JP2003076287A - Backlight device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat radiating effect in a backlight device using semiconductor elements. SOLUTION: This invention relates to the backlight device which comprises a light transmission plate 1 having a light incident face 1a on an end face, a light exit face 1b on the front surface, and a light source 2 constituted by mounting a plurality of LEDs 10 in a columnar form on one face of a film substrate 21 with a light-emitting face made almost vertical to the mounting face, and which is housed in a rectangular frame 31 and a planar frame 32 in the state in which one face of a film substrate 21 is mounted on the surface of the light transmission plate 1 so that the light emitting surface of the LEDs 10 in this light source 2 is closely stuck on the light incident face 1a of the light transmission plate 1, a metallic thin film 23 for heat radiating is arranged almost on the whole other surface where the LEDs 10 in the film substrate 21 for the light source 2 are not mounted, and also this metallic thin film 23 is pressed by a side frame 31a of the rectangular frame 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source type backlight device used in a liquid crystal display device or the like.

[0002]

2. Description of the Related Art Conventionally, a planar light source type backlight device includes a light guide plate made of a wedge-shaped acrylic plate, and a discharge lamp arranged so that one end of the light guide plate is a light incident surface and faces the surface. It is composed of a metal frame for housing these.

Further, the backlight device includes a reflector for reflecting the light emitted from the discharge lamp in the direction opposite to the light guide plate toward the light guide plate, and a diffusion sheet or prism sheet attached to the light emitting surface which is the surface of the light guide plate. And a reflection sheet attached to the light reflection surface which is the back surface of the light guide plate.

In recent years, a backlight device using a light emitting diode (LED) instead of the discharge lamp has been considered. The use of LEDs eliminates the need for high-voltage components such as piezoelectric inverters, which were necessary for discharge lamps, and enables the circuit board to be downsized, and also has the advantage of eliminating the effects of noise due to high voltage. Also,
With a discharge lamp, a thin backlight with a light guide plate having a thickness of 1 mm or less, which is almost impossible, is also possible.

[0005]

However, the LED
Due to its characteristics, it has a characteristic of generating heat at a high temperature when a large amount of current is passed, and there is a problem in that it is susceptible to the heat of the peripheral portion of the LED. Therefore, it is necessary to suppress the current value to a specified value in order to maintain the characteristics of the LED itself, and it is necessary to increase the number of LEDs in order to improve the light emission amount as a light source.

[0006]

The present invention has been made to solve the above problems. That is, according to the present invention, a light guide plate having a light incident surface on the end surface and a light emitting surface on the surface, and a plurality of semiconductor light emitting elements having a light emitting surface substantially perpendicular to the mounting surface are arranged in a line on one surface of the film substrate. A light source that is mounted, and is housed in a metal frame with one surface of the film substrate attached to the surface of the light guide plate so that the light emitting surface of the semiconductor light emitting element in this light source is brought into close contact with the light incident surface of the light guide plate. In the backlight device, a metal thin film for heat dissipation is provided on almost the entire other surface of the film substrate of the light source on which the semiconductor light emitting element is not mounted,
The metal thin film is pressed by the metal frame.

In the present invention as described above, the film substrate on which a plurality of semiconductor light emitting devices are mounted is provided on almost the entire other surface of the film substrate.
Since a metal thin film for heat dissipation is provided and this metal thin film is pressed by the metal frame, it is possible to dissipate the heat generated by the multiple semiconductor light emitting elements from the metal thin film to the metal frame, resulting in a high heat dissipation effect. You will be able to get it.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view illustrating a backlight device according to this embodiment. That is, the backlight device according to the present embodiment is mainly used for illumination of a liquid crystal display device, and uses a plurality of LEDs 10 which are semiconductor light emitting elements as a light source.

The backlight device has a light incident surface 1 on the end face.
a, a light guide plate 1 having a light emitting surface 1b on its surface, a light source 2 including a film substrate 21 made of a flexible tape for mounting a plurality of LEDs 10 in a row and a metal reflector 22, and a light source 2 attached to the light guide plate 1. The frame-shaped frame 31 and the planar frame 3 that store and hold them in the closed state
2 and.

On the light emitting surface 1b of the light guide plate 1, a diffusion plate 41, a vertical prism sheet 42, a horizontal prism sheet 43 and a polarizing sheet 44 are sequentially arranged as optical sheets. Further, the light-incident surface 1a of the light guide plate 1 is adhered to the light-incident surface 1a of the plurality of LEDs 10 mounted on the film substrate 21 with the white double-sided tape 5 so that the light-emission surfaces (surfaces substantially vertical to the mounting surface) of the LEDs 10 are closely attached. Has been.

That is, in this embodiment, a so-called side-view type element that emits light from a surface (side surface) substantially perpendicular to the mounting surface is used as the LED 10. This allows LE
When the film substrate 21 on which D10 is mounted is attached to the light guide plate 1, the surface (mounting surface) of the film substrate 21 and the light guide plate 1
The surface (light emitting surface 1b) can be firmly bonded over a wide area.

Further, the thickness of the light incident surface 1a of the light guide plate 1 can be made substantially equal to the thickness of the LED 10, for example, 1 m.
It is also possible to reduce the thickness of the backlight device by using the light guide plate 1 having a thickness of m or less.

A light reflecting surface 1c which is the back surface of the light guide plate 1
A reflection sheet 45 is arranged in the. This reflection sheet 45
Thus, the light traveling toward the back surface of the light guide plate 1 can be efficiently reflected to the light emitting surface 1b side.

Here, in order to maintain the luminous efficiency of the LED 10, by releasing the heat generated from the LED 10,
It is important to maximize the characteristics of the LED 10. That is, if the junction temperature of GaN (gallium nitride) increases by 1 ° C., the luminous efficiency decreases by about 1%. Further, from the viewpoint of the luminous efficiency of the LED 10, the more current is applied, the more heat is generated and the amount of light cannot be obtained. Moreover, LED10
Due to the lifetime of the package and the sealing resin, it is impossible to flow a large amount of current.

Therefore, in this embodiment, the film substrate 2
A metal thin film 23 for heat dissipation is provided on almost the entire surface of the first LED 10 which is not mounted. A soft aluminum sheet 24 is attached to the metal thin film 23 as needed.

The metal thin film 23 and the soft aluminum sheet 24
By pressing the horizontal frame 31a of the frame-shaped frame 31, the heat generated in the LED 10 can be radiated from the metal thin film 23 to the frame-shaped frame 31 and the planar frame 32 to be efficiently radiated. Furthermore, the frame-shaped frame 31
The horizontal frame 31a and the metal reflector 22 are attached by the heat radiation film sheet 25, and the heat radiation effect is further improved.

Next, a method of manufacturing the backlight device according to this embodiment will be described. First, as shown in FIG. 2A, the film substrate 21 is molded on the film base material 20 and a predetermined wiring pattern 21b is formed.
Further, as shown in FIG. 2B, the thin film metal 23 is deposited on almost the entire back surface of the film substrate 21.

FIG. 2 (c) is an enlarged view of part A of FIG. 2 (b). In the portion where the wiring pattern 21b of the film substrate 21 extends, a cutout portion 21c is provided in the peripheral portion corresponding to the wiring pattern 21b from the viewpoint of preventing a short circuit with the outside, and at the corresponding portion of the thin film metal 23, Notch 21
A notch 23a which is slightly larger than c is provided.

Next, the wiring pattern 2 of the film substrate 21
Applying a cream solder by printing on a predetermined part of 1b,
A chip mounter is used to mount components such as LEDs (not shown), thermistors, and electrostatic breakdown prevention resistors on these, and each component is soldered to the wiring pattern 21b through a reflow furnace. Then, the film substrate 21 is separated from the base material 20 using a mold or the like.

Next, as shown in FIG. 3, a soft aluminum sheet is attached to the separated metal thin film 23 of the film substrate 21 if necessary.

Next, as shown in FIG. 4 (a), the metal reflector 22 is attached to the light incident surface 1a side of the light guide plate 1 by another operation. At this time, the metal reflector 22 and the light incident surface 1a
A hole for accommodating the light source is formed between and.

As shown in FIG. 4B, which is a partially enlarged side view of FIG. 4A, a recess is provided on the light incident surface 1a side of the light emitting surface 1b of the light guide plate 1. With this recess, the light source is used as a white double-sided tape 5 (see FIG. 1) in a later step.
The film substrate 21 of the light source becomes substantially the same surface as the light emitting surface 1b of the light guide plate 1 when it is attached.

Next, as shown in FIG. 5, a white double-sided tape 5 is attached to a concave portion (see FIG. 4B) on the light incident surface 1a side of the light emitting surface 1b of the light guide plate 1, and through this. The film substrate 21 is attached. At this time, the film substrate 21
The LED 10 mounted on the LED 1 is housed in the hole between the metal reflector 22 and the light incident surface 1a, and
The light emitting surface of 0 is in close contact with the light incident surface 1a of the light guide plate 1.

Next, as shown in FIG. 6, after the polarizing sheet 44, the horizontal prism sheet 43, the vertical prism sheet 42, and the diffusion plate 41, which are optical sheets, are sequentially stacked in the frame of the frame frame 31, As shown in FIG. 7, the light guide plate 1 to which the light source is attached is housed so as to overlap with the optical sheets (the polarizing sheet 44, the horizontal prism sheet 43, the vertical prism sheet 42, and the diffusion plate 41) of the frame-shaped frame 31. At this time, the claws provided on the light guide plate 1 are fitted and fixed in the holes of the frame-shaped frame 31.

Next, as shown in FIG. 8, the frame-shaped frame 3
After stacking the reflection sheet 45 on the light guide plate 1 housed in 1, the planar frame 32 serving as the back cover is fitted into the frame frame 31. By combining the frame-shaped frame 31 and the planar frame 32 into a box as in the present embodiment, the strength of the frame can be improved, and the alignment when used in a liquid crystal display device or the like can be accurately performed. This makes it possible to prevent light leakage through the gap between the frame and the liquid crystal display device.

Further, the planar frame 32 is replaced by the frame-shaped frame 3
The horizontal frame 3 of the frame-shaped frame 31
1a (see FIG. 1) is in a state of pressing the metal thin film 23 of the film substrate 21, and the heat of the LED 10 is generated by the metal thin film 23.
Can be released from the frame-shaped frame 31 to the planar frame 32.

Finally, as shown in FIG. 9, in order to suppress the floating between the frame-shaped frame 31 and the film substrate 21, a heat-dissipating film sheet 25 having a thickness of about 50 μm is attached from the frame-shaped frame 31 to the metal reflector 22. wear. As a result, the backlight device of this embodiment is completed.

In the backlight device of this embodiment, LE
Since a so-called side-view type in which a surface (side surface) substantially vertical to the mounting surface is used as D10 is used, the attachment surface of the film substrate 21 and the surface of the light guide plate 1 can be made parallel to each other, and Since the area can be increased, the film substrate 21 can be firmly fixed to the light guide plate 1. As a result, even if stress is applied to the soldered portion of the LED 10 or the like when the routing portion of the wiring extending from the film substrate 21 is curved, the occurrence of peeling of the soldered portion can be suppressed.

Further, in the backlight device having such a structure, the metal thin film 23 for heat dissipation is formed on the film substrate 21.
The following heat dissipation effect can be obtained as compared with the case where no is formed. That is, when the metal thin film 23 is not provided, the applied current to the LED 10 is 17 mA and the LED 10 is
In contrast to the temperature of the soldered part of 66 ° C., the temperature of the soldered part of the LED 10 becomes 65 ° C. with the current applied to the LED 10 of 23 mA in this embodiment (when the metal thin film 23 is present).

Further, in the backlight device of this embodiment, as shown in FIG. 10, a plurality of (five in this example) LEDs 10 are mounted in a row on the film substrate 21, but the frame-shaped frame 31 Horizontal frame 31a (see FIG. 1)
By changing the shape of the
It may be changed according to the heat generation amount of 10.

That is, in the case where the LED arranged in the center of the plurality of LEDs 10 has a large heat generation amount, the horizontal frame 3
The contact area of 1a is made wider toward the center as shown in the graph in the figure. In this way, in order to change the contact area between the horizontal frame 31a and the metal thin film 23 depending on the position of the LED 10, for example, the shape of the horizontal frame 31a is made into a trapezoidal shape so that the central portion is in wide contact with the metal thin film 23.

By changing the shape of the horizontal frame 31a in this way, it is possible to improve the heat dissipation efficiency of the widely contacted portion and make the temperatures of the plurality of LEDs 10 uniform.

In this embodiment, an example in which a flexible cable is used as the film substrate 21 is shown, but the same applies when a glass epoxy substrate is used. It is also applicable when using a semiconductor light emitting element other than an LED. Further, although the white double-sided tape 5 is used for attaching the film substrate 21, a double-sided tape made of a material whose one side is reflected may be used.

In the present embodiment, the side-view type LED 10 is used, but the top-view type LED 10 is used, and the frame-like frame is provided with a leaf spring structure from the back side and pushed from the back side. Can also obtain the same effect.

[0035]

As described above, the present invention has the following effects. That is, it is possible to obtain a high heat dissipation effect even in a backlight device using a light source that uses a semiconductor light emitting element. As a result, a larger amount of current can be passed than in the conventional case, and the number of semiconductor light emitting elements can be reduced. In particular, according to the present invention, it is possible to internally disperse heat and directly dissipate heat to the frame housing, and it is possible to apply the present invention to a device (digital still camera, video camera, etc.) using a CCD (solid-state image sensor) with severe temperature conditions. .

[Brief description of drawings]

FIG. 1 is an exploded perspective view illustrating a backlight device according to this embodiment.

FIG. 2 is a schematic plan view illustrating manufacturing of a film substrate.

FIG. 3 is a schematic side view illustrating attachment of a soft aluminum sheet.

FIG. 4 is a diagram for explaining attachment of a metal reflector.

FIG. 5 is a schematic perspective view illustrating attachment of a light source.

FIG. 6 is a schematic perspective view illustrating attachment of an optical sheet.

FIG. 7 is a schematic cross-sectional view illustrating attachment of a light guide plate.

FIG. 8 is a schematic cross-sectional view illustrating attachment of the planar frame.

FIG. 9 is a partially enlarged cross-sectional view illustrating attachment of a heat dissipation film sheet.

FIG. 10 is a schematic diagram illustrating a contact area with a metal thin film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light guide plate, 1a ... Light incident surface, 1b ... Light emitting surface, 2 ... Light source, 20 ... Base material, 21 ... Film substrate, 22 ... Metal reflector, 23 ... Metal thin film, 31 ... Frame frame, 31a
... Horizontal frame, 32 ... Planar frame, 41 ... Diffusing plate, 4
2 ... Vertical prism sheet, 43 ... Horizontal prism sheet, 44
… Polarizing sheet, 45… Reflecting sheet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F21V 8/00 F21V 8/00 601Z G02F 1/13357 G02F 1/13357 // F21Y 101: 02 F21Y 101: 02 (72) Inventor Toshiaki Igawagawa, 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo, Sony Corporation (72) Hirokazu Nakayoshi 6-7-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term, Sony Corporation (Reference) 2H091 FA23Z FA45Z LA04 5G435 AA12 BB12 BB15 EE05 EE06 EE27 FF08 GG23 GG26 KK02 LL07

Claims (4)

[Claims] 1. A light guide plate having a light incident surface on an end surface and a light emitting surface on the surface, and a plurality of semiconductor light emitting devices having a light emitting surface substantially perpendicular to the mounting surface mounted on one surface of a film substrate in a row. And a light source of the semiconductor light emitting element in the light source is housed in a metal frame with one surface of the film substrate attached to the surface of the light guide plate so that the light emitting surface of the semiconductor light emitting element closely contacts the light incident surface of the light guide plate. In the backlight device, a metal thin film for heat dissipation is provided on almost the other surface of the film substrate of the light source on which the semiconductor light emitting element is not mounted, and the metal thin film is pressed by the metal frame. A backlight device characterized by being provided. 2. The backlight according to claim 1, wherein a contact area of the metal thin film with the metal frame is set according to heat generation amounts of a plurality of semiconductor light emitting elements mounted on the film substrate. apparatus. 3. A notch is provided in a part of the metal thin film formed on the other surface of the film substrate, corresponding to the wiring pattern formed on the one surface of the film substrate. The backlight device according to claim 1. 4. The frame is composed of a frame-shaped frame attached to a peripheral edge of the light guide plate and a plate-shaped frame attached to one surface side of the light guide plate. Backlight device.