JP6734124B2 - Method for producing cured resin film and cured resin film - Google Patents

Description

The present invention relates to a method for producing a cured resin film and a cured resin film.

A cured resin film used in various technical fields may be required to have a small surface roughness depending on the application. For example, a cured resin film for an insulating layer of a flexible printed wiring board or a cured resin film for an insulating substrate in a chip-on-film mounting technique is often required to have a small surface roughness. The demand tends to become stronger as the miniaturization of the wiring formed on the surface of the insulating layer or the insulating substrate progresses.

On the other hand, in recent years, development of fine-grained diamond material called nanodiamond has been promoted. Regarding nanodiamonds, so-called single-digit nanodiamonds having a particle size of 10 nm or less may be required depending on the application. Techniques relating to such nanodiamonds are described in, for example, Patent Document 1 and Patent Document 2 below.

JP, 2005-001983, A JP, 2010-126669, A

Nanodiamonds having a primary particle size of 10 nm or less can exhibit high mechanical strength, high thermal conductivity, etc., as in bulk diamond. Since nanoparticles, which are fine particles, generally have a large proportion of surface atoms (coordinatively unsaturated), the total sum of van der Waals forces that can act between surface atoms of adjacent particles is large and causes aggregation. Cheap. In addition to this, in the case of nanodiamond particles, a phenomenon called agglutination in which Coulomb interaction between crystal faces of adjacent crystallites contributes to form a very strong aggregation may occur. Nanodiamond particles have such a unique property that crystallites or primary particles can interact in a superposed manner. In the conventional technique, the primary particles are dissociated by dissociating the primary particles of nanodiamond. For example, creating a dispersed state in a solvent or a resin material involves technical difficulties. Such low dispersibility in the primary nanodiamond particles is a cause of the low degree of freedom in designing the composite material containing the nanodiamond particles, which is an obstacle to the production of the composite material containing nanodiamonds. There are cases. The low dispersibility of the primary nanodiamond particles may affect the surface smoothness of the resin film containing the nanodiamond particles. The lower the degree of dispersion of nanodiamond particles in the nanodiamond-containing resin film (that is, the higher the degree of aggregation), the rougher the surface of the resin film.

The present invention was devised under the circumstances as described above, and provides a method for producing a cured resin film suitable for obtaining a nanodiamond-containing cured resin film with high surface smoothness, And it aims at providing the cured resin film obtained by this.

According to the first aspect of the present invention, a method for producing a cured resin film is provided. This method for producing a cured resin film includes a first step and a second step. The first step is a curable composition containing at least a component for forming a cured resin (curable resin component), and a nanodiamond organic solvent dispersion liquid containing at least nanodiamond particles having a median diameter of 30 nm or less and an organic solvent. Is a step for obtaining a curable composition containing nanodiamonds. The curable resin component contained in the curable composition provided for the mixing in the first step is a component capable of forming a cured resin, and, for example, a monomer, an oligomer, and a polymer that can be cured by heating or light irradiation. It contains at least one selected from the group consisting of precursors. The curable composition may contain an organic solvent in addition to such a curable resin component. The nanodiamond organic solvent dispersion used for the mixing in the first step is an organic solvent solution in which nanodiamond particles having a median diameter of 30 nm or less are dispersed. Such a nanodiamond organic solvent dispersion is prepared, for example, by a solvent replacement operation in which water as a dispersion medium in a nanodiamond aqueous dispersion in which nanodiamond primary particles are dispersed as colloidal particles is replaced with a desired organic solvent. It is possible. The nanodiamond particles in the nanodiamond organic solvent dispersion liquid include nanodiamond primary particles and/or nanodiamond secondary particles. The nanodiamond primary particles are nanodiamonds having a particle size of 10 nm or less. And the 2nd process of this manufacturing method is a process for hardening after apply|coating the nanodiamond containing curable composition obtained by the 1st process to a base material. The substrate may be separated from the cured resin film after providing the surface on which the cured resin film is formed, or may be integrated with the cured resin film in need of coating with the cured resin film. .. By passing through the second step, a cured resin film is formed on the base material.

In the first step of the present manufacturing method, as described above, the organic solvent solution (nanodiamond organic solvent dispersion liquid) in which the nanodiamond particles having a median diameter of 30 nm or less are dispersed is mixed with the curable composition containing the curable resin component. To be done. At this time, the organic solvent solution in which the nanodiamond particles are dispersed, the curable resin component in the curable composition and the organic solvent, if present, are easily compatible and compatible with each other. Therefore, the mixing in the first step, while avoiding or suppressing the agglomeration of the nanodiamond particles that were well dispersed in the organic solvent solution with a median diameter of 30 nm or less before the mixing, Suitable for preparing a curable composition containing nanodiamonds. In the second step after the first step, a cured resin film is formed from the nanodiamond-containing curable composition. Therefore, in the second step, the nanodiamond particles that were well dispersed in the organic solvent solution with a median diameter of 30 nm or less before the mixing in the first step were avoided or suppressed in the state of aggregation. It is suitable for forming a cured resin film by forming a composite with a cured resin. In addition, the higher the degree of dispersion of the nanodiamond particles in the curable composition containing nanodiamonds, the higher the degree of dispersion of the nanodiamond particles in the curable composition in the second step, which is caused by the non-uniformity of the distribution of the nanodiamond particles. Non-uniformity of the surface tension of the composition is suppressed, convection in the composition due to the non-uniformity of the surface tension is suppressed, the occurrence of convection traces on the surface of the cured resin film formed is suppressed. The Rukoto. The second step as described above is suitable for obtaining a nanodiamond-containing cured resin film having a small surface roughness, that is, a high surface smoothness. In addition, the present inventors have found that a cured resin film in which a cured resin and nanodiamond particles are composited may have a lower surface roughness than a cured resin film made of the cured resin. Found. For example, it is as shown in Examples and Comparative Examples described below. This reduction in surface roughness is due to the fact that the curable composition containing nanodiamonds has a higher viscosity in the course of curing of the composition than the curable composition containing no nanodiamond particles, resulting in convection in the composition. It is thought that this is because the occurrence of irregularities on the surface of the formed cured resin film is suppressed as a result.

As described above, the method for producing a cured resin film according to the first aspect of the present invention is suitable for obtaining a nanodiamond-containing cured resin film with high surface smoothness.

In addition, the cured resin film produced by the present production method contains nanodiamond particles dispersed in the resin film, and the nanodiamond particles contain heat of the cured resin present in the cured resin film. It has the effect of suppressing decomposition and improving the heat resistance of the cured resin film. For example, it is as shown in Examples and Comparative Examples described later. The nanodiamond particles are capable of exhibiting heat resistance without being decomposed even in a high temperature environment of, for example, 400° C., at least one of the surfaces of the nanodiamond particles forming the nanodiamond particles or contained in the nanodiamond particles. It is presumed that sp ² structure carbon is generated in the portion, that is, at least the {111} plane by spontaneous transition from sp ³ structure carbon forming the diamond main body. The presence of this sp ² structured carbon on the surface of the nanodiamond can contribute to capturing and stabilizing radicals generated in the resin material under high temperature environment, and as a result, thermal decomposition of the cured resin due to the action of radicals is suppressed. It is considered to be one.

Therefore, the method for producing a cured resin film according to the first aspect of the present invention is suitable for obtaining a nanodiamond-containing cured resin film that exhibits high heat resistance in addition to high surface smoothness.

The ratio of the content of the nanodiamond particles to the content of the curable resin component and the nanodiamond particles in the nanodiamond-containing curable composition obtained through the above-mentioned first step is preferably 0.001 to 20% by mass. is there. The higher the ratio of the content of the nanodiamond particles, the greater the effect of suppressing the thermal decomposition due to the presence of the nanodiamond particles in the formed cured resin film. From the viewpoint of appropriately exhibiting functions such as insulation in the cured resin film, it may be preferable that the content ratio of the nanodiamond particles is 20% by mass or less.

The above organic solvent is preferably a polar organic solvent. The polar organic solvent is suitable as a dispersion medium for dissolving and dispersing the nanodiamond particles. The polar organic solvent is preferably methanol, ethanol, isopropanol, isobutyl alcohol, ethylene glycol, propylene glycol, glycerin, 2-methoxyethanol, dimethyl sulfoxide, N-methyl-2-pyrrolidone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N,N-dimethylmethoxyacetamide, hexamethylphosphoramide, dimethyl sulfone, γ-butyrolactone, α-acetyl-γ-butyrolactone, From 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, cyclohexanone, tetrahydrofurfuryl acetate, and propylene carbonate At least one selected from the group consisting of

According to the second aspect of the present invention, a cured resin film is provided. This cured resin film contains a cured resin and nanodiamond particles, and has a film surface with a surface roughness (arithmetic mean roughness) Sa of 10 nm or less. The curable resin includes, for example, at least one selected from the group consisting of polyimide resin, epoxy resin, polyurethane resin, phenol resin, melamine resin, urea resin, and polyester resin. The nanodiamond particles include nanodiamond primary particles and/or nanodiamond secondary particles. A cured resin film containing nanodiamond particles and having a surface roughness Sa of 10 nm or less on the surface of the film is appropriately produced by the method for producing a cured resin film according to the first aspect of the present invention. It is possible to The surface roughness (arithmetic mean roughness) Sa can be obtained by measuring the surface shape of the member using a non-contact type surface measurement system utilizing the optical interference method.

In addition, the nanodiamond particles dispersed in the hardened resin film have an effect of suppressing thermal decomposition of the hardened resin present in the hardened resin film and improving the heat resistance of the hardened resin film. For example, it is as shown in Examples and Comparative Examples described later. As described above, the nanodiamond particles can exhibit heat resistance without being decomposed even in a high temperature environment of, for example, 400° C. or less. It is assumed that sp ² structure carbon is generated on at least a part of the surface of, ie, at least the {111} plane by spontaneous transition from sp ³ structure carbon forming the diamond body. The presence of this sp ² structured carbon on the surface of the nanodiamond can contribute to capturing and stabilizing radicals generated in the resin material under high temperature environment, and as a result, thermal decomposition of the cured resin due to the action of radicals is suppressed. It is considered to be one.

Therefore, the cured resin film according to the second aspect of the present invention is suitable for realizing high surface smoothness and high heat resistance.

In the present cured resin film, the ratio of the content of the nanodiamond particles to the content of the cured resin and the nanodiamond particles is preferably 0.001 to 20% by mass. The higher the ratio of the content of the nanodiamond particles, the greater the effect of suppressing the thermal decomposition due to the presence of the nanodiamond particles in the cured resin film. From the viewpoint of appropriately exhibiting functions such as insulation in the cured resin film, it may be preferable that the content ratio of the nanodiamond particles is 20% by mass or less.

In the first and second aspects of the present invention, the nanodiamond particles are preferably nanodiamond particles produced by the detonation method (detonation method nanodiamond particles). According to the detonation method, it is possible to appropriately generate nanodiamonds having a primary particle size of 10 nm or less.

It is process drawing of one Embodiment of the cured resin film manufacturing method which concerns on this invention. It is an expansion schematic diagram of a curable composition obtained through the mixing process shown in FIG. FIG. 2 is an enlarged cross-sectional schematic view of a cured resin film obtained through the film body forming step shown in FIG. 1, which is an embodiment of the cured resin film according to the present invention. 3 is a graph showing the results of thermogravimetric measurement for the resin compositions of Example 1 and Comparative Example 2.

FIG. 1 is a process drawing of an embodiment of a method for producing a cured resin film according to the present invention. The present manufacturing method is a method for manufacturing a nanodiamond-containing cured resin film in which a cured resin and nanodiamond particles are composited, and includes at least a mixing step S1 and a film body forming step S2.

In the mixing step S1, a curable composition containing a component for forming a cured resin and a nanodiamond organic solvent dispersion liquid are mixed to form an ND-containing curable composition which is a nanodiamond-containing curable composition as shown in FIG. This is a process for obtaining the product 10. The ND-containing curable composition 10 contains at least a curable resin component 11, ND particles 12 that are nanodiamond particles, and a solvent 13. The film body forming step S2 is a step for applying the ND-containing curable composition 10 obtained in the mixing step S1 to a substrate and then curing the composition. By passing through the film body forming step S2, the cured resin film 20 as shown in FIG. 3, which is one embodiment of the cured resin film according to the present invention, is formed. The cured resin film 20 contains at least a cured resin 21 and ND particles 12.

The above-mentioned curable composition provided for the mixing in the mixing step S1 contains the curable resin component 11 that is a component for forming the cured resin, and also contains the organic solvent in the present embodiment.

The curable resin component 11 is for forming a cured resin 21 that forms a matrix resin in the cured resin film 20 formed from the ND-containing curable composition 10. The curable resin 21 is, for example, a thermosetting resin that is cured by heating or a photocurable resin that is cured by irradiation with light such as ultraviolet rays. The cured resin 21 preferably contains at least one selected from the group consisting of polyimide resin, epoxy resin, polyurethane resin, phenol resin, melamine resin, urea resin, and polyester resin. By adopting the resin material, it is possible to realize sufficient hardness in the cured resin film 20 manufactured by the present manufacturing method.

The curable resin component 11 specifically includes at least one selected from the group consisting of a monomer, an oligomer, and a polymer precursor for forming the cured resin 21 (in FIG. 2, the curable resin component 11 is (Represented schematically). When a polyimide resin is used as the curable resin 21, the curable resin component 11 contains, for example, a polyamic acid obtained by reacting a tetracarboxylic dianhydride and a diamine as a polymer precursor or a polyimide precursor. The polyamic acid forms a polyimide resin by reacting an adjacent amide group and a carboxy group in a repeating unit to form an imide group-containing ring-closing structure. Examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, and 2,3,5-tricarboxy Cyclopentyl acetic acid dianhydride may be mentioned. Examples of the diamines include oxadianiline, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminophenylmethane, 4,4′-diaminodiphenylsulfone, 1,4-diamino Benzene and 2,5-diaminotoluene are mentioned.

The content of the curable resin component 11 in the above-mentioned curable composition provided for the mixing in the mixing step S1 is, for example, 2 to 30% by mass.

The organic solvent contained in the above-mentioned curable composition provided for the mixing in the mixing step S1 is selected according to the type and composition of the curable resin component 11. Examples of the organic solvent include N-methyl-2-pyrrolidone, γ-butyrolactone, and N,N-dimethylacetamide.

The nanodiamond (ND) organic solvent dispersion liquid used for the mixing in the mixing step S1 is an organic solvent solution in which the ND particles 12 are dispersed, and contains at least the ND particles 12 and an organic solvent. The ND particles 12 include nanodiamond primary particles and/or nanodiamond secondary particles. The median diameter (particle diameter D50) of the ND particles 12 in the ND organic solvent dispersion is 30 nm or less, preferably 25 nm or less, more preferably 20 nm or less, more preferably 15 nm or less, more preferably 13 nm or less, more preferably Is 10 nm or less. The particle diameter D50 of the ND particles 12 can be measured by, for example, a dynamic light scattering method. Moreover, the content of the ND particles 12 in the ND organic solvent dispersion is, for example, 0.5 to 4 mass %.

The ND particles 12 are preferably nanodiamond particles produced by the detonation method (detonation method nanodiamond particles). According to the detonation method, it is possible to appropriately generate nanodiamonds having a primary particle size of 10 nm or less. The detonation nanodiamond particles can be obtained, for example, as follows.

First, explosive is exploded in a closed container. At this time, the explosive used causes partial incomplete combustion to release carbon as a raw material, and nanodiamond is produced by the action of the pressure and energy of the shock wave generated by the explosion. A mixture of trinitrotoluene (TNT) and cyclotrimethylenetrinitroamine or hexogen (RDX) can be used as explosive. The nanodiamond crude product obtained by the detonation method is likely to contain metal oxides. This metal oxide is an oxide of Fe, Co, Ni or the like derived from a container or the like used in the detonation method. For example, the metal oxide can be dissolved and removed from the crude nanodiamond product by applying a predetermined strong acid in an aqueous solvent (acid treatment). The strong acid used in this acid treatment is preferably a mineral acid, and examples thereof include hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, and aqua regia. The crude nanodiamond product obtained by the detonation method contains graphite. This graphite is derived from the carbon that did not form nanodiamond crystals among the carbon released by the partially explosive combustion of the explosive used. For example, after undergoing the above-mentioned acid treatment, graphite can be removed from the crude nanodiamond product by subjecting it to a predetermined oxidizing agent in, for example, an aqueous solvent (oxidation treatment). Examples of the oxidizing agent used in this oxidation treatment include chromic acid, chromic anhydride, dichromic acid, permanganic acid, perchloric acid, salts thereof, and hydrogen peroxide. Detonation nanodiamonds (nanodiamonds produced by the detonation method) are aggregated due to very strong interactions between primary particles even after being refined through the above-mentioned acid treatment and oxidation treatment. It takes the form of agglomerates (secondary particles). By subjecting the suspension obtained by dispersing this aggregate to a predetermined dispersion medium and subjecting it to a crushing treatment, nanodiamonds having a particle size of one digit nanometer can be obtained. The dispersion medium is preferably a solvent in which nanodiamond can exhibit solubility, and examples thereof include water, methanol, ethanol, ethylene glycol, and N-methyl-2-pyrrolidone. The crushing treatment can be performed using, for example, a high shear mixer, a high shear mixer, a homomixer, a ball mill, a bead mill, a high pressure homogenizer, an ultrasonic homogenizer, or a colloid mill. Further, after the crushing treatment, the liquid amount of the suspension in which the nanodiamonds are dispersed is reduced as necessary, whereby a nanodiamond dispersion liquid having a predetermined concentration can be obtained. Alternatively, after the crushing treatment, a liquid part of the nanodiamond is removed from the suspension in which the nanodiamond is dispersed, if necessary, to obtain a nanodiamond powder. The liquid amount reduction and liquid content removal can be performed using, for example, an evaporator or a spray dryer.

The organic solvent contained in the ND organic solvent dispersion liquid used for the mixing in the mixing step S1 is preferably a polar organic solvent. The polar organic solvent is suitable as a dispersion medium for dissolving and dispersing the ND particles 12. The polar organic solvent is preferably methanol, ethanol, isopropanol, isobutyl alcohol, ethylene glycol, propylene glycol, glycerin, 2-methoxyethanol, dimethyl sulfoxide, N-methyl-2-pyrrolidone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N,N-dimethylmethoxyacetamide, hexamethylphosphoramide, dimethyl sulfone, γ-butyrolactone, α-acetyl-γ-butyrolactone, From 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, cyclohexanone, tetrahydrofurfuryl acetate, and propylene carbonate At least one selected from the group consisting of

Regarding the above-mentioned ND organic solvent dispersion liquid containing at least ND particles 12 and an organic solvent, for example, water as a dispersion medium in a nanodiamond water dispersion liquid in which nanodiamond primary particles are dispersed as colloidal particles is a desired organic solvent. It can be prepared by a solvent replacement operation in which For example, the solvent substitution can be promoted by mixing the nanodiamond aqueous dispersion and the organic solvent and then distilling the water from the mixture by a distillation operation.

As described above, the ND-containing curable composition 10 obtained through the mixing step S1 contains at least the curable resin component 11, the ND particles 12 that are nanodiamond particles, and the solvent 13, and the solvent 13 is For example, it is derived from the organic solvent (first organic solvent) in the curable composition and the organic solvent (second organic solvent) in the ND organic solvent dispersion, which are used for the mixing in the mixing step S1. From the viewpoint of avoiding/suppressing the aggregation of the ND particles 12 during the mixing in the mixing step S1, these first and second organic solvents are preferably the same.

The ratio of the content of the ND particles 12 to the total content of the curable resin component 11 and the ND particles 12 in the ND-containing curable composition 10 is preferably 0.001 to 20 mass %. As the ratio of the content of the ND particles 12 is higher, in the formed cured resin film 20, the mechanical strength improving effect due to the presence of the ND particles 12, the thermal conductivity improving effect, the thermal decomposition suppressing effect described later, and the like. However, the lower limit of the content ratio of the ND particles 12 is more preferably 0.01% by mass, and further preferably 1% by mass. From the viewpoint of appropriately expressing the resin characteristics of the cured resin 21 in the cured resin film 20 formed from the ND-containing curable composition 10, the content ratio of the ND particles 12 is 20% by mass or less. It may be preferable. Further, from the viewpoint of enjoying the effect due to the presence of the ND particles 12 in the formed cured resin film 20 with a smaller amount of the ND particles 12, the upper limit of the content ratio of the ND particles 12 is more preferable. Is 10% by mass, more preferably 8% by mass, more preferably 6% by mass.

The ND-containing curable composition 10 may contain other components in addition to the curable resin component 11, the ND particles 12, and the solvent 13. Such other ingredients include, for example, flame retardants, glass fibers, carbon fibers, antistatic agents, lubricants, and colorants.

In the film body forming step S2 after the mixing step S1, the ND-containing curable composition 10 as described above is applied to the substrate and then cured. For example, after applying the ND-containing curable composition 10 on a substrate, the solvent 13 is evaporated from the ND-containing curable composition 10 by heating or the like to form a semi-cured film on the substrate, and The semi-cured film is fully cured by further heating or the like. The base material may be separated from the cured resin film 20 after providing the surface on which the cured resin film is formed, or may be integrated with the cured resin film 20 in need of coating with the cured resin film 20. May be.

As described above, the cured resin film 20 as the nanodiamond-containing cured resin film in which the cured resin 21 and the ND particles 12 are composited can be manufactured.

In the above-mentioned mixing step S1 in the present manufacturing method, the organic solvent solution (nanodiamond organic solvent dispersion liquid) in which the ND particles 12 having a median diameter of 30 nm or less are dispersed is mixed with the curable composition containing the curable resin component 11. .. At this time, the organic solvent solution in which the ND particles 12 are dispersed, and the curable resin component 11 and the organic solvent (the second organic solvent described above) in the curable composition are easily compatible and easily compatible with each other. Therefore, the mixing in the mixing step S1 is performed while avoiding or suppressing the aggregation of the ND particles 12 that were well dispersed in the organic solvent solution with a median diameter of 30 nm or less before the mixing. Suitable for preparing the ND-containing curable composition 10. In the above-mentioned film body forming step S2 after such a mixing step S1, the cured resin film 20 is formed from the ND-containing curable composition 10. Therefore, the film body forming step S2 avoids or suppresses the aggregation of the ND particles 12 which were well dispersed in the organic solvent solution with a median diameter of 30 nm or less before the mixing in the mixing step S1. This is suitable for forming the cured resin film 20 by forming a composite with the cured resin 21 in the state. In addition, the higher the degree of dispersion of the ND particles 12 in the ND-containing curable composition 10, the more uneven the distribution of the ND particles 12 in the course of curing of the composition in the film body forming step S2. The non-uniformity of the surface tension of the composition is suppressed, the convection in the composition due to the non-uniformity of the surface tension is suppressed, and the generation of convection marks on the surface of the formed cured resin film 20. Will be suppressed. The film body forming step S2 as described above is suitable for obtaining the cured resin film 20 having a small surface roughness, that is, a high surface smoothness. In addition, in the case where the cured resin film 20 in which the cured resin 21 and the ND particles 12 are composited has a surface roughness lower than that of the cured resin film made of the cured resin 21. Found that there is. For example, it is as shown in Examples and Comparative Examples described below. This reduction in surface roughness is caused by the fact that the ND-containing curable composition 10 has a higher viscosity in the course of curing of the composition in the film body forming step than the curable composition containing no ND particles 12. It is considered that convection in the composition is suppressed, and as a result, the generation of irregularities on the surface of the formed cured resin film 20 is suppressed.

As described above, the present manufacturing method is suitable for obtaining a nanodiamond-containing cured resin film with high surface smoothness. The surface roughness (arithmetic mean roughness) Sa of the film surface of the nanodiamond-containing cured resin film obtained by the present production method is, for example, 10 nm or less, preferably 7 nm or less, more preferably 5 nm or less, more preferably 3 nm or less, More preferably, it is 2 nm or less. The median diameter (particle diameter D50) of the ND particles 12 in the ND organic solvent dispersion liquid used for the mixing in the mixing step S1 is, as described above, 30 nm or less, preferably 25 nm or less, more preferably 20 nm or less, The thickness is more preferably 15 nm or less, more preferably 13 nm or less, and more preferably 10 nm or less. Such a configuration is suitable for obtaining a nanodiamond-containing cured resin film with high surface smoothness.

In addition, the cured resin film 20 manufactured by the present manufacturing method contains the ND particles 12 dispersed in the resin film, and the ND particles 12 include the cured resin existing in the cured resin film 20. There is an effect of suppressing the thermal decomposition of 21 and improving the heat resistance of the cured resin film 20. For example, it is as shown in Examples and Comparative Examples described later. The ND particles 12 are capable of exhibiting heat resistance without being decomposed even in a high temperature environment of, for example, 400° C., at least one of the surfaces of the nanodiamond primary particles forming the ND particles 12 or contained therein. It is presumed that sp ² structure carbon is generated in the portion, that is, at least the {111} plane by spontaneous transition from sp ³ structure carbon forming the diamond main body. The presence of this sp ² structure carbon on the nanodiamond surface can contribute to capturing and stabilizing radicals generated in the resin material under a high temperature environment, and as a result, thermal decomposition of the cured resin 21 due to the action of radicals is suppressed. It is thought to be done.

Therefore, the above-mentioned method for producing a cured resin film is suitable for obtaining a nanodiamond-containing cured resin film that exhibits high heat resistance in addition to high surface smoothness.

FIG. 3 is an enlarged schematic sectional view of a cured resin film 20 which is an embodiment of the cured resin film according to the present invention. The cured resin film 20 contains at least the cured resin 21 and the ND particles 12 described above, and has a surface roughness (arithmetic mean roughness) Sa of 10 nm or less, preferably 7 nm or less, more preferably 5 nm or less, and more preferably It has a film surface 20a of 3 nm or less, more preferably 2 nm or less.

In the cured resin film 20, the ratio of the content of the ND particles 12 to the total content of the cured resin 21 and the ND particles 12 is preferably 0.001 to 20 mass %. The higher the ratio of the content of the ND particles 12, the higher the mechanical strength of the hardened resin film 20 due to the presence of the ND particles 12 that are the nanodiamond particles, the effect of improving the thermal conductivity, and the effect of suppressing thermal decomposition described below. However, the lower limit of the content ratio of the ND particles 12 is more preferably 0.01% by mass, and further preferably 1% by mass. From the viewpoint of appropriately expressing the resin characteristics of the cured resin 21 in the cured resin film 20, it may be preferable that the content ratio of the ND particles 12 is 20 mass% or less. Further, from the viewpoint of enjoying the effect caused by the presence of the ND particles 12 in the cured resin film 20 with a smaller amount of the ND particles 12, the upper limit of the content ratio of the ND particles 12 is more preferably 10 mass. %, more preferably 8% by mass, more preferably 6% by mass.

The thickness of the cured resin film 20 is, for example, 1 to 50 μm, preferably 5 to 30 μm, and more preferably 5 to 20 μm. The haze value of the cured resin film 20 having such a thickness is, for example, 4% or less, preferably 3% or less, and more preferably 2% or less. The higher the degree of dispersion of the ND particles 12 contained in the cured resin film 20 (that is, the lower the degree of aggregation), the higher the transparency indicated by the haze value of the cured resin film 20 tends to be.

The cured resin film 20 may contain other components in addition to the cured resin 21 and the ND particles 12. Such other ingredients include, for example, flame retardants, glass fibers, carbon fibers, antistatic agents, lubricants, and colorants.

The above-described cured resin film 20 containing the ND particles 12 and having a surface roughness Sa of the film surface 20a with a surface smoothness of 10 nm or less can be appropriately manufactured by, for example, the above-described cured resin film manufacturing method. Is.

In addition, the ND particles 12 dispersed in the cured resin film 20 have an effect of suppressing thermal decomposition of the cured resin 21 existing in the cured resin film 20 and improving heat resistance of the cured resin film 20. .. For example, it is as shown in Examples and Comparative Examples described later. The ND particles 12 are capable of exhibiting heat resistance without being decomposed even in a high temperature environment of, for example, 400° C., at least one of the surfaces of the nanodiamond primary particles forming the ND particles 12 or contained therein. It is presumed that sp ² structure carbon is generated in the portion, that is, at least the {111} plane by spontaneous transition from sp ³ structure carbon forming the diamond main body. The presence of this sp ² structure carbon on the nanodiamond surface can contribute to capturing and stabilizing radicals generated in the resin material under a high temperature environment, and as a result, thermal decomposition of the cured resin 21 due to the action of radicals is suppressed. It is thought to be done.

Therefore, the cured resin film 20 is suitable for achieving high surface smoothness and high heat resistance. Such a cured resin film 20 can be used as, for example, a cured resin film for an insulating layer of a flexible printed wiring board or a cured resin film for an insulating substrate in the chip-on-film mounting technology. Further, the cured resin film 20 can be applied to various optical film materials. In addition, the cured resin film 20 can also be applied to a heat resistant transparent film material having both heat resistance and transparency. Examples of applications of the heat-resistant transparent film material include transparent conductive base materials for touch panels, flexible circuit boards and process papers thereof, base materials for flexible displays, organic EL base materials, and LED lighting base materials.

[Example 1]
The cured resin film of Example 1 was produced through the following mixing process and film forming process.

In the mixing step, 5 g of a polyamic acid solution containing a polyamic acid as a polyimide precursor (trade name “U-imide Varnish CR”, manufactured by Unitika Ltd.) and a nanodiamond NMP dispersion liquid as a nanodiamond organic solvent dispersion liquid ((tradename 2.4 g of "Vox D in NMP", manufactured by Carbodeon Co., Ltd. was mixed. % By mass, and the viscosity is 5 Pa·s Regarding the nanodiamond NMP dispersion liquid used for mixing, the solvent is N-methyl-2-pyrrolidone, the solid content concentration or nanodiamond concentration is 2% by mass, The particle diameter D50 (median diameter) of the nanodiamond particles is 12.4 nm.In this step, while the polyamic acid solution is being stirred, the nanodiamond NMP dispersion liquid is added by a dropping operation to the polyamic acid and the nanodiamond particles. The polyamic acid solution and the nanodiamond NMP dispersion liquid were mixed in such an amount ratio that the ratio of the content of the nanodiamond particles to the total content of the above was 5% by mass. A nanodiamond-containing curable composition (curable composition E1′) containing nanodiamond particles and NMP as a solvent was obtained.

In the film body forming step, a cured resin film was formed from the curable composition E1′ obtained as described above. First, using a squeegee, the curable composition E1′ was applied on a glass plate with a predetermined thickness. And the said glass plate in which the coating film of curable composition E1' was formed was put into the muffle furnace, and baking processing was carried out in nitrogen atmosphere. Specifically, first, heating is performed at 130° C. for 10 minutes (semi-cured film forming step), then temperature is increased from 130° C. to 340° C. over 120 minutes, and then heating is performed at 340° C. for 60 minutes. Was performed (main curing step). In the semi-cured film forming step, NMP as a solvent is mainly evaporated. In the main curing step, a reaction between polyamic acids mainly proceeds to form a polyimide resin. As described above, the cured resin film of Example 1 containing the polyimide resin and the nanodiamond particles (cured resin film E1, thickness 20 μm) was prepared.

[Comparative Example 1]
The mixing step was performed in the same manner as the mixing step of Example 1 except that 2.4 g of another nanodiamond-containing solution was used instead of 2.4 g of the nanodiamond NMP dispersion liquid used in Example 1. The nanodiamond-containing solution used for mixing was a slurry obtained by mixing nanodiamond powder (trade name “Vox P”, manufactured by Carbodeon) and N-methyl-2-pyrrolidone (manufactured by Kishida Chemical Co., Ltd.). It was subjected to ultrasonic crushing treatment for 2 hours using an ultrasonic homogenizer. In this nanodiamond-containing solution, the solvent is N-methyl-2-pyrrolidone, the solid content concentration to the nanodiamond concentration is 2% by mass, and the particle diameter D50 (median diameter) of the nanodiamond particles is 117 nm. In this step, while the polyamic acid solution is being stirred, the nanodiamond-containing solution is added thereto by a dropping operation, and the ratio of the content of the nanodiamond particles to the total content of the polyamic acid and the nanodiamond particles is 5% by mass. The polyamic acid solution and the nanodiamond-containing solution were mixed in a quantitative ratio. As described above, a curable composition containing nanodiamonds (curable composition C1′) was obtained. Then, the film body forming step was performed in the same manner as the film body forming step of Example 1 except that the curable composition C1′ was used instead of the curable composition E1′. As described above, a cured resin film of Comparative Example 1 (cured resin film C1, thickness 20 μm) containing a polyimide resin and nanodiamond particles was produced. The particle size D50 of the nanodiamond particles contained in the nanodiamond-containing solution described above in this comparative example was measured by a dynamic light scattering method using a device manufactured by Spectris (trade name "Zetasizer Nano ZS"). It is the value measured by the contact backscattering method).

[Comparative Example 2]
Mixing was carried out in the same manner as in the mixing step of Example 1 except that 2.4 g of N-methyl-2-pyrrolidone (manufactured by Kishida Chemical Co., Ltd.) was used instead of 2.4 g of the nanodiamond NMP dispersion liquid used in Example 1. The process was carried out. As a result, a curable composition containing no nanodiamond particles (curable composition C2′) was obtained. Then, the film body forming step was performed in the same manner as the film body forming step of Example 1 except that the curable composition C2′ was used instead of the curable composition E1′. As described above, a cured resin film (cured resin film C2, thickness 20 μm) of Comparative Example 2 made of polyimide resin was produced.

<Total light transmittance and haze value>
For each cured resin film of Example 1 and Comparative Examples 1 and 2, the total light transmittance (%) and the haze value (%) were measured using "Haze Meter 300A" manufactured by Nippon Denshoku Industries Co., Ltd. .. The total light transmittance was measured according to JIS K 7105. The haze value was measured according to JIS K 7136. The results are listed in Table 1.

<Convection mark>
For each cured resin film of Example 1 and Comparative Examples 1 and 2, the presence or absence of convection marks on the film surface was visually observed. The results are listed in Table 1.

<Surface roughness Sa>
For each cured resin film of Example 1 and Comparative Example 2, the surface roughness (arithmetic mean roughness) Sa of the film surface was obtained. Specifically, the surface shape of the cured resin film in a predetermined measurement area (2500 μm×1880 μm) is measured by using a non-contact type surface shape measurement system VertScan 2.0 (manufactured by Ryoka System Co., Ltd.) using the optical interference method. The measurement was performed, and the surface roughness (arithmetic mean roughness) Sa was calculated based on the measurement result. The results are listed in Table 1. On the other hand, on the film surface of the cured resin film C1 of Comparative Example 1, undulations that are large enough to be visually confirmed are observed, and are significantly more remarkable than the film surfaces of the cured resin film E1 of Example 1 and each cured resin film of Comparative Example 2. It has been confirmed that it has a large surface roughness.

[Thermogravimetric measurement]
Using the thermogravimetric measuring device (trade name “TG-DTA6300”, manufactured by SII Nano Technology Co., Ltd.), the cured resin films of Example 1 and Comparative Example 2 manufactured as described above were air-treated. The amount of weight loss was measured while maintaining at 460° C. in the atmosphere. In this measurement, the weight of the object to be measured when it was held at 460° C. for 10 minutes was taken as the reference weight (initial weight). The result is represented by a line E1 (Example 1) and a line C2 (Comparative Example 2) in the graph of FIG. In the graph of FIG. 4, the horizontal axis represents the time (minutes) that is the holding time at 460° C. of the measurement target, and the vertical axis represents the TG (%) as the weight reduction rate from the reference weight. Reference weight at the time when the cured resin film E1 of Example 1 is held at 460° C. for 60 minutes, that is, at the time when the cured resin film E1 of Example 1 reaches the reference weight for 50 minutes at 460° C. The weight loss rate was 0.35%. Further, at the time when the cured resin film C2 of Comparative Example 2 was held at 460° C. for 60 minutes, that is, at the time when the cured resin film C2 of Comparative Example 2 was held at 460° C. for 50 minutes after reaching the reference weight. The weight loss rate from the standard weight was 4.26%.

[Evaluation]
From the comparison between the haze value of the cured resin film E1 of Example 1 and the haze value of the cured resin film C1 of Comparative Example 1, a median diameter of 30 nm or less was obtained when preparing a curable composition for forming a nanodiamond-containing cured resin film. In Example 1 in which the nanodiamond NMP dispersion liquid in which the nanodiamond particles are dispersed is used, it can be evaluated that the cured resin film E1 was produced in a state in which the highly dispersed state of the nanodiamond particles was maintained. Convection marks were not observed in the cured resin film E1 of Example 1 because the film body forming step was performed in Example 1 while the highly dispersed state of the nanodiamond particles was maintained. This is because convection in the composition coating film was suppressed in the process. On the other hand, the convection traces were observed in the cured resin film C1 of Comparative Example 1 because the film body forming step was performed in Comparative Example 1 in a state where the degree of dispersion of the nanodiamond particles was low. It is thought that this is because the non-uniformity of the distribution of the composition causes the non-uniformity of the surface tension of the composition, and the convection occurred in the composition coating film due to the non-uniformity of the surface tension in the film forming step. To be

From the comparison between the surface roughness Sa of the cured resin film E1 of Example 1 and the surface roughness Sa of the cured resin film C2 of Comparative Example 2, the cured resin film E1 containing nanodiamond particles does not contain nanodiamond particles. It can be seen that higher surface smoothness is realized than that of the cured resin film C2 of Comparative Example 2. The nanodiamond-containing curable composition for forming the cured resin film E1 has a higher composition than the nanodiamond-free curable composition for forming the cured resin film C2 in the film body forming step S2. It is considered that in the course of curing, the viscosity increases and convection in the composition is suppressed, and as a result, the generation of irregularities on the surface of the formed cured resin film is suppressed.

From the results shown in the graph of FIG. 4, the thermal decomposition of the cured resin film E1 of Example 1 in which the nanodiamond particles are dispersed is suppressed more than that of the cured resin film C2 of Comparative Example 2 containing no nanodiamond particles. That is, that is, the heat resistance is high.

S1 mixing step S2 film body forming step 10 ND-containing curable composition (nanodiamond-containing curable composition)
11 Curable resin component 12 ND particles (nanodiamond particles)
13 Solvent 20 Cured Resin Film 21 Cured Resin

Claims (8)

A curable composition containing a curable resin component, and a nanodiamond organic solvent dispersion containing a nanodiamond particle having a median diameter of 15 nm or less and an organic solvent are mixed to obtain a nanodiamond-containing curable composition. Process,
A method for producing a cured resin film, comprising a step of curing the nanodiamond-containing curable composition after applying it to a substrate ,
The organic solvent is a polar organic solvent,
The polar organic solvent may be dimethyl sulfoxide, N-methyl-2-pyrrolidone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N,N-diethylacetamide, N,N. -Dimethylmethoxyacetamide, hexamethylphosphoramide, dimethyl sulfone, γ-butyrolactone, α-acetyl-γ-butyrolactone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 1 , 3-dimethyl-2-imidazolidinone, tetramethylurea, cyclohexanone, tetrahydrofurfuryl acetate, and at least one selected from the group consisting of propylene carbonate,
The ratio of the content of the nanodiamond particles to the total content of the curable resin component and the nanodiamond particles in the nanodiamond-containing curable composition is 0.001 to 20% by mass. .. The method for producing a cured resin film according to claim 1 , wherein the nanodiamond particles are detonation method nanodiamond particles. The method for producing a cured resin film according to claim 1, wherein the polar organic solvent contains N-methyl-2-pyrrolidone. The curable composition containing the curable resin component contains an organic solvent,
The curing according to any one of claims 1 to 3, wherein the organic solvent contains at least one selected from the group consisting of N-methyl-2-pyrrolidone, γ-butyrolactone, and N,N-dimethylacetamide. Resin film manufacturing method. The method for producing a cured resin film according to claim 1, wherein the curable resin component contains a polyamic acid. A cured resin film comprising a cured resin and nanodiamond particles, and having a film surface having a surface roughness Sa of 10 nm or less ,
The cured resin includes a polyimide resin,
The cured resin film, wherein the ratio of the content of the nanodiamond particles to the total content of the cured resin and the nanodiamond particles is 0.001 to 20% by mass . The cured resin film according to claim 6 , wherein the nanodiamond particles are detonation method nanodiamond particles. The cured resin film according to claim 6, wherein the surface roughness Sa of the cured resin film is 2 nm or less.

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