JP2011102373A - Paste and optical waveguide using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paste wherein inorganic nanoparticles are dispersed, which undergoes no increase in viscosity and is excellent in shelf stability, and to stably produce an optical waveguide using the same, which is favorable in terms of optical transparency, thermomechanical property and insulation reliability. <P>SOLUTION: The paste comprises (A) the inorganic particles, (B) a compound having a polymerizable group and a carboxyl group, (C) an amine compound having a polymerizable group and (D) an organic solvent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a paste in which inorganic particles are dispersed in an organic substance, and an optical waveguide using the paste.

  With the downsizing and higher performance of electronic devices, optical interconnection technology is being developed that replaces signal transmission between chips in devices that have been performed by conventional electrical signals with optical signals. Optical wiring materials, which are optical signal media, are required to have high transparency and electrical and thermomechanical reliability. On the other hand, a dispersion liquid in which barium sulfate particles are dispersed and a matrix resin are mixed to produce a photosensitive paste composition, which is patterned by a photolithography method to obtain an optical waveguide that exhibits athermal properties. A technique is known (see, for example, Patent Document 1). In this technology, nano-dispersion of particles is realized in an organic solvent using a carboxyl group-containing resin as a dispersant for barium sulfate particles.

  On the other hand, a technique for improving the dispersibility and storage stability of a dispersion by adding an amine compound when dispersing inorganic particles or an organic pigment is known (see, for example, Patent Documents 2 to 3).

International Publication WO08 / 056639 Pamphlet JP 2000-321768 A JP 2004-18690 A

  However, in the conventional method, the viscosity of the paste may increase while the paste in which the inorganic particles are dispersed is manufactured or stored. With such a paste, it may be difficult to apply it on the substrate, or the linear expansion coefficient of the cured product of the paste may be increased or the insulation reliability may be deteriorated.

  An object of the present invention is to solve such problems, and to provide a paste composition having excellent storage stability, low linear expansion coefficient after curing, and excellent insulation reliability.

  The present invention is a paste containing (A) inorganic particles, (B) a compound having a polymerizable group and a carboxyl group, (C) an amine compound having a polymerizable group, and (D) an organic solvent.

  The paste of the present invention does not increase in viscosity during production or storage. This paste can be applied uniformly on the substrate, and the cured product has a low coefficient of linear expansion and excellent insulation reliability, and its properties do not deteriorate over time during manufacture and storage of the paste.

Schematic diagram showing the structure of a channel-type optical waveguide Schematic diagram showing the structure of a slab optical waveguide Top view of copper comb electrode

  The paste of the present invention contains (A) inorganic particles, (B) a compound having a polymerizable group and a carboxyl group, (C) an amine compound having a polymerizable group, and (D) an organic solvent. Hereinafter, a compound having a polymerizable group and a carboxyl group is referred to as “compound A”, and an amine compound having a polymerizable group is referred to as “compound B”.

  Since the compound A in the paste of the present invention is polymerized by light irradiation or heating after the paste is applied and dried, it becomes a matrix resin in a cured product obtained by curing the paste. Moreover, it has a function of improving the dispersibility of the inorganic particles in the paste.

  The paste of the present invention has a low viscosity and little increase in viscosity over time. The reason why the paste of the present invention exhibits such an effect is considered as follows. Compound A is a compound having a carboxyl group, and is considered to have affinity with inorganic particles by dissociating and ionizing hydrogen ions in an organic solvent at a certain ratio. Here, the proportion of the carboxyl group of compound A present in the organic solvent after dissociating hydrogen ions depends on the concentration of the dissociated hydrogen ions in the solvent. If compound B that captures hydrogen ions is contained in the paste, the dissociated hydrogen ions are captured by compound B, whereby the equilibrium moves in the direction in which the carboxyl group of compound A further dissociates. Therefore, it is considered that dispersibility of the inorganic particles is improved by increasing the amount of the compound A that is dissociated and presenting more compounds A on the surface of the inorganic particles.

  Further, the polymerizable group in the compound B is an organic group that can be polymerized by light addition or heat by a polyaddition reaction or a radical reaction. In the paste of the present invention, when compound A or other polymerizable group-containing resin in the paste is polymerized as will be described later, compound B also polymerizes with compound A and the like. Does not degrade the mechanical strength.

  On the other hand, when an amine compound having no polymerizable group is used instead of compound B, the main chain and side chain of the amine compound can move relatively freely in the cured product obtained by curing the paste. The amine compound undergoes a large thermal motion during heating. Therefore, the thermal expansion of the cured product, the generation of cracks associated therewith, and the thermal decomposition of the cured product may be promoted. That is, the thermal expansion coefficient of the cured product may be increased, and insulation reliability may be impaired.

  Examples of the polymerizable group of Compound B include a vinyl group, an acrylate group, a methacrylate group, an epoxy acrylate group, and an epoxy methacrylate group.

  Compound B is preferably a compound represented by the following general formula (1).

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different. n is an integer of 1-4.

  Specific examples of the compound B represented by the general formula (1) include aminoethyl acrylate, N-ethylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethyl. Examples include aminopropyl acrylate, and those obtained by replacing these acrylates with methacrylate. Examples of commercially available products include “Light Ester DM” (chemical name: N, N-dimethylaminoethyl methacrylate) and “Light Ester DE” (chemical name: N, N-diethylaminoethyl methacrylate) manufactured by Kyoeisha Chemical Co., Ltd. Can be mentioned.

  The content of Compound B in the paste of the present invention is preferably 0.1% by weight or more and 10% by weight or less with respect to Compound A. When the content of compound B with respect to compound A in the paste is 0.1% by weight or more, the viscosity of the paste can be maintained in a low state. On the other hand, when the content of compound B with respect to compound A in the paste is more than 10% by weight, a good balance of inorganic particle dispersion may be lost, and the viscosity immediately after the paste preparation may be increased. However, even in such a case, the viscosity does not increase during storage. In order to maintain a low viscosity from the beginning, the content of compound B relative to compound A is preferably 10% by weight or less.

The inorganic particles used in the present invention are not particularly limited, but Si, Al, Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Ag, In, Sn, Sb, Te, Cs, Ba, Hf, Ta, W, Re, La, Ce, Pr, Nd, Pm, Sm, Eu, Examples thereof include oxides such as Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, single salts such as sulfates, carbonates, and fluorides, or double salts (such as MgAl ₂ O ₄ ).

  When light enters a material in which particles are dispersed in a matrix resin like the material of the present invention, Rayleigh scattering is caused by the dispersed particles. When the Rayleigh scattering is small, the irradiated light is transmitted through the material without being scattered, so that a good pattern processing without wiring thickening can be realized. In addition, if the Rayleigh scattering is small, the light transmittance of the cured product of the paste becomes good.For example, when an optical waveguide is produced by curing the paste, there is little scattering of the optical signal propagating through the optical waveguide. Propagation loss is reduced. Since Rayleigh scattering is proportional to the cube of the particle diameter of the dispersed particles, the number average particle diameter of the inorganic particles in the paste is preferably smaller in order to suppress the scattering.

  The number average particle diameter of the inorganic particles in the paste of the present invention is preferably 1 nm or more and 50 nm or less. The inorganic particles in the paste include those in the state of primary particles in which aggregation is completely loosened, and those in the state in which a plurality of primary particles are aggregated. Here, the particle diameter of the inorganic particles is the particle diameter of the primary particles that are not aggregated, and the particle diameter of the aggregates is the aggregate of the primary particles. As a method of measuring the number average particle diameter of the inorganic particles in the paste, there is a method of directly observing the particles with SEM (scanning electron microscope) or TEM (transmission electron microscope) and calculating the number average of the particle diameters. It is done.

  When the number average particle diameter of the inorganic particles is 50 nm or less, the Rayleigh scattering is reduced, and thus good pattern processing can be realized by a photolithography method. Further, the light transmittance of the cured paste is improved. On the other hand, when the number average particle diameter of the inorganic particles is 1 nm or more, the specific surface area with respect to the volume of the particles becomes small, so that the dispersibility of the particles becomes good.

  The content of the inorganic particles in the paste of the present invention is preferably 30% by weight or more and 80% by weight or less with respect to the solid component. When the content of the inorganic particles with respect to the solid component in the paste is 30% by weight or more, the refractive index change rate and the linear expansion coefficient depending on the temperature of the obtained cured product can be further reduced. The content of the inorganic particles with respect to the solid component in the paste is more preferably 50% by weight or more. When the content of the inorganic particles with respect to the solid component in the paste is 80% by weight or less, the cured product obtained from the paste becomes tough and cracks are hardly generated. In addition, when pattern processing is performed by a photolithography method, the residue of unexposed portions during development is reduced. The content of inorganic particles with respect to the solid component in the paste is more preferably 70% by weight or less.

  The compound A in the paste of the present invention has a function of enhancing the dispersibility of the inorganic particles as described above. In addition, the polymerizable group in the compound A is an organic group that can be polymerized by light addition or heat by a polyaddition reaction or a radical reaction, and the compound A is a cured matrix resin obtained by curing the paste. It becomes.

  Furthermore, pattern processing by a photolithography method can be performed by curing the compound A in the paste with light. In this case, since the compound A is polymerized in a state where the inorganic particles are captured in the exposed area, a strong network is formed starting from the inorganic particles, and swelling and dissolution of the exposed area during development can be suppressed, so a clear pattern can be obtained. The shape can be realized. In the unexposed area, the carboxyl group of compound A dissolves well in a developer such as an alkali developer, so that there is little residue after development.

  Examples of the polymerizable group of Compound A include a vinyl group, an acrylate group, a methacrylate group, an epoxy acrylate group, and an epoxy methacrylate group.

  The compound A used in the present invention is preferably one represented by the following general formula (2).

In the general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a divalent group represented by any one of the following general formulas (3) to (5).

  In general formula (3)-(5), l and m are the integers of 1-3, respectively.

  When l and m in the general formulas (3) to (5) are small, the number of polymerizable groups and carboxyl groups per unit weight increases, so that the polymerizability becomes better and the dispersion of inorganic particles Improves. On the other hand, when the number of l and m is large, the effect of causing steric hindrance when the compound A is coordinated to the inorganic particles is increased, so that dispersibility is improved. From these balances, l and m are preferably 2.

  Specific examples of the compound A represented by the general formula (2) include “HOA-MS” (a compound represented by the following formula (6)) and “HOA-HH” (the following formula) manufactured by Kyoeisha Chemical Co., Ltd. Compound represented by (7)), "HOA-MPL" (compound represented by the following formula (8)).

  The paste of the present invention polymerizes compound A to form a matrix in the cured product, but may further contain a resin that forms the matrix. The resin used at this time has a polymerizable group such as polyamic acid, vinyl resin, norbornene resin, epoxy resin, acrylate resin, epoxy acrylate resin, cyanate resin, bismaleimide-triazine resin, benzocyclobutene resin, siloxane resin, etc. A thermosetting resin or an ultraviolet curable resin can be used. Moreover, thermoplastic resins, such as an aramid resin, a polystyrene, polyetherimide, polyphenylene ether, thermoplastic polyimide, are mentioned. In addition, those having both a polymerizable group and a carboxyl group are included in “Compound A”.

  In applications where heat resistance is required in the process, among the above resins, resins having a polymerizable group such as thermosetting resins and ultraviolet curable resins are preferable. Moreover, when using the hardened | cured material obtained from a paste for the use as which a light transmittance is requested | required, an epoxy resin, an acrylate resin, an epoxy acrylate resin, a siloxane resin etc. are used suitably.

  These resins forming the matrix can be used alone or in combination of two or more.

  In the paste of the present invention, the preferable content of the compound A, which is a matrix resin, and other matrix resins is preferably 20% by weight or more and 70% by weight or less based on the solid components in the paste. If the combined content of compound A and other matrix resin is 20% by weight or more based on the solid components in the paste, the cured product obtained from the paste becomes tough and cracks are less likely to occur. It is more preferable that the combined content of Compound A and the other matrix resin is 30% by weight or more based on the solid component in the paste because these effects are further increased. When the combined content of compound A and other matrix resin is 70% by weight or less with respect to the solid components in the paste, the refractive index change rate and the linear expansion coefficient due to the temperature of the resulting cured product are further reduced. Can do. It is more preferable that the combined content of compound A and other matrix resin is 50% by weight or less based on the solid component in the paste, since these effects are further enhanced.

  In addition, when light is incident on the matrix resin in which particles are dispersed as described above, Rayleigh scattering of incident light by the particles may occur, which may degrade paste pattern processability and paste cured product light transmittance. . In order to reduce Rayleigh scattering, it is effective to reduce the difference in refractive index between the matrix resin and the particles in the paste, in addition to the method of reducing the number average particle diameter of the inorganic particles.

  Examples of preferable conditions for the compound A or other matrix resin used as the matrix resin when the optical waveguide is produced by curing the paste of the present invention are shown below. An optical waveguide consists of a core part with a large refractive index and a cladding part surrounding the core part, and a refractive index smaller than that of the core part. If the refractive index difference between the core part and the cladding part is large, the light at the bent part of the optical waveguide Signal scattering can be reduced. Since the refractive index of a resin that can be generally used as a matrix resin is about 1.40 to 1.65, the matrix resin used for the core portion has a refractive index of 1.55 to 1.65 on the high refractive index side, and is used for the cladding portion. It is preferable for the above reason to use a matrix resin having a refractive index of 1.45 to 1.55 on the low refractive index side.

  As described above, in order to reduce Rayleigh scattering, it is effective to reduce the difference in refractive index between the matrix resin and the particles in the paste. Therefore, in accordance with the refractive index of the matrix resin, inorganic particles having a refractive index of 1.55 to 1.65 in the core portion, and a refractive index of 1.45 to 1.55 in the cladding portion. It is preferable to use certain inorganic particles. For example, barium sulfate particles having a refractive index of 1.60 are preferably used for the core portion, and silica particles having a refractive index of 1.45 are preferably used for the cladding portion.

  The paste of the present invention preferably contains a polymerization inhibitor. Compound A, Compound B, or other polymerizable group-containing resin in the paste has a polymerizable group, and polymerization proceeds gradually even at room temperature. Therefore, the molecular weight of these resins increases and the viscosity of the paste may increase while the paste is stored. When the viscosity of the paste increases, it may affect the applicability and drying properties of the paste and deteriorate the productivity. Further, since the compound A has a function of improving the dispersibility of the inorganic particles, if the structure of the compound A is changed by polymerization, the dispersibility of the inorganic particles may deteriorate and the inorganic particles may aggregate. Although these phenomena are improved by including Compound B in the paste, the effect is further increased by including a polymerization inhibitor.

  Specific examples of the polymerization inhibitor include phenothiazine, hydroquinone, 2,5-dibutylhydroquinone, N-phenylnaphthylamine, chloranil, hydroquinone monomethyl ether, pyrogallol and the like.

  The content of the polymerization inhibitor in the paste of the present invention is preferably 0.05% by weight or more and 5% by weight or less based on the total amount of Compound A and the other matrix resin. When the content of the polymerization inhibitor with respect to the total amount of the compound A and the other matrix resin in the paste is 0.05% by weight or more, the viscosity of the paste can be maintained in a low state. When the content of the polymerization inhibitor with respect to the total amount of the compound A and the other matrix resin in the paste is 5% by weight or less, the polymerizability of the compound A and the other matrix resin at the time of curing can be improved. The refractive index change rate and the linear expansion coefficient depending on the temperature of the cured product can be further reduced.

  The paste of the present invention preferably contains a silane coupling agent. By containing the silane coupling agent, it is possible to reduce the thinning and peeling of the pattern of the exposed portion in the pattern processing by the photolithography method, and to suppress the generation of cracks, thereby realizing a clear pattern shape. Moreover, the residue of an unexposed part can also be reduced more.

  As silane coupling agents, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyl Trimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyl Triethoxysilane and the like are preferable. Moreover, it is preferable that content of the silane coupling agent in a paste is 0.1 to 10 weight% with respect to a solid component. When the content of the silane coupling agent with respect to the solid component in the paste is 0.1% by weight or more, a sufficient effect by the silane coupling agent can be obtained. Moreover, when the content of the silane coupling agent with respect to the solid component in the paste is 10% by weight or less, the cured product obtained from the paste becomes tough and cracks are hardly generated.

  The paste of the present invention contains (D) an organic solvent. Examples of the organic solvent include N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone, dimethyl sulfoxide, γ-butyrolactone, ethyl lactate, isopropyl alcohol, acetic acid-n-butyl, methyl isobutyl ketone, 1- Examples include methoxy-2-propanol, 1-ethoxy-2-propanol, 4-methyl-2-pentanol, diacetone alcohol, propylene glycol monomethyl ether acetate, and tetrahydrofurfuryl alcohol.

  The paste of the present invention may contain a polymerization initiator. The polymerization initiator has a function of initiating polymerization of the resin by generating active species such as radicals, cations and anions by heat and light. In particular, when a photopolymerization initiator that generates active species by light irradiation is used, pattern processing by a photolithography method becomes possible.

Next, the manufacturing method of the paste of this invention is demonstrated in detail.
Examples of the method for producing the paste include a method in which inorganic particles are dispersed in an organic solvent using a dispersion apparatus, and then the resulting dispersion of inorganic particles is mixed with Compound A and Compound B. Or the method of mixing the commercially available dispersion liquid in which the inorganic particle is disperse | distributing in the organic solvent, the compound A, and the compound B is mentioned.

  First, an example of a method for producing a dispersion in which inorganic particles are dispersed in an organic solvent is shown. Inorganic particles (including secondary particles, aggregated ones), organic solvents, and if necessary, Compound A, Compound B, dispersant, other matrix resin, antifoaming agent, pH adjuster, antioxidant, polymerization Inhibitors, silane coupling agents and the like are mixed in a predetermined amount and stirred so that the liquid becomes uniform.

  Next, the obtained mixed liquid is treated with a dispersing device to disperse the inorganic particles to produce a dispersion of inorganic particles. Examples of the dispersing apparatus include bead mills such as “Ultra Apex Mill” manufactured by Kotobuki Industries Co., Ltd. and “Star Mill” manufactured by Ashizawa Finetech Co., Ltd. The particle diameter of the beads used in the bead mill is preferably 0.01 mm or more and 0.5 mm or less. When the particle diameter of the beads is 0.5 mm or less, since the frequency of contact between the inorganic particles and the beads in the bead mill is high, a sufficient dispersion effect can be obtained. On the other hand, when the particle diameter of the beads is 0.01 mm or more, since the momentum of each bead is large, a shear stress sufficient to disperse the aggregated inorganic particles can be obtained.

  As the material of the beads, ceramic, glass, metal or the like can be used. Specific examples include soda glass, quartz, titania, silicon nitride, silicon carbide, alumina, zirconia, zirconium silicate, steel, and stainless steel. Among these, zirconia beads having particularly high hardness can be preferably used.

  Dispersion by the bead mill may be performed by a single treatment using small beads, or may be performed by changing the size of the beads step by step. For example, first, dispersion treatment may be performed using beads having a particle diameter of 5 mm until the dispersed particle diameter of the inorganic particles reaches about 100 nm, and then dispersion treatment may be performed using finer beads.

  The time spent for the dispersion treatment is appropriately set according to the type and composition ratio of substances constituting the mixed liquid such as inorganic particles and organic solvent. In addition, sampling the mixed solution at regular intervals and measuring the dispersed particle size of the inorganic particles in the mixed solution can grasp the time-dependent change of the dispersion state and can determine the end point of the dispersion process. preferable. As an apparatus for measuring the dispersed particle size of inorganic particles in a mixed liquid, “Zeta Sizer Nano ZS” manufactured by Sysmex Corporation, which is a dynamic light scattering method, can be mentioned.

  Next, a paste is produced by mixing a predetermined amount of necessary substances such as a dispersion of inorganic particles obtained by the above method or a dispersion of commercially available inorganic particles with Compound A, Compound B, and other matrix resins. Here, when compound A and compound B are mixed at the time of manufacturing the dispersion, the dispersion after the dispersion treatment is the paste of the present invention, and the mixture of the other matrix resin and the like is also the paste of the present invention. It is.

  In order to make the paste obtained by mixing a predetermined amount of the dispersion with a resin or the like more uniform, a mixing process using a ball mill or a roll mill can be performed. Also, if air bubbles are mixed in the paste due to the mixing process, leave the solution under a reduced pressure, or remove the air bubbles by using a stirring defoamer, etc., into the cured product produced using the paste. Air bubbles can be avoided.

Next, a method for producing a cured product using the produced paste will be described.
First, the manufactured paste is applied on a substrate, the organic solvent is removed, and a dry film of the paste is produced. As a coating method, screen printing, spray coater, bar coater, blade coater, die coater, spin coater, or the like can be used. Examples of the method for removing the organic solvent include heating with an oven or a hot plate, vacuum drying, heating with an electromagnetic wave such as infrared rays or microwaves, and the like. Here, when the removal of the organic solvent is insufficient, the cured product obtained by the next curing treatment may be in an uncured state or may have poor thermomechanical properties.

  Next, according to the curing mechanism of the compound A or the resin in the used paste, a cured reaction of the paste after drying is performed by heat treatment, light irradiation, or the like, thereby producing a cured product of the paste. In this case, a plurality of treatments may be combined for further curing such as heat treatment after light irradiation. Further, when the heat treatment is performed at 100 ° C. or higher, it is preferable to perform the treatment in an inert atmosphere such as nitrogen because polymerization is not hindered.

  In the present invention, the paste can be applied directly on the substrate as described above to produce a cured product of the paste. However, as shown below, an uncured sheet of paste is prepared in advance and this is applied to the substrate. You may produce the hardened | cured material of a paste by bonding.

  First, the paste produced as described above is applied onto a substrate, the organic solvent is removed, and an uncured sheet is produced. Polyethylene terephthalate (PET) or the like can be used for the base material to which the paste is applied. When it is necessary to peel and remove the PET film as a base material when using an uncured sheet bonded to a substrate such as a silicon wafer, use a PET film whose surface is coated with a release agent such as a silicone resin. When used, the uncured sheet and the PET film can be easily peeled off, which is preferable.

  As a method for applying the paste onto the PET film, screen printing, spray coater, bar coater, blade coater, die coater, spin coater or the like can be used. Examples of the method for removing the organic solvent include heating with an oven or a hot plate, vacuum drying, heating with an electromagnetic wave such as infrared rays or microwaves, and the like. Here, when the removal of the organic solvent is insufficient, the cured product obtained by the next curing treatment may be in an uncured state or may have poor thermomechanical properties.

  The thickness of the PET film is not particularly limited, but is preferably in the range of 30 to 80 μm from the viewpoint of workability. Further, in order to protect the surface of the uncured sheet from dust in the atmosphere, a cover film may be bonded to the surface. When the solid content concentration of the paste is low and an uncured sheet having a desired film thickness cannot be produced, two or more uncured sheets after removal of the organic solvent may be bonded together.

  When pasting the uncured sheet produced by the above method on another substrate, even if using a laminator such as a roll laminator or a vacuum laminator, use a rubber roller on the substrate heated on the hot plate. You may paste together. After bonding to the substrate, the PET film is peeled off after sufficiently cooling, whereby a dry paste film can be formed on the substrate.

  The dried film of the paste obtained by pasting the uncured sheet on the substrate is subjected to heat treatment, light irradiation, etc., and the cured reaction of the paste is advanced to produce a cured product of the paste. In this case, a plurality of treatments may be combined for further curing such as heat treatment after light irradiation. Further, when the heat treatment is performed at 100 ° C. or higher, it is preferable to perform the treatment in an inert atmosphere such as nitrogen because polymerization is not hindered.

  Next, a method for patterning the dry film of the paste manufactured as described above by a photolithography method will be described.

  First, a dry film of the paste is formed on the substrate by a method of applying and drying the paste on the substrate or a method of bonding an uncured sheet onto the substrate. Next, light is irradiated through a mask designed to allow light to pass through only necessary portions corresponding to the pattern. Examples of the light source include an ultrahigh pressure mercury lamp, a metal halide lamp, a halogen lamp, a helium-neon laser, and a YAG laser. Examples of the exposure apparatus include an ultra-high pressure mercury lamp exposure apparatus “PEM-6M” (manufactured by Union Optical Co., Ltd.). When the curing mechanism of the paste of the present invention is radical polymerization, it is preferable to perform an exposure treatment in a nitrogen atmosphere in order to prevent radical active species from being deactivated by oxidation. In order to increase the resolution of the pattern, it is preferable to increase the parallelism of the irradiation light of the exposure apparatus. Further, in order to reduce the influence of the diffracted light by the mask, the mask and the substrate are brought into contact or the mask and the substrate It is preferable to reduce the gap.

  The pattern may become thick due to scattering of the irradiation light inside the paste during exposure. In this case, it is preferable to add an ultraviolet absorber to the paste, because the ultraviolet absorber absorbs the weak light leaking from the exposed portion and suppresses scattering, so that the pattern edge can be kept sharp. The scattering of light inside the paste is largely due to Rayleigh scattering from inorganic particles, and the shorter the wavelength, the greater the scattering. Therefore, an ultraviolet absorber that selectively absorbs light having a short wavelength can also be preferably used. Further, it is possible to suppress scattering by inserting a filter for cutting short wavelength light between the light source and the mask.

  In order to further advance the curing reaction after exposure, the substrate can be stored at room temperature or subjected to heat treatment for a certain period of time. After the exposure processing, the substrate is dipped in a developing solution, the paste not exposed is removed, and the substrate on which the cured product pattern is formed is washed and dried. In order to advance the curing reaction, heat treatment may be further performed.

  Developers used for developing the paste of the present invention include tetramethylammonium hydroxide, diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethylamine, An aqueous solution of a compound exhibiting alkalinity such as dimethylaminoethyl acetate, dimethylaminoethanol, dimethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine, and hexamethylenediamine is preferred.

  The paste or cured product of the present invention is preferably used for an optical waveguide. The optical waveguide is formed on a circuit board such as an electronic device and has a function of transmitting an optical signal between ICs mounted on the board. The optical waveguide includes a core part through which an optical signal propagates and a cladding part having a lower refractive index than the core part surrounding the core part. The structure of the channel type optical waveguide is shown in FIG. 1, and the structure of the slab type optical waveguide is shown in FIG. The channel-type optical waveguide has a structure in which a cladding portion 2 surrounds a linear core portion 1. The slab type optical waveguide has a structure in which the layered cladding portion 2 covers the upper and lower sides of the layered core portion 1. The paste of the present invention may be used for both the core part and the cladding part, or may be used for only one of them.

  Next, the manufacturing method of the optical waveguide using the paste of this invention is demonstrated. First, an uncured sheet for an undercladding part is bonded to a substrate. Bonding may be performed using an apparatus such as a roll laminator or a vacuum laminator, or may be performed manually using a rubber roller on a hot plate. After cooling sufficiently, the PET film is peeled off and heat treatment is performed. Next, the core part uncured sheet is bonded onto the undercladding part by the same method as described above, and then the PET film is peeled off to form the core part. Here, the core part can be processed into an optical waveguide pattern by the following method. When the uncured core portion sheet is polymerized by light irradiation, pattern processing can be performed by a photolithography method. Moreover, when the uncured sheet for the core part is polymerized by heat, pattern processing can be performed by reactive ion etching or the like. Finally, the uncured sheet for the overcladding part is bonded to the upper surface of the core part produced on the undercladding part by the same method as described above, and the PET film is peeled off. An optical waveguide can be formed by thermosetting these.

  The refractive index and thickness of the cladding portion and the core portion of the optical waveguide can be arbitrarily selected depending on the optical waveguide to be designed. In the case of a multimode optical waveguide, it is suitable to increase the refractive index difference between the core part and the cladding part to make the core part thicker. In the case of a single mode optical waveguide, the difference in refractive index between the core portion and the cladding portion is reduced, and the core portion is thinned so that single mode propagation is realized.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
The compounds used in this example are listed below.

<Inorganic particles>
Barium sulfate particles “BF-40” (average primary particle size: 10 nm, manufactured by Sakai Chemical Industry Co., Ltd.)
Barium sulfate particles “BF-20” (average primary particle size: 30 nm, manufactured by Sakai Chemical Industry Co., Ltd.)
Barium sulfate particles “BF-10” (average primary particle size: 60 nm, manufactured by Sakai Chemical Industry Co., Ltd.)
Barium titanate particles “T-BTO-030R” (average primary particle size: 30 nm, manufactured by Toda Kogyo Co., Ltd.)
<Compound A>
・ "HOA-MPL" (manufactured by Kyoeisha Chemical Co., Ltd.)
"Resin A" (compound represented by the following formula (9))

<Compound B>
"Light ester DE" (Chemical name: N, N-diethylaminoethyl methacrylate, manufactured by Kyoeisha Chemical Co., Ltd.)
・ "Light ester DM" (Chemical name: N, N-dimethylaminoethyl methacrylate, manufactured by Kyoeisha Chemical Co., Ltd.)
<Photopolymerization initiator>
・ "IRGACURE 819" (Ciba Japan Co., Ltd.)
<Silane coupling agent>
・ "KBM-503" (chemical name: 3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)
<Dispersion>
Silica particle dispersion “PMA-ST” (number average particle size: 10 nm, concentration: 30% by weight, manufactured by Nissan Chemical Industries, Ltd.)
Moreover, it shows below about what uses the abbreviation among the compounds used in the Example.
THFA: tetrahydrofurfuryl alcohol.

  The measurement method of each characteristic of the paste in which the inorganic particles are dispersed or the cured product obtained from the paste is as follows.

<Measurement method of number average particle diameter of inorganic particles in paste>
The paste was dropped onto the carbon-deposited collodion film, the organic solvent was removed by drying, and the particles were observed with a transmission electron microscope “H-7100FA” (manufactured by Hitachi, Ltd.). The acceleration voltage was 100 kV. The observed image is taken into a computer as a digital image, and the particle diameter is obtained by calculating the particle diameter when approximating the spherical shape of any 100 particles observed with the image processing software “FlvFs” (manufactured by Flobel Co., Ltd.). The particle size was calculated. In addition, when the primary particles were aggregated, the particle diameter as the aggregate was measured.

<Measurement method of viscosity of paste>
It measured at 25 degreeC using the viscometer "RE-115L" (made by Toki Sangyo Co., Ltd.). Measurements were made at 2.5 rpm, 1.0 rpm, and 0.5 rpm, and the average value was calculated.

<Method for measuring linear expansion coefficient of cured product>
On the uncured sheet of 50 μm thick paste placed on a 90 ° C. hot plate, another 50 μm thick uncured sheet was bonded using a rubber roller. Next, using a super high pressure mercury lamp exposure apparatus “PEM-6M” (manufactured by Union Optical Co., Ltd.), the whole line exposure was performed at an exposure amount of 300 mJ / cm ² (wavelength 365 nm conversion), and then the PET film was peeled off in nitrogen. Heated at 200 ° C. for 1 hour to produce a cured product. The obtained cured product was cut into a square having a side of about 5 mm, and several layers were stacked using a TMA measuring device “TMA / SS6100” manufactured by SII NanoTechnology Co., Ltd. Measured. A displacement value was measured when the temperature was raised from room temperature to 120 ° C. in a nitrogen atmosphere with an indentation load of 50 mN, and the temperature was lowered again to room temperature, and the average linear expansion coefficient of the temperature rise and fall from 50 ° C. to 70 ° C. was calculated. In order to remove the temperature history of the linear expansion coefficient, the temperature increase and decrease were repeated twice, and the second measurement result was used as the displacement value.

<Method of insulation reliability test of cured product>
The paste was applied on a copper comb electrode (FIG. 3) having a line and space of 10 μm / 10 μm using the tip of a tweezers and dried at 90 ° C. for 1 hour in the atmosphere. Next, using an ultra-high pressure mercury lamp exposure apparatus “PEM-6M” (manufactured by Union Optics), the entire line was exposed at an exposure dose of 300 mJ / cm ² (wavelength 365 nm conversion), and then heated in nitrogen at 200 ° C. for 1 hour. A sample for evaluation was prepared. Between the electrodes of the obtained sample for evaluation, a voltage of 20 V was continuously applied in an atmosphere at a temperature of 85 ° C. and a relative humidity of 85%, and an insulation reliability test was performed for 1000 hours. The time when the resistance value between the electrodes was less than 10 ⁸ Ω was measured to obtain the insulation resistance holding time. When the resistance value was 1000 hours or more and 10 ⁸ Ω or more, the holding time was 1000 hours. The copper comb electrode includes a chromium under electrode having a thickness of 0.08 μm on a silicon wafer on which a thermal oxide film having a thickness of 0.4 μm and a silicon nitride film having a thickness of 0.8 μm are formed. Further, a copper electrode having a thickness of 10 μm patterned was used.

<Measurement method of light propagation loss of optical waveguide>
It was measured by a cut back method according to the JPCA standard (JPCA-PE02-05-01S-2004). The optical fiber on the incident side and the outgoing side was a multimode type having a core diameter of 50 μm and a numerical aperture of 0.28. The measurement temperature was 23 ° C., and the wavelength of the measurement light source was 850 nm.

Example 1
200 g of barium sulfate particles “BF-40”, 20 g of compound A “HOA-MPL”, 0.2 g of compound B “light ester DE”, 0.2 g of polymerization inhibitor phenothiazine, 220 g of organic solvent THFA, and a particle size of 5 mm A 500 ml plastic container filled with 1 kg of some zirconia beads (manufactured by Nikkato Co., Ltd., YTZ balls) was charged and rotated on a ball mill frame for 24 hours to disperse the barium sulfate particles.

  Subsequently, the above dispersion treated with a ball mill mount was subjected to dispersion treatment using “Ultra Apex Mill UAM-015” (manufactured by Kotobuki Industries Co., Ltd.) which is a bead mill. The material of the beads was zirconia, the particle diameter was 0.05 mm (manufactured by Nikkato Co., Ltd., YTZ ball), and the input amount was 400 g. The peripheral speed of the rotor of the bead mill was 9.5 m / s, and the liquid feeding pressure was 0.1 MPa. Dispersion treatment was performed for 20 hours, and after completion of the dispersion treatment, the liquid was recovered to obtain paste A in which barium sulfate particles were dispersed. The viscosity of the paste A after recovery was 89 mPa · s, and the number average particle diameter of the barium sulfate particles in the paste A was 18 nm.

  The paste A was then stored in a refrigerator (room temperature 5 ° C.) for 3 weeks. Further, the viscosity of the paste A and the number average particle size of the particles in the paste A were measured every week during storage. The evaluation results are shown in Table 2.

  Next, 10 g of paste A that was refrigerated for 3 weeks, 4 g of compound A “resin A”, 0.04 g of compound B “light ester DE”, 0.1 g of photopolymerization initiator “IRGACURE 819”, silane coupling agent “KBM-503” “0.2 g was mixed using a ball mill.

  The paste was applied onto a PET film “SR-1” (thickness 38 μm, manufactured by Otsuchi Industry Co., Ltd.) using a bar coater, dried at 90 ° C. for 15 minutes in the atmosphere, and the film thickness after drying was 50 μm. An uncured sheet was produced. The linear expansion coefficient of the cured product of the paste obtained from the uncured sheet was 39 ppm / ° C.

Moreover, when the insulation reliability test of the hardened | cured material obtained from a paste was done, it continued holding | maintaining resistance value 10 ⁸ ohms or more for 1000 hours or more.

Examples 2-13
With the composition shown in Table 1, a paste in which inorganic particles were dispersed was produced in the same manner as in Example 1 and evaluated during refrigerated storage for 3 weeks. The evaluation results are shown in Table 2. Moreover, each material was mixed so that it might become the composition shown in Table 3 by the method similar to Example 1 using the obtained paste (what was refrigerated storage for 3 weeks), and also the cured | curing material of the paste was produced. The evaluation results are shown in Table 4.

Comparative Examples 1-5
With the composition shown in Table 1, a paste in which inorganic particles were dispersed was produced in the same manner as in Example 1 and evaluated during refrigerated storage for 3 weeks. The evaluation results are shown in Table 2. The viscosity of the paste increased with storage time. Moreover, each material was mixed so that it might become the composition shown in Table 3 by the method similar to Example 1 using the obtained paste (what was refrigerated storage for 3 weeks), and also the cured | curing material of the paste was produced. The evaluation results are shown in Table 4. When the paste was applied, traces of the bar coater remained on the surface of the coating film and did not disappear after drying. Moreover, the linear expansion coefficient was large and the insulation resistance retention time was short.

  In Comparative Example 1, when the paste was used immediately after production without being refrigerated for 3 weeks, the paste coating property was good, the linear expansion coefficient of the cured product was as small as 40 ppm / ° C., and the insulation resistance retention time Also, the insulation reliability was good for 1000 hours or longer. This shows that Compound B improves the storage stability of the paste.

Comparative Example 6
With the composition shown in Table 1, paste S in which inorganic particles were dispersed was produced in the same manner as in Example 1, and evaluated during refrigerated storage for 3 weeks. Here, instead of compound B, triethanolamine, which is an amine having no polymerizable group, was used. The evaluation results are shown in Table 2. Moreover, each material was mixed so that it might become the composition shown in Table 3 by the method similar to Example 1 using the obtained paste S, and also the cured | curing material of the paste was produced. The applicability of the paste was good, but the linear expansion coefficient of the cured product was as large as 73 ppm / ° C., and the insulation resistance retention time was as short as 130 hours.

Example 14
Silica particle dispersion “PMA-ST” 15 g, compound A “resin A” 4 g, compound B “light ester DE” 0.04 g, photopolymerization initiator “IRGACURE 819” 0.1 g, silane coupling agent “KBM-” 503 "0.2g was mixed using the ball mill, and the paste was manufactured.

  The paste was applied onto a PET film “SR-1” (thickness 38 μm, manufactured by Otsuchi Industry Co., Ltd.) using a bar coater, dried at 90 ° C. for 15 minutes in the atmosphere, and the film thickness after drying was 50 μm. An uncured sheet was produced. The linear expansion coefficient of the cured product of the paste obtained from the uncured sheet was 35 ppm / ° C.

Moreover, when the insulation reliability test of the hardened | cured material obtained from a paste was done, it continued holding | maintaining resistance value 10 ⁸ ohms or more for 1000 hours or more.

Comparative Example 7
15 g of silica particle dispersion “PMA-ST”, 4 g of compound A “resin A”, 0.1 g of photopolymerization initiator “IRGACURE 819” and 0.2 g of silane coupling agent “KBM-503” are mixed using a ball mill. To produce a paste. Since the liquid mixture rapidly thickened and gelled, the paste could not be evaluated.

Example 15
10 g of paste A (refrigerated for 3 weeks) obtained in Example 1, 4 g of compound A “resin A”, 0.04 g of compound B “light ester DE”, 0.1 g of photopolymerization initiator “IRGACURE 819” Then, a paste obtained by mixing 0.2 g of silane coupling agent “KBM-503” using a ball mill was applied onto a PET film “SR-1” (thickness 38 μm, manufactured by Otsuchi Industry Co., Ltd.) using a bar coater. And dried in the atmosphere at 90 ° C. for 15 minutes to produce an uncured sheet having a thickness of 50 μm after drying. This was used as the uncured sheet for the core portion of the optical waveguide. Further, the paste obtained in Example 14 was applied onto a PET film “SR-1” using a bar coater, dried in the air at 90 ° C. for 15 minutes, and the film thickness after drying was 10 μm and 60 μm. A cured sheet was produced, which was an uncured sheet for an undercladding part and an uncured sheet for an overcladding part, respectively.

The silicon wafer was heated to 90 ° C. on a hot plate, and an uncured sheet for an undercladding part was bonded using a rubber roller. After sufficiently cooling, the PET film was peeled off. Then, it heated at 200 degreeC in nitrogen for 1 hour for hardening, and the under-cladding part was formed on the board | substrate. Subsequently, the substrate on which the undercladding part was formed was heated on a hot plate to 90 ° C., and the uncured sheet for the core part was bonded using a rubber roller. After sufficiently cooling, the PET film was peeled off. An exposure amount of 50 mJ / cm ² (converted to a wavelength of 365 nm) is passed through a quartz mask using an ultrahigh pressure mercury lamp exposure apparatus (PEM-6M, manufactured by Union Optics Co., Ltd.) on the core portion formed on the under-ladding portion. ). The quartz mask was designed to have a slit portion having a width of 50 μm and a length of 9 cm at a pitch of 250 μm, and to shield light from portions other than the slit portion. The exposed substrate is immersed in a developer “PMER P-7G” (manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 5 minutes to remove the unexposed film, and a core part having a width of 50 μm and a length of 9 cm is formed. Formed. The developed pattern was a clear rectangle, no cracks were generated, no residue was observed in the unexposed areas, and the developability was good.

  Furthermore, in order to form an overcladding part on this, the board | substrate was heated at 90 degreeC on the hotplate, and the uncured sheet | seat for overcladding parts was laminated using the rubber roller. After sufficiently cooling, the PET film was peeled off. For curing, heating was performed in nitrogen at 200 ° C. for 1 hour to obtain an optical waveguide.

  The dicing apparatus was used to cut both ends of the optical waveguide together with the substrate, and the light propagation loss was determined to be 0.1 dB / cm.

Examples 16-17
An uncured sheet for the core part was produced in the same manner as in Example 15 with the composition shown in Table 5 (each paste was refrigerated for 3 weeks). In addition, an optical waveguide was produced in the same manner as in Example 15 using the obtained uncured sheet for core portion. The evaluation results are shown in Table 5. In Example 17 using barium sulfate particles having an average primary particle diameter of 60 nm, the optical propagation loss of the obtained optical waveguide was as large as 3.3 dB / cm. This is considered to be because Rayleigh scattering of incident light is increased by using particles having a large particle diameter. In addition, the width | variety of the core part patterned in Example 17 was 67 micrometers, and the thickness of the pattern was seen. This can also be explained as an increase in Rayleigh scattering of irradiation light during pattern processing.

DESCRIPTION OF SYMBOLS 1 Core part 2 Cladding part 3 Optical signal 4 Copper electrode 5 Silicon wafer

Claims (7)

A paste containing (A) inorganic particles, (B) a compound having a polymerizable group and a carboxyl group, (C) an amine compound having a polymerizable group, and (D) an organic solvent. The paste of Claim 1 in which the amine compound which has the said polymeric group contains the compound represented by following General formula (1).

(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and may be the same or different. N is an integer of 1 to 4.) The paste according to claim 1 or 2, wherein the compound having a polymerizable group and a carboxyl group contains a compound represented by the following general formula (2).

(In the general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a divalent group represented by any one of the following general formulas (3) to (5).)

(In the above general formulas (3) to (5), l and m are each an integer of 1 to 3.) The paste according to any one of claims 1 to 3, wherein the content of the amine compound having a polymerizable group is 0.1 wt% or more and 10 wt% or less with respect to the compound having a polymerizable group and a carboxyl group. The paste in any one of Claims 1-4 whose number average particle diameters of the said inorganic particle are 1 nm or more and 50 nm or less. Furthermore, the paste in any one of Claims 1-5 containing a polymerization inhibitor. An optical waveguide obtained by curing the paste according to claim 1.

Images