JP5438407B2 - Low dielectric resin composition - Google Patents

Description

  The present invention relates to a low dielectric resin composition, a low dielectric film, a low dielectric resin composition, a method for producing a low dielectric film, and a coating agent for a low dielectric film.

In recent years, electronic devices such as LSIs used for CPUs and memories have become more and more sophisticated, and the operating frequency has been increased and the size of the device has been reduced. Issues such as an increase in transmission loss and an increase in delay time due to miniaturization of wiring are expanding.
In order to solve these problems, development of an insulating material having a low dielectric constant and a low dielectric loss tangent used for a multilayer wiring structure of an electronic circuit is required. In order to reduce the dielectric constant of the interlayer insulating film, studies have been made to introduce voids inside the film. However, if non-uniformly sized voids are introduced to reduce the dielectric constant, the film strength will decrease. There's a problem.

Patent Document 1 discloses a mesoporous silica film having a dielectric constant of 2 to 3 by preparing a film-forming liquid composed of a ceramic precursor, a catalyst, a surfactant, and a solvent, and removing the solvent on the substrate. A method for producing a ceramic film is disclosed.
Patent Document 2 discloses a low dielectric constant film composed of a porous body of silicon oxide containing an organic group, wherein the silicon oxide has a carbon-silicon bond in which at least a part of silicon atoms are at two or more positions of the organic group. A low dielectric constant film is disclosed in which the porous body is a mesoporous body having a central pore diameter of 1 to 30 nm.
However, Patent Documents 1 and 2 have a problem that they are not versatile because a baking process is required to remove the surfactant used in film formation, and the types of substrates are limited.

Patent Document 3 discloses that a thin film is formed by applying a solution containing fine particles having a bond between silicon atoms and oxygen atoms and having pores, a resin, and a solvent to a substrate, and then forming the substrate. A method of forming a low dielectric constant insulating film by heating is disclosed.
Patent Document 4 discloses that in a low dielectric resin composition containing hollow particles and a thermosetting resin, the hollow particles have an average porosity of 30 to 80% by volume and an average particle size of 0.1 to 20 μm. A low dielectric resin composition that can reduce the dielectric constant and dielectric loss tangent using silica particles, and a prepreg that is impregnated into a base material and heat-dried are disclosed.
However, Patent Documents 3 and 4 are not satisfactory in terms of the dielectric constant and dielectric loss tangent of the film.

JP 2001-226171 A JP 2003-86676 A JP 2005-167266 A JP 2008-031409 A

  The present invention relates to a low dielectric resin composition having a sufficiently low dielectric constant and dielectric loss tangent, a low dielectric film comprising the low dielectric resin composition, a method for producing the low dielectric resin composition and the low dielectric film, and a low dielectric film. It is an object to provide a coating agent.

The present inventors have found that the above problem can be solved by dispersing hollow silica particles having a specific structure in a matrix resin.
That is, the present invention provides the following [1] to [5].
[1] Hollow silica having an average particle diameter of 0.05 to 1 μm, 80% by mass or more of the whole particles having an average particle diameter of ± 30% or less and a BET specific surface area of less than 30 m ² / g A low dielectric resin composition in which particles are dispersed in a matrix resin.
[2] A low dielectric film comprising the low dielectric resin composition of [1].
[3] The method for producing a low dielectric resin composition according to [1], including the following steps (I) to (III).
Step (I): Step of preparing hollow silica particles (A) containing air inside the particles, or core-shell type silica particles (B) enclosing a material that disappears by firing to form a hollow portion Step (II): Step of preparing hollow silica particles (C) by firing the hollow silica particles (A) or the core-shell type silica particles (B) obtained in step (I) at a temperature exceeding 950 ° C. Step (III): The step [4] of preparing a dispersion in which the hollow silica particles (C) obtained in the step (II) are dispersed in a matrix resin forming material. The steps (I) to (III) and the following step (IV) are performed. A method for producing a low dielectric film.
Step (IV): Step of solidifying after applying the dispersion obtained in Step (III) on the substrate [5] Average particle diameter is 0.05 to 1 μm, and 80% by mass or more of the whole particles are average particles A coating agent for a low dielectric film, in which hollow silica particles having a particle diameter of ± 30% or less and a BET specific surface area of less than 30 m ² / g are dispersed in a matrix resin forming material.

  According to the present invention, a low dielectric resin composition having a sufficiently low dielectric constant and dielectric loss tangent, a low dielectric film comprising the low dielectric resin composition, a method for producing the low dielectric resin composition and the low dielectric film, and a low dielectric A coating agent for a film can be provided.

[Low dielectric resin composition and low dielectric film]
The low dielectric resin composition of the present invention and the film thereof have an average particle diameter of 0.05 to 1 μm, 80% by mass or more of the whole particles have an average particle diameter within ± 30%, and a BET ratio. Hollow silica particles having a surface area of less than 30 m ² / g are characterized by being dispersed in a matrix resin, and the low dielectric film of the present invention is characterized by comprising the low dielectric resin composition.
In the low dielectric resin composition and the low dielectric film of the present invention, by containing the hollow silica particles having the specific structure dispersed therein, the dielectric constant and dielectric loss tangent are reduced. This is presumably because the matrix resin cannot be present in the hollow part of the hollow silica particles, so that the porosity is not lowered, and the dielectric constant and dielectric loss tangent of the molded body and film made of the resin composition are lowered.
For example, the dielectric constant of the low dielectric film is preferably 3.5 or less, more preferably 3.2 or less, still more preferably 3.0 or less, and particularly preferably 1.5 to 3.0 at a frequency of 1 MHz. The dielectric constant can be measured by an ordinary method such as an electrode contact method or an electrode non-contact method using an LCR meter or an impedance analyzer.
Further, the dielectric loss tangent of the low dielectric film is preferably 0.01 or less, more preferably 0.0095 or less, and still more preferably 0.009 or less, under the measurement conditions described in the examples.
The thickness of the low dielectric film is not particularly limited, but is preferably 10 to 700 μm, more preferably 30 to 500 μm, and still more preferably 50 to 300 μm from the viewpoints of production and performance of a low dielectric constant.

[Hollow silica particles]
In the present invention, the average particle size is 0.05 to 1 μm, 80% by mass or more of the total particles have a particle size within an average particle size ± 30%, and the BET specific surface area is less than 30 m ² / g. Hollow silica particles (hereinafter also simply referred to as “hollow silica particles” or “hollow silica particles (C)”) are used.
The average particle diameter of the hollow silica particles can be adjusted as appropriate in consideration of the application and the like, but the number average particle diameter is preferably 0.1 to 1 μm, more preferably 0.15 to 0.9 μm, still more preferably 0.8. 2 to 0.8 μm. The hollow silica particles preferably have a particle size of 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more of the average particle size within ± 30%. It is desirable to have a group of particles having a very uniform particle diameter.
Further, the BET specific surface area of the hollow silica particles is preferably 25 m ² / g or less, more preferably 20 m ² / g or less, and more preferably 18 m ² / g or less, from the viewpoint of stable retention of inclusions. preferable.

The hollow silica particles preferably do not show a peak at a diffraction angle (2θ) corresponding to a range where the crystal lattice spacing (d) is less than 1 nm in powder X-ray diffraction (XRD) measurement.
Further, it is preferable that the hollow silica particles do not substantially exhibit a pore distribution of 1 nm or more in the pore diameter distribution. The average thickness of the outer shell portion is preferably thin as long as the hollow silica particles can maintain the strength as a carrier, and the average diameter (average volume) of the hollow portion is preferably larger from the viewpoint of increasing the porosity. From these viewpoints, the average thickness of the outer shell is usually 0.5 to 500 nm, preferably 2 to 400 nm, more preferably 3 to 300 nm.
The ratio of [average thickness of outer shell part / average particle diameter of hollow silica particles] is usually 0.01 to 0.9, preferably 0.05 to 0.8, more preferably 0.1 to 0.7. is there.
The average particle diameter of the hollow silica particles and the average thickness of the outer portion can be appropriately adjusted depending on the production conditions of the hollow silica particles (A) as a raw material, the particle diameter of the hollow part forming material, the firing conditions, and the like.

[Production Method of Low Dielectric Resin Composition]
Although there is no restriction | limiting in particular in the manufacturing method of the low dielectric resin composition of this invention, According to the method containing following process (I)-(III), it can manufacture efficiently.
Step (I): a hollow silica particle (A) containing air inside the particle (hereinafter also simply referred to as “hollow silica particle (A)”), or a core shell containing a material that disappears by firing to form a hollow part Step of Preparing Type Silica Particles (B) (hereinafter Also referred to as “Core Shell Type Silica Particles (B)”) Step (II): Hollow silica particles (A) or core shell type silica particles obtained in step (I) ( Step of preparing hollow silica particles (C) by baking B) at a temperature exceeding 950 ° C. Step (III): Dispersing the hollow silica particles (C) obtained in Step (II) in the matrix resin forming material Steps for Preparing the Dispersed Liquid The details of steps (I) to (III) and the components used therein will be described below.

Process (I)
Step (I) is a step of preparing hollow silica particles (A) or core-shell type silica particles (B). The method is not particularly limited as long as it is a method capable of producing the hollow silica particles (A) or the core-shell type silica particles (B), but a method including the following steps A to D is more preferable.
Step A: 0.1 to 50 g / L of the polymer particles (a-1) or 0.1 to 100 mmol / L of the hydrophobic organic compound (a-2), and the following general formulas (1) and (2) And 0.1 to 100 mmol / L of one or more (b) selected from quaternary ammonium salts represented by the formula (1)) and 0.1 to 100 mmol of silica source (c) that produces a silanol compound by hydrolysis. Step of preparing an aqueous solution containing / L.
[R ¹ (CH ₃ ) ₃ N] ⁺ X ⁻ (1)
[R ¹ R ² (CH ₃ ) ₂ N] ⁺ X ⁻ (2)
(In the formula, R ¹ and R ² each independently represents a linear or branched alkyl group having 4 to 22 carbon atoms, and X represents a monovalent anion.)
Step B: The aqueous solution obtained in Step A is stirred at a temperature of 10 to 100 ° C., has an outer shell composed of silica, and has polymer particles (a-1) or a hydrophobic organic compound (a -2) Step of preparing an aqueous dispersion of proto-core-shell type silica particles Step C: Step of separating core-shell type silica particles (B) from the aqueous dispersion obtained in Step B Step D: Obtained in Step C Baked core-shell type silica particles (B) to obtain hollow silica particles (A)

Hereinafter, steps A to D will be described.
[Step A]
(Polymer particles (a-1))
As the polymer particles (a-1) used in the step A, particles of one or more polymers selected from a cationic polymer, a nonionic polymer and an amphoteric polymer are preferable, and a substantially water-insoluble polymer is preferable.
The average particle size of the polymer particles used in Steps A to D is preferably 0 for the purpose of obtaining a compound having a fine particle size and a uniform particle size distribution, which is a feature of the hollow silica particles of the present invention. It is desirable that the thickness is 0.02 μm to 1 μm, more preferably 0.05 μm to 0.9 μm, still more preferably 0.1 μm to 0.8 μm, and particularly preferably 0.12 μm to 0.7 μm. The polymer particles preferably have a particle diameter of 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more of the average particle size within ± 30% of the whole particle. It is desirable to have a group of particles having a very uniform particle diameter.

(Cationic polymer)
The cationic polymer is preferably a polymer that can be dispersed as a polymer emulsion in a medium containing a continuous phase in an aqueous system in the presence of a cationic surfactant, and is cationic in the presence of a cationic surfactant. Those obtained by emulsion polymerization of a monomer mixture, particularly a monomer mixture containing an ethylenically unsaturated monomer having a cationic group, by a known method are preferred.
Examples of the cationic monomer include an acid neutralized product of a monomer having an amino group, or a quaternary ammonium salt obtained by quaternizing the monomer with a quaternizing agent.
As a specific example of the cationic monomer, a (meth) acrylate having a dialkylamino group or a trialkylammonium group is more preferable, and a (meth) acrylate having a dialkylamino group or a trialkylammonium group is most preferable.
In the present specification, (meth) acrylate means acrylate, methacrylate, or both.

  The cationic polymer contains a structural unit derived from the cationic monomer, but in addition to the cationic monomer structural unit, it is derived from a hydrophobic monomer such as an alkyl (meth) acrylate or an aromatic ring-containing monomer. It is more preferable to contain a structural unit. Preferable examples thereof include styrenic monomers such as alkyl (meth) acrylate, styrene or 2-methylstyrene having an alkyl group having 1 to 30 carbon atoms, preferably 3 to 22 carbon atoms, more preferably 3 to 18 carbon atoms. , Aryl esters of (meth) acrylic acid such as benzyl (meth) acrylate, aromatic group-containing vinyl monomers having 6 to 22 carbon atoms, or vinyl acetate. Of these, alkyl (meth) acrylate and styrene are most preferred.

The hydrophobic monomer means a polymerizable organic compound that has low solubility in water and forms a phase separation with water. Examples of the hydrophobic monomer include compounds having a LogP value of 0 or more, preferably 0.5 or more, and 25 or less. Here, LogP means a logarithmic value of a 1-octanol / water partition coefficient of a chemical substance, and is a numerical value calculated by a fragment approach by SRC's LOGKOW / KOWWIN Program. Specifically, the chemical structure of a chemical substance is decomposed into its constituent components, and the hydrophobic fragment constants of each fragment are integrated (Meylan, WM and PH Howard. 1995. Atom / fragment contribution method for octanol-water partition coefficients. See J. Pharm. Sci. 84: 83-92).
The cationic monomer constituting unit constituting the cationic polymer may be a small amount, and most constituting the cationic polymer may be constituted by a constituent unit derived from the hydrophobic monomer. The total amount of the cationic monomer constituent unit and the constituent unit derived from the hydrophobic monomer in the cationic polymer is 70 to 100% by mass, more preferably 80 to 100% by mass, and particularly preferably 95 to 100% by mass. In particular, the weight ratio of [(constituent unit derived from cationic monomer) / (constituent unit derived from hydrophobic monomer)] is preferably 0.001 to 0.5, more preferably 0.002 from the viewpoint of particle formation. It is -0.3, Most preferably, it is 0.003-0.1.

(Nonionic polymer)
Nonionic polymer means a polymer that has no charge in aqueous solution. The nonionic polymer is a polymer derived from a monomer having no charge, that is, a nonionic monomer, and can be obtained by polymerizing a nonionic monomer by a known emulsion polymerization method, non-emulsifier polymerization method or the like.
Nonionic monomers include the hydrophobic monomers (paragraphs [0015] and [0016]) mentioned in the description of the cationic polymer. Preferable examples thereof include one or more selected from alkyl (meth) acrylates having an alkyl group having 1 to 30 carbon atoms, preferably 3 to 22 carbon atoms, more preferably 3 to 18 carbon atoms, vinyl acetate, and styrene. Can be mentioned.
Specific examples of nonionic polymers include polystyrene, ethyl acrylate / ethyl methacrylate copolymer, ethyl acrylate / methyl methacrylate copolymer, octyl acrylate / styrene copolymer, butyl acrylate / vinyl acetate copolymer, methyl methacrylate / butyl. Examples thereof include acrylate / octyl acrylate copolymers, vinyl acetate / styrene copolymers, vinyl pyrrolidone / styrene copolymers, butyl acrylate, and polystyrene acrylate resins.

Among the cationic polymer, the nonionic polymer and the amphoteric polymer, the cationic polymer and the nonionic polymer are preferable, and the cationic polymer is more preferable from the viewpoint of easy formation of the hollow silica particles (A).
For the production of the hollow silica particles (A), a polymer that does not substantially dissolve in water is used. For this purpose, a method for increasing the polymerization ratio of a hydrophobic monomer, a method for crosslinking, and the like can be employed.
Preferred examples of such a polymer include a copolymer of a hydrophobic monomer selected from alkyl (meth) acrylate and styrene and a (meth) acrylate having a cationic group, and one or more hydrophobic properties selected from alkyl (meth) acrylate and styrene. Mention may be made of nonionic polymers composed of monomers.
Said polymer can be used individually or in mixture of 2 or more types.
The shape and form of the polymer particles are not particularly limited, and the size of the particles can be changed or the particles can be formed into a true spherical shape, an egg shape, or the like according to the purpose of use of the composite silica particles. By changing the size and particle size distribution of the polymer particles, the particle size of the hollow silica particles (A) and the size of the hollow part can be appropriately adjusted.

(Hydrophobic organic compound (a-2))
In the present invention, the hydrophobic organic compound (a-2) means a compound that has low solubility in water and forms a phase separation with water. Preferably, the compound is dispersible in the presence of the quaternary ammonium salt. Examples of such hydrophobic organic compounds include compounds having a LogP value of 1 or more, preferably 2 to 25.
Examples of the hydrophobic organic compound (a-2) include oils such as hydrocarbon compounds, ester compounds, fatty acids having 6 to 22 carbon atoms, alcohols having 6 to 22 carbon atoms, and silicone oil, fragrances, agricultural chemicals, pharmaceuticals, and the like. The various base materials of these can be mentioned.
When the hydrophobic organic compound (a-2) is used, the particle size of the hollow silica particles (A) and the size of the hollow part are affected by the size of the droplets of the hydrophobic organic compound. It can be appropriately adjusted depending on the melting point of the organic compound, the reaction temperature, the stirring speed, the surfactant used, and the like.

(Quaternary ammonium salt (b))
The quaternary ammonium salt (b) is used for forming mesopores and dispersing the polymer particles (a-1) or the hydrophobic organic compound (a-2).
R ¹ and R ² in the general formulas (1) and (2) are linear or branched alkyl groups having 4 to 22 carbon atoms, preferably 6 to 18 carbon atoms, and more preferably 8 to 16 carbon atoms. It is. Examples of the alkyl group having 4 to 22 carbon atoms include various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, and various hexadecyl groups. , Various octadecyl groups, various eicosyl groups, and the like.
X in the general formulas (1) and (2) is preferably one selected from monovalent anions such as halogen ions, hydroxide ions, nitrate ions, and sulfate ions from the viewpoint of obtaining high crystallinity. That's it. X is more preferably a halogen ion, still more preferably a chlorine ion or a bromine ion, and particularly preferably a bromine ion.

Examples of the alkyltrimethylammonium salt represented by the general formula (1) include butyltrimethylammonium chloride, hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethyl Ammonium chloride, stearyltrimethylammonium chloride, butyltrimethylammonium bromide, hexyltrimethylammonium bromide, octyltrimethylammonium bromide, decyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide Bromide, stearyl trimethyl ammonium bromide, and the like.
Examples of the dialkyldimethylammonium salt represented by the general formula (2) include dibutyldimethylammonium chloride, dihexyldimethylammonium chloride, dioctyldimethylammonium chloride, dihexyldimethylammonium bromide, dioctyldimethylammonium bromide, didodecyldimethylammonium bromide, ditetradecyl. Examples thereof include dimethylammonium bromide.
Among these quaternary ammonium salts (b), from the viewpoint of forming regular mesopores, alkyltrimethylammonium salts represented by the general formula (1) are particularly preferred, and alkyltrimethylammonium bromide or alkyltrimethyl Ammonium chloride is more preferred, and dodecyltrimethylammonium bromide or dodecyltrimethylammonium chloride is particularly preferred.

(Silica source (c))
A silica source (c) produces | generates a silanol compound by hydrolysis of alkoxysilane etc., and can mention the compound shown by following General formula (3)-(7).
SiY ₄ (3)
R ³ SiY ₃ (4)
R ³ ₂ SiY ₂ (5)
R ³ ₃ SiY (6)
Y ₃ Si—R ⁴ —SiY ₃ (7)
(In the formula, each R ³ independently represents an organic group in which a carbon atom is directly bonded to a silicon atom, R ⁴ represents a hydrocarbon group or a phenylene group having 1 to 4 carbon atoms, and Y represents A monovalent hydrolyzable group that becomes a hydroxy group by hydrolysis.)
More preferably, in the general formulas (3) to (7), each R ³ is independently a hydrocarbon group having 1 to 22 carbon atoms in which a part of hydrogen atoms may be substituted with fluorine atoms, Specifically, it is an alkyl group, a phenyl group, or a benzyl group having 1 to 22 carbon atoms, preferably 4 to 18 carbon atoms, more preferably 6 to 18 carbon atoms, and particularly preferably 8 to 16 carbon atoms, and R ⁴ Is an alkanediyl group having 1 to 4 carbon atoms (methylene group, ethylene group, trimethylene group, propane-1,2-diyl group, tetramethylene group, etc.) or phenylene group, and Y is more preferably 1 to 22 carbon atoms. Is a C1-C8, particularly preferably C1-C4 alkoxy group or a halogen group excluding fluorine.

Preferable examples of the silica source (c) include the following compounds.
-The silane compound in which Y is a C1-C3 alkoxy group or a halogen group except a fluorine in General formula (3).
In general formula (4) or (5), Y is an alkoxy group having 1 to 3 carbon atoms or a halogen group excluding fluorine, and R ³ is a phenyl group, a benzyl group, or a part of a hydrogen atom Is a trialkoxysilane or dialkoxysilane, which is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, substituted with a fluorine atom.
In General Formula (6), Y is an alkoxy group having 1 to 3 carbon atoms or a halogen group excluding fluorine, and R ³ is a phenyl group, a benzyl group, or a hydrogen atom partially substituted with a fluorine atom. Monoalkoxysilane which is a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.
A compound in which Y is a methoxy group and R ⁴ is a methylene group, an ethylene group or a phenylene group in the general formula (7).
Among these, tetramethoxysilane, tetraethoxysilane, phenyltriethoxysilane, and 1,1,1-trifluoropropyltriethoxysilane are particularly preferable.

Polymer particles (a-1) or hydrophobic organic compound (a-2) in the aqueous solution in step A (hereinafter, both are also collectively referred to as “component (a)”), quaternary ammonium salt (b), And the content of the silica source (c) is as follows.
The content of the component (a-1) is preferably 0.1 to 50 g / L, more preferably 0.3 to 40 g / L, and particularly preferably 0.5 to 30 g / L.
The content of the component (a-2) is 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, and particularly preferably 5 to 80 mmol / L.
The content of component (b) is preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, particularly preferably 5 to 80 mmol / L, and the content of component (c) is And preferably 0.1 to 100 mmol / L, more preferably 1 to 100 mmol / L, and particularly preferably 5 to 80 mmol / L.
There is no restriction | limiting in particular in the order which contains (a)-(c) component. For example, (i) the suspension of the component (a), the component (b) and the component (c) are added in this order while stirring the aqueous solution, (ii) the suspension of the component (a) while stirring the aqueous solution, (B) Component and (c) component can be added simultaneously, (iii) Suspension of (a) component, (b) Component, (c) Stirring after addition of component, etc. can be employed. However, among these, the method (i) is preferable.
The aqueous solution containing the components (a) to (c) may contain other components such as an organic compound such as methanol and an inorganic compound as long as the formation of protocore-shell particles is not inhibited. As described above, when it is desired to carry other elements other than silica and organic groups, metal raw materials such as alkoxy salts and halide salts containing these metals can be added during or after production.

[Step B]
Step B is a step of preparing an aqueous dispersion of protocore-shell type silica particles. The aqueous solution obtained in Step A is stirred for a predetermined time at a temperature of 10 to 100 ° C., preferably 10 to 80 ° C., and then allowed to stand to leave the polymer particles (a-1) or the hydrophobic organic compound (a-2). A proto-core shell in which mesopores are formed on the surface of quaternary ammonium salt (b) and silica source (c), and polymer particles (a-1) or hydrophobic organic compound (a-2) are included inside Type silica particles can be deposited. Although the stirring treatment time varies depending on the temperature, protocore-shell type silica particles are usually formed at 10 to 80 ° C. for 0.1 to 24 hours. The mesopores of the protocore-shell type silica particles obtained at this time are in a state where the surfactant used in the production is clogged.
The obtained protocore-shell type silica particles are obtained in a state suspended in water. Depending on the application, it can be used as it is, but preferably the protocore-shell type silica particles are used separately. As a separation method, a filtration method, a centrifugal separation method, or the like can be employed.
When the protocore-shell type silica particles obtained in step B contain a cationic surfactant or the like, the cationic surfactant or the like can be removed by contacting the acidic solution once or a plurality of times. Examples of the acidic solution to be used include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid; organic acids such as acetic acid and citric acid; liquids obtained by adding a cation exchange resin or the like to water or ethanol. Hydrochloric acid is particularly preferable. The pH is usually adjusted to 1.5 to 5.0.
The particles from which the surfactant has been removed from the pores by the above method have a mesopore structure on the surface, and have a high BET specific surface area. Polymer particles (a-1) or hydrophobic organic compounds (a-2) Is a proto-core-shell type silica particle.

[Steps C and D]
Step C is a step of separating the core-shell type silica particles (B) from the aqueous dispersion obtained in Step B. Step D is a step of firing the core-shell type silica particles (B) obtained in Step C. This is a step of obtaining hollow silica particles (A).
In step C, the core-shell type silica particles (B) can be separated from the aqueous dispersion, and contacted with an acidic aqueous solution, washed with water, and dried as necessary. Moreover, after processing at high temperature, in process D, it is preferably fired in an electric furnace or the like at 350 to 800 ° C., more preferably at 450 to 700 ° C. for 1 to 10 hours, and the inner polymer (a-1) or hydrophobic The organic compound (a-2) is removed. Although the basic structure of the outer shell part of the obtained hollow silica particles (A) is not changed, the inner polymer (a-1) or the hydrophobic organic compound (a-2) is removed by calcination.
In the present invention, since the core-shell type silica particles containing the polymer (a-1) or the hydrophobic organic compound (a-2) are fired, the shape and form of the polymer particles (a-1) to be included are particularly desired. By controlling in advance to the state, hollow silica particles (A) having a desired shape and form can be easily produced. For example, by firing core-shell type silica particles having a true spherical polymer inside, hollow silica particles (A) having an internal hollow shape and a true spherical shape can be produced.

Of the hollow silica particles (A) and the core-shell type silica particles (B) obtained as described above, in the powder X-ray diffraction measurement, the diffraction angle (2θ corresponding to the range of the surface spacing (d) of 1 nm to 12 nm. ) Is preferred.
The average pore diameter of the mesopore structure of the hollow silica particles (A) obtained in the step (I) is preferably 1 to 8 nm, more preferably 1 to 5 nm, and the mesopore diameter is determined by the hollow silica particles (A 70 mass% or more, preferably 75 mass% or more, more preferably 80 mass% or more of the average pore diameter is within ± 30 mass%.
The BET specific surface area of the hollow silica particles (A) is preferably 100 to 1500 m ² / g, more preferably 200 to 1500 m ² / g, and still more preferably 300 to 1500 m ² / g.
The average particle diameter of the hollow silica particles (A) is preferably 0.05 to 2 μm, more preferably 0.05 to 1.5 μm, still more preferably 0.1 to 1.2 μm. The hollow silica particles are preferably 80% by mass or more of the total primary particles, more preferably 85% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more of primary particles having an average particle size within ± 30%. It is desirable to have a group of particles having a diameter and a very uniform particle diameter.
The average thickness of the outer shell part (mesoporous silica part) is preferably as thin as the hollow silica particles can maintain the strength as a carrier, and the average diameter (average volume) of the hollow part is from the viewpoint of retaining a large amount of inclusions. Larger is preferable. From these viewpoints, the average thickness of the outer shell is usually 0.5 to 500 nm, preferably 2 to 400 nm, more preferably 3 to 300 nm.
The ratio of [average thickness of outer shell portion / average particle diameter of hollow silica particles] is usually 0.01 to 0.9, preferably 0.05 to 0.8, more preferably 0.1 to 0. 7.
The average particle diameter, average outer shell thickness, BET specific surface area, average pore diameter, and powder X-ray diffraction (XRD) pattern of the hollow silica particles (A) can be measured by the methods described in the examples.

Process (II)
Step (II) is a step of preparing hollow silica particles (C) by firing the hollow silica particles (A) or the core-shell type silica particles (B) obtained in step (I) at a temperature exceeding 950 ° C. is there.
The firing temperature is such that the pores are appropriately baked, the average particle size is 0.05 to 1 μm, 80% by mass or more of the whole particles is within the average particle size ± 30%, and the BET specific surface area is less than 30 m ² / g From this viewpoint, the temperature is preferably 960 to 1500 ° C, more preferably 970 to 1300 ° C, and further preferably 980 to 1200 ° C.
Firing can be performed using an electric furnace or the like, and the firing time varies depending on the firing temperature and the like, but is usually 0.5 to 100 hours, preferably 1 to 80 hours.
In the present invention, the hollow silica particles (A) are produced once in the step (I), and then fired at a temperature exceeding 950 ° C. in the step (II) to obtain the hollow silica particles obtained in the step (I). Without changing the basic configuration of (A), hollow silica particles (C) having a reduced average particle diameter and BET specific surface area can be obtained. Further, the hollow shell particles (C) may be obtained by directly firing the core-shell type silica particles (B) obtained in the step (I) at a temperature exceeding 950 ° C. In the present invention, it is more preferred to obtain hollow silica particles (C) having a small BET specific surface area by first producing hollow silica particles (A) and then further firing.

Process (III)
Step (III) is a step of preparing a dispersion in which the hollow silica particles (C) obtained in step (II) are dispersed in a matrix resin forming material.
(Matrix resin)
There is no restriction | limiting in particular in the matrix resin which can be used by this invention. Examples thereof include a thermosetting resin that is cured by heating, a photocurable resin that is cured by irradiation with light such as ultraviolet rays, and a thermoplastic resin.
Examples of the thermosetting resin and the photocurable resin include epoxy resins, unsaturated polyester resins, phenol resins, urea / melamine resins, polyurethane resins, silicone resins, diallyl phthalate resins, and the like.
Examples of the epoxy resin include various epoxy resins such as glycidyl ether type, glycidyl ester type, glycidyl amine type, cycloaliphatic type, novolak type, naphthalene type, dicyclopentadiene type such as bisphenol A type epoxy resin.
Unsaturated polyester resins include orthophthalic acid, isophthalic acid, terephthalic acid, alicyclic unsaturated acid, fatty saturated acid, bisphenol, halogenated acid, and halogenated bisphenol. A polyester resin is mentioned.
Examples of the phenolic resin include phenolic resins such as a resol type and a novolac type.

Thermoplastic resins include polyolefin resin, polyvinyl chloride resin, vinylidene chloride resin, polystyrene resin, acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, styrene block copolymer resin, methacrylic resin, polyvinyl Alcohol resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, thermoplastic polyester resin, fluorine resin, polyphenylene sulfide resin, polysulfone resin, amorphous arylate resin, polyetherimide resin, polyethersulfone resin, polyetherketone Examples thereof include resins, liquid crystal polymer resins, polyamideimide resins, thermoplastic polyimide resins, and syndiopolystyrene resins.
Polyolefin resins include polyethylene resin, polypropylene resin, α-olefin copolymer resin, polybutene-1 resin, polymethylpentene resin, cyclic olefin polymer resin, ethylene / vinyl acetate copolymer resin, ethylene / methacrylic acid copolymer. Examples thereof include resins and ionomers.
Examples of the polyamide resin include nylon 6, nylon 66, nylon 11, nylon 12, and the like.
Examples of the thermoplastic polyester resin include polyethylene terephthalate resin, polybutylene terephthalate resin, polybutylene succinate resin, and polylactic acid resin.
Fluororesin includes polytetrafluoroethylene resin, perfluoroalkoxyalkane resin, perfluoroethylene propene copolymer resin, ethylene / tetrafluoroethylene copolymer resin, polyvinylidene fluoride resin, polychlorotrifluoroethylene resin, ethylene / chlorotrifluoroethylene Examples thereof include a copolymer resin, a tetrafluoroethylene / perfluorodioxole copolymer resin, and a polyvinyl fluoride resin.

Among the above matrix resins, thermosetting resins and photocurable resins are preferable, and from the viewpoint of low dielectric constant, epoxy resins and phenol resins are more preferable, and epoxy resins are particularly preferable. The matrix resin can be used alone or in combination of two or more.
The weight average molecular weight of the matrix resin is preferably 200 to 100,000, more preferably 500 to 10,000.
The content of the matrix resin is preferably 30 to 98% by mass, more preferably 50 to 95% by mass, and still more preferably 60 to 90% by mass, from the viewpoint of expressing the performance of the low dielectric film.

[Low Dielectric Film Manufacturing Method and Low Dielectric Film Coating Agent]
The method for producing a low dielectric film according to the present invention includes the steps (I) to (III) and the following step (IV).
Step (IV): Step of solidifying after applying the dispersion obtained in step (III) on the substrate. “Matrix resin forming material” has fluidity and solidifies under certain conditions. It means a material for forming a matrix resin. For example, a liquid resin material before curing of a thermosetting resin or a photocurable resin, a thermoplastic resin material that is made fluid by heating, a thermoplastic resin material dissolved in a volatile solvent, A pre-polymerization material or a polymerization intermediate material of a thermoplastic resin is included.

In the low dielectric film of the present invention, when the matrix resin is a thermosetting resin or a photocurable resin, a liquid resin material before curing is used as a matrix resin forming material, and after hollow silica particles (C) are dispersed therein, It can be obtained by a method of curing and solidifying the matrix resin forming material.
Further, when the matrix resin is a thermoplastic resin, (1) a method of dispersing the hollow silica particles (C) in the matrix resin forming material fluidized by heating and then cooling and solidifying, (2) volatility A method in which hollow silica particles (C) are dispersed in a matrix resin forming material dissolved in a solvent, and then the solvent is volatilized and solidified. (3) A hollow silica is applied to the matrix resin forming material that is a monomer or an intermediate polymer. A method of dispersing and solidifying the particles (C); and (4) dispersing the hollow silica particles (C) in the matrix resin forming material during the polymerization and before solidification to complete the polymerization. Thus, the low dielectric film of the present invention can be obtained by a method of solidifying and the like.

The coating agent for low dielectric film of the present invention has an average particle diameter of 0.05 to 1 μm, 80% by mass or more of the whole particles have an average particle diameter within ± 30%, and a BET specific surface area of 30 m. Hollow silica particles that are less than ² / g are dispersed in a matrix resin-forming material. In this low dielectric film coating agent, hollow silica particles are dispersed in a flowable matrix resin forming material, and this is used as a dispersion liquid in the step (III) in the step (IV). A low dielectric film can be formed by solidifying after coating.
There is no particular limitation on a substrate using a silicon wafer, Si ₃ N _4, a metal plate (Al, Pt, etc.), a glass plate and the like, are also included as a very thin metal foil.
The coating agent (dispersion) can be applied by conventional methods such as spin coating, dip coating, bar coating, spraying, and gravure coating.
Solidification after applying the coating agent can be performed by drying or heating, or by light irradiation.
The drying or heating varies depending on the composition and material of the film structure and the use of the film, but from the viewpoint of productivity and ease of production, it is preferably room temperature to 300 ° C, more preferably 50 to 200 ° C, and still more preferably 70 to 150. It can be carried out by holding at a temperature of ° C., preferably for 0.5 to 20 days, more preferably for 1 to 10 days.
In order to reduce the dielectric constant of the film, it is considered important to prevent the matrix resin from entering into the mesopores and the hollow portion of the hollow silica particles and to have as many voids as possible. From this point of view, it is preferable that the matrix resin-forming material is solidified before entering into the mesopores and the hollow portion. Therefore, after dispersing the hollow silica particles in the matrix resin-forming material having high viscosity, it is applied and solidified as soon as possible. It is preferable to do.

The viscosity of the matrix resin forming material is preferably from 0.1 to 20 Pa · s, more preferably from 0.2 to 18 Pa · s, and further preferably from 1 to 16 Pa · s, from the viewpoint of performance expression of the low dielectric film and ease of dispersion. 2 to 15 Pa · s is preferable. The viscosity can be measured by the method described in the examples.
The mixing time of the matrix resin forming material and the hollow silica particles is preferably as short as possible within the range in which the silica particles are uniformly dispersed, preferably 0.1 to 60 minutes, more preferably 0.5 to 10 minutes. 0.5 to 2 minutes is more preferable. Further, after preparing a dispersion by mixing both, it is preferable to apply and solidify on the substrate as soon as possible. The time from preparation of the dispersion to application is preferably from 0.1 to 60 minutes, 10 minutes is more preferable, and 0.1 to 2 minutes is still more preferable. In addition, what is necessary is just to perform both uniform mixing by conventional methods, such as spatula stirring, magnetic stirring, blade stirring, a homomixer.
The content of the hollow silica particles contained in the coating agent is preferably 10 to 70% by mass and more preferably 15 to 50% by mass from the viewpoint of coating operability and the performance of the obtained low dielectric film. The coating agent may contain a solvent (dispersion medium), and although it depends on the type of resin and the like, an alcohol solvent is usually preferable.

The coating agent for low dielectric film and low dielectric film of the present invention can contain mesoporous silica particles having no hollow structure within the range not inhibiting the object of the present invention, together with the hollow silica particles. From this point of view, it is preferable not to include mesoporous silica particles having no hollow structure.
In addition, the low dielectric film and coating agent of the present invention are known antioxidants, light stabilizers, antistatic agents, nucleating agents, flame retardants, plasticizers, stabilizers, colorants (pigments, dyes), antibacterial agents. , Surfactants, coupling agents, release agents and the like can be contained.

In the following production examples, examples and comparative examples, “%” is “% by mass”.
Various measurements of the hollow silica particles obtained in the production examples and the low dielectric films obtained in the examples and comparative examples were performed by the following methods.
(1) Powder X-ray diffraction (XRD) measurement of hollow silica particles X-ray source: Cu-kα, tube voltage: 40 mA, using a powder X-ray diffractometer (manufactured by Rigaku Denki Kogyo Co., Ltd., trade name: RINT2500VPC) Powder X-rays under conditions of tube current: 40 kV, sampling width: 0.02 °, divergence slit: 1/2 °, divergence slit length: 1.2 mm, scattering slit: 1/2 °, and light receiving slit: 0.15 mm Diffraction measurement was performed. A continuous scanning method with a scanning range of diffraction angle (2θ) of 1 to 20 ° and a scanning speed of 4.0 ° / min was used. The measurement was performed by packing the pulverized sample in an aluminum plate.
(2) Observation of particle shape of hollow silica particles The particle shape was observed using an electrolytic emission type high resolution scanning electron microscope (manufactured by Hitachi, Ltd., trade name: FE-SEM S-4000).

(3) Measurement of average primary particle diameter, average hollow part diameter, and average outer shell part thickness of hollow silica particles Accelerated using a transmission electron microscope (TEM) (manufactured by JEOL Ltd., trade name: JEM-2100) The particles were observed at a voltage of 160 kV. The diameter, hollow diameter, and outer shell thickness of all particles in five fields of view containing 20-30 particles were measured on a photograph, and the average primary particle diameter, average hollow diameter, and average outer shell thickness were measured. Furthermore, the ratio (mass%) of particles having a particle diameter within ± 30% of the average particle diameter relative to the whole particles was determined by calculation. In addition, observation was performed using what attached to Cu mesh (200-A mesh by Oken Shoji Co., Ltd.) with the carbon support film for high resolution, and removed the excess sample by the blow.
(4) Measurement of BET specific surface area and average pore diameter of hollow silica particles Using a specific surface area / pore distribution measuring device (manufactured by Shimadzu Corporation, trade name: ASAP2020), a multipoint method using liquid nitrogen The BET specific surface area was measured, and a value was derived within a range where the parameter C was positive. The BJH method was adopted for deriving the BET specific surface area, and the peak top was defined as the average pore diameter. The sample was pretreated at 250 ° C. for 5 hours.

(5) Measurement of dielectric constant and dielectric loss tangent A mixture in which hollow silica particles and a resin were kneaded was applied on a PET film, and after heat curing, the resin composition was peeled off from the film and cut into a rod shape to obtain a sample. Alternatively, a mold in which a groove having a width of 2 mm, a depth of 1.5 mm, and a length of 120 mm is dug in Teflon (registered trademark) resin, and a mixture obtained by kneading hollow silica particles and the resin is poured into the mold, and heat-cured, After cooling, the sample was removed from the mold. Samples obtained by either method had similar electrical characteristics.
Using a device in which a dielectric constant measuring device (resonator, 5.8 GHz) manufactured by Kanto Electronics Co., Ltd. is connected to a PNA microwave network analyzer “E8361A” (10 MHz to 67 GHz) manufactured by Agilent Using the resonator perturbation method, the dielectric constant and dielectric loss tangent of the previous sample were measured at 5.8 GHz.
When the dielectric constant is 3.5 or less and the dielectric loss tangent is 0.01 or less, it is a low dielectric film having sufficient insulation performance.

Production Example 1 (Production of hollow silica particles)
In a 20 L reactor, 16 kg of water, 66 g of 25% tetramethylammonium hydroxide, 68 g of dodecyltrimethylammonium bromide, and cationic acrylic polymer particles (manufactured by Nippon Paint Co., Ltd., trade name: Finesphere FS-501, average particle diameter 500 nm) 192 g was added and stirred, and 68 g of tetramethoxysilane was slowly added to the aqueous solution, stirred at room temperature (25 ° C.) for 5 hours, and then aged for 12 hours.
Next, the obtained white precipitate was filtered through a membrane filter having a pore size of 0.2 μm, washed with 10 L of water, dried at 100 ° C. for 5 hours, polymer particles as a core, and silica particles as a shell. A dry powder of core-shell type silica particles was obtained.
The obtained dry powder was heated to 600 ° C. at a rate of 1 ° C./min with air flow (3 L / min) using a high-speed heating furnace (trade name: SK-2535E manufactured by Motoyama Co., Ltd.). The organic component was removed by baking at 600 ° C. for 2 hours to obtain hollow silica particles. 50 g of the hollow silica particles were transferred to an alumina crucible and baked at 1000 ° C. for 72 hours in the air using the electric furnace.
The measurement results of the hollow silica particles after firing were as follows.
The average primary particle size was 480 nm, the average hollow portion diameter was 400 nm, the average outer shell thickness was 40 nm, and the BET specific surface area was 15 m ² / g.
-99.9 mass% of the whole particle | grains had a particle diameter within the average particle diameter +/- 30%.
-It was confirmed by average pore diameter measurement that there was no peak at 1 nm or more.
In the powder X-ray diffraction measurement, it was confirmed that there was no peak in the diffraction angle (2θ) corresponding to the range where the crystal lattice spacing (d) was less than 1 nm.

Example 1
0.6 g of hollow silica particles obtained in Production Example 1 were added to a bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., liquid type, grade: 828 (2 to trimer), viscosity: 12 to 15 Pa · s (25 ° C), epoxy equivalent: 184-194), epoxy resin curing agent (manufactured by Japan Epoxy Resin Co., Ltd., acid anhydride grade: YH306), curing accelerator (manufactured by Japan Epoxy Resin Co., Ltd., 2-ethyl-4 (5) -Methylimidazole, grade: EMI 24) was kneaded with 1.4 g of matrix resin mixed in a weight ratio of 5: 6: 0.05 to produce a low dielectric resin composition. This composition was poured into the Teflon (registered trademark) mold, heated at 80 ° C. for 3 hours in an electric dryer, further heated and cured at 120 ° C. for 6 hours, and cooled, and then a sample was taken out from the mold. Using this sample, dielectric constant and dielectric loss tangent were measured. The results are shown in Table 1.

Example 2
A low dielectric resin composition was produced in the same manner as in Example 1 except that 0.8 g of the hollow silica particles and 1.2 g of the matrix resin were changed in Example 1, and a sample was produced.
Comparative Example 1
In Example 1, a low dielectric resin composition was produced and a sample was produced in the same manner as in Example 1 except that the hollow silica particles were not used.
Comparative Example 2
In Example 1, a low dielectric resin composition was produced in the same manner as in Example 1 using hollow silica particles (specific surface area 1200 m ² / g) which were fired at 600 ° C. for 2 hours in Production Example 1, and a sample Was made.

Example 3
0.6 g of the hollow silica particles obtained in Production Example 1 were kneaded with 7 g of a polyimide resin (manufactured by Ube Industries, Ltd., trade name: U-Varnish S (solid content 20%)) to produce a low dielectric resin composition. . This composition is poured into the Teflon (registered trademark) mold, heated at 200 ° C. for 10 minutes in an electric dryer, taken out of the sample, and further heated at 450 ° C. for 10 minutes in a baking furnace to prepare a sample. did. Using this sample, dielectric constant and dielectric loss tangent were measured. The results are shown in Table 1.
Comparative Example 3
In Example 3, a low dielectric resin composition was produced and a sample was produced in the same manner as in Example 3 except that the hollow silica particles were not used.

From Table 1, the low dielectric resin composition containing the epoxy resin of Examples 1 and 2 containing hollow silica particles as a matrix resin has a dielectric constant of 2.31 and 2.29, respectively, and a dielectric loss tangent of 0.0078 and In contrast to the 0.0068, the resin composition of Comparative Example 1 that does not contain hollow silica particles has a high dielectric constant of 2.65 and a dielectric loss tangent of 0.0112. Further, in Comparative Example 2 including hollow particles having a high specific surface area of 1200 m ² / g, the dielectric constant is 2.63 and the dielectric loss tangent is as high as 0.0129. The low dielectric resin composition containing the polyimide resin of Example 3 as a matrix resin has a dielectric constant of 2.99 and a dielectric loss tangent of 0.0015, whereas the resin of Comparative Example 3 does not contain hollow silica particles. The composition has a high dielectric constant of 3.7 and a dielectric loss tangent of 0.0017.
From this, the low dielectric resin composition containing the hollow silica particles according to the present invention is a comparison containing hollow silica particles having a higher specific surface area than the resin composition of Comparative Example 1 or 3 not containing the hollow silica particles. It can be seen from Example 2 that it has a low dielectric constant and a low dielectric loss tangent that are clearly significant in practice.

Claims (8)

Hollow silica particles having an average particle diameter of 0.05 to 1 μm, 80% by mass or more of the whole particles having an average particle diameter of ± 30% or less and a BET specific surface area of less than 30 m ² / g, A low dielectric resin composition dispersed in a matrix resin.   2. The low dielectric resin according to claim 1, wherein the hollow silica particles do not show a peak at a diffraction angle (2θ) corresponding to a range of crystal lattice spacing (d) of less than 1 nm in powder X-ray diffraction measurement. Composition.   The low dielectric resin composition according to claim 1 or 2, wherein the content of the hollow silica particles is 10 to 60% by mass.   A low dielectric film comprising the low dielectric resin composition according to claim 1. The manufacturing method of the low dielectric resin composition in any one of Claims 1-3 containing following process (I)-(III).
Step (I): Step of preparing hollow silica particles (A) containing air inside the particles, or core-shell type silica particles (B) enclosing a material that disappears by firing to form a hollow portion Step (II): Step of preparing hollow silica particles (C) by firing the hollow silica particles (A) or the core-shell type silica particles (B) obtained in step (I) at a temperature exceeding 950 ° C. Step (III): A step of preparing a dispersion in which the hollow silica particles (C) obtained in the step (II) are dispersed in a matrix resin forming material. The method for producing a low dielectric film according to claim 4, comprising the steps (I) to (III) according to claim 5 and the following step (IV).
Step (IV): A step of solidifying the dispersion obtained in step (III) after applying it on the substrate.   The method for producing a low dielectric film according to claim 6, wherein the matrix resin forming material has a viscosity of 0.1 to 20 Pa · s. Hollow silica particles having an average particle diameter of 0.05 to 1 μm, 80% by mass or more of the whole particles having an average particle diameter of ± 30% or less and a BET specific surface area of less than 30 m ² / g, A coating agent for a low dielectric film dispersed in a matrix resin forming material.