JP4844246B2 - Light emitting device and liquid crystal display backlight device - Google Patents

Description

  The present invention relates to a light emitting device used as an illumination light source from the back surface of a liquid crystal display device or a push button including a numeric keypad of a mobile phone, and a backlight device for liquid crystal display using the same.

For example, in a liquid crystal display device, a backlight device having a configuration in which light from a light source is incident on a light guide plate and light is uniformly guided from the light guide plate to the liquid crystal display panel is used. As a light source used in such a backlight device, for example, there is a light emitting device in which silicone is filled in an interface of a light introducing portion of a light guide plate so that an air layer is not formed in the interface (see, for example, Patent Document 1) ). With this configuration, the light-emitting device and the light introducing portion of the light guide plate are closely adhered by silicone, so that light from the light-emitting device can be efficiently introduced into the light guide plate with less reflection at the interface.
JP 2003-234008 A ([0010] to [0013], [0019], FIGS. 1 and 2)

  However, according to the conventional light emitting device, since the mortar-shaped reflector of the package protrudes from the mounting surface of the light emitting element, the light emission angle by the light emitting element is limited, and the light distribution range is narrowed. For this reason, in a backlight device or the like, when trying to reduce the number of light emitting elements used by widening the interval between the light emitting devices, a portion where the luminance decreases between the light emitting devices is generated, and the light emitting device in which luminance unevenness occurs There is a problem of becoming.

  Accordingly, an object of the present invention is to provide a light emitting device and a liquid crystal display backlight device in which the light distribution of the light emitting elements is widened so that luminance unevenness does not occur even when the number of light emitting elements used is reduced. It is in.

To achieve the above object, the present invention provides a plurality of light emitting devices arranged in an array, and a light guide plate that emits light introduced from the plurality of light emitting devices through a light introduction end surface to the back surface of the liquid crystal display panel; And the plurality of light emitting devices are connected to the first and second leads, the mount having an element mounting portion that exposes the first and second leads on the element mounting surface and protrudes from the flat surface. A light emitting element mounted on the element mounting surface of the element mounting portion, and the mount includes a plate-shaped first substrate, and the element mounting portion. And the second substrate stacked on the first substrate, wherein the light guide plate has a recess for positioning the element mounting portion of the mount on the light introduction end surface, Each light emitting device is connected between each light emitting device. To provide a liquid crystal display backlight apparatus characterized by not having a light shield for shielding light.

  According to such a configuration, in the plurality of light emitting devices provided on the light introduction end surface of the light guide plate, the light emitting element is mounted on the element mounting surface of the element mounting portion. Since there is no light shield and the light distribution range of each light emitting element is widened, luminance unevenness does not occur between the light emitting devices.

  According to the light-emitting device of the present invention, the light distribution of the light-emitting elements is widened, and even when used as a backlight light source, unevenness in luminance can be prevented. In addition, according to the backlight device of the present invention, it is configured by using the light emitting device equipped with the light emitting element in which no light shield exists in the light emitting direction, so that luminance unevenness does not occur between the light emitting devices. be able to.

[First Embodiment]
(Configuration of light emitting device)
FIG. 1 shows a light emitting device according to a first embodiment of the present invention. The light emitting device 1 is configured by mounting a light emitting element 18 on a mount 100. The mount 100 is configured by laminating a plate-like first substrate 14 and a second substrate 16.

  The first substrate 14 includes a ceramic insulating layer 10, conductive patterns 11A and 11B provided on the upper surface of the ceramic insulating layer 10 by screen printing or the like, and via holes having one ends connected to the conductive patterns 11A and 11B. 12A, 12B, and first and second electrodes 13A, 13B provided on the lower surface of the ceramic insulating layer 10 with the other ends connected to the via holes 12A, 12B. The via holes 12A and 12B are formed by metallizing the inner surfaces of the insulating holes.

  The second substrate 16 protrudes so as to be connected to the ceramic insulating layer 20 having a columnar protruding portion (which is an element mounting portion, but hereinafter referred to as a protruding portion) 16a in the center and the conductor patterns 11A and 11B. First and second via holes 15A and 15B as first and second leads provided in the portion 16a are provided. Here, the upper surface of the second substrate 16 other than the projecting portion 16a serves as a reference surface 16b for mounting on the light guide, and the upper surface of the projecting portion 16a serves as an element mounting surface 16c on which the light emitting element 18 is mounted.

  The light-emitting element 18 is a flip-chip type, and has a structure in which, for example, an n-type layer, a layer including a light-emitting layer, and a p-type layer are sequentially grown on a sapphire substrate by MOCVD (metal organic chemical vapor deposition). For example, a blue light emitting diode (blue LED) made of a GaN-based compound semiconductor that emits blue light having an emission wavelength of 450 to 480 nm from the sapphire substrate side. Further, the light emitting element 18 is provided with a phosphor layer 19 so as to cover the upper surface and side surfaces.

The phosphor layer 19 includes a phosphor 19a for obtaining white light in a transparent resin such as silicon resin, epoxy resin, fluororesin, urea resin, or translucent resin. The upper surface, the lower surface, and all the side surfaces are provided with a predetermined thickness. An inorganic fluorescent material or an organic fluorescent material can be used for the phosphor 19a. Examples of inorganic fluorescent materials include materials containing rare earth elements, specifically YAG (yttrium, aluminum, garnet) based phosphors, which are made of Y, Lu, Sc, La, Gd and Sm. A garnet-based phosphor activated with cerium comprising at least one element selected from the group consisting of and at least one element selected from the group consisting of Al, Ga and In. For example, Y ₃ Al ₅ O ₁₂ : Ce.

(Configuration of light emitting element)
FIG. 2 shows a configuration of the light emitting element 18. The light emitting element 18 has a buffer layer 182 made of AlN, a clad layer 183 made of n-type GaN, a multi quantum well (MQW) layer 184, a clad layer 185 made of p-type AlGaN, on one surface of a sapphire substrate 181. A contact layer 186 made of p-type GaN is sequentially crystal-grown. Further, a p-side electrode 187 is provided on an exposed surface other than the side surface of the contact layer 186, and an exposed surface other than the side surface of the cladding layer 183 is provided on the exposed surface. An n-side electrode 188 is provided. Bumps 17A (shown in FIG. 1) are connected to the p-side electrode 187, and bumps 17B (shown in FIG. 1) are connected to the n-side electrode 188.

  Note that a substrate made of silicon, silicon carbide, zinc oxide, gallium phosphide, magnesium oxide, or the like can be used instead of the sapphire substrate 181.

(Operation of light emitting device)
Next, the operation of the light emitting device 1 will be described with reference to FIG. 1 and FIG. When a predetermined DC voltage is applied between the first and second electrodes 13A and 13B, the first electrode 13A → the via hole 12A → the conductor pattern 11A → the via hole 15A → the bump 17A → the light emitting element 18 → the bump 17B → the via hole 15B → the conductor. A drive current flows through the path of the pattern 11B → the via hole 12B → the second electrode 13B.

  The light emitting element 18 emits blue light from the MQW layer 184 shown in FIG. 2 and emits upward in FIG. Blue light from the light emitting element 18 is incident on the phosphor layer 19, part of which is absorbed by the phosphor 19 a, and the rest is transmitted through the phosphor layer 19 as it is. The phosphor 19a absorbs blue light and converts it into yellow light. Both the yellow light and the blue light transmitted through the phosphor layer 19 are emitted to a range of about 180 ° on the upper surface of the light emitting element 18 in FIG. 1, and the white light obtained by mixing the two lights is a light guide plate. Etc.

(Effects of the first embodiment)
According to the first embodiment, the following effects are obtained.
(A) Since the light-emitting element 18 does not have a package and a mortar-shaped reflector, there is nothing that blocks the light exit surface, and the light distribution range can be widened. There will be no unevenness.
(B) Since the light distribution range of the light emitting element 18 can be widened by the above (a), the number of the light emitting devices 1 used in the backlight device can be reduced.

In the first embodiment, white light is obtained by combining the light emitting element 18 whose emission color is blue light and the phosphor layer 19 that excites yellow light. However, the present invention is not limited to this. Absent. For example, a light emitting element capable of emitting ultraviolet light having a main light emission peak in a short wavelength region near 400 nm may be used as the light emitting element 18. In this case, the phosphor layer 19 is preferably composed of a resin or glass that is relatively resistant to ultraviolet light and a fluorescent material that can absorb visible light and emit visible light. Examples of such fluorescent materials that can fluoresce red, blue, and green with light having a short wavelength include Y ₂ O ₂ S: Eu as a red phosphor and Sr ₅ (PO ₄ ) ₃ Cl as a blue phosphor: Eu and (SrEu) O.Al ₂ O ₃ are available as green phosphors, and white light can be obtained by containing these in an ultraviolet resistant resin or the like.

  Further, when the light emitting device 1 is used for a backlight device or the like in which the backlight light requires a color other than white light, for example, a single color light such as red, a red light emitting element is used as the light emitting element 18 and fluorescent light is used. There is no need to provide the body layer 19.

[Second Embodiment]
(Configuration of light emitting device)

  3A and 3B show a light emitting device according to a second embodiment of the present invention, where FIG. 3A is a plan view and FIG. 3B is a front view. In the figure, the light-emitting device 2 is shown in cross section. In the present embodiment, the light emitting device 2 is configured using light emitting elements of three colors that emit R (red), G (green), and B (blue).

  The light emitting device 2 is mounted in a row on the plate-shaped first substrate 21, the second substrate 22 having the protrusion 22 a and laminated on the first substrate 21, and the second substrate 22. The light emitting elements 23 to 25 and the translucent sealing member 28 provided on the upper surface of the protruding portion 22a so as to fill the light emitting elements 23 to 25 are provided. As the sealing member 28, for example, a transparent resin such as a silicon resin, an epoxy resin, a fluororesin, or a urea resin can be used.

  The first and second substrates 21 and 22 are, for example, substrates having a ceramic insulating layer, and internally include conductor patterns connected to the light emitting elements 23 to 25, via holes (both not shown), and The electrodes 26A, 26B, and 26C connected to the conductor pattern and the common electrode 27 in which the anodes or cathodes of the electrodes 26A to 26C are connected in parallel. In addition, the 1st board | substrate 21 and the 2nd board | substrate 22 are bonded together by the adhesive agent etc. similarly to 1st Embodiment, and are integrated.

  The light emitting element 23 is an LED element made of, for example, AlGaAs, GaP, GaAsP or the like, and emits red light. The light emitting element 24 is an LED element made of, for example, GaP, and emits green light. The light emitting element 25 is an LED element made of, for example, InGaN, GaN or the like, and emits blue light. In addition, although the light emitting elements 23-25 are mounted on the protrusion part 22a of the 2nd board | substrate 22 at predetermined intervals, the arrangement order can be made arbitrary.

(Operation of light emitting device)
Next, the operation of the light emitting device 2 will be described. When a DC voltage having a predetermined value is applied between the electrodes 26 </ b> A to 26 </ b> C and the common electrode 27, a driving current flows through the light emitting device 2. When the drive current flows, the light emitting elements 23 to 25 emit red light, green light, and blue light at the same time, pass through the sealing member 28, and then emit upward. Light of three colors from the light emitting elements 23 to 25 is obtained by mixing light of three colors of R, G, and B above the light emitting device 2.

  Note that one or two of the light emitting elements 23 to 25 are turned on to obtain a single color or a mixed color of two colors.

(Effect of the second embodiment)
According to the second embodiment, the following effects are obtained.
(A) Since the light emitting device 2 does not have a package and a reflector, there is no light blocking surface, so that the light distribution range can be widened, and even when used in a backlight device or the like, luminance unevenness is not generated. It does not occur. Further, by simultaneously lighting the light emitting elements 23 to 25, the amount of light can be increased as compared with the first embodiment.
(B) By providing the sealing member 28 so as to cover the light emitting elements 23 to 25, the light emitting elements 23 to 25 can be protected from impact or the like.

  In the second embodiment, the light emitting elements of three colors R, G, and B are separately prepared to obtain white light. However, there is one bare chip of three colors R, G, and B. You may use the light emitting element of the structure mounted in the chip | tip. In FIGS. 3A and 3B, the light emitting elements 23 to 25 are arranged in a line, but may be arranged at the vertices of the inner angles of the equilateral triangle.

(First embodiment)
FIG. 4 shows a first embodiment of the present invention. This example is a side-view type backlight device using a plurality of the light-emitting devices of the first embodiment. The backlight device 3 includes a plate-shaped light guide plate 32 in which a plurality of recesses 31 are provided on one side at predetermined intervals, and the protrusions 16a of the light emitting device 1 shown in FIG. The configuration is such that the light guide plate 32 is adhered with an adhesive or the like. The inner surface of each recess 31 serves as a light introduction end surface for the emitted light of the light emitting device 1. Note that the recess 31 may be filled with an epoxy resin or a silicon resin.

  The light guide plate 32 is a plate-like body made of a translucent resin such as methacrylic resin. In a backlight device for a liquid crystal display panel, a reflection sheet, a diffusion sheet or the like is usually provided on one surface of the light guide plate 32, and a polarizing plate or a liquid crystal display panel is provided on the other surface. Are not shown in FIG. 4.

  In the configuration of FIG. 4, when each light emitting device 1 is energized, the emitted blue light enters the light guide plate 32, and after being repeatedly reflected in the light guide plate 32, is emitted in the thickness direction. Illuminate the liquid crystal display panel from the back.

  According to this embodiment, light from the light emitting device 1 is emitted in a direction of approximately 180 ° through the respective recesses 31, and an obstacle such as a package that blocks the light exists between the light emitting devices 1. Therefore, even if the interval between the light emitting devices 1 is increased, luminance unevenness does not occur in the backlight device 3.

  In the first embodiment, the light emission color of the light emitting device 1 is not limited to blue, and an arbitrary color can be used.

(Second embodiment)
FIG. 5 shows a second embodiment of the present invention. In the present embodiment, the light emitting device 1 shown in FIG. 1 has a light emitting device 4 provided with a translucent resin layer 50 in place of the phosphor layer 19, and the other configurations are the same as those in FIG.

  Since the light emitting device 4 of the second embodiment does not have the phosphor layer 19, the blue light from the light emitting element 18 passes through the resin layer 50 as it is and is emitted in a direction of approximately 180 °. Therefore, when used in a backlight device, the illumination light becomes blue light.

  According to this embodiment, by providing the resin layer 50, the light emitting device 4 can be protected from impact or the like.

(Third embodiment)
FIG. 6 shows a third embodiment of the present invention. In this embodiment, the backlight device 3 shown in FIG. 4 uses the light-emitting device 4 shown in FIG. 5 instead of the light-emitting device 1, and further includes a phosphor portion 33 on the light guide plate 32. Other configurations are the same as those of the first embodiment shown in FIG.

  The light guide plate 32 includes a phosphor 33a having the same component as the phosphor 19a in the first embodiment and a plurality of concave portions 31 provided at predetermined intervals, and the phosphor portion 33. And a plate-like main body 34 provided integrally therewith. Note that the recess 31 may be filled with an epoxy resin or a silicon resin.

  In a backlight device for a liquid crystal display panel, a reflection sheet, a diffusion sheet or the like is usually provided on one surface of the light guide plate 32, and a polarizing plate or a liquid crystal display panel is provided on the other surface. Are not shown in FIG. 6.

  In the configuration of FIG. 6, when the light emitting element 18 of each light emitting device 4 is energized, the emitted blue light enters the phosphor portion 33 of the light guide plate 32. The phosphor 33a of the phosphor portion 33 is excited by the blue light from the light emitting device 4, and converts the blue light into yellow light. The white light in which the yellow light and the blue light that has passed through the phosphor portion 33 are mixed is incident on the main body portion 34 of the light guide plate 32, and after being repeatedly reflected in the light guide plate 32, the thickness direction To illuminate the liquid crystal display panel and the like from the back.

  According to this embodiment, light from the light emitting device 4 is emitted in a direction of approximately 180 ° through the respective recesses 31, and an obstacle such as a package that blocks light exists between the light emitting devices 4. Therefore, even if the interval between the light emitting devices 4 is increased, the backlight device 3 does not have uneven brightness. Furthermore, white light can be obtained by providing the phosphor portion 33.

[Other embodiments]
The present invention is not limited to the above embodiments, and various modifications can be made without departing from or changing the technical idea of the present invention. For example, the first and second substrates are bonded to each other, but may be configured to be integrated when the ceramic is sintered.

  Further, the case where the present invention is applied to a backlight device of a liquid crystal display panel has been described. However, the present invention is not limited to the backlight device, and a light source such as a display lamp or a traffic light in which light emitting devices are arranged in a matrix. Can also be used. Or it can also be used for the light source of switches, such as an electronic device.

It is sectional drawing which shows the light-emitting device which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the light emitting element of FIG. The light-emitting device which concerns on the 2nd Embodiment of this invention is shown, (a) is a top view, (b) is a front view. It is a top view which shows the 1st Example of this invention. It is a top view which shows the 2nd Example of this invention. It is a top view which shows the 3rd Example of this invention.

Explanation of symbols

1, 2, 4 Light emitting device 3 Backlight device 10 Ceramic insulating layers 11A, 11B Conductor patterns 12A, 12B Via holes 13A, 13B Electrodes 14 First substrate 15A, 15B Via holes 16 Second substrate 16a Protrusion 16b Reference surface 16c Element Mounting surface 17A, 17B Bump 18 Light emitting element 19 Phosphor layer 19a Phosphor 20 Ceramic insulating layer 21 First substrate 22 Second substrate 22a Protruding portions 23-25 Light emitting elements 26A-26C Electrode 27 Common electrode 28 Sealing member 31 Recess 32 Light guide plate 33 Phosphor 33 a Main body 50 Resin layer 100 Mount 181 Sapphire substrate 182 Buffer layer 183 Cladding layer 184 MQW layer 185 Cladding layer 186 Contact layer 187 p-side electrode 188 n-side electrode

Claims (7)

A plurality of light emitting devices arranged in an array; and
A light guide plate that emits light introduced from the plurality of light emitting devices through the light introduction end face to the back surface of the liquid crystal display panel;
The plurality of light emitting devices are:
A mount having an element mounting portion that exposes the first and second leads on the element mounting surface and protrudes from the flat surface;
A light emitting device having first and second electrodes connected to the first and second leads and mounted on the device mounting surface of the device mounting portion;
The mount is
A plate-like first substrate;
A second substrate having the element mounting portion and being stacked on the first substrate;
The light guide plate has a recess for positioning the element mounting portion of the mount on the light introduction end surface,
The liquid crystal display backlight device, wherein the plurality of light emitting devices do not include a light shielding member that blocks light emitted from each light emitting device between the light emitting devices. The liquid crystal display backlight device according to claim 1 , wherein the light emitting element is a light emitting diode that emits blue light or ultraviolet light. The liquid crystal display backlight device according to claim 1 , wherein the light emitting element is a light emitting diode that emits three colors of red, green, and blue. 4. The liquid crystal display backlight device according to claim 3 , wherein each of the red, green, and blue light emitting diodes is covered with a translucent sealing member. The light-emitting element is provided with a light-transmitting phosphor layer including a phosphor excited by light from the light-emitting element so as to cover a light emitting surface of the light-emitting element. Item 2. A backlight device for liquid crystal display according to item 1 . 2. The backlight device for a liquid crystal display according to claim 1 , wherein the light emitting element is provided with a light-transmitting resin layer so as to cover a light emitting surface of the light emitting element. The light guide plate, a liquid crystal display backlight apparatus according to claim 1, characterized in that it comprises a containing a phosphor to a predetermined width facing the recessed region.