JP2005243556A - Drying agent for organic el devices, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drying agent for organic EL element which suppresses deterioration of the element such as generation and expansion of a dark spot accompanying duration of drive time, and which has high hygroscopic performance and can continue initial performance for a long time, and can be manufactured at low cost, and which is suitable for mass production, and its manufacturing method. <P>SOLUTION: This is a drying agent for organic EL element which consists of a mixture containing a granular hygroscopic material 50-300 parts by mass against a thermoplastic resin 100 parts by mass. The foam resin of the drying agent for organic EL element has an expansion ratio of 1.1-2.0 times, the granular hygroscopic material is supported by the foam resin layer, and a gap is formed at least at a part of the surroundings of the granular hygroscopic material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a desiccant for an organic EL element and a method for producing the same. In detail, it is related with the desiccant for organic EL elements used in order to protect an organic EL element from water vapor | steam, and its manufacturing method.

  An organic EL (electroluminescence) element is a structure in which an organic light-emitting layer made using an organic compound is sandwiched between a pair of electrodes. Compared with a liquid crystal element, responsiveness, brightness, visibility, and low power consumption Excellent in terms of color development and thinning. Therefore, an organic EL display using an organic EL element has attracted attention as a next-generation display that replaces a cathode ray tube display or a liquid crystal display.

  However, organic EL elements are vulnerable to substances such as water vapor, oxygen, and carbon dioxide in the atmosphere, and are particularly vulnerable to water vapor. In the organic EL element, the light emitting layer and the electrode layer are peeled off by water vapor existing in the organic EL element or water vapor entering the organic EL element from the outside, and as a result, a non-light emitting region called a so-called dark spot is generated. . Thus, many desiccants for organic EL elements that protect the organic EL elements from water vapor have been proposed and implemented.

  In the organic EL element described in Patent Document 1, a drying means has been proposed in which an organic EL structure is housed in an airtight case, and diphosphorus pentoxide is disposed in the airtight case isolated from the structure. . However, since diphosphorus pentoxide is a deliquescent compound, it absorbs water vapor and deliquesces to become phosphoric acid, and this phosphoric acid adversely affects the organic EL structure. In addition, diphosphorus pentoxide is extremely difficult to handle because it generates significant heat when moisture is absorbed.

In the organic EL device described in Patent Document 2, a protective case is provided around the organic EL device, and the protective case is filled with a fine powder solid dehydrating agent such as zeolite, activated alumina, silica gel or calcium oxide. Has been proposed. However, since these fine powder solid dehydrating agents are likely to be scattered, it is difficult to use them in a clean room. In addition, the fine powder solid dehydrating agent is scattered and the organic EL element is contaminated during the manufacturing process.
As described above, since the powdery desiccant is easily scattered, it is difficult to handle the powder desiccant, and it is difficult to dispose the desiccant in the organic EL element. Become. Therefore, as a method for solving these problems, a method of making a mixture of a resin and a powdery desiccant has been proposed.

  In the organic EL element described in Patent Document 3, a desiccant obtained by mixing a hygroscopic agent in fluorocarbon oil has been proposed. However, in this desiccant, since the hygroscopic agent is covered with the fluorocarbon oil, the hygroscopic ability such as the initial hygroscopic ability and the hygroscopic ability of the hygroscopic component is lowered. Moreover, in order to manufacture this desiccant, the process of enclosing the mixture of fluorocarbon oil and a hygroscopic agent in an organic EL element is required, and this enclosing process becomes complicated.

  In the organic EL element described in Patent Document 4, there is a drying means using a mixture of a desiccant and a high molecular organic compound having a water absorption rate of 24% at 23 ° C under ASTM D570 of 1% or less. It is disclosed. However, since this mixture is in the form of a solution in which the above desiccant and the high molecular weight organic compound are mixed in a hydrocarbon or halogenated hydrocarbon solvent, the mixture is dried after being placed in the organic EL device. Requires a process. During this drying step, it is difficult to completely remove the hydrocarbon-based or halogenated hydrocarbon-based solvent, and these solvents are volatilized by heat released during light emission of the organic EL element. There is a consideration that adversely affects the organic EL element. Furthermore, since the organic polymer compound covers the desiccant, there is a problem that the hygroscopic ability such as the initial hygroscopic ability and the hygroscopic ability is lowered.

  In the organic EL element described in Patent Document 5, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, calcium hydride, strontium hydride, barium hydride, and aluminum hydride are used as the desiccant for the organic EL element. A mixture of a desiccant and a silicone compound is disclosed. Since this desiccant uses a silicone compound having a high moisture permeability as a binder resin, it is superior to the desiccant for organic EL proposed in Patent Document 4 in moisture absorption capacity such as initial moisture absorption capacity and moisture absorption capacity. Yes. However, this desiccant also has a negative effect on the luminance of the organic EL element due to the volatilization of the low molecular weight silicone compound due to the heat released during the light emission of the organic EL element.

  In the organic EL element described in Patent Document 6, a hygroscopic molded body composed of a hygroscopic agent containing an alkaline earth metal oxide or the like and a gas permeable resin is disclosed. In this hygroscopic molded body, since the hygroscopic agent is coated with a gas permeable resin, the hygroscopic ability such as the initial hygroscopic ability and the hygroscopic ability is lowered. Furthermore, Patent Document 6 proposes a method of making the moisture-absorbent molded body porous by stretching, or a fibrillation method using a fluororesin as a resin component, as a method for improving the decrease in the hygroscopic capacity of the hygroscopic molded body. Has been. However, all of these must be once processed into a sheet shape, which complicates the manufacturing process. In addition, when an alkaline earth metal oxide is used as a hygroscopic agent, it expands after moisture absorption, which adversely affects the organic EL element.

  In the organic EL element described in Patent Document 7, a porous adsorbent sheet composed of a binder resin and a hygroscopic adsorbent is disclosed as a desiccant for the organic EL element. This desiccant for organic EL elements prevents the lowering of the hygroscopic ability such as the initial hygroscopic ability and the hygroscopic ability of the adsorbent by making the adsorbent sheet porous. However, this porous adsorbent sheet requires a molding aid at the time of molding, but this molding aid is volatilized by the heat released during the light emission of the organic EL element, adversely affecting the luminance of the organic EL element. There is consideration.

As a method of preventing moisture absorption of the organic EL element, the method of dispersing the hygroscopic agent in the polymer compound covers the surface of the hygroscopic agent, so that the initial hygroscopic ability inherent in the hygroscopic agent and There is a problem that the hygroscopic ability such as the hygroscopic power is lowered. Furthermore, there is a problem in that outgas is volatilized from the polymer compound or the molding aid due to heat generated during light emission of the organic EL element, which adversely affects the luminance of the organic EL element. Methods for solving these problems are described in Patent Document 8 and Patent Document 9.
Patent Document 8 proposes a desiccant for an organic EL element obtained by heating a mixture of a thermally decomposable organic binder and an inorganic moisture absorbent to a temperature higher than the thermal decomposition temperature of the organic binder to decompose and remove the organic binder. Yes. According to the desiccant for an organic EL element obtained by this method, the problems regarding the reduction of the hygroscopic capacity such as the initial hygroscopic capacity and the hygroscopic capacity of the hygroscopic agent and the outgas generation are solved, but the desiccant preparation process is complicated. Furthermore, since it takes a long time for firing, it is not practical.

  Patent Document 9 proposes a desiccant for an organic EL element in which zeolite or barium oxide is supported on a sheet made of glass fiber or ceramic fiber. The desiccant for organic EL elements obtained by this method does not cause outgassing because the sheet does not support zeolite or barium oxide with a binder resin, but the desiccant for organic EL elements is not contained in the organic EL element. When arranged, zeolite or barium oxide may fall off from the sheet and contaminate the organic EL element. In addition, there are problems such as cracking of the desiccant during the firing, generation of warpage, dropping of the hygroscopic agent from the sheet, and since the firing has a long time, the resulting desiccant becomes expensive and practical. Not right. Moreover, the amount of zeolite or barium oxide supported on the sheet is unknown.

  As described above, since the conventional desiccant for organic EL elements is inferior in initial moisture absorption capacity and moisture absorption capacity such as moisture absorption, it takes a long time to remove water vapor in the organic EL element and water vapor that has entered the organic EL element. As a result, the effect of preventing the deterioration phenomenon of the organic EL element such as the generation of the dark spot in the initial light emission of the organic EL element and the generation / expansion of the dark spot with the lapse of the light emission time is insufficient. Moreover, even if the conventional desiccant for organic EL elements has a water vapor removing effect to some extent, outgas is generated from the desiccant during light emission of the organic EL element, and the organic EL element is adversely affected. The desiccant has a problem that it is inferior in mass productivity or cost because it takes a long time to manufacture the desiccant and the manufacturing process is complicated.

JP-A-3-26109 JP-A-6-176867 Japanese Patent Laid-Open No. 5-114486 JP 2000-195660 A JP 2000-277254 A JP 2002-43055 A JP 2002-280166 A Japanese Patent Laid-Open No. 2003-187762 JP 2003-163077 A

  The present invention can suppress the deterioration of the organic EL element such as the generation and expansion of the dark spot with the occurrence of the dark spot and the emission time of the organic EL element in the initial light emission, and can maintain the initial performance for a long time. Another object of the present invention is to provide an organic EL desiccant that can be manufactured at low cost, has a simple manufacturing process, and is suitable for mass production, and a manufacturing method thereof.

As a result of intensive studies to solve the above problems, the present inventor has found that the foamed polymer retains the particulate hygroscopic material and forms voids around the particulate hygroscopic material, Based on this knowledge, further studies have been made and the present invention has been completed.
That is, the present invention is a desiccant for an organic EL element comprising a mixture containing 50 to 300 parts by mass of a particulate hygroscopic material with respect to 100 parts by mass of a thermoplastic resin, and the foamed resin of the desiccant for the organic EL element The layer has a foaming ratio of 1.1 to 2.0 times, the particulate hygroscopic material is held by the foamed resin layer, and voids are formed in at least a part of the periphery of the particulate hygroscopic material. It is the desiccant for organic EL elements characterized by having the structure made.

The desiccant for organic EL elements of the present invention has a structure in which foamed cells are present in the foamed resin layer and voids are formed at least part of the periphery of the particulate hygroscopic material, so that the particulate hygroscopic material is water vapor. By absorbing and expanding, deformation, warpage, etc. do not occur.
The desiccant for organic EL elements of the present invention has a smaller amount of thermoplastic resin to form a resin layer than a desiccant having a non-foamed resin layer with the same volume. The permeation rate of water vapor is increased, the moisture permeability is drastically improved, and an excellent immediate effect and a high moisture absorption force are obtained.
In the desiccant for organic EL elements of the present invention, since the particulate hygroscopic material is dispersed throughout the foam, the amount of moisture absorption is constant over time, and stable moisture absorption performance can be maintained over a long period of time.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the desiccant for an organic EL element of the present invention. In FIG. 1, 1 is a desiccant for organic EL elements, 2 is a foamed resin layer, 3 is a particulate hygroscopic material, 4 is a foam cell, and 5 is a void.
The desiccant 1 for organic EL elements of the present invention is made of a mixture containing a thermoplastic resin and a particulate hygroscopic material in terms of material, and structurally a foamed resin layer having a large number of foam cells (bubbles) 4. 2, the particulate hygroscopic material 3 is held, at least a part of the particulate hygroscopic material 3 is inserted into the foam cell 4, and a void is formed in at least a part of the periphery of the particulate hygroscopic material 3. 5 is formed. The foamed resin layer 2 is a portion excluding the particulate hygroscopic material 3 in the desiccant 1 for organic EL elements, and has a large number of foamed cells 4 and voids 5.
As shown in FIG. 1, the present invention is such that the whole or a part of the particulate hygroscopic material 3 is inserted into the foamed cell 4 and the void 5 exists in the whole or part of the periphery of the particulate hygroscopic material 3. There are features.

The foamed resin layer 2 is made of a thermoplastic resin foam. Specific examples of the thermoplastic resin include olefin resins such as low density polyethylene, ultra low density polyethylene, high density polyethylene, and ethylene-propylene copolymer, ethylene-vinyl acetate copolymer resin, polystyrene resin, and polycarbonate. Resin, polyurethane resin, polyethylene terephthalate, polybutylene terephthalate, polybutylene succinate, polybutylene adipate, polylactic acid, polycaprolactone, and other polyester resins, polyamide 6, polyamide 66, and other polyamide resins, poly (meth) Acrylic acid resin, polyacrylonitrile resin, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene- Kisa fluoroethylene - fluorine-based resins such vinylidene fluoride copolymers.
Among these, in the present invention, a fluorine-based resin is preferable because it has excellent chemical resistance, high heat resistance, and no outgassing. More preferably, it is an amorphous fluorine resin having high moisture permeability and excellent moldability. Examples of the amorphous fluorine-based resin include a tetrafluoroethylene-hexafluoroethylene-vinylidene fluoride copolymer.
Moreover, when the foamed resin layer 2 is an amorphous resin, it is possible to suppress a decrease in moisture permeability due to a crystal structure and a change in moisture permeability due to a cooling method during molding. Therefore, when the foamed resin layer 2 is a crystalline resin, it is necessary to control the moisture permeability by appropriately selecting a cooling method such as rapid cooling or slow cooling when forming the sheet.
Further, the thermoplastic resin, it moisture permeability of itself, to affect moisture absorption performance of the organic EL desiccant of the invention, the moisture permeability, 3g / m ² / 24hr. /0.1mm thickness (JIS
Z0208 cup method) or higher.

As the particulate hygroscopic material 3, there is a material exhibiting a chemical and physical adsorption action, which will be described in detail below.
Examples of the particulate hygroscopic material exhibiting a chemical adsorption action include alkali metal oxides such as sodium oxide and potassium oxide, alkaline earth metal oxides such as calcium oxide, magnesium oxide, strontium oxide and barium oxide, calcium chloride, Metal halides such as magnesium chloride, chromium chloride, iron chloride, metal sulfates such as calcium sulfate, magnesium sulfate, iron sulfate, nickel sulfate, potassium perchlorate, sodium perchlorate, iron perchlorate, perchloric acid Examples thereof include perchlorates such as cobalt, magnesium perchlorate, barium perchlorate and manganese perchlorate, and metal hydrides such as calcium hydride, strontium hydride, barium hydride and lithium aluminum hydride. However, anhydrous salts are preferably used as the metal halide and metal sulfate.

  Examples of the particulate hygroscopic material exhibiting a physical hygroscopic action include silica gel A type, silica gel B type, natural zeolite, synthetic zeolite, sepiolite, alumina silica gel, bentonite, allophane, activated clay, activated carbon and the like. These are also used as gas adsorbents.

  These particulate hygroscopic materials can be used alone or in admixture of two or more according to the desired hygroscopic performance. Further, the average particle diameter of the particulate hygroscopic material 3 is usually preferably 0.5 to 100 μm in order to obtain the effects of the present invention.

In the desiccant 1 for an organic EL device of the present invention, at least one of the particulate hygroscopic materials 3 has an average particle size of 0.5 to 100 μm, a BET specific surface area of 5 to 100 g / m ² , a temperature of 25 ° C., and a relative humidity. Calcium oxide (CaO) having a moisture absorption rate of 3 to 30% after standing for 1 hour in a 50% atmosphere is preferable. This calcium oxide may be used alone or in a mixture with other particulate hygroscopic materials exhibiting a chemical adsorption action and a physical adsorption action. Calcium oxide has the characteristics of a high moisture absorption rate, strong moisture absorption, low toxicity, and low cost.

  The average particle diameter of the calcium oxide used in the present invention is preferably 0.5 to 100 μm, more preferably 1 to 75 μm, and still more preferably 3 to 50 μm. When the average particle size is less than 0.5 μm, the melt viscosity increases and foam extrusion molding becomes difficult. When the average particle size exceeds 100 μm, it is difficult to highly fill the thermoplastic resin with calcium oxide, and the melt tension is further lowered, so that it is difficult to reduce the thickness of the foam sheet.

The BET specific surface area of calcium oxide is preferably 5 to 100 g / m ² , more preferably 10 to 50 g / m ² , and still more preferably 20 to 30 g / m ² . When the BET specific surface area is less than 5 g / m ² , the moisture absorption rate is slow, so that there is a possibility that the immediate effect which is a necessary condition as a desiccant for organic EL elements cannot be obtained. When the BET non-surface area exceeds 100 g / m ² , the reactivity with water vapor becomes remarkably fast, so that the hygroscopic ability is lost during foaming sheet molding, or heat is generated during moisture absorption.

  Furthermore, calcium oxide has a moisture absorption rate of preferably 3 to 30%, more preferably 5 to 25%, still more preferably 7 to 20% after standing for 1 hour in an atmosphere of a temperature of 25 ° C. and a relative humidity of 50%. It is. When the moisture absorption rate is less than 3%, the moisture absorption rate is slow, so that the immediate effect which is a necessary condition for the desiccant for the organic EL element may not be obtained. When the moisture absorption rate exceeds 30%, the reactivity with water vapor is remarkably increased, so that the moisture absorption ability is lost during foamed sheet molding, or heat is generated during moisture absorption.

  The average diameter of the foam cell 4 is preferably 10 to 300 μm. When the average diameter of the foamed cells is less than 10 μm, the effect of improving the moisture permeability due to foam formation is reduced. On the other hand, when the average diameter exceeds 300 μm, a thin sheet cannot be formed and the particulate hygroscopic material is liable to fall off. The foamed cells may be either closed cells, open cells, or a mixture of these, and may be in a state where foamed cells are formed in an indefinite state by breaking during molding. In addition, let the average diameter of the foam cell 4 be the average of the thickness of the desiccant for organic EL elements and the diameter of the foam cell with respect to the flow direction.

  The void 5 is a space portion of the foamed cell 4 that is formed entirely or partly around the particulate hygroscopic material 3 by inserting the whole or part of the particulate hygroscopic material 3 into the foamed cell 4. is there. The void 5 is formed by the whole or a part of the particulate hygroscopic material 3 being pushed into the foamed cell 4 or by the particulate hygroscopic material 3 as a nucleus in the foaming stage. The void 5 may be formed continuously or intermittently. The size of the void 5 is 10% or more, preferably 40% or more of the outer periphery of the particulate hygroscopic material 3, and the thermoplastic resin. Is preferably at least 1 μm or more.

  The desiccant 1 for organic EL elements of the present invention is composed of a mixture obtained by mixing the above-described thermoplastic resin and particulate hygroscopic material, and this mixing ratio is particulate hygroscopic with respect to 100 parts by mass of the thermoplastic resin. It is 50-300 mass parts of an active material, Preferably it is 100-250 mass parts, More preferably, it is 100-200 mass parts. When the mixing ratio of the particulate hygroscopic material is less than 50 parts by mass, the hygroscopic amount is insufficient and an action as a desiccant for organic EL elements is not recognized. On the other hand, when the mixing ratio of the particulate hygroscopic material exceeds 300 parts by mass, mixing with the thermoplastic resin is difficult, the melt viscosity is increased, and the melt tension is further lowered. The problem is that it is significantly lowered and cannot be molded. The mixing ratio of the particulate hygroscopic material can be arbitrarily selected within the above range in consideration of the performance of the hygroscopic material, the thickness of the foamed resin layer, and the like.

The desiccant for an organic EL device of the present invention uses a supercritical fluid as a foaming agent, injects the supercritical fluid into an extrusion machine by an extrusion method, and performs extrusion foaming from a die at the tip of the extrusion machine. It can be manufactured by molding into a sheet. As this extrusion molding machine, a tandem type extruder or a twin-screw kneading extruder in which two extruders are connected can be used. When using a tandem extruder equipped with a T-die for sheet forming, a mixture of thermoplastic resin and particulate hygroscopic material (usually pellets) is charged into the first extruder and melted and kneaded in the barrel. The supercritical fluid is injected at an appropriate injection amount and pressure while the molten resin is cooled to a temperature condition suitable for foaming in the second extruder. A foamed state is formed by releasing the pressure when discharged from the T die. Also, when using a twin-screw kneading extruder, a particulate hygroscopic material is mixed into the molten resin, a supercritical fluid is injected while continuously cooling the resin, and a foamed sheet is produced in the same manner as described above. Can be molded. The resin discharged from the T die is cooled by, for example, a pinch roll method to obtain a sheet having a desired thickness. At this time, by sandwiching with an appropriate pressure, a skin layer is formed on the surface, and a sheet having a uniform surface is obtained.
The mixture of the thermoplastic resin and the particulate hygroscopic material may be produced by uniformly mixing and dispersing each material using a general mixing apparatus such as a twin screw extruder or a pressure kneader. In consideration of moldability, the mixture can be appropriately added with a heat stabilizer and the like in addition to a processing aid such as a lubricant composed of polyethylene wax, higher fatty acid and the like, as long as the effects of the present invention are not impaired. .

In the production of the desiccant 1 for an organic EL device of the present invention, supercritical nitrogen or supercritical carbon dioxide, which is a supercritical fluid, is used as a foaming agent. The reason for using these in particular is that when the supercritical fluid is added to a mixture of a thermoplastic resin and a particulate hygroscopic material, a foamed structure is formed with the particulate hygroscopic material as a core. This is because the gap 5 can be provided around the material. At the same time, the foam cell 4 is formed in the foam resin layer 2. Since the supercritical fluid plays the role of a processing aid, it is possible to mold a compact that is highly filled with a particulate hygroscopic material.
Considering the reactivity with the particulate hygroscopic material, the influence on the organic EL element, and the size of the foam cell, supercritical nitrogen is preferable. Also, when the particulate hygroscopic material is calcium oxide, inert supercritical nitrogen is preferable, and supercritical nitrogen is also preferable in order to make the foam cell indefinite and increase the hygroscopic effect. The injection amount of these supercritical fluids is determined by calculating from the required expansion ratio and the discharge amount of the molten resin.

The expansion ratio of the foamed resin layer 2 constituting the present invention (the specific gravity of the non-foamed body / the specific gravity of the foamed body) is 1.1 to 2.0 times, and preferably 1.3 to 1.7 times. When the expansion ratio is less than 1.1 times, a sufficient improvement effect of the moisture absorption rate by foaming is not recognized. On the other hand, when the expansion ratio is larger than 2.0 times, the mechanical strength may be lowered.
Moreover, it is preferable that the particulate hygroscopic material 3 and the foamed cells 4 are uniformly present in the foamed resin layer 2. By doing so, the amount of moisture absorption becomes constant over time over a long period of time, and stable moisture absorption performance can be obtained. Therefore, the humidity in the organic EL element is maintained in a low state.

  Although the thickness of the foam sheet used for the desiccant for organic EL elements of the present invention is not limited, it is usually 50 to 500 μm, preferably 100 to 200 μm. When the thickness of the foamed sheet is less than 50 μm, a sufficient amount of the particulate hygroscopic material cannot be taken and the required hygroscopic ability may not be obtained. On the other hand, if the thickness of the foamed sheet exceeds 500 μm, the thickness of the entire organic EL element is increased, which makes it unsuitable for applications requiring downsizing of mobile phones and the like. The shape of the desiccant for the organic EL element may be appropriately selected according to the purpose of use of the final product, and is not particularly limited, such as a square or a circle.

  The method for fixing the desiccant for organic EL elements of the present invention in the organic EL element is not particularly limited as long as it can be reliably fixed in the organic EL element. For example, a method of fixing using an adhesive, a pressure-sensitive adhesive or a thermoplastic resin can be mentioned. In particular, a method of fixing with an adhesive is preferable because it is simple and excellent in workability. As the pressure-sensitive adhesive, a commercially available solventless pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive or a rubber-based pressure-sensitive adhesive can be used. An acrylic pressure-sensitive adhesive is preferred because of its excellent heat resistance.

(Examples 1-3, Comparative Examples 1-3)
A. Production of Foamed Sheet As the thermoplastic resin, amorphous fluororesins shown in Table 1 (Examples 1 and 2 and Comparative Examples 1 and 2 are THV220G, Example 3 and Comparative Example 3 are THV310G, both manufactured by Sumitomo 3M Limited) ), As a particulate hygroscopic material, calcium oxide (highly active quicklime: manufactured by Ube Materials) shown in Table 1 is used, and a mixture of both having a composition ratio (parts by mass) shown in Table 2, Using a first extruder (φ65 mm, L / D = 32), mixing is performed, and in a second extruder (φ90 mm, L / D = 30, T-die: surface length 300 mm), supercritical nitrogen is used as a blowing agent. The foamed sheet was molded by using the same (Examples 1 to 3, Comparative Examples 1 and 3. In addition, Comparative Example 2 could not be molded). Table 1 shows the thickness of the obtained foamed sheet and the expansion ratio. The expansion ratio was determined by the formula: expansion ratio = (specific gravity of non-foamed sheet) / (specific gravity of foamed sheet).
B. Measurement of Hygroscopic Capacity A sample of 5 cm × 5 cm was prepared for each molded foam sheet, and the moisture absorption rate in an atmosphere at a temperature of 25 ° C. and a relative humidity of 50% after a predetermined time was determined. The results are shown in Table 3 and FIG. The moisture absorption rate is expressed by the formula: moisture absorption rate = {(mass of foam sheet after moisture absorption) − (mass of foam sheet before moisture absorption).
} × 100 / (mass of foam sheet before moisture absorption).
C. Confirmation of generation of deformation / warpage of foam sheet after moisture absorption The state of deformation / warpage of the sample after standing for 1 hour in an atmosphere at a temperature of 25 ° C. and a relative humidity of 50% was visually observed. The results are shown in Table 2.

(Evaluation)
The desiccant for an organic EL device of the present invention comprising the foamed sheet of the example not only has a significantly high moisture absorption compared to the non-foamed sheet, but also has an excellent initial moisture absorption rate, high moisture absorption performance, and after moisture absorption. Deformation and warpage of the molded sheet can be prevented.

It is sectional drawing which shows an example of the desiccant for organic EL elements of this invention. It is a figure which shows the relationship between a moisture absorption rate and measurement time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Desiccant for organic EL elements 2 ... Foamed resin layer 3 ... Particulate hygroscopic material 4 ... Foam cell 5 ... Gap

Claims (5)

  An organic EL element desiccant comprising a mixture containing 50 to 300 parts by mass of a particulate hygroscopic material with respect to 100 parts by mass of a thermoplastic resin, wherein the foamed resin layer of the desiccant for organic EL element has an expansion ratio of 1.1 to 2.0 times, the particulate hygroscopic material is held in the foamed resin layer, and has a structure in which voids are formed in at least a part of the periphery of the particulate hygroscopic material. An organic EL device desiccant characterized by the above.   The desiccant for an organic EL device according to claim 1, wherein the amount of outgas generated by heating at a temperature of 85 ° C for 10 minutes and at a temperature of 105 ° C for 5 minutes is 80 ppm or less and 100 ppm or less, respectively.   The desiccant for an organic EL device according to claim 1, wherein the thermoplastic resin is an amorphous fluorine-based resin. At least one particulate hygroscopic material has an average particle diameter of 0.5 to 100 μm, a BET specific surface area of 5 to 100 g / m ² , a moisture absorption after standing for 1 hour in an atmosphere of a temperature of 25 ° C. and a relative humidity of 50%. The desiccant for an organic EL device according to claim 1, which is a calcium oxide having a rate of 3 to 30%. The mixture containing 50 to 300 parts by mass of the particulate hygroscopic material with respect to 100 parts by mass of the thermoplastic resin is foamed using supercritical nitrogen or supercritical carbon dioxide. The manufacturing method of the desiccant for organic EL elements of description.

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