JPH10223021A - Surface light emitting device and display device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge the effective area of a light emitting surface, and prevent the occurrence of nonuniformity of the emitting light by optically connecting a light emitting element in a corner part corresponding to the corner of a light conductive plate by a surface light emitting device composed of the light transmissive light conductive plate and the light emitting element optically connected to an end surface of the light conductive plate. SOLUTION: A light conductive plate 101 is composed of, for example, an acrylic resin, a polycarbonate resin, glass or the like, and efficiently emits the light in a surface shape while diffusing the light emitted from a light emitting element 102. The light emitting element 102 uses an LED chip capable of efficiently emitting light on a surface by being optically connected to the light conductive plate, and a covering rate per unit area is reduced in an intensely light emitting part close from a light source by considering a directional angle of the light emitting element 102, and the covering rate is enhanced as light emitting intensity weakens. A reflecting member 103 is formed by containing a scattering material and a white pigment in resin such as a polyethylene terephthalate resin. By such constitution, uniformity of the light emitting intensity can be improved.

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 switch using a light-emitting element, a surface light-emitting device used for various backlights and displays, and the like. The present invention relates to a planar light emitting device having a large light emitting area.

[0002]

2. Description of the Related Art Today, various portable electronic devices such as portable telephones and notebook personal computers are rapidly developing. Along with this, social demands for a high-brightness display device for displaying and outputting the operation state of electronic devices, image information, and the like are increasing more and more. For example, in a display device using a liquid crystal, an image is displayed by a liquid crystal device and a light source for its backlight so that the display device can be used in an environment with little external light such as at night or indoors. As a planar light emitting device used for such a display device, a small fluorescent tube called a cold cathode tube is often used. The cold-cathode tube is arranged on the end face of the light guide plate and uniformly diffuses white light introduced from the end face into the plane by a diffusion portion provided on the back surface of the light guide plate. Thus, the linear light source is converted into a surface light source and used. As a planar light emitting device using a light guide plate, a device using a cold cathode tube as a light source as a light source has been the mainstream.

On the other hand, as a new light source, RGB (red light,
LED chips, which are semiconductor elements capable of emitting light of high luminance in green and blue colors, respectively, have been developed. LE like this
A planar light-emitting device using a D-chip emits light of a small size with high efficiency and vivid color. In addition, since it is a semiconductor element, there is no fear of lighting failure due to disconnection. It has excellent driving characteristics and is resistant to vibration and ON / OFF lighting.
Further, a boosting circuit and a stabilizing circuit are not required. Therefore, it can be driven by a direct current, and no high-frequency component is generated, and there is no fear of noise. For the above-mentioned reasons and the like, it is expected to be a promising planar light emitting device instead of a planar light emitting device using a cold cathode tube.

In order to emit a white light from a planar light emitting device using a semiconductor element, light emitted from each LED chip such as RGB or BY (blue or yellow) is mixed to form a planar light by a light guide plate or the like. Let it. Alternatively, the light emitted from the LED chip and the light emitted from the fluorescent material excited by the light from the LED chip are mixed to use the complementary color relationship to cause the white light to emit planar light using the light guide plate. You can also.

A planar light emitting device using such an LED chip is macroscopically recognized as a point light source, unlike a linear light source such as a cold cathode tube described above.

Therefore, in order to make a planar light source using a high-brightness LED chip, light is introduced from the side end surface of the light guide plate. In addition, a dot pattern is formed on a light guide plate or the like so as to form a notch or a desired reflection pattern so that uniform light can be emitted in a planar manner even at a greater distance from the light emitting portion of the LED chip. Alternatively, a diffusion lens is provided on the LED chip. By arranging a diffusion member on the light guide plate or the like, more uniform light emission can be considered.

[0007]

However, the light emitting area of the planar light emitting device is increased. Further, in order to perform surface light emission with higher luminance, it is necessary to further improve the light emission luminance from the LED chip. In the case of using an LED chip, it is necessary to convert from a point to a plane when viewed macroscopically. For this reason, although uniform light can be obtained to some extent by a dot pattern or the like, the pattern becomes complicated. In particular, high brightness LE with emission intensity improved to several thousand mcd
When the D chip emits full light, the number of LED chips can be reduced and the size can be reduced. However, a very strong light emission intensity distribution is generated around the vicinity of the light emitting element serving as a light source. Therefore, the dot pattern alone may not be sufficient to make the surface uniform.

As in the case of the dot pattern, unevenness in luminance can be solved to some extent by providing a reflection member, a notch, and a diffusion lens. However, both have a problem that the area of the non-light-emitting portion becomes large and the advantage of improving the brightness of the light source cannot be fully utilized. An object of the present invention is to solve the above problems and provide a planar light emitting device capable of emitting light with high luminance, in which an effective area of a light emitting surface is increased and light emission unevenness is extremely reduced.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a planar light-emitting device having a light-transmitting light guide plate and at least one light-emitting element optically connected to an end face of the light guide plate. In particular, the light emitting element is a planar light emitting device that is optically connected at a corner corresponding to a corner of the light guide plate when viewed from the light emission observation surface side.

[0010] A planar light emitting device according to a second aspect of the present invention relates to a planar light emitting device having a light guide plate having a light transmitting property and at least one light emitting element optically connected to an end face of the light guide plate. . In particular, the light emitting element is optically connected to at least a first side sandwiched between a second side and a third side of the light guide plate, which is narrower than a directional angle of light emitted from the light emitting element when viewed from the light emission observation surface side. Is a planar light emitting device.

According to a third aspect of the present invention, in the planar light emitting device, the light emitting portion of the light emitting element optically connected to the light guide plate includes:
When viewed from the light emission observation surface side, it is substantially symmetrical along the center line of the corner sandwiched by the second side and the third side.

In the planar light emitting device according to a fourth aspect of the present invention, the light emitting element has both a positive electrode and a negative electrode on the same plane side via a gallium nitride compound semiconductor provided on an insulating substrate. The arrangement direction between the two electrodes is substantially parallel to the thickness direction of the light guide plate at the end face.

In the planar light emitting device according to the fifth aspect of the present invention, the light guide plate and the light emitting element are optically connected via a color conversion section containing a fluorescent substance.

The planar light emitting device according to a sixth aspect of the present invention has a color conversion section containing a fluorescent substance on the main surface of the light guide plate.

In the planar light emitting device according to a seventh aspect of the present invention, two or more kinds of light emitting elements emit light having different emission wavelengths.

In a display device according to an eighth aspect of the present invention, there is provided an optical member having a plurality of optical shutters each of which opens and closes in a dot shape, and a planar member provided so that emitted light passes through the optical shutter. A light emitting device. In particular, the planar light-emitting device is optically connected to a light-transmitting light guide plate and an end surface of the light guide plate, and is optically connected to a corner corresponding to a corner of the light guide plate when viewed from the light emission observation surface side. Light emitting element.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The inventor of the present invention
By arranging the light emitting element at a specific position of the light guide plate in consideration of the directivity angle of the light emitted from the light emitting element, it is possible to increase the effective light emitting area and to achieve a planar light emitting device capable of emitting uniform and high brightness light. The inventors have found that the present invention is possible and have accomplished the present invention.

It is considered that the reason why the planarity is improved by the configuration of the present invention is that there is an end face of the light guide plate corresponding to the directional angle of the light emitting element.

That is, as shown in FIGS. 5 and 6, light from the light emitting element has a directional characteristic of emitting light radially with a certain directional angle. Therefore, 1 of the main surface of the light guide plate viewed from the emission observation surface
When it is arranged on the side, there are places where the light emission intensity near the light emitting element is strong and the light emission intensity becomes weaker as the distance from the light emitting element increases. In particular, the vertical direction near the light emitting element tends to be darker than the direction in which light emission is strongest.

In the present invention, since the end faces (second and third sides) of the light guide plate are arranged in the side direction where the light emission intensity is weak due to the directivity angle of the light emitting element, the influence of the directivity characteristics is small and the light emission intensity is small. Improve uniformly. In particular, when a reflection plate is formed on the second and third sides forming the side surface of the light guide plate, reflected light can be used. In addition, since the central portion having high light emission intensity can be arranged on a diagonal line of the light guide plate, light can be efficiently emitted to a distant place. When the position opposite to the light emitting element corresponds to the corner of the light guide plate, the reflected light can be made uniform.

In addition, when the light emitting surface is irradiated with light non-uniformly due to the structure of the light emitting element such that an electrode provided on the semiconductor becomes a shadow of the light emitting surface, the directional characteristics may be distorted. . In such a case, the angle of the connection end face of the light guide plate is changed. Alternatively, a rectangular light guide plate is used. Further, by changing the arrangement angle of the LED chips, more uniform light emission can be obtained.

As a specific example of the present invention, FIG. 2 shows a diagram of the surface light emitting device viewed from the light emission observation surface side. Two corners corresponding to the corners of a light-transmitting light-guiding plate using a quadrangular acrylic resin as viewed from the light emission observation surface are chamfered. As shown in FIG. 3, the chamfered end is interposed between acrylic resin which is a transparent elastic body.
The chip type LED of (A) is arranged. The light emitting surface of the chip type LED is bonded to the end surface of the light guide plate. A barium titanate-containing resin is directly printed and cured on the rear surface of the light guide plate for the purpose of making the light emission more uniform. The printed gradation is a gradation in which the coverage rate per unit area is small at a position close to the light source, and the pattern becomes higher as the distance from the light source increases. Further, a reflecting member is formed except for the chamfered corners and the main surface.

On the main surface of the light guide plate, a color conversion member is provided to obtain white light emission. A cerium-activated YAG-based fluorescent substance ((Y _0.2 Gd _0.8 ) ₃ Al ₅ O ₁₂ : Ce), which emits yellow light when excited by blue light emitted from the LED chip, is scattered by the color conversion member in white. What was contained in the resin together with the material was used. The color conversion member is formed into a sheet shape according to the size of the main surface of the light guide plate.

When power is supplied to the light emitting element of such a planar light emitting device, light from the light emitting element is introduced into the light guide plate via the translucent elastic body and emits light in the main surface shape of the light guide plate. Become. At least a portion of the blue light emitted from the light guide plate excites and emits a fluorescent substance in a color conversion member provided on the light guide plate. Uniform white light emission can be obtained by using mixed color light of the light emitting element and the fluorescent substance. Hereinafter, the constituent members of the present invention will be described in detail.

(Light Guide Plates 101 and 201) The light guide plate 101 used in the present invention is one that efficiently emits planar light while diffusing light emitted from the light emitting element 102, and is excellent in transmittance and heat resistance and uniform. Is required. Further, the shape of the light guide plate can be various shapes such as a rectangle and a polygon as desired. Specific constituent materials of the light guide plate include acrylic resin, polycarbonate resin, glass, and the like. As the thickness of the light guide plate increases, the light use efficiency increases as the thickness of the light guide plate increases.

In order to optically connect the light emitting element to a corner corresponding to a rectangular corner of the light guide plate viewed from the light emission observation surface side, a corner of the light guide plate is cut out and chamfered. Alternatively, it can be formed by integrally molding a chamfered product. A plurality of light emitting elements can be provided as desired. In addition, the light emitting elements can be arranged at all corners of the polygon, or can be arranged at one or more corners as desired. If the light guide plate is square, it goes without saying that the light emitting elements may be connected to all four corners, and the number of LED chips at the corners can be variously selected. As the light emitting element, an LED chip molded with resin or glass may be used, or an LED chip directly in contact with the light guide plate may be used. A device in which a light emitting element in which an LED chip is molded is optically connected can be a planar light emitting device with high yield and high reliability.

On the other hand, a device directly connected to the light guide plate or directly through an electrode can reduce the size and improve the light emission intensity.

Further, the light from the light emitting element can be more scattered by forming irregularities (texture) on the light guide plate surface. Further, by forming irregularities on the light guide plate surface in contact with the diffusion film, it is possible to prevent interference fringes caused by the diffusion film sticking to the light guide plate.

In the present invention, optically connecting the light emitting element and the light guide plate means that light emitted by the light emitting element is directly or indirectly introduced into the light guide plate. Specifically, not only the light emitting element is embedded in the light guide plate, but also the light emitting element is bonded with a light transmitting resin or the like, or the light emission of the light emitting element is guided to the light guide plate using an optical fiber or the like. In addition, the method also includes guiding the light obtained by wavelength-converting the light from the light emitting element with the fluorescent substance to the light guide plate.

In the present invention, the corner corresponding to the corner of the light guide plate means a portion of the light guide plate viewed from the light emission observation surface side such that the light from the light emitting element spreads radially and the darkened portion near the light emitting element is reduced. It is. When a reflection member is provided on the side wall of the light guide plate, light reflected by the reflection member can also be used. Therefore, it is also possible to use a light emitting element having a directional angle smaller than that of a portion (first side) sandwiched between the light guide plate end faces (second and third sides viewed from the light emission observation surface side). Note that a preferable corner portion is a light guide plate end face (a light-emitting observation surface side as viewed from the light-emission observation surface side) which is disposed at an angle smaller than a directional angle at which light from the light-emitting element spreads radially when viewed from the light-emission observation surface side of the planar light emitting device. 2 and the third side) (the first side). Therefore, when the shape of the light guide plate is a polygon, the light guide plate substantially corresponds to a vertex of the light guide plate when viewed from the light emission observation surface side. Further, the light emission observation surface side refers to a main surface side on which light of the light emitting element is emitted via the light guide plate. Such a light guide plate can be formed relatively easily by injection molding.

Note that the directivity angle is an angle at which half of the on-axis luminous intensity of the light emitting element is included in the light from the light emitting element which spreads radially. Therefore, it is equivalent to twice the half value angle.

(Light-Emitting Elements 102 and 202) The light-emitting element 102 used in the present invention uses an LED chip which is optically connected to a light guide plate and can efficiently emit light in a planar manner. Various light-emitting diodes, such as a shell-type light-emitting diode coated with an LED chip or a chip-type LED in which an LED chip is disposed on a support, can be used. Similarly, the LED chip can be used by directly bonding it to the light guide plate. In a shell type light emitting diode or a chip type LED, the directional angle can be set as desired by variously changing the shape of a cup in which an LED chip is arranged or the shape of a mold.

As such a light emitting element, ZnS, ZnSe, S
iC, GaP, GaN, AlN, InN, InGaN,
GaAlN, GaAlAs, AlInGaN, AlIn
A light emitting layer formed of a semiconductor such as GaP is preferably used. As a semiconductor structure, a MIS junction,
Examples thereof include a homostructure having a PIN junction and a PN junction, a heterostructure, and a double heterostructure.
The emission wavelength can be variously selected from ultraviolet to infrared depending on the semiconductor material and the degree of mixed crystal thereof. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed as a thin film in which a quantum effect occurs can be used.

Two or more light emitting elements can be used, or two or more light emitting elements can be used. When two or more types are used, various emission colors can be obtained by mixing the emission colors. The light emitting element is RGB (red, green, blue) or BY
(Blue, yellow) and white light can be emitted by mixing all colors. By variously adjusting the power supplied to the light-emitting elements, or by stopping the supply of power for each light-emitting element, various emission colors can be obtained. Specifically, among the light from the RGB light emitting elements, the supply of power to the light emitting elements capable of emitting B (blue) is stopped by stopping the supply of power.
Mixed light of (red, green) is observed. By stopping the supply of power to the light-emitting elements that can emit BG (blue, green) light, R
A (red) emission color is observed. By adjusting these emission colors, various information can be displayed in the emission colors. Specifically, image information can be displayed by a liquid crystal device provided on the planar light emitting device, and information such as the remaining amount of a battery for driving the planar light emitting device and the liquid crystal device can be notified by switching light emission. . By stopping light emission of the light emitting element as the battery level becomes low,
The usage status can be notified while extending the battery life. For example, each light-emitting element can use a transistor connected to the light-emitting element as a driving driver to change the amount of power or the light-emission time supplied to the light-emitting element and adjust the light-emission amount by a signal applied to the base of the transistor.
That is, various information can be displayed by the base signal of the transistor.

Further, at least a part of the light from the light emitting element can be converted into a color to form a white surface light emitting device. In this case, the LED chip includes a nitride-based compound semiconductor (In _x Ga _Y Al ₁ ) capable of emitting blue light capable of efficiently exciting a fluorescent substance such as a yttrium-aluminum-garnet-based or perylene-based derivative activated with cerium. _-
XYN , 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) is desired.

In the present invention, the emission output of the emission wavelength output from one light emitting element is preferably 200 μW or more, more preferably 300 μW or more. When the light emitting output of the light emitting element is less than 200 μW, even if the number of light emitting elements optically connected to the light guide plate is increased, it tends to be difficult to obtain sufficient brightness and uniform planar light emission.

As a specific example satisfying such characteristics,
A light-emitting element using a nitride-based compound semiconductor is exemplified. When a gallium nitride-based compound semiconductor is used, a material such as sapphire, spinel, SiC, Si, or ZnO can be used for the substrate. In order to form a gallium nitride-based compound semiconductor having better crystallinity, a sapphire substrate is preferably used. A buffer layer such as GaN or AlN is formed on this sapphire substrate, and a pn
A gallium nitride-based compound semiconductor having a junction or the like is formed.

The gallium nitride-based compound semiconductor shows n-type conductivity without doping impurities. When a desired n-type gallium nitride semiconductor is formed, for example, to improve luminous efficiency, Si, Ge, Se, T
It is preferable to appropriately introduce e, C, and the like. On the other hand, when a p-type gallium nitride based semiconductor is formed, p-type dopants such as Zn, Mg, Be, Ca, Sr, and Ba are doped. A gallium nitride-based compound semiconductor is difficult to become p-type only by doping with a p-type dopant. Therefore p
After the introduction of the type dopant, it is preferable to make the p-type by heating in a furnace, low-speed electron beam irradiation, plasma irradiation, or the like.
After the exposed surfaces of the p-type semiconductor and the n-type semiconductor are formed by etching or the like, each electrode having a desired shape can be formed on the semiconductor layer by a sputtering method, a vacuum evaporation method, or the like.

Next, the formed semiconductor wafer or the like is directly full-cut by a dicing saw in which a blade having a diamond blade is rotated, or after a groove having a width wider than the blade width is cut (half cut). The semiconductor wafer is broken by external force. Alternatively, an extremely thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a checkerboard pattern by a scriber in which a diamond needle at the tip reciprocates linearly, and then the wafer is cut by an external force and cut into chips from the semiconductor wafer. Thus, an LED chip that is a gallium nitride-based compound semiconductor can be formed.

In the present invention, more uniform surface light emission can be achieved by using a light emitting element that takes into account the light emitting surface depending on the arrangement and shape of the electrodes. FIGS. 3, 4 and 5 show a specific example. FIGS. 3 and 4 show a light emitting surface of a chip type LED which is a light emitting element. As the support body 301 of the chip type LED, ceramic, a metal substrate, polycarbonate, polyethylene,
An organic resin substrate such as acryl is preferably used. A sapphire substrate of a nitride-based compound semiconductor is die-bonded to the concave portion of the support using an epoxy resin or the like. The external electrode 302 provided on the support and the electrodes of the LED chips 304, 305, 306, and 307 are electrically connected to each other by a gold wire 303 or the like. Such a light emitting surface of the LED chip is not isotropic. Therefore, the directivity varies depending on the arrangement direction of the LED chips.

When the light emitting element emits light as shown in FIG. 3A, the light emitting element may have light emission characteristics as shown by a broken line in FIG. When the shape of the light guide plate is close to a square or the like, the light emitting portion of the light emitting element optically connected to the light guide plate is substantially symmetrical along the center line of the corner formed by the first and second sides. 3 (B)
By arranging them as shown in FIGS. 4C and 4D, light can be emitted more uniformly from the main surface.

When white light is emitted using a monochromatic LED chip in the present invention, the light emission wavelength of the light emitting element is 400 n in consideration of the complementary color relationship with the fluorescent substance, resin deterioration, and the like.
m to 530 nm, preferably 420 nm to 49
0 nm or less is more preferable. In order to further improve the efficiency of the LED chip and the fluorescent substance, it is necessary to use 450 nm
It is more preferably at least 475 nm.

(Diffusion unit) The diffusion unit is suitably used for diffusing light from a light emitting element, which is macroscopically recognized as a point light source, into a uniform plane. Therefore, in the diffusion portion, a pattern in which the coverage per unit area is small in a portion where strong light is emitted close to the light source in consideration of the directivity angle of the light emitting element and the coverage is increased as the light emission intensity decreases is selected. By applying various patterns such as a dot shape, a stripe shape, and a gradation shape, it is possible to relatively easily obtain uniform light. Further, the diffusion part and the reflection member can be used in combination.

The specific diffusion part is a method in which a resin containing titanium oxide, barium titanate or the like is directly printed on the back surface of the light guide plate. A method in which a sheet-like member on which a white substance is printed is attached to the back surface of the light guide plate. Alternatively, there are various methods such as a method in which fine irregularities patterned are provided on the back surface of the light guide plate and light scattering by the irregularities is used. In the present invention, the side surface of the light guide plate is formed according to the directional angle of the light emitting element. Alternatively, the directional angle of the light emitting element is determined according to the side surface of the light guide plate. For this reason, the strong light emission pattern from the light emitting element can be regarded as a fan shape centering on the corner. Therefore, the dot pattern and the like forming the diffusion portion can be arranged relatively easily, and mass productivity and reliability can be improved.

(Reflection members 103, 203, 204) The reflection members are disposed on the rear side and side surfaces of the light guide plate and are preferably used to reflect light from the light emitting elements in the main surface direction without waste. is there. Therefore, it is sufficient that the light from the light emitting element is efficiently reflected into the light guide plate, and the shape and size can be variously selected. It can be used also as a package which is a case-shaped member having a concave portion for holding the light guide plate, or can be processed on the surface of the light guide plate. As a material of such a reflection member, a scattering material such as barium titanate, aluminum oxide, titanium oxide, silicon oxide, calcium phosphate, a white pigment and / or a dye in a resin such as a polyethylene terephthalate resin, a polycarbonate resin, and a polypropylene resin. And the like are preferably included.

Further, a metal film having high reflectivity such as Al, Ag, Cu or the like may be plated on the light guide plate, or may be formed by a sputtering method, a vacuum evaporation method, or the like. Further, the surface of the reflection member may be provided with irregularities for further improving the color mixing, so that the light emitted from the light emitting element is further scattered.
Furthermore, it is also possible to adopt a multilayer structure for improving the reflection and scattering. Examples thereof include a glass nonwoven fabric coated with a metal for improving scattering properties. These reflecting members can be mounted on the light guide plate with an acrylic adhesive, silicone resin, epoxy resin, or the like.

(Color Conversion Unit 706) In the planar light emitting device of the present invention, in addition to the light emitted from the light emitting element being emitted as it is in a plane, the light from the light emitting element is converted into various colors by the color conversion unit. The light may be emitted in a planar manner. As the color conversion section used for such wavelength conversion, a color conversion section containing a fluorescent substance for converting light emitted from the semiconductor light emitting layer to another color is preferably used. Since the fluorescent substance in the color conversion section emits light isotropically, it also has the function of making the light from the light emitting element more uniform.

Therefore, the color conversion member can take various forms. Specifically, the color conversion member may be formed in the support concave opening of the light emitting element on which the LED chip is mounted. Further, the fluorescent material may be contained in a resin and formed in a sheet shape so as to be disposed on the light guide plate. In this case, it can be arranged on the main surface of the light guide plate,
It can also be arranged between the light guide plate and the light emitting element. The color conversion member containing the fluorescent substance, by variously adjusting the ratio and application of the fluorescent substance and the resin, the filling amount,
Any color tone can be used. Further, by selecting the emission wavelength of the light emitting element, an arbitrary color such as a light bulb color can be provided including a white color having a high color temperature.

As a specific color conversion member, a resin containing a fluorescent substance is applied to a sheet-like base film having a light transmittance of 70% or more with respect to light from a light emitting element by a roll coater or the like. Can be formed. As such a base film, translucent,
Preferable examples include a polycarbonate film and a polyester film having high heat resistance. As the base film, in order to further improve the uniformity of light emission, a film coated with fine resin particles of a refractive index or a light-transmitting inorganic fine particle, and a film obtained by embossing the above film are preferably used. A more uniform white display can be obtained by containing a white pigment together with the fluorescent substance.

When a relatively hard inorganic phosphor is applied on the base film, it is preferable to arrange the application surface opposite to the light guide plate. Accordingly, it is possible to prevent the surface of the light guide plate from being damaged when the planar light emitting device is formed.

Specific examples of the fluorescent substance contained in the color conversion member include various substances such as an organic fluorescent substance and an inorganic fluorescent substance that efficiently absorb the emission wavelength of the light emitting element and emit the desired emission wavelength. Can be Examples of the fluorescent substance that efficiently absorbs a high-luminance blue-based emission wavelength from a light-emitting element using a gallium nitride-based compound semiconductor and emits yellow-based light include perylene-based derivatives and cerium-activated yttrium / gadget / aluminum ( Re _1-x Sm _X ) ₃ (A
_{l 1-y Ga y) 5} O 12: Ce phosphor (where, 0 ≦ x <
1, 0 ≦ y ≦ 1, Re is preferably at least one element selected from the group consisting of Y, Gd, and La). In particular, cerium-activated YAG-based fluorescent materials are
It is more preferable to dispose it close to the ED chip because of its high light resistance. (Optical Member 700) The optical member 700 transmits light from the planar light emitting device 705, and displays various information by controlling the transmission. The optical member 700 has a number of optical shutters each of which opens and closes in a dot shape.
Specifically, a liquid crystal device which can be arranged on the light emitting surface of the planar light emitting device 705 is given.

The liquid crystal device is composed of SnO in which liquid crystal 701 is oriented so as to supply power in a dot matrix form.
It is formed so as to be sandwiched between light-transmitting supports 702 such as silicate glass having a transparent electrode 703 such as ₂ . A liquid crystal device or the like in which transistors are formed so that the liquid crystal 701 can be driven in a dot matrix shape is suitably used. Note that a polarizing plate 704 is provided on each of a pair of glass surfaces of the liquid crystal device.

The light from the planar light emitting device 705 has RGB components, and a filter corresponding to RGB is arranged on the optical member 700. Alternatively, full-color display can be achieved by switching the liquid crystal for each of RGB for each pixel. In addition, full-color display can be performed by driving the liquid crystal device while displaying light emission of the planar light emitting device in a time-division manner for each of RGB. Hereinafter, specific examples of the present invention will be described in detail, but it goes without saying that the present invention is not limited thereto.

[0054]

【Example】

(Example 1) An acrylic plate was 35 x 30 m as a light guide plate.
The acrylic plate was cut into a rectangular shape, and a portion corresponding to the short side corner of the acrylic plate was cut out and chamfered. At the corner, a connection end face (first side) of about 4 mm is formed. After all the cut end surfaces of the acrylic plate were polished, irregularities were formed as diffusion portions on the bottom surface of the acrylic plate. Next, a thickness of 0.
A side surface (including the second and third sides) excluding the main surface of the light guide plate and the connection end surface (first side) to which the light emitting element is optically connected is formed of an acrylic resin plate containing titanium oxide at 2 mm.
Were bonded using an acrylic resin.

On the other hand, the light emitting element has an emission peak of 460.
nm In _0.4 Ga _0.6 N semiconductor was used. In the LED chip, a TMG (trimethyl gallium) gas, a TMI (trimethyl indium) gas, a nitrogen gas, and a dopant gas are flowed together with a carrier gas on a cleaned sapphire substrate, and a gallium nitride-based compound semiconductor is formed by MOCVD. Formed. It is formed by switching between SiH ₄ and Cp ₂ Mg as the dopant gas. An In _0.4 Ga _0.6 N active layer was formed between a contact layer of a gallium nitride semiconductor having n-type conductivity and a cladding layer of a gallium nitride semiconductor having p-type conductivity to form a pn junction. (Note that a gallium nitride semiconductor is formed on a sapphire substrate at a low temperature to serve as a buffer layer. The active layer has a thickness of about 3 nm so as to have a quantum effect. The film was annealed at 400 ° C. or higher.) After exposing the surface of the contact layer of each of the p-type and n-type semiconductors by etching, each electrode was formed by sputtering. After drawing the scribe line on the semiconductor wafer thus completed, it is divided by external force and LED
Chips were formed.

A support having an external electrode therein is formed by compression molding using a resin containing silicon oxide in a polycarbonate resin. LE in the opening of the support
The D chip is die-bonded with an epoxy resin. Each electrode of the LED chip and the wiring of the support were wire-bonded with a gold wire to establish electrical continuity. Then LED
For the purpose of protecting the chip, the inside of the concave portion of the support was covered with a translucent epoxy resin, and the chip type LED shown in FIG. 4C was configured as a light emitting element. The light emitting element is shown in FIG.
The directional characteristics shown by the solid line in FIG.

The light emitting surface of the chip type LED was optically adhered to the corner of the light guide plate using an adhesive tape made of a translucent acrylic resin to form the planar light emitting device shown in FIG. Thus, by supplying power to the light emitting element, it is possible to uniformly emit blue light.

Next, as a material of the color conversion member, (Y _0.5 G
_{d 0.5) 3 Al 5 O 12} : Ce fluorescent substance 80 parts by weight, the thriller was mixed well 90 parts by weight of acrylic resin is used. This chiller is applied and cured on an acrylic-based film using a roll coater, and a thickness of 1 mm is applied on the base film.
A 20μ color conversion member was formed. A color conversion member was arranged on the main surface of the light guide plate so that the fluorescent substance and the light guide plate were not in direct contact with each other to form a planar light emitting device capable of emitting white light. When a power supply was connected to the planar light emitting device thus formed, uniform planar white light emission was obtained from the main surface side.

The average chromaticity point, color temperature, and color rendering index of the thus obtained planar light emitting device capable of emitting white light were measured. The chromaticity points (x = 0.303, y =
0.291, color temperature 8085K, Ra (color rendering index) =
87.3, a performance close to that of a three-wavelength fluorescent lamp. Further, in order to measure the uniformity, the luminance was measured at nine points such as a circle 105 in FIG. The measurement was performed at a measurement angle of 20 using BM-7 manufactured by TOPCON. Average brightness is 1
It was 35 cd / m ² .

(Comparative Example 1) As shown in FIG. 8, a chip type LED as a light emitting element was adhered to the short side of a light guide plate, and a portion other than the portion where the chip type LED was optically connected and the main surface were covered with a reflective portion. A planar light emitting device was formed in the same manner as in Example 1 except for the above.

A power source was connected to the planar light emitting device thus obtained in the same manner as in Example 1 to provide a light source for a backlight.
A radially bright light emitting portion having a directivity of about 100 ° was formed near the light emitting element. In the light emitting surface, color unevenness was formed between a bright part and a dark part. Example 1
The luminance at each point similar to the above was measured, and the results are shown in Table 1 together with Example 1. From the results shown in the table, the average luminance of Example 1 was higher than that of Comparative Example 1, and the luminance unevenness at each point was extremely small. Note that the numbers shown in the table indicate the numbers at each measurement point.

Example 2 As a light guide plate, an acrylic plate was cut into a rectangle of 35 × 30 mm, and a portion corresponding to a short side corner of the acrylic plate was cut into two portions (a first corner portion and a second corner portion). Chipped chamfer. A connection end face of about 3 mm (each corresponding to the first side) is formed at the corner. After all the cut end surfaces of the acrylic plate were polished, irregularities were formed as diffusion portions on the bottom surface of the acrylic plate. Next, an acrylic resin plate having a thickness of 0.2 mm and containing titanium oxide as a reflective member is a side surface excluding a main surface of the light guide plate and a connection end surface (first side) to which the light emitting element is optically connected (each side). (Including the second and third sides) using an acrylic resin.

On the other hand, a light emitting element capable of emitting blue light was used at the first corner. The light emitting element is an LED chip in which an InGaN semiconductor is formed as an active layer on a sapphire substrate. A light-emitting element capable of emitting yellow light was used at the second corner. The light-emitting element is formed by forming an active layer on a GaP substrate by using Al.
This is an LED chip on which an InGaP semiconductor is formed.

A support having an external electrode therein is formed by compression molding using a resin containing silicon oxide in a polycarbonate resin. LE in the opening of the support
Each of the D chips is die-bonded with an epoxy resin containing Ag. Each electrode of the LED chip and the wiring of the support were wire-bonded with a gold wire. Thereafter, in order to protect the LED chip, the inside of the concave portion of the support was covered with a translucent epoxy resin, and a chip type LED was configured as a light emitting element.

The light emitting surface of the chip type LED capable of emitting blue light and the LED chip capable of emitting yellow light are optically adhered to the corners of the light guide plate using an adhesive tape formed of a translucent acrylic resin. A light emitting device was formed. Thus, by supplying power to the LED chip capable of emitting blue light, it is possible to relatively uniformly emit surface light of a blue light emission color. In addition, by supplying power to the LED chip that can emit yellow light, it is possible to relatively uniformly emit surface light of a yellow light emission color. Furthermore, L capable of emitting blue light
By supplying power to both the ED chip and the LED chip capable of emitting yellow light, uniform planar white light emission was obtained from the main surface side. By variously controlling the power supplied to the LED chip, it is possible to variously change the emission color emitted from the planar light emitting device.

Example 3 As a light guide plate, an acrylic plate was cut into a rectangle of 35 × 30 mm, and a portion corresponding to a short side corner of the acrylic plate was cut out and chamfered. At the corner, a connection end face (first side) of about 5 mm is formed. After all the cut end surfaces of the acrylic plate were polished, irregularities were formed as diffusion portions on the bottom surface of the acrylic plate. Next, an acrylic resin containing titanium oxide was insert-molded as a reflection member. The molded packaging has openings on the main surface of the light guide plate and the connection end surface (first side) to which the light emitting element is optically connected. The light from the connection end face can be made planar by fitting the acrylic plate into the package.

On the other hand, a light emitting element capable of emitting blue, red and green light was used for the first side. The blue and green light-emitting elements are InGa as an active layer on a sapphire substrate.
This is an LED chip on which an N semiconductor is formed. The composition of In contained in the light emitting layer is changed depending on the light emission color. A light-emitting element that can emit red light has an active layer of A on a GaP substrate.
This is an LED chip on which an InGaP semiconductor is formed.

After each LED chip was placed in the recess of the mount lead, it was electrically connected to the inner lead and the mount lead using a gold wire or Ag paste. Each LED chip was made capable of emitting light by the power supplied to the lead. A multicolor light emitting diode was formed by molding a mount lead and an inner lead on which the LED chip was disposed with epoxy resin.

The multicolor light emitting diode was fitted in a package serving as a first corner. The fitted light emitting diode can be optically connected to the first side of the light guide plate to form a planar light emitting device.

A liquid crystal device was disposed as an optical member on the light emitting surface of the planar light emitting device. By supplying power to each LED chip of the planar light emitting device while making all the liquid crystal devices transmissive, white light can be relatively uniformly emitted from the surface. The liquid crystal device can be driven to obtain a desired full-color display. Further, by variously controlling the power supplied to each LED chip, it is possible to drive the liquid crystal device to display an image and variously change the emission color emitted from the liquid crystal device.

[0071]

As described above, according to the present invention, a light-emitting element is disposed at a specific portion of a light guide plate so as to compensate for a portion having a low luminous intensity in accordance with the directional angle of a light-emitting element which is a point light source. Therefore, a portion having a small local light emission intensity is not formed, so that the uniformity of the light emission intensity can be further improved and the effective light emission area can be increased. In addition, a small-sized planar light-emitting device having high luminance, excellent uniformity, and excellent color mixing properties can be provided. Furthermore, since the light from the light emitting element, which is a point light source, is easily formed uniformly, it is extremely easy to design the layout of the notch (texture) on the light guide plate or the diffusion portion, which is a dot pattern for forming a desired reflection pattern. Can be made.

According to the configuration of the third aspect of the present invention, a planar light emitting device capable of emitting light in a more uniform planar manner can be obtained.

According to the structure of the fourth aspect of the present invention, it is possible to emit light with higher luminance and more evenly in a plane.

According to the structure of the fifth aspect of the present invention, it is possible to emit various colors such as a white color using one kind of light emitting diode.

According to the structure of the sixth aspect of the present invention, it is possible to provide a planar light emitting device in which the color conversion member has no coloring on the light emission observation surface side. In particular, it is possible to further reduce color unevenness or the like in the case where a color conversion member is used by causing the light emitting element to emit surface light with a more uniform directivity characteristic itself.

According to the structure described in claim 7 of the present invention, a planar light emitting device capable of emitting different colors can be obtained.

By adopting the structure described in claim 8 of the present invention, it is possible to provide a display device capable of achieving higher luminance and uniform display.

[0078]

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a planar light emitting device of the present invention.

[0079]

FIG. 2 is a schematic front view showing another planar light emitting device of the present invention.

[0080]

FIG. 3 shows a light emitting surface of a chip type LED used in the planar light emitting device of the present invention, and FIG.
FIG. 3B shows a chip-type LED in which the end surface of the D chip is parallel to the end surface of the support, and FIG. 3B is a diagram in which the diagonal line of the LED chip is parallel to the end surface of the support.

[0081]

FIG. 4 shows a light emitting surface of another chip type LED used in the planar light emitting device of the present invention, and FIG.
This is a chip type LED in which the diagonal line of the LED chip is perpendicular to the end face of the support, and FIG. 4D shows a chip type LED using another LED chip.

[0082]

5 shows the directional characteristics of FIGS. 3 (A) and 4 (C); the solid line shows the directional characteristics of FIG. 4 (C); and the broken line shows the directional characteristics of FIG. 3 (A). .

[0083]

FIG. 6 is a schematic plan view for explaining the operation of the planar light emitting device of the present invention.

[0084]

FIG. 7 is a schematic sectional view of a display device of the present invention.

[0085]

FIG. 8 is a schematic front view of a planar light emitting device shown for comparison with the present invention.

[0086]

[Description of sign]

101, 201: Light guide plate 102, 202: Light emitting element 103, 203 optically connected to the first side of the light guide plate 103, 203: Reflecting member arranged on the side surface of the light guide plate 105: Brightness measuring unit 204 of planar light emitting device 204 Reflecting member arranged on back surface of light guide plate 301 Supporter of chip type LED 302 External electrode disposed in supporter 303 Conductivity Wire 304: Light-emitting part of LED chip 305: Light-emitting part of LED chip arranged so as to emit strong light substantially parallel to the light-emission observation surface of light guide plate 306, 307: Equivalent to light-emission observation surface of light guide plate Light emitting portion of LED chip arranged so as to emit light intensely in parallel 601: first side of light guide plate 602: second side of light guide plate 603: third side of light guide plate 604 ... Luminance from light emitting element Schematic line 700 showing various parts on a light guide plate 700 optical member 701 liquid crystal 702 glass 703 transparent electrode 704 polarizing plate 705 planar light emitting device 706 .. Color conversion member 801: color conversion member arranged on the light guide plate 802: chip type LED optically connected to the light guide plate 803: reflection member 805 arranged on the side surface of the light guide plate ... Luminance measuring unit of planar light emitting device

[Table 1] However, the unit is cd / m ² .

[Procedure amendment]

[Submission date] February 4, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a schematic front view showing a planar light emitting device of the present invention.

FIG. 2 is a schematic front view showing another planar light emitting device of the present invention.

FIG. 3 shows a light emitting surface of a chip type LED used in the planar light emitting device of the present invention. FIG. 3 (A) shows a chip type LE in which an end surface of an LED chip is parallel to an end surface of a support.
D, and FIG. 3B shows a chip type LED in which the diagonal line of the LED chip is parallel to the end surface of the support.

FIG. 4 shows a light emitting surface of another chip type LED used in the planar light emitting device of the present invention, and FIG.
FIG. 4D shows a chip-type LED in which a diagonal line of the chip is perpendicular to the end surface of the support. FIG. 4D shows a chip-type LED using another LED chip.

5 shows the directional characteristics of FIGS. 3 (A) and 4 (C); the solid line is the directional characteristic of FIG. 4 (C);
9A shows the directivity characteristics.

FIG. 6 is a schematic front view of the planar light emitting device shown for comparison with the present invention.

[Description of References] 101, 201: Light guide plate 102, 202: Light emitting element optically connected to the first side of the light guide plate 103, 203: Reflection disposed on the side surface of the light guide plate Member 105: A luminance measuring unit of the planar light emitting device 204: Reflecting member arranged on the back surface of the light guide plate 301: Chip-type LED support 302: External electrode 303 arranged in the support ... conductive wire 304 ... light emitting portion of LED chip 305 ... light emitting portion of LED chip 306, 307 arranged to emit strong light substantially parallel to the light emission observation surface of the light guide plate A light emitting portion of an LED chip arranged to emit light uniformly and intensely substantially parallel to the light emission observation surface 601: a color conversion member arranged on the light guide plate 602: a chip type optically connected to the light guide plate LED 603 Luminance measuring portion of the reflected disposed on a side face of ... the light guide plate member 605 ... planar light emitting device

Claims (8)

[Claims] 1. A light guide plate (101) having a light transmitting property, and the light guide plate
(101) is a planar light emitting device having at least one light emitting element (102) optically connected to an end face, wherein the light emitting element (102) is the light guide plate ( A planar light emitting device characterized by being optically connected at a corner corresponding to the corner of 101). 2. A light guide plate (101) having a light transmitting property, and said light guide plate
(101) is a planar light emitting device having at least one light emitting element (102) optically connected to the end face, wherein the light emitting element (102) is at least the light emitting element ( The second side (602) and the third side (603) of the light guide plate (101), which are narrower than the directivity angle (604) of the light emitted from the light emitting device (102).
A planar light emitting device characterized by being optically connected to a first side (601) sandwiched between the light emitting devices. 3. The light-emitting portion of the light-emitting element (102) optically connected to the light guide plate (101) includes a second side (602) and a third side (603) as viewed from a light emission observation surface side. 3. The planar light emitting device according to claim 2, wherein the surface light emitting device is substantially symmetrical along a center line of a corner sandwiched between the light emitting devices. 4. The light-emitting element (102) has both a positive electrode and a negative electrode on the same plane side with a gallium nitride-based compound semiconductor provided on an insulating substrate. The planar light emitting device according to claim 1, wherein a thickness direction of the light guide plate at the end face is substantially parallel. 5. The planar light emitting device according to claim 1, wherein the light guide plate and the light emitting element are optically connected via a color conversion part containing a fluorescent substance. 6. The planar light emitting device according to claim 1, further comprising a color conversion section containing a fluorescent substance on a main surface of the light guide plate. 7. The planar light emitting device according to claim 1, wherein the light emitting elements are of two or more types that emit different emission wavelengths. 8. A display comprising an optical member (700) having a number of optical shutters each of which opens and closes in a dot shape, and a planar light emitting device (705) provided so that emitted light passes through the optical shutter. The device, wherein the planar light emitting device (705) is a light guide plate having translucency (101)
And a light emitting element (102) optically connected to an end face of the light guide plate (101) and optically connected at a corner corresponding to a corner of the light guide plate (101) when viewed from the light emission observation surface side. A display device, characterized in that: