JP2020158692A - Fluorine-containing condensed type organopolysiloxane prepolymer and cured product thereof - Google Patents

Abstract

To provide a fluorine-containing condensed type organopolysiloxane prepolymer which is excellent in transparency and light resistance in a UV range and can be used as a sealing layer or an adhesive layer, and to provide a cured product thereof.SOLUTION: A fluorine-containing condensed type organopolysiloxane prepolymer is prepared by subjecting the following (A), (B) and (C) to condensation reaction: (A) a polydimethylsiloxane having silanol groups at both ends and having a molecular weight distribution index (Mw/Mn; Mw is a weight average molecular weight, and Mn is a number average molecular weight) of 1.3 or more; (B) oligomers of tetraalkoxysilanes and/or a complete or a partial hydrolyzate or condensates of the oligomers; and (C) a silane compound having 3 methoxy groups and 1 of a linear (n-) perfluoroalkyl group having 4 or more carbon atoms or a branched perfluoroalkyl group having 5 or more carbon atoms, and/or a complete or partial hydrolyzate or condensate of the silane compound.SELECTED DRAWING: None

Description

The present invention generally relates to a fluorine-containing condensation type organopolysiloxane prepolymer and a cured product thereof, and specifically, for sealing or sealing in an optical system component that emits high-energy light at a short wavelength such as UV-LED. It relates to a polydimethylsiloxane polymer containing fluorine and cured by thermal condensation, which is used in a place where emitted light is transmitted or irradiated for the purpose of adhesion.

For the light emitting diode (LED), which is an optical member, an elastic material such as an adhesive for joining a sealing material for protecting parts such as a light emitting element, a wire, and a reflector, and a quartz window material is used. ing. In recent years, LEDs have been required to have shorter emission wavelengths and higher output wavelengths, and to improve the light resistance of constituent members.

However, UV (ultraviolet) -LEDs with a wavelength of 400 nm or less have high energy even if they are low-power LEDs, and even silicone resins that have been used so far and are said to have high heat resistance have material destruction and sealing surfaces. It is impossible to use it due to peeling from the silicon.

Japanese Unexamined Patent Publication No. 2003-008073 (Patent Document 1) is characterized in that it is a light emitting element in which an LED chip is sealed with a sealing resin, and the sealing resin is a fluororesin having visible light transmittance. The light emitting element to be used is described. It is recognized in the market that fluorine-based resins have light resistance to light having wavelengths in the UV range, and they have been put into practical use as a protective layer for LED chips using a thin film.

In the bonding of UV-LED elements such as quartz glass windows, metallizing treatment is known for glass sealing and bonding with gold-sulfur material.

Japanese Unexamined Patent Publication No. 2015-222767 (Patent Document 2) describes a cured condensed-type organosiloxane polymer in which an inorganic component is incorporated into a siloxane polymer. The organosiloxane polymer obtained by thermosetting a condensed organosiloxane polymer precursor prepared from a polydimethylsiloxane having both terminal silanol groups and a silane oligomer having an alkoxy group has heat resistance and light resistance as compared with conventional silicone resins and the like. It is possible to provide an elastic body characterized by low residual strain, which is excellent in property, light transmission, and stress relaxing ability. This material has already been put into practical use in Japan and overseas as a sealing material for LEDs and a lens bonding material.

There are many attempts to incorporate fluorine into an organosiloxane polymer or to combine a fluorine compound in order to improve heat resistance and light resistance. In WO 2016/052495 (Patent Document 3), a condensate of a silane compound is used. As the condensate of the silane compound, a silicone resin containing a structural unit derived from a fluorine atom-containing silane compound formed by bonding a fluoroalkyl group having at least one fluorine atom to a silicon atom is described.

Japanese Unexamined Patent Publication No. 2003-008073 Japanese Unexamined Patent Publication No. 2015-222767 Special re-publication WO2016 / 052495

In the above-mentioned members exposed to UV light and high-intensity light and members that transmit UV light and high-intensity light, they adhere to the base material by inorganic bonding with high binding energy, and can maintain high light resistance and adhered state. , There is a demand for an elastic material having an excellent stress relaxation ability that can withstand a cold cycle.

However, the fluorine-based resin used for the light emitting device described in Patent Document 1 needs to be diluted with a special solvent. In addition, there are many process problems such as molding a lens shape for the purpose of condensing light, sealing in mm units or more, and adhesive use.

On the other hand, in glass sealing and joining with gold-tin brazing material, in addition to the fact that the number of processes increases and high temperature treatment is required, there are problems with UV (ultraviolet) resistance and cold cycle resistance, it is hard. There are weaknesses due to the use of materials.

The condensed polymer siloxane polymer cured product described in Patent Document 2 does not contain a fluoroalkyl group that imparts UV resistance, and is further heat resistant, light resistant, and suitable for use as a UV-LED encapsulant. Gas barrier property is required.

Further, Patent Document 3 does not include a high molecular weight PDMS unit that contributes to the flexibility of the cured product, and there still remains a problem in extending the life of the UV-LED encapsulant.

As described above, a fluorine-based resin is known as one of the materials resistant to the UV region. However, the fluoroalkyl group having a large number of carbon atoms is large and has many restrictions on the reaction. When incorporated into a material that requires flexibility in particular, hardness increases even at a low concentration, and the liquid may become cloudy and separate.

Therefore, an object of the present invention is to provide a fluorine-containing condensed organopolysiloxane prepolymer and a cured product thereof, which are excellent in transparency and light resistance in the UV region and can be used as a sealing layer or an adhesive layer. is there.

The fluorine-containing condensation type organopolysiloxane prepolymer according to the present invention is prepared by subjecting the following (A), the following (B) and the following (C) to a condensation reaction.
(A) A polydimethylsiloxane having silanol groups at both ends and having a molecular weight distribution index (Mw / Mn; Mw is a weight average molecular weight and Mn is a number average molecular weight) of 1.3 or more.
(B) Tetraalkoxysilane oligomers and / or complete or partial hydrolysates or condensates of said oligomers.
(C) A silane compound having a linear (n-) perfluoroalkyl group having 4 or more carbon atoms or a branched perfluoroalkyl group having 5 or more carbon atoms and 3 methoxy groups, and / or the above. A complete or partial hydrolyzate or condensate of a silane compound.

In the fluorine-containing condensed organopolysiloxane prepolymer according to the present invention, (A) preferably has a number average molecular weight (Mn) of 15,000 to 70,000.

In the fluorine-containing condensed organopolysiloxane prepolymer according to the present invention, (B) is a linear tetramer to a tetramer, and preferably has a methoxy group or an ethoxy group as an alkoxy group.

In the fluorine-containing condensed organopolysiloxane prepolymer according to the present invention, it is preferable that 0.5 to 4 mol of (B) is blended with respect to 1 mol of (A).

In the fluorine-containing condensed organopolysiloxane prepolymer according to the present invention, it is preferable that 1 to 9 mol of (C) is blended with respect to 1 mol of (A).

In the fluorine-containing condensed organopolysiloxane prepolymer according to the present invention, the compound (D) having an isocyanurate ring structure, an epoxy group or a terminal epoxy group, and a terminal alkoxy group is (A), ( It is preferable that 0.1 to 5 parts by weight is blended with respect to a total of 100 parts by weight of B) and (C).

The encapsulant for the LED light emitting device according to the present invention includes any of the above fluorine-containing condensed organopolysiloxane prepolymers.

The adhesive for optical members having a wavelength of 450 nm or less according to the present invention includes any of the above fluorine-containing condensed organopolysiloxane prepolymers.

The cured product according to the present invention is a cured product of any of the above fluorine-containing condensed organopolysiloxane prepolymers.

When the thickness of the cured product according to the present invention is 10 μm, it is preferable that the transmittance at a wavelength of 265 nm is 75% or more, the transmittance at 300 nm is 80% or more, and the transmittance at 350 nm is 90% or more.

As described above, according to the present invention, a fluorine-containing condensed organopolysiloxane prepolymer and a cured product thereof, which are excellent in transparency and light resistance in the UV region and can be used as a sealing layer or an adhesive layer, are provided. can do.

The fluorine-containing condensed organopolysiloxane prepolymer according to the present invention will be described in detail below.

<Polydimethylsiloxane (A) having silanol groups at both ends>
The fluorine-containing condensation type organopolysiloxane prepolymer of the present invention uses polydimethylsiloxane (PDMS) having a silanol group having reactivity at both ends as a raw material. Various raw materials can be considered, such as those having silanol groups at both ends and the molecular chain branched, those having a plurality of silanol groups at the ends, and those having other reactive functional groups, but reacting with a fluorine-containing compound. When the fluorine was incorporated, the perfluoroalkyl group had a large steric hindrance and was sometimes difficult to synthesize. As a result, the linear one having silanol groups at both ends was most suitable for the preparation of the fluorine-containing condensed organopolysiloxane prepolymer. The chemical formula of (A) is shown in (1).

The biterminal silanol polydimethylsiloxane is preferably linear, the number average molecular weight (Mn) is preferably 15,000 to 70,000, and m in (1) is an integer satisfying the above molecular weight. It is preferable to have. Mw / Mn is 1.3 or more.

When the number average molecular weight is less than 15,000, the fluorine-containing organopolysiloxane cured product obtained by curing the synthesized fluorine-containing condensed organopolysiloxane prepolymer becomes hard, and it becomes difficult to relax the thermal stress. As a result, the UV resistance is lowered. On the other hand, when the number average molecular weight exceeds 70,000, the reaction of incorporating the fluoroalkyl group becomes very difficult. Therefore, the number average molecular weight of PDMS having a terminal silanol group, which is a raw material, is preferably 15,000 or more and 70,000 or less, more preferably 20,000 or more and 60,000 or less, and 25,000. As mentioned above, it is more preferably 55,000 or less.

The molecular weight distribution index Mw / Mn is 1.3 or more. When the polymerization of the silicone raw material is advanced, it is generally difficult to narrow the molecular weight due to the influence of the temperature distribution variation depending on the size of the reaction vessel. For general-purpose silicone, it is about 1.3 or more, and for high molecular weight, it is 1.5 or more. Those having a molecular weight distribution index Mw / Mn of 1.1 or less due to living polymerization or the like are also commercially available, but in the present invention, UV resistance cannot be obtained with PDMS having such a narrow molecular weight distribution.

If Mw / Mn is small, the transparency and homogeneity with respect to light will be good, and the curing reaction will be completed quickly, but the polymer having a narrow molecular weight distribution will have low toughness. From the viewpoint of resistance in the UV region, 1.5 or more is preferable. On the contrary, when Mw / Mn is large, the transparency is remarkably deteriorated. Therefore, Mw / Mn is preferably 3.0 or less, more preferably 2.5 or less.

<Oligomer of tetraalkoxysilane and / or complete or partial hydrolyzate or condensate of this oligomer (B)>
As the silane oligomer having an alkoxy group, compounds such as methyl silicate and ethyl silicate are generally known, and they can be easily obtained. The general structural formula of the alkyl silicate, which is the oligomer, is as follows.

Here, R is a methyl group or an ethyl group, but in the case of a methyl group, the reaction proceeds rapidly, but methanol may be generated as a by-product, so it is desirable to use an ethyl group. It is preferable to use n of 4 to 10 (tetramer to 10-mer). When n exceeds 10 (10-mer), the reactivity with PDMS becomes small, and the synthesis may take a high temperature and a long time. If n is less than 4 (tetramer), polycondensation of alkyl silicate alone may proceed and cluster particles may be formed, which may lead to a decrease in light transmission. Further, from the viewpoint of reactivity due to steric hindrance, the oligomer of (B) is preferably linear.

<A silane compound having a linear (n-) perfluoroalkyl group having 4 or more carbon atoms or a branched perfluoroalkyl group having 5 or more carbon atoms and 3 methoxy groups, and / or this silane compound. Complete or partial hydrolyzate or condensate (C)>
Linear (n-) perfluoroalkyl group with 4 or more carbon atoms or branched chain-like (iso is preferable but not limited to steric hindrance) perfluoroalkyl group with 5 or more carbon atoms 1 and 3 Regarding the silane compound having a methoxy group, it is important that the hydrolyzable group is a methoxy group, and it is difficult to prepare an ethoxy group probably because the hydrolysis reaction rate is low. From the viewpoint of safety, it is desirable to use a compound having an ethoxy group rather than a methoxy group, but a system using an ethoxy group causes cloudiness and is difficult to synthesize.

From the above, the following general structural formula is preferable. From the viewpoint of reactivity due to steric hindrance, a linear one is more preferable.

In the case of an n-perfluoro group, p1 is an integer of 3 or more, and in the case of an isoperfluoro group, p2 is an integer of 2 or more. If p1 and p2 are less than 3 and 2, respectively, it is difficult to improve heat resistance and light resistance. Preferably, p1 is an integer of 3-7 and p2 is an integer of 2-6.

<Compound (D) having an isocyanurate ring structure, a terminal epoxy group or an epoxy group, and a terminal alkoxy group>
As a material used for the purpose of improving adhesiveness, a compound having an isocyanurate ring structure having an epoxy group having high adhesiveness, light resistance, and heat resistance, and having a terminal epoxy group or an epoxy group, and a terminal alkoxy group. (D) can be used in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of the compounds (A), (B) and (C). The compound (D) is generally known as a modifier for an epoxy resin, and among these, a compound (D) having an alkoxy group as a functional group is preferable. This type of compound has a high molecular flatness and is expected to have an effect of increasing adhesiveness along the bonding surface, but is 0.1 parts by weight based on the total amount of the compounds (A), (B) and (C). If it is less than, the effect of improving the adhesiveness is hard to be exhibited, and if it exceeds 5 parts by weight, the light resistance and heat resistance may be deteriorated. Considering the balance between the adhesiveness improving effect, the light resistance, and the heat resistance, 0.2 to 2 parts by weight of the compound (D) is used with respect to 100 parts by weight of the total amount of the compounds (A), (B), and (C). Is more preferable.

<Organometallic compound (E)>
For the preparation of the fluorine-containing condensation type organopolysiloxane prepolymer of the present invention, it is preferable to proceed with the synthesis using an organometallic compound as a condensation catalyst. There are no restrictions on the condensation catalyst, but a Sn-based catalyst that is the easiest to use and can keep the addition amount low is effective. In addition to Sn-based catalysts, there are organometallic compounds such as Ti-based, Al-based, Zn-based, Zr-based, and Bi-based catalysts, but the reactivity is low, the heat resistance of the cured product at the time of residue is reduced, and coloring is performed. Sn-based catalysts can be used most effectively because they cause problems such as.

As the Sn-based catalyst, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin bisacetylacetonate and the like are generally used. Depending on the synthesis conditions, the Sn-based catalyst can promote an effective condensation reaction with a small amount, and the blending amount with respect to the solid content can be suppressed to 500 ppm or less.

<Measurement of average molecular weight>
The average molecular weight of PDMS (A) was measured by a gel permeation chromatography (GPC) method, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was used as the molecular weight distribution index. Using polystyrene as a standard sample, the polystyrene-equivalent molecular weight was measured. The polystyrene-equivalent molecular weight measurement by the GPC method shall be performed under the following measurement conditions.
a) Measuring equipment: Tosoh GPC HLC-8320PC
b) Columns with Mn of 30,000 or less: TSKgel guardColum Super HZ-H, TSKgel Super HZM-H x 2 c) Columns with Mn of 30,000 or more: TSKgel guardColum Super MP (HZ) -N, TSKgel Multi Book d) Oven temperature: 40 ° C
e) Eluent: Tetrahydrofuran (THF) 1.0 mL / min
f) Standard sample: polystyrene g) Injection amount: 100 μL
h) Concentration: 0.05g / 10mL
i) Sample preparation: Dissolve by stirring at room temperature using THF to which 0.2% by mass of 2,6-di-tert-butyl-p-phenol (BHT) is added as a solvent.
j) Correction: The molecular weight is calculated by correcting the deviation of the BHT peak between the time of calibration curve measurement and the time of sample measurement.

<Preparation of fluorine-containing condensation type organopolysiloxane prepolymer (F)>
In the preparation of the fluorine-containing condensed organopolysiloxane prepolymer of the present invention, a condensed polydimethylsiloxane prepolymer is first synthesized by a condensation reaction by dehydration or dealcoholization, preferably in the presence of the organic metal compound (E). To.

The polydimethylsiloxane (A) having a silanol group at both ends and the silane oligomer (B) having an alkoxy group are compounded in an adjusted molar ratio to be completely or partially hydrolyzed with dealcohol (or (B)) by heating. Dehydration) causes a condensation reaction. This reaction is controlled in several hours to several tens of hours to obtain a condensed polydimethylsiloxane-based prepolymer. A reaction vessel (flask with multiple insertion ports) equipped with a stirrer, a thermometer, and a dropping line is used for the synthesis. The stirrer is particularly limited as long as it has the effect of uniformly mixing high-viscosity liquid raw materials that contribute to the reaction, such as a rotary stirrer with stirring blades, a magnetic stirrer, a biaxial planetary stirrer, and an ultrasonic cleaner. There is no. However, a rotary stirrer, a magnetic stirrer, or the like is desirable because it is accompanied by temperature control, atmosphere control, component dropping line, and the like. Homogeneity is important for the synthesis temperature. The synthesis temperature is appropriately set between 60 and 140 ° C. It is set individually according to the type of raw material, blending ratio, synthesis equipment, etc., such as when reacting at low temperature for a long period of time or when synthesizing at high temperature for a short time. For the synthetic atmosphere, for example, nitrogen gas is used as the inert gas, and the reaction vessel is sufficiently filled with nitrogen gas having a constant water content. At this time, the nitrogen gas can be used not only from the nitrogen gas production apparatus but also from a cylinder or liquid nitrogen.

Regarding the molar ratio (blending ratio) of the polydimethylsiloxane (A) having a silanol group at both ends and the silane oligomer (B) having an alkoxy group, (B) is 0.5 with respect to 1 mol of (A) above. It is preferably adjusted in the range of ~ 4 mol. By advancing the condensation reaction under conditions suitable for condensation while the molar ratios of (A) and (B) are in the above range, gelation during or after the reaction is less likely to occur, and there is no residue of low molecular weight siloxane. A stable prepolymer can be obtained.

The molar ratio referred to here is the number average molecular weight (Mn) of PDMS measured by gel permeation chromatography (GPC method) using polystyrene as a standard substance and tetrahydrofuran as an eluent, and the oligomer of tetraalkoxysilane. It is a molar ratio calculated based on purity and average molecular weight.

In addition to the synthesized condensed polydimethylsiloxane-based prepolymer, a linear (n-) perfluoroalkyl group having 4 or more carbon atoms or a branched perfluoroalkyl group having 5 or more carbon atoms (steric hindrance should not be too large). Iso is preferred, but not limited to) reacting a silane compound with one and three methoxy groups (C; including complete or partially hydrolyzed / condensate). Since this compound (C) has a reactive alkoxysilyl group, a part of the previously prepared condensed polydimethylsiloxane prepolymer is hydrolyzed to have a reactive silanol group. Is preferable. Regarding the molar ratio (blending ratio) of the polydimethylsiloxane (A) having a silanol group at both ends and the silane compound (C), (C) is in the range of 1 to 9 mol with respect to 1 mol of the above (A). It is preferable to be adjusted.

The synthesized fluorine-containing condensed type organopolysiloxane prepolymer (F) becomes a fluorine-containing organopolysiloxane cured product having high transparency and UV resistance by heat treatment. It also has adhesiveness, and can be applied to UV-LED sealing materials, quartz lens and window material bonding materials, transparent insulating layers, and the like.

In the present invention, after a condensation reaction between both terminal silanol polydimethylsiloxanes and a silane oligomer having an alkoxy group, an n-perfluoroalkyl group having 4 or more carbon atoms or a branched perfluoroalkyl group having 5 or more carbon atoms is immediately formed. A fluorine-containing condensed organopolysiloxane prepolymer is prepared by reacting a silane compound (or a completely or partially hydrolyzed / condensate) having three methoxy groups. This prepolymer becomes an elastic material having flexibility and mechanical properties with a thick film of 1 mm or more, which was impossible with conventional materials having UV resistance by thermosetting.

<Preparation of highly adhesive fluorine-containing condensation type organopolysiloxane prepolymer (G)>
When it is difficult to apply with the adhesive strength of the fluorine-containing organopolysiloxane cured product, a compound having an isocyanurate ring structure, a terminal epoxy group or an epoxy group, and a terminal alkoxy group (D) for the purpose of improving the adhesive strength. ) Can be compounded. By this compounding, the adhesiveness can be improved without significantly impairing the heat resistance and the light resistance.

The fluorine-containing condensed organopolysiloxane prepolymer of the present invention can be packed in a UV-LED package and used as a sealing material. Since it is possible to impart adhesive strength, it can be used for fixing UV-LED quartz window materials and as a coating film, and because of its high flexibility, it can be used for adhesion between substrates with different coefficients of thermal expansion. Can also be used. Further, since it has high UV resistance, it can be applied and developed to an optical member that uses light in the visible short wavelength region from UV of 250 nm to 450 nm. Further, since it is also a material that partially transmits an infrared region such as 3 μm to 4.5 μm, it can be used as a bonding material for each member such as a sensor component by utilizing its adhesive strength and light resistance.

The cured product obtained from the fluorine-containing condensed organopolysiloxane prepolymer of the present invention can be used as a sealing layer or an adhesive layer having excellent light resistance and heat resistance in the UV region, and is deformed and broken by UV light for a long period of time. It is a material that does not cause deterioration of characteristics such as discoloration and peeling. In addition, by blocking the UV-LED element from disturbance factors such as water and various gases, the application of UV-LED becomes active, and it is possible to give great effects on the environment such as sterilization of water and reduction of power consumption. ..

As described above, the encapsulant for the LED light emitting device according to the present invention includes the fluorine-containing condensation type organopolysiloxane prepolymer according to the present invention.

Further, the adhesive for an optical member having a wavelength of 450 nm or less according to the present invention includes a fluorine-containing condensed type organopolysiloxane prepolymer according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The toluene content in PDMS in the examples was measured by gas chromatography.

[Examples 1 to 6]
[Preparation of fluorine-containing condensation type organopolysiloxane prepolymer (F)]
The reaction vessel equipped with the stirrer, thermometer, and dropping line was sufficiently filled with nitrogen gas. At this time, as the nitrogen gas, a nitrogen gas produced by a nitrogen gas production apparatus (UNX-200 manufactured by Japan Unix Co., Ltd.) was used.

Next, PDMS (A) having silanol groups at both ends, an oligomer (B) of tetraalkoxysilane, and a solvent are put into the reaction vessel sufficiently filled with the nitrogen gas to homogenize the reaction vessel. After stirring to, the condensation catalyst was added and the reaction was carried out at 120 ° C. for 1 hour. As the oligomer (B), a product distilled by an evaporator (130 ° C. for 2 hours) was used. Then, it was allowed to cool naturally to room temperature to obtain a condensed polydimethylsiloxane-based prepolymer. A silane compound ((C); hereinafter, a fluorine-based silane coupling agent) having one n-perfluoroalkyl group having four or more carbon atoms and three methoxy groups is added to the prepolymer, and nitrogen is used in the same manner as described above. Was charged and mixed until it became transparent, and then reacted at 120 ° C. for 2 hours and naturally cooled to room temperature to obtain a fluorine-containing condensed organopolysiloxane prepolymer (F).

Tables 1 and 2 show the names and masses of the raw materials used, their respective molar ratios, solvents, condensation catalysts, etc., and the amounts added.

PDMS (A); PLY2-7630 manufactured by Nusil (number average molecular weight (Mn) 27100, Mw / Mn = 2.21), PRO-2369 manufactured by Nusil (number average molecular weight (Mn) 54300, Mw / Mn = 1. 94) is used.
Silicate oligomer (B); ethyl silicate, manufactured by Tama Chemical Industry Co., Ltd., silicate 40: oligomer which is a linear 4 to hexamer of tetraethoxysilane, average molecular weight = 745. Distilled and purified at 130 ° C. for 2 hours is used. ..
Fluorine-based silane coupling agent (C): Trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (T2917 manufactured by Tokyo Chemical Industry Co., Ltd .; molecular weight = 568.30), trimethoxy (1H, 1H, 2H, 2H) -Nonafluorohexyl) silane (T2918 manufactured by Tokyo Chemical Industry Co., Ltd .; molecular weight = 368.27) is used.
Solvent: tert-butyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used.

[Comparative Examples 1 to 3]
The reaction vessel equipped with the stirrer, thermometer, and dropping line was sufficiently filled with nitrogen gas. At this time, as the nitrogen gas, a nitrogen gas produced by a nitrogen gas production apparatus (UNX-200 manufactured by Japan Unix Co., Ltd.) was used.

Next, PDMS (A) or (a) having silanol groups at both ends, an oligomer (B) of tetraalkoxysilane, and a solvent are put into the reaction vessel sufficiently filled with the nitrogen gas. After stirring until homogeneous, the condensation catalyst was added and the reaction was carried out at 120 ° C. for 1 hour. Then, it was allowed to cool naturally to room temperature to obtain a condensed polydimethylsiloxane-based prepolymer. The prepolymer is a silane compound having one n-perfluoroalkyl group having four or more carbon atoms or one carbon number and three methoxy groups ((C) or (c); hereinafter, a fluorosilane coupling agent). Was filled with nitrogen in the same manner as described above, mixed until it became transparent, and then reacted at 120 ° C. for 2 hours and naturally cooled to room temperature to obtain a fluorine-containing condensed organopolysiloxane prepolymer (f). However, Comparative Example 1 does not use a fluorine-based silane coupling agent.

Table 3 shows the names and masses of the raw materials used, their respective molar ratios, solvents, condensation catalysts, etc. and their addition amounts.

PDMS (A); PLY2-7630 (number average molecular weight (Mn) 27100, Mw / Mn = 2.21) manufactured by Nusil is used.
PDMS (a): FM9927A manufactured by JNC Corporation (number average molecular weight (Mn) ≈29500, Mw / Mn = 1.10) is used.
Silicate oligomer (B); ethyl silicate, manufactured by Tama Chemical Industry Co., Ltd., silicate 40: oligomer which is a linear 4 to hexamer of tetraethoxysilane, average molecular weight = 745. Distilled and purified at 130 ° C. for 2 hours is used. ..
Fluorine-based silane coupling agent (C): Trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (T2917 manufactured by Tokyo Chemical Industry Co., Ltd .; molecular weight = 568.30) is used.
Fluorine-based silane coupling agent (c): Trimethoxy (3,3,3-trifluoropropyl) silane (T2720 manufactured by Tokyo Chemical Industry Co., Ltd .; molecular weight: 218.25) is used.
Solvent: tert-butyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used.

[Creation of hardener]
14.07 g of 4 to hexamer silicate oligomer (ethyl silicate 40 manufactured by Tama Chemical Co., Ltd .; distilled refined product), zirconyl 2-ethylhexanoate (Nippon Kagaku) in a sealable plastic container that can be installed in a stirring defoaming device. 3.72 g of Nikkaoctix zirconium (12%) manufactured by Sangyo Co., Ltd. and 2.21 g of zinc 2-ethylhexanoate (18% Nikkaoctix zinc manufactured by Nippon Kagaku Sangyo Co., Ltd.) were added, and the mixture was sufficiently stirred and then tert-butyl alcohol was added. 2 g is added, and the mixture is further stirred and used as a curing agent.

[Preparation of highly adhesive fluorine-containing condensation type organopolysiloxane prepolymer (G)]
[Examples 7 and 8 and Comparative Example 4]
Fluorine-containing condensed organopolysiloxane prepolymers (F) and (f') were obtained in the same manner as in Examples 1 to 6. A pre obtained by dissolving a compound having an isocyanurate ring structure, a terminal epoxy group or an epoxy group, and a terminal epoxy group (D; hereinafter, a high-performance epoxy compound) with a solvent having the same weight as (D). It was added to the polymers (F) and (f') and reacted at 100 ° C. for 15 minutes with stirring to obtain highly adhesive fluorine-containing condensed organopolysiloxane prepolymers (G) and (g).

Table 4 shows the names and masses of the raw materials used, their respective molar ratios, solvents, condensation catalysts, etc. and their addition amounts.

PDMS (A); PLY2-7630 manufactured by Nusil (number average molecular weight (Mn) 27100, Mw / Mn = 2.21) was used.
PDMS (a): FM9927A manufactured by JNC Corporation (number average molecular weight (Mn) 29500, Mw / Mn = 1.10) is used.
Silicate oligomer (B); ethyl silicate, manufactured by Tama Chemical Industry Co., Ltd., silicate 40: oligomer which is a linear 4 to hexamer of tetraethoxysilane, average molecular weight ≈745. Distilled and purified at 130 ° C. for 2 hours is used. ..
Fluorine-based silane coupling agent (C): Trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (T2917 manufactured by Tokyo Chemical Industry Co., Ltd .; molecular weight = 568.30) is used.
High-performance epoxy compound (D): High-performance epoxy compound TEPIC-PAS B22 (epoxy equivalent: 180 to 200 g / eq) manufactured by Nissan Chemical Industries, Ltd. is used.
Solvent: tert-butyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used.

[Evaluation of light transmittance]
[Preparation of evaluation sample]
On a quartz substrate of 10 mm × 20 mm and a thickness of 0.5 mm, 3 parts by weight of the above-mentioned curing agent was added to 100 parts by weight of the prepolymer containing a solvent, and a stirrer manufactured by Shinky (Shinky Co., Ltd. ) Was stirred and defoamed. Then, a vacuum defoaming treatment was performed for 15 minutes, a quartz substrate of the same size was placed on the quartz substrate, the film thickness was adjusted to 10 μm, and heat treatment was performed at 80 ° C. for 30 minutes and then at 220 ° C. for 3 hours.

[Exposure test at wavelength 258 nm]
The sample prepared by the above method was continuously irradiated for up to 1000 hours with an illuminance of 258 nm and an output of 17 mW / m ² using a low-pressure mercury lamp using SSP16-110 manufactured by Sen Special Light Source Co., Ltd., and the appearance and wavelength were 265 nm. The changes in transmittance at 300 nm and 350 nm were compared in 500 hours and 1000 hours from the initial stage. The results are shown in Table 5.

[Adhesive strength confirmation test]
Preparation of Evaluation Sample To 100 parts by weight of the prepolymer of Example 1, Example 7, Example 8 and Comparative Example 4, 10 parts by weight of the above-mentioned curing agent was added, and the mixture was sufficiently stirred with a stirring defoaming device. An adhesive polymer was prepared. According to JIS K 6850, each adhesive polymer was applied so that one end of two aluminum plates having a width of 25 mm, a length of 100 mm, and a thickness of 1 mm overlap each other with a width of 10 mm, and fixed with an office clip. This was pre-baked at 100 ° C. for 60 minutes in an electric furnace, and then heat-treated at 250 ° C. for 3 hours to prepare a sample for evaluation. A tensile test was performed on an autograph AGS-J manufactured by Shimadzu Corporation in accordance with JIS K 6850. The adhesive strength measurement results (tensile test results (n = 3)) are shown in Table 6.

(Evaluation results)
From the results in Table 5, it can be seen that the cured product obtained from the fluorine-containing condensed organopolysiloxane prepolymer of the present invention has excellent transparency and light resistance. On the other hand, the one without using the fluorine-based silane coupling agent (Comparative Example 1) used PDMS having Mw / Mn of 1.3 or less, which caused cracks after 500 hours of irradiation at 258 nm (Comparative Example 3). And the one using trimethoxy (3,3,3-trifluoropropyl) silane (Comparative Example 2) cracked in 1000 hours. It can be seen that even if a fluorine-based silane coupling agent is used, a fluoroalkyl group having a short chain length cannot withstand 1000 hours of UV irradiation at 258 nm.

Further, from Table 6, in order to improve the poor adhesion due to fluorine, a compound having an isocyanurate ring structure, a terminal epoxy group or an epoxy group, and a terminal alkoxy group (TEPIC-PAS B22) was used. In Examples 7 and 8, the transparency was slightly impaired, but the adhesive strength was improved.

[Change example]
In the above examples, the present invention is not limited to this, and organometallic compounds of different types and properties may be used.

It should be considered that the embodiments and examples disclosed above are exemplary in all respects and not restrictive. The scope of the present invention is not shown in the above embodiments and examples, but is indicated by the scope of claims, and includes all modifications and modifications within the meaning and scope equivalent to the scope of claims.

The fluorine-containing condensed organopolysiloxane prepolymer of the present invention can be used as a highly light-resistant encapsulant, adhesive, and optical material in an optical member using ultraviolet rays of 370 nm or less, and can be used in the UV region. As a stable material for a long period of time with excellent light transmission, it is useful for producing ultraviolet light emitting members for sterilization and medical applications.

Claims (10)

A fluorine-containing condensed organopolysiloxane prepolymer prepared by subjecting the following (A), the following (B), and the following (C) to a condensation reaction.
(A) A polydimethylsiloxane having silanol groups at both ends and having a molecular weight distribution index (Mw / Mn; Mw is a weight average molecular weight and Mn is a number average molecular weight) of 1.3 or more.
(B) Tetraalkoxysilane oligomers and / or complete or partial hydrolysates or condensates of said oligomers.
(C) A silane compound having a linear (n-) perfluoroalkyl group having 4 or more carbon atoms or a branched perfluoroalkyl group having 5 or more carbon atoms and 3 methoxy groups, and / or the above. A complete or partial hydrolyzate or condensate of a silane compound. The fluorine-containing condensed organopolysiloxane prepolymer according to claim 1, wherein (A) has a number average molecular weight (Mn) of 15,000 to 70,000. The fluorine-containing condensed organopolysiloxane prepolymer according to claim 1 or 2, wherein (B) is a linear tetramer to a tetramer and has a methoxy group or an ethoxy group as an alkoxy group. .. The fluorine-containing condensed organopolysiloxane prepolymer according to claim 3, wherein 0.5 to 4 mol of (B) is blended with respect to 1 mol of (A). The fluorine-containing condensed organopolysiloxane prepolymer according to any one of claims 1 to 4, wherein 1 to 9 mol of the (C) is blended with respect to 1 mol of the (A). The compound (D) having an isocyanurate ring structure, an epoxy group or a terminal epoxy group, and a terminal alkoxy group is added to a total of 100 parts by weight of the above (A), the above (B) and the above (C). The fluorine-containing condensed organopolysiloxane prepolymer according to any one of claims 1 to 5, which is blended in an amount of 0.1 to 5 parts by weight. A sealing material for an LED light emitting element having a wavelength of 450 nm or less, which comprises the fluorine-containing condensation type organopolysiloxane prepolymer according to any one of claims 1 to 6. An adhesive for an optical member having a wavelength of 450 nm or less, which comprises the fluorine-containing condensed type organopolysiloxane prepolymer according to any one of claims 1 to 6. The cured product of the fluorine-containing condensed type organopolysiloxane prepolymer according to any one of claims 1 to 6. The cured product according to claim 9, wherein when the thickness is 10 μm, the transmittance at a wavelength of 265 nm is 75% or more, the transmittance at 300 nm is 80% or more, and the transmittance at 350 nm is 90% or more.