JP2009004275A - Manufacturing method of surface light emitter and surface light emitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light emitter in which total reflection of light at the interface of a transparent electrode layer and a buffer layer is suppressed and extraction efficiency of light can be improved. <P>SOLUTION: The surface light emitter is provided with a light scattering portion 2 formed on the surface of a translucent substrate 1, a buffer layer 3 which is formed on the surface of the light scattering portion 2 and smoothes the surface roughness of the light scattering portion 2, a transparent electrode layer 4 formed on the surface of the buffer layer 3, and a light-emitting layer 5 which is formed on the opposite side to the translucent substrate of the transparent electrode layer 4. The buffer layer 3 has a refractive index which incliningly varies in the layer so that the refractive index on the transparent electrode layer 4 side may be higher and the refractive index on the light scattering portion 2 side may be smaller, and the refractive index at the interface with the transparent electrode layer 4 of the buffer layer 3 is same or smaller than that of the transparent electrode layer 4. Thereby, it can be made that a large difference in refractive indexes may not occur at the interface of the transparent electrode layer 4 and the buffer layer 3, and total reflection caused by the difference in refractive indexes at the interface can be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface light emitter used for various displays, display elements, liquid crystal backlights, and the like, and a method for producing the same.

  A typical example of the surface light emitter is an organic electroluminescence element (organic EL element). In this organic EL element, as shown in FIG. 3A, a transparent electrode layer 4 is provided on the surface of a translucent substrate 1, and a light emitting layer 5 made of an organic EL material is provided on the surface of the transparent electrode layer 4. The counter electrode 7 is provided on the surface of the light emitting layer 5. The light emitted from the light emitting layer 5 by applying a voltage between the transparent electrode layer 4 and the counter electrode 7 is transmitted through the transparent electrode layer 4 and the translucent substrate 1 and extracted.

When the light emitted from the light emitting layer 5 is extracted outside through the transparent electrode layer 4 and the translucent substrate 1 as described above, the light is extracted when the light is totally reflected at the interface between the transparent electrode layer 4 and the translucent substrate 1. Efficiency is reduced. For this purpose, as shown in FIG. 3B, a light scattering portion 2 is formed between the transparent electrode layer 4 and the translucent substrate 1, and light is scattered by the light scattering portion 2, whereby the transparent electrode layer 4 The occurrence of total reflection at the interface between the light transmitting substrate 1 and the translucent substrate 1 is reduced to increase the light extraction efficiency. The light scattering portion 2 is provided with fine irregularities on the surface of the transparent substrate 1 on the transparent electrode layer 4 side, or a coating resin layer containing particles on the transparent electrode layer 4 side of the transparent substrate 1. In any case, the surface becomes uneven, so that the relief layer 3 is formed on the surface of the light scattering portion 2 as shown in FIG. The transparent electrode layer 4 having a thin film thickness is formed on the smooth surface of the relaxation layer 3 (see, for example, Patent Document 1 and Patent Document 2).
Japanese Patent Laid-Open No. 2003-216061 JP 2006-286616 A

  However, if the relaxation layer 3 is formed between the light scattering portion 2 and the transparent electrode layer 4 as described above, light may be totally reflected at the interface between the transparent electrode layer 4 and the relaxation layer 3, and this total reflection is caused. This causes a problem that the light extraction efficiency is lowered.

  The present invention has been made in view of the above points, and suppresses the total reflection of light at the interface between the transparent electrode layer and the relaxation layer, and the surface light emitter capable of improving the light extraction efficiency and its The object is to provide a manufacturing method.

  The surface light emitter according to claim 1 of the present invention smoothes the surface roughness of the light scattering portion 2 formed on the surface of the light scattering portion 2 and the light scattering portion 2 formed on the surface of the light transmissive substrate 1. In the surface light emitter comprising the relaxation layer 3, the transparent electrode layer 4 formed on the surface of the relaxation layer 3, and the light emitting layer 5 formed on the opposite side of the transparent electrode layer 4 from the translucent substrate 1, 3 has a refractive index that changes in an inclined manner in the layer so that the refractive index on the transparent electrode layer 4 side is high and the refractive index on the light scattering portion 2 side is low, and the transparent electrode layer of the relaxation layer 3 4 is characterized in that the refractive index of the interface with the transparent electrode layer 4 is the same as or lower than the refractive index of the transparent electrode layer 4.

  According to the present invention, the refractive index of the relaxation layer 3 changes so as to be inclined so as to be high on the transparent electrode layer 4 side and low on the light scattering portion 2 side, and the interface between the relaxation layer 3 and the transparent electrode layer 4 Since the refractive index of the transparent electrode layer 4 is equal to or lower than the refractive index of the transparent electrode layer 4, it is possible to prevent a large difference in refractive index from occurring at the interface between the transparent electrode layer 4 and the relaxing layer 3. It is possible to suppress the total reflection caused by the rate difference and improve the light extraction efficiency.

  The surface light emitter according to claim 2 of the present invention smoothes the surface roughness of the light scattering portion 2 formed on the surface of the light scattering portion 2 and the light scattering portion 2 formed on the surface of the light transmissive substrate 1. In the surface light emitter comprising the relaxation layer 3, the transparent electrode layer 4 formed on the surface of the relaxation layer 3, and the light emitting layer 5 formed on the opposite side of the transparent electrode layer 4 from the translucent substrate 1, 3 has a refractive index that changes in an inclined manner in the layer so that the refractive index on the transparent electrode layer 4 side is low and the refractive index on the light scattering portion 2 side is high, and the transparent electrode layer of the relaxation layer 3 4 is characterized in that the refractive index of the interface with the transparent electrode layer 4 is equal to or higher than the refractive index of the transparent electrode layer 4.

  According to the present invention, the refractive index of the relaxation layer 3 changes so as to be inclined so as to be low on the transparent electrode layer 4 side and high on the light scattering portion 2 side, and the interface of the relaxation layer 3 with the transparent electrode layer 4 Since the refractive index of the transparent electrode layer 4 is the same as or higher than the refractive index of the transparent electrode layer 4, it is possible to prevent a large difference in refractive index from occurring at the interface between the transparent electrode layer 4 and the relaxation layer 3, and the refraction at the interface. It is possible to suppress the total reflection caused by the rate difference and improve the light extraction efficiency.

  The surface light emitter according to claim 3 of the present invention smoothes the surface roughness of the light scattering portion 2 formed on the surface of the light transmissive substrate 1 and the light scattering portion 2 formed on the surface of the light scattering portion 2. A surface emitting body comprising: a relaxing layer 3 for forming the transparent electrode layer 4 formed on the surface of the relaxing layer 3; and a light emitting layer 5 formed on the opposite side of the transparent electrode layer 4 from the light transmitting substrate. Is formed in a multilayer structure of two or more layers in which the refractive index of the layer 3a on the transparent electrode layer 4 side is high and the refractive index of the layer 3b on the light scattering portion 2 side is low, and the layer 3a closest to the transparent electrode layer 4 is formed. The refractive index is the same as or lower than the refractive index of the transparent electrode layer 4.

  According to this invention, the relaxation layer 3 is formed in a multilayer structure of two or more layers in which the refractive index of the layer 3a on the transparent electrode layer 4 side is high and the refractive index of the layer 3b on the light scattering portion 2 side is low, and the most transparent The refractive index of the layer 3a close to the electrode layer 4 is the same as or lower than the refractive index of the transparent electrode layer 4, so that a large refractive index difference does not occur at the interface between the transparent electrode layer 4 and the relaxing layer 3. Thus, total reflection caused by the difference in refractive index at the interface can be suppressed, and the light extraction efficiency can be improved.

  The surface light emitter according to claim 4 of the present invention smoothes the surface roughness of the light scattering portion 2 formed on the surface of the translucent substrate 1 and the surface of the light scattering portion 2 formed on the surface of the light scattering portion 2. In the surface light emitter comprising the relaxation layer 3, the transparent electrode layer 4 formed on the surface of the relaxation layer 3, and the light emitting layer 5 formed on the opposite side of the transparent electrode layer 4 from the translucent substrate 1, 3 is formed in a multilayer structure of two or more layers in which the refractive index of the layer 3a on the transparent electrode layer 4 side is low and the refractive index of the layer 3b on the light scattering portion 2 side is high, and the layer 3a closest to the transparent electrode layer 4 The refractive index is equal to or higher than the refractive index of the transparent electrode layer 4.

  According to the present invention, the relaxation layer 3 is formed in a multilayer structure of two or more layers in which the refractive index of the layer 3a on the transparent electrode layer 4 side is low and the refractive index of the layer 3b on the light scattering portion 2 side is high, and the most transparent The refractive index of the layer 3a close to the electrode layer 4 is the same as or higher than the refractive index of the transparent electrode layer 4, so that a large difference in refractive index does not occur at the interface between the transparent electrode layer 4 and the relaxing layer 3. Thus, total reflection caused by the difference in refractive index at the interface can be suppressed, and the light extraction efficiency can be improved.

  The method for manufacturing a surface light emitter according to claim 5 of the present invention includes a step of forming the light scattering portion 2 on the surface of the light-transmitting substrate 1, a resin coating on the surface of the light scattering portion 2, and a coating resin. The step of forming the relaxation layer 3 by heat curing, the step of forming the transparent electrode layer 4 on the surface of the relaxation layer 3, and the heat treatment at a temperature higher than the curing temperature of the coating resin of the relaxation layer 3 relaxes. The step of changing the refractive index of the layer 3 by inclining in the thickness direction inside the layer and the step of forming the light emitting layer 5 on the surface of the transparent electrode layer 4 are sequentially performed.

  According to this invention, by forming the relaxation layer 3 and the transparent electrode layer 4 and then performing a heat treatment, the refractive index of the relaxation layer 3 can be changed in the thickness direction in the layer, which is referred to as a heat treatment. The relaxing layer 3 as in claims 1 and 2 can be formed in the process.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, in the heat treatment step, the material component of the relaxation layer 3 and the material component of the transparent electrode layer 4 are diffused and mixed so that the refractive index of the relaxation layer 3 is increased within the layer. It is characterized in that it is changed by inclining in the direction.

  According to this invention, it is possible to prevent a large difference in refractive index from occurring at the interface between the transparent electrode layer 4 and the relaxation layer 3 by diffusion mixing of the material components of the relaxation layer 3 and the transparent electrode layer 4, It is possible to improve the light extraction efficiency by suppressing total reflection caused by the difference in refractive index at the interface.

  According to the present invention, when the light emitted from the light emitting layer 5 is taken out through the transparent electrode layer 4, the relaxation layer 3, the light scattering portion 2, and the translucent substrate 1, the light is scattered by the light scattering portion 2. The total reflection at the interface of the conductive substrate 1 can be suppressed, and a large difference in refractive index is not generated at the interface between the transparent electrode layer 4 and the relaxation layer 3. It is possible to suppress the total reflection of light, and to improve the light extraction efficiency.

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

  The light-transmitting substrate 1 can be used without particular limitation as long as it transmits light. For example, a rigid transparent glass plate such as soda glass or non-alkali glass, polycarbonate, or polyethylene terephthalate. Arbitrary things, such as flexible transparent plastic boards, such as these, can be used.

  The light scattering portion 2 provided on the surface of the translucent substrate 1 may have any structure that scatters light. The light scattering portion 2 can be formed by sandblasting or the like. The method is roughly divided into a method of forming a rough surface having fine irregularities on the surface of the translucent substrate 1 and a method of forming a light scattering layer 2a for scattering light on the surface of the translucent substrate 1. be able to. The structure for scattering light may be isotropic scattering or scattering having directivity, and may be appropriately selected according to the light and angle to be extracted. The light scattering layer 2a can be formed by patterning a resin coating layer on the surface of the translucent substrate 1, or by direct patterning coating (such as nanoimprinting), or by translucent a binder containing particles. There is a method of coating the surface of the substrate 1.

  In the present invention, the method for forming the light scattering portion 2 may be any of those described above, but the method for forming the light scattering layer 2a by coating a binder containing particles is easy and has various This is preferable because it has the feature of easily controlling the optical factor.

Transparent particles are used as the 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 porosity Examples thereof include inorganic particles mainly composed of substances and organic particles such as acrylic resin, styrene resin, polyethylene terephthalate resin, and silicone resin. The particle diameter is preferably in the range of 100 nm to 20 μm for effective Mie scattering.

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

  The refractive index difference between the binder and the light scatterer is usually preferably in the range of 0.01 to 2. If this refractive index difference is too small, it becomes difficult to obtain effective Mie scattering, and the refractive index difference is If it is too large, the backscattering increases and the light extraction rate may not be sufficiently obtained.

  The coating material obtained by blending the particles with the binder is coated on the surface of the translucent substrate 1 by a method such as spin coating, dip coating, die coating, casting, spray coating, gravure coating, etc., so that the light scattering layer 2a Can be formed. The thickness of the light scattering layer 2a is not particularly limited, but is preferably in the range of about 0.1 to 20 μm.

The light scattering layer 2a can also be formed using two types of fine particles having different refractive indexes. That is, assuming that the refractive index of the binder is Nb, one of the two types of fine particles is Nf ₁ , and the other refractive index is Nf ₂ , the binder and 2 so as to satisfy the relationship Nf ₂ >Nb> Nf _1. A type of fine particles is selected and used. The light scattering layer 2a composed of the binder having the refractive index having such a relationship and the two kinds of fine particles has a light scattering effect amplified by the difference between the refractive indexes, and the light scattering layer 2a transmits light. By forming on the surface of the light-transmitting substrate 1, the critical angle at the interface between the light scattering layer 2a and the light-transmitting substrate 1 is disturbed, and more light is transmitted to the light-transmitting substrate 1, and light is transmitted. The extraction efficiency is increased.

  Examples of the two kinds of fine particles having different refractive indexes include airgel fine particles, hollow silica fine particles, polymer hollow fine particles, organic polymer fine particles, metal oxide fine particles, and the like. In order to improve the dispersibility, these fine particles are preferably subjected to a surface coating treatment that does not significantly change the refractive index, such as a surfactant treatment or a thin film coating treatment.

The refractive indexes Nf ₁ and Nf ₂ of the fine particles are generally in the range of 1.2 to 2.5, but one of the two types of fine 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. Thus, when the refractive index Nf1 of _one fine particle is 1.4 or less, the refractive index of the light scattering layer 2a is greatly reduced, the light scattering property is high, and the light scattering layer 2a having a low refractive index is obtained. It can be formed. Also in this case, it is desirable that the difference in refractive index _Nf 1, Nf ₂ of the two types of fine particles is 0.5 or more. When the two kinds of fine particles have a refractive index difference of 0.5 or more, the light scattering intensity of the light scattering layer 2a is increased, and as a result, the light extraction efficiency is further improved. The upper limit of the difference in refractive index between the two types of fine particles is not particularly limited, but is generally preferably about 1.3 or less.

  The average particle size of the two types of fine particles is preferably in the range of 5 to 200 nm. This is because when the average particle diameter of the fine particles exceeds 200 nm, the surface roughness of the light scattering layer 2a formed containing the fine particles increases, and when the average particle diameter of the fine particles becomes too small. The average particle diameter of the fine particles is preferably 5 nm or more because the light scattering effect is insufficient. The two kinds of fine particles preferably have different average particle diameters. In this case, the average particle diameter of one fine particle and the other fine particle preferably has a difference of 2 times or more. Thus, when the difference in the average particle size of the two types of fine particles is more than twice, the fine particles are mixed in the binder in a state where the other fine particles having the smaller average particle size enter between the fine particles having the larger average particle size. Dispersion improves the dispersibility of the fine particles in the binder, and the light scattering layer 2a in which the fine particles are uniformly dispersed can be formed. The upper limit of the difference between the average particle sizes of the two types of fine particles is not particularly limited, but it is desirable that the difference between the average particle sizes of the two types of particles be in the range of 15 to 50 nm. The particle diameter and average particle diameter of the fine particles are numerical values measured using a particle size distribution measuring apparatus using a laser diffraction principle as described later.

On the other hand, examples of materials that can be used for the binder include organic polymers, metal oxides, and porous silica. A material having a refractive index satisfying the above relationship with the refractive indexes Nf ₁ and Nf _{2 of} the two kinds of fine particles may be selected from these usable materials. The refractive index Nb of the binder is generally in the range of 1.45 to 1.60.

  In the combination of the binder and the two kinds of fine particles, among the above materials, the fine particles are at least one selected from airgel fine particles, hollow silica fine particles, and polymer hollow fine particles, and the binder is selected from organic polymers and metal oxides. At least one is preferred.

Although the film thickness of the light-scattering layer 2a formed as mentioned above is not specifically limited, Generally the range of 0.1-20 micrometers is preferable. Further, the content ratio of the two kinds of fine particles to the binder is not particularly limited, but generally, the two kinds of fine particles are set to have a mass ratio of 10:90 to 70:30 with respect to the binder. preferable. Further, the ratio of the two kinds of fine particles is not particularly limited, but those having a small refractive index Nf ₁ and those having a large refractive index Nf ₂ are preferably blended at a mass ratio of 1: 9 to 9: 1.

  In many cases, the refractive index of the light scattering layer 2a formed as described above is in the range of 1.30 to 1.70, but is equal to or smaller than the refractive index of the translucent substrate 1. It is preferable to set as follows. As described above, when the refractive index of the light scattering layer 2a is equal to or lower than the refractive index of the translucent substrate 1, the light incident on the translucent substrate 1 from the light scattering layer 2a is reduced from being totally reflected. This can increase the efficiency of extracting light to the outside.

  The light scattering layer 2a formed as described above preferably 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 2a within this range, it is possible to improve the light extraction efficiency without impairing the appearance of the surface light emitter. 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.

  Thus, after the light scattering layer 2a containing two kinds of fine particles is formed on the surface of the translucent substrate 1, the light scattering layer 2a containing the Mie scattering particle size is further formed thereon. It may be.

  Even if the light scattering portion 2 is formed by any of the above methods, the surface of the light scattering portion 2 becomes a rough surface having irregularities. For example, when the light scattering portion 2 is formed by the light scattering layer 2a of a coating material containing particles, irregularities are generated by the particles exposed on the surface of the light scattering layer. For this reason, when the transparent electrode layer 4 is formed directly on the surface of the light scattering portion 2, the transparent electrode layer 4 is formed in a shape that follows the unevenness because the film thickness is thin, causing problems in electrical characteristics. Short circuit may occur. Therefore, a relaxation layer 3 is formed on the surface of the light scattering portion 2 opposite to the translucent substrate 1, and the unevenness of the light scattering portion 2 is filled with the relaxation layer 3, so that the smooth surface of the relaxation layer 3 is smoothed. The transparent electrode layer 4 is formed.

  This relaxation layer 3 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 part 2, the relaxation layer 3 can be formed by heating and hardening. Although the film thickness of the relaxation layer 3 is not specifically limited, The range of about 1-20 micrometers is preferable.

  The refractive index of the resin forming the relaxation layer 3 is lower than the refractive index of the light scattering layer 2a or higher than the refractive index of the light scattering layer 2a when the light scattering portion 2 is formed of the light scattering layer 2a. It is desirable that the difference is small.

  After providing the relaxation layer 3 on the surface of the light scattering portion 2 as described above, the transparent electrode layer 4 is formed on the surface of the relaxation layer 3 opposite to the light scattering portion 2. Any material can be used as the material of the transparent electrode layer 4 as long as the effect of the present invention is not hindered. Examples thereof include indium-tin oxide (ITO), indium-zinc oxide (IZO), and tin oxide. , Ultra-thin 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 laminate of these Etc. These transparent electrode layers 4 are usually formed using a vapor phase growth method such as a sputtering method or an ion plating method. The film thickness of the transparent electrode layer 4 is not particularly limited, but is preferably about 50 to 300 nm.

  Thus, when forming the transparent electrode layer 4, heat processing is performed in order to anneal an electrode material. The heat treatment is performed at a high temperature exceeding the curing temperature, which is the heating temperature for curing the resin forming the relaxation layer 3 as described above. When the heat treatment is performed at a temperature higher than the curing temperature of the resin forming the relaxation layer 3 in this way, the material component of the relaxation layer 3 and the transparent electrode layer 4 at the contact interface between the relaxation layer 3 and the transparent electrode layer 4. A mixing portion 10 in which material components are diffusely mixed is formed as a part of the relaxation layer 4. The conditions for this heat treatment are not particularly limited as long as the temperature is higher than the curing temperature of the resin that forms the relaxation layer 3, but the curing temperature of the resin that forms the relaxation layer 3 is T ° C. The heating temperature is preferably set in the range of T ° C. + 5 ° C. to T ° C. + 100 ° C., and the heating time is preferably about 10 minutes to 2 hours.

  The mixing portion 10 formed in the relaxation layer 3 by performing the heat treatment as described above has a large amount of material components forming the transparent electrode layer 4 on the transparent electrode layer 4 side, and the light scattering portion 2 side. Thus, the material concentration of the relaxation layer 3 is large, and the material concentration distribution is inclined.

  Therefore, when the relaxation layer 3 is formed of a material having a lower refractive index than that of the transparent electrode layer 4, the refractive index of the mixing unit 10 in the relaxation layer 3 is higher on the transparent electrode layer 4 side and on the light scattering unit 2 side. It has a refractive index that changes in an inclined manner within the layer, and the refractive index of the interface between the relaxation layer 3 and the transparent electrode layer 4 is the same as or lower than the refractive index of the transparent electrode layer 4. It is possible to prevent a large difference in refractive index from occurring at the interface between the transparent electrode layer 4 and the relaxing layer 3.

  Alternatively, when the relaxation layer 3 is formed of a material having a higher refractive index than the transparent electrode layer 4, the refractive index of the mixing unit 10 in the relaxation layer 3 is lower on the transparent electrode layer 4 side and on the light scattering unit 2 side. The refractive index at the interface between the relaxation layer 3 and the transparent electrode layer 4 is the same as or higher than the refractive index of the transparent electrode layer 4. Similarly, it is possible to prevent a large difference in refractive index from occurring at the interface between the transparent electrode layer 4 and the relaxing layer 3.

  Next, after providing the transparent electrode layer 4 on the surface of the relaxation layer 3 as described above, the light emitting layer 5 is formed on the surface of the transparent electrode layer 4 opposite to the relaxation layer 3. As a material for forming the light emitting layer 5, an organic EL material can be used. For example, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxa Diazole, bisbenzoxazoline, 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-i ) Amine, pyran, quinacridone, rubrene, and derivatives thereof, or 1-aryl-2,5-di (2-thienyl) pyrrole derivative, distyrylbenzene derivative, styrylarylene derivative, styrylamine derivative, and light emission thereof Examples thereof include a compound or a polymer having a group consisting of a functional compound in a part of the molecule. Further, not only compounds derived from fluorescent dyes typified by the above-mentioned 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 counter electrode 7 on the surface of the light emitting layer 5 opposite to the transparent electrode layer 4, a surface light emitter as shown in FIG. 1 made of an organic EL element can be formed. As the material of the counter electrode 7, Al or the like can be used. However, a structure in which Al and another electrode material are combined to form a laminated structure or the like may be used. 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 addition, in order to reduce the damage at the time of forming the hole transport layer, the electron transport layer, the buffer layer, or the electrode between the light emitting layer 5 and the electrodes 4 and 7 to improve the carrier injection property from the electrodes 4 and 7. For example, an alkali metal doped organic layer, a copper phthalocyanine layer, an acceptor doped organic layer, or the like may be formed.

  In the surface light emitter formed as described above, light emitted from the light emitting layer 5 by applying a voltage between the transparent electrode layer 4 and the counter electrode 7 is transmitted from the transparent electrode layer 4 to the relaxing layer 3 and The light is transmitted through the light scattering portion 2 and further transmitted through the translucent substrate 1 and taken out. At this time, the relaxation layer 3 has a structure in which the refractive index is inclined in the layer, and is formed so that there is no difference in the refractive index at the interface between the transparent electrode layer 4 and the relaxation layer 3 or the difference is small. Therefore, the light transmitted from the transparent electrode layer 4 to the relaxation layer 3 can be prevented from being totally reflected at the interface. In addition, since the light transmitted from the relaxation layer 3 to the light scattering portion 2 is scattered by the light scattering portion 2, the light is prevented from being totally reflected at the interface between the light scattering portion 2 and the translucent substrate 1. be able to. In this way, total reflection at each interface is suppressed, and light is efficiently transmitted from the transparent electrode layer 4 to the relaxation layer 3, the light scattering portion 2, and the translucent substrate 1 to be transmitted. The light can be extracted from the substrate 1, and the light extraction efficiency of the light emitted from the light emitting layer 5 is improved.

  FIG. 2 shows another embodiment of the present invention, in which the relaxation layer 3 is formed in a multilayer structure of two or more layers. Each of the multiple layers forming the relaxation layer 3 is set so that the refractive index of the layer 3a on the transparent electrode layer 4 side is high and the refractive index of the layer 3b on the light scattering portion 2 side is low. Is set so that the refractive index of the layer 3a close to is the same as or lower than the refractive index of the transparent electrode layer 4. Therefore, when the relaxation layer 3 is formed of a material having a lower refractive index than that of the transparent electrode layer 4, a large difference in refractive index can be prevented from occurring at the interface between the transparent electrode layer 4 and the relaxation layer 3. Yes, light transmitted from the transparent electrode layer 4 to the relaxation layer 3 can be prevented from being totally reflected at the interface.

  In addition, when the relaxation layer 3 is formed in a multilayer structure of two or more layers as described above, each of the multilayer layers forming the relaxation layer 3 has a low refractive index of the layer 3a on the transparent electrode layer 4 side, and is on the light scattering portion 2 side. The refractive index of the layer 3b may be set to be high, and the refractive index of the layer 3a closest to the transparent electrode layer 4 may be set to be the same as or higher than the refractive index of the transparent electrode layer 4. Therefore, when the relaxation layer 3 is formed of a material having a higher refractive index than the transparent electrode layer 4, it is possible to prevent a large difference in refractive index from occurring at the interface between the transparent electrode layer 4 and the relaxation layer 3. Yes, light transmitted from the transparent electrode layer 4 to the relaxation layer 3 can be prevented from being totally reflected at the interface.

  Although FIG. 2 shows a case where the relaxation layer 3 is formed in two layers, it goes without saying that the relaxation layer 3 can be formed in three or more layers.

  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, to this silicone resin solution, methylsilicone particles (“TOSPEARL 120” manufactured by GE Toshiba Silicone Co., Ltd .: average particle size 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. 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 methylsilicone particle-dispersed silicone resin solution was applied to the surface of the translucent substrate 1 at 1000 rpm using a spin coater. After drying and repeating this coating and drying 6 times, the light scattering layer 2a having a thickness of about 5 μm was formed by baking at 200 ° C. for 30 minutes. The optical properties of the translucent substrate 1 with the light scattering layer 2a thus obtained were measured with a haze meter (“NDH-2000” manufactured by Nippon Denshoku Industries Co., Ltd.). The haze value was 95.4, all The light transmittance was 73.4%.

  On the surface of the light scattering layer 2a thus formed, an imide resin coating material ("HRI1783: nD = 1.78, concentration 18% by mass, manufactured by OPTMATE) was applied by a spin coater under the condition of 2000 rpm and dried. The relaxation layer 3 having a thickness of about 4 μm was formed by heating and curing at 200 ° C. for 30 minutes.

  Next, an ITO film having a thickness of 120 nm was formed on the relaxing layer 3 by sputtering the surface of the relaxing layer 3 formed as described above using an ITO target (manufactured by Toto). Next, the transparent substrate 1 on which the ITO film is formed in this manner is heat-treated at 300 ° C. for 1 hour in an Ar atmosphere, thereby annealing the ITO film to form the transparent electrode layer 4 having a sheet resistance of 18Ω / □. Formed.

  The refractive index (@ 632 nm) of the relaxation layer 3 and the transparent electrode layer 4 formed in this manner was analyzed using an optical thin film analyzer (“Film-Tek-3000” manufactured by SCI). The refractive index of the relaxation layer 3 is 1.77 at a position of 0.8 μm from the interface side with the light scattering layer 2 a and 1.81 at a position of 3.1 μm, and the refractive index on the light scattering layer 2 a side is low, It changed in an inclined manner in the layer so that the refractive index on the transparent electrode layer 4 side was increased. The refractive index of the transparent electrode layer 4 was 1.98.

Next, the translucent substrate 1 on which the transparent electrode layer 4 was formed was ultrasonically washed 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 translucent substrate 1 is set in a vacuum deposition apparatus, and N, N′-diphenyl-N, N′-bis (1-naphthyl) -1,1′-biphenyl-4, 4′-diamine (NPB) (manufactured by eRay) is formed on the transparent electrode layer 4 with a film thickness of 40 nm, and further, an aluminum-tris (8-hydroxyquinoline) is formed thereon as the electron transport layer / light-emitting layer 5. (Alq) (manufactured by eRay) was formed with a film thickness of 60 nm, and LiF (manufactured by high purity chemical) was formed thereon with a film thickness of 1 nm as an electron injection layer. Finally, Al (manufactured by High-Purity Chemical Co., Ltd.) was vacuum-deposited with a thickness of 80 nm on the electron injection layer to form the counter electrode 7 as a cathode.

  Then, the translucent 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 of -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, a sealing cap is attached to the light-transmitting 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. A surface light emitter comprising an organic EL element having a layer structure as in a) was obtained.

(Example 2)
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, to this silicone resin solution, an IPA dispersion sol (solid content: 20% by mass, dispersion medium: isopropyl alcohol, manufactured by Catalyst Kasei Kogyo Co., Ltd.) of hollow silica fine particles (average particle diameter 60 nm, outer shell thickness 10 nm) is added with isopropyl alcohol. The sol diluted to 5% by mass was added so as to be 35/30 based on the solid content mass of hollow silica fine particles / silicone resin (condensation compound equivalent) to obtain a hollow silica fine particle-containing silicone resin solution. Further, to this solution, methylethylketone dispersion sol (solid content: 20% by mass, produced by Catalyst Kasei Kogyo Co., Ltd.) of silica-titania composite fine particles (average particle size 10-20 nm) coated with silica on the surface of titania particles was added with isopropyl alcohol. The sol diluted to 5% by mass is added to 35/35/30 based on the solid content mass of hollow silica fine particles / silica-titania composite fine particles / silicone resin (condensed compound equivalent), and finally Coating composition was obtained.

Here, the refractive index Nd, refractive index Nf ₁ of the hollow silica fine particles of the silicone resin of the binder material, silica - refractive index Nf ₂ of the titania fine particles are each 1.40,1.25,1.85, Nf ₂ >Nb> Nf ₁ was satisfied. These refractive indexes were measured as follows. The binder material was coated to form a thin film, and the refractive index was measured with an ellipsometer. The refractive index of each of the hollow silica fine particles and silica-titania fine particles is determined by the immersion method (dispersing the fine particles in various refractive index liquids, and using the haze meter to determine the refractive index of the refractive index liquid at which the haze is zero. It was measured using a method for obtaining the refractive index of fine particles. The haze value was measured using a haze meter (Nippon Denshoku, 300A) based on JIS-K-7136. Further, the average particle diameters of the hollow silica fine particles and silica-titania fine particles are 60 nm and 10-20 nm, respectively, as described above, and these particle sizes are measured by a particle size distribution measuring apparatus (manufactured by Horiba, Ltd.) using a laser diffraction principle. ).

  Next, a non-alkali glass plate (“No. 1737” manufactured by Corning Inc., refractive index 1.51) is used as the translucent substrate 1, and the above coating material composition is applied to the surface of the translucent substrate 1 by a spin coater. A coating film was prepared by coating and drying at 1000 rpm, followed by baking at 200 ° C. for 30 minutes and heat treatment to form a light scattering layer 2a having a thickness of about 500 nm. The light scattering layer 2a thus obtained has a refractive index of 1.45, which is smaller than the refractive index of the translucent substrate 1. Moreover, the haze value of the light-scattering layer 2a was 3.0, and the total light transmittance was 85.7%.

  After forming the light scattering layer 2a having a thickness of about 500 nm in this manner, the methylsilicone particle-dispersed silicone resin solution was applied, dried and fired thereon in the same manner as in Example 1 to form the light scattering layer 2a having a thickness of about 5 μm. Then, as in Example 1, the relaxing layer 3, the transparent electrode layer 4, the light emitting layer 5, and the counter electrode 7 are formed and sealed with a sealing cap to obtain a surface light emitter made of an organic EL element. It was.

(Example 3)
A surface light emitter made of an organic EL element was obtained in the same manner as in Example 1 except that the heat treatment for annealing the transparent electrode layer 4 was performed at 300 ° C. for 1 hour.

  In this structure, the refractive index of the relaxation layer 3 is 1.74 at a position of 0.3 μm from the interface side with the light scattering layer 2 a and 1.78 at a position of 3.6 μm, and is on the light scattering layer 2 a side. The refractive index of the transparent electrode layer 4 side was changed so that the refractive index of the transparent electrode layer 4 side was increased and the refractive index of the transparent electrode layer 4 side was increased. The refractive index of the transparent electrode layer 4 was 1.90. The sheet resistance of the transparent electrode layer 4 was the same as that in Example 1.

Example 4
A surface emission composed of an organic EL element in the same manner as in Example 1 except that the heat-curing of the relaxation layer 2 is performed at 200 ° C. for 30 minutes and the heat treatment for annealing the transparent electrode layer 4 is performed at 250 ° C. for 1 hour. Got the body.

  In this structure, the refractive index of the relaxation layer 3 is 1.74 at a position of 0.3 μm from the interface side with the light scattering layer 2 a and 1.80 at a position of 3.4 μm, and is on the light scattering layer 2 a side. The refractive index of the transparent electrode layer 4 side was changed so that the refractive index of the transparent electrode layer 4 side was increased and the refractive index of the transparent electrode layer 4 side was increased. The refractive index of the transparent electrode layer 4 was 1.82. The sheet resistance of the transparent electrode layer 4 was the same as that in Example 1.

(Comparative Example 1)
An ITO film was sputtered directly on the surface of the translucent substrate 1, and the transparent electrode layer 4 annealed by heat treatment at 300 ° C. for 1 hour was formed. Then, a light emitting layer and a counter electrode were formed thereon as in Example 1, and sealed with a sealing cap to obtain a surface light emitter made of an organic EL element.

(Comparative Example 2)
In Example 1, after the ITO film was sputtered, the annealed transparent electrode layer 4 was formed by heat treatment at 100 ° C. for 1 hour. Others were the same as in Example 1 to obtain a surface light emitter made of an organic EL element.

  In this structure, the refractive index of the relaxation layer 3 was 1.78 almost uniformly in the layer, and the refractive index of the transparent electrode layer 4 was 1.95. The sheet resistance of the transparent electrode layer 4 was 40Ω / □.

As described above, the characteristics of the surface light emitters composed of the organic EL elements obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were measured using a DC power source (manufactured by Caseley Co.), and the current flowing inside the element was 10 mA / It fixed to cm < ² > and evaluated using the luminance meter (made by 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. The results are shown in Table 1 as relative values with Comparative Example 1 taken as 1. The current-voltage characteristics were not significantly different between Examples 1 to 4 and Comparative Examples 1 and 2. There was no significant difference in the emission spectrum.

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

It is the schematic which shows an example of embodiment of this invention. It is the schematic which shows an example of other embodiment of this invention. It is the schematic which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Translucent board | substrate 2 Light-scattering part 3 Relaxation layer 4 Transparent electrode layer 5 Light emitting layer 7 Counter electrode

Claims (6)

  A light scattering part formed on the surface of the translucent substrate, a relaxation layer formed on the surface of the light scattering part, for smoothening the surface roughness of the light scattering part, a transparent electrode layer formed on the surface of the relaxation layer, In a surface light emitter having a light emitting layer formed on the opposite side of the transparent electrode layer from the light transmissive substrate, the relaxation layer has a high refractive index on the transparent electrode layer side and a low refractive index on the light scattering portion side. And a refractive index that changes in an inclined manner in the layer, and the refractive index of the interface between the relaxation layer and the transparent electrode layer is the same as or lower than the refractive index of the transparent electrode layer.   A light scattering part formed on the surface of the translucent substrate, a relaxation layer formed on the surface of the light scattering part, for smoothening the surface roughness of the light scattering part, a transparent electrode layer formed on the surface of the relaxation layer, In a surface light emitter having a light emitting layer formed on the opposite side of the transparent electrode layer from the light transmissive substrate, the relaxation layer has a low refractive index on the transparent electrode layer side and a high refractive index on the light scattering portion side. And a refractive index that changes in an inclined manner within the layer, and the refractive index at the interface between the relaxation layer and the transparent electrode layer is the same as or higher than the refractive index of the transparent electrode layer.   A light scattering part formed on the surface of the translucent substrate, a relaxation layer formed on the surface of the light scattering part, for smoothening the surface roughness of the light scattering part, a transparent electrode layer formed on the surface of the relaxation layer, In a surface light emitter having a light emitting layer formed on the opposite side of the transparent electrode layer from the light transmissive substrate, the relaxation layer has a high refractive index of the layer on the transparent electrode layer side and a refractive index of the layer on the light scattering portion side. A surface light-emitting body, which is formed in a multilayer structure having two or more layers having a low thickness, and the refractive index of the layer closest to the transparent electrode layer is the same as or lower than the refractive index of the transparent electrode layer.   A light scattering part formed on the surface of the translucent substrate, a relaxation layer formed on the surface of the light scattering part, for smoothening the surface roughness of the light scattering part, a transparent electrode layer formed on the surface of the relaxation layer, In a surface light emitter having a light emitting layer formed on the opposite side of the transparent electrode layer from the light-transmitting substrate, the relaxation layer has a low refractive index of the layer on the transparent electrode layer side and a refractive index of the layer on the light scattering portion side. A surface light-emitting body, which is formed in a multilayer structure having two or more layers having a high refractive index, and the refractive index of the layer closest to the transparent electrode layer is equal to or higher than the refractive index of the transparent electrode layer.   A step of forming a light scattering portion on the surface of the light-transmitting substrate, a step of coating a resin on the surface of the light scattering portion and heating and curing the coating resin to form a relaxation layer, and a transparent on the surface of the relaxation layer A step of forming an electrode layer, a step of changing the refractive index of the relaxation layer in the thickness direction inside the layer by heat treatment at a temperature higher than the curing temperature of the coating resin of the relaxation layer, A method of manufacturing a surface light emitter, comprising sequentially performing a step of forming a light emitting layer on a surface.   The material component of the relaxation layer and the material component of the transparent electrode layer are diffused and mixed in the heat treatment step so that the refractive index of the relaxation layer changes in the thickness direction in the layer. Item 6. A method for producing a surface light emitter according to Item 5.

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