JPH0219845B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an epoxy resin composition with good transparency for sealing light-emitting elements, light-receiving elements, and the like. [Technical background of the invention and its problems] In recent years, light-emitting devices such as light-emitting diodes, which have been put into practical use for various displays, have been manufactured by resin sealing. The light emitting device is molded using liquid epoxy resin or the like as the sealing resin. However, it is very difficult to cure and obtain a transparent epoxy resin composition, and currently carboxylic acid anhydrides are generally used for curing epoxy resins. However, although the cured product obtained from carboxylic acid anhydride and epoxy resin has less coloration than amine curing, etc., the curing temperature is 130-140°C.
If the temperature exceeds .degree. C., coloration becomes significant, so the curing temperature must be kept low and curing requires a long time of 3 hours or more. Furthermore, when curing an epoxy resin with an acid anhydride curing agent, a curing accelerator is often added to accelerate curing. However, addition of these curing accelerators often causes significant discoloration. Furthermore, even cured epoxy resins obtained from carboxylic acid anhydrides and the like with relatively little coloration have the disadvantage that coloration progresses over time, and particularly in high-temperature atmospheres of 100° C. or higher, coloration progresses significantly. From these points, resin-sealed light emitting devices have had many problems in terms of coloring of the sealing resin. [Object of the invention] The present invention has been made in view of the above circumstances, and
The object of the present invention is to provide an epoxy resin composition that can yield a transparent cured product in a short time and maintain transparency for a long time in a relatively high-temperature atmosphere. [Summary of the Invention] As a result of intensive studies to achieve the above object, an epoxy resin composition that is a transparent cured product and exhibits significantly less coloration at high temperatures has been created by adding thiophosphites to the epoxy resin system. This is what we found out that it can be obtained. That is, the present invention is an epoxy resin composition for sealing with good transparency, characterized in that a thiophosphite is blended as a coloring inhibitor into an epoxy resin containing an anhydride curing agent. Epoxy resins used in the present invention include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, water Examples thereof include bisphenol A type epoxy resins, aliphatic epoxy resins, epoxy resins obtained by reacting aromatic, aliphatic or alicyclic carboxylic acids with epichlorohydrin, and spiro ring-containing epoxy resins. Examples of commercially available products include Epicote 807, 827, 828, 834 manufactured by Ciel Chemical Co., Ltd.
1001, 1004, Ciba Geigy's product name Araldide CY-175, CY-182, CY-183, Dow Chemical's product name DEN431, DEN438, DER332, Daicel Chemical's product name Celoxide 2021, Asahi Denka's product name There are products such as Adekal Resin EP4080. These epoxy resins may be used alone or in combination of two or more. Examples of carboxylic acid anhydrides as curing agents used in the present invention include phthalic anhydride, tetrahydrophthalic anhydride, 3.6 endomethylenetetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and succinic anhydride. , adipic anhydride, maleic anhydride, pyromellitic dianhydride, etc. It is desirable to use these cured products that have been sufficiently purified and have little coloring, and the proportion of these cured products blended into the epoxy resin is in the range of 0.5 to 1.8 equivalents per 1 equivalent of epoxy resin. These acid anhydrides can be used alone or in combination of two or more. As the curing accelerator used in the present invention, tertiary
Examples include class amines, imidazoles, carboxylic acid metal salts, quaternary ammonium salts, quaternary phosphates, diaza-bicyclo-alkenes and their salts. The amount of these curing accelerators added is 0.05 to 7.0% by weight based on the total amount of the epoxy resin or the epoxy resin and the carboxylic acid anhydride curing agent. The thiophosphites used as coloring inhibitors in the present invention include trimethyl trithiophosphite, triethyl trithiophosphite, tri-n-propyl trithiophosphite, trilauryl trithiophosphite, and tricyclohexyl trithiophosphite. These include osphite, triphenyl trithiophosphite, etc. The thiophosphite is usually used in an amount of 0.05% to 8% by weight based on the total amount of the epoxy resin, curing agent and curing accelerator. This is because if it is less than 0.05% by weight, the coloring prevention effect is insufficient, and if it exceeds 8% by weight, it will be inferior in water resistance, water absorption, and heat distortion temperature. Therefore, it is limited within the above range. As described above, the epoxy resin composition of the present invention with good transparency contains an epoxy resin, a curing agent, a curing accelerator, and thiophosphites, but may also contain various additives such as a light scattering agent and dye if necessary. can be blended. [Effects of the Invention] The epoxy resin composition of the present invention thus obtained exhibits excellent transparency, particularly excellent discoloration resistance during and after molding, and resists discoloration and decrease in light transmittance. It is extremely useful for resin-sealed light-emitting/light-receiving devices. [Embodiments of the Invention] Examples of the present invention will be described below. Example 1 100 g of Epon 828 (epoxy resin trade name manufactured by Ciel Chemical Co., Ltd.), 100 g of hexahydrophthalic anhydride,
2.0 g of UCAT SA102 (2-ethylhexane salt of 1.8-diazabicyclo(5,4,0) undecene 7 manufactured by Sunabott Co., Ltd.) and 2.0 g of trilauryl trithiophosphite were mixed and stirred to form a resin composition. Thickness 2.0mm, width 20mm, length
Inject into a mold to obtain a 50 mm molded product, 150
℃ for 30 minutes. Next, the cured molded product was removed from the mold and visually evaluated for anhydrity. After curing the above resin composition at 120°C for 3 hours, the light transmittance of the molded material to visible light was measured using a self-recording spectrophotometer (UVDIC-510 model manufactured by JASCO Corporation).
Measurements were carried out using Add this molded product to 150
After being left in an air atmosphere at ℃ for 200 hours, the light transmittance was measured in the same manner as above. These results are shown in the lower part of Table 1. Numbers are light transmittance at 550nm. Examples 2 to 7 Moldings were prepared using the compositions shown in Table 1 in the same manner as in Example 1, and the same coloring evaluations were performed. The coloring evaluation criteria are shown below. A is colorless and transparent, B is slightly colored, C is transparent but slightly colored, D is colored, and E is significantly colored. Comparative Examples 1 to 6 Moldings were made using the compositions shown in Table 1 in the same manner as in Example 1, and the same coloring evaluations were performed. The results are shown in the lower part of Table 1. FIG. 1 shows some examples and comparative examples of light transmittance curves from 400 nm to 700 nm.

[Table] As is clear from Table 1, the resin composition of the present invention to which thiophosphites are added has excellent transparency after curing at 150°C and light transmittance after 200 hours at 150°C. In the comparative example, the temperature was raised to 150℃ with the addition of a general antioxidant.
While the light transmittance at 550 nm after 200 hours was about 30 to 60%, in the examples in which thiophospheres were added, it was 90% or more, indicating a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a graph showing the light transmittance of the epoxy resin composition of the present invention at a wavelength of 400 to 700 nm in comparison with conventionally known epoxy resin compositions.

Claims (1)

[Scope of Claims] 1. An epoxy resin composition for sealing with good transparency, characterized in that a thiophosphite is blended as a coloring inhibitor into an epoxy resin containing an acid anhydride curing agent. 2. The epoxy resin composition for sealing with good transparency according to claim 1, wherein the thiophosphite is 0.05% to 8% by weight based on the epoxy resin composition.