JPS6331519Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electroluminescent lamp, particularly to improving variations in luminance distribution due to a voltage drop in the resistance of a transparent conductive film.

Generally, the electroluminescent lamp 1 is as shown in FIG.
Between a pair of flat electrodes 2 and 3, at least one of which is transparent, is a phosphor layer 4 in which phosphor powder is dispersed in a high dielectric constant organic binder, and an insulator in which high dielectric fine particles are dispersed in an organic binder. A light emitting element 6 having a structure in which a layer 5 is laminated in a thin layer is covered with moisture-resistant resin outer skins 7 and 8 from both sides and the peripheral edge of the element 6 is sealed, and is connected to the ends of both electrodes 2 and 3. When an AC power source is connected to the electrode leads 9 and 10 and a high voltage is applied, the phosphor powder inside the phosphor layer 4 is excited and emits light, which is emitted to the outside from the transparent electrode 2 in front of the phosphor layer 4. Ru.

By the way, the transparent electrode 2 is generally made of a transparent conductive film 2b of indium oxide or tin oxide coated on one side of a transparent insulating substrate 2a such as polyester or mylar, and this conductive film 2b is transparent. It is formed into a particularly thin film to improve its properties, and its volume resistance usually reaches several kilohms. Therefore, in an electroluminescent lamp using a long electrode layer with a large light emitting surface, a voltage drop occurs at the conductive film 2b of the transparent electrode 2, causing uneven brightness on the light emitting surface. For this reason, the transparent electrode 2 using the transparent conductive film 2b having a higher resistance than the conventional one has a current collecting band 11 made of Ag paste or the like on the longitudinal edge of the conductive film 2b, as shown in FIG. A method has been adopted in which the voltage drop in the conductive film 2b is dealt with by forming the conductive film 2b.

However, with this method of dealing with the voltage drop across the conductive film 2b in the current collecting band 11, if the light emitting surface is relatively small and the lighting is performed at a low frequency (for example, 60 Hz), the uneven brightness will not be much of a problem. If the light-emitting surface is long (e.g. 100 mm or more) and it is lit at high frequency (e.g. 1KHz), the voltage drop cannot be compensated for and a large brightness difference will occur between the power supply side and the unfinished side of the light-emitting surface, which may be harmful to the eyes. It was clearly confirmed that brightness unevenness occurred on the light emitting surface. In this way, conventional electroluminescent lamps produce a voltage drop within the conductive layer of the transparent electrode,
In particular, in an electroluminescent lamp with a long light emitting surface, the luminance distribution varies between the power supply side and the end side. Efforts have been made to reduce the resistance of the current path on the electrode surface by forming a current collecting band on the transparent conductive film. However, the former impairs the light transmittance of the transparent electrode, and the latter not only reduces the size of the light transmitting surface film of the transparent electrode, but also cannot be sufficiently corrected when the brightness is increased by the above-mentioned high frequency drive. Ta.

The present invention has been proposed in view of the above, and provides an electroluminescent lamp that can provide a light emitting surface with a uniform luminance distribution even when driven at high frequencies.

The present invention's measures to improve the variation in luminance distribution of the light emitting surface were made by focusing on the fact that generally, the higher the voltage applied to a phosphor, the higher the luminance can be obtained.
That is, in the electroluminescent lamp according to the present invention, the ratio of the thickness of the phosphor layer interposed between both electrodes to the insulating layer decreases as the voltage due to the resistance of the transparent electrode increases from the power supply side of the transparent electrode to the end side. It is characterized by a small setting that compensates for the drop and provides uniform luminance over the entire surface, and the decrease in the voltage applied to the phosphor layer due to the voltage drop in the conductive film reduces the thickness of the phosphor layer. This is complemented by the improvement in electric field strength caused by high frequency lighting, and even at high brightness caused by high frequency lighting, a uniform light emitting surface is obtained and brightness unevenness is improved.

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

FIG. 3 shows a cross-sectional view of the electroluminescent lamp 12 according to the present invention, which, like the conventional electroluminescent lamp 1, has the following features:
A light emitting element 13 in which a phosphor layer 4 and an insulator layer 5 are laminated between a pair of flat electrodes 2 and 3 is attached to both electrodes 2 and 3.
The electrode leads 9 and 10 are shown sealed with moisture-resistant resin outer sheaths 7 and 8, leaving the external lead-out portions connected to the ends of the electrode leads 9 and 10. Here, the same functional parts as in FIG. 1 are indicated by the same symbols. The difference between this electroluminescent lamp 12 and the conventional electroluminescent lamp 1 is the thickness composition ratio of the phosphor layer 4 and the insulator layer 5 interposed between the electrodes 2 and 3. The film thickness ratio t ₁ /t ₂ of the phosphor layer 4 to the insulator layer 5 becomes smaller as it goes from the power supply side of the transparent electrode 2 to the far end side, whereas the body layer 5 was formed to have a uniform thickness. This is the point. In this figure, the film thickness t ₂ of the insulator layer 5 is kept constant, and the film thickness t ₁ of the phosphor layer 4 is formed to become thinner from the power supply side to the far end side. .

In order to make the film thickness _t1 of the phosphor layer 4 thinner as it goes from the power supply side to the far end side, a phosphor layer paste in which phosphor powder is dispersed in an organic binder with a high dielectric constant is used. Apply using screen printing method,
A method was implemented in which multilayer printing was performed by repeating drying several times. In other words, each time you print,
By moving the printing roller from the end side of the phosphor layer 4 to the power supply side, it was possible to make the end side of the phosphor layer 4 thinner and the power supply side thicker. Figure 4 shows the luminance distribution characteristics at three locations along the longitudinal direction of the electroluminescent lamp 12 created in this way: the power supply side, the center, and the end side.
In the results measured under the measurement conditions of 100v/60Hz and 100v/1KHz, the dotted lines a and a' are those of the conventional example in which the thickness of the phosphor layer 4 and insulator layer 5 are each formed at a constant 35μ, and the solid line is the result of measurement. b, b′ is the film thickness t ₂ of the insulator layer 5 of 40μ
The structure of the present invention is shown in which the film thickness t ₁ of the phosphor layer 5 is kept constant and is made thinner from 40μ to 30μ from the power supply side to the end side. As is clear from the figure, the configuration of the present application has a low frequency of 60Hz (curve b')
Of course, even at a high frequency of 1 KHz (curve b), a uniform brightness distribution is obtained.

What is particularly noteworthy here is that in the above embodiment, the current collecting band 11 formed on the transparent conductive film 2b of the transparent electrode 2 is formed only at the connection periphery of the electrode lead 9, and extends in the longitudinal direction. Since there is no need to form a transparent electrode 2, there is no need to block internal light emission.
can be used effectively.

Furthermore, the method of forming the phosphor layer thinner from the power supply side to the terminal side in the present invention is not limited to the screen printing method; for example, the doctor blade method can reduce the thickness of the phosphor layer from the power supply side By tilting the doctor blade to make it thicker,
If using the press method, the press mold should meet the above conditions, or if using the spray method, the power supply side of the phosphor layer should be placed close to the spray head, and the phosphor slurry should be applied diagonally. This can be done by spraying, etc.

As described above, in the present invention, the thickness of the phosphor layer laminated between both electrodes increases as the distance from the power supply side increases.
Compensating for the voltage drop caused by the resistance of the transparent electrode relative to the thickness of the insulating layer, it is formed thin so that the entire surface has uniform luminance, and the applied voltage is reduced due to the voltage drop across the transparent conductive film. Since this is corrected by increasing the electric field strength applied to the phosphor layer,
An electroluminescent lamp with a uniform luminance distribution over a long and large light emitting surface can be obtained.

In the above embodiments, the thickness of the insulator layer is kept constant and the thickness of the phosphor layer is varied, but various modifications such as changing the thickness of the insulator layer or both are also possible, and similar changes can be made. The effect of this can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional electroluminescent lamp, Fig. 2 is a sectional view taken from the - line in Fig. 1, Fig. 3 is a sectional view of the electroluminescent lamp of the present invention, and Fig. 4 is a sectional view of the electroluminescent lamp of the present invention. It is a brightness distribution characteristic diagram obtained by. 1... Electroluminescent lamp, 2... Transparent electrode, 4... Fluorescent layer, 5... Insulator layer.

Claims (1)

[Claims for Utility Model Registration] In an electroluminescent lamp comprising a pair of planar electrodes, at least one of which is transparent, a phosphor layer and an insulating layer are interposed between the phosphor layer and the transparent electrode. An electroluminescent lamp characterized in that the lamp is formed so that the voltage drop due to the resistance of the transparent electrode is compensated for as the distance from the side increases relative to the thickness of the insulating layer, so that the luminance is uniform over the entire surface. .