JP2014170736A - Method for manufacturing glass substrate for organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass substrate for an organic EL element in which a light extraction layer having high light extraction efficiency and flat surface can be inexpensively manufactured.SOLUTION: In a method for manufacturing a glass substrate 3 for an organic EL element, on a glass plate 1 having at least one surface which is an uneven surface 1a, glass powder are coated and burned at a temperature of (softening point of glass powder plus 100°C) or less, thereby capable of forming a light extraction layer 2.

Description

  The present invention relates to a method for producing a glass substrate for an organic EL element on which a light extraction layer is formed.

  In recent years, energy consumed in living spaces such as homes has increased due to the spread of home appliances, increase in size, and increase in functionality. In particular, because of the high energy consumption in lighting applications, high-efficiency alternative lighting to replace fluorescent lighting that is widely used as lighting for daily life is being actively studied, and LED lighting has begun to be adopted as an alternative to incandescent bulbs. Yes.

  Illumination light sources are classified into “directional light sources” that illuminate a limited range and “diffuse light sources” that illuminate a wide range. Since LED illumination corresponds to a “directional light source”, an alternative light source for a fluorescent lamp corresponding to a “diffuse light source” is desired, and organic EL (electroluminescence) illumination is a promising candidate for such an alternative light source. It is believed that.

  The organic EL element includes a glass substrate, a transparent conductive film as an anode, an organic EL layer including one or more light-emitting layers made of an organic compound exhibiting electroluminescence that emits light by current injection, and a cathode. It is an element. As the organic EL layer used in the organic EL element, a low molecular dye material or a conjugated polymer material is used. When forming as a light emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron A laminated structure with an injection layer or the like is formed. An organic EL layer having such a laminated structure is disposed between the anode and the cathode, and by applying an electric field to the anode and the cathode, holes injected from the transparent electrode that is the anode and those injected from the cathode Electrons recombine in the light emitting layer, the emission center is excited by the recombination energy, and light is emitted.

  The organic EL element has a luminous efficiency equivalent to that of a liquid crystal or a plasma display that is widely used as a thin television, and is being adopted for use in a mobile phone or a display. However, it is said that the luminance of the light source for illumination is not yet sufficient for practical use, and further improvement in luminous efficiency is required.

  One of the causes of low brightness is as follows. That is, the refractive index nd of the organic EL layer is 1.8 to 1.9, and the refractive index nd of the transparent conductive film is 1.9 to 2.0. On the other hand, the refractive index nd of the glass substrate is usually about 1.5. For this reason, in the conventional organic EL device, light emitted from the organic EL layer is reflected at the interface between the transparent conductive film and the glass substrate due to a large difference in refractive index between the transparent conductive film and the glass substrate. There was a problem that light could not be extracted efficiently.

  Furthermore, due to the difference in refractive index between the glass substrate and air, a loss similar to that described above occurs. That is, when light incident on a glass substrate having a refractive index nd of about 1.5 enters the air having a refractive index nd of 1.0, light is reflected at the interface, and light trapped in the glass substrate is generated. was there.

Therefore, in an organic EL element used as a light source for illumination, it has been studied to interpose a light extraction layer capable of efficiently extracting light emitted from the organic EL layer between the transparent conductive film and the glass substrate. For example, Patent Document 1 discloses a glass substrate in which a light extraction layer is formed by applying and baking a high-refractive-index low-melting glass on an uneven surface of a glass plate.
This improves the light extraction efficiency by reducing the light confined in the organic layer by the high refractive index glass and reducing the light confined in the glass substrate by scattering the light on the uneven surface. Is intended.

JP 2010-198797 A

  By the way, in order to form a transparent conductive film on the light extraction surface, it is desirable that the surface of the light extraction layer is flat. However, when the low melting point glass described in Patent Document 1 is used, if the firing temperature is increased to such an extent that the above-described flat light extraction layer surface can be obtained, the uneven shape on the surface of the glass plate tends to disappear, and the surface unevenness There is a problem that it is difficult to enjoy the scattering effect.

  The objective of this invention is providing the manufacturing method of the glass substrate for organic EL elements with high light extraction efficiency.

  The manufacturing method of the glass substrate for organic EL elements of this invention apply | coats glass powder on the glass plate whose at least one surface is an uneven surface, and bakes it at the temperature below (softening point of glass powder +100 degreeC). It is characterized by. Here, “the temperature below (softening point of glass powder + 100 ° C.)” means a temperature that is 100 ° C. higher than or lower than the softening point of the glass constituting the glass powder.

  If the said structure is employ | adopted, at the time of baking for forming a light extraction layer, the viscosity of glass will not become low too much and the erosion of the unevenness | corrugation by glass will not occur easily. Therefore, it is possible to easily produce a glass substrate for an organic EL element that can efficiently extract light emitted from the organic layer into the air.

  The method for producing a glass substrate for an organic EL device of the present invention is characterized by using glass powder having a softening point of 525 ° C. or higher.

  If the said structure is employ | adopted, the erosion of the unevenness | corrugation on the substrate surface can be suppressed effectively.

In the present invention, a glass powder having a refractive index nd of 1.8 to 2.2, 0.1% or more of ZrO ₂ in terms of mol%, and a content of Nb ₂ O ₅ of 15% or less. It is preferable to use it. Here, the refractive index nd is a value measured by ellipsometry.

If the glass powder having the above structure is used, a light extraction layer having a refractive index close to that of the transparent conductive film can be formed. Therefore, reflection of light at the interface between the transparent conductive film and the light extraction layer can be reduced, and light extraction efficiency can be reduced. Can be increased. Moreover, since it is not necessary to use an expensive raw material, the light extraction layer forming glass can be supplied at low cost. Furthermore, since ZrO ₂ is contained in the glass composition, the chemical resistance of the glass is high, and the light extraction layer formed using this glass is etched by a chemical solution such as an acid or alkali solution in the subsequent device manufacturing process. It is hard to become cloudy.

In the present invention, it is preferable to use glass powder made of bismuth-based glass. In the present invention, “bismuth-based glass” means glass containing 10 mol% or more of Bi ₂ O ₃ as a glass composition.

  If the said structure is employ | adopted, a glass powder with a low softening point can be selected easily, and it becomes possible to perform baking for light extraction layer formation at low temperature.

In the present invention, Bi ₂ O ₃ 10 to 35%, B ₂ O ₃ 20 to 35%, SiO _{2 over} 5% to 35%, Al ₂ O ₃ 0 to 10%, ZnO 0 to 10 in terms of mol%. %, ZrO ₂ 1-8% containing glass powder is preferably used. Further, by _{mol%, Bi 2 O 3 10~35%,} B 2 O 3 20~35%, SiO 2 + Al 2 O 3 21~45%, 0~10% ZnO, ZrO 2 0.1~10% It is preferable to use glass powder contained. Here, “SiO ₂ + Al ₂ O ₃ ” means the total content of SiO ₂ and Al ₂ O ₃ .

  Since the glass having the above configuration has high weather resistance, it is easy to make fine powder when producing glass powder. As a result, a light extraction layer having a smooth surface necessary for forming a transparent conductive film such as ITO can be formed by baking at a low temperature in a short time. In particular, when a light extraction layer is formed on a glass plate having an uneven surface, it is possible to form a light extraction layer having a flat surface while maintaining the uneven surface of the glass plate. A transparent conductive film having good film quality can be formed on the layer.

  In the present invention, it is preferable to use glass powder that does not substantially contain PbO. Here, “substantially does not contain PbO” means that it is not intentionally contained, and more objectively means that PbO is 0.1% or less in terms of mol%.

  If the said structure is employ | adopted, there is no possibility of causing environmental pollution in the manufacture process etc. of glass powder.

The typical sectional view showing the glass substrate for organic EL devices produced by the method of the present invention is shown. It is typical sectional drawing which shows an organic EL element.

  A method for producing the glass substrate for an organic EL device of the present invention will be described.

  First, a glass plate having an uneven surface is prepared.

  As for the glass plate 1, the surface by the side of the light extraction layer 2 becomes the uneven surface 1a as shown in FIG. By setting the surface of the glass plate 1 on the light extraction layer 2 side to be an uneven surface 1a, reflection of light at the interface between the light extraction layer 2 and the glass plate 1 can be reduced, and light can be easily taken into the glass plate 1. The glass plate 1 having the uneven surface 1a formed on the surface can be produced, for example, by subjecting a glass plate having a flat surface to a method such as a sand blast method, a sol-gel spray method, or an etching method. Or it can also produce by press-molding a glass plate with the metal mold | die with which the unevenness | corrugation was formed on the surface, or roll-forming a molten glass with the roll by which the unevenness | corrugation was formed on the surface. In addition to the light extraction layer 2 side, the uneven surface 1a may be formed on the surface facing the uneven surface 1a. Moreover, the uneven surface 1a does not necessarily need to be formed over the entire surface of the glass plate 1, and may be formed, for example, only at the central portion of the surface of the glass plate 1. The surface roughness Ra of the concavo-convex surface 1a can be set in consideration of the required degree of light scattering from the organic EL element. For example, the surface roughness Ra is preferably in the range of 0.05 to 2 μm, and more preferably in the range of 0.05 to 1.5 μm. If the surface roughness Ra of the uneven surface 1a is too small, sufficient light extraction efficiency may not be obtained. On the other hand, if the surface roughness Ra of the uneven surface 1a is too large, sufficient light extraction efficiency cannot be obtained, and the amount of glass for filling the uneven surface 1a increases, which may reduce the transmittance.

  Moreover, the light extraction layer forming material containing glass powder is prepared. In the following description of the glass powder, “%” means mol% unless otherwise specified.

  As the glass powder, it is preferable to use a glass powder having a softening point of 525 ° C. or higher, 530 ° C. or higher, particularly 550 ° C. or higher. When the softening point of the glass powder is too low, the viscosity of the glass tends to decrease during firing for forming the light extraction layer, and the unevenness on the surface of the glass plate is easily eroded and lost. If the softening point of the glass is too high, it becomes difficult to form a smooth fired film at a low temperature, for example, 600 ° C. or lower. Therefore, the softening point of the glass is preferably 590 ° C. or less.

Moreover, it is preferable to use what consists of glass whose refractive index nd exists in the range of 1.8-2.2 as glass powder. When the refractive index n _d of the glass is less than 1.8, too large difference in refractive index of the transparent conductive film and the light extraction layer increases the percentage of reflected light at the interface therebetween, the light extraction efficiency It becomes difficult to increase. On the other hand, when the refractive index nd of the high softening point glass exceeds 2.2, the difference in refractive index at the light extraction layer / glass plate interface increases, and the light extraction efficiency may not be improved.

As the glass powder, it is preferable to use one made of glass containing ZrO ₂ 0.1% or more. ZrO ₂ is a component that increases the refractive index of the glass and is a component that improves the acid resistance of the glass.

The glass powder is preferably made of glass having a composition in which the content of Nb ₂ O ₅ is limited to 15% or less, 10% or less, 8% or less, and particularly 5% or less. Nb ₂ O ₅ is a component that increases the refractive index of glass, but since the raw material is expensive, it is desired to reduce the content as much as possible. For the same reason, it is desirable to reduce the contents of Gd ₂ O ₅ and La ₂ O ₃ as much as possible. The total amount of these components (Nb ₂ O ₅ + Gd ₂ O ₃ + La ₂ O ₃ ) is preferably 30% or less, more preferably 15% or less, 10% or less, 8% or less, and particularly preferably 5% or less. .

As the glass powder, bismuth-based glass containing 10% or more of Bi ₂ O ₃ , more specifically, Bi ₂ O ₃ 10 to 35%, B ₂ O ₃ 20 to 35%, SiO ₂ more than 35 to 35% , Al ₂ O ₃ 0 to 10%, ZnO 0 to 10%, ZrO ₂ 1 to 8% glass or Bi ₂ O ₃ 10 to 35%, B ₂ O ₃ 20 to 35% in terms of mol% , SiO ₂ + Al ₂ O ₃ 21 to 45%, ZnO 0 to 10%, ZrO ₂ 0.1 to 10% is preferably used. The reason for limiting the glass composition in this way is shown below.

Bi ₂ O ₃ is a component that lowers the softening point of glass and raises the refractive index. The content is preferably 10 to 35%, 20 to 35%, particularly 21 to 33%, and more preferably 22 to 31%. When the content of Bi ₂ O ₃ is too small, the softening point of the glass is excessively increased and it becomes difficult to fire at a low temperature. On the other hand, when the content of Bi ₂ O ₃ is excessive, the material cost is increased.

B ₂ O ₃ is a component that forms a glass skeleton and expands the vitrification range, and its content is 20 to 35%, particularly 21 to 34%, 22 to 33%, and further 23 to 33%. It is preferable. When the content of B ₂ O ₃ is too small, the glass is easily crystallized during firing, and it becomes difficult to obtain a smooth fired film. On the other hand, when the content of B ₂ O ₃ is too large, the softening point of the glass is excessively increased and it is difficult to fire at a low temperature. Moreover, the weather resistance of glass falls and it becomes difficult to pulverize at the time of powder preparation.

SiO ₂ is a component that forms a glass skeleton, raises the softening point, stabilizes the glass, and facilitates obtaining a smooth surface after firing. Moreover, there exists an effect which improves the weather resistance of glass. The content of SiO ₂ is preferably more than 5 to 35%, particularly 15 to 34%, 20 to 34%, 25 to 34%, 26 to 34%, and more preferably 27 to 34%. If the SiO ₂ content is too low, the glass can be lowered in temperature, but at the same time, it is easy to crystallize, which is not preferable. Moreover, when the weather resistance of glass falls and powder is produced, it becomes difficult to make fine powder. On the other hand, when the content of SiO ₂ is too large, the softening point of the glass is excessively increased and it is difficult to fire at a low temperature.

Al ₂ O ₃ is a component that can stabilize the glass and raise the softening point, and its content is preferably 0 to 10%, particularly 0 to 9%, and more preferably 0 to 8%. When the content of Al ₂ O ₃ is too large, the softening point of the glass is excessively increased and it is difficult to fire at a low temperature.

The total content of SiO ₂ and Al ₂ O ₃ is 21 to 45%, particularly 22 to 40%, more preferably 25 to 38%. If the total content of SiO ₂ and Al ₂ O ₃ is too small, the weather resistance of the glass is lowered, and it becomes difficult to make fine powder when producing powder. On the other hand, if the total amount of SiO ₂ and Al ₂ O ₃ is too large, the softening point of the glass becomes too high. When the total content of SiO ₂ and Al ₂ O ₃ is limited to the above range, the content of SiO ₂ is preferably 21 to 45%, particularly preferably 22 to 45%, and the content of Al ₂ O ₃ The amount is preferably 0 to 10%, particularly 1 to 9%.

  ZnO is a component having an effect of lowering the softening point of glass, and its content is preferably 0 to 10%, particularly 0 to 9%, and more preferably 0 to 8%. If the ZnO content is too high, the stability of the glass is lowered, and in some cases, crystallization occurs after firing, making it difficult to obtain a smooth surface.

ZrO ₂ is a component that improves the refractive index of glass, and is also a component that improves the chemical resistance of glass. The ZrO ₂ content is preferably 0.1 to 10%, 0.1 to 8%, particularly 1 to 8%, 2 to 7%, and more preferably 3 to 6%. When the content of ZrO ₂ is too small, the effect of improving the refractive index becomes insufficient. In addition, chemical resistance decreases. On the other hand, if the content of ZrO ₂ is too large, the glass is easily crystallized during firing, and it becomes difficult to obtain a smooth glass surface, and the softening point of the glass is too high, making it difficult to fire at a low temperature. Become.

  Moreover, the said bismuth-type glass can add a various component in the range which does not impair the required characteristic.

  For example, alkaline earth metal oxides of MgO, CaO, SrO and BaO are components that lower the softening point of the glass and adjust the thermal expansion coefficient, and the total amount is 0 to 20%, especially 0 to 15%. Furthermore, 0 to 12% can be contained. If the total amount of these components is too large, the thermal expansion coefficient becomes too large, which is not preferable. In addition, the content of each component of these alkaline earth metal oxides is preferably 0 to 6%.

Furthermore, in order to lower the softening point of the glass, the total amount of alkali metal oxides of Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, Rb ₂ O is up to 5%, and the glass is stabilized. Y ₂ O ₃ , La ₂ O ₃ , Ta ₂ O ₅ , SnO ₂ , TiO ₂ , Nb ₂ O ₅ , P ₂ O ₅ , and water resistance, acid resistance, and alkali resistance _CuO, can be added CeO _2, V _{2 O 5} and the like up to 15% in total.

  PbO is a component that lowers the melting point of glass, but it is also an environmentally hazardous substance, so substantial introduction should be avoided.

  The bismuth-based glass having the above composition exhibits a refractive index nd of 1.8 to 2.2 close to that of a transparent conductive film. Further, the glass is stable, and for example, a smooth fired film can be obtained without crystallization at a temperature of 600 ° C. or lower.

  Moreover, since the bismuth-type glass of the said composition has high weather resistance, it is easy to pulverize by wet grinding. If the particle size of the glass powder is small, the glass softens and flows by heat treatment at a lower temperature or in a shorter time than when the particle size is large. Therefore, the firing conditions for forming the light extraction layer can be set at a low temperature and in a short time, and even if there is an uneven surface on the glass plate surface, it can be fired without being eroded or lost.

The glass powder can be prepared by preparing the raw materials so as to become the glass having the above composition, melting, forming, pulverizing and classifying. The particle size of the glass powder, the average particle diameter _{D 50} 0.3 to 2.0 .mu.m, the maximum particle diameter _{D max} may be desirable to use those 10μm or less. When either one of the average particle diameter D ₅₀ and the maximum particle diameter D _max is greater than the upper limit, it becomes difficult to produce a smooth fired film. Also when the average particle diameter D ₅₀ less than 0.3 [mu] m, the dispersion of the paste or the like becomes difficult, which is not preferable.

  The light extraction layer forming material may include ceramic particles as scattering particles. When ceramic particles are included, the content is preferably 20% by volume or less, particularly preferably 0.5 to 15% by volume. Various materials can be used as the ceramic particles. For example, alumina, zircon, zirconia, mullite, silica, cordierite, titania, titanic acid compound, tin oxide, various inorganic pigments, etc. can be used alone or in combination. Can be used.

  The light extraction layer forming material may include a ceramic powder. When ceramic powder is included, the mixing amount is 80 to 100% by volume (more preferably 85 to 99.5% by volume) of glass powder, and 0 to 20% by volume (more preferably 0.5 to 15% by volume) of ceramic powder. Preferably there is. Various materials can be used as the ceramic powder. For example, alumina, zircon, zirconia, mullite, silica, cordierite, titania, titanic acid compound, tin oxide, various inorganic pigments, etc. can be used alone or in combination. Can be used.

  The light extraction layer forming material is preferably used in the form of a paste. The proportion of the powder material in the whole paste is generally about 30 to 90% by mass. In the case of making a paste, in addition to the powder material, a thermoplastic resin, a plasticizer, a solvent, and the like are included.

  The thermoplastic resin is a component that increases film strength after drying and imparts flexibility. As for the ratio of the thermoplastic resin to the whole paste, about 0.1-20 mass% is common. As the thermoplastic resin, polybutyl methacrylate, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, ethyl cellulose and the like can be used, and these are used alone or in combination.

  The plasticizer is a component that controls the drying speed and imparts flexibility to the dry film. As for the ratio of the plasticizer to the whole paste, about 0-10 mass% is common. As the plasticizer, butylbenzyl phthalate, dioctyl phthalate, diisooctyl phthalate, dicapryl phthalate, dibutyl phthalate and the like can be used, and these are used alone or in combination.

  The solvent is a component that pastes the material. The content of the solvent in the entire paste is generally about 10 to 30% by mass. As the solvent, for example, terpineol, diethylene glycol monobutyl ether acetate, 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate or the like can be used alone or in combination.

  The paste can be produced by mixing the above-described light extraction layer forming material, thermoplastic resin, plasticizer, solvent and the like at a predetermined ratio and kneading them uniformly.

  Next, the light extraction layer forming material is applied onto the glass plate. When the light extraction layer forming material is used in the form of a paste, it is applied to a predetermined film thickness using a method such as a screen printing method or a batch coating method and dried. Further, instead of making a paste, the light extraction layer forming material can be applied onto the glass plate by employing a method such as a green sheet method, electrostatic coating, or electrophoresis.

  Thereafter, firing is performed at a temperature of (glass powder softening point + 100 ° C.) or lower, preferably (glass powder softening point + 70 ° C.) or lower. The firing time is preferably about 5 to 60 minutes. Thus, the glass substrate 3 for organic EL elements in which the light extraction layer 2 was formed on the glass plate 1 can be obtained. If the firing temperature is too low or the holding time is too short, sintering becomes insufficient and it becomes difficult to form a dense light extraction layer. On the other hand, if the firing temperature is too high or the holding time is too long, the unevenness formed on the surface of the glass plate tends to be eroded. Further, bubbles are generated during firing, and it becomes difficult to obtain a smooth light extraction layer, which is not preferable.

  As shown in FIG. 1, the glass substrate 3 for an organic EL element thus obtained has a glass plate 1 having at least one surface which is an uneven surface 1 a and a light extraction layer formed on the uneven surface 1 a. 2.

  The obtained glass substrate for an organic EL element preferably has a surface roughness Ra of the surface 2a of the light extraction layer 2 of 1 μm or less, 0.7 μm or less, particularly 0.5 μm or less. The smaller the surface roughness Ra of the surface 2a of the light extraction layer 2, the easier the film formation of the transparent conductive film 4 formed thereon. An excessively large surface roughness Ra is not preferable because the film quality of the transparent conductive film becomes nonuniform and adversely affects the light emission of the organic EL device.

  In addition, the obtained glass substrate for an organic EL element preferably has a haze value of 30% or more, 40% or more, 50% or more, 60% or more, particularly 70% or more. If the haze value is low, sufficient light cannot be extracted.

  Next, the example of the organic EL element produced using the above-mentioned glass substrate for organic EL elements is demonstrated.

  For example, as shown in FIG. 2, the organic EL element has a transparent conductive film 4 formed on the light extraction layer 2 of the glass substrate 3, and an organic EL layer 5 is formed on the transparent conductive film 4. A cathode 6 is formed on the organic EL layer 5. That is, the organic EL layer 5 is formed between the transparent conductive film 4 and the cathode 6. In the present embodiment, the transparent conductive film 4 functions as an anode. The organic EL layer 5 includes a light emitting layer (not shown), and a hole injection layer, a hole transport layer, and the like are formed between the light emitting layer and the transparent conductive film 4 as necessary. Moreover, an electron transport layer, an electron injection layer, etc. are formed between the light emitting layer and the cathode 6 as needed. Light emitted from the light emitting layer of the organic EL layer 5 passes through the transparent conductive film 4 and the glass substrate 3 and is extracted outside.

The transparent conductive film 4 is not particularly limited as long as it functions as an anode in the organic EL element. For example, a composite oxide thin film having conductivity such as indium tin oxide (ITO), aluminum zinc oxide (AZO), and indium zinc oxide (IZO) can be used. In the present invention, indium tin oxide is particularly preferably used. The transparent conductive film 4 may be formed on the light extraction layer 2 or may be formed on the light extraction layer 2 via a protective film such as SiO ₂ or Ta ₂ O ₅ .

  The organic EL element may be hermetically sealed using glass, epoxy resin, or the like in order to block moisture and oxygen in the air.

Hereinafter, the present invention will be described in detail based on examples.
[Evaluation of glass powder sample]
Table 1 shows the light extraction layer forming glass powders (Sample Nos. 1 to 11), respectively.

  Each glass powder sample was prepared as follows.

First, each raw material was prepared and uniformly mixed so that the glass composition shown in Table 1 was obtained in mol%. Next, the mixed raw materials were put in a platinum crucible and melted at 1300 ° C. for 2 hours, and then the molten glass was formed into a thin plate shape. Next, by pulverizing them in a ball mill average particle diameter _{D 50 0.8~2.0μm,} maximum particle diameter _{D max} to obtain a glass powder sample of 5 [mu] m.

The obtained glass powder sample was measured for the thermal expansion coefficient α, softening point Ts, refractive index nd, and average particle size D ₅₀ as follows. The results are shown in Table 1.

  The thermal expansion coefficient was measured as follows. First, each glass powder sample was press-molded, and the obtained molded body was fired at 580 ° C. for 10 minutes, and then polished into a cylindrical shape having a diameter of 4 mm and a length of 40 mm. Using this sample, the thermal expansion coefficient in the temperature range of 30 to 300 ° C. was determined in accordance with JIS (Japanese Industrial Standards) R3102.

  The softening point of the glass was measured using a macro type differential thermal analyzer, and the value of the fourth inflection point was taken as the softening point.

  Refractive index nd was evaluated by measuring ellipso in a region of about 10 μmφ by preparing a plate-shaped sample.

The particle size was measured using a laser diffraction particle size distribution meter, was determined a value of D _50.

As shown in Table 1, no. Each glass powder sample of 1 to 10 has a thermal expansion coefficient of 69.2 to 83.4 × 10 ⁻⁷ / ° C., a softening point of 528 to 565 ° C., and a refractive index of 1.810 to 1.926. Range.
[Evaluation of glass substrate]
Sample No. in Table 1 1 and no. A glass substrate was prepared and evaluated using 11 glass powder samples.

  First, ethyl cellulose (manufactured by Dow Chemical Company, weight average molecular weight (Mw) of about 180,000) is used as the thermoplastic resin, terpineol is used as the organic solvent, and the weight ratio of glass powder: resin binder: organic solvent is 70: 2: 28. These were mixed and kneaded by a three-roll mill to produce a glass paste.

Further, as a glass plate, “SS-1” manufactured by Nippon Electric Glass Co., Ltd. (thickness 1.8 mm, thermal expansion coefficient 84 × 10 ⁻⁷ / ° C., refractive index nd1.5), “OA-” manufactured by Nippon Electric Glass Co., Ltd. 10G "(thickness 0.7 mm, thermal expansion coefficient 35 × 10 ⁻⁷ / ° C., refractive index nd1.52),“ QDE-002 ”manufactured by Nippon Electric Glass Co., Ltd. (thickness 0.7 mm, thermal expansion coefficient 72 × 10 ^{− 7} / ° C., refractive index nd1.64) and soda glass (thickness 1.8 mm, refractive index nd1.5) manufactured by Nippon Sheet Glass Co., Ltd. were each divided into 5 cm squares to obtain glass plate samples. Furthermore, an uneven surface having a surface roughness Ra of 0.6 microns was formed on one surface by subjecting the surface to a surface by sandblasting using alumina powder (# 1200).

  Next, the glass paste produced as described above was applied onto a glass plate with an applicator, dried at 120 ° C. for 10 minutes, and then baked at 570 ° C. and 600 ° C. for 20 minutes. In this way, samples (Nos. 101 to 116) were obtained.

  About the obtained board | substrate sample, surface roughness Ra of the light extraction layer surface, haze value, total light transmittance Tt, diffused transmittance Td, and parallel-line transmittance Tp were evaluated. The results are shown in Tables 2 and 3.

As apparent from Tables 2 and 3, Sample No. baked at a temperature of (softening point + 100 ° C.) or lower. 101-112 had a haze value as high as 35.1% or more.

The haze value, total light transmittance Tt, diffuse transmittance Td, and parallel line transmittance Tp were measured using “TM double beam type automatic haze computer” manufactured by Suga Test Instruments Co., Ltd. The higher the haze value, the higher the light scattering property of the glass substrate.
In contrast, Sample No. as a comparative example. Nos. 113 to 116 were fired at a temperature of (softening point + 100 ° C.) or higher, and the haze value was as low as 19.3% or less.

DESCRIPTION OF SYMBOLS 1 Glass plate 1a Irregular surface 2 Light extraction layer 2a Surface of light extraction layer 3 Glass substrate for organic EL elements 4 Transparent conductive film 5 Organic EL layer 6 Cathode

Claims (7)

  A method for producing a glass substrate for an organic EL device, comprising applying a glass powder on a glass plate having at least one surface having an uneven surface and firing at a temperature of (softening point of glass powder + 100 ° C.) or lower.   The method for producing a glass substrate for an organic EL device according to claim 1, wherein a glass powder having a softening point of 525 ° C or higher is used. A glass powder having a refractive index nd of 1.8 to 2.2, 0.1% or more of ZrO ₂ in terms of mol%, and 15% or less of Nb ₂ O ₅ is used. The manufacturing method of the glass substrate for organic EL elements of Claim 1 or 2.   The method for producing a glass substrate for an organic EL device according to any one of claims 1 to 3, wherein a glass powder made of bismuth glass is used. Bi ₂ O ₃ 10-35%, B ₂ O ₃ 20-35%, SiO _{2 over} 5% -35%, Al ₂ O ₃ 0-10%, ZnO 0-10%, ZrO ₂ 1 The glass powder containing -8% is used, The manufacturing method of the glass substrate for organic EL elements in any one of Claims 1-4 characterized by the above-mentioned. Bi ₂ O ₃ 10-35%, B ₂ O ₃ 20-35%, SiO ₂ + Al ₂ O ₃ 21-45%, ZnO 0-10%, ZrO ₂ 0.1-10% Glass powder is used, The manufacturing method of the glass substrate for organic EL elements in any one of Claims 1-4 characterized by the above-mentioned. The method for producing a glass substrate for an organic EL device according to any one of claims 1 to 6, wherein glass powder containing substantially no PbO is used.