Adhesive composition, production method therefor, and optical device

Abstract

Provided are an adhesive composition and a production method therefor, the adhesive composition having good manipulability during use, and a cured body of the composition having a low coefficient of linear expansion and storage elastic modulus. Also provided is an optical device in which components are less susceptible to displacement caused by temperature changes and impacts. This adhesive composition contains an (A) epoxy compound, an (B) oxetane compound, a (C) silane coupling agent, a (D) photoacid generator, and (E) silica. The (E) silica includes (E-1) large-particle silica and (E-2) small-particle silica. The average particle size D50 of the (E-1) large-particle silica is 0.5 μm to 1.5 μm. The average particle size D50 of the (E-2) small-particle silica is less than 0.5 μm. The difference between the average particle size D50 of the (E-1) large-particle silica and the average particle size D50 of the (E-2) small-particle silica is 0.5 μm or more. The (E-2) small-particle silica content of the (E) silica is 10 mass% to 50 mass%.

Description

Adhesive composition, method for producing the same, and optical device

[0001] The present invention relates to an adhesive composition, a method for producing the same, and an optical device.

[0002] In the manufacture of optical devices such as smartphone camera modules and in-vehicle optical sensors, a method of bonding optical components such as lenses and imaging elements to a substrate or housing using a photocationically curable adhesive, which is an ultraviolet-curable adhesive, is commonly employed. For example, an adhesive composition containing an epoxy compound, an oxetane compound, a photocationic polymerization initiator, a silane coupling agent, and silica has been proposed as such a photocationically curable adhesive, from the viewpoint of exhibiting excellent adhesive strength and mounting accuracy (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-69039

[0004] Adhesives used in optical devices are required to have properties that prevent optical components from shifting or falling off due to external factors during use. Specifically, the adhesive after curing is required to have a low linear expansion coefficient, i.e., to be resistant to temperature changes, and also to have flexibility to absorb impacts, i.e., a low storage modulus. Furthermore, when using the adhesive, it is also required to be easy to suction or dispense with an applicator such as a dropper or dispenser, and to be placed at the bonding site.

[0005] An object of the present invention is to provide an adhesive composition that has good operability during use and a low linear expansion coefficient and storage modulus after curing, a method for producing the same, and an optical device whose components are less likely to shift due to temperature changes and impacts.

[0006] In order to solve the above problems, the present invention includes the following inventions.

[0007] The present invention [1] comprises an adhesive composition containing (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica, wherein the (E) silica has (E-1) large-particle-size silica and (E-2) small-particle-size silica, the average particle diameter D50 of the (E-1) large-particle-size silica is 0.5 μm or more and 1.5 μm or less, the average particle diameter D50 of the (E-2) small-particle-size silica is less than 0.5 μm, the difference between the average particle diameter D50 of the (E-1) large-particle-size silica and the average particle diameter D50 of the (E-2) small-particle-size silica is 0.5 μm or more, and the content of the (E-2) small-particle-size silica in the (E) silica is 10% by mass or more and 50% by mass or less.

[0008] The present invention [2] includes the adhesive composition according to [1], in which the content of (E) silica per 100 parts by mass of the total of (A) the epoxy compound and (B) the oxetane compound is 100 parts by mass or more and 200 parts by mass or less.

[0009] The present invention [3] includes an optical device comprising a cured product of the adhesive composition according to [1] or [2].

[0010] The present invention [4] is a method for producing an adhesive composition containing (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica, the method comprising mixing (E-1) large-particle silica having an average particle size D50 of 0.5 μm or more and 1.5 μm or less and (E-2) small-particle silica having an average particle size D50 of less than 0.5 μm and a difference of 0.5 μm or more from the average particle size D50 of the large-particle silica (E-1) such that the content of the small-particle silica (E-2) in the silica (E) is 10% by mass or more and 50% by mass or less.

[0011] The adhesive composition of the present invention has good operability during use and a good linear expansion coefficient and storage modulus after curing. Furthermore, the optical device of the present invention can suppress displacement of components due to temperature changes and impacts.

[0012] FIG. 1 shows a schematic cross-sectional view of a camera module of the present invention.

[0013] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below, and can be implemented with any modifications within the scope of the gist of the present invention.

[0014] An example of the adhesive composition of the present invention (hereinafter also referred to as "the composition") is a photocationically curable adhesive containing (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica. Each component is described in detail below.

[0015] (A) Epoxy Compound The epoxy compound has one or more epoxy groups in the molecule, and preferably has two or more epoxy groups in the molecule. By containing the epoxy compound, the present composition can be cured by a polymerization reaction to bond parts together. Furthermore, by having multiple epoxy groups in the epoxy compound, the strength of the cured product of the present composition is further improved.

[0016] The epoxy compound is preferably an alicyclic epoxy compound having an alicyclic structure and an epoxy group, more preferably an alicyclic epoxy compound having an epoxy group (alicyclic epoxy group) composed of two adjacent carbon atoms and an oxygen atom that constitute an alicyclic ring. Because such epoxy compounds have rigidity, thermal volume expansion of the cured product of the composition is suppressed, and the linear expansion coefficient can be further reduced.

[0017] The alicyclic epoxy compound preferably has two or more epoxy groups in the molecule. In this case, all of the two or more epoxy groups may be alicyclic epoxy groups, or may be a combination of alicyclic epoxy groups and non-alicyclic epoxy groups. Preferably, all of the epoxy groups are alicyclic epoxy groups.

[0018] Examples of such alicyclic epoxy compounds include compounds represented by the following formulas (A1) to (A3). These alicyclic epoxy compounds may be used alone or in combination of two or more. In the present composition, preferably, at least the compound of formula (A1) is used. More preferably, the alicyclic epoxy compound of formula (A1) is used in combination with the alicyclic epoxy compound of formula (A2) and / or (A3).

[0019]

[0020] In the above formula, R １ represents an alkylene group having 4 to 8 carbon atoms, and n represents, for example, an integer of 1 to 5. X represents a single bond, an ether bond (—O—), a thioether bond (—S—), or an alkylene group having 1 to 3 carbon atoms. R ２ represents an alkylene group having 1 to 3 carbon atoms, etc.

[0021] Specific examples of the alicyclic epoxy compound include CELLOXIDE 8000, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, CELLOXIDE 2085, EPOLEAD GT401, and EHPE3150 manufactured by Daicel Corporation; and TTA21, TTA22, TTA26, and TTA3150 manufactured by Sun Chemical Co. These may be used alone or in combination of two or more.

[0022] When the alicyclic epoxy compound of Formula (A1) is used in combination with other alicyclic epoxy compounds (for example, the alicyclic epoxy compounds of Formula (A2) and / or Formula (A3)), the blending ratio thereof (other alicyclic epoxy compounds:alicyclic epoxy compound of Formula (A1)) is, in mass ratio, for example, 1:1 to 6:1, preferably 2:1 to 3:1. This can further improve the linear expansion coefficient and storage modulus of the cured body of the composition.

[0023] The present composition may further contain a bisphenol-type epoxy resin as the epoxy compound in addition to the above-mentioned alicyclic epoxy compound, thereby adjusting the crosslink density of the cured product of the present composition and improving the linear expansion coefficient and storage modulus.

[0024] Examples of bisphenol type epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, and bisphenol AD ​​type epoxy resins.

[0025] The weight average molecular weight of the bisphenol type epoxy resin is, from the viewpoint of the linear expansion coefficient of the cured body, for example, 1200 or less, preferably 800 or less, more preferably 600 or less, and for example, 300 or more.

[0026] Specific examples of bisphenol-type epoxy resins include jER806, jER806H, jER807, jER825, jER827, jER828, jER828EL, jER828US, jER828XA, and jER834 manufactured by Mitsubishi Chemical Corporation; YD-8125 and YDF-8170C manufactured by Nippon Steel Chemical & Material Co., Ltd.; and Epiclon 830, Epiclon 830-S, Epiclon 835, Epiclon 840, Epiclon 840-S, Epiclon 850, Epiclon 850-S, and Epiclon 850-LC manufactured by DIC Corporation. These may be used alone or in combination of two or more.

[0027] When an alicyclic epoxy compound and a bisphenol-type epoxy resin are used in combination, the mass ratio of the alicyclic epoxy compound to the bisphenol-type epoxy resin is, for example, 1:1 to 6:1, and preferably 3:1 to 4:1. This allows the linear expansion coefficient, storage modulus, glass transition temperature, and other properties to be adjusted to desired values ​​for an adhesive used in optical devices such as camera modules or optical sensors. The total epoxy compound content in the composition is, for example, 10% by mass or more, preferably 25% by mass or more, and for example, 60% by mass or less, preferably 45% by mass or less. This further improves adhesive strength and mounting accuracy.

[0028] (B) Oxetane Compound The oxetane compound has one or more oxetane groups in the molecule. Since the propagation reaction rate of an oxetane compound is faster than that of an epoxy compound, the inclusion of the oxetane compound in the composition of the present invention allows the polymerization reaction during curing to proceed efficiently, reduces the brittleness inherent to epoxy resins, and improves flexibility and toughness.

[0029] Examples of oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, xylylene bisoxetane, oxetanyl silsesquioxetane, 3-ethyl-3-phenoxymethyloxetane, 2-ethylhexyloxetane, 3-ethyl-3-(cyclohexyloxy)methyloxetane, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, phenol novolac oxetane, etc. These may be used alone or in combination of two or more.

[0030] The content of the oxetane compound is, in terms of the mass ratio of the epoxy compound to the oxetane compound, for example, 4:1 to 20:1, or preferably 8:1 to 10:1, thereby achieving a good balance between the curing rate and the physical properties of the cured product.

[0031] (C) Silane Coupling Agent The silane coupling agent is a silicon compound having both an organic reactive site and an inorganic reactive site. By including the silane coupling agent, the adhesive strength of the present composition can be improved.

[0032] Examples of silane coupling agents include vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. These may be used alone or in combination of two or more. From the viewpoint of affinity between the epoxy compound and the oxetane compound, 3-glycidoxypropyltrimethoxysilane is preferred.

[0033] The content of the silane coupling agent is, relative to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, for example, 0.5 parts by mass or more, preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 4.5 parts by mass or less. By setting the content in such a range, the adhesiveness of the composition can be further improved.

[0034] (D) Photoacid Generator The photoacid generator generates an acid upon irradiation with energy rays or radiation. In the present composition, it is blended, for example, as a polymerization initiator.

[0035] Examples of photoacid generators include onium salts that release a Lewis acid upon irradiation with energy rays or the like. Examples of such onium salts include sulfonium salts and iodonium salts, with sulfonium salts being preferred. Examples of sulfonium salts include the compound represented by the following formula (D1) (diphenyl[4-(phenylthio)phenyl]sulfonium salt) and the compound represented by formula (D2). Examples of iodonium salts include the compound represented by the following formula (D3) or (D4). These may be used alone or in combination of two or more.

[0036]

[0037] In the above formula, X － are SbF, respectively. ６ － , P.F. ６ － , P.F. ３ (C ２ F ５ ) ３ － , B(C ６ F ５ ) ４ － , B.F. ４ － , AsF ６ － This indicates an anion such as:

[0038] The content of the photoacid generator is, relative to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, for example, 0.5 parts by mass or more, preferably 1 part by mass or more, and for example, 10 parts by mass or less, preferably 5 parts by mass or less. By setting the content in such a range, the composition can be cured with ultraviolet irradiation for a shorter period of time.

[0039] (E) Silica The silica includes (E-1) large particle size silica and (E-2) small particle size silica. Preferably, the silica consists solely of large particle size silica and small particle size silica.

[0040] (E-1) Large-Particle Silica The large-particle silica has an average particle diameter D50 of 0.5 μm or more and 1.5 μm or less, preferably 0.7 μm or more and 1.5 μm or less, and more preferably 1.2 μm or more and 1.5 μm or less. The large-particle silica preferably has a D10 / D90 value of 0.7 or less. D10 / D90 is an index indicating the uniformity of the particle size distribution; the smaller this value, the more uniform the particle size distribution and the greater the number of silica particles of 0.5 μm or more and 1.5 μm or less. This facilitates a decrease in the storage modulus due to the interaction between the large-particle silica and the small-particle silica. In the present invention, D10, D50, and D90 are the particle sizes at which the volume accumulation in the particle size distribution curve determined by laser diffraction is 10%, 50%, and 90%, respectively. Specifically, 100 mg of silica is mixed with 40 ml of water, and the mixture is dispersed for 10 minutes using an ultrasonic homogenizer at an output of 40 W. The D10, D50, and D90 can be determined from the particle size distribution curve obtained by measuring the sample using a laser diffraction particle size distribution analyzer.

[0041] The specific surface area of ​​the large particle silica is, for example, 0.5 m ２ / g or more, preferably 1m ２ / g or more, more preferably 1.5m ２ / g or more, and for example, 5m ２ / g or less, preferably 4.5m ２ / g or less, more preferably 4m ２ / g or less. By setting the specific surface area of ​​the large particle size silica within the above range, it is possible to suppress an increase in viscosity and ensure high fluidity even when the composition contains a high content of silica. The specific surface area of ​​silica is the BET specific surface area measured by the BET method.

[0042] The content of large-particle silica in the silica is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and for example, 90% by mass or less, preferably 85% by mass or less, preferably 80% by mass or less, and for example, 80 parts by mass or more, preferably 90 parts by mass or more, more preferably 110 parts by mass or more, and for example, 200 parts by mass or less, preferably 180 parts by mass or less, more preferably 150 parts by mass or less, relative to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound.

[0043] (E-2) Small Particle Size Silica The small particle size silica has an average particle size D50 of less than 0.5 μm, and for example, 0.1 μm or more, preferably 0.3 μm or more. In the small particle size silica, the D10 / D90 ratio is preferably 0.7 or less.

[0044] The specific surface area of ​​the small particle silica is, for example, 5 m ２ / g or more, preferably 6.5m ２ / g or more, more preferably 8m ２ / g or more, and for example, 20m ２ / g or less, preferably 18m ２ / g or less, more preferably 16m ２ / g or less. By setting the specific surface area of ​​the small-particle silica to be equal to or greater than the above lower limit, sedimentation of the silica during storage of the composition can be suppressed, resulting in excellent sedimentation resistance. Furthermore, by setting the specific surface area of ​​the small-particle silica to be equal to or less than the above upper limit, the fluidity of the composition can be further improved.

[0045] The content (content ratio) of small-particle silica in the silica is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less. Furthermore, relative to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, the content is, for example, 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and for example, 80 parts by mass or less, preferably 60 parts by mass or less, more preferably 40 parts by mass or less. By setting the content of small-particle silica within the above range, the storage modulus of the cured product of the composition can be reduced (improved) while maintaining the fluidity of the composition. Therefore, in optical devices bonded with a cured product of the composition, the effects of impact can be mitigated, preventing component misalignment or detachment.

[0046] The difference (particle size difference) between the average particle size D50 of the large-particle silica and the average particle size D50 of the small-particle silica is 0.5 μm or more, preferably 0.8 μm or more, more preferably 1.1 μm or more, and for example, 5.0 μm or less, preferably 3.0 μm or less, more preferably 2.0 μm or less. If the particle size difference is below the lower limit, the voids between the silica particles in the cured product of this composition will become large, and the silica region and the resin region will be easily separated, resulting in a layered state. As a result, the hard silica region will be unevenly distributed, which will easily cause stress concentration in the silica region, and the storage modulus will be high.

[0047] Preferably, both the large-particle silica and the small-particle silica are spherical silica. Specifically, the shapes of 1,000 silica particles contained in the silica are observed with a scanning electron microscope, and the sphericity of each particle is measured. If the average value is 0.9 or more, the silica is considered to be spherical silica. The sphericity is calculated by the formula 4π × (area) / (perimeter) ２ The measurement can be performed using an image processing program (e.g., AnalySIS manufactured by Soft Imaging System GmbH). This makes it possible to suppress an increase in viscosity and ensure high fluidity even when the composition contains a high content of silica.

[0048] Furthermore, the large-particle silica and the small-particle silica are preferably independent. Independent means that the silica is unlikely to form aggregates (both primary aggregates and secondary aggregates). Specifically, for silica, the ratio (specific surface area) / (calculated value of specific surface area) is in the range of 0.85 to 1.35. The specific surface area is measured by the BET method. The calculated value of the specific surface area is calculated by 6 / (density x D50), and the density of silica in this calculation is 2.2 g / cm. ３ This allows the silica to exist independently in the composition without agglomerating, making it less likely that stress will concentrate, and thus making it easier to reduce the storage modulus of the cured product of the photocationically curable adhesive.

[0049] The total content of silica (i.e., the sum of large-particle silica and small-particle silica) is, relative to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, for example, 90 parts by mass or more, preferably 100 parts by mass or more, more preferably 130 parts by mass or more, and for example, 300 parts by mass or less, preferably 200 parts by mass or less, more preferably 170 parts by mass or less. By setting the amount of silica in the above range, it is possible to maintain a low linear expansion coefficient while suppressing an increase in viscosity and improving fluidity. Therefore, the composition can be used by suction or discharge to improve workability, and can exhibit properties suitable for use as an adhesive in optical devices such as camera modules and optical sensors.

[0050] The silica in the present composition, both large-particle and small-particle silica, may be commercially available or produced by known methods such as dry and wet processes. Alternatively, commercially available or produced silica may be used after adjusting the specific surface area to the desired range using sieves, air classification, or the like. The dry process involves burning a silicon compound to produce silica powder, which is then grown in or near the flame. Specific examples of the dry process include the method described in WO 2020 / 175160. In the dry process, the average particle size and specific surface area can be adjusted by adjusting the flame combustion and cooling conditions and the amount of heat removal. Examples of wet processes include the sol-gel process. The sol-gel process involves hydrolyzing and polycondensing silicon alkoxide in a catalyst-containing reaction medium to produce a silica sol, which is then gelled and dried. Specific examples of the sol-gel process include the method described in WO 2018 / 096876. In the sol-gel method, the average particle size and specific surface area can be adjusted by adjusting the reaction temperature, the concentration of the reaction solution, and the dropping speed of the reaction solution. The silica may be surface-treated with a silane coupling agent or the like.

[0051] The present composition has good fluidity, and furthermore, when cured, it has a low coefficient of linear expansion and a low storage modulus. The reason for this is not clear, but the present inventors believe it to be as follows. Note that the present invention is not limited to the following.

[0052] By incorporating a high silica content into the adhesive, the proportion of resin components (polymers of epoxy compounds and oxetane compounds) with a relatively high linear expansion coefficient can be reduced, thereby reducing (improving) the linear expansion coefficient of the cured adhesive. However, on the other hand, the proportion of relatively hard silica increases, increasing the storage modulus of the cured adhesive and reducing its flexibility. Furthermore, the high silica content reduces the fluidity of the adhesive, making it difficult to smoothly draw in and dispense from the dispenser during use, reducing operability. Thus, it was thought that it was difficult to achieve both a low storage modulus and good fluidity while reducing the linear expansion coefficient with conventional single-silica formulations.

[0053] In response to this problem, the present inventors solved the above problem by incorporating specific amounts of two specific types of silica, namely, a specific large-sized silica and a specific small-sized silica having a specific particle size difference, into the adhesive composition of the present invention. Specifically, by replacing a portion of the large-sized silica having a low linear expansion coefficient with a small-sized silica having a low linear expansion coefficient, the concentrated stress on the large-sized silica is dispersed to the surrounding resin. In addition, by setting the particle size difference between the large-sized silica and the small-sized silica to a specific value or more, the small-sized silica is appropriately positioned in the gaps between the large-sized silica, suppressing layer separation (separation between the silica and the resin) and reducing the concentrated stress on the silica region. This reduction in concentrated stress leads to a reduction in the storage modulus. Furthermore, by adjusting the amount of small-sized silica to an appropriate amount, a decrease in fluidity is suppressed, achieving a reduction in both the linear expansion coefficient and the storage modulus while maintaining good fluidity.

[0054] (Other Components) The present composition may contain other components in addition to (A) to (E) to the extent that the effects of the present invention are not impaired. Examples of other components include fillers other than silica, thermal cationic polymerization initiators, curing accelerators, flame retardants, rubber particles, thickeners, antifoaming agents, leveling agents, antioxidants, colorants, and photosensitizers. In addition, in the present composition, it is preferable that the filler consist solely of silica, from the viewpoint of achieving both a high linear thermal expansion coefficient and a high storage modulus.

[0055] (Method for Producing Adhesive Composition) In one example of a method for producing the present composition, (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, (E-1) large-particle silica, and (E-2) small-particle silica are mixed together so that the content of small-particle silica in the silica is 10% by mass or more and 50% by mass or less.

[0056] For example, (A) the epoxy compound, (B) the oxetane compound, (C) the silane coupling agent, (D) the photoacid generator, (E-1) the large particle size silica, and (E-2) the small particle size silica may be mixed at the same time, or these components may be mixed in an appropriate order.

[0057] Alternatively, (E-1) large-particle silica and (E-2) small-particle silica may be separately mixed to prepare a mixed silica (i.e., (E) silica), and this (E) silica may then be mixed with (A) epoxy compound, (B) oxetane compound, (C) silane coupling agent, and (D) photoacid generator. In this case, the order in which (A), (B), (C), (D), and (E) are mixed is not limited, and for example, they may all be mixed at the same time, or they may be mixed in any appropriate order.

[0058] The mixing method is not limited, and the mixture can be produced by a known method using, for example, a known mixing device such as a blender, a mixer, etc. If necessary, the mixing may be carried out in a heated atmosphere or an inert gas atmosphere.

[0059] (Physical Properties of the Cured Product of the Adhesive Composition of the Present Invention) A cured product of the present composition can be obtained by subjecting the composition to the curing method described below. The linear expansion coefficient of the cured product of the present composition is preferably 60 ppm / K or less, more preferably 50 ppm / K or less, and even more preferably 45 ppm / K or less. When the linear expansion coefficient of the cured product is below the above upper limit, thermal expansion and thermal contraction are small, resulting in excellent low expansion properties. Therefore, when optical device components (e.g., lenses, image sensors, etc.) are fixed using the present composition, even when the optical device is heated or cooled, volume changes at the bonded locations are mitigated, thereby preventing component misalignment and detachment (disengagement) due to temperature changes. Therefore, the present composition can provide an optical device that is less susceptible to thermal effects. The lower limit is not limited, but is, for example, 30 ppm / K or more, preferably 35 ppm / K or more. The linear expansion coefficient can be measured, for example, by a compression load method using a thermomechanical analyzer.

[0060] The storage modulus E' of the cured product of this composition is preferably 8 GPa or less, more preferably 7.5 GPa or less, and even more preferably 7 GPa or less. When the storage modulus of the cured product is below the above upper limit, the flexibility is excellent. Therefore, when a component is fixed using this composition, even if the optical device is subjected to an impact, the adhesive portion absorbs the impact, thereby preventing the component from shifting or falling off due to the impact. Therefore, this composition can provide an optical device that is less susceptible to mechanical influences. The lower limit is not limited, but is, for example, 4 GPa or more, preferably 5 GPa or more. The storage modulus E' is the value at 25°C when a 1 mm thick cured product is measured using a dynamic viscoelasticity measuring device at a frequency of 1 Hz.

[0061] The glass transition temperature Tg of the cured product of the present composition is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. When the glass transition temperature of the cured product is equal to or higher than the above-mentioned lower limit, the heat resistance of the bonded portion is excellent. The upper limit is not limited, but is, for example, 250°C or lower, preferably 200°C or lower.

[0062] (Applications) The present composition is not limited to adhesive applications and can be used to bond various parts. The present composition can be bonded (cured) by ultraviolet irradiation, and the cured product has a good linear expansion coefficient and storage modulus, making it suitable for use in the production of optical devices. Optical devices are devices equipped with optical components such as lenses and mirrors, and examples include camera modules and optical sensors equipped with such modules. Such optical components, such as camera modules and optical sensors, are designed for various purposes, such as for smartphones and in-vehicle applications. An example of the use of the present composition for bonding camera modules is described below.

[0063] (Camera Module) An example of a camera module including a cured product of the adhesive of the present invention will be described with reference to FIG.

[0064] The camera module 1 of the present invention includes a lens 2 , a lens barrel 3 , a seal glass 4 , an imaging element 5 , a circuit board 6 , a housing 7 , and a hardened body 8 .

[0065] The lens 2 is fixed to the lens barrel 3 inside the lens barrel 3 via a hardened body 8. That is, the hardened body 8 is disposed between the outer peripheral surface of the lens 2 and the inner peripheral surface of the lens barrel 3.

[0066] The lens barrel 3 is fixed to the housing 7 inside the housing 7 via a hardened body 8. That is, the hardened body 8 is disposed between the outer peripheral surface of the housing 3 and the inner peripheral surface of the housing 7.

[0067] The seal glass 4 is fixed to the housing 7 via a hardened body 8 inside the housing 7. That is, the hardened body 8 is disposed between the outer peripheral surface of the seal glass 4 and the inner peripheral surface of the housing 7. The seal glass 4 may also serve as an infrared cut filter that blocks infrared rays.

[0068] The circuit board 6 has its upper surface (the surface on the lens 2 side) fixed to the housing 7 via the hardened body 8. That is, the hardened body 8 is disposed between the upper surface of the circuit board 6 and the lower surface of the housing 7. In addition, the imaging element 5 is mounted on the circuit board 6.

[0069] The camera module 1 of the present invention is produced by applying or flowing the present composition to (1) the bonding area between the lens 2 and the lens barrel 3, (2) the bonding area between the seal glass 4 and the housing 7, (3) the bonding area between the lens barrel 3 and the housing 7, and (4) the bonding area between the circuit board 6 and the housing 7, and then curing the composition.

[0070] The composition can be cured, for example, by ultraviolet irradiation. The irradiance and duration of ultraviolet irradiation are not limited as long as the resin component of the composition reacts. For example, ２ More than 1000mW / cm ２ The irradiation time may be 10 seconds or more and 10 minutes or less. The irradiation may be performed once or multiple times. In the case of multiple irradiations, for example, temporary fixation may be performed by first irradiating with low-intensity ultraviolet light, and then final fixation may be performed by irradiating with high-intensity ultraviolet light. Furthermore, a heating step may be performed after ultraviolet light irradiation. This can promote post-curing and relieve thermal distortion caused by ultraviolet light irradiation, thereby increasing adhesive strength. The heating conditions may be, for example, a temperature of 50°C to 150°C for 0.5 hours to 5 hours. The composition may be applied and flowed using a known application tool such as a dropper or dispenser.

[0071] The camera module 1 thus obtained is bonded at the bonding locations (1) to (4) above with a cured product of the present composition. Therefore, the bonding locations are resistant to thermal expansion and have an appropriate degree of flexibility. This makes it possible to prevent displacement and detachment of the lens 2, lens barrel 3, sealing glass 4, circuit board 6, and housing 7 due to temperature changes and impacts. As a result, for example, it is possible to prevent optical axis deviation and focus deviation with respect to the image sensor 5, and color tone changes due to misalignment of the infrared cut filter (sealing glass 4).

[0072] 1, the cured body 8 is disposed at each of the adhesion locations (1) to (4), but for example, although not shown, the cured body 8 may be disposed at any one of the adhesion locations (1) to (4). In particular, from the viewpoint of being directly affected by the lens 2, it is preferable that the cured body 8 be disposed at least at the adhesion location (1).

[0073] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples. Various materials used and physical property measurement conditions are described below.

[0074] (A) Epoxy compounds A-1: ​​"Celloxide 2081" (the following alicyclic epoxy compound, manufactured by Daicel Corporation) A-2: "Celloxide 2021P" (the following alicyclic epoxy compound, manufactured by Daicel Corporation) A-3: "jER828" (bisphenol A type epoxy resin, weight average molecular weight 370, manufactured by Mitsubishi Chemical Corporation)

[0075]

[0076] (B) Oxetane Compounds B-1: 3-Ethyl-3-hydroxymethyloxetane (OXT-101, manufactured by Toagosei Co., Ltd.) (C) Silane Coupling Agents C-1: 3-Glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Silicones Co., Ltd.) (D) Photoacid Generators D-1: Diphenyl[4-(phenylthio)phenyl]sulfonium hexafluoroantimonate (CPI-101A, manufactured by San-Apro Co., Ltd.)

[0077] (E) Silica E-a: Sunsil SS-15 (manufactured by Tokuyama Corporation, D50: 1.44 μm, specific surface area: 2 m ２ / g, D10 / D90: 0.53) E-b: Sunsil SS-10 (manufactured by Tokuyama Corporation, D50: 1.10 μm, specific surface area: 3 m ２ / g, D10 / D90: 0.44) E-c: Sunsil SS-07 (manufactured by Tokuyama Corporation, D50: 0.72 μm, specific surface area: 4 m ２ / g, D10 / D90: 0.65) E-d: Sunsil SS-04 (manufactured by Tokuyama Corporation, D50: 0.41 μm, specific surface area: 8 m ２ / g, D10 / D90: 0.67) E-e: Sunsil SS-03 (manufactured by Tokuyama Corporation, D50: 0.33 μm, specific surface area: 11 m ２ / g, D10 / D90: 0.63) E-f: Sunsil SS-01 (manufactured by Tokuyama Corporation, D50: 0.16 μm, specific surface area: 15 m ２ / g, D10 / D90: 0.57)

[0078] <Measurement of D10, D50, and D90> 100 mg of silica was mixed with 40 ml of water and irradiated with 40 W ultrasonic waves for 10 minutes to obtain a measurement sample in which the silica was dispersed in water. The particle size distribution of the measurement sample was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Beckman Coulter: LS13 320). In the obtained volume frequency distribution of particle sizes (particle size distribution), the volume frequencies were accumulated from the smallest particle size, and the particle size at which the cumulative value reached 10% was defined as D10, the particle size at which the cumulative value reached 50%, and the particle size at which the cumulative value reached 90% was defined as D90.

[0079] <Measurement of Specific Surface Area> A measurement sample was prepared by drying 2 g of silica in a nitrogen gas flow at 100° C. for 1 hour. The specific surface area of ​​the measurement sample was measured by the BET method (single-point nitrogen adsorption method) using a rapid surface area analyzer (SA-1000, manufactured by Shibata Scientific Co., Ltd.).

[0080] <Measurement of Sphericity> 1000 silica particles contained in the silica were observed using a scanning electron microscope (SEM), and the sphericity of each particle was measured and the average value was calculated. The measurement was performed using an image processing program (AnalySIS manufactured by Soft Imaging System GmbH). The sphericity was calculated as 4π × (area) / (perimeter). ２ As a result, it was found that all of the silica used had an average sphericity of more than 0.9 and was spherical silica.

[0081] <Determination of Independence> The value of (specific surface area) / (calculated value of specific surface area) was calculated to determine whether the silica particles were independent particles. The calculated value of specific surface area was calculated by 6 / (density x D50). The density of silica was 2.2 g / cm ３As a result, it was found that the above values ​​were in the range of 0.85 to 1.35 for all of the silicas used, and were independent.

[0082] <Measurement of fluidity> 0.2 mL of the adhesive from each example and comparative example was aspirated and dispensed using a dropper with a tip diameter of 2 mm. If the adhesive could be easily aspirated into the dropper and dispensed, it was evaluated as "good." If resistance was felt during aspirating or dispensing, or if air was mixed into the dropper, it was evaluated as "poor."

[0083] <Measurement of Linear Expansion Coefficient> The adhesive of each Example and Comparative Example was poured into a block-shaped mold, irradiated with ultraviolet light from the top and bottom for 5 minutes each, and heated at 100°C for 1.5 hours to produce a cured adhesive. This cured adhesive was then polished to a size of 12 mm x 6 mm x 5.5 mm to obtain a measurement sample. Each measurement sample was measured using a thermomechanical analyzer (NETZSCH: TMA4000SE) by the compression loading method under the following conditions: sample length 12 mm, load 10 g, temperature range 40 to 300°C, and heating rate 5°C / min. The linear expansion coefficient (CTE α1) was calculated based on the slope of the change in linear expansion coefficient from 50°C to 100°C.

[0084] <Measurement of Storage Modulus> The adhesive of each Example and Comparative Example was poured into a rectangular mold, irradiated with ultraviolet light from above and below for 5 minutes each, and heated at 100°C for 1.5 hours to produce a cured adhesive. This cured adhesive was then polished to a size of 25 mm x 5 mm x 1 mm to obtain a measurement sample. Each measurement sample was measured using a dynamic viscoelasticity measuring device (NETZSCH: DMA 242 E Artemis) in tensile measurement mode under the following conditions: sample length (chuck distance) 10 mm, frequency 1 Hz, temperature range 10 to 250°C, and heating rate 3°C / min. The storage modulus E' was obtained as the value at 25°C.

[0085] <Measurement of Glass Transition Point> Measurement samples (25 mm x 5 mm x 1 mm cured bodies) for each Example and Comparative Example were obtained in the same manner as in the measurement of storage modulus. Each measurement sample was measured using a dynamic viscoelasticity measuring device in tensile measurement mode under the same conditions as above. The glass transition point was obtained as the peak temperature of the loss tangent given by the loss modulus / storage modulus.

[0086] Example 1 A photocationically curable adhesive was obtained as an adhesive composition of the present example by mixing 20 parts by mass of A-1, 50 parts by mass of A-2, and 20 parts by mass of A-3 as (A) epoxy compounds, 10 parts by mass of B-1 as (B) oxetane compound, 3 parts by mass of C-1 as (C) silane coupling agent, 3 parts by mass of D-1 as (D) photoacid generator, and 128 parts by mass of E-a and 32 parts by mass of E-e as (E) silica. The physical properties of the silica used and the evaluation results of the physical properties of the cured adhesive are shown in Table 1.

[0087] Examples 2 to 6 The adhesives of the examples were obtained in the same manner as in Example 1, except that the type of (E) silica was changed as shown in Table 1. In Example 6, 96 parts by mass of E-b and 64 parts by mass of Ed were mixed as (E) silica.

[0088] Comparative Examples 1 to 6 Comparative adhesives were obtained in the same manner as Example 1, except that the type of (E) silica was changed as shown in Table 1. In Comparative Examples 1 and 2, 160 parts by mass of only (E-1) large particle silica was mixed as the (E) silica. In Comparative Example 3, 152 parts by mass of E-b and 8 parts by weight of E-d were mixed as the (E) silica. In Comparative Example 4, 72 parts by mass of E-b and 88 parts by weight of E-d were mixed as the (E) silica. In Table 1, Comparative Example 6 contains two types of (E-1) large particle silica, but for convenience of the table, E-c is entered in the column for (E-2) small particle silica.

[0089]

[0090] The evaluation results for Examples 1 to 6 all showed good fluidity, and the linear expansion coefficient of the cured product was less than 50 ppm / K and the storage modulus was less than 8 GPa, indicating that the adhesives of each Example had good operability during use and good linear expansion coefficients and storage moduli after curing. Furthermore, the glass transition points were 140°C or higher, indicating that the adhesives also had excellent heat resistance.

[0091] REFERENCE SIGNS LIST 1 camera module 2 lens 3 lens barrel 4 seal glass 5 imaging element 6 circuit board 7 housing 8 hardened body

Claims

1. An adhesive composition comprising (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica, wherein the (E) silica has (E-1) large particle size silica and (E-2) small particle size silica, the average particle size D50 of the (E-1) large particle size silica is 0.5 μm or more and 1.5 μm or less, the average particle size D50 of the (E-2) small particle size silica is less than 0.5 μm, the difference between the average particle size D50 of the (E-1) large particle size silica and the average particle size D50 of the (E-2) small particle size silica is 0.5 μm or more, and the content of the (E-2) small particle size silica in the (E) silica is 10 mass % or more and 50 mass % or less.

2. The adhesive composition described in claim 1, wherein the content of (E) silica per 100 parts by mass of the total of (A) the epoxy compound and (B) the oxetane compound is 100 parts by mass or more and 200 parts by mass or less.

3. An optical device comprising a cured product of the adhesive composition according to claim 1.

4. A method for producing an adhesive composition containing (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica, comprising mixing (E-1) large-particle silica having an average particle diameter D50 of 0.5 μm or more and 1.5 μm or less and (E-2) small-particle silica having an average particle diameter D50 of less than 0.5 μm and a difference from the average particle diameter D50 of the large-particle silica (E-1) of 0.5 μm or more, such that the content of (E-2) small-particle silica in (E) silica is 10% by mass or more and 50% by mass or less.

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