JP5054464B2 - Organic EL light emitting device - Google Patents

Description

  The present invention relates to an organic EL light emitting device used for a liquid crystal backlight, a lighting fixture, various displays, a display device, and the like.

  As a typical surface light emitter, there is an organic electroluminescence element (organic EL light emitting element). As shown in FIG. 1A, this organic EL light-emitting element is provided with a translucent electrode 3 on a translucent substrate 1 and an organic EL material made of an organic EL material on the translucent electrode 3. The light-emitting layer 2 is provided, and the light-reflective counter electrode 10 is provided on the organic light-emitting layer 2. The light emitted from the organic light emitting layer 2 by applying a voltage between the translucent electrode 3 and the counter electrode 10 is extracted through the translucent electrode 3 and the translucent substrate 1.

  Thus, when the light emitted from the organic light emitting layer 2 is extracted outside through the translucent electrode 3 and the translucent substrate 1, the light is totally reflected at the interface between the translucent electrode 3 and the translucent substrate 1, The light extraction efficiency decreases. For this purpose, as shown in FIG. 1A, a light scattering layer 5 is formed between the light transmitting electrode 3 and the light transmitting substrate 1, and light is scattered by the light scattering layer 5. The occurrence of total reflection at the interface between the electrode 3 and the translucent substrate 1 is reduced to increase the light extraction efficiency.

This light scattering layer 5 is provided with fine irregularities on the surface of the translucent substrate 1 on the translucent electrode 3 side, or a coating resin layer containing particles is formed on the translucent electrode 3 of the translucent substrate 1. However, in any case, the surface of the light scattering layer 5 becomes uneven, and the thin transparent electrode 3 cannot be formed with a uniform thickness. For this reason, as shown in FIG. 1A, a relaxation layer 11 is formed on the surface of the light scattering layer 5 to smooth the unevenness by smoothing the unevenness, and a thin transparent electrode is formed on the smooth surface of the relaxation layer 11. 3 is formed with a uniform thickness (see, for example, Patent Document 1).
JP 2006-286616 A

  As described above, the light extraction layer 4 including the light scattering layer 5 and the relaxation layer 11 is formed between the light transmissive substrate 1 and the light transmissive electrode 3, and the light emitted from the organic light emitting layer 2 is emitted from the light extraction layer 4. The directivity of light is changed by being scattered by the light scattering layer 5, and the total reflection of light at the interface between the translucent electrode 3 and the translucent substrate 1 is suppressed, thereby improving the light extraction efficiency. It is what.

  However, when light is scattered by the light scattering layer 5 of the light extraction layer 4 in this manner, the light extraction in the oblique direction is improved, but the light extraction to the front is reduced, and the light extraction efficiency is reduced. There was a problem that could not be raised sufficiently.

  The present invention has been made in view of the above points, and an organic EL that can extract light with high efficiency by increasing the efficiency of extracting light in an oblique direction while suppressing reduction of front extraction light. The object is to provide a light-emitting element.

  The organic EL light emitting device according to the present invention includes a translucent electrode 3 between the translucent substrate 1 and the organic light emitting layer 2 and provides light directivity between the substrate 1 and the translucent electrode 3. In an organic EL light-emitting device including a light extraction layer 4 to be changed and configured to extract light emitted from the organic light emitting layer 2 from the light extraction layer 4 and the light transmitting electrode 3 through the light transmitting substrate 1. 4 is formed with a light scattering layer 5. The light scattering layer 5 is made of a binder resin containing light scattering particles, and when the intensity of light incident and emitted from the front is measured, The emission angle of light that is 1/100 of the intensity of the light emitted from the light source is 3 to 45 °.

  According to the present invention, when the light emitted from the organic light emitting layer 2 is incident on the light scattering layer 5 of the light extraction layer 4, scattered by the light scattering particles and emitted from the light scattering layer 5, the light is extracted from the substrate 1. The light scattering layer 5 has an emission angle of 3 to 45 ° that is 1/100 of the intensity of the light emitted to the front, so that the oblique direction is suppressed while suppressing the reduction of the light extracted to the front. The light extraction efficiency can be improved and light can be extracted with high efficiency.

  In the present invention, the light scattering particle has a particle size of 0.3 to 10 μm, and a difference in refractive index between the light scattering particle and the binder resin is 0.001 to 0.1. It is.

  By adjusting the particle size of the light scattering particles and the difference in refractive index between the light scattering particles and the binder resin within this range, the emission angle of light that becomes 1/100 the intensity of the light emitted to the front surface can be obtained. The light scattering layer 5 can be formed to be 3 to 45 °, and light can be extracted with high efficiency.

  In the present invention, the volume ratio of the light scattering particles in the light scattering layer 5 is 90% or more, and the average number of light scattering particles in the thickness direction of the light scattering layer 5 is 1 to 10. It is characterized by this.

  By adjusting the volume ratio of the light scattering particles and the average number of particles in the light scattering layer 5 within this range, the emission angle of light that becomes 1/100 the intensity of the light emitted to the front is 3 to 3. The light scattering layer 5 can be formed to be 45 °, and light can be extracted with high efficiency.

  The present invention further includes a buffer layer 11 for smoothing the irregularities on the surface of the light scattering layer 5 between the light scattering layer 5 and the translucent electrode 3, and the light extraction layer 4 is connected to the light scattering layer 5. It is formed from the buffer layer 11.

  According to the present invention, the unevenness of the light scattering layer 5 is filled with the relaxation layer 11, and the electrode 3 can be formed with a uniform film thickness on the smooth surface of the relaxation layer 11, thereby improving the reliability of the device. It is something that can be done.

  According to the present invention, when the light emitted from the organic light emitting layer 2 is incident on the light scattering layer 5 of the light extraction layer 4, scattered by the light scattering particles and emitted from the light scattering layer 5, the light is extracted from the substrate 1. The light scattering layer 5 has an emission angle of 3 to 45 ° that is 1/100 of the intensity of the light emitted to the front, so that the oblique direction is suppressed while suppressing the reduction of the light extracted to the front. The light extraction efficiency can be improved and light can be extracted with high efficiency.

  Hereinafter, the best mode for carrying out the present invention will be described.

  An example of the layer structure of the organic EL light emitting device according to the present invention is shown in FIG. The light scattering layer 5 and the relaxation layer 11 are laminated in this order on one surface of the translucent substrate 1, and the light extraction layer 4 that is extracted by changing the light directivity between the light scattering layer 5 and the relaxation layer 11. It is formed. A translucent electrode 3 is formed on the surface of the relaxation layer 11 opposite to the light scattering layer 5, and the organic light emitting layer 2 is laminated on the surface of the electrode 3 opposite to the relaxation layer 11. If necessary, a hole injection layer and a hole transport layer are laminated on the electrode 3 side of the organic light emitting layer 2, and an electron transport layer and an electron are provided on the side opposite to the electrode 3 of the organic light emitting layer 2 as necessary. An injection layer is laminated. An organic EL light emitting element can be formed by stacking and providing an electrode 10 serving as a counter electrode on the opposite side of the organic light emitting layer 2 from the translucent electrode 3.

  As said translucent board | substrate 1, if it permeate | transmits light, it can use without a restriction | limiting especially, For example, rigid transparent glass plates, such as soda glass and an alkali free glass, polycarbonate Arbitrary things, such as flexible transparent plastic plates, such as polyethylene terephthalate, can be used.

  The light scattering layer 5 provided on the surface of the substrate 1 can be formed by applying a coating material made of light scattering particles and a binder resin to form a film.

Transparent particles are used as the light scattering particles. For example, TiO ₂ , SiO ₂ , ZrO ₂ , Al ₂ O ₃ , Ta ₂ O ₃ , ZnO ₂ , Sb ₂ O ₃ , ZrSiO ₄ , zeolite, or their Examples thereof include porous substances and inorganic particles mainly composed of them, or organic particles such as polyimide resin, acrylic resin, styrene resin, polyethylene terephthalate resin, silicone resin, and fluoride resin.

  As binder resin, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin, polyurethane, acrylic resin, polyacrylonitrile, polyvinyl acetal, polyamide, polyimide, diacrylphthalate resin, Examples thereof include cellulosic resins, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and copolymers of two or more monomers constituting these resins. Further, a silicone resin obtained by reacting a silicate alkoxide, or a porous silica made of polysiloxane can be used. This polysiloxane is obtained by condensation polymerization of an alkoxysilane such as tetraethoxysilane or a partial hydrolyzate thereof.

Moreover, the light-scattering layer 5 can also be formed using two types of light-scattering particles having different refractive indexes. That is, assuming that the refractive index of the binder resin is Nb, one of the two types of light scattering particles is Nf ₁ , and the other refractive index is Nf ₂ , so that the relationship Nf ₂ >Nb> Nf ₁ is satisfied. A binder resin and two types of light scattering particles are selected and used. The light scattering layer 5 composed of the binder resin having the refractive index having such a relationship and the two kinds of light scattering particles has a light scattering effect amplified by the difference between the refractive indexes. Is formed on the surface of the light-transmitting substrate 1, the critical angle at the interface between the light scattering layer 5 and the substrate 1 is disturbed, and the light transmission to the substrate 1 is increased, and the light extraction efficiency is increased. Will be higher.

The refractive index Nb of the binder resin is generally in the range of 1.45 to 1.60, and the refractive indexes Nf ₁ and Nf ₂ of the light scattering particles are generally in the range of 1.2 to 2.5. Of the scattering particles, one of the light scattering particles preferably has a refractive index Nf ₁ of 1.4 or less. The lower limit of the refractive index Nf ₁ is not particularly limited, but is generally about 1.2. As described above, when the refractive index Nf ₁ of one of the fine particles is 1.4 or less, the refractive index of the light scattering layer 5 is greatly reduced, and the light scattering layer 5 having a high light scattering property and a low refractive index is obtained. It can be formed. In this case, the difference between the refractive indexes Nf ₁ and Nf ₂ of the two types of light scattering particles is preferably 0.5 or more. When the two kinds of light scattering particles have a refractive index difference of 0.5 or more, the light scattering intensity of the light scattering layer 5 is increased, and as a result, the light extraction efficiency is further improved. The upper limit of the refractive index difference between the two types of light scattering particles is not particularly limited, but is generally preferably about 1.3 or less. The ratio of the two types of light scattering particles is not particularly limited, but it is preferable to mix a material having a small refractive index Nf _{1 and} a material having a large refractive index Nf ₂ at a mass ratio of 1: 9 to 9: 1. preferable.

  The coating material obtained by blending the light scattering particles with the binder resin is coated on the surface of the substrate 1 by spin coating, dip coating, die coating, casting, spray coating, gravure coating, etc. The scattering layer 5 can be formed.

  The film thickness of the light scattering layer 5 is not particularly limited, but a range of about 0.1 to 20 μm is preferable. In many cases, the refractive index of the light scattering layer 5 is in the range of 1.30 to 1.70, but is preferably set so as to be equal to or smaller than the refractive index of the translucent substrate 1. . As described above, when the refractive index of the light scattering layer 5 is equal to or less than the refractive index of the substrate 1, it is possible to reduce the total reflection of the light incident on the substrate 1 from the light scattering layer 5. The efficiency of taking out outside becomes larger. Furthermore, it is preferable that the light scattering layer 5 has a haze value ((diffuse transmittance / total transmittance) × 100) in the range of 2-50. By setting the haze value of the light scattering layer 5 within this range, it is possible to improve the light extraction efficiency. In the case of a film having a high haze value, even if the light extraction efficiency is improved, the film may be whitened to deteriorate the appearance.

  On the surface of the light scattering layer 5 formed as described above, unevenness is caused by the light scattering particles exposed on the surface of the light scattering layer 5. For this reason, when the translucent electrode 3 is formed directly on the surface of the light scattering layer 5, the electrode 3 is formed in a shape following the unevenness because the film thickness is thin, or the film thickness becomes uneven. There is a risk of problems in electrical characteristics or short circuits. Therefore, by forming the relaxation layer 11 on the surface of the light scattering layer 5 opposite to the base material 1 and filling the unevenness of the light scattering layer 5 with the relaxation layer 11, the smooth surface of the relaxation layer 11 is uniform. The electrode 3 can be formed with a sufficient thickness.

  This relaxation layer 11 can be formed of a resin coating layer. The material of the coating resin is not particularly limited as long as it has optical transparency, and any material can be used, for example, polyester, polyether, polyether ketone, polyimide, polyamide. , Polyimide amide, epoxy, polyurethane, polyurethane acrylate, polycarbonate and the like. Among these, it is preferable to use thermosetting resins such as polyimide, polyamideimide, epoxy, and polyurethane. And after coating this coating resin on the surface of the light-scattering layer 5, the relaxation layer 11 can be formed by heating and hardening. Although the film thickness of the relaxation layer 11 is not specifically limited, The range of about 1-20 micrometers is preferable.

  The refractive index of the resin forming the relaxation layer 11 is such that the total reflection at the interface between the translucent electrode 3 and the relaxation layer 11 is reduced and more light is guided to the light scattering layer 5. Even when the refractive index is higher or lower than the refractive index of the electrode 3, it is desirable that the difference is small. Furthermore, the difference in refractive index of the resin forming the relaxation layer 11 is desirably small even when it is lower than the refractive index of the light scattering layer 5 or higher than the refractive index of the light scattering layer 5. Ideally, the refractive index in the relaxation layer 11 is inclined so as to gradually increase or decrease from the electrode 3 side to the light scattering layer 5 side, and at the interface with the electrode 3, the relaxation layer 11. Is preferably substantially the same as the refractive index of the electrode 3, and the refractive index of the relaxation layer 11 is preferably substantially the same as the refractive index of the light scattering layer 5 at the interface with the light scattering layer 5. In this case, there is no optical interface having a different refractive index between the relaxing layer 11 and the electrode 3 or the light scattering layer 5, and the total reflection loss at the interface can be eliminated.

  After providing the relaxation layer 11 on the surface of the light scattering layer 5 as described above, the translucent electrode 3 is formed on the surface of the relaxation layer 11 opposite to the light scattering layer 5. As the material of the translucent electrode 3, any material can be used as long as the effect of the present invention is not hindered. For example, indium-tin oxide (ITO), indium-zinc oxide (IZO), Tin oxide, ultrathin metal such as Au, conductive polymer, conductive organic material, organic layer containing dopant (donor or acceptor), mixture of conductor and conductive organic material (including polymer), or these And the like. The electrode 3 can be formed by forming a film of these materials using a vapor phase growth method such as a sputtering method or an ion plating method. The thickness of the electrode 3 is not particularly limited, but is preferably about 50 to 300 nm.

  Next, after providing the translucent electrode 3 on the surface of the relaxation layer 11 as described above, the organic light emitting layer 2 is formed on the surface of the electrode 3 opposite to the relaxation layer 11. Examples of the organic EL material that forms the organic light emitting layer 2 include anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, and bisstyryl. , Cyclopentadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-Phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, pyran, quinacridone A molecule comprising rubrene and derivatives thereof, or 1-aryl-2,5-di (2-thienyl) pyrrole derivative, distyrylbenzene derivative, styrylarylene derivative, styrylamine derivative, and a group composed of these luminescent compounds. Or a polymer or the like contained in a part of the above. Further, not only compounds derived from fluorescent dyes typified by the above compounds, but also so-called phosphorescent materials, for example, luminescent materials such as Ir complexes, Os complexes, Pt complexes, and europium complexes, or compounds or polymers having these in the molecule It can be used suitably. These materials can be appropriately selected and used as necessary.

Then, by providing the light-reflective counter electrode 10 on the opposite side of the organic light-emitting layer 2 from the light-transmitting electrode 3, the organic EL light-emitting element having the layer structure of FIG. 1A can be formed. . As the material of the electrode 10, Al or the like can be used. However, a layered structure or the like may be configured by combining Al and another electrode material. Such electrode material combinations include alkali metal and Al laminates, alkali metal and silver laminates, alkali metal halides and Al laminates, and alkali metal oxides and Al laminates. Bodies, alkaline earth metal or laminates of rare earth metals and Al, and alloys of these metal species with other metals, such as sodium, sodium-potassium alloy, lithium, magnesium, etc. For example, a laminate with Al, a magnesium-silver mixture, a magnesium-indium mixture, an aluminum-lithium alloy, a LiF / Al mixture / laminate, an Al / Al ₂ O ₃ mixture, and the like can be given as examples.

  In the organic EL light emitting device formed as described above, light emitted from the organic light emitting layer 2 by applying a voltage between the light transmitting electrode 3 and the counter electrode 10 is transmitted through the light transmitting electrode. 3 is transmitted through the light extraction layer 4 including the relaxation layer 11 and the light scattering layer 5, and further transmitted through the translucent substrate 1. When the light emitted from the organic light emitting layer 2 passes through the light scattering layer 5 of the light extraction layer 4 in this way, the light is scattered to change the directivity of the light, and the interface between the light extraction layer 4 and the substrate 1 is changed. Thus, the total reflection of light can be suppressed.

  Here, when light emitted from the organic light emitting layer 2 is scattered by the light scattering layer 5 of the light extraction layer 4 in order to suppress total reflection at the interface with the substrate 1 in this way, light is extracted in an oblique direction. However, the light extraction efficiency to the front surface is reduced, and the light extraction efficiency cannot be sufficiently increased. Therefore, in the present invention, as the light scattering layer 5 formed containing light scattering particles, when the intensity of light incident and emitted from the front is measured, the intensity of light emitted to the front is 1 The output angle of light having an intensity of / 100 is 3 to 45 °.

  That is, as shown in FIG. 1B, a light scattering layer 5 is formed on the surface of a light-transmitting substrate 1, and light is incident on the surface of the light scattering layer 5 opposite to the substrate 1 at an incident angle of 0 ° from the front. The light is incident and emitted through the light scattering layer 5, and the intensity of the light extracted through the substrate 1 is set to the light emitted from the light scattering layer 5 to the front at an emission angle of 0 ° and from the light scattering layer 5. Measurement is made on light emitted obliquely at an emission angle θ, and the emission angle when the intensity of the light emitted obliquely becomes 1/100 of the intensity of the light emitted from the front (emission angle 0 °). The light scattering layer 5 in which θ is in the range of 3 to 45 ° is used. If the emission angle θ when the intensity of light emitted obliquely becomes 1/100 of the intensity of light emitted to the front is less than 3 °, the light scattering layer 5 goes straight and the front When the amount of light extracted in the direction increases, the extraction in the oblique direction becomes insufficient, and the intensity of light emitted obliquely becomes 1/100 of the intensity of light emitted in the front. If the emission angle θ exceeds 45 °, the light extraction to the front becomes insufficient, and neither can sufficiently increase the light extraction efficiency, but the intensity of the light emitted to the front By using the light scattering layer 5 having an emission angle θ of 3 to 45 ° when the intensity of the light emitted obliquely becomes 1/100, the reduction of the light extracted to the front is suppressed and the oblique direction The efficiency of extracting light to the Is shall. The outgoing angle θ is more preferably 3 to 30 °.

  In order to produce the light scattering layer 5 formed of the binder resin containing the light scattering particles as having the above-described characteristics with respect to the light emission intensity, the light scattering particles have a particle size (average particle size) of 0. The refractive index difference between the light scattering particles and the binder resin is preferably 0.001 to 0.1. If the particle diameter of the light scattering particles is less than 0.3 μm, or if the difference in refractive index between the light scattering particles and the binder resin is less than 0.001, the amount of light scattering in the light scattering layer 5 is reduced, and the front surface It becomes difficult to form the light scattering layer 5 having an emission angle θ of 3 ° or more when the intensity of the obliquely emitted light becomes 1/100 of the intensity of the emitted light. It becomes difficult to desire sufficient extraction efficiency in the direction. Conversely, if the particle size of the light scattering particles exceeds 10 μm, or if the difference in refractive index between the light scattering particles and the binder resin exceeds 0.3, the amount of light scattering in the light scattering layer 5 increases, and the light is emitted to the front. It becomes difficult to form the light scattering layer 5 having an emission angle θ of 45 ° or less when the intensity of the obliquely emitted light becomes 1/100 with respect to the intensity of the emitted light. It becomes difficult to desire sufficient removal efficiency. Either the light scattering particle or the binder resin may have a high refractive index or a low refractive index. Furthermore, when the particle diameter of the light scattering particles exceeds 10 μm, there is a risk that the light scattering particles may penetrate through the layers constituting the organic EL light emitting element to cause an element short circuit, and the reliability of the device may be impaired.

  It is also desirable that the volume ratio of the light scattering particles in the light scattering layer 5 is 90% or more and that the average number of light scattering particles in the thickness direction of the light scattering layer 5 is 1 to 10. The average number of light scattering particles in the thickness direction of the light scattering layer 5 is the number of light scattering particles existing on a straight line in the thickness direction of the light scattering layer 5 at five locations in the plane of the light scattering layer 5. It is obtained as the average value. When the ratio of the binder resin is small, the value obtained by dividing the average film thickness by the average particle diameter of the light scattering particles at three or more locations in the plane of the light scattering layer 5 is also used as the average number of particles in the thickness direction. Good.

  When the volume ratio of the light scattering particles in the light scattering layer 5 is less than 90%, or the average number of light scattering particles in the thickness direction of the light scattering layer 5 is less than 1, The amount of light scattering is reduced, and the light scattering layer 5 is formed with an emission angle θ of 3 ° or more when the intensity of light emitted obliquely becomes 1/100 of the intensity of light emitted to the front. It becomes difficult to achieve sufficient take-off efficiency in the oblique direction. Conversely, if the average number of light scattering particles in the thickness direction of the light scattering layer 5 exceeds 10, the amount of light scattering in the light scattering layer 5 increases, and the light intensity emitted to the front is It becomes difficult to form the light scattering layer 5 having an emission angle θ of 45 ° or less when the intensity of light emitted obliquely becomes 1/100, and it is difficult to desire sufficient extraction efficiency in the front direction. Become. The upper limit of the volume ratio of the light scattering particles in the light scattering layer 5 is not particularly set. However, as the volume ratio of the light scattering particles increases, the ratio of the binder resin decreases, causing a problem in the film strength of the light scattering layer 5 and the like. Therefore, the upper limit of the volume ratio of the light scattering particles in the light scattering layer 5 is about 98%.

  Next, the present invention will be specifically described with reference to examples. The weight average molecular weight was measured by GPC (gel permeation chromatography), using “HLC-8120” manufactured by Tosoh Co., Ltd. as a measuring instrument, creating a calibration curve with standard polystyrene, and converting it into a converted value.

Example 1
Add 803.5 parts by mass of isopropyl alcohol to 86.8 parts by mass of tetraethoxysilane, add 34.7 parts by mass of γ-methacryloxypropyltrimethoxysilane and 75 parts by mass of 0.1N nitric acid, and use a disper. A solution was obtained by mixing. The obtained solution was stirred in a constant temperature bath at 40 ° C. for 2 hours to obtain a 5% by mass solution of a silicone resin having a weight average molecular weight of 1050. Next, in this silicone resin solution, methylsilicone particles (“TOSPEARL 120” manufactured by GE Toshiba Silicone Co., Ltd .: average particle diameter 2 μm) are 80/20 based on the solid content mass of methylsilicone particles / silicone resin (condensation compound equivalent). Then, the mixture was dispersed with a homogenizer to obtain a methyl silicone particle-dispersed silicone resin solution as a coating material. The "condensation compound terms" above, in the case of tetraalkoxysilane, existing Si is mass as a SiO _2.

  Next, a non-alkali glass plate (“No. 1737” manufactured by Corning) was used as the translucent substrate 1, and the above coating material was applied to the surface of the substrate 1 with a spin coater at 1000 rpm, and dried. After repeating coating and drying 6 times, the light scattering layer 5 having a thickness of about 5 μm was formed by baking at 200 ° C. for 30 minutes. The optical properties of the substrate 1 with the light scattering layer 5 thus obtained were measured with a haze meter (“NDH-2000” manufactured by Nippon Denshoku Industries Co., Ltd.). The haze value was 95.4, the total light transmittance. Was 73.4%. The refractive index of the silicone resin constituting the light scattering layer 5 is 1.46 (measured with a prism coupler (made by Metricon) by forming a film having a thickness of 2 to 3 μm on a glass substrate), and the refractive index of methylsilicone particles. Is 1.44 to 1.45, and the refractive index difference between them is 0.02 or less. The volume ratio of methyl silicone particles in the light scattering layer 5 is 60%, and the average number of methyl silicone particles in the thickness direction of the light scattering layer 5 is 1.8 (= 3.6 μm / 2 μm; average film thickness 3 .6 μm is a contact type surface shape measuring device “DekTak 3” manufactured by Nippon Beco Co., Ltd., and an average particle diameter of methyl silicone particles is 2 μm.

  Further, regarding the light scattering layer 5 formed on the surface of the transparent glass substrate 1 in this manner, the relationship between the emission angle with respect to the front incident light and the light intensity is determined using a luminance light distribution characteristic measuring device (“C9920-11” manufactured by Hamamatsu Photonics). ). The results are shown in FIG. 2 (a) in terms of relative intensity when the intensity of front emission light (emission angle 0 °) is 1. FIG. 2 (b) shows an enlarged graph of a part of FIG. 2 (a). As can be seen from the graph of FIG. 2, the emission angle of light having an intensity of 1/100 with respect to the intensity of the front emission light was 5 °.

  Next, on the surface of the light scattering layer 5 formed as described above, an imide-based resin coating material (“HRI1783 manufactured by OPTMATE, refractive index = 1.78, concentration 18% by mass) was applied by a spin coater at 2000 rpm. Then, it was dried and cured by heating at 200 ° C. for 30 minutes to form a relaxation layer 11 having a thickness of about 4 μm.

  Next, an ITO film having a thickness of 120 nm was formed on the relaxing layer 11 by sputtering the surface of the relaxing layer 11 formed as described above using an ITO target (manufactured by Toto Corporation). Next, the substrate 1 thus formed with the ITO film was heat-treated at 200 ° C. for 1 hour in an Ar atmosphere to anneal the ITO film to form an electrode 3 as a transparent electrode having a sheet resistance of 18Ω / □. .

Next, the substrate 1 on which the transparent electrode 3 was formed was ultrasonically cleaned with acetone, pure water, and isopropyl alcohol for 15 minutes, then dried, and further subjected to UV-O ₃ treatment for 15 minutes. Thereafter, the substrate 1 is set in a vacuum deposition apparatus, and N, N′-diphenyl-N, N′-bis (1-naphthyl) -1,1′-biphenyl-4,4′- is used as a hole transport layer. Diamine (NPB) (manufactured by eRay) is formed on the electrode 3 with a film thickness of 40 nm, and further, an aluminum-tris (8-hydroxyquinoline) (Alq) (Alq) ( eRay Co., Ltd.) was formed with a film thickness of 60 nm, and LiF (manufactured by High Purity Chemical) was formed with a film thickness of 1 nm as an electron injection layer thereon. Finally, Al (manufactured by High Purity Chemical Co., Ltd.) was vacuum-deposited with a film thickness of 80 nm on the electron injection layer to form the counter electrode 10 as a cathode.

  Then, the board | substrate 1 formed by vapor-depositing each said layer was conveyed without exposing to the air | atmosphere to the glove box of a dry nitrogen atmosphere with a dew point -80 degrees C or less. On the other hand, a water-absorbing agent (manufactured by Dynic) was attached to a glass sealing cap and an ultraviolet curable resin-based sealing agent was applied to the outer periphery of the sealing cap in advance. Then, the sealing cap is bonded to the substrate 1 with a sealing agent so as to surround each layer in the glove box, and each layer is sealed with the sealing cap by irradiating with ultraviolet rays to cure the sealing agent, as shown in FIG. An organic EL light emitting device having such a layer structure was obtained.

(Comparative Example 1)
An ITO film was sputtered directly on the surface of the translucent substrate 1 and heat-treated at 200 ° C. for 1 hour to form an annealed electrode 3. And the organic light emitting layer 2 and the counter electrode 10 were formed directly on this electrode 3 like Example 1, and it sealed with the sealing cap, and the surface light-emitting body which consists of an organic EL light emitting element was obtained.

(Comparative Example 2)
The coating material of Example 1 was prepared using methyl silicone particles having an average particle size of 0.2 μm instead of methyl silicone particles having an average particle size of 2 μm. Otherwise, an organic EL light emitting device was obtained in the same manner as in Example 1.

  For the light scattering layer 5 formed in Comparative Example 2, the intensity of the emitted light was measured in the same manner as in Example 1. As a result, the emission angle of the light that was 1/100 of the intensity of the front emitted light was It was 2 °.

(Comparative Example 3)
To the silicone resin solution prepared in Example 1, an IPA dispersion sol (solid content 20 mass%, dispersion medium isopropyl alcohol, manufactured by Catalyst Kasei Kogyo Co., Ltd.) of hollow silica fine particles (refractive index 1.25, particle diameter 60 nm, outer shell thickness 10 nm). Sol) diluted with isopropyl alcohol to 5% by mass is added so as to be 35/30 based on the solid content mass of hollow silica fine particles / silicone resin (condensation compound equivalent), and dispersed with a homogenizer. Thus, a hollow silica particle-dispersed silicone resin solution was obtained as a coating material. Using this coating material, a light scattering layer 5 was formed in the same manner as in Example 1, and an organic EL light emitting device was obtained in the same manner as in Example 1 except for that.

  With respect to the light scattering layer 5 formed in Comparative Example 3, the intensity of the emitted light was measured in the same manner as in Example 1. As a result, the emission angle of the light that was 1/100 of the intensity of the front emitted light was It was 48 °.

(Comparative Example 4)
Acrylic UV curable oligomer (“6LPA” manufactured by Shin-Nakamura Chemical Co., Ltd.) and an acrylic UV curable monomer (“A-DPH” manufactured by Shin-Nakamura Chemical Co., Ltd.), “6LPA”: “A-DPH” = 2: 1 An acrylic UV curable resin was prepared by mixing at a (mass ratio) and further adding 3% by mass of a radical photopolymerization initiator (Nagase Sangyo “Irgacure 184”). Next, the same methylsilicone particles as in Example 1 were added to this acrylic UV curable resin so that the mass ratio of methylsilicone particles / acrylic UV curable resin was 20/80, and dispersed with a homogenizer. A methyl silicone particle-dispersed acrylic UV curable resin solution was obtained as a coating material.

  And after apply | coating a coating material on the glass substrate 1 like Example 1, the light-scattering layer 5 is formed by irradiating the integrated light quantity 1000mJ with a UV exposure machine, and others are the same as Example 1. Thus, an organic EL light emitting device was obtained.

  For the light scattering layer 5 formed in Comparative Example 4, the intensity of the emitted light was measured in the same manner as in Example 1. The results are shown in FIG. As can be seen in FIG. 2, the emission angle of light having an intensity of 1/100 with respect to the intensity of front emission light was 75 ° or more.

As described above, the characteristics of the organic EL light-emitting devices obtained in Example 1 and Comparative Examples 1 to 4 were fixed to 10 mA / cm ² using a DC power source (manufactured by Caselay), and the current flowing inside the device was fixed. Evaluation was performed using a luminance meter (Topcon). At this time, the front luminance was measured in the range of −180 ° to + 180 ° in an angular direction every 10 ° together with the current efficiency (cd / A), and the total luminous flux (power efficiency lm / W) was calculated. Table 1 shows the improvement ratio of the light extraction efficiency in the front and all directions, with the results based on the current efficiency (cd / A) and power efficiency (lm / W) of Comparative Example 1. The current-voltage characteristics were not significantly different between Example 1 and Comparative Examples 1 to 4. There was no significant difference in the emission spectrum.

  As seen in Table 1, it is confirmed that the light extraction efficiency of Example 1 is improved not only for Comparative Example 1 but also for Comparative Examples 2 to 4.

An example of embodiment of this invention is shown, (a) is the schematic which shows the layer structure of an organic electroluminescent light emitting element, (b) is a figure which shows the emitted light from a light-scattering layer. It is a graph which shows the measurement result of the intensity | strength of emitted light about the light-scattering layer of Example 1 and Comparative Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Organic light emitting layer 3 Electrode 4 Light extraction layer 5 Light scattering layer 10 Electrode 11 Relaxation layer

Claims (2)

The light emitted from the organic light-emitting layer is provided with a light-transmitting electrode between the light-transmitting substrate and the organic light-emitting layer and a light extraction layer that changes the directivity of light between the substrate and the light-transmitting electrode. In the organic EL light emitting device in which light is extracted from the light extraction layer and the light transmissive electrode through the light transmissive substrate, the light extraction layer is formed with a light scattering layer, and the light scattering layer contains light scattering particles. The light scattering particles have a particle size of 0.3 to 10 μm, the refractive index difference between the light scattering particles and the binder resin is 0.001 to 0.1, and the light scattering in the light scattering layer The volume ratio of the particles is 90% or more, the average number of light scattering particles in the thickness direction of the light scattering layer is 1 to 10, and the light scattering layer has the intensity of light incident and emitted from the front. When measured, it is 1/100 stronger than the intensity of light emitted from the front The organic EL light-emitting device is emission angle of light to be characterized in that it is a 3 to 45 °. A buffer layer for smoothing irregularities on the surface of the light scattering layer is provided between the light scattering layer and the translucent electrode, and the light extraction layer is formed of the light scattering layer and the buffer layer. the organic EL light-emitting device according to claim 1,.

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