JPH031485A - Electroluminescent lamp - Google Patents

Abstract

PURPOSE:To provide good reflectance and accomplish a higher brightness by locating the distribution of particle sizes of high dielectric substance powder between the max. and min. values as specified. CONSTITUTION:In an EL lamp 10 an insulation layer 4 and a light emitting layer 5 are contacting each other, and the total output light is expressed by the sum of the direct incident light and reflected light. To maximize this reflected light, the particle sizes of highly dielectric particles are distributed according to Eq. I so that the light absorbed in the binder in the insulation layer 4 maximizes. In Eq I, lambda1 is max. wavelength of the spectral distribution in the EL lamp 10, lambda2 is the min. wavelength of the spectral distribution in the EL lamp 10, no is reflectance of the binder, and np the reflectance of the highly dielectric substance powder. This optimizes the highly dielectric substance powder used to insulation layer 4 according to the light emission wavelength, raise the brightness of the EL lamp 10, and achieves high brightness and high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroluminescent lamp, and particularly to improving the brightness and efficiency of an organic dispersion type electroluminescent lamp.

Traditionally, organic dispersion type electroluminescent lamps have an insulating material (for example, high dielectric powder such as barium titanate) and Phosphor (
For example, a phosphor made of zinc sulfide activated with copper) dispersed in an organic binder (for example, cyanoethyl cellulose) is sequentially applied to form an insulating layer 4 and a light emitting layer 5, and a current collecting band is placed on top of these. A transparent electrode 6 made of a printed transparent conductive film or the like is provided, and an electroluminescent element 9 formed by covering with a moisture-absorbing film (for example, nylon 6 (trademark of DuPont) 7, 7 from above and below) is further covered with a waterproof outer film (for example, from above and below). It has a structure that is hermetically sealed with fluorine-based films (fluorine-based films) 8, 8.Leads are connected to the back electrode 3 and the transparent electrode 6, respectively, and led out to the outside.

In the electroluminescent lamp having the above structure, the insulating layer is a high dielectric layer for effectively applying an electric field to the light emitting layer, and also serves as a reflective layer for efficiently reflecting light emitted. However, the barium titanate used has a large particle size of 1 to 2 μm and has large variations, resulting in poor reflectance and difficulty in achieving high brightness.

In order to solve the above problem of =, it is desirable to make the high dielectric powder constituting the insulating layer have a particle size Dopt that maximizes the scattering power expressed by the following formula with respect to the emission peak wavelength. It is characterized by

However, it is not realistic to make the particle sizes of the high dielectric powders exactly the same. Therefore, it is characterized in that the emission spectrum is distributed between the maximum and minimum values determined by applying the maximum wavelength and minimum wavelength of the emission spectrum to the following equation.

"pt" 1.414 yr no M λ: Wavelength of light no = refractive index of binder M = L orentz - L orentz coefficient n
, , = refractive index of high dielectric powder 1. According to the above configuration, the scattering power is maximized, that is, the reflectance is improved, and the luminance φ efficiency is improved.

This is because the greater the scattering power, the shorter the distance that light travels within the coating film, so there is less opportunity for light to be attenuated within the coating film, which increases the hiding power and increases the reflectance.

In addition, since barium titanate is uniform fine particles, it is possible to increase the filling rate, improve the dielectric constant of the insulating layer,
An effective electric field can be applied to the light emitting layer.

The scattering coefficient of a pigment with a uniform particle size in a binder is generally expressed as follows. (Coloring Materials Association Magazine Vol. 37 P5-P9) Here, K: proportionality constant 2 particle diameter λ: previous wavelength no: refractive index of binder M: L orentz - L orentz coefficient n
,: Pigment refractive index In the case of an electroluminescent lamp, the insulating layer and the light emitting layer are in contact, and the total output light is expressed as the sum of the direct light and the reflected light, and the reflected light is l) F at the surface of the insulating layer. Light that is reflected according to Resnel's law; 2) Light that is reflected on the surface of the insulating material in the insulating layer and exits; 3) Light that passes through the insulating layer, is reflected by the base material, passes through the coating again, and exits to the outside. In order to maximize this reflected light, the light absorbed by the binder in the insulating layer and the light absorbed by the substrate, or the light reflected by the substrate and absorbed by the binder, should be maximized. Bye. That is, the larger the scattering coefficient of the insulating layer, the shorter the distance through which light passes, and the amount of absorbed light can be suppressed. Therefore, in equation (1), the optimum particle size for maximizing the scattering coefficient is expressed as follows.

Here, the peak wavelength of the insulated light-emitting electroluminescent lamp is 510 n
a+, and the refractive index of the binder no ==l, 5 *
When the refractive index of barium titanate is n si ” 3.0, the optimum particle size is Dopt =0.15.czm, and the scattering coefficient 81 at that time is 58.8.

In addition, conventional barium titanate has large particles of 1 to 2 μm and has large variations, but the scattering coefficient 82 when the particle size is distributed from D2 to D2 is calculated by the following formula, and the above value λ = 510 nm, no :1.5+
Substituting np=3.0, S2 becomes 22. OK.

That is, it can be seen that the insulation used in the electroluminescent lamp according to the present invention has a scattering coefficient 2.87 times larger than that of the conventional product. Next, Table 1 shows the reflectance of the insulating layer using these barium titanates. Further, FIG. 1 shows the brightness-voltage characteristics of the electroluminescent lamp according to the present invention. Note that the dotted line indicates the characteristics of a conventional electroluminescent lamp.

Table 1 As described above, by using barium titanate as an insulating layer with a particle size that is optimal depending on the emission wavelength, the reflectance can be improved and the brightness of the electroluminescent lamp can be improved.

Next, as another example, Table 2 shows a list of optimum particle sizes for each emission wavelength.

front, ma However, np = 3.0 no=1.5 shall be.

As explained above, according to the present invention, the particle size of the high dielectric powder used in the insulating layer, which is a high dielectric and white reflective layer, is optimized according to the emission wavelength, thereby reducing the light emission. By suppressing the amount of light, the reflectance improves, and the brightness of the electroluminescent lamp can be increased without increasing power consumption, making it possible to achieve high brightness and high efficiency.

[Brief explanation of the drawing]

FIG. 1 shows the brightness-voltage characteristics of an electroluminescent lamp according to the invention. FIG. 2 is an enlarged sectional view of a conventional electroluminescent lamp. Figure 2 8 - Wandering Philbe 9, - Mowing - 4 hills

Claims (1)

[Scope of Claims] In an electroluminescent lamp in which an insulating layer and a light emitting layer are sandwiched between a back electrode and a transparent electrode, the insulating layer is formed by dispersing high dielectric powder in a binder, wherein the particle size of the high dielectric powder is An electroluminescent lamp characterized in that the distribution is between a maximum value and a minimum value determined by the following formula. Maximum value = ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Minimum value = ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Where, λ1: Maximum wavelength in the spectral distribution of the electroluminescent lamp λ2: Maximum wavelength in the spectral distribution of the electroluminescent lamp Minimum wavelength n_o: refractive index of the binder n_p: refractive index of the high dielectric powder