JP2007308544A - Nano composite material having low dielectric constant and low refractive index - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica resin nano composite material which can realize a low dielectric constant and a low refractive index without needing the introduction of a special structure in the insulated resin, and to provide a method for producing the same. <P>SOLUTION: This silica resin nano composite material having a low dielectric constant and a low refractive index and having a nano porous structure having ≤100 nm diameter pores in the organic resin is obtained by heating a physically gelled organogel formed from silica fine particles, the organic resin, and an organic solvent to remove the organic solvent from the gelation product. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymer / ceramic nanocomposite material having a nanoporous structure with a diameter of 100 nm or less in an organic resin, and is widely applied as a low dielectric constant interlayer insulating material for multilayer wiring, a low reflection film for various displays, and a cladding material for a waveguide. it can.

  Epoxy resins are widely used as insulating resins for electronic materials. Epoxy resins range from liquid to solid at room temperature and are soluble in general-purpose solvents, so they are excellent in workability. Further, it is easily cured by various amine-based, acid anhydride-based and phenol-based curing agents or photoinitiators, and has excellent moldability. It is a well-balanced resin with excellent properties such as adhesion of cured products, mechanical properties, heat resistance, and electrical properties. Insulating resins for electronic materials are strongly desired to reduce the dielectric constant from the viewpoint of improving transmission speed. However, there is a limit to the reduction of the dielectric constant due to the influence of the epoxy group possessed by the epoxy resin for electronic materials, the amino group serving as a curing agent, phenol, or polar groups such as hydroxyl groups and carboxyl groups generated after curing. Furthermore, expansion of the application range of various displays to low-reflection films, waveguide claddings, and the like has been studied. However, as in the case of the dielectric constant, there is a limit to lowering the refractive index due to the influence of polar groups in the molecular structure. The low dielectric constant of the epoxy resin introduces an alicyclic structure instead of the aromatic group introduced as a heat-resistant skeleton. Alternatively, it is carried out by a method in which polar groups such as amino groups and phenol groups are as few as possible as a curing agent and a hydroxyl group is not generated during the curing process. As described above, the epoxy resin is a well-balanced resin having excellent properties such as adhesion and heat resistance, but the adhesion is impaired by reducing the polar groups. The introduction of an alicyclic structure or a bulky alkyl group has a problem that heat resistance must be sacrificed. Furthermore, the introduction of a special structure has a problem that the synthesis cost is increased. In addition, there is a material using a porous material of polytetrafluoroethylene as a reinforcing material, but there is a limitation in use because it is necessary to use a special reinforcing material. There is also a problem of becoming an opaque material.

  On the other hand, there is a method of dispersing silica fine particles having a nanoporous structure in an epoxy resin (for example, Patent Document 1). This method uses silica hollow spheres having voids having a size ranging from about 10 mm (1 nm) to about 100 mm (10 nm) manufactured by a special method. The size of the silica sphere itself can range from about 10 nm to about 1,000 nm. According to this method, a resin having a dielectric constant of 3.0 or less can be obtained by dispersing the above-described special silica hollow spheres in an epoxy resin or a polyimide resin. According to this method, depending on the amount of silica hollow spheres dispersed, there is a possibility that a low dielectric constant can be achieved without impairing general properties such as epoxy resin.

  In addition, a low-refractive-index composite using a cage silsesquioxane and utilizing molecular-level voids in the molecular structure has also been studied (for example, Patent Document 2).

JP-A-5-182518 JP 2000-334881 A

  However, in order to obtain the silica hollow sphere described in the cited document 1, the temperature is from room temperature to 300 ° C., from 300 ° C. to 600 ° C., from 600 ° C. to 800 ° C., in an oxygen atmosphere or a chlorine / argon gas atmosphere for a long time. Heat treatment is required, and eventually flash sintering in the range of about 800 ° C. to about 1200 ° C. is necessary. There is also a problem that it is difficult to control the void content.

  In Cited Document 2, problems remain in the synthesis of cage silsesquioxane, control of molecular weight, stabilization of characteristics, and the like.

  The present invention has been made in view of the above problems, and provides a silica resin nanocomposite material capable of realizing a low dielectric constant and a low refractive index without requiring the introduction of a special structure in an insulating resin, and a method for producing the same. The purpose is to do.

  As a result of intensive studies in order to achieve the above object, the present inventors have used a physical gelled organogel formed from silica fine particles, an organic resin, and an organic solvent, so that the organic resin has a diameter of 100 nm or less. It was confirmed that a low dielectric constant and low refractive index material having a nanoporous structure with bubbles was obtained. Silica fine particles having a particle size of 5 nm to 100 nm dispersed in an organic solvent are dispersed in an epoxy resin and then brought into a physical gelation state. Thereafter, the organic solvent is removed from the gelled product by heating.

  In order to achieve the above object, the present invention provides a low dielectric constant low refractive index silica resin nanocomposite material in which silica fine particles are dispersed in an organic resin, wherein the organic resin has a low dielectric constant and a low bubble having a diameter of 100 nm or less. Features refractive index silica resin nanocomposite material.

  In the present invention, a solution comprising an organic resin in which silica fine particles are dispersed and a solvent is allowed to stand at room temperature to form a physical gel, then the solvent is removed by heating, and the diameter of the organic resin in which the silica fine particles are dispersed is removed. It is characterized by a method for producing a low dielectric constant, low refractive index silica resin nanocomposite material that forms bubbles of 100 nm or less.

  According to the present invention, a low dielectric constant having a relative dielectric constant of 2.0 to 3.0 is obtained at low cost without using a special device or chemical because a physical gel phenomenon incorporating a solvent, which is a phenomenon peculiar to nanoparticles, is used. For example, when applied to an interlayer insulating film of a wiring board, the signal transmission speed can be greatly improved. In addition, the silica resin nanocomposite material of the present invention becomes a colorless and transparent resin plate, the refractive index of light is reduced, and the application range is greatly expanded as an antireflection film for various displays and a clad material for waveguides.

  The low dielectric constant and low refractive index silica resin nanocomposite material of the present invention is made into a physical gelation state after silica fine particles having a particle diameter of 5 nm to 100 nm dispersed in an organic solvent are dispersed in an epoxy resin. Thereafter, it is prepared by a method of removing the organic solvent from the gelled product by heating. Although the solvent is removed during this heating process, the shape and volume of the composite resin hardly change. The composite resin is colorless and transparent, and the size of the voids after the solvent is removed is 100 nm or less. Finally, since the epoxy resin is cured by heating, the voids become closed cells, so there is no problem such as water absorption. The content rate of bubbles to be voids is 5 to 40% by volume. Here, the gel refers to a state in which the three-dimensional network contains a large amount of a solvent. A gel containing water is called a hydrogel, a gel containing an organic solvent is called an organogel, and a gel containing a gas is called an aerogel. Moreover, the gel by a chemical bond (covalent bond) is called a chemical gel, and the gel by a physical bridge | crosslinking (noncovalent bond) is called a physical gel. In the present invention, an organogel containing a large amount of solvent is used as a gel by physical crosslinking. In the present invention, the organic solvent is removed from the physically gelled organogel formed of silica fine particles, organic resin, and organic solvent to uniformly form bubbles in the composite organic resin. Therefore, unlike the method using hollow silica, the bubble content can be controlled by the amount of the organic solvent and the condition of the solvent drying process. Further, since the generated bubbles are formed in the organic resin between the silica fine particles uniformly dispersed, they exist uniformly in a size of 10 nm to 100 nm in diameter.

  In the present invention, it is effective to use a hydrophobic organosilica sol dispersed at the primary particle level in an organic solvent, but the same applies to silica fine particles that have been surface-treated with a surfactant or the like to improve dispersibility in an organic solvent. An effect is obtained. Organic resins can be applied to all thermosetting resins such as epoxy resins, polyimide resins, cyanate resins, phenol resins, methacrylate resins, and unsaturated polyester resins, but thermoplastics such as polyamide resins that are soluble in solvents. Resin is also applicable. In particular, when applied to an epoxy resin, the effect is remarkable.

  The average particle diameter of the silica fine particles is applicable in the range of 5 nm to 200 nm, and particularly in the range of 5 nm to 100 nm shows a high effect. As the solvent, tetrahydrofuran, acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-methoxyethanol, N, N-dimethylformamide, N, N-dimethylacetamide, etc. can be used, but they can be removed from the composite resin before the epoxy resin is cured. A lower boiling point is preferred.

  The blending amount of silica fine particles is not particularly limited, but is preferably in the range of 5 wt% to 30 wt% in consideration of the balance of various characteristics. For example, as described in JP-A-6-316407 and the like, spherical silica having a uniform particle diameter in a particle diameter range of 3 nm to 100 nm is obtained by a silica sol production method obtained by hydrolyzing an alkyl silicate with an alkali catalyst. can get. In the present invention, the silica fine particles thus obtained can be applied. As a matter of course, the same effect can be obtained with silica fine particles obtained by other production methods. A method using silica fine particles obtained by hydrophobizing the thus obtained hydrophilic colloidal silica with a silylating agent such as a disiloxane compound or a monoalkoxysilane compound is preferred. Of course, it is also possible to apply silica fine particles that have been surface-treated by a method of increasing the dispersibility in an organic solvent by hydrophobizing the surface of the silica fine particles with a silane coupling agent or a method of increasing the dispersibility with a surfactant.

  As a procedure for producing the nanocomposite material, first, a varnish in which an epoxy resin, a curing agent, and a curing accelerator as required is dissolved in a low boiling point solvent such as methyl ethyl ketone in which silica fine particles are dispersed is prepared. Next, this varnish is uniformly applied on the substrate. When this coated substrate is stored in a sealed container, the coated film becomes a physical gel and solidifies within a few hours to a few days. The solvent is removed by heat-treating the physical gel. By this heat treatment, the coating film becomes light as much as the solvent is removed, but the shape and volume hardly change, and the transparency increases, that is, the refractive index decreases. The heat treatment for removing the solvent is preferably performed in an inert gas atmosphere such as nitrogen or in a reduced pressure atmosphere. Thereafter, depending on the application, the composite resin is cured by heating in an inert gas atmosphere such as nitrogen. In the case of photocuring, after curing by UV exposure, post-curing by heating is performed, but the heat treatment for removing the solvent may be performed before exposure or after exposure.

  Hereinafter, specific examples of the low dielectric constant and low refractive index nanocomposite material of the present invention will be described.

Example 1
An alicyclic epoxy resin (Celoxide 2021, manufactured by Daicel Chemical Industries, epoxy equivalent 176), 3or4-methyl-hexahydrophthalic anhydride (HN-5500, manufactured by Hitachi Chemical Co., Ltd.) was mixed at a molar ratio of 1: 1.5. . Further, 0.2 part by weight (based on epoxy and acid anhydride) of 2-ethyl-4-methylimidazole CN (2E4MZ-CN, manufactured by Shikoku Kasei) was added as a curing accelerator to prepare a liquid resin mixture. To this liquid resin mixture, methyl ethyl ketone slurry (Nissan Chemical MEK-ST) in which 30 wt% of hydrophobic silica having an average particle size of 12 nm was dispersed was mixed to prepare a silica filler dispersed varnish. MEK-ST was adjusted at a ratio of 50 parts by weight to 85 parts by weight of the epoxy resin containing a curing agent and a curing accelerator. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 10 μm. Thereafter, it was stored in a sealed glass container for 24 hours to obtain a physical gel-like coating film. This physical gel-like coating film is heated at 90 ° C. under reduced pressure for 30 minutes to dry and remove methyl ethyl ketone remaining in the coating film. The sample was then cured by heating at 130 ° C. for 1 hour and 170 ° C. for 2 hours. FIG. 1 shows a high-resolution SEM photograph (observed with a Hitachi scanning electron microscope S-900) of the cross section of the coating film formed into a physical gel and the cross section of the sample after heat curing. In the physical gel, silica is uniformly dispersed, and it is observed that a network structure containing a resin and a solvent is formed. When this is heat-treated, voids of 30 nm to 50 nm are observed on the entire surface. This is presumed to be a structure in which the solvent is removed while retaining the silica fine particle network and the resin is cured, so that the solvent removal portion remains as a very small void. After curing, the coating film is colorless and transparent and has a low refractive index. In addition, the porosity of the obtained nanoporous structure cured film was 25 vol%. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric characteristics.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (model 4192F manufactured by Hewlett-Packard Co.), the dielectric constant was 2.5. The refractive index of the film produced at the same time was 1.39 at a measurement wavelength of 633 nm.

(Example 2)
A liquid resin composition comprising 90 parts by weight of an alicyclic epoxy resin (Celoxide 2021, manufactured by Daicel Chemical Industries, epoxy equivalent 176) and 0.9 part by weight of a photopolymerization initiator (Adekaoptoma SP-170), an average particle size of 12 nm. A silica filler dispersed varnish was prepared by mixing 33 parts by weight of methyl ethyl ketone slurry (Nissan Chemical MEK-ST) in which 30 wt% of hydrophobic silica was dispersed. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 10 μm. Then, it was stored in a cool and dark place in a sealed glass container for 24 hours to obtain a physical gel-like coating film. This physical gel-like coating film is heated at 90 ° C. under reduced pressure for 30 minutes to dry and remove methyl ethyl ketone remaining in the coating film. Thereafter, the coating film was cured by UV exposure (365 nm, 4 J / cm ² ), and further a cured film was obtained by heating at 100 ° C. for 1 hour and 170 ° C. for 1 hour. After curing, the coating film is colorless and transparent and has a low refractive index. In addition, the porosity of the obtained nanoporous structure cured film was 15 vol%. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric characteristics.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (model 4192F manufactured by Hewlett-Packard Co.), the dielectric constant was 2.6. The refractive index of the film produced at the same time was 1.42 at a measurement wavelength of 633 nm.

Example 3
Bisphenol type epoxy resin (Epicoat 828, Japan epoxy resin, epoxy equivalent 189) and 3or4-methyl-hexahydrophthalic anhydride (HN-5500, manufactured by Hitachi Chemical Co., Ltd.) were mixed at a molar ratio of 1: 2. Further, 2-ethyl-4-methylimidazole CN (2E4MZ-CN, manufactured by Shikoku Kasei Co., Ltd.) was added as a curing accelerator to 0.2 weight capital (based on epoxy and acid anhydride) to prepare a liquid resin mixture. A silica filler dispersed varnish was prepared by mixing this liquid resin mixture with methyl ethyl ketone slurry in which 30 wt% of hydrophobic spherical silica having an average particle diameter of 25 nm was dispersed. Toluene slurry in which spherical silica was dispersed with respect to 90 parts by weight of the epoxy resin containing a curing agent and a curing accelerator was uniformly mixed at a ratio of 33 parts by weight. The varnish was applied on a glass plate on which an electrode was formed with a doctor blade, and the thickness was 20
A μm coating film was formed. Thereafter, it was stored in a sealed glass container for 48 hours to obtain a physical gel-like coating film. This physical gel-like coating film was heated at 90 ° C. under reduced pressure for 30 minutes to dry and remove methyl ethyl ketone remaining in the coating film. Next, the sample was cured by heating at 130 ° C. for 1 hour and at 170 ° C. for 2 hours in a nitrogen gas atmosphere. After curing, the coating film is colorless and transparent and has a low refractive index. In addition, the porosity of the obtained nanoporous structure cured film was 10 vol%. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric properties.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (model 4192F manufactured by Hewlett-Packard Co.), the dielectric constant was 3. The refractive index of the film produced at the same time was 1.49 at a measurement wavelength of 633 nm.

Example 4
Phenol novolac type epoxy resin (Epicoat 152, manufactured by Japan Epoxy Resin, epoxy equivalent 175) and 3or4-methyl-hexahydrophthalic anhydride (HN-5500 manufactured by Hitachi Chemical Co., Ltd.) were mixed at a molar ratio of 1: 1.5. Further, 0.2 part by weight (based on epoxy and acid anhydride) of 2-ethyl-4-methylimidazole CN (2E4MZ-CN, manufactured by Shikoku Kasei) was added as a curing accelerator to prepare a liquid resin mixture. To this liquid resin mixture, methyl ethyl ketone slurry (Nissan Chemical MEK-ST) in which 30 wt% of hydrophobic silica having an average particle diameter of 12 nm was dispersed was mixed to prepare a silica filler dispersed varnish. MEK-ST was adjusted at a ratio of 33 parts by weight to 90 parts by weight of the epoxy resin containing a curing agent and a curing accelerator. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 10 μm. Thereafter, it was stored in a sealed glass container for 24 hours to obtain a physical gel-like coating film. Further, this physical gel-like coating film was heated at 90 ° C. under reduced pressure for 30 minutes to dry remove methyl ethyl ketone remaining in the coating film. The sample was then cured by heating at 130 ° C. for 1 hour and 170 ° C. for 2 hours. After curing, the coating film is colorless and transparent and has a low refractive index. In addition, the porosity of the obtained nanoporous structure cured film was 20 vol%. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric characteristics.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (type 4192F manufactured by Hewlett-Packard Co.), the dielectric constant was 2.7. Moreover, the refractive index of the film produced at the same time was 1.49 at a measurement wavelength of 633 nm.

(Comparative Example 1)
An alicyclic epoxy resin (Celoxide 2021, manufactured by Daicel Chemical Industries, epoxy equivalent 176), 3or4-methyl-hexahydrophthalic anhydride (HN-5500, manufactured by Hitachi Chemical Co., Ltd.) was mixed at a molar ratio of 1: 1.5. . Further, 0.2 part by weight (based on epoxy and acid anhydride) of 2-ethyl-4-methylimidazole CN (2E4MZ-CN, manufactured by Shikoku Kasei) was added as a curing accelerator to prepare a liquid resin mixture. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 10 μm. The sample was then cured by heating at 130 ° C. for 1 hour and 170 ° C. for 2 hours. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric characteristics.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (model 4192F manufactured by Hewlett-Packard Co.), the dielectric constant was 3.3. Moreover, the refractive index of the film produced at the same time was 1.51 at a measurement wavelength of 633 nm.

(Comparative Example 2)
A sample was prepared in exactly the same manner as in Example 1, except that the step of obtaining a physical gel-like coating film by storing in the sealed glass container of Example 1 for 24 hours was omitted. The dielectric constant was 3.4, and the refractive index was 1.48.

  Compared with the matrix resin of Comparative Example 1, the refractive index was slightly reduced, but the dielectric constant at 1 MHz was slightly higher.

(Comparative Example 3)
A liquid resin composition comprising 90 parts by weight of an alicyclic epoxy resin (Celoxide 2021, manufactured by Daicel Chemical Industries, epoxy equivalent 176) and 0.9 part by weight of a photopolymerization initiator (Adekaoptoma SP-170) was prepared. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 10 μm. Thereafter, the coating film was cured by UV exposure (365 mm, 4 J / cm ² ), and further a colorless and transparent cured film was obtained by heating at 120 ° C. for 2 hours and 180 ° C. for 2 hours. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric properties.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (type 4192F manufactured by Hewlett-Packard Company), the dielectric constant was 3.1. Moreover, the refractive index of the film produced at the same time was 1.49 at a measurement wavelength of 633 nm.

(Comparative Example 4)
A sample was prepared in exactly the same manner as in Example 2 except that the step of obtaining a physical gel-like coating film by storing in the sealed glass container of Example 2 for 24 hours was omitted. The dielectric constant was 3.3, and the refractive index was 1.47. Compared with the matrix resin of Comparative Example 3, the refractive index was slightly reduced but 1
The dielectric constant at MHz was slightly higher.

(Comparative Example 5)
Bisphenol A type epoxy resin (Epicolate 828, Japan epoxy resin, epoxy equivalent 189) and 3or4-methyl-hexahydrophthalic anhydride (HN-5500, manufactured by Hitachi Chemical Co., Ltd.) were mixed at a molar ratio of 1: 2. Further, 0.2 part by weight (based on epoxy and acid anhydride) of 2-ethyl-4-methylimidazole CN (2E4MZ-CN, manufactured by Shikoku Kasei) was added as a curing accelerator to prepare a liquid resin mixture. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 20 μm. Next, in a nitrogen gas atmosphere, the sample was cured by heating at 130 ° C. for 1 hour and 170 ° C. for 2 hours to obtain a colorless and transparent coating film. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric characteristics.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (model 4192F manufactured by Hewlett-Packard), the dielectric constant was 3.4. Moreover, the refractive index of the film produced at the same time was 1.54 at a measurement wavelength of 633 nm.

(Comparative Example 6)
A sample was prepared in exactly the same manner as in Example 3 except that the step of obtaining a physical gel-like coating film by storing in the sealed glass container of Example 3 for 48 hours was omitted. The dielectric constant was 3.5, and the refractive index was 1.52. Compared with the matrix resin of Comparative Example 5, the refractive index was slightly reduced but 1
The dielectric constant at MHz was slightly higher.

(Comparative Example 7)
Phenol novolac type epoxy resin (Epicoat 152, manufactured by Japan Epoxy Resin, epoxy equivalent 175) and 3or4-methyl-hexahydrophthalic anhydride (HN-5500 manufactured by Hitachi Chemical Co., Ltd.) were mixed at a molar ratio of 1: 1.5. Further, 0.2 part by weight (based on epoxy and acid anhydride) of 2-ethyl-4-methylimidazole CN (2E4MZ-CN, manufactured by Shikoku Kasei) was added as a curing accelerator to prepare a liquid resin mixture. This varnish was applied on a glass plate on which an electrode was formed with a doctor blade to form a coating film having a thickness of 10 μm. Next, this sample was cured by heating at 130 ° C. for 1 hour and at 170 ° C. for 2 hours to obtain a colorless and transparent coating film. A circular electrode having a thickness of about 500 mm and 1 cm ² was formed on the surface of this sample by vapor deposition of aluminum, and used as a sample for evaluating dielectric characteristics.

  As a result of measuring the dielectric constant at a frequency of 1 MHz using an LF impedance analyzer (type 4192F manufactured by Hewlett-Packard Co.), the dielectric constant was 3.4. The refractive index of the film produced at the same time was 1.59 at a measurement wavelength of 633 m.

(Comparative Example 8)
A sample was prepared in exactly the same manner as in Example 4, except that the step of obtaining a physical gel-like coating film by storing in the sealed glass container of Example 4 for 24 hours was omitted. The dielectric constant was 3.5, and the refractive index was 1.57. Although the refractive index was slightly reduced as compared with the matrix resin of Comparative Example 7, the dielectric constant at 1 MHz was slightly higher.

  The conditions and results of the above examples and comparative examples are summarized in Tables 1 and 2. Comparative Examples 1, 3, 5, and 7 are evaluation results of the matrix resins of Examples 1 to 4. In each of the embodiments, a significant reduction in dielectric constant and reduction in refractive index are realized. Further, Comparative Examples 2, 4, 6, and 8 are cases where the physical gelation process of Examples 1 to 4 was omitted, but since a porous structure was not realized, a remarkable reduction in dielectric constant and low refractive index were achieved. Conversion was not observed. Next, the effect is demonstrated using the Example to a multilayer wiring board, an antireflection film, and an optical waveguide.

(Example 5)
A multilayer wiring board in which the nanocomposite material of the present invention was applied to an insulating layer in the process shown in FIG. 2 was produced. Details will be described below. The epoxy varnish containing the hydrophobic silica prepared in Example 2 was applied to the upper and lower sides of the 0.2 mm thick epoxy laminate (FR-5) 2 having the copper wiring 1 having a thickness of 12 μm formed on both sides, and the physical thickness of 25 μm. A gelled coating film 3 was formed. The physical gel-like coating film is heated at 90 ° C. under reduced pressure to dry and remove methyl ethyl ketone remaining in the coating film. Thereafter, the coating film was cured by UV exposure wavelength (365 nm, 4 J), and further a cured film was obtained by heating at 120 ° C. for 2 hours and 170 ° C. for 2 hours. After that, the blind via 4 was formed by laser, and then copper 5 having a thickness of 18 μm was formed on the entire surface by electroless copper plating and electrolytic copper plating. Next, a portion to be an outer layer wiring was covered with a resist, and copper other than the wiring portion was removed by etching to form an outer layer wiring, a via conduction portion, and a pad portion 6. By this process, a multilayer wiring board 8 having a four-layer wiring having a low dielectric constant insulating layer 7 having a dielectric constant of 2.6 in two upper and lower layers was obtained.

(Example 6)
A liquid resin composition comprising 90 parts by weight of an alicyclic epoxy resin (Celoxide 2021, manufactured by Daicel Chemical Industries, epoxy equivalent 176) and 0.9 part by weight of a photopolymerization initiator (Adekaoptoma SP-170), an average particle size of 12 nm. A silica filler dispersed varnish was prepared by mixing 33 parts by weight of methyl ethyl ketone slurry (Nissan Chemical MEK-ST) in which 30 wt% of hydrophobic silica was dispersed. The produced varnish was applied on a BK7 glass (refractive index 1.52, wavelength 633 nm) substrate by spray coating to obtain a coating film having a thickness of 550 nm. Thereafter, it was stored in a cool and dark place in a sealed glass container for 6 hours to obtain a physical gel-like coating film. This physical gel-like coating film is heated at 70 ° C. under reduced pressure for 30 minutes to dry and remove methyl ethyl ketone remaining in the coating film. Thereafter, the coating film is cured by UV exposure (365 nm, 4 J / cm ² ), and further at 100 ° C.,
A transparent cured film was obtained by heating at 180 ° C. for 2 hours for 1 hour. He-Ne laser light (wavelength 633 mm) was incident on the fabricated substrate from the vertical direction and the reflectance was measured. The reflectance was greatly reduced to 1.9%, and the fabricated low refractive index layer was significantly reflected. The prevention effect was shown.

(Comparative Example 9)
When a He—Ne laser beam (wavelength 633 nm) was incident on the BK7 glass substrate from the vertical direction and the reflectance was measured, the reflectance was 4.5%.

(Comparative Example 10)
A liquid resin composition comprising 90 parts by weight of an alicyclic epoxy resin (Celoxide 2021, manufactured by Daicel Chemical Industries, epoxy equivalent 176) and 0.9 part by weight of a photopolymerization initiator (Adekaoptoma SP-170) was prepared. This varnish is applied onto a glass plate on which an electrode has been formed by spray coating, dried, and then the coating film is cured by UV exposure (365 m, 4 J / cm ² ). A colorless and transparent cured film having a thickness of 550 nm was obtained by heating of. He—Ne laser light (wavelength 633 m) was incident on the manufactured substrate from the vertical direction, and the reflectance was measured. As a result, the reflectance was 4.0%.

(Example 7)
By a process similar to that of Example 6, a low refractive index under cladding having a thickness of 100 μm was formed on a BK7 glass substrate. However, the doctor blade method was used for coating. Thereafter, the varnish used in Comparative Example 10 was applied onto the underclad using a doctor blade, and a core having a thickness of 40 μm was formed by the same process as in Comparative Example 10. Again, by the same process as in Example 6, a low refractive index overclad was formed on the core to form a slab type optical waveguide. When He—Ne laser light was incident from a single surface of the optical waveguide, the guided light was confirmed.

A high-resolution SEM photograph of a cross section of a coating film that has been physically gelled and a cross section of a sample after heat curing. The figure which shows the preparation process of a multilayer wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Copper wiring, 2 ... Epoxy laminated board, 3 ... Coating film, 4 ... Blind via, 5 ... Copper, 6 ... Pad part, 7 ... Low dielectric constant insulating layer, 8 ... Multilayer wiring board.

Claims (10)

  A low dielectric constant, low refractive index silica resin nanocomposite material in which silica fine particles are dispersed in an organic resin, wherein the organic resin has bubbles having a diameter of 100 nm or less. material.   2. The low dielectric constant and low refractive index silica resin nanocomposite material according to claim 1, wherein the content rate of the bubbles is 5 to 40% by volume.   2. The low dielectric constant and low refractive index silica resin nanocomposite material according to claim 1, wherein the silica fine particles have an average particle diameter of 5 nm to 100 nm.   The low dielectric constant low refractive index silica resin nanocomposite material according to claim 1, obtained by heating a physical gel formed from silica fine particles, an organic resin, and an organic solvent.   5. The low dielectric constant low refractive index silica resin nanocomposite material according to claim 4, wherein the silica fine particles are hydrophobic silica that can be dispersed in an organic solvent at a primary particle level.   A solution consisting of an organic resin in which silica particles are dispersed and a solvent is allowed to stand at room temperature to form a physical gel, and then the solvent is removed by heating to form bubbles having a diameter of 100 nm or less in the organic resin in which the silica particles are dispersed. A method for producing a low dielectric constant, low refractive index silica resin nanocomposite material, comprising:   The method for producing a low dielectric constant, low refractive index silica resin nanocomposite material according to claim 6, wherein the amount of silica fine particles in the solution is 5 wt% to 30 wt%.   A wiring board having an insulating layer and a wiring layer, wherein the low dielectric constant silica resin nanocomposite material according to claim 1 is used for the insulating layer.   An antireflection film obtained by applying the low refractive index silica resin nanocomposite material according to claim 1 to a base material. An optical waveguide characterized by using the low refractive index silica resin nanocomposite material according to claim 1 as a clad material.

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