JPH0254861B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has excellent adhesion to base materials such as plastic, rubber, glass, and metal at room temperature or with slight heating, and is capable of preventing cracks inside the gel and base materials due to thermal shock. The present invention relates to a gel composition for optical bonding that can form a stable gel-like material that does not peel off from the substrate and does not discolor or change physical properties at high temperatures. [Prior Art] Conventionally, various technologies have been known for compositions that can be cured to form gel-like polyorganosiloxanes through an addition reaction between a hydrosilyl group and a silicon-bonded vinyl group.・Widely used as potting materials for electronic devices, encapsulations, and implants in surgical procedures. Regarding such a polyorganosiloxane composition, JP-A-48-17847 discloses that the amount of hydrogen atoms bonded to the silicon atom is one or less per vinyl group bonded to the silicon atom, and The average amount per molecule of organohydrodiene siloxane
A composition in which an amount corresponding to 1.4 to 1.8 is present,
Also, JP-A-54-15957 and JP-A-54-48720
In the publication, the amount of hydrogen atoms per vinyl group is
A composition in which a relatively small amount of around 0.3 to 0.8 is present is disclosed, and as a vinyl group-containing polyorganosiloxane, JP-A-54-15957 discloses polydimethylsiloxane end-capped with methylvinylphenylsiloxy groups. , Japanese Patent Publication No. 54-48720
The publication proposes the use of a polysiloxane containing in one molecule at least two vinyl groups and one hydroxyl group bonded to silicon atoms. However, such compositions that can be cured into a gel-like state or gel-like products obtained therefrom have the following drawbacks in common. Due to its low adhesiveness, it does not adhere to the base material, and when used for potting electronic equipment parts, a gap is created between the part and the gel-like material, and moisture can penetrate through the gap, causing corrosion and poor insulation. . Since the vinyl groups remaining in the gel-like material are oxidized at high temperatures, it has poor heat resistance in an oxidizing atmosphere. Since the amount of polyorganohydrodiene siloxane in the composition is small, errors in blending the siloxane or the mixture containing it during blending immediately before curing can cause a significant difference in the softness of the gel-like product. The methylvinylphenylsiloxy terminal group as shown in JP-A-54-15957 is difficult to synthesize. [Problems to be solved by the invention] In order to solve these problems,
Publication No. 143241 basically discloses a composition in which the hydrogen atoms are present in an amount of 0.5 to 5 per vinyl group, thereby almost solving the above problems. However, in all of these compositions that can be cured into a gel-like state, cracks occur inside the silicone gel due to thermal shock, making it impossible to achieve the purpose of optical bonding. In addition, in recent years, transparent plastics have begun to be used in addition to glass in optical bonding applications, and conventional gels have poor adhesion to these plastics and can sometimes peel off from the base material due to thermal shock. . [Means for Solving the Problems] The present invention eliminates these drawbacks, has excellent adhesion to the base material, and does not cause cracks in the silicone gel or peeling from the base material due to thermal shock. The present invention also provides a stable gel composition for optical bonding that does not discolor at high temperatures. The present inventors investigated compositions that solve these problems, and found that instead of the conventionally used polyorganohydrodiene siloxane, compounds with the general formula R ¹ Si (OSiR ² ₂ H) ₃ , (R ¹ , R ² is as mentioned above)
The present inventors have found that the object can be achieved by using a siloxane represented by the following formula and adjusting the amount of the catalyst metal element to the polyorganosiloxane mixture from 0.01 to 30 ppm, and have completed the present invention. That is, the present invention provides (A) an average of 0.1 to 2.0 vinyl groups bonded to the silicon atom in one molecule, and the remaining organic groups bonded to the silicon atom are substituted or unsubstituted vinyl groups that do not contain aliphatic unsaturation. Polyorganosiloxane (B), which is a monovalent hydrocarbon group and has a viscosity of 50 to 100000 cP at 25°C, has the general formula R ¹ Si (OSiR ² ₂ H) ₃ (wherein R ₁ is a C ₁ to C ₄ alkyl or phenyl group, R ² represents a C ₁ to C ₄ alkyl group), the number of hydrogen atoms bonded to the silicon atom is (A) per vinyl group bonded to the silicon atom. an amount of 0.1 to 0.8 or 1.5 to 3.0; and (C) a catalyst selected from the group consisting of a platinum-based catalyst, a palladium-based catalyst, and a rhodium-based catalyst; (A) and (B)
0.01~ as the amount of catalytic metal element relative to the total amount of
The present invention relates to a gel composition for optical bonding, characterized in that the content is 30 ppm. The polyorganosiloxane as component (A) used in the present invention has an average of 0.1 to 2.0, preferably 0.1 to 1.4 vinyl groups bonded to silicon atoms in one molecule. When the amount of vinyl groups is less than 0.1, the amount of polyorganosiloxane that does not participate in crosslinking increases, and the physical properties of the gel-like product obtained by curing and the adhesion to the substrate are significantly reduced. Furthermore, if the amount of vinyl groups is more than 2.0, the feature of the present invention, which is to obtain a soft gel-like material that does not discolor at high temperatures, cannot be exhibited. Among the organic groups bonded to the silicon atom of the polyorganosiloxane (A), those other than the vinyl group mentioned above include methyl group, ethyl group, propyl group, butyl group, amino group, hexyl group, octyl group, decyl group. group, alkyl group such as dodecyl group, aryl group such as phenyl group, aralkyl group such as β-phenylethyl group, β-phenylpropyl group, and chloromethyl group, cyanoethyl group, 3,
Substituted hydrocarbon groups such as 3,3-trifluoropropyl groups are examples, but methyl groups are preferred because of their ease of synthesis, ease of handling in an uncured state, and the heat resistance and physical properties of gel-like products. It is preferable that In addition, when occlusion resistance is required, up to 8 mol% of the total organic groups, and when particularly high heat resistance, radiation resistance, or high refractive index is required, up to 50 mol% of the total organic groups. It is recommended to introduce a phenyl group. Viscosity is 50~100000cP at 25℃,
Preferably, it is selected from the range of 300 to 5000 cP. When used for potting, a range of 500 to 1500 cP is most preferred. If it is lower than 50cP, it will flow easily and the physical properties after reaction will be poor. Also
If it exceeds 100000cP, workability will deteriorate. The siloxane skeleton of the polyorganosiloxane (A) may be linear or branched, or may be a mixture of both, but from the viewpoint of ease of synthesis and imparting appropriate softness to the gel-like material, Preferably, it is linear. It is acceptable for a small amount of cyclic polyorganosiloxane to coexist, but even if it has a vinyl group bonded to a silicon atom, its reactivity is low and it does not contribute to the formation of a sticky gel. The vinyl group in polyorganosiloxane may be bonded to either a silicon atom in the middle of the molecule or a silicon atom at the end of the molecule, but it is preferable to bond to the silicon atom at the end due to the reaction rate and the effect of forming a gel-like substance due to the reaction. It is preferable to do so. Such polyorganosiloxane (A) is made of, for example, a vinyl group-containing polyorganosiloxane that has vinyl groups bonded to silicon atoms at both ends, and a linear or branched polyorganosiloxane that does not contain vinyl groups. If available, it is blended with a polydiorganosiloxane that does not contain vinyl groups to satisfy the average molecular weight and amount of vinyl groups that achieve the above-mentioned viscosity range, and an acid catalyst such as sulfuric acid, hydrochloric acid, activated clay, or potassium hydroxide. It is synthesized by cutting and equilibrating siloxane using conventional methods in the presence of an alkali catalyst such as tetramethylammonium hydroxide. In this case, a cyclic polysiloxane, particularly a cyclic polysiloxane containing no vinyl group, may be used in combination as part of the raw material. After equilibration, the catalyst is removed by a conventional method, and by-product or unreacted low-molecular-weight polyorganosiloxane is removed by heating under reduced pressure, thereby purifying the product. The siloxane component (B) used in the present invention is represented by the general formula R ¹ Si (OSiR ² ₂ H) ₃ and reacts with the vinyl group of the polyorganosiloxane (A) to form a gel-like substance. This is a feature of the present invention. R ¹ is a methyl group, an ethyl group, a propyl group,
Examples include an alkyl group such as a butyl group; and a phenyl group; however, a methyl group or a phenyl group is preferred because it is easy to synthesize and provides a good gel-like product. In addition, R ² is a methyl group, an ethyl group,
Examples include alkyl groups such as propyl group and butyl group, but methyl group is preferred from the viewpoint of ease of obtaining materials and synthesis. These siloxanes may be used alone or in combination of two or more.
Methyltrimethoxysilane and
It can be easily obtained by cohydrolyzing phenyltrimethoxysilane and chlorosilane such as dimethylchlorosilane. The blending amount of component (B) is 0.1 to 0.8 or 1.5 to 3.0 hydrogen atoms to be bonded to the silicon atom in component (B) for each vinyl group bonded to the silicon atom in component (A).
, preferably 0.3 to 0.8. If it is less than 0.1, crosslinking will not proceed sufficiently and the gel-like material will not only become too soft but also become noticeably discolored at high temperatures. Further, if the number exceeds 0.8 and is less than 1.5, the cured product will become rubber-like, and if the number exceeds 3.0, the resulting gel-like material will become hard over time. The catalyst of component (C) used in the present invention is for promoting the addition reaction between the vinyl group of component (A) and the hydrosilyl group of component (B), and is a catalyst of chloroplatinic acid, alcohol-modified platinum chloride, etc. Acids, platinum-based catalysts exemplified by complexes of platinum and olefins, complexes of platinum and ketones, complexes of platinum and vinylsiloxane, tetrakis(triphenylphosphine)palladium, palladium black and triphenylphosphine, etc. Palladium-based catalysts or rhodium-based catalysts such as mixtures of the following can be used, but platinum-based catalysts are preferred from the viewpoint of catalytic effect and ease of handling.
The blending amount of component (C) is such that the amount of the catalytic metal element is in the range of 0.01 to 30 ppm based on the total amount of (A) and (B). If it is less than 0.01 ppm, the addition reaction will not proceed sufficiently and the gel will become too soft.
If it exceeds 30 ppm, discoloration at high temperatures will become significant and the features of the present invention will not be exhibited. The composition of the present invention may be stored in a single container by the presence of a reaction inhibitor such as an acetylenic compound or by using a platinum-based catalyst with low activity at room temperature. Store (B) in the same container and (C) in another container, or store part of (A) in combination with (B), or most of (A) with (C) in separate containers, and store them immediately before hardening. It may be used after uniformly mixing and defoaming under reduced pressure. Furthermore, by adding an inorganic filler to the composition of the present invention as needed, workability, hardness after curing, mechanical strength, etc. can be adjusted depending on the application. Examples of such inorganic fillers include fumed silica, silica aerogel, and precipitated silica. Also,
Solvents such as toluene and hexane, viscosity modifiers such as polydimethylsiloxane, additional base polymers such as alkenyl-containing polysiloxanes, cure inhibitors such as acetylene alcohol and its reaction products with polysiloxanes, etc. , may be used in combination to the extent that the effects of the present invention are not lost. [Effects of the Invention] According to the present invention, the silicone gel has excellent adhesion to the substrate at room temperature or by slight heating, does not cause cracks inside the silicone gel or peels from the substrate due to thermal shock, and does not discolor at high temperatures. A gel composition for optical bonding which forms a stable gel-like material with little change in physical properties was obtained. The composition of the present invention is useful for electrical and electronic parts, especially for potting, encapsulation, and human body parts, such as optical coupling pads that require optical transparency, and parts where design value is important. Used for making models, etc. [Example] Examples of the present invention will be shown below. In the examples, all parts are by weight, and viscosity is the viscosity at 25°C. In addition, the symbol Me,
Vi and Pn represent a methyl group, a vinyl group and a phenyl group, respectively. Example 1 Compositions 1 to 6 were prepared by uniformly mixing the materials shown below according to the blending ratios shown in Table 1. However, compositions 1 and 2 are products of the present invention, and compositions 3 to 6 are comparative products. <(A) As a component> Polysiloxane A-1: Average formula A polydimethylsiloxane containing a vinyl group represented by: Viscosity: 650 cP (as component (B)) B-1: Siloxane represented by PhSi (OSiMe ₂ H) ₃ B-2: Siloxane represented by MeSi (OSiMe ₂ H) ₃ B-3: Average formula Polymethylhydrodienesiloxane represented by B-4: Average formula Polymethylhydrodienesiloxane represented by B-5: Average formula Polymethylhydrodienesiloxane represented by <As component (C)> C-1: One obtained by heating chloroplatinic acid and tetramethyltetravinylcyclotetrasiloxane. Platinum content: 2.0% by weight as platinum

[Table] Number of cures When these compositions were heated at 50° C. for 2 hours, they were all cured to give corresponding transparent gels 1 to 6. ASTM D-1403
When the penetration of the gel-like material was measured according to
Values as shown in the initial values in Table 2 were obtained. Heat Resistance Test Gel products 1 to 6 obtained by curing were placed in an air circulation oven at 150°C, and changes in penetration over time were measured, and the degree of discoloration was measured using APHA values. The results are shown in Table 2. Thermal Shock Test 40g of the compositions No. 1 to 6 were tested at an inner diameter of 18mm and a depth of 180mm.
It was injected into a glass test tube with a diameter of -20 mm and heated at 50℃ for 2 hours to harden.
A thermal shock test was conducted a predetermined number of times with a cycle of ℃/2h←→80℃/2h, and the presence or absence of cracks inside the gel was visually confirmed. The results are shown in Table 2. Adhesion test No.1 by applying a spacer to the test piece shown in Figure 1.
The compositions No. 6 to 6 were injected and cured by heating at 50° C. for 2 hours, and then the spacer was removed. These were pulled in a direction perpendicular to the adhesive surface at 50 mm/min using a tensile tester with an autograph (manufactured by Shimadzu Corporation), and the maximum tensile stress, elongation at break, and cohesive failure rate were measured. The results are shown in Table 2.

[Table] △: There are some cracks inside the gel, but there are relatively few cracks.
×: Cracks occur in the entire gel. From these results, the composition according to the present invention shows little discoloration due to heating, has excellent impact resistance, and has extremely good adhesion. Example 2 Polysiloxane A-1 used in Example 1 100
Average formula instead of part Example 1 except that a polyorganosiloxane containing a vinyl group and a phenyl group represented by was used.
A composition was obtained with the same blending ratio as No. 1. this thing
When heated at 50℃ for 2 hours, the penetration was 67.
A gel-like material with an APHA value of 10 was obtained. Furthermore, at 150℃
After heating for 1000 hours, penetration rate was 60 and APHA value
25 and kept in good condition. In addition, the same impact resistance test and adhesion test as in Example 1 were conducted, but no cracks were observed in the impact resistance test even after 100 cycles.
Further, the adhesion test showed good values such as maximum tensile stress of 110 gf/cm ² , elongation at break of 900%, and cohesive failure rate of 100%.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a test specimen used for measurement in an adhesion test. Note that the unit of numerical values in the figure is mm. 1...Acrylic resin board, 2...Silicone gel.

Claims (1)

[Claims] 1 (A) An average of 0.1 to 2.0 vinyl groups bonded to the silicon atom exist in one molecule, and the remaining organic groups bonded to the silicon atom are substituted or non-substituted without aliphatic unsaturation. Polyorganosiloxane (B) which is a substituted monovalent hydrocarbon group and has a viscosity of 50 to 100000 cP at 25°C. General formula R ¹ Si (OSiR ² ₂ H) ₃ (wherein R ¹ is C ₁ to C ₄ (A) is an alkyl group or phenyl group, ^R2 represents a _C1 to _C4 alkyl group), and the number of hydrogen atoms bonded to the silicon atom is equal to one vinyl group bonded to the silicon atom of (A). (C) a catalyst selected from the group consisting of platinum-based catalysts, palladium-based catalysts, and rhodium-based catalysts; (A) and (B);
0.01~ as the amount of catalytic metal element relative to the total amount of
A gel composition for optical bonding characterized by comprising an amount of 30 ppm. 2. The composition according to claim 1, wherein the vinyl group bonded to the silicon atom of (A) is present at the end of the molecule. 3. The composition of claim 1, wherein (A) is a substantially linear polyorganosiloxane. 4. The organic group other than the vinyl group bonded to the silicon atom in (A) is a monovalent hydrocarbon group selected from the group consisting of a methyl group and a phenyl group, and the amount of the phenyl group is The composition according to claim 1, wherein the content is 50 mol% or less. 5. The composition according to claim 4, wherein the organic group other than the vinyl group bonded to the silicon atom in (A) is a methyl group. 6. The composition according to claim 1, wherein (A) has a viscosity of 300 to 5000 cP at 25°C. 7 (B) R ¹ is a methyl group or a phenyl group,
A composition according to claim 1. 8. The composition according to any one of claims 1 to 7, wherein R ² in (B) is a methyl group. 9. A patent claim in which the amount of (B) is such that the number of hydrogen atoms bonded to the silicon atom of (B) is 0.3 to 0.8 per vinyl group bonded to the silicon atom of (A) The composition according to item 1. 10. The composition according to claim 1, wherein the catalyst in (C) is a platinum-based catalyst.