JP2010055894A - Sealing film for light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing film for a light-emitting element which is flexible, and has high sealing properties and high light extraction efficiency. <P>SOLUTION: The sealing film for the light-emitting element is equipped with a multilayered film 4 formed by laminating organic layers 2 and inorganic layers 3 on the surface of a translucent film 1. Refractive index differences between neighboring layers are 0.05 or less. The refractive index differences of a layer in contact with the translucent film 1 out of the multilayered film 4 are lower than those of other layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sealing film for a light emitting element used as a transparent substrate such as a liquid crystal display element and an organic EL element (organic electroluminescence element).

  As a transparent base material for liquid crystal display elements, organic EL elements, etc., film base materials such as transparent plastics, which have features such as light weight and high degree of freedom, are used instead of glass substrates that are heavy and easy to break. Being started.

  However, a film substrate such as a transparent plastic has a problem that sealing properties are inferior to a glass substrate. If the sealing property of the film substrate is inferior, moisture and oxygen enter the element, and the light emitting element is deteriorated. Therefore, in order to ensure high sealing performance while maintaining transparency, in recent years, a technique for producing a barrier film having an alternately laminated structure of organic layers / inorganic layers on a film substrate by vacuum deposition has been proposed. (See Patent Document 1).

However, in the sealing film having the alternately laminated structure of these organic layers / inorganic layers, the influence of coloring due to multilayer interference of light cannot be ignored due to the difference in the refractive index of each layer. In order to reduce this coloring, a technique for reducing the difference between the refractive index of the organic layer and the refractive index of the inorganic layer has also been proposed (see Patent Document 2), but these sealing films are used for organic EL elements. In such a case, there is a problem of a decrease in light extraction efficiency due to the organic layer / inorganic layer stack.
US Pat. No. 6,413,645 JP 2003-203771 A

  Thus, if an organic EL element using a film base material can be obtained, the weight can be reduced as compared with that using a glass base material. A technique for improving the sealing property by installing a barrier layer having a laminated structure of inorganic layers has been proposed. On the other hand, there is a problem that the light extraction efficiency of the organic EL element is lowered due to the alternately laminated structure of the organic layer / inorganic layer.

  This invention is made | formed in view of said point, and it aims at providing the sealing film for light emitting elements which has flexibility, high sealing property, and high light extraction efficiency.

  A sealing film A for a light emitting device according to claim 1 of the present invention is a sealing film A for a light emitting device comprising a multilayer film 4 in which an organic layer 2 and an inorganic layer 3 are laminated on the surface of a translucent film 1. The difference in refractive index between adjacent layers is 0.05 or less, and the refractive index of the layer in contact with the translucent film 1 in the multilayer film 4 is lower than the refractive index of the other layer. To do.

  The sealing film A for a light-emitting element according to claim 2 of the present invention is that in claim 1, the organic layer 2 disperses particles having a refractive index higher than the refractive index of the resin forming the resin phase in the resin phase. It is characterized by being formed.

  The sealing film A for a light emitting device according to claim 3 of the present invention is characterized in that in claim 1 or 2, the organic layer 2 is formed by dispersing hollow particles in a resin phase. It is.

  In invention of Claim 1, by using the resin-made translucent film 1 as a base material, it becomes easier to be flexible than a glass base material, and can be formed flexibly. Moreover, by providing the multilayer film 4 having a laminated structure of an organic layer / inorganic layer, the gas barrier property can be increased, and the sealing property can be higher than that of the translucent film 1 alone. . Furthermore, by performing optical design of the organic layer and the inorganic layer, long-term stable optical characteristics can be realized with high light extraction efficiency.

  According to the second aspect of the present invention, further high sealing performance can be realized by forming the organic layer 2 with a mixed system of particles having a high refractive index and a resin.

  In the invention of claim 3, by using the hollow particles, the light transmittance of the sealing film for a light emitting element can be improved more than when solid particles having the same shape as the hollow particles are used.

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

  The sealing film A for light-emitting elements of the present invention comprises a multilayer film 4 formed by laminating an organic layer 2 and an inorganic layer 3 on the surface of a translucent film 1 as a sealing layer.

  The translucent film 1 is used as a transparent flexible support substrate, and can be used without any particular limitation as long as it is a transparent and flexible plastic substrate. Any substrate that can be held can be selected as appropriate depending on, for example, the purpose of use of the light-emitting element. Specific examples of the material constituting the translucent film 1 include polyester resin, methacrylic resin, methacrylic acid-maleic acid copolymer, polystyrene, transparent fluororesin, polyimide resin, fluorinated polyimide resin, polyamide resin, and polyamideimide. Resin, polyetherimide resin, cellulose acylate resin, polyurethane resin, polyetheretherketone resin, polycarbonate resin, alicyclic polyolefin resin, polyarylate resin, polyethersulfone resin, polysulfone resin, cycloolefin copolymer, fluorene ring modification Examples thereof include thermoplastic resins such as carbonate resins, alicyclic modified polycarbonate resins, and acryloyl compounds. Among these resins, a preferable example is a film made of a polyester resin, particularly a polyethyl naphthalate resin (PEN), a polyarylate resin (PAr), a polyether sulfone resin (PES), or the like. Moreover, the thickness of the translucent film 1 should just be a range which does not impair physical properties, such as flexibility, translucency, and intensity | strength, For example, it is preferable to set it as 0.01-1 mm.

  One or more organic layers 2 are provided adjacent to the inorganic layer 3 in order to improve the brittleness and sealing performance of the inorganic layer 3, and in the present invention, the inorganic layer 3 and the organic layer 2 are alternately laminated. It is preferable that Moreover, it is preferable that the refractive index of the organic layer 2 is more than the refractive index of the said translucent film, and below the refractive index of the anode material mentioned later. As described above, the refractive index of polyethylene naphthalate (PEN), which is a material of the translucent film 1 that is preferably used in the present invention, is about 1.65, and is generally used for an anode material used in a bottom emission type organic EL element. Since the refractive index of ITO is 2.00 or less, the refractive index of the material constituting the organic layer 2 is preferably 1.65 to 2.00. Although it does not specifically limit about the thickness of the organic layer 2, 10 nm-5000 nm are preferable. If the thickness of the organic layer 2 is too thin, it will be difficult to obtain thickness uniformity, so that the structural defects of the inorganic layer 3 cannot be efficiently filled with the organic layer 2, and the improvement in sealing performance is observed. It may not be possible. Conversely, if the thickness of the organic layer 2 is too thick, cracks are likely to occur in the organic layer 2 due to an external force such as bending, which may cause a problem that the sealing performance is lowered. Examples of the method for forming the organic layer 2 include a method in which an organic substance is laminated by coating or vapor deposition, and then ultraviolet curing, vapor deposition, a vacuum film forming method by plasma CVD, or the like. When the coating method is used, various conventionally used coating methods such as spray coating, spin coating, and bar coating can be used.

The organic layer 2 can be formed of a material satisfying a refractive index of 1.65 to 2.00 such as polyimide resin or bisphenol type epoxy resin. The organic layer 2 can be formed by dispersing one or more kinds of particles having a refractive index higher than that of the resin in the resin phase (matrix). In this case, the resin is not particularly limited, and an appropriate material such as an acrylic resin, an epoxy resin, or a polyimide resin can be used. Further, as the particles having a high refractive index, a material having low absorption of visible light and high refraction, such as TiO ₂ , ZrO ₂ , and Al ₂ O ₃ is preferable. The particle diameter of these particles is preferably in the range of 0.001 μm to 100 μm. If the particle diameter is larger than the above range, it is difficult to flatten the organic layer 2. The refractive index of the particles can be higher than the refractive index of the resin by 0.01 or more. Moreover, 5 to 95 mass% of particles can be blended with respect to the total amount of the resin in the organic layer 2.

As particles dispersed in the organic layer 2, hollow particles can be used. In this case, the light transmittance of the sealing film for a light-emitting element can be improved as compared with the case of using non-hollow particles (solid particles) having the same shape. As the hollow particles, those made of a material having low visible light absorption such as SiO ₂ , TiO ₂ , ZrO ₂ , and Al ₂ O _{3 with} a particle size in the range of 0.001 to 100 μm are preferably used. If the particle size is larger than the above range, it may be difficult to planarize the organic layer 2. The refractive index of the particles can be higher than the refractive index of the resin by 0.01 or more. Moreover, 5 to 95 mass% of particles can be blended with respect to the total amount of the resin in the organic layer 2.

The inorganic layer 3 is a layer that contains an inorganic substance and improves the sealing performance of the translucent film 1. The inorganic component contained in the inorganic layer is not particularly limited. For example, an oxide, nitride, or oxynitride containing one or more selected from Si, Al, In, Sn, Zn, Ti, Cu, Ce, Ta, and the like. Things can be used. The inorganic layer 3 in the present invention is preferably not less than the refractive index of the translucent film 1 in terms of refractive index and not more than the refractive index of the anode material described later. The refractive index of polyethylene naphthalate (PEN), which is a material of the translucent film 1 preferably used in the present invention, is about 1.65, and the refractive index of ITO, which is an anode material generally used in bottom emission type organic EL elements. Is about 2.00. For this reason, it is preferable that the refractive index of the material which comprises the inorganic layer 3 is 1.65 to 2.00. For example, the inorganic layer 3 is preferably Al ₂ O ₃ (refractive index n = 1.75) closer to the translucent film 1, and the outer inorganic layer 3 is ZnO (refractive index n = 1. 90). The inorganic layer 3 in the present invention may be formed by any method as long as it can form a target thin film. For example, a sputtering method, a vacuum deposition method, an ion plating method, a plasma CVD method and the like are suitable. The thickness of the inorganic layer is not particularly limited, but if it is too thick, there is a risk of cracking due to bending stress, and if it is too thin, the film is distributed in an island shape, so that the water vapor barrier property tends to decrease in any case. For this reason, the thickness of each inorganic layer 3 is preferably 5 nm to 1000 nm. In the present invention, it is preferable that two or more inorganic layers 3 are formed. In that case, each inorganic layer 3 may have the same composition or a different composition, and is not limited.

  And the sealing film A for light emitting elements of this invention forms the multilayer film 4 which laminated | stacked the at least one layer of the inorganic layer 3 and the at least one layer of the organic layer 2 on the surface of the translucent film 1 as a sealing layer. Has been. The upper limit of the number of inorganic layers 3 and organic layers 2 is not particularly limited, but can be 10 layers or less. Further, the difference in refractive index between the adjacent organic layer 2 and the inorganic layer 3 is 0.05 or less. In this case, since it is preferable that there is no difference in refractive index between the adjacent organic layer 2 and the inorganic layer 3, the lower limit of this difference is zero. Moreover, the refractive index of the layer which contacts the translucent film 1 among the multilayer films 4 is set lower than the refractive index of the other layer. That is, the refractive index of the layer in contact with the translucent film 1 among the organic layer 2 and the inorganic layer 3 constituting the multilayer film 4 is made the lowest.

  The sealing film A for a light emitting device of the present invention is configured as described above, so that multi-layer interference of light is suppressed, and light is strengthened or weakened at an arbitrary wavelength due to such multi-layer interference. As a result, the optical characteristics are not deteriorated such that a uniform spectrum cannot be obtained. Further, when a bottom emission type organic EL element is formed as a light emitting element, a difference in refractive index between the oxide semiconductor (anode material) such as ITO formed as an anode (transparent conductive film) and the translucent film 1 is large. When the anode is directly formed on the surface of the light-sensitive film 1, the difference in refractive index at the interface between the layers increases, and Snell's law reduces the critical angle at which total reflection occurs, leading to a decrease in light extraction efficiency. Therefore, in the present invention, the refractive index of the multilayer film 4 in which the organic layer 2 and the inorganic layer 3 are laminated is designed as described above, and an anode is formed on the multilayer film 4 so that the refractive index between the respective layers can be reduced. The light extraction efficiency is improved by making the difference as small as possible.

  In the present invention, the refractive indexes of the translucent film 1, the organic layer 2, and the inorganic layer 3 can be designed by changing the type and composition of the materials used. Moreover, as long as the effect of this invention is not impaired, you may have another layer, for example, an ultraviolet absorption layer, an antireflection layer, etc. Further, the refractive index value of the present invention is a value for light having a wavelength of 633 nm unless otherwise specified. The refractive index of each layer can be measured using a prism coupler, a transmission / reflection refractometer, and an Abbe refractometer.

  Hereinafter, the present invention will be described specifically by way of examples.

(Example)
As the translucent film 1, a PEN film having a thickness of 120 μm was used. Both sides of the film were subjected to corona discharge treatment and UV irradiation treatment. By the corona discharge treatment, the wettability of the surface of the translucent film 1 is remarkably improved by the physical surface modification of the discharge itself and the chemical surface modification by the generation of polar functional groups, and further by the surface treatment by the UV irradiation. Surface modification and washing of the translucent film 1 are performed.

  An organic layer 2a, an inorganic layer 3a, an organic layer 2b, an organic layer 2c, and an inorganic layer 3b were laminated in order on one side of the translucent film 1 as a multilayer film 4.

The organic layer 2 a is a layer formed in contact with the surface of the translucent film 1. TiO ₂ spherical particles 1g, the imide resin 9g were mixed and stirred by a homogenizer, after dispersing the TiO ₂ spherical particles in the imide resin, by heat cured for 10 minutes at coating to 200 ° C. by spin coating An organic layer 2a having a thickness of 500 nm was formed. The refractive index of the organic layer 2a was 1.71. The TiO ₂ spherical particles were anatase type with a refractive index of 2.5 and a particle size of 20 to 30 nm. The imide-based resin was a product number HRI672 manufactured by Optomate Corporation and had a refractive index of nD = 1.67.

The inorganic layer 3a is a layer formed of Al ₂ O ₃ . Al was set as a target, and a pulse application type DC power source was prepared as a discharge power source. After the preparation of the translucent film 1 on which the organic layer 2a was formed on the sputtering apparatus, the vacuum chamber door was closed, the vacuum pump was started, and evacuation was started. When the ultimate pressure reached 4 × 10 ⁻⁴ Pa, argon was introduced as a discharge gas to turn on the discharge power source, and plasma was generated on the Al target at a discharge power of 5 kW and a film formation pressure of 0.3 Pa for 5 minutes. Pre-sputtering was performed. Thereafter, oxygen was introduced as a reaction gas. Discharge is stabilized, the film formation was carried out for a certain time _Al 2 _{O 3.} After completion of film formation, the vacuum chamber was returned to atmospheric pressure, and a film having an Al ₂ O ₃ layer having a thickness of 100 nm formed on the surface of the organic layer 2a was taken out. The refractive index of this inorganic layer 3a was 1.75.

The organic layer 2b is a layer formed on the surface of the inorganic layer 3a. 4 g of TiO ₂ spherical particles and 6 g of imide resin were mixed and stirred with a homogenizer, and the TiO ₂ spherical particles were dispersed in the imide resin, and then applied onto the inorganic layer 3a by spin coating to 200 ° C. For 10 minutes to form an organic layer 2b having a thickness of 500 nm. The refractive index of the organic layer 2b was 1.80. The TiO ₂ spherical particles and imide resin used was the same as described above.

The organic layer 2c is a layer formed on the surface of the organic layer 2b. TiO ₂ spherical particles 5g, the imide resin 5g were mixed and stirred by a homogenizer, after dispersing the TiO ₂ spherical particles in the imide resin, a 200 ° C. is applied by spin coating on the organic layer 2b For 10 minutes to form an organic layer 2c having a thickness of 300 nm. The refractive index of the organic layer 2c was 1.85.

The inorganic layer 3b is a ZnO layer formed on the surface of the organic layer 2c. The inorganic layer 3b was formed by depositing ZnO in the same manner as the Al ₂ O ₃ inorganic layer 3a except that the target was changed to Zn. The refractive index of the inorganic layer 3b was 1.90.

(Example 2)
Instead of the TiO ₂ particles (anatase type, refractive index 2.5, particle size 20-30 nm) used in Example 1, hollow TiO ₂ particles (anatase type, refractive index 2.5, particle size 20-30 nm) were used. used. The refractive index of the organic layer 2a was 1.71, the refractive index of the organic layer 2b was 1.80, and the refractive index of the organic layer 2c was 1.90. Other than that, in the same manner as in Example 1, the organic layer 2a, the inorganic layer 3a, the organic layer 2b, the organic layer 2c, and the inorganic layer 3b were sequentially laminated as a multilayer film 4 on one side of the translucent film 1. Formed.

(Example 3)
As a multilayer film 4 formed on one side of a light-transmitting film 1 similar to that in Example 1, an organic layer 2a, an organic layer 2b, an inorganic layer 3a, an organic layer 2c, an organic layer 2d, and an organic layer 2e were sequentially stacked. .

The organic layer 2 a is a layer formed in contact with the surface of the translucent film 1. Mix and stir 0.2 g of TiO ₂ spherical particles and 10 g of polyimide resin with a homogenizer, disperse the TiO ₂ spherical particles in the polyimide resin, apply by spin coating, and heat cure at 200 ° C. for 10 minutes. Thus, an organic layer 2a having a thickness of 500 nm was formed. The refractive index of the organic layer 2a was 1.66. The same TiO ₂ spherical particles as those used in Example 1 were used. The polyimide resin used was a product number HRI592 manufactured by Optomate Corporation and the refractive index was nD = 1.59.

The organic layer 2b is a layer formed on the organic layer 2a. After 0.4 g of TiO ₂ spherical particles and 10 g of polyimide resin were mixed and stirred with a homogenizer, the TiO ₂ spherical particles were dispersed in the polyimide resin, and then applied onto the inorganic layer 3 a by spin coating to 200 ° C. For 10 minutes to form an organic layer 2b having a thickness of 500 nm. The refractive index of the organic layer 2b was 1.71. The TiO ₂ spherical particles and the polyimide resin used was the same as described above.

The inorganic layer 3a is a layer formed of Al ₂ O _{3 and} was formed in the same manner as the inorganic layer 3a in Example 1.

The organic layer 2c is a layer formed on the surface of the inorganic layer 3a. TiO ₂ spherical particles 0.5 g and polyimide resin 10 g were mixed and stirred with a homogenizer to disperse the TiO ₂ spherical particles in the polyimide resin, and then applied onto the inorganic layer 3a by spin coating to 200 ° C. For 10 minutes to form an organic layer 2c having a thickness of 300 nm. The refractive index of the organic layer 2c was 1.80. The TiO ₂ spherical particles and the polyimide resin used was the same as described above.

The organic layer 2d is a layer formed on the surface of the organic layer 2c. 0.6 g of TiO ₂ spherical particles and 10 g of polyimide resin were mixed and stirred with a homogenizer, and the TiO ₂ spherical particles were dispersed in the polyimide resin, and then applied onto the organic layer 2c by spin coating to 200 ° C. The organic layer 2d having a thickness of 200 nm was formed by heating and curing for 10 minutes. The refractive index of the organic layer 2d was 1.85. The TiO ₂ spherical particles and the polyimide resin used was the same as described above.

The organic layer 2e is a layer formed on the surface of the organic layer 2d. TiO ₂ spherical particles 0.7 g and polyimide resin 10 g were mixed and stirred with a homogenizer, and the TiO ₂ spherical particles were dispersed in the polyimide resin, and then applied onto the organic layer 2d by spin coating to 200 ° C. The organic layer 2e having a thickness of 200 nm was formed by heating and curing for 10 minutes. The refractive index of the organic layer 2e was 1.90. The TiO ₂ spherical particles and the polyimide resin used was the same as described above.

Example 4
In Example 1, in forming the organic layer 2a and the organic layer 2b, ZrO ₂ particles (anatase type, refractive index 2.2, particle diameter of about 20 nm) were used instead of TiO ₂ particles. The refractive index of the organic layer 2a was 1.71, and the refractive index of the organic layer 2b was 1.80. Other than that, in the same manner as in Example 1, the organic layer 2a, the inorganic layer 3a, the organic layer 2b, the organic layer 2c, and the inorganic layer 3b were sequentially laminated as a multilayer film 4 on one side of the translucent film 1. Formed.

(Comparative Example 1)
Except that the multilayer film 4 was formed on the surface of the translucent film 1 in the order of the organic layer 2c, the ZnO inorganic layer 3b, the organic layer 2b, the organic layer 2a, and the Al ₂ O ₃ inorganic layer 3a. Went to.

  An organic EL element was formed as a light emitting element using the sealing film A for a light emitting element of the above Examples and Comparative Examples.

  First, sputtering was performed on the multilayer film 4 (sealing layer) side of the sealing film A using an ITO (indium tin oxide indium) target (manufactured by Tosoh Corporation) to form an ITO layer having a thickness of 150 nm. The obtained sealing film with an ITO layer was annealed at 200 ° C. for 1 hour in an Ar atmosphere to form a transparent electrode layer (anode layer) 10 having a sheet resistance of 20Ω / □.

  Next, the sealing film with a transparent electrode layer was subjected to ultrasonic cleaning with pure water for 10 minutes, dried, and then subjected to UV-03 treatment for 10 minutes. Thereafter, this sealing film with a transparent electrode layer is set in a vacuum deposition apparatus, and N, N′-diphenyl-N, N′-bis (1-naphthyl) -1,1′-biphenyl is used as the hole transport layer 11. -4,4'-diamine (NPB) (manufactured by eRay) was formed on the anode layer 10 to a thickness of 40 nm. Next, 60 nm of aluminum-tris (8-hydroxyquinoline) (Alq) (manufactured by eRay) was formed on the hole transport layer 11 as the electron transport layer 12 and the light emitting layer 13. Further thereon, 1 nm of LiF (manufactured by High Purity Chemical) was formed as the electron injection layer 14. Finally, Al (made by high-purity chemical) was vacuum-deposited on the electron injection layer 14 with a film thickness of 80 nm to form the cathode layer 15. Then, the sealing film formed by vapor-depositing each of these layers was transported to a glove box having a dew point of −80 ° C. or less in a dry nitrogen atmosphere without being exposed to the air.

  On the other hand, a sealant made of UV curable resin was prepared in advance while adhering a water absorbing agent (made by Dynic) to the glass sealing cap 16 and applying the sealing agent made of UV curable resin to the outer periphery of the sealing cap 16. Then, the sealing film A and the sealing cap 16 are laminated with a sealing agent in the glove box, and each layer is sealed with the sealing cap 16 as shown in FIG. An organic EL light emitting device was obtained.

Characteristics of the organic EL light-emitting device obtained as described above, using a DC power supply (manufactured by case Ray), to secure the current flowing through the internal element 10 mA / cm ^2, using a luminance meter (manufactured by Topcon) element The characteristic evaluation of was performed. Front luminance [current efficiency (cd / A) was measured for each 10 ° angular orientation from −80 ° to + 80 °, and the total luminous flux [power efficiency lm / W] was calculated. The results are shown in Table 1 below. Based on the current efficiency (cd / A) and power efficiency (lm / W) of Comparative Example 1, the front and omnidirectional light extraction efficiency improvement magnification of each Example 1 is calculated. It was about 1.4 times in Example 2, about 1.4 times in Example 2, about 1.4 times in Example 3, and about 1.3 times in Example 4.

It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows an example of an organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Translucent film 2 Organic layer 3 Inorganic layer 4 Multilayer film

Claims (3)

  In the sealing film for a light-emitting element including a multilayer film in which an organic layer and an inorganic layer are laminated on the surface of the light-transmitting film, the difference in refractive index between adjacent layers is 0.05 or less, and the multilayer film The sealing film for light emitting elements characterized by the refractive index of the layer which contacts a translucent film being lower than the refractive index of the other layer.   2. The sealing film for a light-emitting element according to claim 1, wherein the organic layer is formed by dispersing particles having a refractive index higher than that of the resin forming the resin phase in the resin phase. The organic layer is formed by dispersing hollow particles in a resin phase, and the sealing film for a light-emitting element according to claim 1 or 2.

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