JP5647841B2 - Dispersion type EL device manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a dispersive electroluminescence (hereinafter referred to as dispersive EL) element.

  As shown in FIG. 7, a dispersion type EL element 110 conventionally known as a surface-emitting light source has a transparent electrode 102 made of ITO (indium oxide) or the like on one side of a base film 101 made of polyethylene terephthalate or the like, A light emitting layer 103 in which phosphor fine powder 103B is dispersed in a binder 103A, a dielectric layer 104 in which dielectric fine powder 104B is dispersed in a binder 104A, and a back electrode 105 made of aluminum or the like are sequentially laminated. Configured.

  In order to improve the light emission luminance and efficiency of the dispersion type EL element, an electric field applied to the light emitting layer 103 is increased by using a material having a high dielectric constant as the binder 104A or the dielectric fine powder 104B of the dielectric layer 104 to increase its capacity. It is known to increase. Further, the light emitting layer 103 is also devised to increase the electric field applied to the phosphor fine powder 103B by using fluororubber, cyanocellulose or the like having a high dielectric constant for the binder 103A.

However, even if a binder having a high dielectric constant is selected, the relative dielectric constant is about 15 at most, which is one to two orders of magnitude smaller than that of an oxide-based high dielectric material. In addition, a resin having a high dielectric constant has a disadvantage that the dielectric loss (so-called tan δ) is large and leads to power loss.

To solve such problems, as a binder 103A of Patent Document 1, the light-emitting layer 103, but the dielectric constant is small with a resin that is low in dielectric loss, at the same time a high dielectric powder 103C as shown in FIG. 7 It has been proposed to be distributed.

JP-A-6-267657

However, as described in paragraph [0031] of Patent Document 1, the high dielectric fine powder 103C is opaque to light, and the light emitting layer is dispersed by dispersing a powder having a particle size on the order of 1 μm. The light transmittance of the light-emitting element 103 is reduced, and the light emission intensity of the dispersion-type EL element 110 is not increased as expected.

In order to prevent a decrease in light transmittance, it is conceivable to reduce the particle size of the high dielectric fine powder 103C to about 100 nm or less. However, when the particle size becomes ultrafine particles of this order, the particles are aggregated to form a binder. There was a problem that it was difficult to disperse uniformly in 103A.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method of manufacturing a dispersion type EL element in which high dielectric ultrafine particles are uniformly dispersed in a light emitting layer.

Generally, a dispersion type EL device has a transparent electrode, a light emitting layer in which fine phosphor powder and high dielectric ultrafine particles are dispersed in a binder, and a fine dielectric powder dispersed in a binder on a base film. The dielectric layer thus formed and a back electrode are laminated. In the method for manufacturing a dispersion-type EL element according to the present invention, the process of forming the light emitting layer includes a step of preparing a dispersion in which the high dielectric ultrafine particles are dispersed in an organic medium, and the dispersion and the phosphor fine particles. It comprises a step of obtaining a paint in which powder is dispersed and mixed in a binder, and a step of applying the paint in a uniform thickness on the transparent electrode formed on the base film.

In the above-described configuration, in the first step of forming the light emitting layer, a dispersion liquid in which high dielectric ultrafine particles are dispersed in an organic medium is prepared in advance, and this dispersion liquid is mixed with a phosphor fine powder in a binder. Yes. For this reason, nanometer-order high dielectric ultrafine particles are uniformly dispersed in the binder without aggregation.

Here, in order to improve the dispersibility, the high dielectric ultrafine particles may be subjected to a surface treatment having an affinity for the organic medium. In consideration of the adhesion of the light emitting layer, the volume ratio of the high dielectric ultrafine particles in the binder is preferably 0.5 or less. In consideration of the light transmittance, the high dielectric ultrafine particles preferably have a particle size of 100 nm or less. In particular, ultrafine particles of titanium oxide or zirconium oxide are preferable because they are easily available.

It is also possible to form a dielectric layer in which high dielectric ultrafine particles are uniformly dispersed in a binder by the same process as that for the light emitting layer. In this case, considering the adhesion of the dielectric layer, the volume ratio of the high dielectric ultrafine particles in the binder is preferably 0.8 or less.

According to the present invention, the light transmittance of the light emitting layer is improved and the scattering is small as compared with the conventional light emitting layer in which high dielectric fine powder of micrometer order is dispersed, which contributes to the improvement of the light emission efficiency. be able to.

It is principal part sectional drawing of the dispersion type EL element which concerns on one Embodiment of this invention. It is a flowchart of each process of forming the light emitting layer of a dispersion-type EL element. 4 is a graph showing the light transmittance of the light emitting layer of the dispersion type EL device according to Example 1 in relation to the volume ratio of titanium oxide ultrafine particles to the binder. 6 is a graph showing the light emission efficiency of the dispersive EL element according to Example 1 in relation to the voltage value of the drive voltage. It is a graph which shows the light transmittance of the light emitting layer of the dispersion-type EL element which concerns on Example 2 by the relationship with the volume ratio with respect to the binder of a zirconium oxide ultrafine particle. It is principal part sectional drawing of the dispersion type EL element which concerns on other embodiment of this invention. It is principal part sectional drawing of the dispersion type EL element which concerns on a prior art example.

  With reference to FIG. 1, a schematic configuration of a dispersion type EL element according to the first embodiment of the present invention will be described. The dispersive EL element 10 shown in FIG. 1 has the same basic structure as that of the conventional dispersive EL shown in FIG. 7, and on one side of the base film 1, a transparent electrode 2, a light emitting layer 3, and a dielectric layer. 4 and the back electrode 5 are laminated. Note that the outer surface of the dispersion type EL element 10 may be sealed with a protective coat (see Patent Document 1).

  As the base film 1, any resin film having low moisture permeability and hygroscopicity can be used. However, since the heat resistance is good, a heat resistant resin film such as polyethylene terephthalate is particularly suitable. As for the film thickness, a film thickness of 0.30 mm or less is particularly preferable in order to improve the flexibility of the planar light emitter.

  The transparent electrode 2 is formed by depositing a transparent conductor such as ITO on one side of the base film 1, for example, by sputtering.

The light emitting layer 3 is formed by uniformly dispersing phosphor fine powder 3B and high dielectric ultrafine particles 3C in a binder 3A made of a crosslinkable resin.

  As a material constituting the binder 3A, a crosslinkable resin, such as a fluororubber resin, an acrylic resin, a urethane resin, a silicon resin, an epoxy resin, an acrylic silicon resin, an acrylic epoxy resin, a butyral resin, A resin material that is crosslinked by heat or a curing agent, such as a phenol resin, is used.

  Further, as the phosphor fine powder 3B, a fine powder of any phosphor that is publicly known can be used. However, since strong emission intensity can be obtained, etc., those obtained by adding copper and chlorine to zinc sulfide, etc. Is particularly preferred. The mixing ratio of the phosphor fine powder 3B to the binder 3A is particularly preferably about 1 or more, more preferably about 2 in volume ratio.

Furthermore, as the high dielectric ultrafine particles 3C, any high dielectric ultrafine particles that are publicly known can be used. However, since the dielectric constant is high, titanium oxide, zirconium oxide, yttrium oxide, barium titanate, or titanic acid is used. Ultrafine particles of metal oxide such as barium zirconate are particularly suitable. A preferable mixing ratio of the high dielectric ultrafine particles 3C to the binder 3A will be described later.

The upper limit of the particle size of the high dielectric ultrafine particles 3C is said to be about 100 nm, which is the limit size that can be seen with an optical microscope. It can be considered that there is almost no effect on sex. In addition, light scattering by particles is handled by the Rayleigh scattering theory. According to the theory, light having a wavelength shorter than a certain wavelength is almost scattered backward. The conditions under which Rayleigh scattering occurs are λ / π << D, where the wavelength is λ and the particle size is D, so the particle size D at which the short wavelength end of visible light is 400 nm and no scattering occurs is about 130 nm or less. The upper limit value is also within this range, which is preferable.

As shown in FIG. 2, the formation process of the light emitting layer 3 mainly includes a step of preparing a dispersion liquid in which high dielectric ultrafine particles 3C are dispersed in an organic medium (step S1), a dispersion liquid and a phosphor fine powder. It comprises a step of obtaining a paint in which 3B is dispersed and mixed in a binder 3A (step S2) and a step of applying the paint to the transparent electrode 2 formed on the base film 1 with a uniform thickness (step S3). The

In step S1, as the dispersion medium for the high dielectric ultrafine particles 3C, any known organic solvent can be used, but hydrophilic methyl ethyl ketone and methanol are preferable.

The high dielectric ultrafine particles 3C are particles having a size of 100 nm or less as described above, and the force of aggregating between such nanometer-sized particles works, so that it is difficult to disperse them as they are. . Therefore, it is preferable to mix with a dispersion medium after performing an appropriate surface treatment. Specifically, since the high dielectric ultrafine particle 3C is made of a metal oxide that is an inorganic material as described above, a silane coupling agent or the like is used as a surface treatment agent in order to increase affinity with the organic medium. A surface modification treatment is performed using a surfactant. These treatment agents have a hydrophilic group and an organic functional group. When the hydrophilic group is bonded to a metal oxide, a surface state having an affinity with an organic medium, which is an organic substance, is realized in the inorganic material.

  As methods for modifying the surface of an inorganic material with a surface treatment agent, a wet method and a dry method are known. In the wet method, an inorganic material is dispersed in a medium, and a surface treatment agent such as a silane coupling agent or a surfactant is diluted with water or an organic medium and added to the inorganic material while stirring vigorously. In the dry method, the surface treatment agent is sprayed at a high speed to stir the inorganic material and adhere to the surface.

  When the surface-treated metal oxide ultrafine particles are dispersed in the organic medium, they are dispersed in the medium in a uniform and non-aggregated state by the action of the organic functional group. At this time, an additive (dispersant) for further enhancing the affinity of the surface-treated metal oxide particles to the medium may be added to the medium.

  Next, in step S2, the dispersion prepared as described above is mixed with phosphor fine powder 3B together with binder 3A dissolved in a solvent, and subjected to treatments such as viscosity adjustment and defoaming to obtain a paste. Make a paint.

The mixing ratio of the high dielectric ultrafine particles 3C is suitably 0.1 to 1 as a volume ratio with respect to the binder 3A. The mixing ratio of the phosphor fine powder 3B is suitably 2 to 5 in terms of the weight ratio with respect to the binder 3A and the high dielectric ultrafine particles 3C.

  In step S3, the coating layer obtained as described above is subjected to, for example, screen printing on the transparent electrode 2 formed on the base film 1, thereby forming the light emitting layer 3 with a uniform thickness. The

The dielectric layer 4 is formed by uniformly dispersing high dielectric fine powder 4B in a binder 4A. The dielectric layer 4 is formed to have a uniform thickness by, for example, screen printing or the like on the light emitting layer 3 with a coating obtained by dispersing and mixing the high dielectric fine powder 4B in a binder 4A dissolved in a solvent. Is done.

As the high dielectric fine powder 4B, the same kind of high dielectric ultrafine particles 3C mixed in the light emitting layer 3 can be used, and as the material of the binder 4A, the binder 3A of the light emitting layer 3 described above can be used. The same kind of material can be used.

  The back electrode 5 is formed by vacuum-depositing a conductive metal material such as aluminum on the dielectric layer 4. Alternatively, a conductive paste such as a silver paste can be screen-printed.

In the present embodiment, in the first step of forming the light emitting layer, a dispersion liquid in which high dielectric ultrafine particles are dispersed in an organic medium is prepared in advance, and this dispersion liquid is mixed with a phosphor fine powder in a binder. Yes. For this reason, it has become possible to form a light emitting layer uniformly dispersed in a binder without aggregation of nanometer-order high dielectric ultrafine particles. As a result, the light transmittance of the light-emitting layer is improved and the scattering is small compared to the conventional light-emitting layer in which high- dielectric fine powder of micrometer order is dispersed, which can contribute to the improvement of the light emission efficiency. .

  Hereinafter, examples of the dispersion-type EL element according to the present embodiment will be listed to clarify the effects of the method for manufacturing the dispersion-type EL element of the present invention.

<Example 1>
Rutile-type titanium oxide ultrafine particles having a central particle diameter of about 10 nm were previously dispersed in methyl ethyl ketone. At this time, surface treatment, addition of a dispersant, and the like were performed so as not to cause aggregation of particles, and an almost transparent dispersion liquid was prepared.

  Next, this dispersion and phosphor powder (product name: GG25, manufactured by OSRAM Sylvania Co., Ltd.) are mixed with a fluororubber binder dissolved in a solvent and subjected to treatments such as viscosity adjustment and defoaming. A paint was obtained. Using the obtained paint, a dispersion type EL element 10 as shown in FIG. 1 was produced by a conventional method. The film thickness of the light emitting layer 3 is 50 μm.

  Using the dispersion-type EL element of Example 1, the light transmittance of the light emitting layer with respect to visible light was measured. The result is shown in FIG. The measurement was performed by changing the volume ratio of titanium oxide to the binder. As shown in FIG. 3, as the particle size of titanium oxide is smaller, there is a tendency that the light transmittance is less likely to decrease even if the mixing rate of titanium oxide is increased. From this result, the particle size of titanium oxide is preferably 50 nm or less, and more preferably 10 nm or less.

  In addition, four samples of the dispersion type EL element of Example 1 having different mixing ratios of the ultrafine titanium oxide particles (volume ratios of 0, 0.15, 0.4, and 0.5 with respect to the binder) were prepared, and luminous efficiency was prepared. Was measured. The result is shown in FIG. Measurement was performed by changing the voltage at a frequency of 2 kHz with a sine wave drive for each sample. As shown in FIG. 4, it can be seen that the effect of improving the light emission efficiency can be obtained by uniformly dispersing the ultrafine titanium oxide particles in the binder of the light emitting layer. The effect appears when the mixing ratio of titanium oxide is 0.1 or more in volume ratio, and saturates at about 0.5. Note that it is not preferable to increase the mixing ratio of titanium oxide beyond this, because it impedes the light transmittance and adhesion of the light emitting layer.

<Example 2>
In Example 1, in the process of forming the light emitting layer 3, the same procedure as in Example 1 was used, except that a dispersion in which zirconium oxide ultrafine particles having a central particle diameter of about 20 nm were previously dispersed in methanol was used instead of titanium oxide ultrafine particles. A dispersion type EL element 10 as shown in FIG.

  Then, four samples (dispersion volume ratios of 0, 0.15, 0.2, and 0.4 with respect to the binder) of the dispersion type EL element of Example 2 having different mixing rates of the zirconium oxide ultrafine particles were prepared, and the luminous efficiency Was measured. The result is shown in FIG. Measurement was performed by changing the voltage at a frequency of 2 kHz with a sine wave drive for each sample. As shown in FIG. 5, when the ultrafine zirconium oxide particles were uniformly dispersed in the binder of the light emitting layer, there was an effect of improving the light emission efficiency. As for the mixing ratio of zirconium oxide ultrafine particles, an effect close to the maximum appears at a volume ratio of about 0.15, and the effect is almost constant up to about 0.4. A volume ratio exceeding 0.5 is not preferable because the adhesiveness of the light emitting layer starts to decrease.

Next, the configuration of a distributed EL element according to another embodiment of the present invention will be described with reference to FIG. In the dispersion-type EL element 20 according to the embodiment shown in FIG. 6, in the dispersion-type EL element 10 (see FIG. 1) according to the above-described embodiment, as the dielectric layer 4 ′, high dielectric ultrafine particles in the binder 4A. 4C is uniformly dispersed. Other configurations of the dispersion-type EL element 20 according to the present embodiment are the same as those of the dispersion-type EL element 10 according to the above-described embodiment. The dielectric layer 4 ′ can be formed basically in the same process as the process of forming the light emitting layer 3 except that the phosphor fine powder is not added in step S2 of FIG.

The high dielectric ultrafine particles 4C can basically use the same material as the high dielectric ultrafine particles 3C, and the mixing ratio can be increased to about 0.8 in volume ratio to the binder 4A. It is not preferable to increase the mixing ratio of the high dielectric ultrafine particles 4C beyond this because the adhesion of the dielectric layer 4 will be hindered.

  According to the dispersion-type EL element 20 according to the present embodiment, the effect of making the dielectric constant of the dielectric layer 4 ′ uniform is exhibited, which contributes to further improving the light emission efficiency of the dispersion-type EL element.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1-base film 2-transparent electrode 3-light emitting layer 3A-binder 3B-phosphor fine powder 3C- high dielectric ultrafine particle 4A-binder 4B- high dielectric fine powder 4C- high dielectric ultrafine particle 4, 4'- Dielectric layer 5-Back electrode 10, 20-Dispersion type EL element

Claims (6)

On the base film, a transparent electrode, a light emitting layer in which phosphor fine powder and ferroelectric ultrafine particles are dispersed in a binder, a dielectric layer in which dielectric fine powder is dispersed in a binder, and a back electrode In the manufacturing method of the dispersion type EL element constituted by laminating
The ferroelectric ultrafine particles are zirconium oxide ultrafine particles,
The light emitting layer includes a step of preparing a dispersion in which the ferroelectric ultrafine particles are dispersed in an organic medium, a step of obtaining a paint in which the dispersion and the fine phosphor powder are dispersed and mixed in a binder, and the paint. And a step of coating the transparent electrode formed on the base film with a uniform thickness. 2. The method for manufacturing a dispersion type EL element according to claim 1 , wherein a mixing ratio of the ferroelectric ultrafine particles is 0.2 or less in a volume ratio with respect to the binder. The ferroelectric ultrafine particles, method for producing a dispersion-type EL element according to claim 1 or 2, characterized in that the surface treatment to have an affinity for organic medium is applied.   The dielectric layer comprises a step of obtaining a dispersion in which ferroelectric ultrafine particles are dispersed in a medium, and a step of obtaining a paint in which the dispersion is dispersed and mixed in a binder. It forms by apply | coating with uniform thickness on the top, The manufacturing method of the dispersion type EL element in any one of Claims 1-3 characterized by the above-mentioned.   5. The method for manufacturing a dispersion-type EL element according to claim 1, wherein a mixing ratio of the ferroelectric ultrafine particles in the dielectric layer is 0.8 or less in terms of a volume ratio to a binder. .   6. The method of manufacturing a dispersion type EL element according to claim 1, wherein the ferroelectric ultrafine particles have a particle size of 100 nm or less.

Images