JP2003197364A - El light emitting device with high light emission efficiency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL light emitting device capable of improving emission efficiency for clarifying a displayed image. <P>SOLUTION: In this EL light emission device, a synthetic resin layer, in which a lens array formed by arranging multiple three-dimensional patterns each having a lens function is formed, is optically integrated on the light emission face of this EL light emission device while the lens array is set on the light emission side. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a television, a personal computer,
The present invention relates to an EL light emitting device used for a flat panel display suitable for a display device such as a mobile information terminal and a mobile phone, and particularly to an EL display device preferably used for a backlight of a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used in these information devices, particularly portable information devices, in accordance with the demand for higher performance and lighter weight of these devices. The liquid crystal display is lighter,
Due to the features of thinness and power saving, the backlight or front light is indispensable for producing beautiful images because it is the optimum display for information devices and portable information devices, and it has been a brake for power saving. Therefore, in order to realize high brightness and high definition while realizing power saving, effective use of light from a backlight or front light using various optical films has been studied. Further thinning, downsizing and power saving are required.

On the other hand, EL light emitting devices have rapidly developed in recent years,
In particular, organic EL has come to a practical range. And, as its main features, it can operate in a low electric field as high as that of a liquid crystal display device and is suitable for a moving image of a self-luminous display device.
It is expected that it will be excellent in high-speed response and image clarity, and that it will be highly efficient in converting energy into light. Unlike a liquid crystal display device, a display device does not need to handle polarized light, and it is not necessary to consider absorption of light by a polarizing film, and a liquid crystal has a light blocking property due to the presence of an aperture ratio. While efficiency loss occurs, E
Since the L display device can emit only the necessary light emitting portion,
Power saving of display devices is expected.

Further, since the EL light emitting device is easy to obtain as a surface light source, it has been attempted to use it as a backlight of a liquid crystal display device. The advantage of this case is that the EL light emitting device has higher light utilization efficiency than the liquid crystal display device and can be developed into a uniform surface light source from a point light source or a line light source such as a conventional LED or a cold cathode tube. It is expected that the above-mentioned member is unnecessary. However, since the EL light emitting device is a self-luminous device, the power consumption is likely to be large, and therefore reduction of the power consumption is an issue.

[0005]

To reduce the power consumption of the EL light emitting device, improvement of the light emission efficiency is an important issue, but it is also important to improve the emission efficiency which is another aspect. The EL light emitting device has a structure in which a thin film is formed together with electrodes on a substrate. The light is emitted to the substrate side or the opposite side. In the method of emitting light to the substrate side, the light emitting body is formed on the transparent substrate, and in the method of emitting light to the opposite side, the light emitting body is protected and integrated on the emitting side by the transparent plate. Therefore, in the light emitting place, the vicinity of the emitting transparent plate or the emitting transparent plate itself serves as a light emitting source. As for the emitted light, the light rays in the direction nearly perpendicular to the emission transparent plate are emitted almost as they are, but the light rays in other directions are refracted at the interface between the emission transparent plate and the outside air and are emitted after turning the direction. In addition, a light ray having an angle equal to or larger than the critical angle at the interface with the air is trapped in the outgoing transparent plate and cannot be emitted, and as a result, the emission rate is reduced. The present invention intends to solve the problem by improving the emission rate.

[0006]

In order to solve the above-mentioned problems, the first aspect of the present invention is directed to a synthetic resin in which a lens array in which a large number of three-dimensional patterns having a lens function are arranged is formed on the emission surface of an EL light emitting device. An EL light-emitting device is characterized in that the layer is optically integrated with the lens array on the exit side.

According to a second aspect of the present invention, the three-dimensional pattern having a lens function is a prismatic shape which is substantially a triangular prism and is arranged so that the directions of the apexes thereof are substantially parallel to each other, or the cross-section is a sinusoidal curve. A three-dimensional pattern in which the longitudinal directions of the corrugated columnar bodies are arranged substantially parallel to each other, or a three-dimensional pattern in which the columnar bodies having a semicircular cross section are arranged so that their longitudinal directions are substantially parallel to each other, or The EL light emitting device according to claim 1, wherein the EL light emitting device has a three-dimensional pattern in which pyramidal or hemispherical convex units are provided.

A third aspect of the present invention is a lens array in which a large number of lens functions each having a three-dimensional pattern having a lens function are arranged at regular intervals on the light emitting surface of an EL light emitting device having an XY matrix display. The synthetic resin layer formed with a period of 1/3 or less with respect to the period direction of the unit pixel of the EL light-emitting device is optically integrated with the lens array as the emission side. The content of the EL light emitting device is as follows.

According to a fourth aspect of the present invention, the unit pixel of the XY matrix display has RGB three primary colors.
The content is the L light emitting device.

According to a fifth aspect of the present invention, the three-dimensional pattern having a lens function is a three-dimensional pattern in which the prismatic shape is substantially a triangular prism and the apexes are arranged substantially parallel to each other, or the cross section is a sinusoidal curve. A three-dimensional pattern in which the longitudinal directions of the corrugated columnar bodies are arranged substantially parallel to each other, or a three-dimensional pattern in which the columnar bodies having a semicircular cross section are arranged so that their longitudinal directions are substantially parallel to each other, or The EL light emitting device according to claim 3 or 4, which has a three-dimensional pattern in which pyramidal or hemispherical convex units are provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of an EL light emitting device is slightly different depending on the type of the light emitting layer.
A thin-film light emitting layer is provided on the O transparent electrode, and a back metal electrode is provided thereon. Generally, the light emitted from the light emitting layer is emitted through the transparent glass substrate. On the other hand, a method of emitting light to the side opposite to the substrate on which the light emitting layer is formed has also been announced (Sony: Announced in 2001.2.7). EL light emitting devices are classified into inorganic EL and organic EL depending on the type of light emitting layer. The inorganic EL is classified into a dispersion type as shown in FIG. 1 and a thin film type as shown in FIG. In the former case, a light emitting layer in which inorganic phosphor particles are dispersed in a binder polymer is formed in a thickness of 20 to 100 μm on a substrate coated with ITO. The light emitting layer can be formed by screen printing, spraying or coating. The back electrode is formed by adhesion of aluminum foil, application of conductive paste, and vapor deposition of aluminum. The latter thin film type has a structure in which a light emitting layer is sandwiched between two dielectric layers, and these layers are formed by a method such as vacuum deposition, sputtering, and CVD.

Generally, in the case of organic EL, a glass substrate is used, ITO formed by vacuum vapor deposition or sputtering is used for the electrodes on the substrate, and when the organic layer is a low molecular compound, vacuum heating vapor deposition or high temperature is used. In the case of molecules, it is formed by dip coating or spin coating and an inkjet printing method. The back electrode is formed by evaporating a metal such as magnesium / silver or lithium / aluminum. As shown in FIG. 3, the organic layer consists of a hole transport layer and an electron transport layer.
As shown in FIG. 4, the light emitting layer further comprises three or more layers. Then, depending on in which layer the light emitting layer occurs, two types can be considered as shown in (a) and (b) respectively. In any case, the thickness of the entire layer is as thin as 1000 to 2000Å, and light is emitted on the transparent substrate.

A glass substrate is often used as the transparent substrate of the EL light emitting device, but a synthetic resin substrate is also used. In this case, the moisture and oxygen barrier properties are important in order to maintain the reliability and durability of the light emitting device, and in the case of a synthetic resin substrate, the moisture and oxygen barrier properties are particularly taken into consideration.

Since the EL light-emitting device emits light in the vicinity of the emission-side back surface of the transparent substrate, which is extremely close to the front surface, an uneven structure may be provided on the emission surface so as to facilitate emission. In this case, since the emitted light becomes scattered light, light loss is likely to occur, and when the emission surface of the display device has a concavo-convex structure, characters and images are difficult to blur. Therefore, it is necessary to regularly emit the emitted light without scattering it.

A three-dimensional pattern of a synthetic resin layer (hereinafter referred to as a prism film) having a lens array in which a plurality of three-dimensional patterns having a lens function optically integrated with the emission surface of an EL light-emitting device is formed is substantially A prismatic shape consisting of triangular prisms, arranged in such a way that the directions of the apexes are almost parallel to each other, or a columnar body having a corrugated sinusoidal cross section and arranged so that their length directions are substantially parallel to each other Examples thereof include a pattern, a three-dimensional pattern in which columnar bodies having a semicircular cross section are arranged so that their length directions are substantially parallel to each other, or a three-dimensional pattern in which pyramid-shaped or hemispherical convex units are continuously arranged.

The prism-shaped triangular prism has a triangular cross-section, and the shape of the triangle may be equilateral or unequal, but when the emitted light is guided in a direction perpendicular to the EL light emitting layer surface, it is an equilateral triangle, especially two sides. It is preferable to integrate the equilateral triangles in the emission direction. The apex angle of the triangle can be selected widely,
60 to 150 ° is preferable. If it is less than 60 °, the emission directions are too divided, while if it exceeds 150 °, there is little effect of directing it in the desired emission direction. Further, it is preferable to use a lens array in which the directions of the apexes are substantially parallel to each other and at the same time, the slopes of the triangular prisms are connected so that the slopes of the adjacent prisms are in common with each other. Further, this prism shape may be a lens array having a curvature at the top and / or the valley, and a columnar body having a sinusoidal waveform, which is a cross section in which the top and the valley have both curvatures, and the length directions thereof are substantially the same as each other. A three-dimensional pattern arranged in parallel may be used. Further, it is also possible to use a three-dimensional pattern in which semicircular or partial circular arc-shaped columnar bodies are arranged so that their length directions are substantially parallel to each other. A lens array in which pyramidal or hemispherical convex units are continuously arranged on a plane is also preferable.

The prism film is obtained from a transparent synthetic resin. Examples of the transparent synthetic resin include acrylic resin, polystyrene, polyolefin, polycarbonate, polyester and the like. As the molding method, various synthetic resin molding methods can be adopted. In injection molding or compression molding, an original plate having a three-dimensional pattern of a lens array is produced by a precision milling machine or the like, and a stamper is produced from the original plate by electroforming (JP-A-6-26570) to produce a die. In extrusion molding, for example, as described in Japanese Patent No. 2925069, transparent synthetic resin is melt-extruded using a release sheet having a three-dimensional pattern, and the three-dimensional pattern of the release sheet is transferred to a molten resin layer. There is a method for producing a precise three-dimensional pattern by doing.

Further, a method of manufacturing using a transparent curable synthetic resin is also known. In this case, it is manufactured by injecting or coating a liquid curable synthetic resin into a mold and then solidifying it by heat or actinic radiation such as ultraviolet rays or electron beams. At this time, a synthetic resin sheet or film of a multi-layer lens array obtained by solidifying together with another transparent substrate can be used.

The other surface of the lens array of prism film is substantially planar. However, the other surface of the lens array may be a flat surface having a fine concavo-convex structure in order to improve the peeling strength and the adhesive strength of the bonding surface with the transparent substrate on which the EL light emitting layer is formed.

The prism film is optically integrated with the emission surface of the EL light emitting device with its lens array facing the emission side. The optical integration uses a transparent adhesive or pressure-sensitive adhesive to completely eliminate the air layer between the light emitting surface of the transparent substrate on which the EL light emitting layer is formed and the flat surface of the back surface of the lens array of the prism film. It is essential to do so. For this purpose, an optical adhesive or pressure-sensitive adhesive is applied to one of the integrated surfaces and then bonded to the other surface. In this case, a method in which adhesives or pressure-sensitive adhesives on both sides prepared on the release paper are adhered to one surface, and then the release paper is removed and the other surface is adhered are also suitably used. Also suitable is a method of pressurizing the integrated product in an autoclave to ensure integration and complete elimination of air.

The adhesive or pressure-sensitive adhesive used for the integration is preferably one for optical use and having high transparency, and this refractive index can be used if it is an ordinary polymer material. The most preferable refractive index of the adhesive or pressure-sensitive adhesive is equal to or higher than the refractive index of the transparent substrate on which the EL light emitting layer is formed, and lower than the refractive index of the material forming the lens array. This is to minimize the loss of light and the loss of light at the joint surface.

The path of light rays when the prism film is integrated with the light emitting surface of the EL light emitting device with an adhesive or a pressure sensitive adhesive with the lens array as the light emitting side will be shown as an example. First, the appearance of emitted light when a prism film is not provided on the light emitting surface of the EL light emitting device will be described with reference to FIG. That is, the EL light emitting layer 1 is
Light emitted from the light emitting device which is formed through the O electrode 2 and forms a light emitting surface will be described. Light emitted from the ITO electrode 2 is perpendicular to the light emitting surface with reference to the direction perpendicular to the light emitting surface. Although the light ray can go straight, the light ray with an exit angle of 30 ° is refracted at the interface of the exit surface and advances to the direction of 48.5 °, and the light ray with an exit angle of 41.8 ° is a critical angle of the glass substrate 3 (of glass). It reaches a refractive index of 1.50 and a critical angle of 41.8 ° and is in a direction parallel to the emission surface and cannot be emitted, and a light beam with an emission angle of 45 ° larger than this is confined in the glass substrate.

Next, the state of the emitted light in the case of the present invention in which the prism film is optically integrated with the light emitting surface of the EL light emitting device will be described with reference to FIG. That is, the same light emitting surface of the EL light emitting device as described above, that is, the surface of the glass substrate 3 is made of polycarbonate having a refractive index of 1.58, and has a cross-sectional shape of a right angle with a top angle of 90 ° and a base angle of 45 °. A prism film 8 having a thickness of 200 μm, which is a lens array in which three-dimensional patterns of equilateral triangles are arranged at a period of 50 μm, is attached. This bonding has a refractive index of 1.
A double-sided adhesive tape (product name: Pol-A manufactured by Polatechno Co., Ltd.) having a thickness of 25 μm and a thickness of 51 is used. In this case, the light is emitted in such a manner that a light ray perpendicular to the light emitting surface is reflected by the light emitting surface of the prism film 8 and returns to the light emitting surface, but is reflected by the back electrode (not shown) of the light emitting layer and collected. It Output angle 3
The ray of 0 ° hardly refracts at the interface between the light emitting layer glass substrate 3 and the adhesive layer 7, is refracted at the interface between the adhesive layer 7 and the prism film 8 and turns to 28.3 °, and then exits from the prism film 8. The surface is perpendicularized to a direction of 18.9 ° with respect to the vertical direction. Glass substrate 3 having the EL light emitting layer formed
The ray of 41.8 °, which was a critical angle in the above, was 39.degree. At the interface between the adhesive layer and the prism film 8 as in the case of the ray.
The light is refracted at 6 ° and refracted at the exit surface of the prism film 8 to be emitted at a direction of 36.6 ° with respect to the vertical direction. The light ray confined in the glass substrate having the exit angle of 45 ° is refracted at 42.5 ° at the interface between the adhesive layer 7 and the prism film 8, and is 4 ° with respect to the vertical direction at the exit surface of the prism film 8.
Emit in the direction of 1.2 °.

As described above, by optically integrating the prism film having the isosceles triangular lens array formed on the light emitting surface of the EL light emitting device, the direction in which the EL film is confined in the transparent substrate of the EL light emitting device. The light in the majority of directions can be collected vertically, including In the case of an isosceles triangle, the direction is biased toward the steep slope of the isosceles triangle, in the case of a corrugated or semicircular shape, it is in a direction similar to that of an isosceles triangle, and in the case of a pyramid or a hemispherical three-dimensional pattern, the light emitting surface and the vertical and horizontal directions. Both can collect light in the vertical direction or in a specific direction to improve the emission rate.

The EL light emitting device has many uses, but it is roughly divided into a case where it is used as a surface light source and a display device which can display characters and images. The former is useful as a backlight for a liquid crystal display device, as a surface light source capable of particularly uniform surface emission. The latter has pixels divided into an XY matrix, and characters and images are displayed by blinking the pixels. In the case of color display, the pixel has a structure in which RGB of three primary colors are developed. If the light emitted from this pixel is scattered or the emission direction between the pixels is disturbed, the image will not be clear. A function of one lens determined corresponding to this one pixel is provided, and when repeated for each pixel, no disturbance occurs in the light emission direction, so that a character image becomes clear. However, it is difficult to align the pixels of the EL light emitting device with the individual lens arrays in which a large number of three-dimensional patterns having a lens function of synthetic resin are perfectly aligned.

In order to substantially eliminate the disturbance in the emission direction of the pixel unit and improve the sharpness of the image, the lens function is the same in each part of the EL display surface, and the alignment error can be ignored. It has been found by the present inventors that the unit of the lens function should be sufficiently smaller than the unit of the pixel. For this purpose, it is only necessary that three-dimensional patterns having the same shape can be accurately created in the same cycle. Then, it was found that the unit of the lens function should be made smaller than the period of 1/3 of the pixel unit in practical use. In practice, EL
Since the pixel unit of the display device is in the range of 200 to 300 μm, the period of the three-dimensional pattern having a lens function is 70 μm.
The following units may be used.

The method of integration is the same as that of an EL light emitting device without an XY matrix structure, but a triangular prism having ridges and axes,
The bonding directions of the corrugated and semicircular lens arrays may be integrated so that the ridges or axes (length direction) are parallel to the direction in which the outgoing light rays are desired to be collected. In this case, interference fringes are likely to occur due to the pixel structure of the EL light emitting device and the periodicity of the lens array, but in order to avoid this, the ridges or axes of the lens array are shifted from the axial direction of the lattice fringes of the pixel structure of the EL light emitting device. It is good to integrate it. A suitable result is obtained when the degree of displacement is 3 ° or more. Also in this case, the period of the lens array is preferably ⅓ or less of the unit pixel in the same direction as the lens array period direction.

[0028]

As described above, the E according to the present invention
According to the L light emitting device, the following operational effects can be obtained. (1) The light confined in the transparent substrate on the emission side of the EL light emitting device is guided to the emission side to improve the light emission efficiency, and the display surface can be bright and the power consumption can be saved. (2) The reduction of the light trapped in the transparent substrate on the emission side of the EL light emitting device can reduce stray light, enhance the contrast, and make the displayed image clear. (3) Light can be guided in a desired direction by selecting a lens array.

[Brief description of drawings]

FIG. 1 is a basic structure of a dispersed inorganic EL.

FIG. 2 is a basic structure of a thin film type inorganic EL.

3A and 3B are diagrams showing a basic structure and a light emitting layer of a two-layer organic EL.

4A and 4B are diagrams showing a basic structure and a light emitting layer of a three-layer organic EL.

FIG. 5 is a diagram showing an optical path and a light emission state of light in an EL light emitting layer and a glass substrate.

FIG. 6 is a diagram showing an optical path and a light emission state of light when a lens array film is optically integrated on a light emission side of a glass substrate of an EL light emitting device.

[Explanation of symbols]

1 Light Emitting Layer 1.1 Electron Transporting Layer 1.2 Hole Transporting Layer 2 ITO Electrode 3 Glass Substrate 4 Dielectric Layer 5 Back Electrode 6 Carrier Block Layer 7 Adhesive Layer 8 Prism Film EL Light Emitting Surface Perpendicular Light Emitting Surface To the EL light emitting surface, which is 30 ° from the vertical direction, to the EL emitting surface, which is 41.8 ° from the vertical direction,

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiiragi Ohara             4-13-18 Anchi, Suminoe-ku, Osaka-shi, Osaka               Within Goyo Paper Co., Ltd. (72) Inventor Taizo Yasumoto             4-13-18 Anchi, Suminoe-ku, Osaka-shi, Osaka               Within Goyo Paper Co., Ltd. F term (reference) 3K007 AB03 AB17 BB06 DA04 DB03

Claims (5)

[Claims] 1. A layer of synthetic resin having a lens array in which a large number of three-dimensional patterns having a lens function are arranged is optically integrated on the light emission surface of an EL light emitting device with the lens array as the light emission side. An EL light emitting device characterized in that 2. A three-dimensional pattern having a lens function is a three-dimensional pattern having substantially prismatic prism shapes and arranged so that the directions of the apexes thereof are substantially parallel to each other, or a corrugated columnar body having a sinusoidal cross section. Three-dimensional patterns arranged so that their length directions are substantially parallel to each other, or three-dimensional patterns arranged in a columnar body with a semicircular cross section so that their length directions are substantially parallel to each other, or pyramidal or hemispherical The EL light emitting device according to claim 1, wherein the EL light emitting device has a three-dimensional pattern provided with convex units. 3. A lens array in which a large number of lens functions each having a three-dimensional pattern having a lens function are arranged at regular intervals on the light emission surface of an EL light emitting device having an XY matrix display, and the cycle is the EL. An EL light-emitting device characterized in that a synthetic resin layer formed at a period of ⅓ or less with respect to a period direction of a unit pixel of the light-emitting device is optically integrated with the lens array as a light emission side. . 4. The unit pixel for XY matrix display is RG.
The EL light-emitting device according to claim 3, which has B primary colors. 5. A three-dimensional pattern having a lens function is a three-dimensional pattern in which prism shapes are substantially triangular prisms and arranged so that directions of apexes are substantially parallel to each other, or a columnar body having a corrugated sinusoidal cross section. Three-dimensional patterns arranged so that their length directions are substantially parallel to each other, or three-dimensional patterns arranged in a columnar body with a semicircular cross section so that their length directions are substantially parallel to each other, or pyramidal or hemispherical The E according to claim 3 or 4, which is a three-dimensional pattern provided with convex units.
L light emitting device.