In the present invention, typically, all LEDs are linearly arranged in a row. Usually, the LEDs are arranged in a straight line. However, for example, when the light emitting surface of the light guide plate to be used is a curved surface, the LEDs may be arranged in a curved shape in accordance with the shape of the light emitting surface.

  In one embodiment of the present invention, a plurality of blue light-emitting LEDs (hereinafter also referred to as “blue LEDs”) and a plurality of red light-emitting LEDs (hereinafter also referred to as “red LEDs”) are used in combination. Then, a phosphor that is excited by the light of the blue light emitting LED and emits yellow or yellow-green fluorescence (hereinafter also referred to as “yellow phosphor”) is used together. In such an embodiment, the white LED light is finally obtained by mixing (mixing) the blue LED light, the yellow to yellow-green light from the phosphor, and the red LED light. White light can be obtained only by a combination of a blue LED and a yellow phosphor, but the white light obtained in this way has a relatively small red wavelength component, for example, as a backlight of a liquid crystal panel. When used, red color is inferior. That is, color reproducibility is poor. On the other hand, if the red LED is further used in combination as described above, a red component is added, so that, for example, when used as a backlight of a liquid crystal panel, a bright red color can be developed (color). Display with excellent reproducibility is possible). In addition, as described later, it is possible to obtain white light by combining a red LED, a green LED, and a blue LED, but the light emission efficiency is better when the above configuration is adopted.

The yellow phosphor is provided at a position where the light of the blue LED is irradiated, but it is preferably disposed in the vicinity of the blue LED for efficient excitation and fluorescence action. For example, a resin containing a yellow phosphor is applied on a blue LED, or a cup-shaped space formed by a reflector described later is filled with a resin containing a yellow phosphor (that is, the yellow phosphor is The yellow phosphor can be disposed in the vicinity of the blue LED, for example, by sealing the LED with a resin that contains it).
Here, if the phosphor is also arranged in the vicinity of the red LED (for example, the red LED is also covered with the phosphor-containing resin), the phosphor functions as a diffusing agent. Therefore, red, blue, and yellow light Mix well.

The yellow phosphor for example, the general formula _{Y 3-x Gd x Al 5} -y Ga y O 12: Ce (0 ≦ x ≦ 3,0 ≦ y ≦ 5) yttrium-aluminum-garnet fluorescent represented by The body can be preferably used. Such a phosphor efficiently converts blue light into yellow or yellow-green light. In the above general formula, part or all of yttrium (Y) may be replaced with Lu or La, and part or all of aluminum (Al) may be replaced with In or Sc. You can also.
Further, as the yellow phosphor, ZnS: Cu, Au, Al, ZnS: Cu, Al, ZnS: Cu, ZnS: Mn, ZnS: Eu, YVO ₄ : Eu, YVO ₄ : Ce, Y ₂ O ₂ S: Eu And one or more phosphors selected from Y ₂ O ₂ S: Ce can be used. Here, ZnS: Cu, Au, Al is a ZnS-based photoluminescent phosphor activated with Cu, Au, and Al using ZnS as a base material. ZnS: Cu, Al, ZnS: Cu, ZnS: Mn and ZnS: Eu are photoluminescent phosphors activated by Cu, Al, Cu, Mn, and Eu, respectively, using ZnS as a base material. Similarly, YVO ₄ : Eu and YVO ₄ : Ce are phosphors activated with Eu and Ce, respectively, using YVO ₄ as a base, and Y ₂ O ₂ S: Eu and Y ₂ O ₂ S: Ce are Y ₂ O. ₂ is a phosphor activated with Eu and Ce, respectively. These phosphors have an absorption spectrum for blue light, and emit light having a wavelength longer than the excitation wavelength.
Each of the above phosphors has a unique emission color, and the emission color can be taken into consideration in the selection of the phosphor. That is, a phosphor having an appropriate fluorescent color can be selected so that a desired white color can be obtained by mixing the fluorescence emitted therefrom and the light of the blue LED and the red LED. From another viewpoint, white light having a different color can be obtained by changing the yellow phosphor used. Two or more different yellow phosphors may be used in combination.

The number of blue LEDs used and the number of red LEDs used are not limited, but it is preferable to relatively reduce the number of red LEDs used. This is because the light of the red LED is used for the purpose of compensating for the red component that is insufficient with only the blue LED and the yellow phosphor as described above.
In addition to the blue LED and the red LED, one type or a plurality of types of LEDs having different emission colors such as a green LED may be used.

In another embodiment of the present invention, a plurality of ultraviolet light emitting LEDs (hereinafter also referred to as “ultraviolet LEDs”) are used. A phosphor that emits red fluorescence when excited by ultraviolet light (hereinafter also referred to as “red phosphor”), a phosphor that similarly emits green fluorescence (hereinafter also referred to as “green phosphor”), Similarly, a phosphor that emits blue fluorescence (hereinafter also referred to as “blue phosphor”) is also used. In such an embodiment, the white light is finally obtained by mixing (mixing) the fluorescence from each phosphor, that is, the red, green, and blue fluorescence. When an ultraviolet LED is used, there is an advantage that the color change can be reduced. That is, in this case, the color balance is less likely to change over time, and the color balance is excellent in terms of current dependency.
In addition to the above phosphors, a phosphor that emits yellow or yellow-green fluorescence when excited by light of ultraviolet light or blue phosphor (hereinafter also referred to as “yellow phosphor”) may be used. In this case, red light, green light, blue light, and yellow light are generated, and by mixing (mixing) the light, white light that is more excellent in color reproducibility can be obtained. Note that a red phosphor, a blue phosphor, and a yellow phosphor may be used in combination without using the green phosphor. This is because the fluorescence of the yellow phosphor generally has a broad wavelength, so that the yellow to green color can be covered by the fluorescence.
In addition to the ultraviolet LED, one type or a plurality of types of LEDs having different emission colors such as a red LED, a green LED, or a blue LED may be used.

Here, as the red phosphor, for example, 6MgO · As ₂ O ₅ : Mn ⁴⁺ , Y (PV) O ₄ : Eu, CaLa _0.1 Eu _0.9 Ga ₃ O ₇ , BaY _0.9 Sm _{0.1 Ga 3 O 7, Ca (Y} 0.5 Eu 0.5) (Ga 0.5 In 0.5) 3 O 7, Y 3 O 3: Eu, YVO 4: Eu, Y 2 O 2: Eu, 3 .5MgO.0.5MgF ₂ GeO ₂ : Mn ⁴⁺ , (Y · Cd) BO ₂ : Eu, and the like can be used. On the other hand, examples of green phosphors include Y ₂ SiO ₅ : Ce ³⁺ , Tb ³⁺ , Sr ₂ Si ₃ O ₈ .2SrCl ₂ : Eu, BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Mn ²⁺ , ZnSiO ₄ : Mn. _{, Zn 2 SiO 4: Mn,} LaPO 4: Tb, SrAl 2 O 4: Eu, SrLa 0.2 Tb 0.8 Ga 3 O 7, CaY 0.9 Pr 0.1 Ga 3 O 7, ZnGd 0.8 Ho _0.2 Ga ₃ O ₇ , SrLa _0.6 Tb _0.4 Al ₃ O ₇ , ZnS: Cu, Al, (Zn, Cd) S: Cu, Al, ZnS: Cu, Au, Al, Zn ₂ SiO _{4: Mn, ZnSiO 4: Mn} , ZnS: Ag, Cu, (Zn · Cd) S: Cu, ZnS: Cu, GdOS: Tb, LaOS: Tb, YSiO 4: Ce · Tb, ZnGe ^{_{4: Mn, GeMgAlO: Tb,}} SrGaS: Eu 2+, ZnS: Cu · Co, MgO · nB 2 O 3: Ge, Tb, LaOBr: Tb, Tm, and _La 2 _O 2 S: be employed Tb, etc. it can. Similarly, as the blue phosphor, for example, (Ba, Ca, Mg) ₅ (PO ₄ ) ₃ Cl: Eu ²⁺ , (Ba, Mg) ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Ba ₃ MgSi ₂ O ₈ : Eu ²⁺ , BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , (Sr, Ca) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , (Sr, Ca) ₁₀ (PO ₄ ) ₆ Cl ₂ .nB ₂ O ₃ : Eu ²⁺ Sr ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , (Sr, Ba, Ca) ₅ (PO ₄ ) ₃ Cl: Eu ²⁺ , Sr ₂ P ₂ O ₇ : Eu, Sr ₅ (PO ₄ ) ₃ Cl: _{Eu, (Sr, Ca, Ba} ) 3 (PO 4) 6 Cl: Eu, SrO · P 2 O 5 · B 2 O 5: Eu, (BaCa) 5 (PO 4) 3 Cl: Eu, SrLa 0.95 Tm _0.05 Ga _{3 7, ZnS: Ag, GaWO 4} , Y 2 SiO 6: Ce, ZnS: Ag, Ga, Cl, Ca 2 B 4 OCl: Eu 2+, BaMgAl 4 O 3: Eu 2+, and the general formula (M1, _{Eu) 10} 1 known as a phosphor represented by (PO ₄ ) ₆ Cl ₂ (M1 is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba), or an organic phosphor, , 4-bis (2-methylstyryl) benzene (Bis-MSB), stilbene dyes such as trans-4,4′-diphenylstilbene (DPS), and 7-hydroxy-4-methylcoumarin (coumarin 4). A coumarin-type pigment | dye etc. can be employ | adopted.

(Reflector)
In the present invention, a reflector that collectively encloses a group (two or more) of LEDs arranged in succession is used. That is, a reflector is not prepared for each LED, but one reflector is used for a plurality of LEDs. Specifically, for example, when eight LEDs are arranged in a line, one reflector can be used so as to surround all the LEDs together. Alternatively, a plurality of reflectors may be used, such as dividing the LEDs into left and right four parts and using one reflector for each LED group.
The material of the reflector is not particularly limited. For example, white resin, aluminum, or the like can be used as a reflector forming material. The reflector may have a surface (light receiving surface) facing the LED that is light reflective. Therefore, for example, a reflector that is provided with light reflectivity by forming a suitable material and then applying a white paint or plating to the region to be the light receiving surface may be used as the reflector.

(Light guide plate)
The light guide plate includes at least a light introducing surface and a light emitting surface. In principle, the light introduction surface is a surface facing the light emission side of the LED, and light is introduced into the light guide through the light introduction surface. The light introduction surface is formed on a part or the whole of the end surface or the back surface of the light guide plate (the surface located on the opposite side of the light emitting surface). Specifically, for example, one end surface of the light guide is used as a light introduction surface. Alternatively, the back surface of one end portion of the light guide plate is a light introduction surface. In this case, it is preferable that the end surface of the light guide plate at the end position is a surface having an inclination that reflects the introduced light in the direction of the opposite end surface. This is because the introduced light is favorably guided by the reflection action by the end face of the light guide plate. The end face of the light guide plate may be a flat surface or a curved surface (including a case where a part is a curved surface).

  A surface that tapers toward the light emitting surface as the distance from the region where the light introduction surface is formed can be formed on the back surface of the light guide plate. As such a configuration, for example, if LED light is incident so that its optical axis is parallel to the light emitting surface of the light guide plate, the light that reaches the back surface of the light guide plate is inherently less as it gets farther from the light introduction surface. The tapered surface portion can receive light that is closer to the optical axis, that is, light with high luminance, by being inclined in the optical axis direction as the distance from the light introduction surface increases. As a result, the amount (light intensity) of light received at the tapered surface portion is made uniform throughout. As a result, light emission unevenness on the light emitting surface of the light guide plate where the light reflected by the tapered surface portion radiates is reduced. Preferably, substantially the entire back surface of the light guide plate is formed with such a tapered surface. This is because light emission unevenness is reduced over the entire light emitting surface of the light guide plate, and the light emission luminance is made uniform.

The material of the light guide plate is not particularly limited as long as it is light transmissive. The light guide plate is preferably made of a transparent material (including colorless and transparent, and colored and transparent). Moreover, it is preferable to comprise a light-guide plate with the material which is easy to process and was excellent in durability. As a material of the light guide plate, for example, acrylic resin, polyethylene terephthalate (PET), polycarbonate resin, epoxy resin, glass, or the like can be used.
Hereinafter, the present invention will be described in more detail with reference to examples.

FIG. 1 is an exploded perspective view of a liquid crystal display device 1 according to an embodiment of the present invention. FIG. 2 is a plan view of the light source unit 15 constituting the light source unit 10 (backlight light source) of the liquid crystal display device 1. FIG. 3 is a cross-sectional view of the light source unit 10.
The liquid crystal display device 1 is roughly divided into a light source unit 10 (backlight light source), a liquid crystal panel 20, and a design cover 30. The light source unit 10 includes a light guide plate 11, a light source unit 15, and a heat sink 18. The light guide plate 11 is made of acrylic resin and has a substantially flat plate shape. The upper surface of the light guide plate 11 becomes the light emitting surface 12, and the liquid crystal panel 20 is placed thereon. On the other hand, the one end surface 13 of the light guide plate 11 has a predetermined inclination. In this example, the angle formed by the end surface 13 and the light emitting surface 12 is about 135 °. Note that the inclination angle of the end face 13 can be designed so that the end face 13 can reflect light from a light source unit 15 described later with efficient and good light distribution characteristics. In the present embodiment, the end surface 13 is planar, but it may be a curved surface curved with a predetermined curvature (the curvature may not be constant over the entire surface). Or it is good also as a shape which combined the plane and the curved surface.

The back surface 14 of the light guide plate 11 is a tapered surface that gradually approaches the upper surface (light emitting surface 12) from the end surface 13 side toward the opposite end surface (see FIGS. 1 and 3).
A light source unit 15 is disposed below the light guide plate on the side where the end face 13 is formed. In the present embodiment, a total of three light source units 15 are arranged in a line. Each light source unit 15 includes a substrate 21, a plurality of LEDs mounted thereon, and a reflector 24. Eight blue LEDs 16 and three red LEDs 17 are used for one light source unit 15. The plurality of LEDs are arranged linearly on the substrate 21 so that every second LED is a red LED 17.

  The substrate 21 has a copper surface nickel-plated and has high thermal conductivity. Further, as shown in FIG. 1, the surface area of the substrate 21 is significantly larger than that of the LED mount region 22. Employing the substrate 21 having such a configuration is advantageous in terms of forming a wiring pattern (for example, a large electrode pad can be formed and electrical connection is facilitated). Further, the contact area between the substrate 21 and the heat sink 18 is increased, and the heat conduction efficiency from the substrate 21 to the heat sink 18 is increased. As a result, the light source unit 10 (backlight light source) having a further excellent heat dissipation effect can be obtained, and high driving stability and long life can be achieved over a long period of time. In this embodiment, both the blue LED 16 and the red LED 17 are COB type (chip on board type).

As shown in FIGS. 2 and 3, the reflector 24 is arranged so as to collectively surround the blue LEDs 16 and the red LEDs 17 arranged on a straight line. The reflector 24 is made of white resin and has a trapezoidal cross section and a horizontally long opening 25. The reflector 24 is placed on the substrate 21 so that the blue LED 16 and the red LED 17 are accommodated in the opening 25. Thereafter, the opening 25 of the reflector 24 is filled with an epoxy resin 27 in which a yellow phosphor is dispersed. On the other hand, the space between the reflector 24 and the light guide plate 11 is filled with a transparent optical gel whose refractive index is equal to or similar to that of the light guide plate (not shown).
On the other hand, the reflector 24 includes a mounting portion 26 that extends to the side opposite to the side where the opening 25 is formed. The reflector 24 is screwed to the substrate 21 using the mounting portion 26. In the present embodiment, the reflector 24, the substrate 21, and the heat sink 18 described later are connected by the screwing. According to such a configuration, these members can be firmly integrated by a simple method. Therefore, it is possible to expect an improvement in quality such that the assembling work becomes easy and the strength against external impact is increased.
The heat sink 18 is provided with a step 19 so that the substrate 21 and the reflector 24 can be accommodated. In this embodiment, the heat sink 18 is made of aluminum copper, but is not limited to this.

In the light source unit 10 (backlight light source) configured by the light guide plate 11, the light source unit 15, and the heat sink 18, the following light emission modes are obtained (see FIG. 3). The liquid crystal panel 20 is placed on the light emitting surface 12 of the light guide plate 11 and then the design cover 30 is put on.
First, when each LED is turned on, blue light from the blue LED 16 and red light from the red LED 17 are emitted. A part of the blue light is used to excite the yellow phosphor in the resin 27 that covers each LED. This produces yellow light. Here, linear light is emitted from each light source unit 15 by arranging the blue LED 16 and the red LED 17 in a straight line as described above. Accordingly, it is possible to allow light to be incident on the thin light guide plate with high incidence efficiency. In addition, it is possible to suppress the occurrence of luminance unevenness in the light guide plate.

By the way, each light (blue light, red light, and yellow light) described above is directly or after being reflected by the reflector 24, and then introduced into the light guide plate 11 through the light guide plate back surface 14. In this process or in the process of proceeding through the light guide plate 11, the lights are mixed and finally white light is emitted from the light emitting surface 12 of the light guide plate 11. Here, the gap between the reflector 24 and the light guide plate 11 is filled with a transparent optical gel whose refractive index is equal to or similar to that of the light guide plate, so that the light loss can be minimized. Efficient light is introduced into the interior. On the other hand, since the end face 13 of the light guide plate 11 positioned above each LED has a predetermined inclination as described above, the introduced light is efficiently reflected there and converted to light in the opposite end face direction. Can do. As a result, a good light guiding effect is obtained, and the luminance of light emitted from the light emitting surface 12 is made uniform. That is, light emission unevenness is reduced. On the other hand, when the light guide plate back surface 14 is tapered as described above, positive light reflection to the light emitting surface 12 side occurs on the light guide plate back surface 14 and high light emission efficiency is obtained. Further, the distance between the light guide plate back surface 14 and the light emitting surface 12 becomes closer to the region farther from the light incident region, and the light extraction efficiency is improved accordingly. As a result, the shortage of the light amount due to the distance from the light incident area is resolved, thereby reducing the light emission unevenness.
On the other hand, the red wavelength component is compensated by using the red LED 17 in addition to the blue LED 16. Thereby, the light emitted from the light source unit 10 includes the wavelength components corresponding to the three primary colors of light in a well-balanced manner. As a result, it is possible to develop a bright red color that cannot be realized only by the combination of the blue LED and the yellow phosphor, and a liquid crystal display device having excellent color reproducibility is configured.

In the above configuration, the surface of the end face 13 can be subjected to a light reflection process to enhance the reflection action by the end face 13.
In this embodiment, eleven LEDs are used for each light source unit 15, but the number of LEDs used is not limited to this. For example, a larger number or a smaller number of LEDs may be used in consideration of the size of the light source unit 15 or the light guide plate 11, the required luminance, and the like. Moreover, the usage ratio of the blue LED 16 and the red LED 17 is not particularly limited. By changing the usage ratio of these LEDs, the hue of white light finally obtained can be adjusted. It is also possible to perform the same adjustment by using other light emitting color LEDs (for example, a green LED and a blue-green LED) together.
On the other hand, in addition to the yellow phosphor, a phosphor emitting fluorescence of other colors may be used in combination. Moreover, the arrangement | positioning aspect thru | or inclusion aspect of fluorescent substance are not specifically limited, For example, the above fluorescence effects can also be acquired by apply | coating resin containing fluorescent substance only on blue LED16.

In this embodiment, an ultraviolet light emitting LED is used as a light source. On the other hand, a red phosphor, a green phosphor, and a blue phosphor are used as the phosphor. Other configurations are the same as those of the above-described embodiment (that is, the same as the configuration shown in FIGS. 1 to 3).
In the above configuration, the light from the LED is used to excite three types of phosphors. That is, light in the ultraviolet region emitted from the LED is irradiated onto the red phosphor, the green phosphor, and the blue phosphor to generate red light, green light, and blue light. The light of the three primary colors thus obtained enters the light guide plate while being mixed (color mixing). As a result, white light obtained by mixing (mixing) these lights is emitted from the light emitting surface of the light guide plate.
Also in this embodiment, the light guide plate back surface 14 has a tapered surface, the light emission efficiency is improved and the light emission unevenness is reduced, and the use of a heat dissipation substrate and a heat sink increases the driving stability and the life span. The same effect is produced.

4 and 5 show a liquid crystal display device 2 which is another embodiment. 4 is an exploded perspective view of the liquid crystal display device 2, and FIG. 5 is an enlarged perspective view of the light source unit 40 used in the liquid crystal display device 2. In addition, the same code | symbol is attached | subjected to the member same as a prior Example, and the description is abbreviate | omitted.
As will be described below, the liquid crystal display device 2 uses a substrate 41 having a reflector function. The substrate 41 has a substantially rectangular parallelepiped shape, and a groove 42 having a U-shaped cross section is formed along the longitudinal axis of the substrate 41 on one surface side. On the other hand, the surface of the substrate 41 is plated with nickel (Ni) and has high reflectivity. Accordingly, the substrate 41 has a function as a reflector that reflects (and distributes) light on the wall surface of the groove 42 in addition to the original function or role (LED mounting, wiring, etc.). In addition, the substrate 41 of this embodiment is made of copper, has a high thermal conductivity, and also has a function as a heat sink.
An LED is mounted in the groove 42 of the substrate 41. In this embodiment, twelve blue LEDs 16 and three red LEDs 17 are used. As shown in FIG. 5, the plurality of LEDs are linearly arranged in the groove 42 of the substrate 41 so that every fourth LED becomes the red LED 17. The groove 42 is filled with an epoxy resin in which a yellow phosphor is dispersed. The electrodes of each LED are connected to the wiring pattern 44 by lead wires 43.

  In the light guide plate 50 used in this embodiment, the end surface 13 (light incident surface) is perpendicular to the light emitting surface 12. And the board | substrate 41 and the light-guide plate 50 are connected so that the mount surface side of LED may oppose the end surface 13 of the light-guide plate 50. FIG. The back surface 14 of the light guide plate is a tapered surface as in the case of the above embodiment. An optical gel layer is formed between the substrate 41 and the light guide plate end face 13.

According to the above configuration, after the blue light and red light caused by each LED and the yellow light caused by the phosphor are reflected directly or by the wall surface of the groove 42 of the substrate 41, the light guide plate end face 13 (light introducing face) ) Through the light guide plate 50. In this process or in the process of proceeding through the light guide plate 50, each light is mixed (mixed color), and finally, white light is emitted from the light emitting surface 12 of the light guide plate 50.
In this embodiment, the light source unit 40 has a good light distribution characteristic and is excellent in heat dissipation by using the substrate 41 serving as both a reflector and a heat sink. Further, the number of parts as a whole is reduced, and effects such as improvement in assembly workability and reduction in manufacturing cost are exhibited.
In the present embodiment as well, the light emitting plate back surface 14 has a tapered surface to improve the light emission efficiency and light emission unevenness, and to improve the color reproducibility by using the red LED 17 in addition to the blue LED 16. The same effect as the example is produced.

  The backlight device of the present invention transmits information such as a liquid crystal panel such as a mobile phone, a car navigation system, a laptop (notebook) PC, and a liquid crystal television, an instruction board and an advertisement (board) used outdoors or indoors. It can be used as a light source used for a medium.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

FIG. 1 is an exploded perspective view of a liquid crystal display device 1 according to an embodiment of the present invention. FIG. 2 is a plan view of the light source unit 15 constituting the light source unit 10 (backlight light source) of the liquid crystal display device 1. FIG. 3 is a cross-sectional view of the light source unit 10 of the liquid crystal display device 1. FIG. 4 is an exploded perspective view of a liquid crystal display device 2 according to another embodiment. FIG. 5 is an enlarged perspective view of the light source unit 40 used in the liquid crystal display device 2.

Explanation of symbols

1, 2 Liquid crystal display device 10 Light source section (backlight light source)
11 50 Light guide plate 12 Light guide plate light emitting surface 13 Light guide plate end surface (reflective surface)
14 Back surface of light guide plate 15 40 Light source unit 16 Blue LED
17 Red LED
18 heat sink 20 liquid crystal panel 21 41 substrate 24 reflector 30 design cover

Claims (4)

A heat dissipation substrate;
A plurality of LEDs arranged substantially linearly on the heat dissipating substrate;
A reflector that collectively surrounds two or more LEDs that are continuously arranged in the LED, a light introduction surface that introduces light of the LED, and a light emission surface that emits the introduction light. A light guide plate;
A backlight device comprising: The plurality of LEDs includes a plurality of blue light emitting LEDs and a plurality of red light emitting LEDs,
The backlight device according to claim 1, further comprising a yellow or yellow-green phosphor at a position irradiated with light of the blue light emitting LED. The plurality of LEDs include a plurality of ultraviolet light emitting LEDs,
The backlight device according to claim 1, further comprising a red phosphor, a green phosphor, and a blue phosphor at a position irradiated with light from the ultraviolet light emitting LED. The light introduction surface is formed on the back surface of at least one end of the light guide plate;
The end face of the light guide plate at the end position has a slope that reflects the introduced light toward the opposite end face.
The backlight apparatus in any one of Claims 1-3.

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