WO2023033468A1 - Curable silicone composition capable of having dome shape, and cured product thereof - Google Patents

Abstract

The present invention relates to a curable silicone composition and a cured product thereof. The silicone composition has thixotropicity through surface-modified fumed silica of the curable silicone composition, and thus can be discharged and cured into a dome shape and has excellent transparency and light extraction efficiency. In addition, the silicone composition contains a surfactant so as to improve fluidity, and thus a uniform dome diameter can be implemented when the silicone composition is discharged in a dome shape.

Description

Curable silicone composition capable of dome shape and cured product thereof

The present invention relates to a curable silicone composition and a cured product thereof. More specifically, it relates to a curable silicone composition for optics that has high light transmittance and can be manufactured into a constant dome shape and thus has excellent optical functions, and a cured product thereof.

An encapsulant has been used to seal the optical element, but this encapsulant is discolored due to high temperature due to an increase in luminance and power of the optical element, thereby reducing the lifespan of the entire element. In order to avoid this problem, a number of techniques for resin-sealing optical elements using silicone compositions having excellent thermal stability have been developed.

As an optical element, light emitting diode (LED) is used in various fields because of its low power consumption and long lifespan. The light emitted from the LED is highly linear, so it is necessary to adjust the direction of light, and the difference in refractive index between the silicone composition covering the LED and the air When is large, there is a problem in that total reflection occurs, the efficiency of light extraction emitted into the air decreases, and the cured silicone material is deteriorated by high-energy short-wavelength LED light or heat. Regarding this, the outer surface of the cured silicone material is made into a dome shape or the technology to control the direction of LED light by adjusting the refractive index of the cured silicone material, and the formation of a layer with an appropriate refractive index on the outside of the cured silicone material so that the difference in refractive index between the cured silicone material and air is not large. A technology for efficiently emitting light, such as a light emission, and a technology for improving heat resistance by adjusting the silicone component of a silicone composition (Registration No. 10-1614161) have been introduced.

However, the above techniques did not solve the problem of making a cured silicone product opaque due to cloudiness of the silicone composition when silica is added to the silicone composition to form a dome shape.

There was also a change in the process of manufacturing the cured silicone material in a dome shape, and conventionally, it was manufactured in a lens shape through injection molding and then fixed to the LED chip with an adhesive. However, this method requires an additional bonding process after manufacturing a cured product, and the lens is peeled off or discolored by high-energy light and heat, resulting in a decrease in light extraction efficiency, thereby deteriorating the performance of the LED.

In order to solve this problem, research on the dispensing method of dispensing a silicone composition with thixotropic properties directly onto the LED chip in a dome shape is being conducted, but it is difficult to implement a constant dome diameter, resulting in poor fairness, and It remains a problem that the transmittance of cured silicone products is lowered with the addition of silica.

Accordingly, the problem to be solved by the present invention is to provide a silicone composition and a cured product having excellent transparency and light extraction efficiency while allowing the silicone composition to have thixotropy, including surface-modified fumed silica.

In addition, to provide a silicone composition and a cured product thereof maintaining transparency and light extraction efficiency without discoloration even when exposed to high-energy short-wavelength light and heat.

Another problem to be solved in the present invention is to improve the fluidity of the silicone composition by further including a surfactant, so that the dome diameter can be uniformly implemented when dispensing in a dome shape, and the processability is improved because the bonding process is not required. and to provide a cured product thereof.

According to one aspect of the present invention for solving the above problems, (A) two or more organopolysiloxanes having two or more alkenyl groups per molecule and having different mass average molecular weights;

(B) organopolysiloxanes containing at least two silicon-bonded hydrogen atoms per molecule;

(C) fumed silica modified with a silicon compound and containing siloxane groups on the surface; and

(D) a surfactant:

The refractive index of (A) and (B) is greater than or equal to the refractive index of (C),

A curable silicone composition is provided in which the difference between the refractive indices of (A) and (B) and the refractive index of (C) is less than 0.05.

Preferably, a curable silicone composition is provided, wherein the difference in mass average molecular weight of the two or more organopolysiloxanes of (A) is 20,000 g/mol to 100,000 g/mol.

Preferably, the fumed silica of (C) is surface-modified by forming a siloxane group containing one or more R ₂ SiO _2/2 units (R is an alkyl group) on its surface,

A curable silicone composition is provided in which one or more siloxane groups including one or more R ₂ SiO _2/2 units are bonded to the surface of the fumed silica.

Preferably, the refractive index of (C) is 1.43 to 1.47, a curable silicone composition is provided.

Preferably, a curable silicone composition is provided wherein the refractive index of (A) and (B) is greater than or equal to 1.43 and less than 1.5.

Preferably, a curable silicone composition is provided wherein the silicon compound of (C) is at least one selected from the group consisting of Octamethylcyclotetrasiloxane and Dichlorodimethylsilane.

Preferably, (A) is 45 to 60 parts by weight in total,

(B) is 35 to 45 parts by weight,

(C) is 4 to 15 parts by weight and

The (D) is provided with a curable silicone composition comprising 0.03 to 0.07 parts by weight.

Preferably, (D) is provided with a curable silicone composition in which at least one selected from the group consisting of cyclosiloxane and dimethicone.

Preferably, a curable silicone composition further comprising at least one selected from the group consisting of a hydrosilylation catalyst, a curing retarder, and an adhesion promoter is provided.

Preferably, a curable silicone composition having a thixotropy of 3.5 to 4.5 is provided.

Preferably, a cured product prepared by curing the curable silicone composition is provided.

Preferably, the transmittance of single wavelength light is 90% or more, and a cured product characterized in that it is colorless and transparent is provided.

Preferably, after applying heat at 150° C. to 250° C. for 250 hours to 350 hours, a cured product having a single wavelength light transmittance of 90% or more is provided.

Preferably, as a cured product prepared by curing the curable silicone composition into a dome shape,

A cured product characterized in that the uniformity (±0.1 mm range) of the dome diameter is 95% or more is provided.

The silicone composition and its cured product according to the present invention can be discharged and cured in a dome shape by including surface-modified fumed silica to have thixotropy.

In addition, transparency and light extraction efficiency of the silicone composition and its cured product including surface-modified fumed silica are excellent, and transparency and light extraction efficiency are maintained without discoloration even when exposed to short-wavelength light and heat having high energy.

In addition, by improving the fluidity of the silicone composition by including a surfactant, even if the silicone composition is discharged in a dome shape by a dispensing method, the dome diameter can be made uniform and the bonding process is not required, so the processability is improved.

1 shows a reaction scheme for modifying the surface of fumed silica using dichlorodimethylsilane as a specific example of surface-modified fumed silica.

2 shows a reaction formula for modifying the surface of fumed silica using octamethylcyclotetrasiloxane as a specific example of surface-modified fumed silica.

Hereinafter, the present invention will be described.

All terms (including technical and scientific terms) used in this specification, unless otherwise defined, may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined.

In addition, throughout this specification, when a certain component is said to "include", it means that it may further include other components, not excluding other components, unless otherwise stated.

<Curable silicone composition>

As an embodiment of the present invention, the curable silicone composition includes: (A) two or more organopolysiloxanes having two or more alkenyl groups per molecule and having different mass average molecular weights; (B) two or more silicon bonds per molecule; Organopolysiloxane containing a hydrogen atom, (C) fumed silica modified with a silicon compound and containing a siloxane group on the surface, and (D) a surfactant, wherein the refractive index of (A) and (B) is The refractive index of (C) is greater than or equal to, and the difference between the refractive index of (A) and (B) and the refractive index of (C) is less than 0.05, respectively.

Component (A) is one of the main components of the present invention and has an essentially linear molecular structure, but may be partially branched. The alkenyl group of component (A) may include vinyl, allyl, isopropenyl, butenyl, hexenyl and cycloalkenyl groups and the like, and is preferably a vinyl group. The binding positions of the two or more alkenyl groups in one molecule of organopolysiloxane are preferably both terminals, and include, but are not limited to, binding to both terminals and side chains.

Component (A) may comprise R ₃ SiO _1/2 units and R ₂ SiO _2/2 units, or may further comprise RSiO _3/2 units. Wherein R is a monovalent hydrocarbon group, independently an alkyl group such as methyl, ethyl or propyl, an alkenyl group such as vinyl, allyl, isopropenyl, butenyl, hexenyl and cycloalkenyl group, phenyl, xylyl, etc. It may be an aryl group, an aralkyl group such as benzyl, or a halogenated alkyl group, preferably a vinyl group at both ends and side chain ends.

Component (A) is composed of two or more organopolysiloxanes having different standard polystyrene-reduced mass average molecular weights measured by gel permeation chromatography, and in order to appropriately adjust the hardness, strength, etc. required after the composition is cured, the component ( A) can be configured. The average molecular weight difference between the organopolysiloxanes of component (A) is 20,000 g/mol or more, preferably 30,000 g/mol to 100,000 g/mol, more preferably 50,000 g/mol to 80,000 g/mol.

The two or more organopolysiloxanes of component (A) are not particularly limited, but may preferably have an average molecular weight of 100 g/mol to 160,000 g/mol, and the mass ratio between these components is, for example, when two organopolysiloxanes are included. In, the mass ratio of high molecular weight siloxane:low molecular weight siloxane may be 2 to 6:1, preferably 3.5 to 5.5:1.

The refractive index of (A) is greater than or equal to the refractive index of (C), and the difference between the refractive index of (A) and the refractive index of (C) is less than 0.05. When the difference between the refractive index of any one or more of (A) and the refractive index of (C) is 0.05 or more, the transparency of the mixed silicone composition may decrease. Specifically, when the refractive index of (C) is 1.43 to 1.47, the refractive index of (A) is 1.43 or more and less than 1.52, preferably 1.45 or more and less than 1.5, more preferably about 1.45 to 1.49.

The component (B) may serve as a cross-linking agent and may have a linear, branched or cyclic molecular structure. The above (B) includes two or more silicon-bonded hydrogens per molecule, and there are no restrictions on their positions, but they may be located on both ends and side chains. In addition to the silicon-bonded hydrogen described above, as a group capable of being bonded to silicon, it is a monovalent hydrocarbon group, independently an alkyl group such as methyl, ethyl or propyl, an aryl group such as phenyl, xylyl, an aralkyl group such as benzyl, Halogenated alkyl groups can be exemplified.

Component (B) may comprise R ₃ SiO _1/2 units, R ₂ SiO _2/2 units and RSiO _3/2 units, preferably R ₃ SiO _1/2 units and RSiO _3/2 units. may consist of R is a monovalent hydrocarbon group and may independently be an alkyl group such as methyl, ethyl or propyl, an aryl group such as phenyl or xylyl, an aralkyl group such as benzyl, or a halogenated alkyl group, preferably methyl and phenyl groups am. Specifically, polyphenyl-(dimethylsiloxy)siloxane hydride terminated with terminal hydrogenation may be used.

The refractive index of (B) is greater than or equal to the refractive index of (C), and the difference between the refractive index of (B) and the refractive index of (C) is less than 0.05. If the difference between the refractive index of (B) and the refractive index of (C) is 0.05 or more, the transparency of the mixed silicone composition may decrease. Specifically, when the refractive index of (C) is 1.43 to 1.47, the refractive index of (B) is 1.43 or more and less than 1.52, preferably 1.45 or more and less than 1.5, and more preferably about 1.45 to 1.49.

The component (C) imparts thixotropy to the silicone composition so that a dome-shaped cured product can be formed. The thixotropy of the curable silicone composition may be 3.5 to 4.5, preferably 3.5 to 4.

The surface-modified fumed silica of (C) is surface-modified by forming a siloxane group containing one or more R ₂ SiO _2/2 units (R is an alkyl group) on its surface, and the one or more R ₂ SiO _2/ It is characterized in that at least one siloxane group containing ₂ units is bonded to the surface of the fumed silica.

Specifically, the silicon compound that can be used to surface-modify the fumed silica of (C) may be at least one selected from the group consisting of Octamethylcyclotetrasiloxane and Dichlorodimethylsilane. The silicon part of the silicon compound is bonded to the oxygen of the hydrophilic silanol group on the surface of the fumed silica, and the siloxane group surrounds the surface of the fumed silica to modify it to have hydrophobicity. It is believed that the dispersibility and transparency of the silicone composition are improved. Specific examples of the surface-modified fumed silica of (C) are shown in FIGS. 1 and 2.

Specifically, the refractive index of (C) may be 1.43 to 1.47, preferably 1.44 to 1.46, and more preferably about 1.45.

The component (D) is a surfactant, and can improve the ejectability of the silicone composition in the dispensing process by increasing the fluidity of the silicone composition, and as a certain amount of the silicone composition is ejected, a dome-shaped dome diameter is uniformly realized can be made

(D) may be at least one selected from the group consisting of cyclosiloxane and dimethicone. Specifically, the cyclosiloxane includes cyclotetrasiloxane, cyclopentansiloxane, cyclohexasiloxane, and the like, and cyclotetrasiloxane is preferably used.

The curable silicone composition includes 45 to 60 parts by weight of (A), 35 to 45 parts by weight of (B), 4 to 15 parts by weight of (C), and 0.03 to 0.07 parts by weight of (D). can do.

Other additives

The curable silicone composition may further include at least one selected from the group consisting of a hydrosilylation catalyst, a curing retardant, and an adhesion promoter.

The hydrosilylation catalyst is for accelerating the curing of the silicone composition. The catalyst includes a platinum-based catalyst, a rhodium-based catalyst, or a palladium-based catalyst, and a platinum-based catalyst is preferable. For example, ethenyl-[ethenyl(dimethyl)silyl]oxy-dimethylsilane, platinum may be used.

The curing retardant is for suppressing curing of the silicone composition at room temperature. Specifically, there is 3,5-Dimethyl-1-hexyn-3-ol or 1-Ethynyl-1-cyclohexanol.

The adhesion promoter is to improve the adhesion of the silicone composition to the optical element, and one or more adhesion promoters may be used. Specifically, Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated reaction products with trimethoxy[3-oxiranylmethoxy)propyl]silane and 3-glycidyloxy propyltrimethoxysilane can be mixed and used.

<cured product of silicone composition>

As another embodiment of the present invention, the cured product of the silicone composition includes one prepared by curing the curable silicone composition, and the curing may use a hydrosilation reaction between two or more organopolysiloxanes of the component (A).

The cured product of the silicone composition may have a single wavelength light transmittance of 90% or more and be colorless and transparent, and the light transmittance is preferably 95% or more.

In addition, the cured product of the silicone composition may be characterized in that transmittance of single wavelength light is maintained at 90% or more even after heating at 150 ° C to 250 ° C for 250 to 350 hours.

Components used to prepare the silicone compositions of Examples and Comparative Examples are listed in Table 1 below. Hereinafter, the following components are indicated by A to G.

C-1 is the same as shown in Figure 1, C-2 is the same as shown in Figure 2, and C-3 is to modify the surface of the fumed silica with hexamethydisilazane so that the surface of the fumed silica is surrounded by trimethylsilyl groups. , which is hydrophobic. The refractive indices of C-1 to C-3 are all about 1.45.

<Example 1> Curable silicone composition and cured product thereof

1. Preparation of silicone composition

1) 42.6 parts by weight of A-1, 10 parts by weight of A-2 and 6 parts by weight of C-1 were mixed in a planetary mixer under vacuum conditions for 3 hours.

2) Add 40 parts by weight, 0.05 parts by weight, 0.4 parts by weight, and 1 part by weight of B, D and other additives (F, G) to the mixture at room temperature, respectively, and mix for 3 hours in a planetary mixer under vacuum conditions do.

3) 10 ppm of E was added and stirred for 10 minutes under vacuum using a revolution mixer, followed by defoaming to obtain a final composition.

2. Dispensing a dome-shaped silicone composition and preparing a cured product (dispensing method)

1) One dome was formed by discharging 5 dots of the prepared silicone composition in a liquid state. A MYD10X fully automatic in-line jet dispensing system (MYCRONIC) was used.

2) After discharging, thermal curing was performed to prepare a cured product of the silicone composition.

<Example 2>

Same as Example 1, except that C-2 was used instead of C-1 as the surface-modified fumed silica.

<Comparative Example 1>

Same as Example 1, but 42.6 parts by weight of A-3 was used instead of A-1, and component D was not included.

<Comparative Example 2>

Same as Example 1, but 42.6 parts by weight of A-3 was used instead of A-1, component D was not included, and C-3 was used instead of C-1.

The above components and each weight ratio are summarized in Table 2 below.

<Experimental Example 1> Evaluation of viscosity and thixotropy of silicone composition

The viscosity and thixotropy of the silicone compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were measured at 25° C. using a Rheometer MCR-702 (Anton-paar Co.). The viscosity value was a value at 10s ^-1 , and the thixotropy was calculated as viscosity (1s ^-1 )/viscosity (10s ^-1 ). Each was discharged in a dome shape and the dome diameter of the heat-cured product was measured. The results are shown in Table 3.

Examples 1 and 2 and Comparative Example 1 had similar viscosity and thixotropic values, but Comparative Example 2 had slightly lower viscosity and thixotropic values.

After curing of Examples 1 and 2 and Comparative Example 1, the dome diameter was formed to be about 2.5 mm, but the dome diameter of Comparative Example 2 having low viscosity and thixotropy was about 2.8 mm. Since each silicone composition is ejected at 5 dots and each amount is similar, it means that the larger the diameter of the dome, the smaller the curvature of the formed dome. Therefore, in order to prepare a dome-shaped cured product having an appropriate curvature, it was confirmed that fumed silica surface-modified with C-1 or C-2 is preferable, as in Examples 1 and 2 and Comparative Example 1.

<Experimental Example 2> Evaluation of transparency and light transmittance of cured silicone material

The silicone compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were put between slide glasses and cured at 190° C. for 5 minutes to prepare specimens having a thickness of 1 mm. The specimen was visually observed to confirm the appearance color (transparency), and the light transmittance at a wavelength of 450 nm was measured using a spectrophotometer (x-rite, Color i5). The results are shown in Table 4.

Examples 1 and 2 were colorless and transparent to the naked eye, but Comparative Examples 1 and 2 were somewhat opaque and it was confirmed that the transparency was poor. In addition, even when looking at the measured light transmittance, Examples 1 and 2 had a high light transmittance of 95% or more, and Comparative Examples 1 and 2 had a low light transmittance of less than 90%.

Since the refractive index of C-1 to C-3 is about 1.45, the refractive index of components corresponding to (A) and (B) is preferably about 1.45 or more and less than 1.50. The refractive index of A-3 used in Comparative Examples 1 and 2 is 1.52, which is different from the refractive index of C-1 and C-3 by more than 0.05, so it seems that the light transmittance of the cured product of the silicone composition was measured very low. Example 1 And the refractive indices of A-1, A-2 and B used in 2 all belonged to the range of 1.45 or more and less than 1.5, so it was confirmed that the cured product had excellent light transmittance.

<Experimental Example 3> Evaluation of heat resistance of cured silicone products

After each specimen prepared in Experimental Example 2 was left at about 200 ° C. for about 300 hours, the light transmittance at a wavelength of 450 nm was measured using a spectrophotometer (x-rite, Color i5). The results are shown in Table 5.

Although discoloration due to heat was not confirmed in all of Examples 1 and 2 and Comparative Examples 1 and 2, the light transmittance of Examples 1 and 2 was still excellent at 90% or more, whereas the light transmittance of Comparative Examples 1 and 2 was 80%. was greatly reduced to less than

In addition, the decrease rate of light transmittance of Examples 1 and 2 was only about 5%, whereas the decrease rate of light transmittance of Comparative Examples 1 and 2 was about 8 to 9.5%, and heat generated in the optical element when used in the element. It is judged that the life of the optical element to which the cured silicone products of Examples 1 and 2 are applied will be maintained longer even if continuously exposed to the like.

<Experimental Example 4> Evaluation of dome diameter uniformity of cured silicone material

The silicone compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were dispensed in a dome shape to prepare 100 pieces each, and the dome diameter was measured to determine the uniformity of the dome diameter. The diameter of the dome is uniformly formed only when the mass of 1 dot of the discharged silicone composition is constant. The results are shown in Table 6.

In Examples 1 and 2, fumed silica (C-1 or C-2) and surfactant (D) were added, and all 100 domes were measured to have a diameter in the range of ± 0.1 mm, and the uniformity of the dome diameter was quite excellent However, in Comparative Examples 1 and 2 in which surfactant (D) was not added, 1 to 10 domes with a dome diameter exceeding the range of ±0.1 mm were found, and the dome diameter uniformity was normal.

Comparative Example 1, to which no surfactant was added, showed a similar level of viscosity and thixotropy to Examples 1 and 2 (Experimental Example 1), but the uniformity of the dome diameter was similar to that of Examples 1 and 2 because surfactant was not added. It was confirmed that there was a drop in comparison. Therefore, in order to satisfy both the implementation of a suitable dome shape according to imparting thixotropic properties and the uniformity of the dome diameter, it is determined that it is preferable to properly mix and use the surface-modified fumed silica and the surfactant.

As described above, the silicone composition and the cured product thereof according to the present invention can be discharged and cured in a dome shape by including surface-modified fumed silica to have thixotropy.

In addition, transparency and light extraction efficiency of the silicone composition and its cured product including surface-modified fumed silica are excellent, and transparency and light extraction efficiency are maintained without discoloration even when exposed to short-wavelength light and heat having high energy.

In addition, by improving the fluidity of the silicone composition by including a surfactant, even if the silicone composition is discharged in a dome shape by a dispensing method, the dome diameter can be made uniform and the bonding process is not required, so the processability is improved.

It is obvious to those skilled in the art that the present invention is not limited to the above embodiments and can be variously modified or modified without departing from the technical gist of the present invention. it did

Claims (14)

(A) two or more organopolysiloxanes having two or more alkenyl groups per molecule and having different mass average molecular weights; (B) organopolysiloxanes containing at least two silicon-bonded hydrogen atoms per molecule; (C) fumed silica modified with a silicon compound and containing siloxane groups on the surface; and (D) a surfactant: The refractive index of (A) and (B) is greater than or equal to the refractive index of (C), The difference between the refractive index of (A) and (B) and the refractive index of (C) is less than 0.05, curable silicone composition. The method of claim 1, The curable silicone composition, characterized in that the difference in mass average molecular weight of the two or more organopolysiloxanes of (A) is 20,000 g / mol to 100,000 g / mol. The method of claim 1, The fumed silica of (C) is surface-modified by forming a siloxane group containing one or more R ₂ SiO _2/2 units (R is an alkyl group) on its surface, The siloxane group containing one or more R ₂ SiO _2/2 units is one or more bonded to the surface of the fumed silica, curable silicone composition. The method of claim 1, The refractive index of (C) is 1.43 to 1.47, curable silicone composition. The method of claim 1, The refractive index of (A) and (B) is 1.43 or more and less than 1.5, curable silicone composition. The method of claim 1, The silicon compound of (C) is at least one selected from the group consisting of octamethylcyclotetrasiloxane and dichlorodimethylsilane. The method of claim 1, The (A) is a total of 45 to 60 parts by weight, (B) is 35 to 45 parts by weight, (C) is 4 to 15 parts by weight and The (D) is a curable silicone composition comprising 0.03 to 0.07 parts by weight. The method of claim 1, (D) is at least one curable silicone composition selected from the group consisting of cyclosiloxane and dimethicone. The method of claim 1, A curable silicone composition further comprising at least one selected from the group consisting of a hydrosilylation catalyst, a curing retarder, and an adhesion promoter. The method of claim 1, A curable silicone composition having a thixotropy of 3.5 to 4.5. A cured product produced by curing the curable silicone composition according to claim 1. The method of claim 11, A cured product characterized in that the transmittance of single wavelength light is 90% or more and is colorless and transparent. The method of claim 11, After applying heat at 150 ° C to 250 ° C for 250 to 350 hours, the cured product has a transmittance of 90% or more of single wavelength light. A cured product produced by curing the curable silicone composition according to claim 1 into a dome shape, A cured product, characterized in that the uniformity of the dome diameter (range of ± 0.1 mm) is 95% or more.

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