JP2010114026A - El element, and el display device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element capable of realizing high light extraction efficiency by a simple constitution, and an easy manufacturing method. <P>SOLUTION: This is the EL element in which an optical sheet to satisfy the following conditions is installed at an either position on a light-emitting layer 24c side than a face from which light is extracted toward outside of the EL element 21, and on the viewing side than a face of a light emitting side of a light transmissive electrode 25. a. When out of light incident to the optical sheet, parallel transmissivity against light incident from the normal line direction of the sheet face is made To, and the parallel transmissivity against light incident from a direction inclined to the sheet by 45° in a state that both sheet faces are pinched by two sheets of right angle reflecting prism slope is made Tα, a value of Tα/To is 0.6 or less. b. As for the optical sheet, flat particles of which the average aspect ratio is 2 or more are dispersed in a transparent resin, and the average value of the smaller angle made by a long axis direction of the particles and the sheet face direction in two cross-sections perpendicular to the sheet face is within 30°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an EL element provided with an optical sheet and an EL display device using the same.

  In recent years, with the diversification of information equipment, the need for a surface light-emitting element with low power consumption and a small volume has increased, and as one of such surface light-emitting elements, an electroluminescence element (hereinafter abbreviated as EL element) is used. Attention has been paid. Such EL elements are roughly classified into inorganic EL elements and organic EL elements depending on the materials used.

  Here, the inorganic EL element generally applies a high electric field to the light emitting portion, accelerates electrons in the high electric field to collide with the light emission center, thereby exciting the light emission center to emit light. On the other hand, an organic EL element combines an electron and a hole from an electron injection electrode and a hole injection electrode in a light emitting layer to bring the organic material into an excited state, and emits light when the organic material returns from the excited state to the ground state. As compared with the inorganic EL element, there is an advantage that it can be driven at a lower voltage. Taking advantage of the fact that it emits light on its surface, it is expected to be used for thin displays and lighting applications.

  However, when a surface light emitting element such as an EL element emits light, the light emitted inside the light emitting layer having a high refractive index travels in various directions and is totally reflected on the light emitting surface of the surface light emitting element. There is also a lot of light confined inside the light emitting element. In general, only 20% to 30% of the light emitted from the surface light emitting device can be taken out of the surface light emitting device, and sufficient brightness cannot be obtained. In particular, in the case of an organic EL element, there is also a problem that the lifetime of the element is shortened if the brightness is compensated by the magnitude of the current.

  In order to solve such a problem, a technique in which a layer containing diffusing particles is provided at any position on the light emitting surface side of an EL element has been conventionally known. However, with a configuration in which only a diffusing layer is provided, a sufficient light extraction effect cannot be obtained, and the front luminance decreases due to a scattering phenomenon with respect to light emitted toward the front side of the viewing side. Will occur. For such a problem, among the light emitted from the EL element, the light emitted toward the front side of the viewing side hardly scatters and is large for light traveling at an angle greater than the critical angle. Disclosure of optical technology that imparts scattering and enhances light extraction efficiency has been made (see, for example, Patent Documents 1 to 5).

  However, in the above-mentioned Patent Document 1, there is a reference to the relationship between the refractive index of the resin and the scatterer contained in the resin, and the birefringent resin or the like. There is no detailed description of the implementation of the structure, such as the material of the scatterer and the method of aligning the orientation of each birefringent scatterer. In Patent Document 1, as an example in which the shape of the scatterer has anisotropy, a configuration in which the elongated scatterer is oriented so as to stand in the thickness direction of the diffusion layer is described. If there is no description and this configuration is applied to an EL display device as it is, pixel blurring becomes large, resulting in a stunning image. Patent Documents 2 and 3 describe a structure having a refractive index distribution in the thickness direction, for example, a field of view such as Sumitomo Chemical's Lumisty as a concept of a structure that gives large scattering to light traveling at an angle greater than the critical angle. Although a film having control characteristics is mentioned, the definition of the refractive index distribution is unknown, and in addition, the visibility control film of Rumisty's type varies in the magnitude of scattering depending on the angle of incidence on the film from the air Therefore, even if this is applied to an EL device structure, it does not always function effectively for light above the critical angle, but rather scatters significantly for relatively high angle incident light within the critical angle range. As a result, the front luminance is reduced. Also in Patent Documents 4 and 5, as the evaluation of the configuration that gives large scattering to light traveling at an angle greater than the critical angle, in the same way as the visibility control films listed in Patent Documents 2 and 3, the light is directly incident on the film. Only the way the scattering characteristics change according to the angle to be taken is not sufficient as the light extraction efficiency. Further, in Patent Documents 4 and 5, a holographic diffusion sheet is cited as a specific configuration, but the manufacturing method itself is complicated, and when this is applied to an EL display device, this is performed for each pixel. Such a structure must be provided on the light emitting element, which is very expensive.

Patent Documents 6 and 7 both disclose a configuration in which a layer containing particles in which mica is coated with titanium dioxide is provided on the surface of the EL element, but there is no description of the shape characteristics of the particles. In addition, particles having a particle diameter of 10 μm or more were used, and no function exceeding the light extraction effect of a simple diffusion film was observed. Further, in this configuration, when used as an EL display device, the level is a problem in terms of image bleeding.
Patent No. 4083812 Japanese Patent No. 4104339 JP 2003-208974 A Japanese Patent No. 3750563 JP 2004-95541 A JP-A-9-245966 Japanese Patent Laid-Open No. 11-214158

  The first object of the present invention is to provide an EL element capable of realizing high light extraction efficiency with a simple structure and an easy manufacturing method, and an EL display device having high luminance and less image blur using the EL element. The second purpose is to provide it.

  The above object of the present invention is achieved by the following configurations.

  1. A light-emitting layer is provided between a pair of electrodes opposed to each other on the substrate, and at least one of the pair of electrodes is a light-transmitting electrode. Light is extracted toward the outside of the EL element. An EL sheet that is provided with an optical sheet satisfying both of the following conditions a and b at any position on the light emitting layer side of the surface and on the viewing side of the light emitting side surface of the light transmissive electrode. element.

  a. Of the light incident on the optical sheet, the parallel transmittance with respect to the light incident from the normal direction of the sheet surface is To, and the both surfaces of the sheet are sandwiched between two right-angle reflecting prism inclined surfaces. On the other hand, when the parallel transmittance with respect to light incident from a direction inclined by 45 ° is Tα, the value of Tα / To is 0.6 or less.

  b. The optical sheet has a configuration in which flat particles having an average aspect ratio of 2 or more are dispersed in a transparent resin, and the major axis direction of the particles in two cross sections perpendicular to the sheet surface and the sheet surface direction. The average value of the smaller angles formed is within 30 °.

  2. 2. The EL element according to 1 above, wherein a distance from a light emitting side surface of the light transmissive electrode to a viewing side surface of the optical sheet is 200 μm or less.

  3. 3. The EL device according to 1 or 2, wherein the average particle size of the flat particles is less than 10 μm, and the average aspect ratio of the flat particles is 5 or more.

  4). 4. The EL device according to any one of 1 to 3, wherein the flat particles have an average particle size of 5 μm or less and an average thickness of 0.5 μm or less.

  5. Of the light incident on the optical sheet, the value of Tβ / To is 0.65 or more, where Tβ is the parallel transmittance for light incident from a direction inclined by 40 ° with respect to the normal of the sheet surface. 5. The EL device according to any one of 1 to 4 above, wherein

  6). 6. The EL element according to any one of 1 to 5, wherein an average refractive index difference between the transparent resin constituting the optical sheet and the flat particles is 0.06 or more.

  7). 7. An EL display device using the EL element according to any one of 1 to 6 above.

  According to the present invention, it is possible to provide an EL element capable of realizing high light extraction efficiency with a simple configuration and an easy manufacturing method. Further, an EL display device with high luminance and less image blur can be provided using the EL element.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  An EL element of the present invention includes a pair of electrodes opposed to each other on a substrate and a light emitting layer between the electrodes, and at least one of the pair of electrodes is a light transmissive electrode. An optical sheet satisfying both of the following conditions a and b is provided at any position on the light emitting layer side from the surface from which light is extracted toward the light emitting side of the light transmissive electrode and on the viewing side. With such a configuration, an EL element capable of realizing high light extraction efficiency with a simple configuration and an easy manufacturing method is provided.

  a. Of the light incident on the optical sheet, the parallel transmittance with respect to the light incident from the normal direction of the sheet surface is To, and the both surfaces of the sheet are sandwiched between two right-angle reflecting prism inclined surfaces. On the other hand, when the parallel transmittance with respect to light incident from a direction inclined by 45 ° is Tα, the value of Tα / To is 0.6 or less.

  b. The optical sheet has a configuration in which flat particles having an average aspect ratio of 2 or more are dispersed in a transparent resin, and the major axis direction of the particles in two cross sections perpendicular to the sheet surface and the sheet surface direction. The average value of the smaller angles formed is within 30 °.

  Hereinafter, the present invention will be described in detail.

(Scattering characteristics of optical sheet according to the present invention)
In the optical sheet of the present invention, the parallel transmittance with respect to light incident from the normal direction of the sheet surface out of the light incident on the sheet is To, and both surfaces of the sheet are sandwiched between two right-angled triangular prism inclined surfaces. In this state, the value of Tα / To is 0.6 or less, where Tα is the parallel transmittance with respect to light incident from a direction inclined by 45 ° with respect to the sheet.

  Here, the parallel transmittances To and Tα of the optical sheet according to the present invention are values measured by the following method. That is, the optical sheet portion is peeled off from the organic EL element in advance, and this is shown in FIG. Set to an optical system schematically represented in A, for example, a commercially available haze meter such as a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. That is, the parallel transmittance To is measured. Next, FIG. As shown in B, two commercially available 45 ° right-angle reflecting prisms were prepared, and the optical functional layer was bonded between the inclined surfaces of the triangular prism via an adhesive layer so that bubbles would not be mixed as much as possible. Set in the optical system, light is applied from an angle inclined by 45 ° from the normal of the optical sheet, and the parallel transmittance measurement value Tα at that time is measured. In the optical sheet according to the present invention, the value of Tα / To is 0.6 or less, preferably 0.001 or more and 0.5 or less, from the viewpoint of enhancing the light extraction effect.

  Further, the optical sheet according to the present invention has Tβ / when the parallel transmittance with respect to light incident from the direction inclined by 40 ° with respect to the normal of the sheet surface is Tβ. The value of To is preferably 0.65 or more from the viewpoint of enhancing the light extraction effect. The value of Tβ means a value of parallel transmittance obtained when the optical sheet is measured in a state inclined by 40 ° with respect to incident light in FIG. 1A. The value of Tβ / To is preferably 0.65 or more and 0.99 or less, and more preferably 0.7 or more and 0.99 or less.

  The values of Tα / To and Tβ / To are the thickness and particle size of the flat particles constituting the optical sheet, the ratio of the number of flat particles in the total number of scatterers contained in the sheet, flat particles and transparent resin Can be easily controlled by changing the refractive index difference, the scatterer density, the thickness of the optical sheet, etc. alone or in combination as appropriate.

(Configuration of optical sheet according to the present invention)
The optical sheet according to the present invention has a configuration in which flat particles are dispersed in a transparent resin. The density of the flat particles contained in the sheet is generally determined by the relationship between the detailed shape of each particle, the refractive index determined by the material, and the refractive index of a transparent resin that functions as a binder for the particles. However, the volume ratio is preferably 0.03% to 50%, and more preferably 0.1% to 30%.

  The thickness of the sheet is not particularly limited as long as it is equal to or greater than the thickness of the flat particles contained in the sheet, but is preferably approximately 0.2 μm to 150 μm, preferably 0.5 μm to 80 μm. Is more preferable, and most preferably 1 μm or more and 40 μm or less.

(Flat particles used in the present invention)
The flat particles used in the present invention are particles having short characteristics in at least one direction when an orthogonal three-dimensional coordinate system is applied to the three-dimensional shape of the particles, and are apparently elliptical, including a disk, Various shapes such as a polygonal flat plate represented by a square shape or a hexagonal shape, and a rod shape are used.

  The optical sheet according to the present invention is characterized in that flat particles having an average aspect ratio of 2 or more are dispersed in a transparent resin. In the present invention, the aspect ratio refers to the ratio of the particle diameter to the thickness (aspect ratio = diameter / thickness). The particle size referred to in the present invention is perpendicular to the circumscribed or inscribed surface of the plane (hereinafter referred to as the main surface) having the largest area among the flat surfaces or curved surfaces forming the surface of the flat particles. It is represented by the diameter of a circle equal to the area (projected area) when the particles are projected. The grain thickness is defined as the longest grain thickness in a direction perpendicular to the major surface.

  The particle size and thickness are determined by the following method when the particles are solid. From the optical sheet previously peeled off from the EL element, the binder resin is removed by a method such as dissolution to extract only the particles. A sample is prepared by coating this on a support together with a latex ball having a known particle size as an internal standard, shadowing is performed by a carbon vapor deposition method from a certain angle, and then a replica sample is prepared by a normal replica method. An electron micrograph of the sample is taken, and the projected area and thickness of each particle are obtained using an image processing apparatus or the like. In this case, the projected area of the particle can be calculated from the projected area of the internal standard, and the thickness of the particle can be calculated from the length of the internal standard and the shadow of the particle. In the present invention, the average values of the aspect ratio, the particle size, and the particle thickness are values obtained by arbitrarily measuring 300 or more particles using the shadowing method and calculating the arithmetic average thereof. Further, when the particles are gas or liquid, the optical sheet is continuously cut out in an ultrathin film shape, and is three-dimensionalized by image processing of an electron microscope image, and then the particle diameter and thickness can be obtained.

  In the present invention, the average aspect ratio of the flat particles is 2 or more, but is preferably 5 or more. The average particle size of the flat particles used in the present invention is preferably less than 10 μm, more preferably 0.1 μm to 8 μm, and particularly preferably 0.1 μm to 5 μm. The average thickness of the flat particles used in the present invention is preferably 2 μm or less, more preferably 1 μm or less, and most preferably 0.5 μm or less.

  The flat particles used in the present invention may be any of an inorganic substance, an organic substance, and an organic / inorganic composite, and the state of the substance is not limited to a solid, and may be a liquid or a gas. As an example of the flat particles being liquid, for example, in a thermoplastic resin such as polyethylene terephthalate (hereinafter abbreviated as PET), a UV absorbing compound that shows a liquid state at room temperature and has low compatibility with PET is dispersed. Examples thereof include a biaxially stretched sheet after film formation by a melt extrusion method together with PET. Since the dispersion composed of each UV-absorbing compound after biaxial stretching follows the surrounding PET, the shape expands in the plane direction, and thus becomes a flat dispersion. By selecting the type of UV absorbing compound so that the difference in average refractive index between PET and UV absorbing compound is 0.02 or more and controlling the draw ratio, an optical sheet exhibiting the scattering characteristics aimed by the present invention can be obtained. it can. Further, as an example of the flat particles being gas, for example, in PET, inorganic particles having almost no difference in average refractive index from PET are added, and after the film formation by the melt extrusion method together with PET, Examples include a stretched sheet. By biaxially stretching PET, fine voids starting from the interface between each inorganic particle and PET are formed into flat particles. As the inorganic particles to be added, those having a refractive index close to that of PET as a dispersion medium are selected, so that there is no optical effect. By controlling the size, addition concentration, and stretch ratio of the inorganic particles, an optical functional film that exhibits the scattering characteristics targeted by the present invention can be obtained.

  Next, specific examples of the flat particles used in the present invention are shown. Inorganic flat particles include mica such as mascobite, phlogopite, biotite, sericite, and phlogopite (artificial mica). , Kaolin (clay), talc (talc), montmorillonite, etc., flaky aluminum oxide / titanium oxide / zinc oxide / silicon oxide and composites of these, flat calcium carbonate, etc. Silver halides such as silver chloride, silver bromide, silver iodide, silver iodobromide, silver bromochloride, silver iodochloride and silver iodobromochloride whose shape is controlled are used.

  Examples of mica include A-11, A-21, A-41, AB-25S, SYA-21R, SYA-41R, SJ-005, SJ-010, CS-325DC, Y-manufactured by Yamaguchi Mica Industry. 1800, Y-2300X, Y-2400, Y-3000, SA-310, SA-350, FA-450, NCC-322, NCF-322, TM-10, TM-20, etc., Micro Mica manufactured by Coop Chemical MK-100F, S1MK, MK-100, MK-200, MK-300, Sofushima ME-100, MAE, MTE, MEE, and MPE manufactured by the same company are used.

  Examples of smectites such as kaolin and talc include FK-500S, FK-300S, and CT-35 manufactured by Yamaguchi Mica Industry Co., Ltd., Lucentite SWN, SWF, SAN, SAN316, and STN manufactured by Corp Chemical. , SEN, SPN and the like.

  Examples of the flaky aluminum oxide include Seraph YFA00610, 02025, 02050, 05025, 05025, 05070, 07070, and 10030 manufactured by Kinsei Matech, and Luxelen FAO manufactured by Asahi Chemical Industry.

  Examples of the flaky titanium oxide include luxelenium silk D, H, UV, luxelenium PC, and ODT manufactured by Asahi Chemical Industry.

  Examples of the flaky zinc oxide include Luxelene FZT manufactured by Asahi Chemical Industry.

  Examples of the flaky silicon oxide include Chemiselen manufactured by Asahi Chemical Industry, SG flake manufactured by Nippon Sheet Glass Co., Ltd., TSG9, TSG30, NTS30K3TA, NPT30K3TA, and the like.

  As the flat calcium carbonate, those made by New Lime Co., such as hexagonal plates, discs, and scales are used.

  Examples of the organic flat particles include polyamide-based, polyester-based, polyether-based, polysulfide-based, polyolefin-based, and fluororesin, which are made by using a manufacturing method disclosed in JP-A-11-199706. Or a polyvinyl alcohol-based one is used.

  As a special shape of the flat particles, rod-shaped particles can be mentioned. When using rod-shaped particles, it is important that the major axis is oriented in the plane direction of the optical sheet according to the present invention. When viewed from a direction perpendicular to the sheet surface, each rod-shaped particle has a specific direction. It is preferable that the film is not oriented. Moreover, not only the case where it is dispersed as a single rod-like particle alone, but also those in which a plurality of rod-like particles aggregate to form a flat particle group are preferably used. Specifically, in order to increase the affinity with various resins used as a particle binder described later in any of the above-mentioned flat particles of inorganic, organic, or composite type, various known surface modifiers / methods Can be used for surface treatment.

(Transparent resin used in the present invention)
The transparent resin used in the present invention is preferably a material that is substantially transparent in the visible light region. Specifically, for example, cellulose ester resins such as triacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin polymer, crosslinked polyethylene resin, polychlorinated resin Amorphous thermoplastic resins such as vinyl resin, polyarylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyetherimide resin, polysulfone resin, polyether ketone resin, polyethylene terephthalate, polyethylene resin, polypropylene resin, polybutylene terephthalate Crystalline thermoplastic resins such as aromatic polyester resins, polyacetal resins, and polyamide resins can be used. Furthermore, an acrylic, epoxy, urethane, or other ultraviolet curable resin or thermosetting resin may be applied to the thermoplastic resin substrate or glass substrate together with the flat particles described above. preferable.

(Relationship between refractive index of transparent resin and flat particles)
The refractive index relationship between the transparent resin and the flat particles used in the present invention preferably has an average refractive index of 0.02 or more and 1.0 or less. Here, with respect to the average refractive index, in terms of transparent resin, the refractive index of the resin part forming the optical sheet of the present invention in the two axial directions is Nmx and Nmy, and the refractive index in the thickness direction of the resin part is This means Nmav defined by the following formula (1) when Nmz, and in the case of flat particles, the biaxial refractive indexes on the tangential surface with respect to the main surface are Ndx and Ndy, and the refractive index in the thickness direction of the particles Ndav defined by the following formula (2) where Ndz is Ndz.

Nmav = (Nmx + Nmy + Nmz) / 3 Formula (1)
Ndav = (Ndx + Ndy + Ndz) / 3 Formula (2)
Δn = | Nmav−Ndav | Equation (3)
Δn defined by is preferably 0.02 or more and 1.0 or less, more preferably 0.04 or more and 0.9 or less, and 0.06 or more and 0.7 or less in order to obtain excellent scattering characteristics. Is more preferable. Nmx, Nmy, and Nmx may be substantially optically isotropic with a difference of 0.02 or less, and Nmx is 0.05 or more smaller than Nmx or Nmy, or 0.05 or more. Although it may be large, the difference between Nmx and Nmy is preferably 0.05 or less, and more preferably 0.02 or less. On the other hand, Ndx, Ndy, and Ndz may be substantially optically isotropic with a difference of 0.02 or less, or Ndz is 0.05 or more smaller than Ndx or Ndy, or 0. The difference between Ndx and Ndy is preferably 0.05 or less, and more preferably 0.02 or less. The relationship between Nmx, Nmy and Ndx, Ndy is preferably used without any special restrictions as long as Δn represented by Equation (3) satisfies the relationship of 0.02 to 1.0. Alternatively, the difference between Nmy and Ndx or Ndy is preferably 0.03 or less. The relationship between Nmz and Ndz is preferably 0.05 or more and 1.0 or less.

  The refractive index of the transparent resin and the flat particles of the optical sheet used in the present invention can be roughly estimated from the manufacturer's catalog value if the bulk refractive index values of the compounds constituting them are examined, or commercially available. it can. In actual measurement, a transparent resin sheet not containing flat particles is prepared in advance, and then measured using, for example, an Abbe refractometer DR-M2 manufactured by Atago Co., Ltd. The refractive index of the flat particles can be measured using the Becke method. That is, it is possible to determine the refractive index of a particle by preparing several immersion liquids having different refractive indexes and observing the presence or absence of a Becke line when the particle is immersed therein.

(Orientation of flat particles)
The orientation of the flat particles in the optical sheet according to the present invention is preferably such that the thickness direction of the sheet is substantially parallel to the flat direction of the individual flat particles. In other words, it is preferable that the major axis direction of the particles in the two vertical and horizontal cross sections perpendicular to the sheet surface is substantially parallel to the surface direction of each cross section. Here, the major axis direction of the particle in the cross section perpendicular to the sheet surface means the direction connecting the two longest points of the distance between the two points on the outer periphery in the particle cross section surrounded by the closed curve or the closed straight line. And The orientation of the flat particles in the optical sheet according to the present invention is such that the average of the smaller angle between the major axis direction of the particle cross section and the sheet surface direction is within 30 ° in two vertical and horizontal cross sections perpendicular to the sheet surface. It is characteristic that it is within 20 °.

  As a method for realizing the preferred orientation, flat particles having a high average aspect ratio are selected, or a solution containing flat particles having a high viscosity at the time of forming a sheet is prepared. There are various methods such as applying a strong shearing force in the direction, or increasing the time from drying to solidification after containing a large amount of solvent immediately after coating. These methods can be used alone or in combination as appropriate. Can be realized. In other words, for example, flat particles that are not sufficiently stably oriented in the solidified layer by applying a coating solution containing a solvent, a UV curable resin, and flat particles with a wire bar and then immediately irradiating with UV. It is possible to produce a sheet containing Also in wire bar coating, good orientation can be obtained by taking sufficient time from drying after coating to solidification by UV irradiation. Also, the spin coating method is preferable because it can easily form a preferred orientation of flat particles.

(Method for producing optical sheet according to the present invention)
The optical sheet manufacturing method of the present invention is not particularly limited, but as a guide, when forming a sheet having a thickness of about 30 μm or more, a film forming method such as a solution casting method or a melt extrusion method, or a film forming method therefor Thereafter, a method of appropriately stretching and thinning the film is preferably used. When forming a sheet with a thickness of less than about 30 μm, vapor deposition, casting, gravure coating, comma coating, bar coating, die coating, lip coating, roll coating, flow coating, print coating, dip coating, spin A coating method such as a coat, a production method by printing, an ink jet method or the like is preferably used. In particular, the spin coating method is preferred for controlling the orientation of the flat particles.

(Arrangement position of optical sheet according to the present invention)
The arrangement position of the optical sheet according to the present invention is at any position on the light emitting layer side from the surface from which light is extracted toward the outside in the EL element and on the viewing side from the light emitting surface side of the light transmissive electrode. is there. Here, the surface from which light is extracted toward the outside world refers to a surface that is positioned closest to the viewing side of the EL element. In the configuration of the EL element, after the light from the light emitting layer passes through the light transmissive electrode, passes through the transparent substrate, and reaches the viewing side, the transparent substrate on the side opposite to the surface where the light transmissive electrode is located. The configuration in which the optical sheet of the present invention is provided on the surface and the surface of the optical sheet opposite to the transparent substrate is an external air layer is outside the scope of the present invention. That is, it is important that the optical sheet of the present invention is sandwiched between members whose refractive index is generally greater than 1. The optical sheet of the present invention may be provided between the viewing side surface of the light transmissive electrode and the surface of the transparent substrate on the light transmissive electrode side.

  When the EL element of the present invention is used as an image display device, it is necessary to consider image bleeding. In order to suppress image blur as much as possible, it is preferable to place the optical sheet at a position that is not a surface from which light is extracted toward the outside, that is, a position that is not the outermost surface on the viewing side, and a position that is relatively close to the light transmissive electrode. More preferably. In this case, as a standard of the distance from the viewing side surface of the light transmissive electrode to the viewing side surface of the optical sheet of the present invention, 0.2 μm or more and 200 μm or less is preferable, 0.5 μm or more and 100 μm or less is more preferable, and 1 μm or more and 50 μm or less. Is most preferred.

<< Configuration of EL Element of the Present Invention >>
Next, the configuration of the EL element of the present invention will be described. The technique of the present invention can be applied to any organic / inorganic EL element, but here, the organic EL element will be mainly described as a representative. FIG. 2 is a cross-sectional view schematically showing an example of the EL element of the present invention. The EL element 21 shown in this figure has a structure in which an anode 23, an organic layer 24, and a cathode 25 are laminated in this order on a substrate 22. Among these, the organic layer 24 has a configuration in which, for example, a hole injection layer 24a, a hole transport layer 24b, a light emitting layer 24c, and an electron transport layer 24d are stacked in this order from the anode 23 side. In the following, it is assumed that the EL element 21 having such a stacked configuration is configured as a so-called top emission type element that extracts light from the side opposite to the substrate 22, and details of each layer in this case are sequentially described from the substrate 22 side. explain.

<Board>
The substrate 22 is a support on which the EL elements 21 are arranged and formed on one surface thereof, and may be a known substrate, such as quartz, glass, metal foil, or a resin film or sheet. Of these, quartz and glass are preferred, and in the case of resin, methacrylic resins represented by polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene Although polyesters, such as a phthalate (PBN), or polycarbonate resin is mentioned, it is necessary to perform the laminated structure and surface treatment which suppress water permeability and gas permeability.

<Anode>
The anode 23 has a high work function from the vacuum level of the electrode material in order to inject holes efficiently, for example, aluminum (Al), chromium (Cr), molybdenum (Mo), tungsten (W), copper (Cu), silver (Ag), gold (Au) metals and alloys thereof, oxides of these metals and alloys, alloys of tin oxide (SnO ₂ ) and antimony (Sb), ITO (indium) Tin oxide), InZnO (indium zinc oxide), alloys of zinc oxide (ZnO) and aluminum (Al), and oxides of these metals and alloys are used alone or in a mixed state.

  Further, the anode 23 may have a laminated structure of a first layer having excellent light reflectivity and a second layer having a light transmittance and a large work function provided on the upper layer.

  The first layer is made of an alloy containing aluminum as a main component. The subcomponent may include at least one element having a work function relatively smaller than that of aluminum as a main component. As such a subcomponent, a lanthanoid series element is preferable. Although the work function of the lanthanoid series elements is not large, the inclusion of these elements improves the stability of the anode and also satisfies the hole injection property of the anode. In addition to lanthanoid series elements, elements such as silicon (Si) and copper (Cu) may be included as subcomponents.

  The content of subcomponents in the aluminum alloy layer constituting the first layer is preferably about 10% by mass or less in total if it is Nd, Ni, Ti, or the like that stabilizes aluminum. Thereby, while maintaining the reflectance in the aluminum alloy layer, the aluminum alloy layer can be stably maintained in the manufacturing process of the organic electroluminescent element, and further, processing accuracy and chemical stability can be obtained. In addition, the conductivity of the anode 23 and the adhesion to the substrate 22 can be improved.

  Examples of the second layer include a layer made of at least one of an oxide of an aluminum alloy, an oxide of molybdenum, an oxide of zirconium, an oxide of chromium, and an oxide of tantalum. Here, for example, when the second layer is an oxide layer of an aluminum alloy containing a lanthanoid element as a subcomponent (including a natural oxide film), the oxide of the lanthanoid element has a high transmittance, so that this is included. The transmittance of the second layer is improved. For this reason, it is possible to maintain a high reflectance on the surface of the first layer. Further, the second layer may be a transparent conductive layer such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). These conductive layers can improve the electron injection characteristics of the anode 23.

  The anode 23 may be provided with a conductive layer for improving the adhesion between the anode 23 and the substrate 22 on the side in contact with the substrate 22. Examples of such a conductive layer include transparent conductive layers such as ITO and IZO.

  When the driving method of the display device configured using the EL element 21 is an active matrix method, the anode 23 is patterned for each pixel and connected to a driving thin film transistor provided on the substrate 22. It is provided in the state. In this case, although not shown here, an insulating film is provided on the anode 23, and the surface of the anode 13 of each pixel is exposed from the opening of the insulating film. And

<Hole injection layer / hole transport layer>
The hole injection layer 24a and the hole transport layer 24b are for increasing the efficiency of hole injection into the light emitting layer 24c. Examples of the material for the hole injection layer 24a or the hole transport layer 24b include benzine, styrylamine, triphenylamine, porphyrin, triphenylene, azatriphenylene, tetracyanoquinodimethane, triazole, imidazole, and oxadiazole. , Polyarylalkanes, phenylenediamines, arylamines, oxazoles, anthracenes, fluorenones, hydrazones, stilbenes or their derivatives, or heterocyclic conjugated systems such as polysilane compounds, vinylcarbazole compounds, thiophene compounds or aniline compounds Monomers, oligomers or polymers of can be used.

  Further, as specific materials for the hole injection layer 24a or the hole transport layer 24b, α-naphthylphenylphenylenediamine, porphyrin, metal tetraphenylporphyrin, metal naphthalocyanine, hexacyanoazatriphenylene, 7, 7, 8 , 8-tetracyanoquinodimethane (TCNQ), 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4-TCNQ), tetracyano 4,4,4-tris ( 3-methylphenylphenylamino) triphenylamine, N, N, N ′, N′-tetrakis (p-tolyl) p-phenylenediamine, N, N, N ′, N′-tetraphenyl-4,4′- Diaminobiphenyl, N-phenylcarbazole, 4-di-p-tolylaminostilbene, poly (paraphenyle Vinylene), poly (thiophene vinylene), poly (2,2'-thienylpyrrole), and including without being limited thereto.

<Light emitting layer>
The light emitting layer 24c is a region where emitted holes are generated by recombination of holes injected from the anode 23 side and electrons injected from the cathode 25 side. Such a light emitting layer 24c may be an organic thin film formed of an organic material composed only of carbon and hydrogen, and is configured using a material having a tertiary amine having a hole transporting property in a molecular structure. It may be a layer formed. In addition, the light emitting layer 24c may be a mixed organic thin film containing a trace amount of an organic substance such as a berylene derivative, a coumarin derivative, a pyran dye, or a triphenylamine derivative as a dopant. In this case, the light emitting layer 24c is formed by co-evaporation of the host material (main material) constituting the light emitting layer 24c and the material to be the dopant. In particular, a material having a tertiary amine having a hole transporting property in the molecular structure has a characteristic that the intermolecular interaction is small and the concentration quenching is difficult, so that high concentration doping is possible and optimum. Functions as one of the dopants.

  The material constituting the light emitting layer 24c as described above can be selected according to a desired color. For example, when it is desired to obtain blue light emission, oxadiazole derivatives, cyclopentadiene derivatives, pyrazoloquinoline derivatives, distyrylarylene derivatives, oligothiophene derivatives, and the like are used. In order to obtain green light emission, a layer obtained by doping a blue light-emitting layer with a known green pigment such as a coumarin derivative such as coumarin 6 or a quinacridone derivative is used. In order to obtain red light emission, neil red, DCM1 {4- (dicyanomethylene) -2-methyl-6 (p-dimethylaminostyryl) -4H-pyran} is added to the light emission layer of blue or green light. , DCJT {4- (dicyanomethylene) -2-t-butyl-6- (julolidylstyryl) -pyran} and other known red pigments such as pyran derivatives, squarylium derivatives, porphyrin derivatives, chlorin derivatives, eurodiline derivatives, etc. Doped layers are used.

  The light emitting layer 24c may be a white light emitting layer in which a red light emitting layer, a green light emitting layer, and a blue light emitting layer are laminated, and has a tandem structure in which a plurality of light emitting layers are laminated through a connection layer. Also good. Furthermore, the light emitting layer 24c may be an electron transporting light emitting layer that also serves as an electron transporting layer, or may be a hole transporting light emitting layer.

<Electron transport layer>
The electron transport layer 24d is for transporting electrons injected from the cathode 25 to the light emitting layer 24c. Examples of the material for the electron transport layer 24d include quinoline, perylene, phenanthroline, bisstyryl, pyrazine, triazole, oxazole, oxadiazole, fluorenone, and derivatives or metal complexes thereof. Specifically, tris (8-hydroxyquinoline) aluminum (abbreviated as Alq ₃ ), anthracene, naphthalene, phenanthrene, pyrene, anthracene, perylene, butadiene, coumarin, acridine, stilbene, 1,10-phenanthroline, or a derivative or metal thereof A complex.

  The organic layer 24 is not limited to such a layer structure, and it is sufficient that at least the light emitting layer 24c and the electron transport layer 24d are provided in contact therewith. You can choose.

  In addition, the light emitting layer 24c may be provided in the EL element 21 as a hole transporting light emitting layer, an electron transporting light emitting layer, or a charge transporting light emitting layer. Furthermore, each layer constituting the organic layer 24, for example, the hole injection layer 24a, the hole transport layer 24b, the light emitting layer 24c, and the electron transport layer 24d may have a laminated structure including a plurality of layers.

<Cathode>
Next, the cathode 25 provided on the organic layer 24 having such a configuration has, for example, a two-layer structure in which a first layer 25a and a second layer 25b are stacked in this order from the organic layer 24 side.

The first layer 25a is formed using a material having a small work function and good light transmittance. Examples of such materials include lithium oxide (Li ₂ O), which is an oxide of lithium (Li), cesium carbonate (Cs ₂ CO ₃ ), which is a composite oxide of cesium (Cs), and oxidation of these materials. Mixtures of oxides and composite oxides can be used. The first layer 25a is not limited to such a material. For example, alkaline earth metals such as calcium (Ca) and barium (Ba), alkali metals such as lithium and cesium, and indium ( In), magnesium (Mg), and other metals having a low work function, and oxides and composite oxides, fluorides, and the like of these metals alone or these metals, oxides and composite oxides, You may use it, improving stability as a mixture or an alloy.

  The second layer 25b is formed of a thin film using a light-transmitting layer such as MgAg. The second layer 25b may be a mixed layer containing an organic light emitting material such as an aluminum quinoline complex, a styrylamine derivative, or a phthalocyanine derivative. In this case, a layer having optical transparency such as MgAg may be additionally provided as the third layer.

  When the driving method of the display device using the EL element 21 is the active matrix method, the cathode 25 is composed of the organic layer 24 and the above-described insulating film not shown here. Thus, a solid film is formed on the substrate 22 while being insulated from the anode 23, and is used as a common electrode of each pixel.

  Needless to say, the cathode 25 is not limited to the laminated structure as described above, and an optimum combination and laminated structure may be adopted according to the structure of the device to be manufactured. For example, the configuration of the cathode 25 of the above embodiment includes an inorganic layer (first layer 25a) that promotes functional separation of each electrode layer, that is, electron injection into the organic layer 24, and an inorganic layer (second layer 25b) that controls the electrode. Is a laminated structure in which and are separated. However, the inorganic layer that promotes electron injection into the organic layer 24 may also serve as the inorganic layer that controls the electrodes, and these layers may be configured as a single layer structure. Moreover, it is good also as a laminated structure which formed transparent electrodes, such as ITO, on this single layer structure.

  The current applied to the EL element 21 configured as described above is normally a direct current, but a pulse current or an alternating current may be used. The current value and the voltage value are not particularly limited as long as the element is not destroyed. However, considering the power consumption and life of the organic electroluminescent element, it is desirable to emit light efficiently with as little electrical energy as possible.

Furthermore, although illustration is omitted here, the EL element 21 having such a configuration is used in a state of being covered with a protective layer (passivation layer) in order to prevent deterioration of the organic material due to moisture, oxygen, etc. in the atmosphere. It is preferable. The protective film includes silicon nitride (typically Si ₃ N ₄ ), silicon oxide (typically SiO ₂ ) film, silicon nitride oxide (SiNxOy: composition ratio X> Y) film, silicon oxynitride ( A SiOxNy: composition ratio X> Y) film, a thin film mainly composed of carbon such as DLC (Diamond like Carbon), a CN (Carbon Nanotube) film, or the like is used. These films are preferably single-layered or laminated. Among these, the protective layer made of nitride is preferably used because it has a dense film quality and has an extremely high blocking effect against moisture, oxygen, and other impurities that adversely affect the EL element 21.

  In the above embodiment, the present invention has been described in detail by exemplifying a case where the EL element is a top emission type. However, the EL element of the present invention is not limited to application to a top emission type, and can be widely applied to a configuration in which an organic layer having at least a light emitting layer is sandwiched between an anode and a cathode. Therefore, in order from the substrate side, the cathode, the organic layer, and the anode are laminated in sequence, and the electrode located on the substrate side (lower electrode as the cathode or anode) is made of a transparent material and located on the opposite side of the substrate The electrode (upper electrode as a cathode or anode) is made of a reflective material, so that it can be applied to a bottom emission type EL device in which light is extracted only from the lower electrode side.

  Furthermore, the EL element of the present invention may be an element formed by a pair of electrodes (anode and cathode) and an organic layer sandwiched between the electrodes. For this reason, it is not limited to what comprised only a pair of electrode and organic layer, and other components (for example, an inorganic compound layer and an inorganic component) coexist in the range which does not impair the effect of this invention. Is not to be excluded.

  On the other hand, in the case of a polymer organic layer formed of a polymer organic material, only the hole transport layer can be provided in the direction of the anode 23 around the light emitting layer 24c. The hole transport layer 24b is made of polyethylene dihydroxythiophene (PEDOT), polyaniline (PANI), or the like, and is formed on the anode 23 by an inkjet printing method or a spin coating method. Phenyl vinylene (PPV), soluble PPV, PPV with cyano group, polyfluorene, and the like can be used, and a color pattern can be formed by a general method such as an inkjet printing method, a spin coating method, or a thermal transfer method using a laser.

In the case of an inorganic electroluminescent element, the light emitting layer 24c is composed of an alkaline earth calcium sulfide such as ZnS, SrS, CaS, CaCa ₂ S ₄ , SrCa ₂ S ₄ , BaAl ₂ S ₄ , and Mn, Ce, Tb, Eu. , Transition metal containing Tm, Er, Pr, Pb, or the like, or an emission rare earth metal such as an alkali rare earth metal, and insulating between the anode 23 and the cathode 25 around the emission layer 24c. A layer is formed.

≪Schematic configuration of display device≫
3A and 3B are diagrams illustrating an example of the display device 10 according to the embodiment. FIG. 3A is a schematic configuration diagram, and FIG. 3B is a configuration diagram of a pixel circuit. Here, an embodiment in which the present invention is applied to an active matrix display device using the EL element 21 shown in FIG. 2 as a light emitting element will be described.

  As shown in FIG. 3A, a display area 2a and a peripheral area 2b are set on the substrate 2 of the display device 10. The display area 2a is configured as a pixel array section in which a plurality of scanning lines 11 and a plurality of signal lines 13 are wired vertically and horizontally, and one pixel a is provided corresponding to each intersection. Each pixel a is provided with an EL element 21. In the peripheral region 2b, a scanning line driving circuit b that scans and drives the scanning lines 11, and a signal line driving circuit c that supplies a video signal (that is, an input signal) corresponding to luminance information to the signal line 13 are arranged. Yes.

  As shown in FIG. 3B, the pixel circuit provided in each pixel a includes, for example, each EL element 21, a drive transistor Tr1, a write transistor (sampling transistor) Tr2, and a storage capacitor Cs. Then, the video signal written from the signal line 13 via the write transistor Tr2 is held in the holding capacitor Cs by driving by the scanning line driving circuit b, and a current corresponding to the held signal amount is sent from the drive transistor Tr1 to each EL. The EL element 21 is supplied to the element 21 and emits light with a luminance corresponding to the current value.

  Note that the configuration of the pixel circuit as described above is merely an example, and a capacitor element may be provided in the pixel circuit as necessary, or a plurality of transistors may be provided to configure the pixel circuit. In addition, a necessary drive circuit is added to the peripheral region 2b according to the change of the pixel circuit.

  The display device 10 described above includes a module-shaped one having a sealed configuration. For example, a sealing part 3 is provided so as to surround the display area 2a which is a pixel array part, and the sealing part 3 is used as an adhesive and is attached to an opposing part (sealing substrate) such as transparent glass. Applicable to modules. The transparent sealing substrate may be provided with a color filter, a protective film, a light shielding film, and the like. The substrate 21 as a display module in which the display area 2a is formed may be provided with a flexible printed board for inputting / outputting signals from / to the display area 2a (pixel array unit).

  According to the configuration of the embodiment described above, it is possible to improve the image quality in the display device 10 by using the EL element 21 with improved element characteristics. In particular, even if the EL element 21 is a top emission type that is advantageous for the active matrix type display device 10, the element characteristics can be improved. By configuring the matrix display device 10, it is possible to improve image quality in the display device 10 having a wide pixel aperture.

<Lighting device>
An illumination device to which the surface light emitter of the present invention is applied will be described.

  The EL element according to the present invention may be used as a kind of lamp such as an illumination or exposure light source, a projection device that projects an image, or a display device that directly recognizes a still image or a moving image. (Display) may be used. The driving method when used as a display device for moving image reproduction may be either a simple matrix (passive matrix) method or an active matrix method.

  In the white EL element used for this invention, you may pattern by a metal mask, the inkjet printing method, etc. at the time of film forming as needed. When patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire element layer may be patterned. There is no restriction | limiting in particular as a light emission dopant used for a light emitting layer, For example, if it is a backlight in a liquid crystal display element, platinum complex and a well-known light emission dopant will be adapted so that it may correspond to the wavelength range corresponding to CF (color filter) characteristic. Any one of them may be selected and combined for whitening.

  As described above, the white EL element according to the present invention is taken out from the organic EL element by combining the CF (color filter) and arranging the element and the driving transistor circuit in accordance with the CF (color filter) pattern. Using white light as a backlight, blue light, green light, and red light are obtained through a blue filter, a green filter, and a red filter, so that a full-color organic electroluminescence display having a low driving voltage and a long life can be obtained.

<Industrial field to which the EL element according to the present invention is applied>
The EL element according to the present invention can be used as a display device, a display, and various light sources.

  The display device according to the present invention described above is an electronic device such as a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, a video camera, a video signal input to the electronic device, or an electronic device. It is possible to apply to the display apparatus of the electronic device of all fields which display the video signal produced | generated by (1) as an image or an image | video.

  Examples of the light source include home lighting, interior lighting, backlights for watches and liquid crystals, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light Examples include, but are not limited to, a light source of a sensor. In particular, it can be effectively used as a backlight for various display devices combined with a color filter, a light diffusing plate, or the like, or a light source for illumination.

<< Embodiment of Top Emission Type EL Display Device >>
Next, an example of a specific embodiment of a top emission type EL display device preferably used in the present invention will be described.

  FIG. 4 is a schematic cross-sectional view showing a cross-sectional structure of the EL display device of the present embodiment.

  In FIG. 4, only the RGB pixel regions are shown, but in actuality, it is assumed that a plurality of pixel regions are formed on the entire surface of the actual light emitting region in the organic EL device as shown in FIG.

  The EL display device 201 of this embodiment is configured to irradiate the color filter substrate 207 with white light from the EL element. Therefore, color display is performed by the colored layers 208R, 208G, and 208B.

  Next, the structure of the low molecular weight light emitting functional layer sandwiched between the pixel electrode 223 and the cathode 250 will be described.

  As shown in FIG. 4, the light emitting layer 300 has a structure in which a hole injection layer 301, a hole transport layer 302, an organic light emitting layer 303, and an electron injection layer 304 are sequentially stacked from the pixel electrode 223 toward the cathode 250. It has become.

  Here, the hole injection layer 301 contains triarylamine (ATP), and the hole transport layer 302 is made of TPD (triphenyldiamine).

  The organic light emitting layer 303 includes a blue organic light emitting layer including a styrylamine light emitting layer (host) and an anthracene dopant, and a styrylamine light emitting layer (host) and a rubrene dopant. And a yellow organic light emitting layer.

The electron injection layer 304 is an aluminum quinolinol (Alq ₃ ) layer.

  The cathode 250 is formed by stacking an alloy such as MgAg and ITO.

  The material of each of the organic layers 301 to 304 and LiF are sequentially formed by a vacuum evaporation method using a heating boat (crucible). As for the formation of the cathode 250, a vacuum deposition method is used for metal materials, and a high-density plasma film formation method such as an ECR sputtering method, an ion plating method, or an opposed target sputtering method is used for oxide materials such as ITO. Is adopted.

  In such an EL display device 201, if the pixel electrode 223 is patterned for each color, it is not necessary to separately form the light emitting layer 300 and the cathode, and it is not necessary to perform mask vapor deposition that requires high accuracy.

  Next, the layer film formed above the cathode 250 will be described.

  An electrode protective layer 255 is formed above the cathode 250. The electrode protective layer 255 is formed by a high-density plasma film forming method such as an ECR sputtering method or an ion plating method. The material is preferably a silicon compound such as silicon oxynitride in consideration of transparency, adhesion and water resistance. Further, if the adhesion is improved by oxygen plasma treatment before the formation, the adhesion with the electrode is improved, and the light emission unevenness is reduced. Another object is to prevent penetration of the organic buffer layer before curing, and the film thickness is preferably 100 nm or more.

  In addition, an organic buffer layer 210 is formed above the electrode protective layer 255. As a raw material main component before curing of the organic buffer layer 210, it is necessary to be an organic compound material that is excellent in fluidity and does not have a volatile component such as a solvent in order to be applied and formed under reduced pressure, preferably, An epoxy monomer / oligomer having an epoxy group and a molecular weight of 3000 or less (definition of monomer: molecular weight 1000 or less, definition of oligomer: molecular weight 1000 to 3000). For example, bisphenol A type epoxy oligomer, bisphenol F type epoxy oligomer, phenol novolac type epoxy oligomer, 3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexene carboxylate, ε-caprolactone modified 3,4-epoxycyclohexyl Examples thereof include methyl 3 ', 4'-epoxycyclohexanecarboxylate and the like. These may be used alone or in combination.

  Further, as the curing agent that reacts with the epoxy monomer / oligomer, those that form a cured film having excellent electrical insulation, toughness, and excellent heat resistance are preferable, and addition polymerization types having excellent transparency and little variation in curing are preferable. . For example, 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride, 1,2,4,5-benzene Acid anhydride curing agents such as tetracarboxylic dianhydride and 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride are preferred. These curings are performed by heating in the range of 60 to 100 ° C., and the cured film becomes a polymer having an ester bond that is excellent in adhesion to silicon oxynitride.

  Further, by adding a relatively high molecular weight material such as an aromatic amine, alcohol, aminophenol or the like as a curing accelerator for promoting acid anhydride ring-opening, curing at a low temperature and in a short time becomes possible.

The viscosity of each raw material is preferably 1000 to 10,000 mPa · s (room temperature). The reason is that the organic light-emitting layer penetrates immediately after coating and does not generate a non-light-emitting region called a dark spot, and the film thickness is 3 to 10 μm or less. By suppressing the film thickness to this thickness, the color filter substrate 207 can be brought closer to the organic light emitting layer 303, so that a light emitting region can be widened without leaking light to an adjacent colored layer. Moreover, the viscosity of the buffer layer material containing these raw materials must also be 1000 mPa · s or more (room temperature). These materials are cured by heating in the range of 60 to 100 ° C. As a problem at this point, the viscosity temporarily decreases until the reaction is started immediately after heating. At this time, the material constituting the organic buffer layer 210 passes through the electrode protective layer 255 and the cathode 250 and reaches Alq ₃ to generate a dark spot. Therefore, it is more preferable to leave it at a low temperature until the curing proceeds to some extent and raise the temperature to a certain degree when the viscosity is increased to a certain degree to complete the curing. In addition, a cation-releasing type photopolymerization initiator may be added and partially cured at a low illuminance of 10 mW / cm ² or less before heating to prevent a decrease in viscosity. However, since many photopolymerization initiators are colored, they are limited to bottom emission applications.

  In order not to generate dark spots, the main component (for example, 70% by mass or more) of the buffer layer material is preferably 1000 mPa · s or more. The reason is that if a large amount of low-viscosity components are mixed, the organic light-emitting layer penetrates into the organic light-emitting layer before being cured by heating during curing to generate dark spots.

  In the present embodiment, the organic buffer layer 210 contains a silane coupling agent that improves adhesion to the cathode 250 and the gas barrier layer 230.

  In particular, in the case of the low molecular weight organic light emitting layer 303, a silane coupling agent is mixed in the material of the organic buffer layer 210, or a layer made of a silane coupling agent is added, and a cathode protective layer is further added. Yes. Further, since the layer of the silane coupling agent alone has a problem that the film strength is fragile, the organic buffer layer 210 supplements the film strength, and the organic layer is used so that the silane coupling agent prevents penetration of the cathode protective layer 255 into the pinhole. It is preferable to mix a silane coupling agent with the material of the buffer layer 210.

Since the silane coupling agent is covalently bonded to SiO ₂ , SiON, and SiN, the adhesion to the cathode protective layer, the gas barrier layer, the glass substrate, and the like is improved (it also reacts with a metal such as aluminum). Epoxysilane is preferred as the silane coupling agent. Epoxysilane is preferable because it reacts with the curing agent component (acid anhydride curing agent) of the buffer layer raw material.

  The composition of the main agent / curing agent / curing accelerator is preferably 40 to 45/40 to 45/10 to 20 (common to low-molecular / polymer light-emitting devices). In this way, the uncured component is 10 to 20% (when the unreacted epoxy group in the buffer layer raw material is 100%, the unreacted epoxy group residual ratio after curing: comparison with the epoxy group absorption peak intensity difference of FTIR) It is possible to prevent deterioration due to penetration of the uncured component into the light emitting functional layer (when 20% or less, it is called complete curing).

  Further, the curing agent group (acid anhydride, amine) remains as the material composition, and the uncured ratio is around 10% (when the dicarboxylic anhydride group in the raw material is 100%, the unreacted after curing) Acid anhydride group residual ratio). It is preferable to leave this degree in the completed film because the shrinkage during curing is small and the stress can be relaxed, so that damage to the organic EL element can be prevented in advance.

In particular, since a raw material having a low viscosity dissolves the material of the low molecular light emitting element (for example, there is a possibility of dissolving Alq ₃ ), it is preferable to use a high viscosity raw material for the low molecular light emitting element. On the other hand, this is not the case with polymer light emitting devices. It can be improved by increasing the molecular weight of each raw material to increase the viscosity. The range of preferable viscosity (or molecular weight) in the case of a low molecular light emitting device is in the range of 3000 mPa · s to 8000 mPa · s (at room temperature), and the film thickness (around 5 μm) at the time of screen printing and the flatness of the coated surface are Can be compatible.

  In addition to the silane coupling agent, a water capturing agent such as an isocyanate compound, and additives such as fine particles that prevent shrinkage during curing may be mixed in the organic buffer layer 210.

  A gas barrier layer 230 is formed above the organic buffer layer 210. As a method for forming the gas barrier layer 230, a high-density plasma film forming method such as an ECR sputtering method or an ion plating method is employed. The material is preferably a silicon compound such as silicon oxynitride in consideration of transparency, gas barrier properties and water resistance. Further, if the adhesion is improved by oxygen plasma treatment before formation, the reliability is improved. The film thickness is preferably 300 nm or more because the surface and side surface coating of the organic buffer layer is insufficient when the film thickness is 200 nm or less.

Specific examples of the present invention are described below, but the present invention is not limited to the following.
Example 1
<Production of EL Display Device 101> (Comparative Example)
With reference to the EL display device shown in FIG. 4, the device was manufactured by the method and procedure described in the section “Embodiment of Top Emission Type EL Display Device”. That is, first, an anode (pixel electrode), a hole injection layer, a hole transport layer, a white light emitting layer (EL layer), an electron injection layer, and a cathode (ITO) are stacked in this order on the first glass substrate. An EL element is formed by providing an organic buffer layer and a gas barrier layer thereon. On the other hand, on one side of a second glass substrate having a thickness of 500 μm, a black matrix is formed on the glass substrate according to Example 1 of Japanese Patent Application Laid-Open No. 2008-41181, and then R, G, B type three color filters are provided. A 100 μm pitch was formed, and a transparent flattening layer was provided thereon.

  The surface of the second glass substrate with a color filter on the color filter layer side, more precisely, the surface of the transparent flattening layer is EL using an adhesive of Sekisui Chemical's transparent double-sided tape, double tack tape # 5511 (5 μm). The EL display device 101 shown in FIG. 5 was obtained by pasting on the gas barrier layer of the first substrate on which the element was formed.

<Production of EL Display Device 102> (Comparative Example)
Next, in the method for manufacturing the EL display device 101, a C-1 solution containing the following acicular particles is spin-coated on the transparent flattening layer on the color filter layer, and a magnetic field is applied to normal the glass substrate. An EL display device 102 was produced in the same manner except that the needle-like particles were oriented in the direction and cured by ultraviolet irradiation to provide an optical functional layer. At this time, the thickness of the optical sheet was 5 μm, and the value of Tα / To obtained based on the result of measurement with the apparatus of FIGS. 1A and 1B was 0.40. The average orientation angle in the major axis direction of the acicular particles was 88 °. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 12 μm.

(C-1 solution)
Needle-like iron oxide particles coated with titanium oxide (iron oxide particles; AR Toda Kogyo AR major axis 180 nm, minor axis 20 nm, titanium oxide coverage 30%)… volume ratio 5%
UV curable resin (Mitsubishi Chemical UV2000) ... Volume ratio 95%
<Production of EL Display Device 103> (Comparative Example)
In the manufacturing method of the EL display device 101, a C-2 liquid containing the following flat particles is applied with a wire bar on the transparent flattening layer on the color filter layer, and immediately cured by ultraviolet irradiation to provide an optical sheet. The EL display device 103 was manufactured by the same method except for the above. At this time, the thickness of the optical sheet was 5 μm, the average orientation angle in the major axis direction of the particles was 45 °, and the value of Tα / To was 0.70. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 12 μm.

(C-2 liquid)
Plate-like alumina (Luxelenium FAO manufactured by Asahi Chemical Industry Co., Ltd., average aspect ratio 3.5, average particle size 11.0 μm)… volume ratio 5%
UV curable resin (Mitsubishi Chemical UV2000) ... Volume ratio 95%
<Preparation of EL Display Device 104> (Invention)
The EL display device 104 was manufactured by the same method except that the EL sheet 103 was spin coated with the C-2 liquid and cured by ultraviolet irradiation to provide an optical sheet. At this time, the thickness of the optical sheet was 5 μm, and as a result of producing by the spin coating method, the average orientation angle in the major axis direction of the particles was 25 °, and the value of Tα / To was 0.60. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 12 μm.

<Production of EL Display Devices 105 to 108> (Invention)
In the manufacturing method of the EL display device 104, the EL display devices 105 to 108 are all the same except that the flat particles contained in the liquid used in the spin coating are changed to those described in Table 1. Produced. At this time, the thickness of each optical sheet was 5 μm, and the average orientation angle in the major axis direction of the particles and the value of Tα / To were as shown in Table 1.

  The synthetic mica (MK-300) used here is a product manufactured by Corp Chemical Co., and the plate-like alumina (Seraph) is manufactured by Kinsei Matech. Further, the distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 12 μm in all cases.

<Production of EL Display Device 109> (Comparative Example)
The EL display device 107 is manufactured by the same method except that the optical sheet is provided on the surface of the second glass substrate opposite to the surface on which the color filter is provided (that is, the viewing side surface). 109 was produced. At this time, the thickness of the optical sheet was 5 μm, and the average orientation angle in the major axis direction of the particles and the value of Tα / To were the same as those of the EL display device 107. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 520 μm.

<Production of EL Display Device 110> (Comparative Example)
The EL display device 110 was manufactured by the same method except that the steps from spin coating to curing by ultraviolet irradiation were repeated six times in the manufacturing method of the EL display device 107. At this time, the thickness of the optical sheet was 30 μm, the average orientation angle in the major axis direction of the particles was 18 °, and the value of Tα / To was 0.80. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 37 μm.

<Production of EL Display Device 111> (Invention)
In the manufacturing method of the EL display device 104, the EL display device 111 is formed by the same method except that the C-2 solution is changed to the C-3 solution, spin coated, and cured by ultraviolet irradiation to provide an optical sheet. Produced. At this time, the thickness of the optical sheet was 5 m, the average orientation angle in the major axis direction of the particles was 20 °, and the value of Tα / To was 0.50. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 12 μm.

(C-3 solution)
Flat calcium carbonate (new lime flat aragonite, average aspect ratio 10, average particle size 5.0 μm) ... volume ratio 5%
UV curable resin (UV1000 manufactured by Mitsubishi Chemical) ... 95% volume ratio after layer formation
<Preparation of EL Display Device 112> (Invention)
An EL display device having a commercially available hard coat film on the outermost surface (viewing side surface of the second glass substrate) of the EL display device was produced by the following method.

  In the manufacturing method of the EL display device 107, the thickness of the second glass substrate provided with the color filter on one side is set to 190 μm, and the surface of the glass substrate opposite to the surface provided with the color filter (that is, visible) A side surface) is provided with an optical sheet, and a TAC film with a hard coat layer having a thickness of 100 μm (AH200 (clear panther) manufactured by Nitto Denko) is provided on the surface, and the hard coat film is provided on the outermost surface by the same method. An EL display device 112 was produced. When providing an optical sheet between the second glass substrate / the TAC film with a hard coat layer, Sekisui Chemical's transparent double-sided tape, double tack tape # 5511 (5 μm) was pasted on both sides of the optical sheet. At this time, the thickness of the optical sheet was 5 μm, and the average orientation angle in the major axis direction of the particles and the value of Tα / To were the same as those of the EL display device 107. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 210 μm.

<Preparation of EL Display Device 113> (Invention)
In the manufacturing method of the EL display device 112, the EL display device 113 was manufactured by the same method except that the thickness of the second glass substrate provided with the color filter on one side was set to 170 μm. At this time, the thickness of the optical sheet was 5 μm, and the average orientation angle in the major axis direction of the particles and the value of Tα / To were the same as those of the EL display device 107. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 190 μm.

<Preparation of EL Display Device 114> (Invention)
In the manufacturing method of the EL display device 112, the EL display device 114 was manufactured by the same method except that the thickness of the second glass substrate provided with the color filter on one side was set to 80 μm. At this time, the thickness of the optical sheet was 5 μm, and the average orientation angle in the major axis direction of the particles and the value of Tα / To were the same as those of the EL display device 107. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 100 μm.

<Production of EL Display Device 115> (Invention)
100 parts by mass of the following dope solution was sufficiently mixed with an in-line mixer (Toray static type in-tube mixer Hi-Mixer, SWJ), and then uniformly cast on a stainless steel band support using a belt casting apparatus. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. Tension is applied at the time of peeling so that the stretching ratio is 1.1 times in the longitudinal direction, then both ends of the web are gripped with a tenter so that the stretching ratio in the width direction is 1.1 times. Stretched. The residual solvent at the start of stretching was 30%. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, further carry for 30 minutes in the third drying zone set at 125 ° C., and perform drying, Thereafter, the film was stretched 1.2 times in the longitudinal direction at 180 ° C. to prepare an optical sheet S-115 having a film thickness of 40 μm.

<Dope composition>
Methylene chloride 300 parts by weight Ethanol 40 parts by weight Cellulose ester (cellulose acetate propionate; acetyl group substitution degree 1.9, propionyl group substitution degree 0.7, total acyl group substitution degree 2.6) 100 parts by weight aromatic terminal ester Compound (the following compound) 5.5 parts by mass Trimethylolpropane tris (3,4,5-trimethoxybenzoate)
5.5 parts by mass UV absorber (Tinubin 109, manufactured by Ciba Japan Co., Ltd.) 1.2 parts by mass UV absorber (Tinuvin 171, manufactured by Ciba Japan Co., Ltd.) 0.8 part by mass Flat particles (Kinsei Matec) Seraph 05025 by the company)
2 parts by mass

  In the manufacturing method of the EL display device 101, Sekisui Chemical's transparent double-sided tape, double tack tape # 5511 (on the surface of the second glass substrate with a color filter, on the surface of the color filter layer side, more precisely on the surface of the transparent flattening layer) EL display using the same method except that the optical sheet S-115 is bonded to the first substrate gas barrier layer via double tack tape # 5511 (5 μm). Device 115 was fabricated. In this apparatus, the thickness of the optical sheet was 40 μm, the average orientation angle in the major axis direction of the particles, and the value of Tα / To were 0.5. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 47 μm.

<Production of EL Display Device 116> (Invention)
(Pellet preparation)
Cellulose acetate propionate (acetyl group substitution degree 1.23, propionyl group substitution degree 1.31, number average molecular weight 75000) 100 parts by mass (meth) acrylic polymer A 5.5 parts by mass Sugar ester compound A 5.5 Part by weight Trimethylolpropane tris (3,4,5-trimethoxybenzoate)
1 part by mass IRGANOX-1010 (manufactured by Ciba Japan Co., Ltd.) 1 part by mass Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.) 0.5 part by mass (meth) acrylic polymer A: polymerization described in JP 2000-128911 A Bulk polymerization was performed by the method. That is, methyl acrylate was introduced as a monomer into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser, and nitrogen gas was introduced and the inside of the flask was replaced with nitrogen gas while stirring. Added.

  After the addition of thioglycerol, polymerization was carried out for 4 hours, the contents were returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added thereto to stop the polymerization. The contents were transferred to an evaporator, and tetrahydrofuran, residual monomer and residual thioglycerol were removed under reduced pressure at 80 ° C. to obtain a (meth) acrylic polymer A having a molecular weight of 1000.

  Sugar ester compound A: The following sugar ester compound

  2 parts by weight of flat particles (Seraph 05025 manufactured by Kinsei Matec Co., Ltd.) were added to the above material, mixed for 30 minutes with a V-type mixer containing nitrogen gas, and then a twin-screw extruder (PCM30 Co., Ltd.) attached with a strand die. And a cylindrical pellet having a length of 4 mm and a diameter of 3 mm was produced. At this time, the shear rate was set to 25 (mm / s). The obtained pellets were dried at 100 ° C. for 5 hours to have a water content of 100 ppm and supplied to a single screw extruder (GT-50; manufactured by Plastic Engineering Laboratory Co., Ltd.) equipped with a 300 mm wide T die. And T-die was set to 250 degreeC and it formed into a film. The surface of the T die was subjected to hard chrome plating and finished with a mirror finish with a surface roughness of 0.1S. The film from the T-die was dropped onto a first cooling roll with a chrome-plated mirror surface adjusted to 110 ° C.

  The film in close contact with the first cooling roll was pressed with an elastic touch roll after being transported around the circumference of the first cooling roll by a central angle of 10 °. At this time, it contacted with the pressure of 4 N / mm with respect to the whole width 250mm of a film. After the pressed film is brought into contact with the circumferential portion of the first cooling roll having a central angle of 150 °, a total of three cooling films, ie, a second cooling roll (temperature 110 ° C.) and a third cooling roll (temperature 80 ° C.) are cooled. The film was sequentially circumscribed on the roll, cooled and solidified to form a film, and peeled off by a peeling roll. Thereafter, the optical sheet S-116 having a film thickness of 40 μm was produced by stretching 1.2 times in the longitudinal direction at 180 ° C. In this apparatus, the thickness of the optical sheet was 40 μm, the average orientation angle in the major axis direction of the particles, and the value of Tα / To was 0.47. The distance from the light emitting side surface of the light transmissive electrode to the viewing side surface of the optical sheet was 47 μm.

<Performance evaluation>
(Front brightness improvement ratio)
The front luminances of the EL display elements 102 to 113 when the front luminance of the EL display element 101 is 1 are shown as relative values. The measurement was performed using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) to measure the light emission luminance from the front (2 ° viewing angle front luminance).

(Image bleeding evaluation)
In addition, pixel bleeding was examined visually from the image of the digital camera and evaluated according to the following criteria.
A: No pixel bleeding was observed, which was about the same as when no sheet was present. B: Pixel bleeding was hardly observed, and was almost the same as when there was no sheet. Δ: Pixel bleeding was slightly recognized. X: Slightly deteriorated compared to the case where there was no sheet x: Image blur was remarkably observed, and it was significantly deteriorated from the case where there was no sheet.

(Refractive index measurement)
The method described in the text was used to measure the refractive index of the transparent resin and flat particles constituting the optical sheet. The measurement wavelengths were all 589 nm.

  From Table 1, the EL display device of the present invention is excellent in light extraction effect and hardly causes image bleeding. In addition, when particles having a particle size of less than 10 μm, particles having an average aspect ratio of 5 or more, or when the value of Tβ / To is 0.65 or more, the difference in average refractive index between the particles and the resin ( When [Delta] n) is 0.06 or more, and when the distance from the viewing side surface of the light-transmissive electrode to the viewing side surface of the optical sheet is 200 [mu] m or less, the effect of improving the front brightness is particularly large without causing image blurring. Recognize.

It is a schematic diagram which shows the optical system at the time of evaluating the optical characteristic of the optical sheet concerning this invention. It is a schematic diagram which shows an example of embodiment of the EL element structure of this invention. It is a schematic diagram which shows an example of the cross-sectional structure of EL display apparatus of embodiment. It is a schematic diagram which shows an example of the circuit structure of the EL display apparatus of embodiment. It is a schematic diagram which shows the cross-sectional structure of the EL display apparatus produced in the Example.

Explanation of symbols

2 Substrate 2a Display area 2b Peripheral area 3 Sealing section 10 Display device 11 Scan line 13 Signal line 21 EL element 22 Substrate 23 Anode 24 Organic layer 24a Hole injection layer 24b Hole transport layer 24c Light emitting layer 24d Electron transport layer 25 Cathode 25a First layer 25b Second layer 201 EL display device 207 Color filter substrate 208R, 208G, 208B Colored layer 210 Organic buffer layer 223 Pixel electrode 230 Gas barrier layer 250 Cathode 255 Electrode protective layer 300 Light emitting layer 301 Hole injection layer 302 Hole transport Layer 303 Organic light emitting layer 304 Electron injection layer 401 First glass substrate 402 Anode 403 EL light emitting layer 404 Cathode (ITO)
405 Gas barrier layer 406 Adhesive layer 407 Optical sheet 408 Transparent flattened layer 409 Color filter 410 Second glass substrate

Claims (7)

A light-emitting layer is provided between a pair of electrodes opposed to each other on the substrate, and at least one of the pair of electrodes is a light-transmitting electrode. Light is extracted toward the outside of the EL element. An EL sheet that is provided with an optical sheet satisfying both of the following conditions a and b at any position on the light emitting layer side of the surface and on the viewing side of the light emitting side surface of the light transmissive electrode. element.
a. Of the light incident on the optical sheet, the parallel transmittance with respect to the light incident from the normal direction of the sheet surface is To, and the both surfaces of the sheet are sandwiched between two right-angle reflecting prism inclined surfaces. On the other hand, when the parallel transmittance with respect to light incident from a direction inclined by 45 ° is Tα, the value of Tα / To is 0.6 or less.
b. The optical sheet has a configuration in which flat particles having an average aspect ratio of 2 or more are dispersed in a transparent resin, and the major axis direction of the particles in two cross sections perpendicular to the sheet surface and the sheet surface direction. The average value of the smaller angles formed is within 30 °. 2. The EL element according to claim 1, wherein a distance from a light emitting side surface of the light transmissive electrode to a viewing side surface of the optical sheet is 200 μm or less. 3. The EL device according to claim 1, wherein the average particle diameter of the flat particles is less than 10 μm, and the average aspect ratio of the flat particles is 5 or more. 4. The EL device according to claim 1, wherein the flat particles have an average particle size of 5 μm or less and an average thickness of 0.5 μm or less. Of the light incident on the optical sheet, the value of Tβ / To is 0.65 or more, where Tβ is the parallel transmittance for light incident from a direction inclined by 40 ° with respect to the normal of the sheet surface. The EL element according to any one of claims 1 to 4, wherein the EL element is characterized in that The EL element according to claim 1, wherein an average refractive index difference between the transparent resin and the flat particles constituting the optical sheet is 0.06 or more. An EL display device using the EL element according to claim 1.

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