JP3463613B2 - Surface emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light emitting device using a light emitting diode as a light source which can be used as a light source for a backlight of a liquid crystal display section of a viewfinder of a video camera or the like.

[0002]

2. Description of the Related Art A liquid crystal display having a small size and a low power consumption is widely used as a display unit of a mobile phone or the like. This liquid crystal display is arranged so that the liquid crystal panel faces the display surface side, and is often equipped with a backlight so that characters and images can be seen even in a dark place. A full-color liquid crystal display screen provided in a viewfinder of a video camera or other liquid crystal monitors is also usually provided with a backlight.

The liquid crystal display portion of a mobile phone is generally a backlight that shines in a single color. Rather than increasing the surface brightness of the display surface, the display surface is made uniform so that there is no difference in brightness. It is necessary to emit light. On the other hand, in the case of full-color liquid crystal display, not only the brightness of the entire display surface needs to be uniformed but also the surface luminance needs to be increased, and thus white-emitting LEDs have been used recently. And
The light distribution to the liquid crystal panel is basically the same in that the light guide plate is used, and FIG. 6 shows a schematic view of a typical example of a backlight structure including the light guide plate. (A) is a longitudinal cross-sectional view of a main part, and (b) is a right side view of the same figure (a).

Referring to FIG. 6, in the conventional backlight structure, a light guide plate 52 using a transparent acrylic plate is arranged above a printed wiring board 51, and the light guide plate 5 is also provided.
2 is provided with a liquid crystal display panel 53 in which liquid crystal is sealed, and a surface mount type light emitting diode (hereinafter referred to as “LED”) 54 mounted on the printed wiring board 51 is provided as a light source. In the light guide plate 52, the side on which the LED 54 is arranged has an edge surface 52a of approximately 45 ° and the LED 54
The light from the surface is totally reflected and made incident, and this edge surface 5
Mirror 52b is arranged along 2a
The reflected light from is made incident. Then, a pattern 52c of minute unevenness is formed on the surface opposite to the surface of the light guide plate 52 facing the liquid crystal display panel 53, and the LE which has entered the light guide plate 52 is entered.
The light from D54 is diffused by the concavo-convex pattern 52c and is irradiated so that the entire liquid crystal display panel 53 has uniform brightness. It should be noted that two LEDs 54 are generally arranged along the right side of the light guide plate 52 as in the example shown in the figure, or more LEDs are provided for higher brightness.

[0005]

The LED 54 used as a light source for such a backlight has recently been made higher in brightness, and in particular, a white light emitting device using a GaN compound semiconductor has been adopted. It was

However, due to the higher brightness of the LED 54, the light distribution distribution near the LED 54 inevitably becomes higher. For this reason, the displayed image is divided into a clear portion and a non-clear portion, which makes it difficult to see the image. Further, since the light emitted from the LED 54 indirectly enters the liquid crystal display panel 53 through the light guide plate 52, the light guide plate 5
Attenuation of the amount of light while passing through 2 also impairs high brightness.

As described above, in the conventional surface light emitting device used for the backlight structure, the surface light emission having uniform brightness can be obtained as the LEDs used as the light source have higher brightness and the number of LEDs decreases. Absent. In addition, since light is incident indirectly through the light guide plate, there is a large amount of light leakage from the light guide plate, and the light cannot be efficiently incident on the light guide plate. High brightness cannot be achieved unless used. Moreover, since a large number of LEDs are used, there is a problem that the price is high, the power consumption is high, and the structure is complicated.

It is an object of the present invention to achieve low brightness, low power consumption, small size, high uniformity, and high brightness in a surface emitting device used as a backlight of a liquid crystal display panel or the like.

[0009]

The present invention comprises a light emitting element mounted on a conductive material, and a reflective diffusion layer for accommodating the light emitting element and reflecting and diffusing the emitted light toward the illumination target side. The diffusion layer surrounds at least the periphery of the light emitting element and has a reflective surface in the light emitting direction formed on the inner surface thereof, and a space between the light emitting element and the reflective surface in the reflective frame. A light-transmitting light guide plate that is partially or wholly immersed and that receives light from the light-emitting element and emits surface light toward the illumination target side, and is provided between the light-emitting element and the illumination target. It is characterized in that it is provided with a means for making the irradiation light amount distribution to the object uniform.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 comprises a light emitting element mounted on a conducting material, and a reflective diffusion layer for accommodating the light emitting element and reflecting and diffusing the emitted light toward the illumination target side. The reflection-diffusion layer surrounds at least the periphery of the light-emitting element and has a reflection surface in which a reflection surface in the light-emitting direction is formed on the inner surface, and the reflection frame is spaced apart from the light-emitting element and the reflection surface. A light-transmissive light guide plate, which is partially or wholly immersed therein and which receives light from the light emitting element and surface-emites toward the illumination target side, the reflection surface and the light guide plate.
Transparent to fill the gap between and seal around the light emitting element
And a resin layer, a period from the light emitting element to the illumination target, spaced between 且 one said reflective surface, uniform the irradiation light amount distribution of the light traveling directly to the illumination target Means for adjusting the irradiation light amount distribution to the illumination target.
The light emitting element of the light guide plate is
The light from the light emitting element is directed to the light guide plate at the incident surface facing the light guide plate.
Of the light distribution section and the light guide plate which are incident with a uniform light distribution.
The light is emitted from the light guide plate to the emission surface facing the illumination target side.
A surface emitting device characterized by comprising a diffusing section for diffusing the reflected light toward the illumination target side, even if the light emitting element is arranged so as to correspond to the central portion of the light guide plate, Light is uniformly incident on the light guide plate by the means for uniformizing the distribution of the irradiation light amount to the illumination target, and only the light-emitting element portion does not have locally high brightness, but the uniform brightness toward the illumination target side. Is obtained. Moreover, the light extraction efficiency is improved by the transparent resin layer.
Since it goes up, it improves the utilization efficiency of light from the light emitting element.
be able to.

[0011]

[0012]

[0013]

[0014]

[0015] According to a second aspect of the invention, the conducting material is a lead frame, according to claim, characterized in that it has integrally molded a reflective frame of the diffuse reflection layer on the lead frame
In the surface emitting device according to 1, the heat generated by the light emitting element can be released from the lead frame.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a surface emitting device according to the present invention.
(A) is a top view and (b) is a longitudinal cross-sectional view showing a part of it in an enlarged manner.

As shown in FIG. 1, the surface emitting device of the present invention has a wiring board 1 having a rectangular planar shape, a light emitting element 2 which is conductively mounted in the center of the wiring board 1, and a periphery of the light emitting element 2. And a reflective diffusion layer 3 for surface emission, which is formed on the wiring board 1. As shown in FIG. 6 of the conventional example, a liquid crystal display panel, a diffusion sheet, and a prism sheet (not shown) are arranged on the upper end of the surface emitting device, that is, on the reflection diffusion layer 3, and the reflection diffusion layer 3 is removed. This light is made to enter the liquid crystal display panel as a backlight.

The wiring board 1 is provided with a wiring pattern (not shown) that conducts to a power supply circuit on the equipment side when incorporated in equipment such as a viewfinder of a video camera, and the light emitting element 2 is mounted on the wiring pattern to conduct electricity. Let

The reflection / diffusion layer 3 includes a reflection frame 4 mounted on the wiring board 1, a light guide plate 5 arranged in the reflection frame 4 directly above the light emitting element 2, and the reflection frame 4 of these. And a transparent resin layer 6 filled between the light guide plates 5.

The reflection frame 4 is a component formed in advance by resin and placed on the wiring board 1 and fixed by an adhesive agent and heat caulking. The resin material of the reflection frame 4 is white, such as PBT or PC, and has a mortar shape 4 with a uniform inclination angle around the light emitting element 2.
The inclined surfaces are the inclined surfaces, and these inclined surfaces are the reflection surfaces 4a of the light from the side surface of the light emitting element 2. The base end of the reflecting surface 4a is at a position where it does not interfere with the light emitting element 2, and the inclination angle thereof is about 45 °, and the light from the light emitting element 2 is reflected right above so that the light from the surface emitting device is uniform. Decide to emit to.

The light guide plate 5 is made of a transparent acrylic resin or the like, and is prepared in the same manner as the reflection frame 4 and is attached to the reflection frame 4 or is transparent after the light guide plate 5 is attached. Seal with resin. The incident surface 5a at the lower end and the exit surface 5b at the upper end of the light guide plate 5 are in a substantially parallel relationship with each other, and are arranged on the reflection frame 4 so as to be orthogonal to the light emitting axis of the light emitting element 2 (the vertical direction in FIG. 1B). To assemble. The four side surfaces between the entrance surface 5a and the exit surface 5b have inclination angles that are substantially parallel to the reflection surfaces 4a located on the lower side when incorporated in the reflection frame 4.

The transparent resin layer 6 is made of a resin such as an epoxy resin or a silicone resin. As mentioned above, the transparent resin layer 6 seals the periphery of the light emitting element 2 and the emitting surface 5b serves as the upper end surface of the reflecting frame 4. The light guide plate 5 is integrated with the reflection frame 4 so that they have almost the same height.

When the light emitting element 2 is energized from the wiring board 1, the active layer of the light emitting element 2 emits light. In the present invention, the light emitting element 2 has the highest upward emission luminance in FIG. 1B, that is, has the upper surface of the light emitting element 2 as the main light extraction surface. As described above, in the light emitting element 2 with the main light extraction surface facing upward, the amount of light directed to the incident surface 5a of the light guide plate 5 is the largest, but the light from the active layer is emitted not only to the upper surface side but also to the side surface. Therefore, most of the light passing through the transparent resin layer 6 in the substantially horizontal direction is reflected by the reflecting surface 4 a of the reflecting frame 4.
Is reflected by and goes toward the light guide plate 5.

As described above, the components of the light from the light emitting element 2 are divided into those which are directly incident on the light guide plate 5 from the incident surface 5a and those which are incident sideways after being reflected by the reflecting surface 4a. . Therefore, if the components of the light incident from the light emitting element 2 directly on the incident surface 5a of the light guide plate 5 and the components reflected from the reflection surface 4a are adjusted to be substantially the same, the light exit surface 5b of the light guide plate 5 is adjusted. The whole can be set to almost uniform brightness. In order to adjust the brightness as described above, (b) of FIG.
As shown in FIG. 5, the adjustment pattern film 7 is formed on the incident surface 5a of the light guide plate 5 by, for example, silk screen printing.

As has been widely known in the past, silk screen printing is a method of printing by drawing ink on a plate with a squeegee and printing, and changing the interval between the plate and the squeegee or repeating it a plurality of times. The thickness of the ink can be freely changed by printing. A white ink may be used to provide a uniform thickness adjustment pattern. However, if the ink layer is printed so that it has a thin portion and a thick portion as necessary, light will not be emitted in the thin portion of the ink layer. A pattern is obtained in which light is blocked at the transparent and thick portions. Therefore, the form of the light-transmitting and light-shielding patterns of the adjustment pattern film 7 is set so that the light incident on the light guide plate 5 has substantially uniform brightness in consideration of the component of the light reflected from the reflecting surface 4a. .

Also, instead of forming the adjustment pattern film 7 by silk screen printing, a similar effect can be obtained even if a white film having a size of about 2.5 mmφ and made of PET is attached. can get.

Further, in order to make the luminance unevenness uniform,
The light diffusion portion 8 is formed on the emission surface 5b of the light guide plate 5.

FIG. 2 is a plan view and an enlarged vertical sectional view showing an example of the pattern of the light diffusion portion 8.

For example, the light diffusing portion 8 is an uneven portion formed by subjecting a metal mold to graining or blasting. The uneven portion may be uniform, but the uneven portion is deeper in the region closer to the light emitting element, and the pitch of the unevenness is smaller. As the distance from the light emitting element 2 increases, the uneven portion gradually becomes shallower and the pitch becomes smaller. It is formed to be large. That is, by making the emission surface of the light guide plate 5 rougher in the area closer to the light emitting element and reducing the amount of emitted light, it is possible to make the entire illumination even.

As described above, by the adjustment pattern film 7,
The light from the light emitting element 2 is uniformly incident on the light guide plate 5 and the light emitted from the light guide plate 5 is diffused by the light diffusing section 8, whereby a surface light emitting device with less uneven brightness can be realized.

In the above structure, when the light emitting element 2 is energized through the wiring board 1, the light is turned on, and the light from the main light extraction surface on the upper surface of the light emitting element 2 passes through the transparent resin layer 6 and enters the light guide plate 5. Head to surface 5a. Since the adjustment pattern film 7 is formed on the incident surface 5a by silk screen printing of white ink, as described above, only the central portion of the light guide plate 5 right above the light emitting element 2 has high brightness. The light amount is incident on the light guide plate 5 as a uniform light amount distribution over the entire light guide plate 5. The light emitted from the side surface of the light emitting element 2 is
It is reflected to the light guide plate 5 side by the reflection surface 4a of the reflection frame 4,
Most of the light is incident on the light guide plate 5 from the inclined side surfaces of the four directions. The light diffusing section 8 further improves the uniformity of the brightness of the entire surface emitting device.

Therefore, by disposing the liquid crystal display panel, the diffusion sheet, and the prism sheet on the surface emitting device, it is possible to display a high-brightness liquid crystal image with less uneven brightness.

In the example shown in FIG. 1, the adjustment pattern film 7 is formed on the incident surface 5a of the light guide plate 5 and the light diffusion portion 8 is formed on the emission surface 5b at the same time. By forming only 7 or only the light diffusion portion 8, it is possible to make the uneven brightness of the entire surface light emitting device uniform.

Further, since the transparent resin layer 6 is formed between the reflection frame 4 and the light guide plate 5, the light emitting element 2 emits light 5b.
There is no air layer in the optical path up to and the change in the refractive index in the optical path is small. Therefore, the emission intensity of light from the light emitting element 2 is less attenuated, and the light extraction efficiency can be increased.
Here, the transparent resin layer 6 is formed in order to realize a high-luminance surface emitting device, but in the case of using the ultra-high-luminance light emitting element 2, it is not necessary to form the transparent resin layer. Adjustment pattern film 7 so that the entire brightness is uniform
Should be formed.

Further, since the light emitting element 2 is arranged corresponding to the central portion of the light guide plate 5, it serves as a light source centered on the central portion of the display screen of the liquid crystal display panel, and along the edge of the light guide plate as in the conventional case. The efficiency of taking in light is better than the case where LEDs are arranged. That is, in the conventional structure in which the light emitting elements are arranged at the edge of the light guide plate, the efficiency of capturing light into the light guide plate is poor, and a plurality of light emitting elements are required to realize a high-luminance surface emitting device. become. On the other hand, in the present invention, since the light emitting element is mounted in the reflection frame 4 mounted on the wiring board 1 and is sealed with the transparent resin, the light use loss is small and the adjustment pattern film 7 is used. Since the overall brightness can be set uniformly by adjusting the light distribution and improving the uniformity by the light diffusing unit 8, it is possible to perform display with less brightness unevenness.

In this way, the adjustment pattern film 7 is formed on the incident surface 5a.
By including the light guide plate 5 in which the LE is formed,
Even when the light emitting element 2 of D is used as a light source, the entire display screen of the liquid crystal display panel can be uniformly illuminated and can be optimally used as a backlight. Further, as generally known as a structure of a liquid crystal display panel, a diffusion sheet and a prism sheet are provided on the surface emitting device to illuminate the liquid crystal display panel, so that the price is low, the power consumption is small and the size is small. This makes it possible to display with less uneven brightness.

The example of FIG. 3 is a bottom view showing an example in which a light distribution plate is provided on the incident surface 5a of the light guide plate 5.

In FIG. 3, a light distribution plate 10 made of metal or the like is integrally bonded or vapor-deposited on the incident surface 5a. The light distribution plate 10 has a light transmission hole 10a having a small opening diameter distributed in the central portion thereof and an opening diameter increasing toward the periphery. With such a distribution of the light transmission holes 10a having different opening diameters, the amount of passing light is small in the central portion directly above the light emitting element 2 and large in the peripheral portion. Therefore, as in the case of using the adjustment pattern film 7 of FIG. 1, the uneven brightness of the surface emitting device can be sufficiently improved.

In the example of FIG. 4, a pair of electrodes are formed on both front and back surfaces of the wiring board itself, and a light emitting element which is electrically connected to these electrodes is sealed by a resin package. It is a longitudinal cross-sectional view showing an example in which a light distribution layer 9a is provided in the upper resin package.

By forming the light distribution layer 9a on the surface-mounted LED 9 by silk screen printing as described above, the adjustment pattern film 7 is formed on the incident surface 5a of the light guide plate 5 of FIG. The same effect is obtained. Furthermore, FIG.
The adjustment pattern film 7 is formed on the incident surface 5a as in the example shown in FIG.
It goes without saying that a surface emitting device with less unevenness in brightness can be realized by adopting a structure using the light guide plate 5 in which the light diffusion portion 8 is formed on the emission surface 5b at the same time or only one of them.

In each of the above examples, the light emitting element 2 and the reflection diffusion layer 3 are mounted on the wiring board 1. However, as shown in FIG. 5, a lead frame is used instead of the wiring board 1. It is possible to increase the heat dissipation and to make it suitable for mass production.

In FIG. 5, a bifurcated lead frame 13 is connected to the power source side of a device incorporating the liquid crystal display panel.
The light emitting element 2 is mounted with the upper surface of the one lead 13a as a mount portion, and the other lead 13b and the light emitting element 2 are bonded by the wire 2a. A reflection frame 14a, a transparent resin layer 14b, and a light guide plate 14c are integrally provided as the reflection diffusion layer 14 on the upper end of the lead frame 13. This reflection diffusion layer 14 has substantially the same structure as that shown in FIG. 1, for example, and the light guide plate 14c is provided with the adjustment pattern film or the light diffusion portion shown in FIG. It is made uniform and is emitted to the illumination target side.

In the example of FIG. 5, the lead frame 13 and the reflection frame 14a are integrally molded, the light emitting element 2 is mounted on the mount portion of the lead 13a, and then the light guide plate 14c is incorporated into the reflection frame 14a. It can be manufactured by a step of injecting a liquid resin that forms the transparent resin layer 14b. By integrally molding the lead frame 13 and the reflection frame 14a in this way, it is more suitable for mass production. Further, since the heat generated when the light emitting element 2 is turned on is released to the device side by the lead frame 13, the reliability of the light emitting element 2 is also improved.

[0045]

According to the present invention, even if only one high-luminance light-emitting element is arranged in the central portion of the light guide plate, only the portion close to the light-emitting element is projected to have high luminance by forming the light distribution portion. In addition, by forming the diffusion portion, it is possible to provide a backlight with less uneven brightness. In addition, since the light from the light emitting element is directly taken into the light guide plate, the utilization efficiency is improved, and the surface brightness is improved by only one light emitting element, which leads to low cost, low power consumption, and downsizing. further,
Mounting the light emitting element on the lead frame improves heat dissipation and improves reliability.

[Brief description of drawings]

FIG. 1 is a schematic view of a surface emitting device of the present invention, (A) is a plan view (B) is a longitudinal cross-sectional view showing an enlarged part

FIG. 2 is a detail of the diffusion part of the light guide plate, (A) is a front view (B) is a longitudinal cross-sectional view showing an enlarged part

FIG. 3 is a bottom view of an example in which the incident surface of the light guide plate is provided with a light distribution plate.

FIG. 4 is a vertical cross-sectional view showing an example in which a light distribution layer is provided on a surface-mounted light emitting element.

FIG. 5 is a longitudinal sectional view showing an example in which a light emitting element is mounted on a lead frame and a reflection diffusion layer is integrated.

FIG. 6 is a schematic view of a conventional example of a backlight structure including a light guide plate, in which (a) is a longitudinal cross-sectional view of a main part and (b) is a right side view of the same (a).

[Explanation of symbols]

1 wiring board 2 light emitting element 2a wire 3 Reflective diffusion layer 4 reflective frame 4a Reflective surface 5 Light guide plate 5a Incident surface 5b exit surface 6 Transparent resin layer 7 Adjustment pattern film 8 Light diffuser 9 Surface mount LED 9a Light distribution layer 10 Light distribution plate 10a light transmission hole 13 lead frame 13a, 13b lead 14 Reflective diffusion layer 14a reflective frame 14b Transparent resin layer 14c Light guide plate

Front page continuation (72) Inventor Yoshihiko Chosa 1-1 Sachimachi Takatsuki, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd. (56) Reference JP-A-10-319873 (JP, A) JP-A-8-153895 (JP, A) JP 9-18055 (JP, A) JP 61-158605 (JP, A) JP 61-158607 (JP, A) JP 60-92678 (JP, A) Kaihei 5-346768 (JP, A) JP 11-284803 (JP, A) JP 2000-31547 (JP, A) Actual opening 4-101592 (JP, U) Actual opening Sho 63-22760 (JP , U) Actual Kaihei 5-55567 (JP, U) Actual Kai Sho-40-4009 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00 G02B 6/00

Claims (2)

(57) [Claims] 1. A light-emitting element mounted on a conductive material, and a reflection-diffusion layer that houses the light-emitting element and reflects and diffuses the emitted light toward an illumination target side. A reflection frame that surrounds at least the periphery and has a reflection surface in the light emission direction formed on the inner surface, and a part or the whole is immersed in the reflection frame with a gap between the light emitting element and the reflection surface, and A light-transmissive light guide plate that takes in light from the light-emitting element and emits surface light toward the illumination target side .
The gap between the reflection surface and the light guide plate is filled and the light is emitted.
And a transparent resin layer which seals around the element, a period from the light emitting element to the illumination target, spaced between 且 one said reflecting surface, the light traveling directly to the illumination target Bei means for equalizing the illumination intensity distribution
For example, a means for equalizing the illumination intensity distribution to the illumination target
Then, on the incident surface of the light guide plate facing the light emitting element,
Light distribution from the light emitting element to the light guide plate
The light distribution part to be incident at and the light guide plate facing the illumination target side.
The light emitted from the light guide plate onto the light emitting surface.
A surface emitting device comprising a diffusing section for diffusing toward the elephant side . 2. The conductive material is a lead frame,
The surface emitting device according to claim 1, wherein the lead frame is integrally formed with a reflective frame of the reflective diffusion layer.