JP7626147B2 - Primer Composition - Google Patents

Description

The present invention relates to a primer composition, and more specifically to a primer composition that imparts adhesion between an adherend, such as a polyimide resin, and a cured silicone material.

Silicone rubber has excellent heat resistance, cold resistance, light resistance, electrical insulation, etc., and has traditionally been used as an adhesive sealant, electrical insulation material, potting material, etc. In this case, if the adhesive strength of the silicone rubber to the substrate is insufficient, it is common to first treat the substrate with a primer.

Known primer compositions for the cured products of addition-curing silicone compositions used in adhesive sealants, electrical insulating materials, potting materials, etc. include compositions consisting of silane coupling agents and/or their reaction products, polyester resins, acrylic resins, and compositions consisting of phenyl-containing siloxanes, alkyl silicates, and chlorosilanes.

In recent years, polyimide resins have been used in various applications as high-performance materials with excellent mechanical strength, heat resistance, electrical insulation, and the like. The applications are diverse, and examples include flexible printed circuits. When a substrate is converted to a polyimide resin with excellent heat resistance, materials with excellent heat resistance are also required for the peripheral materials. For this reason, it is expected that the use of silicone materials in polyimide components will increase. However, in general, silicone cured products are difficult to adhere to polyimide resins, and a method for improving adhesion to polyimide resins is required.
Prior art documents related to the present invention include the following:

JP 2020-19909 A

The present invention has been made in consideration of the above circumstances, and aims to provide a primer composition that can firmly bond an adherend, such as a polyimide resin, to a cured silicone material.

As a result of extensive research into achieving the above object, the inventors discovered that a composition containing a (meth)acrylic acid ester (co)polymer and an organosilicon compound having a specific functional group introduced therein can firmly bond an adherend such as a polyimide resin to a cured silicone material, thereby completing the present invention.

（式中、Ｒ¹およびＲ²は、互いに独立に、炭素数１～４のアルキル基であり、Ｒ³は、互いに独立に、炭素数１～３０の２価炭化水素基であり、Ｒ⁴は、互いに独立に、炭素数１～６のアルキレン基またはカルボニル基であり、Ｒ⁵は、互いに独立に、炭素数１～２０の１価炭化水素基であり、ａは、互いに独立に、０または１であり、ｂは、０～３の整数である。）
（Ｃ）テトラアルコキシチタン、テトラアルコキシジルコニウム、テトラアルコキシスズ、トリアルコキシアルミニウムおよびこれらの部分加水分解物から選ばれる１種以上の縮合触媒と、
（Ｄ）溶剤と
を含有するプライマー組成物、
２． （Ａ）成分を構成するアクリル酸エステル、メタクリル酸エステルまたはこれらの両方が、１分子中に１個以上のＳｉＨ基を有する化合物を含む１記載のプライマー組成物、
３． （Ｂ）成分が、上記式（１）で表される有機ケイ素化合物を含み、かつ、Ｒ⁴が、カルボニル基である１または２記載のプライマー組成物、
４． さらに、（Ｅ）下記式（３）で表される有機ケイ素化合物を含む１～３のいずれかに記載のプライマー組成物、
（Ｒ⁶Ｏ）_cＲ⁷ _dＳｉ （３）
（式中、Ｒ⁶は、互いに独立に、炭素数１～４のアルキル基であり、Ｒ⁷は、互いに独立に、ハロゲン原子、アクリル基、メタクリル基またはエポキシ基で置換されていてもよい炭素数１～１０の１価炭化水素基であり、ｃは、１～４の整数であり、ｄは、０～３の整数であり、ｃ＋ｄ＝４である。）
５． １～４のいずれかに記載のプライマー組成物を被着体上に供給する工程と、
前記プライマー組成物を供給した被着体上に、硬化性シリコーン組成物を配置し、このシリコーン組成物を硬化させる工程と
を有する被着体とシリコーン硬化物との接着方法、
６． 被着体が、ポリイミド樹脂である５記載の接着方法
を提供する。 That is, the present invention provides
1. (A) an acrylic acid ester, a methacrylic acid ester, or a (co)polymer of both of these;
(B) an organosilicon compound represented by the following formula (1), an organosilicon compound represented by the following formula (2), or both of these:

(In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 4 carbon atoms, R ³ are each independently a divalent hydrocarbon group having 1 to 30 carbon atoms, R ⁴ are each independently an alkylene group or a carbonyl group having 1 to 6 carbon atoms, R ⁵ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, a is each independently 0 or 1, and b is an integer from 0 to 3.)
(C) one or more condensation catalysts selected from tetraalkoxytitanium, tetraalkoxyzirconium, tetraalkoxytin, trialkoxyaluminum, and partial hydrolysates thereof;
(D) a primer composition containing a solvent;
2. The primer composition according to 1, wherein the acrylic acid ester, the methacrylic acid ester, or both of them constituting the component (A) contain a compound having one or more SiH groups in one molecule;
3. The primer composition according to 1 or 2, wherein the component (B) contains an organosilicon compound represented by the above formula (1) and ^R4 is a carbonyl group.
4. The primer composition according to any one of 1 to 3, further comprising (E) an organosilicon compound represented by the following formula (3):
(R ⁶ O) _c R ⁷ _d Si (3)
(In the formula, R ⁶ are each independently an alkyl group having 1 to 4 carbon atoms, R ⁷ are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an acrylic group, a methacrylic group, or an epoxy group, c is an integer of 1 to 4, d is an integer of 0 to 3, and c+d=4.)
5. A step of supplying the primer composition according to any one of 1 to 4 onto an adherend;
a step of placing a curable silicone composition on the adherend to which the primer composition has been applied, and curing the silicone composition;
6. The bonding method according to claim 5, wherein the adherend is a polyimide resin.

The primer composition of the present invention can firmly bond adherends such as polyimide resins to cured silicone materials, and is particularly useful as an adhesive for semiconductor devices that require high reliability.

The present invention will be specifically described below.
The primer composition according to the present invention contains (A) a (meth)acrylic acid ester (co)polymer, (B) an organosilicon compound, (C) a condensation catalyst, and (D) a solvent.

(1) Component (A) The component (A) is an acrylic acid ester, a methacrylic acid ester, or a (co)polymer of both of these.
A primer composition containing such component (A) forms a flexible film on an adherend and forms a bond through an addition reaction with the addition-curable silicone composition.
The (meth)acrylic acid ester constituting component (A) is preferably a (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 12 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isopentyl acrylate, n-hexyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isononyl acrylate, n-decyl acrylate, and isodecyl acrylate.

Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isononyl methacrylate, n-decyl methacrylate, and isodecyl methacrylate.

The (meth)acrylic acid ester constituting component (A) is preferably one having one or more SiH groups in one molecule.
Examples of the (meth)acrylic acid ester having one or more SiH groups in one molecule include compounds represented by the following formulas (4) to (6).

^R8 are each independently a hydrogen atom or a methyl group.
R ⁹ is, independently of each other, a monovalent organic group. The monovalent organic group of R ⁹ is preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 3 carbon atoms. Examples of the monovalent hydrocarbon group include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, pentyl, neopentyl, hexyl, and octyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl (2-propenyl), and 1-propenyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, and chlorine, or cyano groups, for example, chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl. R ⁹ is preferably a methyl group, an ethyl group, or a phenyl group, and particularly preferably a methyl group.

R ¹⁰ is, independently of each other, a divalent organic group. The divalent organic group of R ¹⁰ is preferably a non-substituted or substituted divalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 3 carbon atoms. Examples of the divalent hydrocarbon group include linear or branched alkylene groups such as methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, and octamethylene; cycloalkylene groups such as cyclohexylene; and arylene groups such as phenylene and naphthylene. In addition, some or all of the hydrogen atoms of these groups may be substituted with halogen atoms such as fluorine, bromine, and chlorine, or cyano groups, such as tetrafluoroethylene and hexafluoropropylene. As R ¹⁰ , a methylene group, an ethylene group, or a trimethylene group is preferable, and a trimethylene group is particularly preferable.

n is 0, 1 or 2. m is 0 or a positive integer, p is a positive integer, q and r are positive integers. In formulas (5) and (6), the arrangement of the siloxane units in parentheses may be arbitrary.
These (meth)acrylic acid esters may be used alone or in combination of two or more. The component (A) preferably contains a compound represented by formula (4), and it is particularly preferable to use other acrylic acid esters and/or methacrylic acid esters in combination with the compound represented by formula (4).
In this case, the use ratio of the other acrylic acid ester and/or methacrylic acid ester to the compound represented by formula (4) is not particularly limited, but the molar ratio of the other acrylic acid ester and/or methacrylic acid ester:the compound represented by formula (4) is preferably 1:1 to 20:1, more preferably 1:1 to 15:1, and even more preferably 1:1 to 10:1.

Examples of the compound represented by formula (4) include the following.

（式中、ｍおよびｐは、上記と同じである。括弧が付された各シロキサン単位の配列は、任意であってよい。） Examples of the compound represented by formula (5) include the following.

(In the formula, m and p are the same as above. The arrangement of the siloxane units in parentheses may be arbitrary.)

（式中、ｑおよびｒは、上記と同じである。各シロキサン単位の配列は、任意であってよい。） Examples of the compound represented by formula (6) include the following.

(In the formula, q and r are the same as above. The arrangement of the siloxane units may be arbitrary.)

As described below, the component (A) can be obtained by polymerizing a (meth)acrylic acid ester using a radical polymerization initiator such as 2,2'-azobisisobutyronitrile (AIBN).
The weight average molecular weight of the component (A) is not particularly limited, but is preferably from 100 to 500,000, and more preferably from 10,000 to 200,000. In the present invention, the weight average molecular weight is a value calculated using standard polystyrene by gel permeation chromatography (GPC).

The amount of component (A) to be blended is not particularly limited as long as it is an amount that dissolves in component (D) described below, but is preferably 0.1 to 20% by mass of the entire composition, more preferably 0.1 to 10% by mass, and even more preferably 0.5 to 5% by mass. If it is within such a range, it is possible to prevent the occurrence of unevenness on the surface of the resulting film, and it is possible to obtain sufficient performance as a primer composition.

(2) Component (B) Component (B) is an organosilicon compound represented by the following formula (1), an organosilicon compound represented by the following formula (2), or both of these.

^R1 and ^R2 are each independently an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms for ^R1 and ^R2 include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, and t-butyl, and are preferably a methyl group or an ethyl group.

^R3 's are each independently a divalent hydrocarbon group having 1 to 30 carbon atoms. Examples of the divalent hydrocarbon group represented by ^R3 include linear or branched alkylene groups such as methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, and octamethylene; cycloalkylene groups such as cyclohexylene; and arylene groups such as phenylene and naphthylene. Those having 3 to 8 carbon atoms are preferred, and a trimethylene group is more preferred.

^R4 is, independently of each other, an alkylene group or a carbonyl group having 1 to 6 carbon atoms. Examples of the alkylene group having 1 to 6 carbon atoms for ^R4 include linear or branched alkylene groups such as methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, and hexamethylene; cycloalkylene groups such as cyclohexylene; and arylene groups such as phenylene. ^R4 is preferably a carbonyl group.

R ⁵ is, independently of each other, a monovalent hydrocarbon group having 1 to 20 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms as R ⁵ include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, pentyl, neopentyl, hexyl, and octyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, and propenyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, and chlorine, or cyano groups, such as chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl. R ⁵ is preferably an alkyl group having 1 to 10 carbon atoms, particularly preferably an alkyl group having 1 to 8 carbon atoms, and more preferably a methyl group, an ethyl group, an n-propyl group, or a butyl group.

a's are each independently 0 or 1, and preferably 0. b's is an integer of 0 to 3, and preferably 0.
The component (B) may be used alone or in combination of two or more. The component (B) preferably contains a compound represented by formula (1), and more preferably, ^R4 is a carbonyl group.

Examples of the compound represented by formula (1) include the following.

Examples of the compound represented by formula (2) include the following.

The amount of component (B) blended is preferably 0.1 to 20% by mass of the entire composition, more preferably 0.1 to 10% by mass, and even more preferably 0.5 to 5% by mass. Within this range, the occurrence of unevenness on the surface of the resulting film can be prevented, and sufficient performance as a primer composition can be obtained.

(3) Component (C) The condensation catalyst of component (C) is one or more condensation catalysts selected from the group consisting of tetraalkoxytitanium, tetraalkoxyzirconium, tetraalkoxytin, trialkoxyaluminum, and partial hydrolysates thereof, and promotes the condensation reaction of the alkoxysilyl groups of component (B).
The alkoxy group of component (C) is preferably an alkyl group having 1 to 6 carbon atoms, and more preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, s-butoxy, and t-butoxy.

Examples of tetraalkoxytitanium include tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, and tetra-n-butoxytitanium, with tetra-n-butoxytitanium being particularly preferred.
Examples of tetraalkoxyzirconium include tetramethoxyzirconium, tetraethoxyzirconium, tetra-n-propoxyzirconium, tetraisopropoxyzirconium, and tetra-n-butoxyzirconium, with tetra-n-butoxyzirconium being particularly preferred.
Examples of tetraalkoxytin include tetramethoxytin, tetraethoxytin, tetra-n-propoxytin, tetraisopropoxytin, tetra-n-butoxytin, and tetra-t-butoxytin, with tetra-t-butoxytin being particularly preferred.
Examples of trialkoxyaluminum include aluminum(III) ethoxide, aluminum(III) isopropoxide, aluminum(III)-s-butoxide, aluminum(III)-n-butoxide, and mono-s-butoxyaluminum diisopropylate, with aluminum(III)-n-butoxide and mono-s-butoxyaluminum diisopropylate being preferred.
These may be used alone or in combination of two or more.

The amount of component (C) is preferably 1 to 300 parts by weight, and more preferably 20 to 250 parts by weight, per 100 parts by weight of component (B). Within this range, a coating with excellent strength can be obtained.

(4) Component (D) The solvent for component (D) is not particularly limited as long as it dissolves the above components (A), (B), and (C) and the optional components described below, and any known organic solvent can be used.
Examples of the solvent include aromatic hydrocarbon solvents such as xylene, toluene, and benzene; aliphatic hydrocarbon solvents such as heptane, hexane, and ligroin; halogenated hydrocarbon solvents such as trichloroethylene, perchloroethylene, and methylene chloride; ester solvents such as ethyl acetate and 1-propylene glycol methyl ether acetate; ether solvents such as tetrahydrofuran and diethyl ether; ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; alcohol solvents such as ethanol, isopropanol, and butanol; rubber volatile oils, silicone solvents, etc. Among these, ethyl acetate, 1-propylene glycol methyl ether acetate, tetrahydrofuran, and acetone are preferably used.

Component (D) may be used alone or in combination of two or more types as a mixed solvent, depending on the evaporation rate during application of the primer composition.

By incorporating component (D), the workability of the primer composition during application and drying can be adjusted. The amount of component (D) is not particularly limited, but is preferably 60% by mass or more of the entire primer composition, more preferably 80 to 95% by mass, and even more preferably 85 to 90% by mass. If it is within such a range, the coating film of the primer composition can be formed uniformly, and unevenness of the coating surface can be suppressed. Note that when component (A) etc. is added as a solution, the amount of component (D) refers to the total amount in the composition including the solvent in the solution.

(5) Component (E) The primer composition of the present invention may further contain an organosilicon compound represented by the following formula (3) as component (E).
(R ⁶ O) _c R ⁷ _d Si (3)

R ⁶ are each independently an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms for R ⁶ include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, and t-butyl, and are preferably a methyl group or an ethyl group.
^R7 's are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an acrylic group, a methacrylic group, or an epoxy group. Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms for ^R7 include the same monovalent hydrocarbon groups as those exemplified for ^R9 , with a methyl group and a phenyl group being preferred.
c is an integer of 1 to 4, preferably 3 or 4; d is an integer of 0 to 3, preferably 0 or 1; and c+d=4.

Examples of component (E) include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, etc. Among these, tetramethoxysilane and tetraethoxysilane are particularly preferred.

When component (E) is used, the amount of component is not particularly limited, but is preferably 1 to 20 mass% of the total composition, and more preferably 2 to 10 mass%.

[Other ingredients]
The primer composition of the present invention may further contain other optional components such as fluorescent materials, reinforcing fillers, dyes, pigments, heat resistance improvers, antioxidants, adhesion promoters, etc., within the scope of not impairing the object of the present invention.

[Method of manufacturing primer composition]
The primer composition of the present invention can be obtained, for example, by a method in which the above-mentioned components (A), (B), (C) and (D), and, if necessary, component (E) and other optional components, are uniformly mixed using a mixer.

[Adhesion method]
The primer composition of the present invention can be suitably used to improve the adhesion between an adherend and a silicone cured product.As a method for adhering an adherend and a silicone cured product using the primer composition of the present invention, for example, a method of supplying the primer composition of the present invention onto an adherend, disposing a curable silicone composition on the adherend to which the primer composition has been supplied, and curing the silicone composition can be adopted.

The primer composition of the present invention can be applied to the adherend by known methods such as brushing or spraying. After applying the primer composition to the adherend, it is air-dried for 5 minutes to 24 hours, preferably 10 minutes to 12 hours, and then a curable silicone composition is applied and the silicone composition is cured at room temperature (25°C) or under heat to bond the adherend to the cured silicone product. Alternatively, after air-drying, the composition may be heated to harden the coating, and then the curable silicone composition may be applied, and the adherend and cured silicone product may be bonded in the same manner as above.

The adherends used in the present invention include organic resins such as acrylic resins, phenolic resins, epoxy resins, polycarbonate resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polyamide resins, polyimide resins, and polypropylene resins, as well as various metals and glass, with polyimide resins being particularly preferred. Examples of polyimide resins include HJA-A4-100 (manufactured by Kitashin Co., Ltd.), Kapton 100H, and Kapton 100EN (all manufactured by Toray Industries, Inc.).

Examples of curable silicone compositions include addition curing type, peroxide curing type, and condensation curing type, but in the present invention, addition curing type silicone rubber compositions are preferred. As the addition curing type silicone rubber composition, a known composition can be used, and typically, a composition containing an organopolysiloxane having two or more alkenyl groups such as vinyl groups in one molecule, an organohydrogenpolysiloxane having two or more SiH groups in one molecule, and an addition reaction catalyst such as a platinum group metal catalyst can be used. Examples of addition curing type silicone rubber compositions include KE-106 and KER-2600 (manufactured by Shin-Etsu Chemical Co., Ltd.).

The present invention will be specifically explained below using synthesis examples, examples and comparative examples, but the present invention is not limited to these.

[Synthesis Example 1]
40 parts by mass of methyl methacrylate, 14 parts by mass of a SiH group-containing methacrylic acid ester represented by the following structural formula (7), 230 parts by mass of ethyl acetate, and 0.25 parts by mass of AIBN were heated and stirred at 90° C. for 6 hours to obtain an ethyl acetate solution containing a copolymer and having a nonvolatile content of 8% by mass (value at 105° C. for 3 hours).
The weight average molecular weight of the resulting copolymer was 95,000 in terms of standard polystyrene, measured using GPC (HLC-8320GPC, manufactured by Tosoh Corporation) with tetrahydrofuran as a developing solvent.

[Examples 1-1 to 1-7, Comparative Examples 1-1 and 1-2]
Primer compositions (I) to (VII) and comparative primer compositions (VIII) and (IX) were prepared by mixing the following components in the amounts shown in Table 1. The values in Table 1 represent parts by mass.

(A): 8% by weight ethyl acetate solution of the copolymer obtained in Synthesis Example 1

(B1): 3-ureidopropyltrimethoxysilane (KBM-585, manufactured by Shin-Etsu Chemical Co., Ltd.)

(B2): 3-aminopropyltriethoxysilane (KBE-903, manufactured by Shin-Etsu Chemical Co., Ltd.)

(B3): 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine (KBE-9103P, manufactured by Shin-Etsu Chemical Co., Ltd.)

(C): Tetra-n-butoxytitanium (D): Ethyl acetate (E): Tetraethoxysilane

[Examples 2-1 to 2-7, Comparative Examples 2-1 and 2-2]
The adhesion of the primer compositions (I) to (VII) and the comparative primer compositions (VIII) and (IX) obtained in Examples 1-1 to 1-7 and Comparative Examples 1-1 and 1-2 was evaluated by the following adhesion test. The results are shown in Table 2.

[Comparative Example 2-3]
The addition curable silicone primer composition (X) (PRIMER NO4 (carbon functional silane primer), manufactured by Shin-Etsu Chemical Co., Ltd.) was used as is to evaluate the adhesion by the following adhesion test. The results are shown in Table 2.

[Comparative Example 2-4]
Except for not using a primer composition, the adhesion was evaluated by the adhesion test described below. The results are shown in Table 2.

[Adhesion test]
Three types of polyimide sheets (HJA-A4-100, manufactured by Hokushin Co., Ltd.; Kapton 100H, manufactured by Toray Industries, Inc.; and Kapton 100EN, manufactured by Toray Industries, Inc.) cut into 30 mm x 30 mm pieces were used as adherends, and the primer composition was brushed onto the adherends and air-dried at 25°C for 15 minutes. An addition-curing silicone composition (KE-106, manufactured by Shin-Etsu Chemical Co., Ltd.) was dripped onto the adherends and cured to produce a laminated sheet.
The resultant laminate sheet was cut near the center of the cured silicone product on the laminate sheet with a cutter knife, and the state of the cured silicone product when the laminate sheet was folded was checked. The results were rated as follows: × if the cured silicone product peeled off when the laminate sheet was folded, △ if the cured silicone product did not peel off when the laminate sheet was folded but peeled off entirely when an attempt was made to peel it off by hand, and ◯ if the cured silicone product did not peel off when the laminate sheet was folded and cohesive failure occurred when an attempt was made to peel it off by hand.

As shown in Table 2, Examples 2-1 to 2-7 show significantly improved adhesion of the addition-cured silicone cured product to the polyimide sheet compared to Comparative Examples 2-1 to 2-3, which used a primer composition different from the primer composition of the present invention, and Comparative Example 2-4, which did not use a primer composition.

Claims (12)

A primer composition is provided on an adherend to bond the adherend to a cured product of the curable silicone composition when the curable silicone composition is placed on the adherend and cured, the primer composition comprising:
(A) an acrylic acid ester, a methacrylic acid ester, or a (co)polymer of both of these;
(B) an organosilicon compound represented by the following formula (1), an organosilicon compound represented by the following formula (2), or both of these:

(In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 4 carbon atoms, R ³ are each independently a divalent hydrocarbon group having 1 to 30 carbon atoms, R ⁴ are each independently an alkylene group or a carbonyl group having 1 to 6 carbon atoms, R ⁵ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, a is each independently 0 or 1, and b is an integer from 0 to 3.)
(C) one or more condensation catalysts selected from tetraalkoxytitanium, tetraalkoxyzirconium, tetraalkoxytin, trialkoxyaluminum, and partial hydrolysates thereof;
A primer composition for bonding an adherend to a cured silicone product, comprising (D) a solvent, and wherein the acrylic acid ester, methacrylic acid ester, or both of these constituting component (A) contain a compound having one or more SiH groups per molecule . 2. The primer composition according to claim 1, wherein the acrylic acid ester, the methacrylic acid ester, or both of them constituting the component (A) include one or more compounds selected from the compounds represented by the following formulas (4) to (6) :

(In the formulae, R8 ^are each independently a hydrogen atom or a methyl group, R9 ^are each independently a monovalent organic group, and R10 ^are each independently a divalent organic group. n is 0, 1 or 2. m is 0 or a positive integer, p is a positive integer, and q and r are positive integers. In formulae (5) and (6), the arrangement of the siloxane units in parentheses may be arbitrary.) 3. The primer composition according to claim 1, wherein component (B) comprises an organosilicon compound represented by the above formula (1), and R ⁴ is a carbonyl group. The primer composition according to any one of claims 1 to 3, further comprising (E) an organosilicon compound represented by the following formula (3):
(R ⁶ O) _c R ⁷ _d Si (3)
(In the formula, R ⁶ 's are each independently an alkyl group having 1 to 4 carbon atoms, R ⁷ 's are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen atom, an acrylic group, a methacrylic group, or an epoxy group, c is an integer of 1 to 4, d is an integer of 0 to 3, and c+d=4.) The primer composition according to any one of claims 1 to 4, wherein the adherend is a polyimide resin. 6. The primer composition according to any one of claims 1 to 5, wherein the curable silicone composition is an addition-curable silicone composition. A step of supplying the primer composition according to any one of claims 1 to 6 onto an adherend;
a step of applying a curable silicone composition to the adherend on which the primer composition has been applied, and then curing the silicone composition. 8. The bonding method according to claim 7 , wherein the adherend is made of a polyimide resin. 9. The bonding method according to claim 7, wherein the curable silicone composition is an addition-curable silicone composition. A laminate comprising an adherend and a cured layer of the curable silicone composition formed on the adherend via a coating of the primer composition according to any one of claims 1 to 6. 11. The laminate according to claim 10, wherein the adherend is a polyimide resin. 12. The laminate according to claim 10, wherein the curable silicone composition is an addition-curable silicone composition.