Photocurable resin composition and molded articles containing the same, and electrical components

Abstract

To provide a photocurable resin composition for obtaining molded articles that combine high strength and a low coefficient of thermal expansion. [Solution] A photocurable resin composition that solves the above problem comprises a polyfunctional acrylic resin, silica particles, and a photopolymerization initiator. The polyfunctional acrylic resin contains 20% to 80% by mass of a polycyclic aliphatic acrylic resin and 20% to 80% by mass of an isocyanuric acid type acrylic resin, the 50% average particle diameter of the silica particles is 30 nm or more and less than 1.0 μm, and the amount of silica particles is 60% to less than 80% by mass of the total mass of the photocurable resin composition.

Description

[Technical Field]

[0001] The present invention relates to a photocurable resin composition, a molded article containing the same, and an electrical component. [Background technology]

[0002] In recent years, 3D printing has become known as a method for manufacturing parts and products of various shapes. Among the various printing methods, stereolithography using a photocurable resin composition containing a photocurable resin has the advantage of being able to quickly cure the resin into the desired shape. Various resins have been proposed as photocurable resins for use in stereolithography. For example, it has been proposed to use acrylates having an isocyanuric ring in stereolithography (Patent Document 1).

[0003] In this context, molded bodies produced by stereolithography are sometimes used in combination with metal components. However, resin molded bodies obtained from resin compositions mainly containing resin, as described in Patent Document 1, have a large difference in thermal expansion coefficient compared to metal. Therefore, when resin molded bodies are combined with metal components, problems such as distortion and deformation due to the difference in thermal expansion coefficients, and defects in the joint area, tend to occur.

[0004] On the other hand, as a method to reduce the thermal expansion coefficient of resin molded articles, it has been proposed to add inorganic substances such as inorganic fillers to the resin composition for stereolithography (for example, Patent Documents 2 and 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-70123 [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0282637 [Patent Document 3] Japanese Patent Publication No. 2023-140203 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, when a photocurable resin composition contains a large amount of inorganic filler, although the coefficient of thermal expansion decreases, the amount of resin that binds the inorganic fillers together decreases. As a result, there was a problem that the strength of the resulting molded article tended to decrease. In other words, with conventional technology, it was difficult to achieve both high strength and a low coefficient of thermal expansion in molded articles obtained from photocurable resin compositions.

[0007] The object of the present invention is to provide a molded article that combines high strength and a low coefficient of thermal expansion, a photocurable resin composition for obtaining the same, and an electrical component. [Means for solving the problem]

[0008] The present invention provides the following photocurable resin compositions. [1] A photocurable resin composition comprising a polyfunctional acrylic resin, silica particles, and a photopolymerization initiator, wherein the polyfunctional acrylic resin contains 20% by mass or more and 80% by mass or less of a polycyclic aliphatic acrylic resin, and 20% by mass or more and 80% by mass or less of an isocyanuric acid type acrylic resin, the 50% average particle diameter of the silica particles is 30 nm or more and less than 1.0 μm, and the amount of silica particles is 60% by mass or more and less than 80% by mass of the total mass of the photocurable resin composition. [2] The photocurable resin composition according to [1], wherein the silica particles are surface-treated with a compound having a (meth)acryloyl group. [3] The photocurable resin composition according to [1] or [2], wherein the polycyclic aliphatic acrylic resin is tricyclodecanedimethanol diacrylate. [4] The photocurable resin composition according to any one of [1] to [3], wherein the isocyanuric acid type acrylic resin is a compound represented by the following general formula. [ka] (In the general formula, X 1 , X2 and X 3 each independently represents a linking group having 1 to 20 carbon atoms and may contain oxygen, R 1 and R 2 each independently represents a hydrogen atom or a methyl group, and Y represents a (meth)acryloyl group or a hydroxy group)

[0009] The present invention provides the following molded articles. [5] A molded article containing a cured product of the photocurable resin composition according to any one of [1] to [4] above. [6] The molded article according to [5], comprising a cured product of the photocurable resin composition and a coating layer containing a polycyclic aliphatic type acrylic resin disposed on the cured product.

[0010] The present invention provides an electrical component. [7] An electrical component comprising the molded article according to [5] or [6] above. electrical component.

Advantages of the Invention

[0011] According to the present invention, there are provided a molded article having high strength and a low thermal expansion coefficient, a photocurable resin composition for obtaining the same, and an electrical component.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a photograph when each molded article produced in the second reference example was observed with a scanning electron microscope.

Modes for Carrying Out the Invention

[0013] The photocurable resin composition of the present invention is suitably used in a stereolithography method for producing a molded article by irradiating light. Therefore, hereinafter, the photocurable resin composition will be described by taking the case where the photocurable resin composition is used in the stereolithography method as an example. However, the use of the photocurable resin composition of the present invention is not limited thereto.

[0014] The photocurable resin composition comprises a polyfunctional acrylic resin, silica particles, and a photopolymerization initiator. The photocurable resin composition satisfies the following four conditions (a) to (d). (a) The polyfunctional acrylic resin contains 20% by mass or more and 80% by mass or less of a polycyclic aliphatic acrylic resin. (b) The polyfunctional acrylic resin contains 20% by mass or more and 80% by mass or less of isocyanuric acid type acrylic resin. (c) The average particle size of the silica particles is 30 nm or more and less than 1.0 μm. (d) The amount of silica particles is 60% by mass or more and less than 80% by mass relative to the total mass of the photocurable resin composition.

[0015] The photocurable resin composition of the present invention contains a relatively large number of silica particles, as shown in condition (d). However, in photocurable resin compositions with a large amount of silica particles, the amount of resin that binds the silica particles becomes relatively small. Therefore, conventional photocurable resin compositions have had the problem of producing molded articles with low mechanical strength. In contrast, the photocurable resin composition of the present invention produces molded articles with high mechanical strength (e.g., flexural strength) and low thermal expansion coefficient. The reason for this is not entirely clear, but it is thought to be as follows.

[0016] In the photocurable resin composition of the present invention, as shown in conditions (a) and (b), the polyfunctional acrylic resin contains predetermined amounts of a polycyclic aliphatic acrylic resin and an isocyanuric acid type acrylic resin. When the polycyclic aliphatic acrylic resin and the isocyanuric acid type acrylic resin are combined, they interact to form an acrylic network. Furthermore, as shown in condition (c), when silica particles with an average particle size within a predetermined range are combined, the silica particles are homogeneously dispersed in the acrylic network, efficiently reinforcing the network. Therefore, the strength of the resulting molded article is increased. Also, as shown in (d), since the amount of silica particles is sufficiently large, the thermal expansion coefficient of the molded article is also reduced. The components contained in the photocurable resin composition will be described in detail below.

[0017] (Polyfunctional acrylic resin) In this specification, a polyfunctional acrylic resin means a resin having two or more (meth)acryloyl groups in one molecule. In this specification, (meth)acryloyl means methacryloyl, acryloyl, or both. The same applies to (meth)acrylate.

[0018] As described above, the polyfunctional acrylic resin comprises at least a polycyclic aliphatic acrylic resin and an isocyanuric acid type acrylic resin. To the extent that the objectives and effects of the present invention are not impaired, the polyfunctional acrylic resin may further contain known bifunctional or higher acrylic resins other than polycyclic aliphatic acrylic resins and isocyanuric acid type acrylic resins (for example, pentaerythritol type acrylic resins). However, the total mass of the polycyclic aliphatic acrylic resin and the isocyanuric acid type acrylic resin relative to the total mass of the polyfunctional acrylic resin is 40% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. When the total mass of the polycyclic aliphatic acrylic resin and the isocyanuric acid type acrylic resin is within this range, the amount of the above-mentioned network becomes sufficiently large, and the bending strength of the resulting molded article tends to increase further.

[0019] Furthermore, the total mass of the polyfunctional acrylic resin in the photocurable resin composition is preferably 20% by mass or more and 40% by mass or less, and more preferably 25% by mass or more and 35% by mass or less. When the amount of polyfunctional acrylic resin is 20% by mass or more, it becomes easier to bind silica particles, and the strength of the photocurable resin composition tends to increase further. On the other hand, when the amount of polyfunctional acrylic resin is 40% by mass or less, the amount of silica particles and photopolymerization initiators becomes relatively large, which tends to further lower the thermal expansion coefficient of the cured product (molded article) and improve the photocurability of the photocurable resin.

[0020] • Polycyclic aliphatic acrylic resin In this specification, "polycyclic aliphatic acrylic resin" refers to a resin having a polycyclic aliphatic structure and two or more (meth)acryloyl groups. The polycyclic aliphatic acrylic resin may be a monomer, an oligomer, or a polymer, but considering the viscosity of the photocurable resin composition and its interaction with the isocyanuric acid type acrylic resin described later, it is preferable that it be a monomer. The polyfunctional acrylic resin may contain only one type of polycyclic aliphatic acrylic resin, or it may contain two or more types.

[0021] Here, the number of rings in the polycyclic aliphatic structure should be two or more, but 2 to 5 is preferred, 2 to 4 is more preferred, and 2 or 3 is even more preferred. Examples of polycyclic aliphatic structures include condensed polycyclic cycloalkane structures such as bicycloundecane, tricyclodecane, norbornane, adamantane, and decahydronaphthalene; and spirocyclic cycloalkane structures such as spiro[3,4]octane, spiro[4,4]nonane, and spiro[4,5]decane. Among these, condensed polycyclic cycloalkane structures are preferred, and tricyclodecane structures are more preferred.

[0022] On the other hand, the number of (meth)acryloyl groups may be two or more, but 2 to 6 is preferred, 2 to 4 is more preferred, and 2 or 3 is even more preferred. The (meth)acryloyl groups may be directly bonded to the above polycyclic aliphatic structure, or they may be bonded via linking groups such as alkylene groups or alkylene oxy groups.

[0023] Specific examples of polycyclic aliphatic acrylic resins include tricyclodecanedimethanol di(meth)acrylate, adamantanediol di(meth)acrylate, and adamantanetriol di(meth)acrylate. Among these, tricyclodecanedimethanol di(meth)acrylate is particularly preferred because it readily interacts with isocyanuric acid-type acrylic resins, as described later, to form the aforementioned network.

[0024] The amount of the polycyclic aliphatic acrylic resin may be 20% by mass or more and 80% by mass or less with respect to the total mass of the polyfunctional acrylic resin, and more preferably 30% by mass or more and 70% by mass or less. As described above, when the amount of the polycyclic aliphatic acrylic resin is within this range, the strength of the cured product (molded body) obtained from the photocurable resin composition is likely to increase.

[0025] · Isocyanuric acid type acrylic resin The isocyanuric acid type acrylic resin is a resin having an isocyanuric ring and two or more (meth)acryloyl groups. The isocyanuric acid type acrylic resin may be a monomer, an oligomer, or a polymer, but from the viewpoints of the viscosity of the photocurable resin composition and the interaction with the above polycyclic aliphatic acrylic resin, it is preferably a monomer. The polyfunctional acrylic resin may contain only one kind of isocyanuric acid type acrylic resin or two or more kinds.

[0026] Here, the number of isocyanuric rings possessed by the isocyanuric acid type acrylic resin may be 1 or more, and may be 2 or more, but is usually 1. Also, the number of (meth)acryloyl groups possessed by the isocyanuric acid type acrylic resin may be 2 or more, and is usually 2 or 3, with 3 being preferable. When the isocyanuric acid type acrylic resin has three (meth)acryloyl groups, the isocyanuric acid type acrylic resin is likely to form the above-mentioned network in the cured product, and further the strength of the cured product (molded body) is likely to increase more.

[0027] Examples of the isocyanuric acid type acrylic resin include compounds represented by the following general formula.

Chemical formula

[0028] In the above general formula, R 1 and R 2 Each of these independently represents either a hydrogen atom or a methyl group. 1 and R 2 These may be the same or different. Furthermore, in the above general formula, Y represents a (meth)acryloyl group or a hydroxyl group.

[0029] The isocyanuric acid type acrylic resin may be a synthetic product or a commercially available product. Examples of commercially available isocyanuric acid type acrylic resins having three (meth)acryloyl groups include NK Ester A-9300 and NK Ester A-9300-1CL (both manufactured by Shin Nakamura Chemical Industry Co., Ltd.), and Aronics M-327 (manufactured by Toagosei Co., Ltd.). Examples of commercially available isocyanuric acid type acrylic resins having two (meth)acryloyl groups include Aronics M-215 (manufactured by Toagosei Co., Ltd.). Furthermore, examples of commercially available mixtures of isocyanuric acid type acrylic resins having three (meth)acryloyl groups and isocyanuric acid type acrylic resins having two (meth)acryloyl groups include Aronics M-313 and Aronics M-315 (both manufactured by Toagosei Co., Ltd.).

[0030] Among the isocyanuric acid type acrylic resins, the compound represented by the following formula is particularly preferred because it readily interacts with the polycyclic aliphatic type acrylic resin to form a desired network. [ka]

[0031] The amount of isocyanuric acid-type acrylic resin may be 20% to 80% by mass relative to the total mass of the polyfunctional acrylic resin, and more preferably 30% to 70% by mass. As described above, when the amount of isocyanuric acid-type acrylic resin is within this range, the strength of the cured product (molded article) obtained from the photocurable resin composition tends to increase further.

[0032] (Silica particles) The silica particles may be any particles with a 50% average particle diameter of 30 nm or more and less than 1.0 μm. In this specification, the 50% average particle diameter is defined as the median of the volume particle diameter distribution measured by laser diffraction. However, if the particle diameter is outside the range of the diffraction particle diameter distribution analyzer (less than 30 nm), the average value of the particle diameters measured by randomly selecting 20 particles from a photograph taken with a transmission electron microscope is used. The above 50% average particle diameter is preferably 100 nm or more and 1.0 μm or less, and more preferably 300 nm or more and 800 nm or less. As described above, when the 50% average particle diameter of the silica particles is 30 nm or more and less than 1.0 μm, the silica particles are more easily dispersed homogeneously in the network formed by the polycyclic aliphatic acrylic resin and the isocyanuric acid type acrylic resin, and the mechanical strength (e.g., bending strength) of the resulting molded article is significantly increased. Furthermore, if the 50% average particle diameter of the silica particles is 30 nm or larger, the viscosity of the photocurable resin composition is less likely to increase excessively, even if the amount of silica particles in the photocurable resin composition is 60% by mass or more of the total mass of the photocurable resin composition. Furthermore, from the viewpoint of durability of the edges of the molded object, the 50% average particle diameter of the silica particles is preferably 30 nm to 100 nm, and more preferably 50 nm to 100 nm.

[0033] The shape of the silica particles is not particularly limited as long as it satisfies the above-mentioned 50% average particle diameter. For example, they may be spherical, polygonal, or irregular in shape, but a spherical shape is more preferable from the viewpoint of easily reinforcing the acrylic resin network.

[0034] The specific surface area of ​​silica particles is, for example, 10 m². 2 / g or more 150m 2 It can be less than / g. When the specific surface area of ​​the silica particles is within this range, the contact area with the polyfunctional acrylic resin is sufficiently large, and the strength of the resulting molded article tends to increase. The specific surface area is 20m². 2 / g or more 130m 2 Preferably less than / g, 30m 2 / g or more 100m 2A value of less than / g is more preferable. Specific surface area is a value measured by the BET method using nitrogen.

[0035] Surface area per unit area of ​​silica particles (m²) 2 The amount of oil absorbed per gram is preferably 0.0003 to 0.01 mL. This amount of oil absorbed is a value specified as follows: Add linseed oil dropwise to 2 g of silica particles to be measured and mix. Then, based on the amount of linseed oil when the mixture changes into a paste, calculate the amount of oil absorbed per gram using the following conversion formula. The measurement is performed by adding the linseed oil dropwise, allowing it to blend in. That is, the amount of linseed oil when the mixture changes into a paste is determined by sequentially adding and mixing the linseed oil. (Oil absorption per gram of silica particles) = Amount of linseed oil required to make the mixture into a paste (mL) / Amount of silica particles being measured (g) The calculated oil absorption amount per gram of silica particles is divided by the specific surface area of ​​the silica particles, and the unit area (m²) of the surface area of ​​the silica particles is calculated. 2 Calculate the amount of oil absorbed per unit. Surface area per unit area of ​​silica particles (m²) 2 When the amount of oil absorbed per unit is within the above range, the viscosity tends to fall within the desired range when silica particles are mixed with a polyfunctional acrylic resin.

[0036] Furthermore, when silica particles are dispersed in cyclohexanone in a 1:1 mass ratio, it is also preferable that the I100 / FWHM ratio of the small-angle X-ray scattering spectrum of the dispersion is 300 or less. When the I100 / FWHM ratio of the small-angle X-ray scattering spectrum is 300 or less, the packing efficiency of the silica particles in the resin composition tends to increase. That is, the silica particles are less likely to aggregate and tend to be dispersed uniformly. As a result, the strength of the resulting molded article tends to increase. It is more preferable that the I100 / FWHM ratio of the small-angle X-ray scattering spectrum is 250 or less, even more preferable that it is 100 or less, and particularly preferable that it is 85 or less. The I100 of the small-angle X-ray scattering spectrum represents the scattering intensity at the peak top of the largest peak in the small-angle X-ray scattering spectrum. The FWHM is the width at half the height of the peak. The small-angle X-ray scattering spectrum can be measured, for example, using synchrotron radiation as the X-ray source and R-AXIS as the detector. Furthermore, the measurement is performed with a camera length of 4m from the X-ray source, and the measurement sample (silica particles) is placed inside a quartz tube with a diameter of 1mm.

[0037] Furthermore, the silica particles may be surface-modified with a surface modifier or the like. Examples of surface modifiers include silane coupling agents and silazanes. When the surface of the silica particles is modified with a silane coupling agent, the affinity between the silica particles and the polyfunctional acrylic resin tends to increase, and the dispersibility of the silica particles in the photocurable resin composition improves. As a result, the strength of the molded article of the photocurable resin composition tends to increase even further.

[0038] The type of silane coupling agent is not particularly limited as long as it has affinity with the polyfunctional acrylic resin and silica particles. Examples of silane coupling agents include amino group-containing silane coupling agents such as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and diethoxymethylvinylsilane; (meth)acryloyl group-containing silane coupling agents such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; and 3-isocyanatetopropyltriethoxysilane. These include isocyanate group-containing silane coupling agents such as: epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane; ureido group-containing silane coupling agents such as 3-ureidopropyltriethoxysilane; mercapto group-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane; phenyl group-containing silane coupling agents such as phenyltrimethoxysilane, phenyltriethoxysilane, and dimethoxyphenylmethylsilane; and aminophenyl group-containing silane coupling agents such as aminophenyltrimethoxysilane, aminophenyltriethoxysilane, and dimethoxyaminophenylmethylsilane. Examples of silazanes include hexamethyldisilazane. These can be used individually or in combination of two or more.

[0039] Among the silane coupling agents mentioned above, compounds having a (meth)acryloyl group, i.e., (meth)acryloyl group-containing silane coupling agents, are preferred from the viewpoint of having good affinity with polyfunctional acrylic resins. Furthermore, when a silane coupling agent has a (meth)acryloyl group, the silane coupling agent polymerizes with the aforementioned polyfunctional acrylic resin. Therefore, silica particles treated with the silane coupling agent become more uniformly dispersed within the polyfunctional acrylic resin.

[0040] The amount of silica particles may be 60% by mass or more and less than 80% by mass of the total mass of the photocurable resin composition, and preferably 65% ​​by mass or more and 75% by mass or less. As described above, when the amount of silica particles is within this range, the coefficient of linear expansion of the resulting molded article becomes sufficiently low, and furthermore, the strength of the resulting molded article increases.

[0041] (Photopolymerization initiator) The photopolymerization initiator can be any compound that absorbs light (e.g., ultraviolet light or visible light) irradiated when curing a photocurable resin composition, generates active species, and initiates polymerization of the polyfunctional acrylic resin or the like. The photocurable resin composition may contain only one type of photopolymerization initiator, or it may contain two or more types.

[0042] Examples of photopolymerization initiators include alkylphenone-based radical polymerization initiators, acylphosphine oxide-based radical polymerization initiators, and oxime ester-based radical polymerization initiators. Examples of alkylphenone-based photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxyethoxy-1-{4-[4-(2-hydroxy-2-methyl-propan- Examples of acylphosphine oxide-based photopolymerization initiators include pionyl)-benzyl]phenyl}-2-methyl-propane-1N-phenylglycine-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone. On the other hand, examples of acylphosphine oxide-based photopolymerization initiators include bisphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. Examples of oxime ester-based radical polymerization initiators include 2-benzoyloxyimino-4'-(phenylthio)octanophenone and 6-[1-(acetyloxyimino)ethyl]-9-ethyl-9H-carbazole-3-yl-2-methylphenyl ketone.

[0043] The amount of photopolymerization initiator in the photocurable resin composition is preferably 0.5 parts by mass to 3.0 parts by mass, and more preferably 0.7 parts by mass to 2.0 parts by mass, per 100 parts by mass of the total mass of the acrylic resin (the polyfunctional acrylic resin and other resins having (meth)acryloyl groups). When the amount of the photocurable resin composition is within this range, it is possible to efficiently cure the photocurable resin composition.

[0044] (Other ingredients) The photocurable resin composition may further contain components other than the polyfunctional acrylic resin, silica particles, and photopolymerization initiator, to the extent that it does not impair the objectives and effects of the present invention. Examples of other components include photocurable resins other than polyfunctional acrylic resins (e.g., monofunctional acrylic resins), other curable resins such as epoxy resins, and various additives. Examples of additives include dispersion stabilizers, colorants, UV absorbers, antioxidants, polymerization inhibitors, defoamers, fillers, photosensitizers, toughening agents, and the like.

[0045] (Viscosity of photocurable resin composition) The viscosity of the photocurable resin composition is appropriately selected depending on the type of stereolithography method. For example, in the additive manufacturing method described later, the viscosity of the photocurable resin composition at 25°C is usually preferably between 1 Pa·s and 1000 Pa·s, and more preferably between 10 Pa·s and 800 Pa·s. The above viscosity is measured using a rheometer (e.g., Discovery HR-2 from TA Instruments) at a shear rate of 1 (1 / s), and read after the rotation has stabilized (e.g., after 90 seconds). When the viscosity of the photocurable resin composition is within this range, the fluidity of the photocurable resin composition during stereolithography tends to be appropriate.

[0046] (Method for preparing a photocurable resin composition) The method of preparing the above-mentioned photocurable resin composition is not particularly limited, as long as it is possible to uniformly mix the polyfunctional acrylic resin, silica particles, and photopolymerization initiator, as well as other components as needed. For example, all components may be mixed at once. Alternatively, the polyfunctional acrylic resin and photopolymerization initiator may be mixed first, and then the silica particles and other components may be mixed. The mixing method can be the same as known stirring or kneading methods.

[0047] (Stereolithography method using photocurable resin composition) The above-mentioned photocurable resin composition can be used in various stereolithography methods, but one example is the following additive manufacturing method.

[0048] In this method, a photocurable resin composition is supplied onto a stage to form a layer (first layer) of a desired thickness made of the photocurable resin composition. At this time, the method of supplying the photocurable resin composition is not particularly limited, and for example, a method using a T-die can be used. The surface of the photocurable resin composition supplied from the T-die may be smoothed with a squeegee or doctor knife as needed. Then, a predetermined area of ​​the first layer made of the photocurable resin composition is irradiated with light to cure the photocurable resin composition in the irradiated area. The method of light irradiation is not particularly limited, and for example, laser light may be scanned, or the area may be exposed all at once through a mask or the like. At this time, the wavelength of the light to be irradiated is not particularly limited and is appropriately selected according to the type of photopolymerization initiator described above, but for example, light with a wavelength of 100 nm to 400 nm is preferred.

[0049] Further, a photocurable resin composition is supplied onto the first layer of cured material to form a layer of a desired thickness (second layer). Then, light is irradiated onto a desired area of ​​the second layer in the same manner as above to cure the photocurable resin composition. By repeating these steps, a molded article containing the cured product of the photocurable resin composition is obtained.

[0050] Furthermore, after or during the production of the molded body, heat treatment may be performed as needed to accelerate the curing of the photocurable resin composition.

[0051] (Uses of molded products) Molded articles containing the cured product of the above-mentioned photocurable resin composition have high mechanical strength and low thermal expansion coefficient, as described above. Therefore, they can be used in a variety of applications, including electrical components, electronic equipment, medical equipment, electrical appliances, robot-related products, and vehicle-related products. Among these, they are particularly useful in the manufacture of electrical components, where composite parts are often produced by combining the molded article with metal.

[0052] (First variation) The above describes a method for manufacturing a molded article using a photocurable resin composition containing a relatively large amount of silica particles. However, when a molded article is manufactured using a photocurable resin composition containing a relatively large amount of inorganic particles, the inorganic particles tend to be exposed on the surface of the molded article. Therefore, when the molded article comes into contact with other components, the inorganic particles may fall off. Conventionally, it is known to provide a coating layer on the surface of the molded article to suppress such detachment of inorganic particles. However, when inorganic particles are exposed on the surface of the molded article, the adhesion with the coating layer, which is mainly made of resin, is low, and the durability of the coating layer cannot be sufficiently obtained.

[0053] In contrast, the inventors have found that by providing a molded body comprising an acrylic resin and inorganic particles having a 50% average particle diameter of 30 nm or more and less than 1.0 μm (preferably 0.1 μm or more and less than 1.0 μm), wherein the inorganic particle content is 60% by mass or more and less than 80% by mass, and a coating layer disposed on the base material, which contains the same type of acrylic resin as the acrylic resin in the base material, the adhesion between the base material and the coating layer is significantly improved, and the durability of the coating layer is enhanced. It should be noted that the acrylic resin contained in the base material and the acrylic resin contained in the coating layer do not need to be completely identical. For example, if the base material contains multiple acrylic resins, the coating layer may contain at least one of these acrylic resins. The reverse is also possible.

[0054] In a molded article containing the above-mentioned base material and coating layer, the reason for the increased durability of the coating layer is not entirely clear, but it is thought to be as follows: Since the base material contains 60% or more by mass of inorganic particles, the inorganic particles are easily exposed on the surface of the base material. At this time, since the 50% average particle diameter of the inorganic particles is 30 nm or more and less than 1.0 μm (preferably 0.1 μm or more and less than 1.0 μm), an appropriate level of unevenness is formed on the surface of the base material. As a result, an appropriate anchoring effect is generated between the base material and the coating layer. In addition, since the acrylic resin contained in the base material and the acrylic resin contained in the coating layer are of the same type, they have high affinity for each other. It is thought that the anchoring effect due to the unevenness and the affinity between the acrylic resins work synergistically to increase the durability of the coating layer.

[0055] The type of inorganic particles contained in the base material is not particularly limited, but it is preferable that they be silica particles as described in the above-mentioned photocurable resin composition, from the viewpoint of hardness, handling, etc. Similarly, the type of acrylic resin contained in the base material is not particularly limited, but it is preferable that it be a polyfunctional acrylic resin (polycyclic aliphatic acrylic resin and isocyanuric acid type acrylic resin) as described in the photocurable resin composition, from the viewpoint of the strength of the resulting molded article, etc. In other words, it is preferable that the base material is a cured product of the above-mentioned photocurable resin composition.

[0056] On the other hand, the coating layer is preferably a layer containing the polycyclic aliphatic acrylic resin described above. Such a coating layer can be obtained, for example, by applying a resin composition for a coating layer containing the polycyclic aliphatic acrylic resin and the photopolymerization initiator described above onto a base material and curing it. The amount of photopolymerization initiator in the coating layer composition is preferably 0.5 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the total amount of acrylic resin (polycyclic aliphatic acrylic resin and other resins having (meth)acryloyl groups). Furthermore, the coating layer composition may contain other components as needed, for example, isocyanuric acid type acrylic resin, other resins, various additives, etc.

[0057] The method for applying the resin composition for the coating layer is appropriately selected according to the shape of the base material and the desired film thickness. For example, known application methods and printing methods such as brush application, inkjet application, spray application, spin coating, and dipping can be used.

[0058] The curing method for the coating layer composition is not particularly limited; for example, it may be performed by scanning with laser light or by simultaneous exposure. In this case, the wavelength of the light used for irradiation should be any wavelength capable of exciting the photopolymerization initiator and generating active species, and should be appropriately selected according to the type of photopolymerization initiator described above, but light with a wavelength of 100 nm to 400 nm is preferred.

[0059] (Second variation) In the above description of the photocurable resin composition, silica particles were used as fillers. However, depending on the application of the photocurable resin composition, it is also possible to use inorganic particles other than silica particles as fillers. However, when mixing inorganic particles with resin, affinity is often a problem. To address this problem, conventional methods have involved treating inorganic particles with coupling agents to increase their affinity with the resin. However, there are many different types of coupling agents, and it is necessary to select one considering both its affinity with the inorganic particles and its affinity with the resin. Furthermore, depending on the type of inorganic particle, treatment with coupling agents may be difficult. In particular, for particles with negative thermal expansion properties (also referred to as "negative expansion materials" in this specification), which have been developed in recent years, there is no prior knowledge, so it is necessary to select a coupling agent on a case-by-case basis.

[0060] In contrast, the inventors have discovered that the above problem can be solved by performing the steps of forming a metal-containing film containing a metal or metal oxide on the surface of the filler by atomic layer deposition (ALD), and arranging a coupling agent on the metal-containing film. In this method, a metal-containing film is formed on the surface of the filler. Therefore, without considering the type of filler, it is possible to select a specific coupling agent from a group of coupling agents with high affinity to the metal-containing film, considering only its affinity to the resin. Thus, this method has the advantage that the selection of a coupling agent is very easy and there is no need to perform excessive trial and error. Furthermore, the ALD method allows for the uniform formation of a dense film on the surface of the filler. Therefore, it becomes possible to evenly arrange the coupling agent across the entire surface of the filler, resulting in a very high affinity between the inorganic particles and the resin after this method is performed.

[0061] The type of filler that can be used in this method is not particularly limited, and various types and shapes of particles can be used. Examples of fillers include MnCuSnN and negative expansion materials such as ZMP (ZnO: 30-40 mass%, MgO: 1-9 mass%, NH4H2PO4: 55-65 mass%, manufactured by Mitsui Mining & Smelting Co., Ltd.).

[0062] On the other hand, examples of metals or metal oxides that constitute a metal-containing film include silicon dioxide (SiO2), Al2O3, TiO2, etc. In this modified example, metalloids such as Si are also treated as metals. Among these, silicon dioxide is preferred from the viewpoint of affinity with the coupling agent.

[0063] The method for forming the metal-containing film is the same as the known ALD method. The thickness of the metal-containing film is preferably thick enough not to be affected by the filler surface, but thin enough not to peel off, preferably between 4 nm and 170 nm, and more preferably between 10 nm and 80 nm. When the thickness of the metal-containing film is within this range, it tends to become a dense film.

[0064] Furthermore, the type of coupling agent is appropriately selected according to the type of metal or metal oxide constituting the metal-containing film. For example, if the metal-containing film is SiO2, various silane coupling agents can be used, and one can be appropriately selected from among the various silane coupling agents according to the type of resin. The method for arranging the silane coupling agent on the metal-containing film can be carried out in accordance with conventional methods. [Examples]

[0065] The present invention will be described below using examples and comparative examples, but the present invention is not limited in any way to the following examples.

[0066] 1. Examples 1-1. Preparation of materials The following materials were used in the examples and comparative examples.

[0067] (Polycyclic aliphatic acrylic resin) • IRR-214K (Tricyclodecanedimethanol diacrylate, manufactured by Daicel Ornex)

[0068] (Isocyanuric acid type acrylic resin) Tris[2-(acryloyloxy)ethyl]isocyanurate (manufactured by Sigma-Aldrich) • A-9300S (Tris[2-(acryloyloxy)ethyl]isocyanurate, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name: NK Ester A-9300S)

[0069] (Photopolymerization initiator) • BAPO (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, manufactured by Sigma-Aldrich)

[0070] (Silica particles) • SC2500-SMJ (methacrylate silane surface treatment, manufactured by Admatex, product name: AdmaFine SC2500-SMJ, 50% average particle size (median of volume particle size distribution by laser diffraction method): 0.5 μm) • NP-30 (manufactured by AGC SI-TEC, Sunsphere NP-30, 50% average particle size (median of volume particle size distribution by laser diffraction): 3 μm) • R7200 (methacrylate silane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL R7200, 50% average particle diameter (average particle diameter measured from 20 randomly selected particles taken from images taken with a transmission electron microscope): 12 nm) • YA050C-SM1: (Methacrylic silane surface treatment, manufactured by Admatex, product name: Admanano YA050-SM1, 50% average particle size (median of volume particle size distribution by laser diffraction method): 50 nm, specific surface area 65 m²) 2 / g) • YC100C-SM2 (methacrylate silane surface treatment, manufactured by Admatex, product name: AdmaFine YA100C-SM2, 50% average particle size (median of volume particle size distribution by laser diffraction method): 100 nm, specific surface area 30 m²) 2 / g)

[0071] (others) • A-HD-N (Hexanediol diacrylate, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name: NK Ester A-HD-N) • NanoAce D-800 (Talc, manufactured by Nippon Talc Co., Ltd., 50% average particle size 0.8 μm (median value of volume particle size distribution by laser diffraction method)) • BYK111 (dispersant, manufactured by BYK, product name: Disper BYK111)

[0072] 1-2. Preparation of photocurable resin composition (Example 1) Acrylic resins of the types shown in Table 1 and photopolymerization initiators were separated into beakers in the mass ratios shown in Table 1. Specifically, 80 parts by mass of polycyclic aliphatic acrylic resin (tricyclodecanedimethanol diacrylate), 20 parts by mass of isocyanuric acid acrylic resin (tris[2-(acryloyloxy)ethyl]isocyanurate), and 1.0 part by mass of photopolymerization initiator (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) were separated into beakers. These were heated at 60°C for 2 hours while stirring, and it was confirmed that a homogeneous solution was obtained. Subsequently, 235 parts by mass of silica particles (SC2500-SMJ) were added, and the mixture was kneaded and degassed using a planetary mixer SK-300TVS (manufactured by Shashin Kagaku Co., Ltd.). This prepared a photocurable resin composition.

[0073] (Examples 2-7, Comparative Examples 1-10) A photocurable resin composition was prepared in the same manner as in Example 1, except that the type and amount of acrylic resin, the type and amount of silica particles, and the amount of photopolymerization initiator were changed as shown in Tables 1 and 2 below.

[0074] (Comparative Example 11) A photocurable resin composition was prepared in the same manner as in Example 1, except that the type and amount of acrylic resin and the amount of photopolymerization initiator were changed as shown in Table 2 below, and talc was used instead of silica particles. The dispersant was added after mixing the acrylic resin and the photopolymerization initiator, and before mixing the talc.

[0075] 1-3. Evaluation Method The photocurable resin compositions prepared in Examples 1-7 and Comparative Examples 1-11 described above were used to fabricate stereolithographic objects using the following methods, and their evaluation was performed. The results are shown in Tables 1 and 2.

[0076] (Method for fabricating stereolithography objects) A 1mm thick, donut-shaped spacer (a φ80mm disc with a φ50mm through-hole in the center) was placed on a release-treated glass plate. The aforementioned photocurable resin composition was poured into the recess formed by the wall surrounding the through-hole of the spacer and the glass plate. Then, another release-treated glass plate was placed on top of the spacer, sandwiching the photocurable resin composition between them. Finally, a high-pressure mercury lamp (Oak Manufacturing Co., Ltd., UV-800) was used to shine 365nm wavelength light onto the photocurable resin composition from both sides for 15 seconds each, with an integrated light intensity of 200mW / cm². 2 The material was irradiated to a certain degree. Then, it was heated in a 200°C oven for 1 hour to obtain the stereolithography object.

[0077] (Method for preparing test specimens) The above-mentioned stereolithographic object (molded body) was cut to a size of 2.8 mm x 15.0 mm using a small CO2 laser processing machine (HAJIME CL1, manufactured by O-Laser Co., Ltd.), and these were used as test pieces.

[0078] (Bending strength measurement) Bending strength was measured using a universal testing machine (manufactured by Instron). Specifically, a three-point bending test was performed using a jig with a span of 10 mm and upper and lower indenter diameters of 0.1 mm, at a crosshead speed of 10 mm / min. The sample size N=5 was used, and the average of the maximum stresses in the tests was taken as the bending strength value.

[0079] (Measurement of thermal expansion coefficient) The thermal expansion coefficient was evaluated using a ThermoplusEV02 TMA8311 / LN2 thermal analyzer (manufactured by Rigaku Corporation), referencing JIS K-7197. Specifically, thermal analysis was performed under a nitrogen atmosphere with a load of -49.0 mM and a heating rate of 5°C / min to determine the thermal expansion coefficient in the range of -40°C to 150°C.

[0080] (Evaluation of the durability of the edges of the molded object) A 1mm thick, donut-shaped spacer (a φ80mm disc with a φ50mm through-hole in the center) was placed on a 0.5mm thick anodized aluminum black plate that had been treated for mold release. The aforementioned photocurable resin composition was poured into the recess formed by the wall surrounding the through-hole of the spacer and the black plate. A glass plate that had been treated for mold release was then placed on top of the spacer. Half of the area of ​​the through-hole of the glass plate (a semicircular area) was masked with black tape. In this state, the photocurable resin composition was irradiated with light from a UV lamp (wavelength 365nm) for 5 seconds from the glass plate side. After wiping off the uncured portion with a nonwoven cloth, the uncured portion was wiped off with ethanol to obtain a stereolithographic object (molded body). The durability of the edges of the printed object was evaluated by pressing a 0.5 mm thick anodized aluminum plate perpendicularly against the edge (chord portion) of a semicircular stereolithographic object (molded body) produced using the method described above and rubbing it. In this test, A (good durability) was assigned if no dust was produced from the stereolithographic object, B if almost no dust was produced, C if dust was produced, and D (poor durability) if a large amount of dust was produced.

[0081] 1-4.Results [Table 1]

[0082] [Table 2]

[0083] As shown in Table 1 above, all of Examples 1 to 7 that satisfy the above conditions [a] to [d] exhibited a bending strength of 174 MPa or higher, which is a sufficiently high value. Furthermore, the coefficient of thermal expansion was also within 35 ppm / K or less.

[0084] In contrast, as shown in Table 2, when conditions [a] and / or [b] were not met, i.e., when the content of polycyclic aliphatic acrylic resin and isocyanuric acid acrylic resin was not within an appropriate range (Comparative Example 1), or when neither polycyclic aliphatic acrylic resin nor isocyanuric acid acrylic resin was present (Comparative Examples 2, 3, and 10), although the coefficient of thermal expansion was good, the flexural strength was low in all cases. One possible reason for this is that a network was not formed by the polycyclic aliphatic acrylic resin and isocyanuric acid acrylic resin.

[0085] On the other hand, in Comparative Examples 4 and 5, where the amount of silica particles was too small (not satisfying [d] above), the bending strength was low and the coefficient of thermal expansion was also high. Furthermore, in Comparative Example 9, where the amount of silica particles was too large (not satisfying [d] above), the material became thickened, and it was not possible to fabricate a stereolithographic object.

[0086] Furthermore, in Comparative Example 6, where the 50% average particle size of the silica particles was too small and the quantity was insufficient (failing to satisfy conditions [c] and [d] above), the silica particles were unable to contribute to improving flexural strength or reducing thermal expansion coefficient, resulting in low flexural strength and high thermal expansion coefficient. Moreover, in Comparative Example 7, where the 50% average particle size of the silica particles was too small (failing to satisfy condition [d] above), adding a large amount of silica particles to satisfy condition [c] above resulted in increased viscosity, making it impossible to fabricate a stereolithographic object.

[0087] On the other hand, in Comparative Example 8, where the 50% average particle size of the silica particles was too large (not satisfying condition [d] above), the bending strength was extremely low.

[0088] Furthermore, when talc was used instead of silica particles, the flexural strength did not increase sufficiently even if the 50% average particle size and quantity (as specified in [c] and [d] above) met the above requirements. This suggests that talc could not efficiently reinforce the polycyclic aliphatic acrylic resin and isocyanuric acid acrylic resin networks.

[0089] 2. First example 2-1. Preparation of materials The following materials were used in each example.

[0090] (Polycyclic aliphatic acrylic resin) • IRR-214K (Tricyclodecanedimethanol diacrylate, manufactured by Daicel Ornex)

[0091] (Isocyanuric acid type acrylic resin) • A-9300S (Tris[2-(acryloyloxy)ethyl]isocyanurate, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name: NK Ester A-9300S)

[0092] (Photopolymerization initiator) • Omnirad 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, manufactured by IGM Resins)

[0093] (Silica particles) • SC2500-SMJ (methacrylate silane surface treatment, manufactured by Admatex, product name: AdmaFine SC2500-SMJ, 50% average particle size (median of volume particle size distribution by laser diffraction method): 0.5 μm) • R7200 (methacrylate silane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL R7200, 50% average particle size (median of volume particle size distribution by laser diffraction method): 12 nm) • NP-30 (manufactured by AGC SI-TEC, Sunsphere NP-30, 50% average particle size (median of volume particle size distribution by laser diffraction): 3 μm)

[0094] 1-2. Preparation of photocurable resin composition (Reference example 1) ·Preparation of photocurable resin composition for base material 70 parts by mass of polycyclic aliphatic acrylic resin (tris[2-(acryloyloxy)ethyl]isocyanurate), 30 parts by mass of isocyanuric acid type acrylic resin (tris[2-(acryloyloxy)ethyl]isocyanurate), and 0.7 parts by mass of photopolymerization initiator (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) were placed in a beaker. These were heated at 60°C for 2 hours while stirring, and it was confirmed that a homogeneous solution was obtained. Then, 235 parts by mass of silica particles (SC2500-SMJ) were added to the above solution, and the mixture was kneaded and degassed using a planetary mixer SK-300TVS (manufactured by Shashin Kagaku Co., Ltd.). This prepared a photocurable resin composition for the base material.

[0095] Preparation of photocurable resin compositions for coating layers 100 parts by mass of a polycyclic aliphatic acrylic resin (tricyclodecanedimethanol diacrylate) was mixed with 2.0 parts by mass of a photoradical polymerization initiator (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide). These were placed in a beaker and stirred while heating at 60°C for 1 hour to prepare a photocurable resin composition for a coating layer.

[0096] (Comparison Examples 1-3) As shown in Table 3 below, the photocurable resin composition for the base material and the photocurable resin composition for the coating layer were prepared in the same manner as in Reference Example 1, except that the amount and type of silica particles in the photocurable resin composition for the base material were changed.

[0097] 2-3. Evaluation Method The photocurable resin compositions for the base material and the photocurable resin compositions for the coating layer prepared in Reference Example 1 and Comparative Examples 1-3 described above were used to fabricate stereolithographic objects using the following method, and their evaluation was performed. The results are shown in Table 3.

[0098] (Method for fabricating stereolithography objects) • Preparation of the base material A 1mm thick, donut-shaped spacer (a φ80mm disc with a φ50mm through-hole in the center) was placed on a 0.5mm thick anodized black plate that had been treated for mold release. The aforementioned photocurable resin composition for the base material was poured into the recess formed by the wall surrounding the through-hole of the spacer and the black plate. A glass plate that had been treated for mold release was then placed on the spacer. Half of the area of ​​the through-hole of the glass plate (a semicircular area) was masked with black tape. In this state, the photocurable resin composition for the base material was irradiated with light from a UV lamp (365nm) for 5 seconds from the glass plate side. After that, the uncured portion was wiped off with a nonwoven cloth and the base material was obtained by air blowing.

[0099] • Formation of the coating layer The coating layer composition was applied to the surface of the above-mentioned base material using a brush. Then, the coating layer composition was irradiated with a UV lamp (365 nm) from one side for 5 seconds to form a coating layer.

[0100] (Durability evaluation) A 0.5mm thick anodized aluminum plate was pressed vertically against the end face (arc portion) of the fabricated semicircular molded body and rubbed. The result was evaluated as A (good durability) if no dust was produced from the stereolithography object, and B (poor durability) if dust was produced.

[0101] 2-3.Results [Table 3]

[0102] In Reference Example 1, no detachment of powdered silica particles was observed, indicating sufficient durability of the coating layer. In contrast, in Comparative Reference Example 1, shavings were observed. It is believed that the average particle size of the silica particles was too small, resulting in insufficient anchoring effect and inadequate durability of the coating layer. Furthermore, in Comparative Reference Example 2, the base material itself could not be 3D printed. In addition, shavings were observed in Comparative Reference Example 3. In this case, it is believed that the average particle size of the silica particles was too large, resulting in insufficient anchoring effect and inadequate durability of the coating layer.

[0103] 3. Second example 3-1. Preparation of surface-treated (or untreated) fillers (Reference example A) A 45 nm thick Al2O3 film (metal-containing film) was deposited on the surface of a microfiller, MnCuSnN (thermal expansion coefficient at 25°C to 60°C: -22 ppm / K), by atomic layer deposition (ALD). Then, a silane coupling treatment was performed using the silane coupling agent A-1110 (Silquest A-1110, manufactured by Momentive), to obtain surface-treated inorganic particles.

[0104] (Comparative reference examples a~d) As shown in Table 4, surface-treated (or untreated) inorganic particles were obtained in the same manner as described above, except that no metal-containing film was formed and / or treatment with a silane coupling agent was performed.

[0105] (Reference examples B, C, comparative examples e~h) As shown in Table 5, surface-treated (or untreated) inorganic particles were obtained in the same manner as in Reference Example A and Comparative Reference Examples a-d, except that ZMP (ZnO: 30-40 mass%, MgO: 1-9 mass%, NH4H2PO4: 55-65 mass%, average particle size D50: 4-5 μm, manufactured by Mitsui Mining & Smelting Co., Ltd.) was used instead of MnCuSnN.

[0106] 3-2. Fabrication of molded bodies HTM140V2 (EnvisionTEC, resin composition for 3D modeling) and Aerosil R7200 (Nippon Aerosil, Inc.) were mixed in the mass ratios shown in Tables 4 and 5. Surface-treated (or untreated) inorganic particles were then mixed to obtain the mixture. A 1mm thick, donut-shaped spacer (a φ80mm disc with a φ50mm through-hole in the center) was placed on a release-treated glass plate. The mixture was poured into the recess formed by the wall surrounding the through-hole of the spacer and the glass plate. Another release-treated glass plate was then placed on top of the spacer, sandwiching the mixture. The mixture was then irradiated with 365nm light from both sides for 26 seconds each using a high-pressure mercury lamp (Oak Manufacturing Co., Ltd., UV-800). Finally, the molded body was heated in a 180°C oven for 1 hour. In reference comparative example X in Table 4, a molded body was obtained without adding surface-treated (or untreated) inorganic particles. Furthermore, this molded body was cut to a size of 3 mm x 15 mm using a cutting machine, and these were used as test specimens.

[0107] 3-3. Evaluation The mixture before curing and the molded articles after curing were evaluated using the following methods. The results are shown in Tables 4 and 5. Figure 1 shows photographs of the obtained molded articles observed with a scanning electron microscope.

[0108] (viscosity) The viscosity of the mixture before curing was measured 90 seconds after the start of rotation at room temperature and a shear rate of 1 (1 / s) using a rheometer (TA Instruments Discovery HR-2). Three measurements were taken, and the average value was used.

[0109] (Coefficient of linear expansion) The linear thermal expansion coefficients of the molded body in the range of -40°C to 25°C, the range of 25°C to 150°C, and the range of -40°C to 150°C were evaluated using a ThermoplusEV02 TMA8311 / LN2 thermal analyzer (manufactured by Rigaku Corporation), with reference to JIS K-7197.

[0110] (Bending test (bending stress, elongation at break, and modulus of elasticity)) A bending test was performed on the molded body at 23°C using an automatic load testing machine (MAX-1kN-H, manufactured by Nippon Keisoku System Co., Ltd.) under a condition of 10 mm / min, and the bending stress, elongation at fracture, and modulus of elasticity were determined.

[0111] (DMA measurement (elastic modulus at 150°C and 170°C)) Dynamic viscoelasticity (DMA) measurements were performed on the molded body to determine the elastic moduli at 150°C and 170°C.

[0112] (Evaluation of adhesion) The adhesion between the surface-treated (or untreated) filler and the resin was confirmed using a scanning electron microscope (SEM) and evaluated as follows. A (Good): The filler surface is covered with resin, and the filler is hardly exposed. B (mottled): Part of the filler surface was covered with resin. C (slight): The filler surface was not covered, but resin was adhering to the surface. D (Slight): Almost no resin adhered to the filler surface, and the sides of the filler were embedded in the resin. E (Almost none): Almost no resin adhered to the filler surface, and the sides of the filler were also exposed.

[0113] 3-4.Results [Table 4]

[0114] [Table 5]

[0115] As shown in Tables 4 and 5 above, and in Figure 1, compared to Reference Comparative Example X in which inorganic particles were not added, when a metal-containing film was formed on the filler surface and a silane coupling agent was also placed, the adhesion between the inorganic particles and the resin was very good (Reference Examples A, B, and C). Furthermore, the addition of these inorganic particles resulted in a lower coefficient of thermal expansion and a higher modulus of elasticity of the molded article.

[0116] On the other hand, when untreated inorganic particles were added, the adhesion between the inorganic particles and the resin was very low (comparative reference examples a and e). Furthermore, when the filler was treated only with a silane coupling agent, the adhesion sometimes improved depending on the combination with the filler (e.g., comparative reference example f), but when the type of filler was changed, the adhesion decreased (e.g., comparative reference example b). Moreover, when only a metal-containing film was formed and not treated with a silane coupling agent, sufficient adhesion was difficult to obtain in any case (comparative reference examples c, d, g, and h). [Industrial applicability]

[0117] The photocurable resin composition of the present invention provides a molded article that combines high strength and a low coefficient of thermal expansion. This molded article can be used in a variety of applications, such as electrical components.

Claims

1. This is a photocurable resin composition comprising a polyfunctional acrylic resin, silica particles, and a photopolymerization initiator. The polyfunctional acrylic resin contains 20% to 80% by mass of a polycyclic aliphatic acrylic resin, and also contains 20% to 80% by mass of an isocyanuric acid type acrylic resin. The 50% average particle diameter of the silica particles is 30 nm or more and less than 1.0 μm. The amount of the silica particles is 60% by mass or more and less than 80% by mass of the total mass of the photocurable resin composition. Photocurable resin composition.

2. The silica particles are surface-treated with a compound having a (meth)acryloyl group. The photocurable resin composition according to claim 1.

3. The polycyclic aliphatic acrylic resin is tricyclodecanedimethanol diacrylate. The photocurable resin composition according to claim 1.

4. The isocyanuric acid type acrylic resin is a compound represented by the following general formula: The photocurable resin composition according to claim 1. 【Chemistry 1】 (In the general formula, X １ , X ２ , and X ３ Each of these independently represents a linking group having 1 to 20 carbon atoms and which may contain oxygen. R １ and R ２ Each of these independently represents either a hydrogen atom or a methyl group. (Y represents a (meth)acryloyl group or a hydroxyl group.)

5. A cured product of a photocurable resin composition according to any one of claims 1 to 4, Molded body.

6. The cured product of the aforementioned photocurable resin composition, A coating layer comprising a polycyclic aliphatic acrylic resin is disposed on the cured product, including, The molded article according to claim 5.

7. A molded article comprising the one described in claim 5, Electrical components.

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