JP2002049326A - Plane light source and display element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive and practicable plane light source of collimating light. SOLUTION: This plane light source has plural light emitting elements 2 (LED chips) which are scattered on a plane and optical elements 4 (microlens arrays) arranged in correspondence to the exit light of these light emitting elements and is so constituted that the light transmitted through the optical elements is emitted approximately perpendicularly (as collimating light) to the plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat light source that emits collimated light using an LED or the like, and a flat and thin display device using the same.

[0002]

2. Description of the Related Art A conventional LCD (liquid crystal display element) performs display utilizing an electro-optic effect due to the orientation of liquid crystal molecules. Therefore, as shown in FIG. When the diffused light 102 enters the liquid crystal panel 101 from 100, the light transmitted through the liquid crystal layer 101 has a drawback that the viewing characteristics depend on the display characteristics due to the incident angle dependence of the optical characteristics.

As a solution to this, recently, a method has been proposed in which each pixel of a liquid crystal panel is provided with a region having a plurality of optical characteristics, and differences in optical characteristics depending on viewing angles are averaged to compensate for viewing angle dependence. (Such as multi-domain orientation).
In addition, there is a liquid crystal switching method (such as an IPS method) that uses only horizontal alignment with little dependence on viewing angle. Further, there is a method in which a film for optically compensating the viewing angle dependence of the optical characteristics of the liquid crystal is laminated on the liquid crystal panel.

[0004] However, all of the above methods involve an increase in cost due to an increase in the number of steps and members. In each case, the visibility is more effective than the conventional liquid crystal element, but the optical compensation for the viewing angle is not perfect. For example, the contrast of a front image and the contrast when viewed obliquely The viewing angle dependency is a problem particularly for large computer monitors and TV applications.

On the other hand, in a fluorescent light emitting type display element such as a CRT, the emitted light of the phosphor is scattered light, and the display light is almost completely scattered light, so that there is almost no dependence on the viewing angle. In order to obtain characteristics equivalent to the viewing angle characteristics of these fluorescent display devices, the following methods have been considered for liquid crystal panels. As shown in the conventional diagram of FIG. 29, first, the emission light 104 of the backlight light source (backlight unit) 103 is substantially collimated light (the emission light of the backlight is substantially perpendicular to the surface). A light diffusion layer or film 105 for diffusing light is provided on the front surface (display side) of the liquid crystal panel 101. At this time, in order to prevent crosstalk between pixels, it is preferable to provide a light diffusion layer in the display side substrate (not shown) of the liquid crystal panel 101.

The light diffusion layer or film 105 is preferably a forward diffusion type layer or film which has a large amount of light diffused forward and a small amount of light diffused backward in order to improve the contrast in a bright room. In this method, the liquid crystal layer 101
Since the light is incident perpendicularly, the optical characteristics of the light transmitted through the liquid crystal layer 101 are substantially the same. Further, since the light diffusion layer or the film 105 diffuses the transmitted light to the display side, the optical characteristics of the diffused light do not change, and a display independent of the viewing angle can be obtained. A method of obtaining such collimated emitted light is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-189907 or
505412. Further, a phosphor may be provided instead of the light diffusion layer. In this case, for example, the backlight light source is an ultraviolet light source, and the ultraviolet light is modulated by a light modulation element such as a liquid crystal element, and the transmitted light excites the phosphor to emit scattered light. Due to the scattered light emission, there is no viewing angle dependency of the display image quality like the CRT.

A flat light source that emits such substantially collimated light is provided by a light modulating means other than the LCD, for example, a light modulating means for moving a flexible thin film by electrostatic force to change the light transmittance. The present invention is also effective for a device in which the transmittance of ultraviolet light incident from an ultraviolet light source is changed and the transmitted light is made incident on a phosphor in front of the light source to display light. In particular, if the type of the light modulating means is interference, diffraction, or the like, which depends on the incident angle of light, it is possible to eliminate the dependence on the incident angle.

Further, the present invention is effective not only for the use of such a display element but also as a general-purpose flat light source. For example, when it is desired to make the light from the flat light source reach farther, it is necessary to have directivity. In this case, however, a flat light source capable of emitting substantially collimated light is useful.

[0009]

However, in the above conventional example, at present, it is technically difficult to provide a backlight light source that emits substantially collimated light with high efficiency.
Fluorescent lamps are currently the mainstream of light sources, but fluorescent lamps that match the spectral transmission characteristics of color filters for backlighting need to be surface light sources because they are elongated tube-shaped linear light sources. Since the light source is a planar light source through the light guide plate and the diffusion plate, the emitted light of the planar light source is non-polarized light having a random optical path. To collimate the light, the optical system becomes complicated and the light use efficiency decreases. There was a problem. In this case, it is possible to use a surface emitting laser as a planar light source. However, when a large-area display element is formed, there is a problem that the cost is considerably high and the apparatus is not suitable.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flat light source capable of emitting collimated light with high efficiency with a simple structure, and a display device using the same.

[0011]

In order to achieve the above object, the invention according to claim 1 is directed to a plurality of light emitting elements scattered on a plane and an optical element arranged corresponding to the light emitted from the light emitting elements. And light transmitted through the optical element is emitted substantially perpendicular to the plane. According to this configuration, for example, a plurality of light-emitting elements such as LED chips are two-dimensionally arranged as a point light source, and the light emitted from the light-emitting elements is combined with an optical element such as a microlens. A planar light source that passes through an optical element and is collimated and emitted perpendicular to a surface can be configured. According to a second aspect of the present invention, there is provided the flat light source according to the first aspect, and means for directing an incident side to the outgoing light side of the flat light source to deflect incident light from the flat light source substantially vertically. It is characterized by. According to this configuration, the collimated light incident from the flat light source can be deflected in the vertical direction by a deflecting unit such as a half mirror, and can be extended as a surface light source.

According to a third aspect of the present invention, there is provided a flat light source according to the first aspect or the flat light source device according to the second aspect, a light modulation element, and a diffusing means. According to this configuration, it is possible to change the light transmittance of the collimated light from the flat light source by the light modulating means, emit the light as diffused light from the diffusing means, and to perform display with reduced viewing angle dependence. According to a fourth aspect of the present invention, in the display device of the third aspect, so-called field sequential driving is performed. This is a display driving method in which colors emitted from a planar light source are switched in a time sequential manner within one field period, and a light modulation element is driven in synchronization with the emitted colors. According to this configuration, for example, R
Three independent color lights from light emitting elements such as LED chips of three colors of GB can be added and mixed in a time-division manner, and color display is possible without a phosphor or a color filter, thereby improving light use efficiency and resolution. I do. Further, at the same resolution, the number of display dots and the driving IC can be reduced, and the cost is reduced.
According to a fifth aspect of the present invention, there is provided the flat light source according to the first aspect, a light modulation element, and a phosphor. According to this configuration, the collimated light from the flat light source is light-modulated to excite the fluorescent material, and display independent of the viewing angle can be performed.

Further, the invention according to claim 6 is characterized in that the optical element is a microlens array. According to this configuration, the incident light from the light emitting elements as the point light sources can be emitted as the collimated light by the micro lenses corresponding to the light emitting elements. The invention according to claim 7 is characterized in that the optical element is a mirror lens array. According to this configuration, the incident light from the light emitting elements serving as the point light sources can be emitted as the collimated light by the many mirror lenses corresponding to the light emitting elements. Further, the invention according to claim 8 is characterized in that the light emitting element is made of a plurality of independent colors. According to this configuration, it is possible to independently control each color, and it is possible to perform free color display and the above-described field sequential driving.

[0014] The invention according to claim 9 is characterized in that the light emitting element is an LED. According to this configuration, the LED can be arranged as a semiconductor chip and can be regarded as a point light source, and can be easily converted into collimated light by a lens or the like. Further, light can be emitted from UV light to RGB light, which is three primary colors of visible light, and free color display is possible. Further, the LED can blink at a high speed, and is suitable for the above-described field sequential driving. Further, the invention according to claim 10 is characterized in that the light emitting element is an organic or inorganic EL. According to this configuration, a dispersion-type or thin-film-type inorganic EL (electroluminescence) and a low- and high-molecular-weight organic EL can be formed as a large number of point light sources arranged in a plane and converted into collimated light by a lens or the like. Is easy. This formation can be mass-produced in a large area by printing, photolithography, or a mask film formation method in vacuum film formation. Further, light can be emitted from UV light to RGB light, which is three primary colors of visible light, and free color display is possible. It is possible to blink at a higher speed, and is suitable for the above-described field sequential driving. An eleventh aspect of the present invention is characterized in that the light emitting element is an FED. According to this configuration, if an FED (Field Emission Display) of a type that irradiates electrons to the phosphor at an accelerated rate is formed as a large number of point light sources arranged in a plane, it can be easily converted into collimated light by a lens or the like. . This formation can be mass-produced in a large area by printing or photolithography. In addition, by selecting a phosphor, it is possible to emit light from UV light to RGB light, which is three primary colors of visible light, and a free color display is possible. It is possible to blink at a higher speed, and is suitable for the above-described field sequential driving.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of the flat light source according to the first embodiment of the present invention. FIG. 2 shows FIG.
FIG. 2 is a front sectional view of the flat light source shown in FIG. FIG. 3 is a cross-sectional view of a planar light source in which the microlenses shown in FIG. 2 are spherical lenses. FIG. 4 is a diagram showing an example in which the microlenses of FIG. 2 are configured by a mirror lens array. FIG. 5 shows the LED shown in FIG.
FIG. 3 is a diagram showing a structure and wiring of a chip. 6 is a configuration diagram of a plurality of LEDs by a chip vertical type hybrid, FIG. 7 is a configuration diagram of a plurality of LEDs by a chip horizontal type hybrid, and FIG. 8 is a configuration diagram of a plurality of LEDs by monolithic formation. It is. In FIG. 1, reference numeral 1 denotes a flat light source that emits collimated LED light, and the flat light source 1 includes a large number of LED chips 2 formed on a rear substrate 3.
And a microlens array 4 formed on the front substrate 5 and collimating the incident light from the LED chip 2.

In FIG. 5, the LED chip 2 formed on the back substrate 3 is composed of a p-type semiconductor connected to the anode electrode 2a by wire bonding 2c, and an n-type semiconductor connected to the cathode electrode 2b. LED light is emitted from the p-type semiconductor side. In FIG. 6, a cathode common electrode pattern CC and an anode common electrode AC made of a metal film are simultaneously formed on an insulating substrate I such as glass or resin. On this, a cathode electrode C, an n-type semiconductor n,
A plurality (nine in the figure) of LED chips composed of a p-type semiconductor p and an anode electrode A are mounted at predetermined positions. At this time, the cathode electrode C is connected to the cathode common electrode pattern CC.
The LED chip is mounted so as to be connected to the LED chip. Thereafter, the anode electrode A of each LED chip and the anode common electrode AC are connected by wire W by wire bonding. When a current is applied to the cathode common electrode pattern CC and the anode common electrode pattern AC, a plurality of (9) LED chips emit light at the same time.

Also, the LED chip 2 is not in the vertical p / n configuration as shown in FIG. 5 (FIG. 6).
If the anode and the cathode are formed at the positions on both sides of the chip between the chip 2 and the substrate 3,
The wire bonding 2c can be omitted and the size can be reduced. FIG. 7 shows this example. In FIG. 7, glass,
A cathode common electrode pattern CC and an anode common electrode AC made of a metal film are simultaneously formed on an insulating substrate I such as a resin. Between these two electrode patterns, a plurality of (nine in the figure) LED chips composed of a cathode electrode C, an n-type semiconductor n, a p-type semiconductor p, and an anode electrode A are mounted at predetermined positions. At this time, each LED chip is mounted such that the LED chip is turned sideways and the cathode electrode C faces the cathode common electrode pattern CC. LED chip cathode electrode C and cathode common electrode pattern CC, and LED
Chip anode electrode A and anode common electrode pattern A
C is connected by a conductive paste. The anode electrode A of each LED chip is connected to the anode common electrode AC.
When a current is applied to the cathode common electrode pattern CC and the anode common electrode pattern AC, a plurality of (9) LED chips emit light at the same time. When a smaller planar light source is desired, monolithic formation on a semiconductor substrate or an insulating substrate is possible. FIG. 8 shows this example.
In FIG. 8, a diffusion mask layer I made of an insulating layer is patterned on n on an n-type semiconductor substrate. Since the opening of the diffusion mask layer becomes a light emitting portion, patterning is performed at a desired position. Next, a p-type semiconductor P is formed by diffusing impurities. At this time, a p-type semiconductor is formed only in the diffusion mask opening.
Next, an anode common electrode A made of metal is formed by patterning. Finally, a cathode common electrode CC is formed on the back surface of the substrate. When a current is applied to the cathode common electrode CC and the anode common electrode pattern AC, each light emitting unit emits light simultaneously. According to this configuration, the manufacturing process can be shortened, and a high-density point light source can be formed. In this example, a diffusion method is used for forming a pn semiconductor, but a pn semiconductor may be formed by epitaxially growing a semiconductor layer on a semiconductor substrate or an insulating substrate. Furthermore, COB (Chip On B)
(order), more integration is possible. In the above-described configuration example of the LED array, the cathode common electrode C is used in order to make the emission intensity of each LED chip or LED light emitting unit uniform.
A resistance layer may be provided between C and the anode common electrode AC and the LED. Further, the cathode common electrode pattern CC and the anode common electrode pattern AC are not limited to the above-described example, and may be matrix wiring or the like. Furthermore, a reflector may be formed around the light emitting portion of the LED in order to increase the luminous efficiency in the emission direction. In addition, a reflector and a light shield for shielding unnecessary emitted light may be formed around the LED. In addition, various configurations and formation methods are possible without being limited to the previous example.

Next, the operation will be described. Such L
When configuring the light source using the ED chip 2, first, when the LED chip 2 illustrated in FIG. 1 is configured with three colors of RGB, a white backlight of a fluorescent lamp conventionally used for an LCD display element, a flexible thin film display element, and the like. Can be configured as a white light source.
Also, a blue LED chip + fluorescent pigment or fluorescent dye (G, R
The white light source can also be configured by the configuration of (fluorescence). That is, if green and red fluorescent paints are applied on the blue LED chip and the blue LED chip emits light and transmits,
G + R yellow is mixed with blue to produce white light. Alternatively, white light can be emitted by a blue LED chip and a phosphor (only B → Y fluorescence such as YAG). The blue LED chip is based on GaN, ZnSe, SiC or the like.

As the backlight light, LED light of any wavelength other than white light can be used. For example, a UV-excited phosphor is irradiated and excited using light emitted from a GaN-based LED chip having a wavelength of 360 to 400 nm instead of an ultraviolet backlight using a low-pressure mercury lamp.

As shown in FIG. 2, if such an LED chip 2 is arranged on a back substrate 3 and covered with a microlens array 4, the light emitted from the LED chip 2 is refracted and deflected in the microlens according to the refractive index. The collimated light 6 becomes an LCD shutter (not shown) at the next stage,
Alternatively, the light enters a flexible thin film light modulation element or the like. The material of the microlens array 4 is a transparent solid polymer material or the like, and is a spherical or aspheric lens having a diameter of about several mm. In this case, the size of the LED chip 2 is 1 mm.
Degrees are possible. Examples of the material of the microlens include glass and resin, and resin is particularly preferable from the viewpoint of mass productivity. As the resin, an acrylic resin, an ethoxy resin, a polyester resin, a polycarbonate resin, a styrene resin, a vinyl chloride resin, or the like is optically preferable. Further, the resin material is a light-curing type, a light-dissolving type, a thermosetting type, or a thermoplastic type. And the like can be selected as appropriate according to the method of manufacturing the microlens.
As a method for producing the microlens, a casting method using a mold, heat press molding, injection molding, a printing method, or a photolithography method is preferable from the viewpoint of productivity. Specifically, it can be molded by hot pressing a thermoplastic resin with a microlens-shaped mold. Further, the mold can be formed by filling a mold with a photocurable resin or a thermosetting resin, curing the resin with light or heat, and removing the resin from the mold. As the photolithography method, exposure to ultraviolet light (or visible light) is performed through a light-shielding mask appropriately patterned on a photo-dissolving resin or a photo-curing resin, and dissolving and developing of exposed portions or dissolving and developing of unexposed portions, respectively, are performed. Formed by A microlens having a desired shape can be obtained from the resin material and the exposure distribution. In addition, depending on the resin material, it is possible to perform a high-moisture bake treatment after development and obtain a microlens of a desired shape by surface tension during thermal softening. In the above-described example, the microlenses are convex lenses, but may be flat microlens arrays having a refractive index distribution. Further, it is possible to form a Fresnel lens or a lens using binary optics. In the case of the present embodiment, the lens diameter is appropriately selected according to the emission aperture size from the LED, but it is preferable that the lens diameter is large so that the emission aperture dimension can be regarded as a point light source. For example, when the LED chip is an LED array by the hybrid method, the emission aperture size is 10 mm in diameter.
If it is about 0 μm to 1 mm, the lens diameter is preferably from several hundred μm to several mm. The array of lens arrays is preferably a honeycomb array to reduce light intensity unevenness. The microlens array having the above structure can be manufactured by any of the above-described manufacturing methods. Above all, from productivity,
Casting by a mold or hot press molding is preferred. Further, in the case of a microlens array by a monolithic method, the diameter of the exit aperture can be up to several μm if the exit aperture size is small, and the lens diameter is about several tens μm or more. The method is preferable, and a photoresist material is suitable as the material. FIG. 3 shows a case where the LED chip 2 is a spherical lens located at the position of the center point of the lens 4a, and FIG.
Are located closer to the circumference than the center, and each has a different radius of curvature and a different refractive index. In any case, it is preferable that the LED chip or the LED light emitting unit is arranged at the main focal position on the optical axis of the microlens. Such LED
By configuring a large number of point light sources of the chip 2, a planar light source corresponding to a display element can be configured.

FIG. 4 is a diagram showing an example in which the microlenses of FIG. 2 are constituted by mirror lens arrays. This is an example in which the LED chip 2 is arranged on the center side of the concave mirror lens array 4b, and the irradiation light is reflected to be collimated light. Actually, as shown in FIG. 9, it can be configured by disposing a transparent substrate on which LED chips are arranged and mounted opposite to a substrate on which a mirror lens array is formed. The substrate on which the mirror lens array is formed can be formed by forming a transparent resin substrate into a mirror array shape and then evaporating aluminum. Further, as shown in FIG. 10, the structure can be formed by filling a transparent resin on a substrate on which a mirror lens array is formed, flattening the substrate, and then mounting an LED chip. In the above description, the LED chip is arranged at the position of the main focal point of the mirror lens. Further, in order to prevent direct light from the LED chip from being emitted upward, a reflector is provided on the LED chip surface opposite to the surface facing the mirror. In addition, in the present invention, various configurations using a mirror lens array are possible.

In the previous example, an LED was used as the light emitting element of the planar light source of the present invention, but other light emitting elements are also possible. Figure 1
1 is an example in which a thin-film inorganic EL is used for the flat light source of the present invention. A transparent electrode such as ITO is formed on a transparent substrate such as glass, and a first insulating layer such as SiO ₂ or a ferroelectric is formed thereon. An inorganic EL layer made of ZnS: Mn or the like is formed by patterning only on an appropriate region that can be regarded as a point light source. A second insulating layer of the same material as described above is formed thereon, and finally a reflective electrode made of a metal film such as aluminum is formed. On the other hand, a microlens array is formed on the back surface of the substrate. When an AC voltage is applied between both electrodes, only the patterned area emits light, and most of the light is emitted to the microlens side, and becomes parallel light by the microlens array.
The emission color can be determined by selecting an inorganic EL material as appropriate.
From V light to visible three primary colors, R light, G light, B light, and white are possible.

FIG. 12 shows an example in which an organic EL is used for the flat light source of the present invention. A transparent electrode such as ITO is formed as an anode electrode on a transparent substrate such as glass. S on it
An opening is provided only in an appropriate region where an insulating layer such as iO ₂ can be regarded as a point light source, and patterning is performed. An organic EL layer and a metal reflective film such as MgAg are formed thereon as a cathode electrode. The organic EL layer can be appropriately selected from a low-molecular organic material, a high-molecular organic material, and the like. The layer configuration can be appropriately selected from a layered structure including an electron / hole transport layer and a single-layered structure. On the other hand, a microlens array is formed on the back surface of the substrate. When a DC voltage is applied between both electrodes, only the opening of the insulating layer emits light, and most of the light is emitted to the microlens side, and becomes parallel light by the microlens array. The emission color can be selected from the three primary colors visible from UV light by appropriately selecting the inorganic EL material.
Light, G light, B light and even white are possible.

FIG. 13 shows an example in which a field emission type light emitting element is used as the flat light source of the present invention. A cathode electrode is formed on a cathode substrate, and an electron emission layer is formed thereon. The electron emission layer is formed of a material and a structure from which electrons are emitted by an electric field. For example, metals such as Mo and W, semiconductors such as Si, and materials such as carbon are suitable.
The electron emission amount is formed so that the electron emission region is scattered. On the other hand, a transparent anode electrode and a phosphor that emits light by electronic excitation are formed on a transparent anode substrate. If necessary, a metal back such as an aluminum thin film is formed on the phosphor. The two substrates are opposed to each other so that the electron emission layer and the phosphor face each other, and the inside is sealed in a high vacuum state. The phosphor is appropriately patterned so that its light emitting region can be regarded as a point light source, and is opposed to the above-mentioned electron irradiation emitted from the electron emitting region. A microlens array is arranged on the outer surface of the anode substrate. With this configuration, when a high voltage is applied so that the cathode electrode is negative and the anode electrode is positive, electrons are emitted from the electron emission layer, accelerated according to the applied voltage, and collide with the opposing phosphor. The phosphor emits light when excited by impact electrons. The emitted light is emitted forward and backward, but the backward component is reflected by the metal back and emitted forward. This light-emitting area can be regarded as a point light source by the above-described configuration. Further, by arranging the light emitting region at each principal focal position of the micro lens array, light incident on the micro lens array is converted into parallel light. The emission color can be changed from UV light to R light, G light, B light, and white, which are three primary colors, by appropriately selecting the phosphor.

For the microlens array, a microlens array sheet formed of resin may be attached to the light emitting element substrate, or the microlens array may be formed directly on the substrate. In addition, in order to facilitate the alignment between the light emitting element, which is a point light source, and the microlens, a microlens array is formed in advance on the substrate, and the exposure is performed from the microlens array side in patterning the light emitting element by photolithography. Thus, a so-called self-alignment can be formed. It should be noted that various configurations other than the previous example are possible, and the configuration of the light emitting source array which can be regarded as a point light source and the optical element such as a microlens array which parallels them, which is the gist of the present invention, is not limited to the previous example.

FIG. 14 shows the LED chip of FIG.
It is a figure showing the example used as a chip. Next, the field sequential drive will be described with reference to FIG. FIG. 14 shows the LED chip 2 of FIG.
3 LEDs of light LED chip 8 and B light LED chip 9
It has been replaced with a chip. The field sequential driving is basically a method of displaying an arbitrary color by additive color mixing in three independent colors R, G, and B at the time.

Specifically, a plurality of R, G, and B light sources of different colors as shown in FIG. 14 are used to enable independent brightness adjustment for each color, thereby providing a plane light source exhibiting uniform surface brightness. As shown in FIG. 15, for example, a field period T of 60 Hz at which flicker does not occur (T = 1/60 sec)
Is further divided into three times T / 3 (T / 3 = 1 /
The RGB LED chips are sequentially turned on at intervals of 180 sec., And an LCD light modulating element array, a flexible thin film light modulating element array, etc. are arranged thereon, and light modulation according to an image signal is synchronized with turning on of each color LED. By doing
Any color display is possible. FIG. 15 shows LE of R and G light.
When the light modulation element is turned on (transmitted) at the timing when D is turned on, it is indicated that R + G = yellow display can be performed. Similarly, when the light modulation element is turned on (transmitted) at the timing when the R, G, and B light LEDs are turned on, R + G + B =
White display becomes possible.

The color display by such a field sequential drive is: 1, high resolution 2, reduction of the number of driver ICs 3, easy adjustment of color balance, as compared with a conventional color LCD by flat additive color mixing using a color filter. (Easy white balance) 4. The advantage that no color filter is required is produced. 1 and 2 are achieved because the number of segment lines is reduced, and 3 is achieved because control is possible for each color.

The above is an example in which the LED chip is used to perform the filled sequential driving. However, even if a light emitting element other than the LED chip, for example, an organic, inorganic EL, FED, or the like is used, a point light source can be used, and similar driving is possible. Can be configured. 16, 17, and 18 show R
This is an example of a planar light source using light emitting elements other than LEDs that independently emit light, G light, and B light. FIG. 16 shows a thin-film inorganic EL element. The inorganic EL layer is made of a material that emits R light, G light, and B light, and is patterned to be regarded as a point light source. Further, the reflective electrode is also separated corresponding to each color, and each color can emit light independently. Inorganic EL similar to the previous example
Light emitted from the layer is collimated by the microlens array and emitted. FIG. 17 shows an organic EL element. The organic EL layer is made of a material that emits R light, G light, and B light, and is formed by patterning so as to be regarded as a point light source. Further, the cathode electrode is also separated for each color, and each color can emit light independently. As in the previous example, the light emitted from the organic EL layer is collimated by the microlens array and emitted. FIG. 18 shows a field emission device in which phosphors are R light, G light,
It is made of a material that emits B light, and is patterned to be regarded as a point light source. Further, the cathode electrode is also separated for each color, and each color can emit light independently. As in the previous example, the light emitted from the phosphor is collimated by the microlens array and emitted. As described above, a display element that can be field-sequentially driven can be configured by a plane light source capable of emitting each color independently.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 19 is a sectional view of the flat light source device according to the second embodiment of the present invention. FIG. 20 shows FIG.
2 is an enlarged view of the flat light source shown in FIG. In FIG. 19, 10
Denotes a light guide made of a material such as acryl, glass, polycarbonate, etc., 11 denotes a deflecting means such as a half mirror, and 12 denotes outgoing light obtained by deflecting incident light in the vertical direction. Deflection means 11
As a specific example, a medium made of a transparent material having a different refractive index from the light guide 10 is preferable. In practice, a plurality of light guides 10 are stacked diagonally as shown in the figure, and the gap between them is fixed with an adhesive layer.
This adhesive layer corresponds to the deflecting means 11 described above, and its refractive index has a slight difference from the refractive index of the light guide 10.

As shown in the enlarged view of FIG. 20, when the collimated light 6 from the planar light source 1 by the LED chip 2 and the microlens array 4 as shown in FIG. A part is reflected by a medium (11) made of a transparent material having a different refractive index and emitted as a deflection 12 in the vertical direction. Further, the rest of the incident light 6 is transmitted, and is sequentially reflected such that a part of the light is reflected by the next half mirror 11. The combination of the light guide plate 10 and the flat light source unit 1 is also developed in the depth direction of the drawing, so that light emitted in the vertical direction is emitted as a surface light source,
A display element can be obtained by placing an LCD (not shown), a flexible thin film type light modulation element, and the like on the upper surface side of the light guide 10 and making the emitted light 12 incident thereon. Further, the use of a surface light source is expanded.

The collimated light 6 incident on the light guide 10
Attenuates from the first half mirror 11 to the right (to the right in the drawing), so that the distance between the half mirrors 11 is L6, L1
The light guide 1 can be corrected by reducing the distance between the light guides L7 and the like.
From 0, outgoing light 12 of uniform intensity is emitted. This can be incident on a light modulation element (not shown) to form a display element. By changing the configuration of the light guide plate, it is possible to separate the polarization components of the P wave and the S wave. Specifically, a plurality of light guides 10 are stacked so as to be inclined at an angle of 45 °, and the gap between them is fixed by an adhesive layer corresponding to the deflecting means 11. As the refractive index of the adhesive layer, an adhesive material having a refractive index difference of 3% or less with respect to the refractive index of the light guide 10 is selected. In this case, the Brewster angle at the interface between the light guide and the adhesive layer is approximately 45 °, and a part of the S-wave polarization component of the light incident on the interface is reflected and emitted in the vertical direction. The P-wave polarization component travels straight through the light guide plate and is transmitted. 1 / on the terminal side surface of the light guide plate
When a four-wavelength plate and a reflector are provided and a reflector is provided on the bottom surface, the transmitted P-wave polarization component is reflected by the terminal side surface, converted into an S-wave polarization component, and proceeds toward the light source. Again, part of the S-wave polarization component that has entered the deflecting means is reflected toward the bottom surface, and is emitted in the vertical direction by the reflector on the bottom surface. Therefore, only the S-wave polarization component is emitted in the vertical direction.
By combining this flat light source device with a light modulation element such as an LCD that uses polarized light, a display element with high light use efficiency can be configured. In the above example, the light source is LE
D chip, but inorganic EL and organic E as in the previous example
L, a field emission device may be used.

Further, this flat light source is also suitable for a color display element driven by field sequential driving.
As shown in FIG. 21, when collimated light from a flat light source composed of an R light source, a G light source, a B light source and a microlens array is incident on a light guide plate, a part of the incident light is reflected by a half mirror and emitted in a vertical direction, and each color is emitted. Can be configured as a collimated planar light source that can be controlled independently. In FIG. 21, one light source is arranged for one microlens.
The R light source, the G light source, and the B light source may be collected and arranged for one microlens. In addition, so that the brightness and color are uniform in the plane finally emitted as a planar light source,
Light sources and microlenses for each color may be appropriately arranged.
According to the configuration of the present embodiment, it is not necessary to dispose the collimated light source over the entire surface of the flat light source, and it is possible to greatly reduce the number and area of the light source required for the collimated light source, thereby realizing low cost. it can.

An embodiment of the display element of the flat light source and the electro-mechanical light modulation element of the present invention will be described. FIG.
2. FIG. 23 shows a specific example thereof. As an example of the light modulation element, an optical length is controlled by changing the optical length of the light interference thin film by electromechanical operation. Further, the wavelength of the planar light source of the present invention is near-UV light, and a phosphor formed on a glass substrate is disposed on the emission side of the light modulation element. The phosphor emits light by being excited by the near-UV light, and converts the near-UV light into visible light. FIGS. 22 and 23 are explanatory diagrams of a single pixel. In an actual display element, the light modulation elements are arranged in an array.

In FIG. 22, as shown in FIG.
A half mirror composed of a transparent electrode and an ultrathin metal film or a dielectric multilayer film is formed on a glass substrate, and a transparent spacer composed of an insulating film is provided thereon. Further, a flexible thin film partly supported by a glass substrate is formed thereon via a gap. The flexible thin film has the same half mirror and transparent electrode as described above. The reflectance of the half mirror is preferably about 0.80 to 0.95. When the voltage between the upper and lower transparent electrodes is 0, the optical length doff between the upper and lower half mirrors is determined by the transparent spacer and the gap. As shown in FIG. 22A, a glass substrate having a phosphor is disposed on the light modulating element with the phosphor side facing the light modulating element, and below the light modulating element, as shown in FIG. 2), a collimated planar light source that emits near-UV light is arranged.

On the other hand, when a voltage Von is applied between the upper and lower transparent electrodes as shown in FIG. 23, the flexible thin film bends toward the substrate due to the electrostatic force acting between the transparent electrodes and contacts the transparent spacer. At this time, the optical length don between the upper and lower half mirrors is determined only by the transparent spacer. Here, the optical length is set to off = 2.
When the wavelength is set to 73 nm and don = 186 nm, the respective spectral transmittances for light that is incident on the light modulation element substantially perpendicularly are as shown in FIG. Therefore, when near-UV light (this spectral characteristic is shown in FIG. 24) is incident on the light modulation element substantially perpendicularly,
When the voltage = 0, the near-UV light is blocked, and when the voltage Von is applied, the near-UV light is transmitted. The transmitted near UV light excites the phosphor, and emits visible light. Since the phosphor emits scattered light, it is possible to display an element having extremely excellent viewing angle characteristics. If the R, G, and B phosphors are arranged for each pixel, full-color display can be easily realized. Here, if the angle of incidence on the light modulation element is large, the spectral transmittance shifts to the shorter wavelength side, and as a result, the transmittance particularly when ON is reduced. According to the collimated flat light source of the present invention, such a problem can be eliminated.

Next, an example of field sequential driving will be described. FIG. 26 shows an arrangement in which a light modulating element by electromechanical operation utilizing the above-described optical interference is arranged for a collimated planar light source capable of independently controlling R light, G light and B light. A light diffusion layer formed on a glass substrate is disposed on the emission side. With such a configuration, as shown in FIG.
60 LED chips of RGB with a field cycle of 0 Hz
Hz, the light modulator 13 is turned on / off sequentially.
By controlling the f timing, color display such as yellow, white, red, and green can be performed. Here, the light transmitted through the light modulation element is diffused and emitted by the light diffusion layer, and a display with good viewing angle characteristics is obtained. According to this embodiment, it is possible to realize an inexpensive display device with high definition, high light utilization efficiency.

In FIG. 27, the collimated light from the flat light source 1 is incident on the microlenses 4d. However, the reflected light from the half mirror 11 is incident via the light guide 10 of the previous embodiment. May be. Note that, in addition to the above example, for an optical modulation element in which incident angle dependence is a problem,
The flat light source of the present invention is effective.

[0039]

As described above, according to the present invention,
A plane that emits white or color collimated light by arranging a plurality of light emitting elements such as LED chips, ELs, or FEDs on a plane, and arranging optical elements such as a microlens array corresponding to these emitted lights. Since the light source is configured, there is an effect that a practical collimated light planar light source can be obtained with a simple configuration. In addition, since a display element of various types such as an electromechanical operation type can be configured by using the above-mentioned flat light source, a high-definition display element having a small viewing angle dependency and requiring no backlight such as a fluorescent lamp and a color filter is required. There is also an effect that it can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a flat light source according to a first embodiment of the present invention.

FIG. 2 is a front sectional view of the flat light source shown in FIG.

FIG. 3 is a cross-sectional view of a flat light source in which the microlens of FIG. 2 is a spherical lens.

FIG. 4 is a diagram showing an example in which the microlens of FIG. 2 is configured by a mirror lens array.

FIG. 5 is a diagram showing a structure and wiring of the LED chip shown in FIG. 1;

FIG. 6 shows a plurality of LEs using a chip vertical type hybrid.
It is a block diagram of D.

FIG. 7 shows a plurality of LEs using a chip horizontal type hybrid.
It is a block diagram of D.

FIG. 8 is a configuration diagram of a plurality of LEDs formed by monolithic formation.

FIG. 9 is a view showing an example in which an LED chip mounting transparent substrate is arranged to face a mirror lens array forming substrate.

FIG. 10 is a diagram illustrating an example in which a transparent resin is filled on a mirror lens array forming substrate and flattened, and then an LED chip is arranged and mounted.

FIG. 11 is a diagram showing an example in which a thin-film inorganic EL is used for the flat light source of the present invention.

FIG. 12 is a diagram showing an example in which an organic EL is used for the flat light source of the present invention.

FIG. 13 is a diagram showing an example in which a field emission (field emission) type light emitting element is used for the planar light source of the present invention.

FIG. 14 is a diagram showing an example in which the LED chip of FIG. 2 is a three-color LED chip.

15 is an explanatory diagram of field sequential driving of the flat light source shown in FIG.

FIG. 16 is a diagram showing an example of a thin-film inorganic EL element having an inorganic EL layer made of a material that emits R light, G light, and B light, which is patterned so as to be regarded as a point light source.

FIG. 17 is a diagram showing an example in which an organic EL element including an organic EL layer made of a material that emits R light, G light, and B light is patterned so as to be regarded as a point light source.

FIG. 18 is a diagram showing an example of a field emission device including a phosphor composed of a material that emits R light, G light, and B light, which is patterned so as to be regarded as a point light source.

FIG. 19 is a sectional view of a flat light source device according to a second embodiment of the present invention.

20 is an enlarged view of the flat light source shown in FIG.

FIG. 21 is an enlarged view of a collimated planar light source in which collimated light from a planar light source composed of an R light source, a G light source, a B light source and a microlens array is partially reflected by a light guide plate and a half mirror so that each color can be controlled independently. .

FIG. 22 is a diagram showing a flat light source and a display element of a light modulation element by electromechanical operation according to an embodiment of the present invention, in which a voltage between upper and lower transparent electrodes is zero.

FIG. 23 is a diagram illustrating a case where a voltage Von is applied between upper and lower transparent electrodes of the display element in FIG. 22;

FIG. 24 is a diagram showing spectral characteristics of near-UV light.

FIG. 25 is a diagram showing the spectral transmittance (wavelength vs. relative intensity) of each optical length (279 nm and 186 nm) with respect to light that is substantially perpendicular to the light modulation element.

FIG. 26 shows a configuration in which a light modulating element by electromechanical operation utilizing light interference is arranged for a collimated planar light source that can independently control R light, G light, and B light, and a light diffusion layer is arranged on the emission side. In the example of the display element, the voltage Vo is applied between the upper and lower transparent electrodes.
It is a figure which shows the time when n was applied.

FIG. 27 is a sectional view of a display element according to a third embodiment of the present invention.

FIG. 28 is a configuration diagram of a conventional display element.

FIG. 29 is a view showing a viewing angle improved type of the display element shown in FIG. 28.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Planar light source 2 LED chip 3 Back substrate 4 Micro lens array 5 Front substrate 6 Collimated light 7 R light LED chip 8 G light LED chip 9 B light LED chip 10 Light guide plate 11 Half mirror 12 Reflected light 13 Light modulation element 14 Diffusion element 15 Pinhole 16 Phosphor 23 Signal electrode 29 Flexible thin film 43 Scanning electrode 45 Power supply 169 Diffusion plate 161 Display element

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13357 H01L 33/00 L H01L 33/00 G02F 1/1335 530 F-term (Reference) 2H042 CA06 CA14 CA17 DB01 DD04 DD08 DE04 2H091 FA14Z FA23Z FA29Z FA31X FA44Z FA45Z LA15 LA30 2H093 NA65 ND17 5F041 DA57 DA82 DB08 EE17 EE23 FF06 5G435 AA02 BB01 FF03 FF06 GG02 GG09 GG12 GG23 HH02 HH06

Claims (14)

[Claims] 1. A light emitting device comprising: a plurality of light emitting elements scattered on a plane; and an optical element arranged corresponding to light emitted from the light emitting element. A planar light source that emits light vertically. 2. A flat surface light source, comprising: the flat light source according to claim 1; and means for directing an incident side to an outgoing light side of the flat light source to deflect incident light from the flat light source substantially vertically. Light source device. 3. The flat light source according to claim 1 or claim 2.
A display element, comprising: the flat light source device according to any one of the preceding claims, a light modulation element, and a diffusion unit. 4. The display device according to claim 3, wherein the color emitted from the flat light source or the flat light source device is switched in a time sequential manner within one field period, and the light modulation element is driven in synchronization with the time. A display element characterized by the above-mentioned. 5. The flat light source according to claim 1 or claim 2.
A display element, comprising: the planar light source device described above; a light modulation element; a diffusion unit; and a color filter. 6. A flat light source according to claim 1 or claim 2.
A display element comprising: the planar light source device described above; a light modulation element; and a phosphor, wherein the phosphor emits and emits light by the planar light source or light emitted from the planar light source device. 7. The flat light source or the flat light source device may be a UV light source.
The display device according to claim 5, wherein the display device emits light. 8. The display device according to claim 3, wherein the light modulation device is a liquid crystal device or a light modulation device operated by electromechanical operation. 9. The flat light source according to claim 1, wherein the optical element is a microlens array. 10. The flat light source according to claim 1, wherein the optical element is a mirror lens array. 11. The flat light source according to claim 1, wherein the light emitting elements are made of a plurality of colors that can be output independently. 12. The flat light source according to claim 1, wherein the light emitting element is an LED. 13. The flat light source according to claim 1, wherein the light emitting element is an organic or inorganic EL. 14. The flat light source according to claim 1, wherein the light emitting element is an FED.