JPS6322618B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin-sealed light emitting diode. Conventionally, a light emitting diode has been covered (sealed) with a transparent resin at least at least the surface that contributes to light emission in order to protect the surface that contributes to light emission and increase luminous efficiency. Here, as the sealing resin,
Epoxy resin compositions are widely used. However, it has not been easy to obtain a cured product from an epoxy resin composition that does not change color during curing (does not change color) and does not change color over time. However, when using an epoxy resin composition consisting of an epoxy resin, a polycarboxylic anhydride as a curing agent, and a tertiary amine or its organic acid salt as a curing accelerator, a transparent cured product with relatively little discoloration (coloring) can be obtained. Improvements in this direction have been made as it has become known that this can be achieved. For example, strong bases such as diaza-bicyclo-alkene compounds or their salts are used as curing accelerators, organic acid metal salts such as tin octylate are used in combination with these, or organic phosphites and hindered phenols are added. Or, a small amount of blue or purple coloring agent is added to perform so-called "blueing". However, although some improvement was seen, it was not sufficient, and in particular, it was not possible to improve the coloring caused by leaving the light emitting diode sealed with resin in a high temperature atmosphere for a long time. The present invention solves these problems. That is, the present invention provides a light emitting diode in which at least a surface contributing to light emission is covered with a cured product of an epoxy resin composition containing an epoxy resin, a polycarboxylic acid anhydride, and a curing accelerator. Among them, methylhexahydrophthalic anhydride is the main component as a polycarboxylic anhydride, and its isomers 4-methylhexahydrophthalic anhydride () and 3-methylhexahydrophthalic anhydride () ()/ () is 75/
Contains in a ratio of 25 to 25/75 (weight ratio),
4-methyl-Δ ³ − in the polycarboxylic anhydride
A polycarboxylic anhydride composition containing 0.1% by weight or less of tetrahydrophthalic anhydride is used as a curing accelerator using the general formula () (However, in the formula, n is an integer from 2 to 11 and m is 2
The present invention relates to a resin-sealed light emitting diode using a diaza-bicyclo-alkene compound represented by the formula (an integer of 6 to 6, and any methylene group may be substituted with an alkyl group or an allyl group). In the present invention, the light emitting diode sealed with the epoxy resin composition is, for example, a GaAsxP _1-x mixed crystal having a p-n junction (where 1≧x≧
There are light emitting elements, numeric display elements, etc. that have a surface that contributes to light emission consisting of 0). At least the surface of such a light emitting diode that contributes to light emission is covered with a cured product of an epoxy resin composition. The epoxy resin composition used in the present invention contains an epoxy resin, a polycarboxylic anhydride, and a curing accelerator. Here, as the epoxy resin, a colorless or light-colored transparent liquid or solid epoxy resin is preferable. Typically used epoxy resins include bisphenol type epoxy resins obtained from divalent phenols such as bisphenol A and bisphenol F and epichlorohydrin, cycloaliphatic type epoxy resins, hexahydrophthalic acid,
These include glycidyl ester type epoxy resins of polybasic acids such as tetrahydrophthalic acid, novolac type epoxy resins, and diglycidyl ether type epoxy resins of long chain polyols. Examples of commercially available products include the product name manufactured by Shell Chemical Company. Araldite CY-183, CY-182, CY-175, GY-
250, GY-260, GY-252, DOW Chemical product name DEN-431, DEN-438, DER-732,
These include DER-330, DER-331, DER-332, and Chitsonox 221 and 289 manufactured by Chitso Corporation. The above-mentioned polycarboxylic acid anhydride containing methylhexahydrophthalic anhydride as its main component is extremely insensitive to moisture in the atmosphere, and especially when blended with epoxy resin, crystals do not precipitate even after absorbing moisture for a long time. It is preferable not only for workability but also for the properties of the cured product. For this purpose, the polycarboxylic anhydride contains 4
-Methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride and 4-methyl-Δ ³
-tetrahydrophthalic anhydride in the above proportions. The structural formulas of 4-methylhexahydrophthalic anhydride (), 3-methyltetrahydrophthalic anhydride () and 4-methyl-Δ ³ -tetrahydrophthalic anhydride () are as follows. The polycarboxylic anhydride of the present invention contains therein:
4-Methyl-Δ ³ -tetrahydrophthalic anhydride
It contains no more than 0.1% by weight, preferably no more than 0.06% by weight, thereby dramatically extending the time until crystal precipitation upon moisture absorption. Considering 4-methyl-Δ ³ -tetrahydrophthalic anhydride () as an impurity, it is natural that hygroscopicity can be improved by removing this impurity as much as possible. Even if the acid contains relatively large amounts of 4-methyl-Δ ⁴ -tetrahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, endomethylene-hexahydrophthalic anhydride, etc. (for example, 20% by weight or less). It is surprising that only 4-methyl-Δ ³ -tetrahydrophthalic anhydride () has an adverse effect, since it does not have an adverse effect on hygroscopicity. Furthermore, even if the content of 4-methyl-Δ ³ -tetrahydrophthalic anhydride () is, for example, 0.1% by weight or less, 4-methylhexahydrophthalic anhydride () and 3-methylhexahydrophthalic anhydride () are If the mixing ratio is outside the range of 75/25 to 25/75 (weight ratio), free carboxylic acid crystals will precipitate in a short time upon moisture absorption. When the above-mentioned polycarboxylic acid anhydride, which is a curing agent component in the epoxy resin composition, is used to seal a light emitting diode, the cured product after sealing will not change color during curing. First, it has excellent transparency, does not change color even if left in a high-temperature atmosphere for a long time, has a very small decrease in transparency, and does not impair the light-emitting characteristics of the light-emitting diode. The amount of the above polycarboxylic acid anhydride used is
Preferably, the amount is in the range of 0.5 to 1.5 equivalents in terms of carboxyl group per equivalent of epoxy group in the epoxy resin. If it is too small, it will be difficult to cure sufficiently, and if it is too large, the mechanical properties of the cured product will tend to deteriorate.
Particularly preferably, 0.85 to 1.2 equivalents are used. As the diaza-bicyclo-alkene compound used as the curing accelerator, compounds represented by the above general formula () are used, and among them, 1.8 diaza-bicyclo(5.4.0) undecene-7 is particularly preferred. The salt of the diaza-bicyclo-alkene compound is obtained by reacting the diaza-bicyclo-alkene compound with an acid. As acids, both organic acids and inorganic acids can be used, but in particular (i) aromatic, alicyclic or aliphatic carboxylic acids or oxycarboxylic acids, (ii) aromatic, alicyclic or aliphatic sulfonic acids. , (iii) phenols, and (iv) inorganic acids such as carbonic acid and phosphoric acid. The amount of these curing accelerators added is preferably 0.1 to 5% by weight based on the total amount of epoxy resin and polycarboxylic acid anhydride.
If the amount is too small, the epoxy resin composition will be difficult to cure, and if the amount is too large, the improvement in the curing accelerating effect proportional to the amount used will decrease, and in some cases, the mechanical properties will tend to deteriorate. Particularly preferably 0.3 to 3% by weight
used. A light emitting diode sealed with a resin can be manufactured by curing the epoxy resin composition while at least the surface of the unsealed light emitting diode that contributes to light emission is immersed in the epoxy resin composition in the sealed mold. can. Good results can be obtained when curing epoxy resin compositions under commonly used curing conditions.
Preferably temperatures of 80°C to 150°C and curing times of several minutes to 1 day are used. Another feature of the present invention is that it is difficult to be colored even when cured for a short time of several minutes to more than ten minutes at 120°C to 150°C. The cured product of the epoxy resin composition that constitutes a part of the light emitting diode sealed with the resin obtained in this way is colorless or light-colored and transparent, and can be heated at 120°C.
Even if it is left for 1000 hours, it can maintain its colorless or light color and transparent properties, which are almost the same as the initial state. Note that known diluents, fillers, extenders, dyes, plasticizers, antifoaming agents, thixotropic agents, and the like may be added to the epoxy resin composition as necessary. Next, examples of the present invention will be shown. Hereinafter, "parts" and "%" are based on weight. Example 1 Consists of 70% of 4-methylhexahydrophthalic anhydride and 30% of 3-methylhexahydrophthalic anhydride, and also contains 0.1% or less of 4-methyl-Δ ³ -tetrahydrophthalic anhydride based on the total amount. 100 g of polycarboxylic anhydride and 1 g of 1.8 diaza-bicyclo(5.4.0) undecene-7 (DBU) were heated at 120°C.
A uniform curing agent solution was prepared by heating and stirring, and mixed with 100 g of Araldite GY-250 (Ciba Geigy Co., Ltd. trade name: Epi-bis type epoxy resin, epoxy equivalent: 190) to obtain a uniform resin solution.
An unsealed light-emitting diode was placed in a mold, the resin solution was poured into the mold, and the mold was heated at 120° C. for 16 hours. Next, the resin-sealed light emitting diode was taken out of the mold. FIG. 1 shows a front view of the resulting resin-sealed light emitting diode. A lead wire 4 is connected between the conductor 1 and a portion (mixed crystal consisting of a p-n junction) 3 that contributes to the light emission of the light emitting diode provided at the tip of the conductor 2, and these are connected using an epoxy resin composition. It is covered with a cured material 5. Note that this cured product is colorless and transparent. A DC voltage was applied between conductors 1 and 2 to measure the brightness. Moreover, after leaving this light emitting diode under the condition of 120℃ for 1000 hours,
The brightness was measured. The results are shown in Table 1. Comparative Example 1 The procedure of Example 1 was followed except that benzyldimethylamine (BDMA) was used instead of DBU. The measurement results are shown in Table 1.

[Table] Invert Examples 2 to 3 and Comparative Examples 2 to 4 Evaluations were made in the same manner as in Example 1 except that the epoxy resin compositions having the formulations shown in Table 2 were used. The results are shown in Table 2.

[Table] 2) and 3) are the same as Table 1.
The cured parts of the light-emitting diodes sealed with the resins obtained in Examples 1 to 3 did not change color during curing or after being left in a high-temperature atmosphere, and remained colorless and transparent. In the resin-sealed light emitting diode according to the present invention, the surface that contributes to light emission is covered with a cured product of a specific epoxy resin composition, and the cured product has excellent transparency and can be kept in a high-temperature atmosphere for a long time. Even if time is radiated,
Since excellent transparency is maintained, the characteristics of the light emitting diode are not deteriorated.

[Brief explanation of the drawing]

FIG. 1 shows a front view of a light emitting diode sealed with resin obtained in an example and a comparative example. Explanation of symbols, 1...Conductor, 2...Conductor, 3
... Part that contributes to light emission, 4 ... Lead wire,
5...Cured product of epoxy resin composition.

Claims (1)

[Scope of Claims] 1. A light emitting diode in which at least a surface contributing to light emission is covered with a cured product of an epoxy resin composition containing an epoxy resin, a polycarboxylic acid anhydride, and a curing accelerator, comprising: The composition contains methylhexahydrophthalic anhydride as the main component as a polycarboxylic anhydride, and its isomers 4-methylhexahydrophthalic anhydride () and 3-methylhexahydrophthalic anhydride () () /() in a ratio of 75/25 to 25/75 (weight ratio), and 4-methyl-Δ ³ -tetrahydrophthalic anhydride is 0.1% by weight or less in the polycarboxylic anhydride. Using a composition of carboxylic acid anhydride, the general formula () is used as a curing accelerator. (However, in the formula, n is an integer from 2 to 11 and m is 2
A light emitting diode sealed with a resin using a diaza-bicyclo-alkene compound represented by: