JP2001036151A - Surface emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface emitting device for backlight use featuring low power consumption, low price and small size, and is moreover capable of high-luminance surface light emission with more uniformity. SOLUTION: This surface light-emitting device comprises a light-emitting element 2, electrically connected to conductive members on a wiring substrate or the like, a reflection frame 4 that encompasses the light-emitting element 2 at least around its periphery and inside of which a reflector plane 4a is formed directed in the light emission direction, a translucent light-guide plate 5 a part or the whole of which is immersed in the reflection frame 4, keeping a distance between itself and the light- emitting element 2 and between itself and the reflection plane 4a, and which receives the light from the light-emitting element 2 and emits the light from a surface, a translucent resin layer 6 that fills the space between the reflection plane 4a and the light- guiding plate 5, and that seals surrounding of the light-emitting element 2, an adjustment pattern film 7 for taking the light from the light-emitting element 2 uniformly toward the light-guiding plate 5 into a incidence plane 5a, from which the light-guiding plate 5 sees the light-emitting element 2, and a light-diffusing member 8 on an emitting plane 5b of the light-guiding plane 5 for further reducing the nonuniformity of the luminance.

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 unit of a view finder of a video camera or the like.

[0002]

2. Description of the Related Art A liquid crystal display having a small size and low power consumption is widely used for a display portion of a cellular phone or the like. This liquid crystal display is arranged so that the liquid crystal panel faces the display surface, and is often provided with a backlight so that characters and images can be seen even in a dark place. In addition, a backlight is usually provided on a full-color liquid crystal display screen provided in a viewfinder of a video camera or another liquid crystal monitor in the same manner.

A liquid crystal display section of a mobile phone is generally a backlight which emits a single color, and rather than increasing the surface luminance of the display surface, the liquid crystal display portion is uniformly provided so that there is no difference in brightness between the entire display surface. It is necessary to emit light. On the other hand, in the case of a full-color liquid crystal display, it is necessary not only to make the brightness of the entire display surface uniform but also to increase the surface luminance. Recently, white light emitting LEDs have been used. And
The light distribution to the liquid crystal panel is basically the same in that a light guide plate is used, and FIG. 6 is a schematic diagram of a typical example of a backlight structure including the light guide plate. (A) is a longitudinal sectional view of a main part, and (b) is a right side view of the same figure (a).

In FIG. 6, a conventional backlight structure has a light guide plate 52 using a transparent acrylic plate disposed above a printed wiring board 51, and the light guide plate 5
2, a liquid crystal display panel 53 in which liquid crystal is sealed is provided, and a surface-mounted light emitting diode (hereinafter, referred to as “LED”) 54 mounted on a printed wiring board 51 is provided as a light source. The light guide plate 52 has an edge surface 52a of approximately 45 ° on the side where the LED 54 is disposed, and the LED 54
From the edge surface 5
2a, a mirror 52b is arranged along the mirror 52b.
The reflected light from is incident. On the surface opposite to the surface where the light guide plate 52 faces the liquid crystal display panel 53, a fine uneven pattern 52c is formed.
The light from D54 is diffused by the concavo-convex pattern 52c to irradiate the entire liquid crystal display panel 53 with uniform brightness. It is to be noted that two LEDs 54 are generally arranged along the right side of the light guide plate 52 as shown in the illustrated example, or more LEDs are used for higher luminance.

[0005]

The LED 54 used as a light source for such a backlight has recently been developed to have higher luminance, and in particular, a white light emitting device using a GaN-based compound semiconductor has been adopted. Was.

However, the higher the brightness of the LED 54, the higher the light distribution at a portion close to the LED 54. For this reason, the display image is divided into a clear portion and a non-clear portion, so that the image tends to be difficult to see. In addition, since light emitted from the LED 54 is indirectly incident on the liquid crystal display panel 53 via the light guide plate 52, the light guide plate 5
The increase in luminance is also impaired by the attenuation of the amount of light during the passage through 2.

As described above, in the surface light emitting device used in the conventional backlight structure, as the LED used as the light source has higher brightness and the number of LEDs decreases, the surface light emission of uniform brightness can be obtained. Absent. In addition, the light guide plate intervenes to indirectly emit light, and there is much light leakage from the light guide plate, and light cannot be efficiently incident on the light guide plate. Unless used, high brightness cannot be achieved. In addition, since a large number of LEDs are used, there arises a problem that the structure is expensive, the power consumption is high, and the structure is complicated.

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

[0009]

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

[0010]

The invention according to claim 1 comprises a light-emitting element mounted on a conductive material, and a reflection-diffusion layer that houses the light-emitting element and reflects and diffuses light emitted from the light-emitting element toward an object to be illuminated. The reflection / diffusion layer surrounds at least the periphery of the light emitting element, and has a reflection surface formed on the inner surface with a reflection surface for light emission in all directions, and the reflection frame at an interval between the light emitting element and the reflection surface. And a light-transmitting light guide plate that is partially or wholly immersed in the light-emitting device and emits light from the light-emitting element and emits surface light toward the illumination target side, provided between the light-emitting element and the illumination target. A surface light emitting device comprising means for equalizing the distribution of the amount of irradiation light to the illumination target, wherein the light emitting element is arranged so as to correspond to the central portion of the light guide plate. A means to make the distribution of irradiation light amount to the target uniform Uniformly light is incident on the light guide plate I,
Uniform luminance can be obtained toward the illumination target side without locally increasing the luminance only in the light emitting element portion.

According to a second aspect of the present invention, as means for uniformizing the distribution of the amount of light applied to the illumination target, the light from the light emitting element is applied to an incident surface where the light guide plate faces the light emitting element. 2. The surface light emitting device according to claim 1, further comprising a light distribution unit for entering the light guide plate with a uniform light distribution, wherein the light is uniformly distributed on the light guide plate by the light distribution unit. Makes it possible to obtain uniform luminance toward the illumination target side.

According to a third aspect of the present invention, the light guide plate is emitted from the light guide plate to an emission surface facing the illumination target side, as means for uniformizing an irradiation light amount distribution on the illumination target. 3. The surface light emitting device according to claim 2, further comprising a diffusion unit that diffuses light toward the illumination target side, wherein the light is diffused by the diffusion unit to form a uniform light toward the illumination target side. Brightness is obtained.

According to a fourth aspect of the present invention, the light emitting element is a surface mount type light emitting element, and the light from the light emitting element is used as a means for equalizing the distribution of the irradiation light amount to the illumination target. The surface light emitting device according to claim 1 or 3, wherein a light distribution unit for entering the light guide plate with a uniform light distribution is formed on a transparent resin of the surface mount type light emitting element. By uniformly entering the light distributed on the light guide plate by the light distribution unit, uniform brightness can be obtained toward the illumination target side.

According to a fifth aspect of the present invention, there is provided a transparent resin layer filled in a gap between the reflection surface and the light guide plate and sealing around the light emitting element. Item 5. The surface light emitting device according to any one of Items 4, wherein the light extraction efficiency is increased by the transparent resin layer, so that the light utilization efficiency from the light emitting element can be improved.

According to a sixth aspect of the present invention, the conductive material is a lead frame, and the reflection frame of the reflection diffusion layer is formed integrally with the lead frame. A surface light emitting device according to any of the above, wherein heat generated by the light emitting element can be released from the lead frame.

An embodiment 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.
FIG. 2A is a plan view, and FIG.

As shown in FIG. 1, a surface light emitting device according to the present invention comprises a wiring board 1 having a rectangular planar shape, a light emitting element 2 conductively mounted at the center of the wiring board 1, and a And a reflection diffusion layer 3 for surface emission formed on the wiring substrate 1 of FIG. As shown in FIG. 6 of the related art, a liquid crystal display panel, a diffusion sheet, and a prism sheet (not shown) are disposed on the upper end of the surface light emitting device, that is, on the reflection diffusion layer 3. Is incident on this liquid crystal display panel as a backlight.

The wiring board 1 is provided with a wiring pattern (not shown) that is connected to a power supply circuit on the device side when incorporated in a device such as a viewfinder of a video camera. Let it.

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

The reflection frame 4 is a component formed in advance by a resin, placed on the wiring board 1 and fixed with an adhesive, thermal caulking or the like. The resin material of the reflection frame 4 is, for example, a white material such as PBT or PC.
Surfaces are inclined, and these inclined surfaces are reflection surfaces 4 a for light from the side surfaces of the light emitting element 2. The base end of the reflecting surface 4a is located at a position where it does not interfere with the light emitting element 2, and its inclination angle is about 45 °. The light from the light emitting element 2 is reflected right above so that the light from the surface light emitting device is uniform. To be emitted.

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

The transparent resin layer 6 is made of a resin such as an epoxy resin or a silicone resin. The transparent resin layer 6 seals the periphery of the light emitting element 2 as described above. The light guide plate 5 is integrated with the reflection frame 4 so as to have substantially the same height.

Here, when the light emitting element 2 is energized from the wiring board 1, light is emitted from the active layer of the light emitting element 2. In the present invention, the light emitting element 2 has the highest upward light emission luminance in FIG. 1B, that is, has the upper surface of the light emitting element 2 as a 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 traveling toward the incident surface 5a of the light guide plate 5 is the largest, but light from the active layer is emitted not only to the upper surface but also to the side. Therefore, most of the light that has passed through the transparent resin layer 6 in a substantially horizontal direction is reflected by the reflection surface 4a of the reflection frame 4.
And is directed toward the light guide plate 5.

As described above, the light from the light emitting element 2 is divided into a component that is directly incident on the light guide plate 5 from the incident surface 5a and a component that is incident after being reflected by the reflective surface 4a toward the side. . Therefore, if the components directly incident on the incident surface 5a of the light guide plate 5 from the light emitting element 2 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 can be adjusted. The whole can be set to almost uniform brightness. In order to adjust such luminance, FIG.
As shown in FIG. 7, an adjustment pattern film 7 is formed on the incident surface 5a of the light guide plate 5 by, for example, silk screen printing.

As is widely known, silk screen printing is a method of printing by drawing ink on a plate with a squeegee and printing the ink. By changing the distance between the plate and the squeegee or repeating the printing several times, By printing, the thickness of the ink can be freely changed. Then, an adjustment pattern with a uniform thickness using white ink may be used.However, if printing is performed so that the ink layer has a thin portion and a thick portion as needed, light is emitted in a portion where the ink layer is thin. A pattern that blocks light is obtained in a thick part that transmits and is thick. Therefore, the form of the light transmission 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 components of the light reflected from the reflection surface 4a. .

The same effect can be obtained even if the base material having a size of about 2.5 mmφ is formed by attaching a white film made of PET or the like instead of forming the adjustment pattern film 7 by silk screen printing. can get.

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

FIG. 2 is a plan view and an enlarged longitudinal sectional view showing a pattern of an example of the light diffusing section 8.

For example, the light diffusing portion 8 is an uneven portion formed by subjecting a mold to graining or blasting. The uneven portion may be uniform, but the uneven portion is formed deeper in a region closer to the light emitting element, and the pitch of the unevenness is reduced. As the distance from the light emitting device 2 increases, the uneven portion gradually becomes shallower and the pitch becomes smaller. It is formed to be large. In other words, by making the emission surface of the light guide plate 5 rougher in a region closer to the light emitting element and reducing the amount of emitted light, more uniform illumination can be achieved as a whole.

As described above, the adjustment pattern film 7
By making the light from the light emitting element 2 uniform and enter the light guide plate 5 and diffusing the light emitted from the light guide plate 5 by the light diffusing unit 8, a surface light emitting device with less luminance unevenness can be realized.

In the above configuration, when the light emitting element 2 is energized through the wiring board 1, the light is turned on, and 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, only the central portion of the light guide plate 5 directly above the light emitting element 2 and has high brightness as described above. Instead, the light enters the light guide plate 5 as a uniform light amount distribution throughout the light guide plate 5. Light emitted from the side surface of the light emitting element 2 is
The light is reflected toward the light guide plate 5 by the reflection surface 4a of the reflection frame 4,
Most of the light enters the light guide plate 5 from four inclined side surfaces. The light diffuser 8 further improves the uniformity of the luminance of the entire surface light emitting device.

Therefore, if the liquid crystal display panel, the diffusion sheet, and the prism sheet are arranged on the surface light emitting device, it is possible to display a high-brightness liquid crystal image with little luminance unevenness.

Here, in the example shown in FIG. 1, the structure in which the adjustment pattern film 7 is formed on the incident surface 5a of the light guide plate 5 and the light diffusing portion 8 is formed on the emission surface 5b at the same time has been described. By forming only the light diffusion portion 7 or only the light diffusion portion 8, the luminance unevenness of the entire surface light emitting device can be made 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 can be moved from the light emitting surface 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. For this reason, the attenuation of the light emission intensity of the light from the light emitting element 2 is small, and the light extraction efficiency can be increased.
Here, the transparent resin layer 6 is formed in order to realize a high-luminance surface light emitting device. However, in the case of using the ultra-high-luminance light-emitting element 2 or the like, it is not necessary to form the transparent resin layer. Adjustment pattern film 7 so that the entire brightness becomes uniform
May be formed.

Further, since the light-emitting element 2 is arranged corresponding to the center of the light guide plate 5, the light source becomes a light source having the center of the display screen of the liquid crystal display panel as a nucleus. Light capturing efficiency is better than when 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 low, and a plurality of light emitting elements are required to realize a high-luminance surface light 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 substrate 1 and is sealed with the transparent resin, the light use loss is small and the adjustment pattern film 7 is used. By adjusting the light distribution and improving the uniformity by the light diffusing unit 8, the overall luminance can be set uniformly, so that display with less luminance unevenness is possible.

As described above, the adjustment pattern film 7 is formed on the incident surface 5a.
To form one LE.
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. Then, as is generally known as a structure of a liquid crystal display panel, a diffusion sheet and a prism sheet are provided on the surface light emitting device to irradiate the liquid crystal display panel, thereby achieving low cost, low power consumption and small size. Thus, display with less luminance unevenness becomes possible.

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. FIG.

In FIG. 3, a light distribution plate 10 utilizing a metal or the like is integrally adhered or deposited on the incident surface 5a. The light distribution plate 10 has a light transmission hole 10a which is distributed in the central portion and has a small opening diameter and an opening diameter increases toward the periphery. With such a distribution of the light transmitting holes 10a having different opening diameters, the amount of transmitted light is small in the central portion located directly above the light emitting element 2 and is large in the peripheral portion. Therefore, as in the case of the adjustment pattern film 7 of FIG. 1, the luminance unevenness of the surface emitting device can be sufficiently improved.

FIG. 4 shows an example of a light emitting device generally called a surface mount type LED 9 having a structure in which a pair of electrodes are formed on the front and back surfaces of the wiring board itself, and the light emitting device conducting to these electrodes is sealed with a resin package. It is a longitudinal cross-sectional view which shows the example which equips the upper resin package with the light distribution layer 9a.

The light distribution layer 9a is formed on the surface mount type LED 9 by the silk screen printing as described above, so that when the adjustment pattern film 7 is formed on the incident surface 5a of the light guide plate 5 in FIG. The same effect is obtained. Further, FIG.
As shown in the example shown in FIG.
It is needless to say that a surface light emitting device with less luminance unevenness can be realized by adopting a structure using the light guide plate 5 in which the light diffusing portion 8 is formed on the emission surface 5b simultaneously 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, but a lead frame is used instead of the wiring board 1 as shown in FIG. A configuration suitable for mass productivity as well as enhancing heat dissipation can be obtained.

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

In the example of FIG. 5, after the light emitting element 2 is mounted on the mounting portion of the lead 13a, the light guide plate 14c is assembled into the reflection frame 14a by integrally molding the lead frame 13 and the reflection frame 14a. It can be manufactured by a step of injecting a liquid resin for forming the transparent resin layer 14b. By thus integrally molding the lead frame 13 and the reflection frame 14a, it is more suitable for mass production. Further, heat generated when the light emitting element 2 is turned on is released to the device side by the lead frame 13, so that 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 center of the light guide plate, only the portion close to the light-emitting element protrudes by forming the light-distribution portion to achieve high luminance. In addition, by forming the diffusion portion, a backlight with less luminance unevenness can be provided. Further, since the light from the light emitting element is directly taken into the light guide plate as light, the utilization efficiency is improved, and the surface luminance is improved by only one light emitting element, which leads to low price, low power consumption, and downsizing. further,
By mounting the light emitting element on the lead frame, heat radiation is improved and reliability is improved.

[Brief description of the drawings]

1A and 1B are schematic views of a surface light emitting device of the present invention, wherein FIG. 1A is a plan view and FIG.

FIGS. 2A and 2B are details of a diffusion portion of the light guide plate, wherein FIG. 2A is a front view and FIG.

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

FIG. 4 is a longitudinal sectional view showing an example in which a light distribution layer is provided on a surface mount type 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.

6A and 6B are schematic diagrams of a conventional example of a backlight structure including a light guide plate, wherein FIG. 6A is a longitudinal sectional view of a main part, and FIG. 6B is a right side view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wiring board 2 Light emitting element 2a Wire 3 Reflection diffusion layer 4 Reflection frame 4a Reflection surface 5 Light guide plate 5a Incident surface 5b Emission surface 6 Transparent resin layer 7 Adjustment pattern film 8 Light diffusion unit 9 Surface mount type LED 9a Light distribution layer 10 Distribution Optical plate 10a Light transmitting hole 13 Lead frame 13a, 13b Lead 14 Reflective diffusion layer 14a Reflective frame 14b Transparent resin layer 14c Light guide plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Yamanaka, Inventor 1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. (72) Inventor Yoshihiko Chosa 1-1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics F term (reference) 2H038 AA55 BA06 5F041 CA12 DA20 DA43 EE23 EE25 FF16

Claims (6)

[Claims] 1. A light-emitting element mounted on a conductive material, and a reflection-diffusion layer that accommodates the light-emitting element and reflects and diffuses light emitted from the light-emitting element toward an object to be illuminated. A reflection frame surrounding at least the periphery and having 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 at an interval between the light emitting element and the reflection surface, and A light-transmitting light guide plate that receives light from the light emitting element and emits surface light toward the illumination target side, and adjusts an irradiation light amount distribution to the illumination target provided between the light emitting element and the illumination target. A surface light-emitting device, comprising: 2. As means for equalizing the distribution of the amount of light applied to the illumination target, light from the light emitting element is directed toward the light guide plate on an incident surface of the light guide plate facing the light emitting element. 2. The surface light emitting device according to claim 1, further comprising a light distribution unit for entering the light with a uniform light distribution. 3. As means for equalizing the distribution of the amount of light applied to the illumination target, light emitted from the light guide plate is applied to an emission surface of the light guide plate facing the illumination target side. 3. The surface light emitting device according to claim 2, further comprising a diffusing unit for diffusing light toward the light emitting device. 4. The light emitting device is a surface-mount type light emitting device as a means for equalizing the distribution of the amount of light applied to the illumination target, and directs light from the light emitting device toward the light guide plate. The surface light emitting device according to claim 1 or 3, wherein a light distribution part to be incident with a uniform light distribution is formed on a transparent resin of the surface mount type light emitting element. 5. The light-emitting device according to claim 1, further comprising a transparent resin layer that fills a gap between the reflection surface and the light guide plate and seals around the light emitting element. Surface emitting device. 6. The conductive material is a lead frame,
The surface light emitting device according to any one of claims 1 to 5, wherein a reflection frame of the reflection diffusion layer is formed integrally with the lead frame.