JP5300218B2 - MICROSTRUCTURE, ITS MANUFACTURING METHOD, AND LIQUID DISCHARGE HEAD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin giving photo cation-polymerizable epoxy resin compositions which can form thick films, are quickly cured by the irradiation of light, and can form desired patterns in high resolutions. <P>SOLUTION: The multi-functional epoxy compound represented by the formula (1) [R is a (n+1) valent organic group; (n) is 2 or 3] and having a nucleophilic organic group A having a nucleophilic group except epoxy group, and an epoxy group-containing group B having one epoxy group. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a polyfunctional epoxy compound and an epoxy resin that is a polymer thereof. In particular, the present invention relates to an epoxy resin for forming a novel photocationically polymerizable epoxy resin composition useful for forming a fine structure such as a flow path forming member of an ink jet recording head on a substrate to be processed by a photolithography process. Furthermore, the present invention relates to a microstructure using the epoxy resin composition, a method for manufacturing the same, and a liquid discharge head.

  In recent years, with the development of science and technology, fine structures have been actively developed in the fields of microactuators, electronic devices, optical devices, etc., and various small sensors, microprobes, thin film magnetic heads have been developed. In addition, the practical application of ink jet recording heads has been promoted.

  As a method for manufacturing such a fine structure, various methods such as a stamper, dry etching, and photolithography are used. Among them, the formation of a pattern by photolithography using a photosensitive resin material has an advantage that a desired shape can be easily obtained with high accuracy.

  For the photosensitive resin composition used for such a purpose, a negative photocationically polymerizable epoxy resin composition may be used from the viewpoints of processability, chemical resistance, heat resistance, and the like.

  The production of the microstructure using the photocationically polymerizable epoxy resin is as follows. That is, after uniformly coating on the substrate with a coater or the like, in the exposure / PEB process, a cross-linking reaction via an epoxy group proceeds only in the exposed part, and in the developing process, the developer in the exposed part and the unexposed part The pattern shape is formed by the difference in dissolution rate with respect to.

Such a photo-cationically polymerizable epoxy resin composition is required to have various characteristics when used in the above-mentioned applications. Specifically, it is as follows.
・ Coating properties: In-plane uniformity during coating ・ High solid differentiation: Low viscosity, high solubility (thick film formability of about several tens of μm)
・ Permanent film characteristics: Chemical resistance Excellent mechanical strength (toughness) Adhesion to substrate ・ Photosensitive characteristics: High resolution High dimensional stability High sensitivity Wide process margin ・ Productivity: High industrial productivity that can withstand mass production In the field of liquid discharge heads applied to inkjet recording heads, etc., the photocationically polymerizable epoxy resin is usually bonded to a substrate such as silicon as a discharge port for liquids such as ink and a liquid flow path forming member. Used in the state. The member is always in contact with ink (generally speaking, ink mainly composed of water and in many cases not neutral), and the permanent film characteristics include excellent ink resistance and the like. Liquidity, mechanical strength, and high adhesion are required. In recent years, it has become clear that the shape of the discharge port affects the liquid discharge accuracy, and high photosensitive characteristics are required to accurately form a desired shape.

  So far, various photocationically polymerizable epoxy resin compositions have been proposed to satisfy the above-mentioned characteristics. However, although it is excellent in individual characteristics, it is not always satisfactory from the viewpoint of paralleling the characteristics.

  A general epoxy resin is obtained by a polymerization reaction using an epoxy compound having several epoxy groups as a monomer. Therefore, at the time of polymerization, a plurality of epoxy groups react at once, and proceed while building a disordered three-dimensional structure. In order to improve the coating film properties of the photocationically polymerizable epoxy resin, since it depends on the primary molecular weight of the base resin in the composition, it is desirable to increase the molecular weight of the epoxy resin to improve the characteristics of the coating film. However, as the molecular weight increases, the viscosity of the solution increases remarkably, and the solubility in the solvent often decreases remarkably, and there is a limit in improving the characteristics.

  In addition, in response to these problems, the molecular weight of the epoxy resin is controlled, and at the solution stage, coating is performed with the molecular weight suppressed to the level of an oligomer that can maintain solubility in solvents, and many epoxy groups are crosslinked during curing. The reaction may improve the physical properties of the coating film. However, in this case, it is often difficult to form a thick film of several tens to several hundreds μm from the viewpoint of molecular weight and viscosity.

  On the other hand, unlike a normal linear polymer, a multi-branched polymer is a specific polymer having a large number of branch points in the main chain. Therefore, it has recently attracted attention as a polymer with unknown potential. It has been clarified that it is derived from less entanglement between molecules compared to ordinary polymers, has low solution viscosity, and exhibits high solubility in various solvents.

  Multibranched polymers are classified into dendrimers represented by the following formula (2) and hyperbranched polymers represented by the following formula (3) from the structural form.

  Dendrimer is a polymer having a star structure as shown in Formula (2). However, when synthesizing a dendrimer, a process of repeating protection, binding and deprotection of a monomer from a site serving as a nucleus (core) is required, which is complicated. Therefore, there is a problem in productivity and it is not suitable as a practical material.

  Hyper-branch polymers have been studied in various ways because of their attractive characteristics as described above. Various hyper-branched polymers and methods for producing the same are reported in, for example, Japanese Patent Publication No. 2000-256459, Japanese Patent Publication No. 2001-114825, and the like.

  Japanese Patent Publication No. 2004-331768 discloses an example using a hyperbranched epoxy resin in a photocationically polymerizable epoxy resin composition. Specifically, a hyper-branch type epoxy resin is synthesized by an A2 + B3 type bimolecular reaction of a phenol compound and an epoxy compound as shown in the following formula (38).

Japanese Patent Laid-Open No. 2000-2556459 JP 2001-114825 A JP 2004-331768 A

  However, in general, the hyperbranched polymer obtained by the A2 + B3 type bimolecular reaction may not have a sufficient degree of branching with respect to the degree of unit polymerization and the number of epoxy at the end. Therefore, various characteristics derived from them may not be sufficient when used for the photocationically polymerizable epoxy resin.

  In addition, the hyperbranched polymer obtained by the A2 + B3 type bimolecular reaction has the property that when the molecular chain grows, the molecular chain extends in multiple directions as compared with the AB2 type. In some cases, gelation may occur during polymerization.

  For example, consider an A2 (lower formula (6)) + B3 (lower formula (7)) type monomer and an intermediate (lower formula (8)) in which each molecule undergoes an addition reaction. A in the compound of the formula (6) and A ′ in the compound of the formula (8) are the same, but are distinguished as described above for convenience.

  Regarding the reactivity of each functional group of the above compounds (6), (7), (8), after the stage where the compound (8) is produced to some extent, the compound (8) B ′ reacts with A ′ to form a polymer. It is expected to grow as. However, when B of formula (7) reacts with A ′ of compound (8), the polymerization reaction does not proceed in a fan shape, the molecular chain grows in multiple directions, and gelation occurs during polymerization. There is a possibility. In addition, in the produced polymer, it is difficult to efficiently leave an epoxy group at the terminal. Therefore, when synthesizing a hyperbranched polymer in the A2 + B3 type, it is necessary to design the reactive groups of the two types of monomers strictly from the viewpoint of the reaction rate. There are restrictions on sex.

  The present invention has been made in view of the above, and is capable of forming a thick film, can be rapidly cured by light irradiation, and can form a desired pattern with high resolution. It is providing the epoxy resin which gives an epoxy resin composition. And it is providing the effective precursor of the said epoxy resin. Another object of the present invention is to provide a novel epoxy resin that is excellent in various properties such as chemical resistance, heat resistance, and mechanical strength and that can provide a cured product having high adhesion to the substrate.

  Moreover, it is providing the related inventions, such as the microstructure which consists of the hardened | cured material of the above-mentioned resin composition, and its manufacturing method.

  As a result of intensive studies to solve the above-described problems, the present inventors have invented a novel epoxy compound shown as an example.

An example of the present invention is a fine structure formed on a substrate, and the fine structure includes a polyfunctional epoxy compound represented by the formula (1) as a monomer and A in the formula (1). a polymer that generated by the polymerization reaction only a and B of R and B, hyper having a plurality of epoxy group at the terminal portion of the polymer - the branch type epoxy resin, a cationic photopolymerization initiator Is a cured product of a photocationically polymerizable epoxy resin composition containing

(Where n is 2 or 3, R is an n + 1 valent organic group having an aromatic ring, A is a hydroxyl group directly bonded to the aromatic ring, and B is an epoxy-containing group having one epoxy group) Yes )

  The epoxy resin of this invention has the various characteristics shown below.

  That is, compared to conventional epoxy resins, the solution viscosity is not so high and the solubility in a solvent is high, so that a solution with a high solid content can be adjusted. Therefore, a thick film of several tens to several hundreds of μm can be formed. Becomes easy. Furthermore, compared with the A2 + B3 type hyper-branch epoxy resin, the degree of branching per unit polymerization degree and the number of terminal epoxy are large. Therefore, a dramatic contrast can be imparted to the degree of crosslinking before and after light irradiation, and a desired pattern can be formed with high resolution. Moreover, since the cured product of the photocationically polymerizable epoxy resin has a high degree of crosslinking density, it exhibits high heat resistance, chemical resistance, and mechanical strength. Furthermore, since a hydroxyl group is generated by ring opening of an epoxy group in a large number of AB binding groups present in the resin, excellent adhesion is exhibited.

  Below, the polyfunctional epoxy compound by this invention, an epoxy resin, a photocationic-polymerizable epoxy resin composition, and the formation method of a microstructure using the same are demonstrated.

(1) Description of photocationically polymerizable epoxy resin composition-Hyper-branch type epoxy resin The hyper-branch type epoxy resin has a polyfunctional epoxy compound represented by the formula (1) as a monomer and its epoxy group. It is a polymer produced by a self-polymerization reaction mainly consisting of a bond of a nucleophilic organic group A.

(Where R is an n + 1 valent organic group, n is 2 or 3, A is a nucleophilic organic group other than an epoxy group that can be bonded to an epoxy group, and B is an organic group having one epoxy group)
For example, the case where n = 2 in equation (1) will be described below as an example.
When n = 2, the hyperbranched epoxy resin of the present invention is compared with the A2 + B3 hyperbranched epoxy resin represented by the formula (5), that is, the AB2 represented by the formula (4). It is a hyperbranch type epoxy resin by self-polymerization of type monomers.

  Hereinafter, advantages of the present invention will be described in comparison with the conventional A2 + B3 type.

  For example, a case where A2 (the following formula (6)) + B3 (the following formula (7)) type monomer is subjected to an addition reaction of 7 molecules in comparison with the same composition is considered. At this time, B has an epoxy group. As shown in Table 1, the AB2 type generates 8 terminal groups and 7 branch points, whereas the A2 + B3 type generates only 3 terminal epoxy groups and 3 branch points (Table 1). (A is a nucleophilic organic group, B is a terminal group, AB is a linking group, and black triangles are branch points).

  For this reason, compared to the hyper-branch type epoxy resin obtained by the A2 + B3 type bimolecular reaction, the degree of branching with respect to the unit polymerization degree and the number of epoxy at the terminal site are large, and when used as a photocationically polymerizable epoxy resin, High reactivity. The same applies when n = 3 in equation (1). In addition, the branched chain grows in a fan shape when viewed as a whole molecule, and the epoxy group is located at the end of the molecule, and is considered to be less susceptible to steric hindrance during cationic polymerization. In the case of the A2 + B3 type, after polymerization, a non-epoxy group called A may exist as a terminal group, but in the case of the present invention, this can be effectively prevented.

  For the characteristics of the hyperbranched epoxy resin of the present invention, the structure of the polyfunctional epoxy compound that is the monomer is important. Below, the preferable structural form of a polyfunctional epoxy compound is demonstrated.

  In the polyfunctional epoxy compound, the nucleophilic organic group A of the formula (1) preferably has a higher reactivity with the epoxy group than the reactivity between the epoxy groups, in particular, an aromatic hydroxyl group, a carboxyl group, An aromatic amino group is preferred. In particular, an aromatic hydroxyl group is more preferable from the viewpoint of solvent resistance of the bonding group to be generated. For example, when using a nucleophilic group equivalent to or low in reactivity between epoxy groups, such as an aliphatic hydroxyl group, the probability that the addition reaction between epoxy groups proceeds competitively during the polymerization reaction increases. The expected hyper-branch polymer may not be obtained. In addition, when a nucleophilic group, such as an aliphatic amino group, that is extremely reactive with an epoxy group is used, the reactivity is too high, and it may be difficult to control the molecular weight or storage stability of the polymer. May cause problems with sex.

  As R in the formula (1), various organic groups can be used without any particular limitation. Among these, from the viewpoints of heat resistance and chemical resistance of the polymer and the resin composition, an organic group containing one or more aromatic rings or alicyclic skeletons is preferable. The molecular weight of R is preferably 1000 or less, more preferably 750 or less, and most preferably 500 or less. When the molecular weight of R is large, the epoxy equivalent of the polymer is high, and when used as a photocationically polymerizable epoxy resin, the resolution and reliability may be lowered due to a decrease in the crosslinking density.

  The epoxy-containing group B in the above formula (1) can be used without particular limitation as long as it contains only one epoxy group. For example, the case where B has a structure shown in Formula (40) is mentioned.

  It is important that the number of epoxy groups is one, and the type of epoxy group is preferably a mono- or di-substituted epoxy group from the viewpoint of reactivity. In the case of a di-substituted epoxy, siloxane hexene oxide is preferable. The group (formula (41)) is preferred. In the case of a polysubstituted epoxy group, the reactivity of the epoxy group decreases, and when used as a photocationically polymerizable epoxy resin, resolution and reliability may decrease due to a decrease in crosslink density.

  The molecular weight of the epoxy-containing group B is preferably 500 or less including the epoxy group, more preferably 400 or less, and most preferably 300 or less. When the molecular weight of the epoxy-containing group B is too large, the molecular weight of the entire epoxy compound is increased, the epoxy equivalent of the polymer is increased, and when used as a photocationically polymerizable epoxy resin, due to a decrease in the crosslinking density, Resolution and reliability may be reduced. Specific examples of the structure of the epoxy-containing group B include skeletal formulas (9) to (20) shown in Table 2.

  It is important that the number of epoxy groups in the above formula (1) is 2 or 3, and when there are 4 or more, it is difficult to control the molecular weight at the time of polymerization and may be accompanied by gelation. is there. In the case of one, the molecular chain is linear and the number of terminal epoxy is small, so that the permanent film characteristics of the cured product of the photocationically polymerizable epoxy resin composition are lowered.

  The method for producing the epoxy compound in the above formula (1) is not particularly limited, but for example, two or three epoxy groups in the same molecule and a nucleophilic organic capable of bonding to the epoxy group. It can be synthesized from a compound having one organic group derivable from the group.

  For example, as shown in the formula (39), it can be obtained by deprotecting the diglycidyl compound (B) obtained from the monohydroxyl-protected body (A) of trihydroxybenzene (P in the figure is a protecting group).

  The organic group that can be derived from the nucleophilic organic group described herein is low in reactivity with the epoxy group and nucleophilic under the condition that the epoxy group is not ring-opened and decomposed or the epoxy groups do not react with each other. Anything that can be derived from an organic group can be used without particular limitation. It can be selected depending on the desired nucleophilic organic group and the induction reaction conditions. For example, in Table 3, an aryl benzyl ether group (formula 21), a benzyl ester group (formula 22), and a nitroaryl group (formula 23) that can be derived into a nucleophilic organic group under reducing conditions in which the epoxy group does not open. Can be mentioned. Moreover, aryl silyl ether (Formula 24), aryl tetrahydropyranyl ether (Formula 25) etc. which can be induced | guided | derived to a nucleophilic organic group under the acidic conditions which epoxy groups do not react are mentioned.

  As a method for producing a hyper-branch epoxy resin, a polymerization reaction may be performed after isolating and purifying an epoxy compound, or a polymerization reaction may be performed as it is without performing isolation and formation after the deprotection reaction of the precursor. In particular, when using a nucleophilic organic group highly reactive with an epoxy group (in the case of an epoxy compound having a high self-polymerization property), it may be difficult to isolate and purify, so after the deprotection reaction, It is desirable to carry out the polymerization immediately.

  For example, when the protecting group of the compound (B) is a benzyl group, the benzyl group is eliminated by catalytic hydrogenation at a low temperature as shown in the following formula (26), and the target is put in the reaction system. The monomer is produced. After the deprotection is completed, by raising the reaction temperature, the monomer generated in the system can be self-polymerized as it is to obtain a hyper-branch epoxy resin. At this time, after the deprotection is completed, an amine-containing compound, a quaternary onium salt compound, an amine salt compound, a phosphorus-containing compound, a crown ether complex, or the like is added to the reaction system as a polymerization reaction accelerator. Reaction efficiency can also be improved. In addition, when the reaction reagent used for the deprotection reaction can inhibit the polymerization reaction, it is desirable to perform an operation of removing from the reaction system after the completion of the deprotection reaction, and then perform the polymerization reaction.

  Moreover, as an example of another method, as shown in the following formula (27), a trifunctional phenol compound such as phloroglucinol is reacted with a bi-equivalent amount of epichlorohydrin, and an addition reaction is performed in the system. Subsequent to the cyclization reaction, a polymerization reaction can be performed. As described above, it is possible to produce a hyperbranched epoxy resin without using a protecting group.

  On the other hand, when the reactivity of the nucleophilic organic group with the epoxy group is high, a problem may occur in the storage stability of the resin solution. This is because the nucleophilic organic group remains as it is at the terminal (end opposite to the epoxy group) in the oligomer and polymer. Therefore, it is desirable to change the nucleophilic group to another non-nucleophilic group by reacting the terminal nucleophilic group sealing agent at the end of the polymerization or after adjusting the epoxy resin.

  Further, the hyper-branch type epoxy resin is not limited to a homopolymer consisting of one type of compound as long as it is a compound represented by (1), but is a copolymer using a plurality of types of compounds having different structures. It doesn't matter. Therefore, in order to give various desired properties, it is also possible to create a photocationically polymerizable resin composition that satisfies many properties by copolymerizing various monomers having the corresponding molecular skeleton. Is possible.

  The content of the hyperbranched epoxy resin in the resin composition can be arbitrarily set according to various target characteristics. In particular, it can be preferably used in the range of 10 wt% to 99 wt%, more preferably in the range of 20 wt% to 95 wt%, and further in the range of 30 wt% to 90 wt% with respect to the total weight of the composition. It can be used suitably. When the amount of the hyperbranched epoxy resin added is too small, the effects of the present invention may not be sufficiently exhibited.

  As described above, the synthesized hyperbranched epoxy resin has a lower solution viscosity and higher solubility in a solvent than a conventional epoxy resin, so that a solution with a high solid content can be prepared. Therefore, it is easy to form a thick film of several tens μm to several hundreds μm. Further, the degree of branching per unit polymerization degree and the number of epoxy at the terminal are large. Therefore, when used as a photocationically polymerizable epoxy resin composition, a dramatic contrast can be imparted to the degree of crosslinking before and after light irradiation, and a desired pattern can be formed with high resolution. Moreover, since the cured product of the photocationically polymerizable epoxy resin has a high crosslinking density, it exhibits high heat resistance, chemical resistance, and mechanical strength.

  The obtained hyperbranched epoxy resin can be used as a photocationically polymerizable epoxy resin by using it together with a photocationic polymerization initiator. Various additives can be added.

-Photocationic polymerization initiator As the photocationic polymerization initiator, an onium salt, a borate salt, a triazine compound, an azo compound, a peroxide, or the like, as long as it is a compound that generates a cationic species that shows strong acidity by light irradiation, It can be used without particular limitation. For example, onium salts include iodonium salts, sulfonium salts, diazonium salts, ammonium salts, pyridinium salts, and the like. Examples of the halogen-containing compound include haloalkyl group-containing hydrocarbon compounds, haloalkyl group-containing heterocyclic compounds and the like (halomethyltriazine derivatives and the like). Examples of the diazoketone compound include 1,3-diketo-2-diazo compounds, diazobenzoquinone compounds, diazonaphthoquinone compounds, and examples of the sulfone compounds include β-ketosulfone and β-sulfonylsulfone. Examples of sulfonic acid compounds include alkyl sulfonic acid esters, haloalkyl sulfonic acid esters, aryl sulfonic acid esters, and imino sulfonates. Of these, aromatic sulfonium salts and aromatic iodonium salts are preferably used in terms of sensitivity, stability, reactivity, and solubility. As aromatic sulfonium salts, those commercially available include TPS-102, 103, 105, MDS-103, 105, 205, 305, DTS-102, 103 (above, manufactured by Midori Chemical Co., Ltd.), SP-170, 172 (manufactured by Asahi Denka Kogyo Co., Ltd.). Examples of aromatic iodonium salts include DPI-105, MPI-103, 105, BBI-101, 102, 103, 105 (manufactured by Midori Chemical Co., Ltd.). From these, it is possible to select appropriately according to the exposure wavelength to be used. These polymerization initiators can be used alone or as a mixture of two or more.

  As content in the resin composition of this photocationic polymerization initiator, it can be set as arbitrary addition amounts so that it may become a target sensitivity and a crosslinking density. Among these, the photocationic polymerization initiator can be preferably used in the range of 0.1 wt% to 30 wt% with respect to the epoxy resin, and more preferably used in the range of 0.3 wt% to 20%. It can be used more suitably in the range of 0.5 wt% to 10 wt%. Moreover, a wavelength sensitizer can also be used as needed. For example, SP-100 (Asahi Denka Kogyo Co., Ltd.) may be added and used.

Other additives The photocationically polymerizable epoxy resin composition according to the present invention has an increased crosslinking density, improved coatability, improved water resistance, improved solvent resistance, imparted flexibility, and improved adhesion to the substrate. For the purpose, various additives can be added without particular limitation. It is also possible to add a plurality of them.

  For example, oligomers and polymers other than hyperbranched epoxy resins can be used as regulators for various properties. Specific examples include the following.

Epoxy resin, poly P-hydroxy styrene, poly M-hydroxy styrene, poly 4-hydroxy 2-methyl styrene, poly 4-hydroxy-3-methyl styrene, poly α-methyl P-hydroxy styrene, partially hydrogenated poly P-hydroxy Styrene copolymer, poly (P-hydroxystyrene-α-methyl P-hydroxystyrene) copolymer, poly (P-hydroxystyrene-α-methylstyrene) copolymer, poly (P-hydroxystyrene-styrene) copolymer, poly (P-hydroxystyrene-M-hydroxystyrene) copolymer, poly (P-hydroxystyrene-styrene) copolymer, poly (P-hydroxystyrene-indene) copolymer, poly (P-hydroxystyrene-acrylic acid) copolymer Poly (P-hydroxy) Styrene-methacrylic acid) copolymer, poly (P-hydroxystyrene-methyl acrylate) copolymer, poly (P-hydroxystyrene-acrylic acid-methyl methacrylate) copolymer, poly (P-hydroxystyrene-methyl acrylate) G) copolymer, poly (P-hydroxystyrene-methacrylic acid-methyl methacrylate) copolymer, polymethacrylic acid, polyacrylic acid, poly (acrylic acid-methyl acrylate) copolymer, poly (methacrylic acid-methyl) Methacrylate) copolymer, poly (acrylic acid-maleimide) copolymer, poly (methacrylic acid-maleimide) copolymer, poly (P-hydroxystyrene-acrylic acid-maleimide) copolymer, poly (P-hydroxystyrene) Methacrylic acid-maleimide) Ma - Commercially available hydroxystyrene those described above, such as, are as follows.

UVR-6100, UVR-6105, UVR-6110, UVR-6128, UVR-6200 (manufactured by Union Carbide), Celoxide 2021, Celoxide 2021P, Celoxide 2081, Celoxide 2083, Celoxide 2085, Celoxide 2000, Celoxide 3000, Cycloma-A200, cycloma-M100, cycloma-M101, epolido GT-301, epolido GT-302, epolido GT-401, epolido GT-403, EHPE3150, epolido HD300 (above, Daicel Chemical Industry Co., Ltd.), KRM-2110, KRM-2199 (Asahi Denka Kogyo Co., Ltd.), Epicoat 801, Epicoat 828 (Oka Chemical Shell Epoxy Co., Ltd.), PY-306, 0163, D -022 (above, manufactured by Ciba-Gaigi), KRM-2720, EP-4100, EP-4000, EP-4080, EP-4900, ED-505, ED-506 (above, manufactured by Asahi Denka Kogyo Co., Ltd.), Epolite M -1230, Epolite EHDG-L, Epolite 40E, Epolite 100E, Epolite 200E, Epolite 400E, Epolite 70P, Epolite 200P, Epolite 400P, Epolite 1500NP, Epolite 1600, Epolite 80MF, Epolite 100MF, Epolite 4000, Epolite 300R, Epolite F 1500 (above, manufactured by Kyoeisha Chemical Co., Ltd.), Santo Tote ST0000, YD-716, YH-300, PG-202, PG-207, YD-172, YDPN638 (above, manufactured by Tohto Kasei Co., Ltd.)
These adjusting agents can be used alone or in combination.

  Further, for the purpose of improving coating properties, fluorine-based and nonionic surfactants and adhesion assistants can be used.

  Surfactants can be used without any particular limitation, and specific examples of commercially available products include the following.

FP TOP EF301, EF303, EF352 (manufactured by Toke Products Co., Ltd.), MegaFuck F171, F173, R-30 (manufactured by Dainippon Ink, Inc.), Florad FC430, FC431 (manufactured by Sumitomo 3M), Asahi Guard AG710 , Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (Asahi Glass Co., Ltd.)
The adhesion assistant can be used without particular limitation, and specific examples include the following.

Silane coupling agents Chlorosilanes such as trimethylchlorosilane, dimethylvinylchlorosilane, methyldiphenylchlorosilane, chloromethyldimethylchlorosilane, trimethylmethoxysilane, dimethyldiethoxysilane, methyldimethoxysilane, dimethylvinylethoxysilane, diphenyldimethoxysilane, phenyl Alkoxysilanes such as triethoxysilane, hexamethyldisilazane, N, N′-bis (trimethylsilyl) urea, silazanes such as dimethyltrimethylsilylamine, trimethylsilylimidazole, vinyltrichlorosilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. Silanes, benzotriazole, benzimidazole, indazole, imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzothiazol, 2-mercaptobenzoxazole, urazol, Heterocyclic compounds such as thiouracil, mercaptoimidazole and mercaptopyrimidine, urea such as 1,1-dimethylurea and 1,3-dimethylurea, thiourea compounds and other additives in the resin composition It can be arbitrary according to various characteristics. In particular, it can be preferably used in the range of 0 to 70 wt% with respect to the total weight, more preferably used in the range of 1 wt% to 60 wt%, and further preferably used in the range of 3 wt% to 50 wt%. Can do.

-Coating solvent The photocationic polymerizable epoxy resin composition according to the present invention is used as a solution dissolved in an organic solvent.

  Any organic solvent can be used without particular limitation as long as it dissolves the resin composition uniformly.

  Specific examples thereof include the following.

Ketone solvents such as methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, ether solvents such as ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, ethyl lactate, butyl lactate, ethyl carbito Ester solvents such as -ruacetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, γ-butyllactone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N -Amide solvents such as vinylpyrrolidone and N-methylcaprolactam, hydrocarbon solvents such as cyclohexane, toluene and xylene. These organic solvents can be used alone, but for the purpose of improving solubility and coating properties. 2 types It may be mixed up.

  The solid content concentration of the photocationically polymerizable epoxy resin composition of the present invention can be preferably used in the range of 1 to 95%, more preferably in the range of 5 wt% to 90 wt%, and 10 wt% to It can be used more suitably in the range of 80 wt%. When the solid content concentration is too low, when forming a film thickness of several tens of μm or more, the desired viscosity may not be reached, which may be difficult, and when it is too high, the precipitate is accompanied by the solubility limit. There may be a problem in storage stability such as the generation of water.

(2) Fine structure and manufacturing method thereof Next, the fine structure of the present invention and the manufacturing method thereof will be briefly described with reference to FIGS. 1 and 2.

  FIG. 1 and FIG. 2 are schematic cross sections showing a microstructure and a manufacturing method thereof according to the present invention.

  First, as shown in FIG. 1, a substrate 101 on which a microstructure is formed is prepared. As the material of the substrate 101, silicon, glass, or the like can be used.

  Next, as shown in FIG. 1B, the above-described photocationically polymerizable epoxy resin composition is solvated on the surface of the substrate 101 to form a resin layer 102 of the photocationically polymerizable epoxy resin composition.

  Then, as shown in FIG. 1C, the resin layer 102 is exposed using a mask 103.

  Thereafter, as shown in FIG. 1D, development processing was performed to form a pattern. Then, if necessary, heat treatment is performed to obtain a microstructure 104 of a cured product of the photocationically polymerizable epoxy resin composition.

  As the pattern shape of the fine structure of the present invention, a beautiful rectangular shape or taper shape can be formed by changing the exposure conditions. Further, since the contrast between the exposed part and the unexposed part is high, as shown in FIG. 2A, the edge part (round frame in the figure) 201 has a sharp vertex.

  On the other hand, when a fine structure is formed by the above-described method using a general negative resist instead of the resin composition of the present invention, depending on the exposure conditions and the resist composition, FIG. As shown in (b), the edge portion 201 may have a rounded corner with no angle at the apex.

  The above phenomenon may affect the performance when the fine structure pattern is used for manufacturing a device having a fine structure such as various liquid discharge heads. This will be described with reference to FIG.

  FIG. 3 is a schematic cross-sectional view showing an example of the liquid discharge head of the present invention. The liquid discharge head according to this embodiment includes a substrate 304 on which energy generating elements are formed in two rows at a predetermined pitch. In the substrate 304, a supply port 306 for supplying a liquid is opened between two rows of energy generating elements 305. On the substrate 304, a discharge port 303 that opens above the energy generating element 305 and an individual liquid channel 308 that communicates from the supply port 306 to the discharge port 303 are formed by the discharge port forming member 302.

  FIG. 3A is a schematic cross-sectional view of the vicinity of a discharge port that is an opening for discharging a liquid provided in the liquid discharge head.

  When the fine structure is used as the member 302 that forms the discharge port 303 of the liquid discharge head, the discharge accuracy of the discharged liquid varies depending on the shape of the edge portion (round frame in the figure) 301 of the discharge port 303.

  In recent years, as a result of studies by the present inventors, it has become clear that the more accurate the shape of the edge portion 301 is, the higher the discharge accuracy is. When the photocationically polymerizable epoxy resin composition of the present invention is used, since the edge boundary portion 301 can be formed in an acute angle shape, an ink jet recording head with high ejection accuracy can be created.

  The liquid discharge head of the present invention is manufactured, for example, as shown in FIG.

  FIG. 4 is a cross-sectional view taken at a position perpendicular to the substrate 304 through a-a ′ in FIG. 3, and is a schematic cross-sectional view showing an example of a method for manufacturing a liquid discharge head according to the present invention.

  First, as shown in FIG. 4A, a substrate 304 on which an energy generating element 305 that generates energy used for discharging a liquid is formed is prepared.

  Next, a sacrificial layer 307 is formed on the substrate 304 as shown in FIG. The sacrificial layer can be appropriately selected as long as it can be dissolved and removed later.

  Next, as shown in FIG. 4 (c), the photocationic resin composition of the present invention is dissolved in an appropriate solvent, and a resin layer 102 is formed on the substrate so as to cover the sacrificial layer 307.

  Next, as shown in FIG. 4D, the discharge port forming member 302 is formed by exposing and developing the resin layer.

  Next, as illustrated in FIG. 4E, the supply port 306 is formed from the back surface of the substrate 304.

  Next, as shown in FIG. 4F, the sacrificial layer 307 is removed, the supply port 306 and the discharge port 303 are communicated, and the flow path 308 is formed.

  Examples of the present invention will be described below to explain the present invention in detail.

・ Synthesis of polyfunctional epoxy compounds (Synthesis Example 1)
A compound represented by the formula (28), which is an example of the polyfunctional epoxy compound (1), was synthesized by the following method.

Synthesis Example 1-1 Synthesis of dimethyl 5-benzyloxyisophthalate (31)

  The reaction described in Formula (29) was allowed to proceed as follows.

  In a flask equipped with a stirrer, a reflux condenser, and a thermometer, 25.0 g (112 mmol) of dimethyl 5-hydroxyisophthalate (manufactured by Tokyo Chemical Industry), 100 ml of dehydrated acetonitrile (manufactured by Wako Pure Chemical Industries), and dehydrated dimethylacetamide ( 25 ml of Wako Pure Chemical Industries, Ltd.) was added. To this solution, 22.0 g (159 mmol) of potassium carbonate (manufactured by Kishida Chemical) and 26.5 g (155 mmol) of benzyl bromide (manufactured by Tokyo Chemical Industry) were added. The mixture was stirred for 2 hours under heating and refluxing in a nitrogen atmosphere.

  After cooling the reaction solution to room temperature, potassium carbonate was filtered off and 1N hydrochloric acid was added at 0 ° C. The product was extracted with ethyl acetate, and the extract was washed with saturated brine and dried over anhydrous sodium sulfate. After the solvent was distilled off under reduced pressure, the resulting residue was recrystallized from ethanol to obtain dimethyl 5-benzyloxyisophthalate (31) as colorless needle crystals (32 g, 89%).

1H-NMR (500 MHz, d6-DMSO, δ ppm): 3.86 (s, 6H), 5.21 (s, 2H), 7.33 (t, J = 7.5 Hz, 1H), 7.39 ( t, J1 = 7.0 Hz, J2 = 7.5 Hz, 2H), 7.46 (d, J = 7.0 Hz, 2H), 7.73 (d, J = 1.5 Hz, 2H), 8.05 (T, J = 1.5Hz, 1H)
13C-NMR (500 MHz, d6-DMSO, δ ppm): 52.63 (2C), 69.97, 119.78 (2C), 122.1, 127.73 (2C), 128.12, 128.61 ( 2C), 131.65 (2C), 136.47, 158.73, 165.28 (2C)
IR (KBr): 3008, 2955, 1721, 1597, 1500, 1460, 1438, 1347, 1307, 1248, 1189, 1117, 1081, 1057, 1034, 1086, 897, 878, 790, 758, 733, 692
Synthesis Example 1-2 Synthesis of 5-benzyloxyisophthalic acid dibutene (33)

  The reaction described in Formula (32) was allowed to proceed as follows.

  A flask equipped with a stirrer, a reflux condenser, a Dean-Stark trap, and a thermometer was prepared. To this was added dimethyl 5-benzyloxyisophthalate (31) (10.0 g (33.3 mmol), 3-buten-1-ol (manufactured by Tokyo Chemical Industry) 36.3 g (503.4 mmol), potassium carbonate (xida (Chemical) 45.8 g (331.3 mmol) and 100 ml of dehydrated acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) were added, and the solution was stirred for 2 hours under heating and reflux in a nitrogen atmosphere.

  After cooling the reaction solution to room temperature, potassium carbonate was filtered off and 1N hydrochloric acid was added at 0 ° C. The product was extracted with ethyl acetate, and the extract was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent and unreacted 3-buten-1-ol were distilled off under reduced pressure. By purifying the obtained residue using silica gel column chromatography (silica gel: silica gel 60 (spherical, neutral) manufactured by Nacalai Tesque, Inc., developing solvent: ethyl acetate / cyclohexane = 1/4), 5 -Dibutylene benzyloxyisophthalate (33) was obtained as a colorless oil (11.0 g, 87%).

1H-NMR (500 MHz, d6-DMSO, δ ppm): 2.46 (br-q, J = 6.5 Hz, 4H), 4.32 (t, J = 6.5 Hz, 4H), 5.07 (br -D, J = 10.5 Hz, 2H), 5.15 (br-d, J = 17.0 Hz, 2H), 5.20 (s, 2H), 5.85 (m, 2H), 7.33 (T, J = 7.5 Hz, 1H), 7.39 (t, J = 7.5, 2H), 7.46 (d, J = 7.5 Hz, 2H), 7.71 (d, J = 1.5Hz, 2H), 8.05 (t, J = 1.5Hz, 1H)
13C-NMR (500 MHz, d6-DMSO, δ ppm): 32.70 (2C), 64.17 (2C), 69.98, 117.40 (2C), 119.75 (2C), 122.03, 127 .77 (2C), 128.13, 128.60 (2C), 131.81 (2C), 134.55 (2C), 136.43, 158.67, 164.70 (2C)
IR (neat): 3074, 2958, 1721, 1642, 1596, 1498, 1455, 1380, 1335, 1308, 1334, 1118, 1040, 988, 916, 756, 697
Synthesis Example 1-3 Synthesis of 5-benzyloxyisophthalic acid dibutylene oxide (33)

  The reaction described in Formula (34) was allowed to proceed as follows.

  In a flask equipped with a stirrer, a reflux condenser, and a thermometer, 3.5 g (9.2 mmol) of 5-benzyloxyisophthalic acid dibutene (33), 100 ml of dehydrated chloroform (manufactured by Wako Pure Chemical Industries, Ltd.), m-chloroperoxide 8.9 g (51.6 mmol) of benzoic acid (manufactured by Tokyo Chemical Industry) was added. The solution was stirred for 7 hours under a nitrogen atmosphere.

  The reaction solution was cooled to 0 ° C., stirred at 0 ° C. for 2 hours, the precipitated white solid was filtered off, and 20% aqueous potassium carbonate solution was added at 0 ° C. The product was extracted with ethyl acetate, and the extract was washed with 20% potassium carbonate and saturated brine, and then dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the obtained residue was subjected to silica gel column chromatography (silica gel: silica gel 60 (spherical, neutral) manufactured by Nacalai Tesque, Inc., developing solvent: ethyl acetate / cyclohexane = 1/1). To give 5-benzyloxyisophthalic acid dibutylene oxide (35) as a colorless oil (3.4 g, 88%). The following and FIG. 5, 6 are the measurement results regarding the product.

1H-NMR (500 MHz, d6-DMSO, δ ppm): 1.83 (m, 2H), 1.99 (m, 2H), 2.51 (dd, J ₁ = 3.0 Hz, J ₂ = 5.0 Hz) , 2H), 2.71 (dd, J ₁ = 4.0 Hz, J ₂ = 5.0 Hz, 2H), 3.05 (m, 2H), 4.41 (t, J = 6.0 Hz, 4H) , 5.24 (s, 2H), 7.33 (t, J = 7.5, 1H), (7.39 (t, J = 7.5, 2H), 7.47 (d, J = 7) .5 Hz, 2H), 7.77 (d, J = 1.5 Hz, 2H), 8.09 (t, J = 1.5 Hz, 1H) (see FIG. 5)
13C-NMR (500 MHz, d6-DMSO, δ ppm): 31.49 (2C), 45.97 (2C), 49.27 (2C), 62.62 (2C), 70.00, 119.86 (2C) ), 122.17, 127.81 (2C), 128.15, 128.61 (2C), 131.77, (2C), 136.45, 158.70, 164.75 (2C).
IR (neat): 2994, 2932, 1720, 1596, 1455, 1383, 1336, 1309, 1236, 1119, 1047, 906, 837, 756, 699 (refer to FIG. 6 where T on the vertical axis represents light transmission) rate))
In addition, 5-benzyloxyisophthalic acid dibutylene oxide of the formula (35) is an important intermediate in producing a precursor for obtaining a hyperbranched epoxy resin described later.
Synthesis Example 1-4 Synthesis of 5-hydroxyisophthalic acid dibutylene oxide

  The reaction described in Formula (36) was allowed to proceed as follows.

  To a flask equipped with a stirrer and a thermometer, add 3.3 g (8.0 mmol) of 5-butyloxyisophthalic acid dibutylene oxide (35) obtained in the previous reaction and 100 ml of dehydrated ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.). It was. To this solution, 0.8 g of 20% palladium carbon (43% water-containing product: manufactured by N.E. Chemcat) was added and stirred for 40 minutes in a hydrogen atmosphere.

  The reaction solution was filtered through Celite to remove palladium on carbon, and then the solvent was distilled off under reduced pressure. By purifying the obtained residue using silica gel column chromatography (silica gel: silica gel 60 (spherical, neutral) manufactured by Nacalai Tesque, Inc., developing solvent: ethyl acetate / cyclohexane = 1/1), 5 -Dibutylene oxide hydroxyisophthalate (37) was obtained as a white solid (2.3 g, 89%). The following and FIGS. 7 and 8 (partially enlarged view of FIG. 7) and FIG. 9 show the analysis results regarding the product.

1H-NMR (500 MHz, d6-DMSO, δ ppm): 1.86 (m, 2H), 1.97 (m, 2H), 2.51 (dd, J ₁ = 3.0 Hz, J ₂ = 5.0 Hz) , 2H), 2.72 (dd, J ₁ = 4.0 Hz, J ₂ = 5.0 Hz, 2H), 3.04 (m, 2H), 4.39 (t, J = 6.0 Hz, 4H) 7.57 (d, J = 1.5 Hz, 2H), 7.95 (t, J = 1.5 Hz, 1H), 10.23 (s, 1H) (see FIG. 7)
13C-NMR (500 MHz, d6-DMSO, δ ppm): 31.50 (2C), 45.97 (2C), 49.27 (2C), 62.40 (2C), 120.35 (2C), 120. 52, 131.60 (2C), 157.97, 164.99 (2C)
IR (KBr): 3380, 3069, 2988, 2962, 1716, 1617, 1602, 1491, 1464, 1439, 1392, 1336, 1300, 1237, 1119, 1053, 1014, 980, 898, 841, 753, 670 (FIG. Refer to 8 (T on the vertical axis in the figure is light transmittance))
As described above, a polyfunctional epoxy compound (37) was obtained.

・ Synthesis of hyperbranched epoxy resin (Polymerization example 1)
Using the polyfunctional epoxy compound (37) synthesized in Synthesis Example 1, Polymer 1 was obtained by the following method.

  To a flask equipped with a stirrer and a thermometer, 200 mg of the polyfunctional epoxy compound (37), 100 mg of triphenylphosphine (manufactured by Kishida Chemical) and dehydrated N, N-dimethylacetamide were added and stirred at 120 ° C. for 5 hours.

  After the reaction, the reaction solution was distilled off under reduced pressure to obtain a hyperbranched epoxy resin as polymer 1.

As a result of structural analysis, the polymer was identified as a hyperbranched epoxy resin produced in the following points. FIG. 10 shows the result of H-NMR analysis of the product. Moreover, the result of IR measurement is described below.
[1] The monomer was easily dissolved in ethyl acetate, whereas the polymer was slightly soluble in the same solvent, confirming that the molecular weight had increased.
[2] From the absorption region and peak intensity of the IR spectrum, the formation of hydroxyl groups and ether bonds and the presence of epoxy groups were confirmed.
[3] From the “integrated intensity ratio of phenolic hydroxyl group and hydrogen on the aromatic ring” of H-NMR, in the polymerization reaction, the reaction proceeds between the phenolic hydroxyl group and the epoxy group, not between the epoxy groups. Confirmed that.
Polyfunctional epoxy compound (1): phenolic hydroxyl group / hydrogen on aromatic ring = 1: 3
Polymer 1: phenolic hydroxyl group / hydrogen on aromatic ring = 1: ∞ (phenolic hydroxyl group is hardly detected)
The above estimation is derived from the following. In the polymer in which the reaction has proceeded between the epoxy groups, the phenolic hydroxyl group does not participate in the reaction, so the integrated intensity ratio of the polymer remains at 1: 3. However, when the phenolic hydroxyl group reacts with the epoxy group, the phenolic hydroxyl group is consumed in the polymerization reaction, so the strength ratio of the phenolic hydroxyl group becomes small.

IR (KBr): 3419, 2966, 1725, 1596, 1438, 1337, 1241, 1101, 1047, 998, 891, 845, 756, 721, 692
Photocationically polymerizable epoxy resin composition (Example 1)
The polymer was dissolved in 100 parts of the hyper-branched epoxy resin of Polymerization Example 1, 5.0 parts of a photocationic polymerization initiator (SP170 manufactured by Asahi Denka Co., Ltd.), and 60 parts of a solvent (cyclohexanone), and stirred at room temperature for 12 hours. Then, the photocation polymerizable epoxy resin composition 1 was obtained by filtering using a 0.2 micrometer capsule filter.

-Evaluation of properties Evaluation was made on the coating properties of the photocationically polymerizable epoxy resin composition of Example 1 and the photosensitive properties such as sensitivity and resolution, and the permanent film properties such as solvent resistance, adhesion, and mechanical properties. As a result, good characteristics were shown.

-Microstructure An example of the microstructure and the manufacturing method thereof according to the present invention will be described. In this embodiment, a liquid discharge head will be described as an example of a fine structure.

(Example 2)
Using the photocationically polymerizable epoxy resin composition of Example 1, a liquid discharge head was manufactured by the method shown in FIG.

  A printing test and a reliability test were performed on the liquid discharge head of Example 2 using ink as the discharge liquid. As a result, good printing was obtained, and the durability was sufficient to withstand long-term use.

It is typical sectional drawing which shows an example of the manufacturing method of the microstructure of one Embodiment of this invention. It is a typical sectional view for explaining the fine structure of one embodiment of the present invention. FIG. 2 is a perspective view and a schematic cross-sectional view illustrating an example of a liquid discharge head according to an embodiment of the present invention. It is typical sectional drawing which shows an example of the manufacturing method of the liquid discharge head of one Embodiment of this invention. It is a chart of the result of the H-NMR measurement of the compound obtained in the process of the synthesis example of this invention. It is a chart of the result of IR measurement of the compound obtained in the process of the synthesis example of this invention. It is a chart of the result of the H-NMR measurement of the compound obtained by the synthesis example of this invention. It is the elements on larger scale of FIG. It is a chart of the result of IR measurement of the compound obtained by the synthesis example of this invention. It is a chart of the result of IR measurement of the compound obtained by the polymerization example of this invention.

Explanation of symbols

101, 304 Substrate 102 Resin layer 103 Mask 104 Fine structure 201, 301 Edge portion 302 Discharge port forming member 303 Discharge port 305 Energy generating element

Claims (7)

A microstructure formed on a substrate, wherein the microstructure is a polyfunctional epoxy compound represented by formula (1) as a monomer and is selected from A, R, and B in formula (1) Photo-cationic polymerization comprising a polymer produced by polymerizing only A and B, and comprising a hyper-branch type epoxy resin having a plurality of epoxy groups at the terminal portion of the polymer, and a photo-cationic polymerization initiator A fine structure, which is a cured product of a conductive epoxy resin composition.

(Where n is 2 or 3, R is an n + 1 valent organic group having an aromatic ring, A is a hydroxyl group directly bonded to the aromatic ring, and B is an epoxy-containing group having one epoxy group) Yes ) B in said Formula (1) has a structure shown to following formula (40), The microstructure of Claim 1 characterized by the above-mentioned.
B in said Formula (1) has a structure shown to following formula (41), The microstructure of Claim 1 characterized by the above-mentioned.
A manufacturing method of a fine structure formed on a substrate,
A polymer produced by polymerizing only A and B of A, R and B in formula (1) using the polyfunctional epoxy compound represented by formula (1) as a monomer on the substrate. Forming a layer using a photocationically polymerizable epoxy resin composition comprising a hyper-branch type epoxy resin having a plurality of epoxy groups at a terminal site of the polymer and a photocationic polymerization initiator; ,
Forming a pattern by exposing and developing the layer; and
A method for producing a fine structure characterized by comprising:

(Where n is 2 or 3, R is an n + 1 valent organic group having an aromatic ring, A is a hydroxyl group directly bonded to the aromatic ring, and B is an epoxy-containing group having one epoxy group) Yes ) A liquid discharge head comprising: an energy generating element that generates energy used to discharge liquid; a discharge port for discharging liquid; and a flow path for supplying liquid to the discharge port. ,
The discharge port forming member that forms the discharge port uses a polyfunctional epoxy compound represented by the formula (1) as a monomer, and only A and B are polymerized from A, R, and B in the formula (1). A cured product of a photocationically polymerizable epoxy resin comprising a hyper-branch type epoxy resin having a plurality of epoxy groups at a terminal portion of the polymer and a photocationic polymerization initiator. A liquid discharge head formed.

(Where n is 2 or 3, R is an n + 1 valent organic group having an aromatic ring, A is a hydroxyl group directly bonded to the aromatic ring, and B is an epoxy-containing group having one epoxy group) Yes )   The fine structure according to any one of claims 1 to 3, wherein the molecular weight of R in the formula (1) is 500 or less. The microstructure according to any one of claims 1, 2 , and 6 , wherein the polyfunctional epoxy compound represented by the formula (1) is a compound represented by the following formula (37).