Adhesive composition and optical device

Abstract

To provide an adhesive composition which has good storage stability and operability in use and a low linear expansion coefficient of a cured body and an optical device whose components hardly shift against temperature changes.SOLUTION: There is provided 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 silica (E) has (E-1) a large particle diameter silica having an average particle diameter D50 of 0.8 μm or more and (E-2) a small particle diameter silica having an average particle diameter D50 of less than 0.8 μm and the ratio S1 / S2 of the specific surface area S1 of the (E-1) large particle diameter silica to the specific surface area S2 of the (E-2) small particle diameter silica is 0.10 or more and 0.40 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive composition and an optical device.

Background Art

[0002] In the manufacture of optical devices such as camera modules for smartphones and in-vehicle optical sensors, when mounting optical components such as lenses and imaging elements on a substrate or housing, a method of bonding using a photocationic curable adhesive, which is an ultraviolet curable adhesive, is generally adopted. As such a photocationic curable adhesive, 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 from the viewpoint of exhibiting excellent adhesive strength and mounting accuracy (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, an adhesive used for an optical device is required to have a property that displacement or detachment of an optical component hardly occurs due to external factors during use. Specifically, in the cured adhesive, a property of being hardly expanded or shrunk with respect to temperature change, that is, a low linear expansion coefficient is required. In addition, the adhesive is often stored for a certain period before use. In that case, if the components of the adhesive (especially silica) precipitate, unevenness occurs in the properties of the adhesive, and thus storage stability in which components hardly precipitate is required. Furthermore, when using the adhesive, the adhesive is smoothly sucked or discharged by a coating tool such as a syringe or a dispenser, and workability of being disposed at the bonding site is also required.

[0005] An object of the present invention is to provide an adhesive composition having good storage stability and operability during use, and a cured product having a low coefficient of linear expansion, and an optical device in which components are less likely to shift with respect to temperature changes. **Means for Solving the Problems**

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

[0007] The present invention [1] contains (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica, and (E) silica has (E-1) a large particle size silica having an average particle size D50 of 0.8 μm or more and (E-2) a small particle size silica having an average particle size D50 of less than 0.8 μm, and the ratio S1 / S2 of the specific surface area S1 of (E-1) the large particle size silica to the specific surface area S2 of (E-2) the small particle size silica is 0.10 or more and 0.45 or less, and includes an adhesive composition.

[0008] The present invention [2] includes the adhesive composition according to [1], in which the ratio A2 / Aa of the total surface area A2 of (E-2) the small particle size silica to the total surface area Aa of (E) silica is 0.35 or more and 0.70 or less.

[0009] The present invention [3] includes the adhesive composition according to [1] or [2], in which the content of (E) silica with respect to 100 parts by mass in 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.

[0010] The present invention [4] includes an optical device including a cured product of the adhesive composition according to any one of [1] to [3]. **Advantages of the Invention**

[0011] According to the adhesive composition of the present invention, the storage stability and the operability during use are good, and the coefficient of linear expansion after curing is good. Further, according to the optical device of the present invention, it is possible to suppress the positional shift of components with respect to temperature changes.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0014] An example of the adhesive composition of the present invention (hereinafter, also referred to as "the present composition") is a photo cation-curable adhesive, and contains (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica. Hereinafter, each component will be described in detail.

[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 to each other. Further, since the epoxy compound has a plurality of epoxy groups, the strength of the cured product of the present composition is further improved.

[0016] As the epoxy compound, preferably, an alicyclic epoxy compound having an alicyclic structure and an epoxy group is mentioned, and more preferably, an alicyclic epoxy compound having an epoxy group (alicyclic epoxy group) composed of two adjacent carbon atoms and an oxygen atom constituting the alicyclic ring is mentioned. Since such an epoxy compound has rigidity, in the cured product of the present composition, volume expansion due to heat 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 an alicyclic epoxy group and a non-alicyclic epoxy group. Preferably, all 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 this composition, preferably, at least the compound of formula (A1) is used. More preferably, the alicyclic epoxy compound of formula (A1) and the alicyclic epoxy compound of formula (A2) and / or (A3) are used in combination.

[0019]

Chemical formula

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

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

[0022] When using the alicyclic epoxy compound of formula (A1) in combination with other alicyclic epoxy compounds (for example, alicyclic epoxy compounds of formula (A2) and / or formula (A3)), the blending ratio of these is such that other alicyclic epoxy compound:alicyclic epoxy compound of formula (A1) is, by mass ratio, for example, 1:1 to 6:1, preferably 2:1 to 3:1. Thereby, the linear expansion coefficient and storage elastic modulus of the cured product of this composition can be made even better.

[0023] In addition to the above alicyclic epoxy compound, this composition may further contain a bisphenol type epoxy resin as the epoxy compound. Thereby, the crosslink density of the cured product of this composition can be adjusted to make the linear expansion coefficient and storage elastic modulus good.

[0024] Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD type epoxy resin, and the like.

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

[0026] Specific examples of the bisphenol type epoxy resin include jER806, jER806H, jER807, jER825, jER827, jER828, jER828EL, jER828US, jER828XA, jER834 manufactured by Mitsubishi Chemical Corporation; YD-8125, YDF-8170C manufactured by Nippon Steel Chemical & Material Co., Ltd.; Epiclon 830, Epiclon 830-S, Epiclon 835, Epiclon 840, Epiclon 840-S, Epiclon 850, Epiclon 850-S, Epiclon 850-LC manufactured by DIC Corporation, and the like. 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, preferably 3:1 to 4:1. Thereby, the linear expansion coefficient, storage elastic modulus, glass transition point, etc. can be adjusted to desired values as an adhesive used for optical devices such as camera modules or optical sensors. Further, the content of the total epoxy compound in this composition is, for example, 10% by mass or more, preferably 25% by mass or more, and is, for example, 60% by mass or less, preferably 45% by mass or less. Thereby, the adhesive strength and mounting accuracy are further improved.

[0028] (B) Oxetane compound The oxetane compound has one or more oxetane groups in the molecule. Since the oxetane compound has a faster growth reaction rate than the epoxy compound, when this composition contains the oxetane compound, the polymerization reaction during curing can proceed efficiently, the brittleness peculiar to the epoxy resin can be reduced, and the flexibility and toughness can be improved.

[0029] Examples of the oxetane compound 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, and the like. These may be used alone or in combination of two or more.

[0030] The content of the oxetane compound is such that the mass ratio of the epoxy compound to the oxetane compound is, for example, 4:1 to 20:1, preferably 8:1 to 10:1. Thereby, the balance between the curing rate and the physical properties of the cured product can be made good.

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

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

[0033] The content of the silane coupling agent is, 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, based on 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, and is, 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 this way, the adhesiveness of this composition can be further improved.

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

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

[0036] [Chemical formula]

[0037] In the above formula, X - represents an anion such as SbF6 - , PF6 - , PF3(C2F5)3 - , B(C6F5)4 - , BF4 - , AsF6 - and the like.

[0038] The content of the photoacid generator is, 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, based on 100 parts by mass of the total amount of the epoxy compound and the oxetane compound. By setting the content in this way, the composition can be cured by ultraviolet irradiation in an even shorter time.

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

[0040] (E-1) Large-particle-size silica The large-particle-size silica has an average particle diameter D50 of 0.8 μm or more, preferably 1.0 μm or more, more preferably 1.1 μm or more, and, for example, 5.0 μm or less, preferably 2.0 μm or less, more preferably 1.5 μm or less, still more preferably 1.3 μm or less. The large-particle-size silica preferably has a narrow particle size distribution. Specifically, the value of D10 / D90 is preferably 0.7 or less. In the present invention, D10, D50, and D90 are the particle diameters at which the volume cumulative in the particle size distribution curve determined by the laser diffraction method is 10%, 50%, and 90%, respectively. Specifically, D10, D50, and D90 can be determined from the particle size distribution curve obtained by measuring a sample prepared by mixing 100 mg of silica with 40 ml of water and dispersing it with an ultrasonic homogenizer at an output of 40 W for 10 minutes using a laser diffraction type particle size distribution measuring device.

[0041] The specific surface area of the large-particle-size silica is, for example, 0.5 m 2 / g or more, preferably 1 m 2 / g or more, more preferably 1.5 m 2 / g or more, still more preferably 2.5 m 2 / g or more, and, for example, 3.5 m 2 / g or less. By setting the specific surface area of the large-particle-size silica within the above range, even when the composition contains silica in a high content, an increase in viscosity can be suppressed and high fluidity can be ensured. The specific surface area of silica is the BET specific surface area measured by the BET method.

[0042] The content ratio (content) of the large-particle-size 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. Also, based on 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, it is, 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.

[0043] (E-2) Small particle size silica The small particle size silica has an average particle size D50 of less than 0.8 μm, preferably 0.75 μm or less, more preferably 0.6 μm or less, still more preferably 0.45 μm or less, and also, for example, 0.1 μm or more, preferably 0.25 μm or more, more preferably 0.4 μm or more. In the small particle size silica, D10 / D90 is preferably 0.7 or less.

[0044] The specific surface area of the small particle size silica is, for example, 3.5 m 2 / g or more, preferably 6 m 2 / g or more, more preferably 8 m 2 / g or more, and also, for example, 30 m 2 / g or less, preferably 20 m 2 / g or less, more preferably 16 m 2 / g or less. By setting the specific surface area of the small particle size silica to be not less than the above lower limit, sedimentation of silica during storage of the present composition can be suppressed, and it has excellent sedimentation resistance, that is, storage stability. Also, by setting the specific surface area of the small particle size silica to be not more than the above upper limit, the fluidity of the present composition can be further improved.

[0045] The content ratio of the small particle size silica in the silica is, for example, 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and also, for example, 50% by mass or less, preferably 35% by mass or less, more preferably 28% by mass or less. Also, based on 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, it 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 also, 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 the small particle size silica within the above range, while maintaining the fluidity of the present composition, the storage elastic modulus of the cured product of the present composition can be reduced (improved). Therefore, in the optical device adhered by the cured product of the present composition, the influence of impact can be mitigated, and displacement or dropping of the components can be suppressed.

[0046] In this composition, the ratio of the specific surface area S1 of the large-particle-size silica to the specific surface area S2 of the small-particle-size silica, that is, S1 / S2, is 0.10 or more and 0.45 or less. Preferably, it is 0.25 or more and 0.40 or less. Thereby, both the storage stability and the fluidity of this composition can be made good.

[0047] The ratio of the total surface area A2 of the small-particle-size silica to the total surface area Aa of the silica, that is, A2 / Aa, is, for example, 0.35 or more, preferably 0.40 or more, and, for example, 0.70 or less, preferably 0.65 or less. Thereby, the sedimentation resistance and the fluidity can be made even better. The total surface area A2 of the small-particle-size silica is the surface area in the whole small-particle-size silica, and A2 = [specific surface area of the small-particle-size silica (m 2 / g)] × [content ratio (mass%) of the small-particle-size silica in the silica] × [total weight of the silica (g)] is calculated by the formula. The total surface area A1 of the large-particle-size silica is the surface area in the whole large-particle-size silica, and A1 = [specific surface area of the large-particle-size silica (m 2 / g)] × [content ratio (mass%) of the large-particle-size silica in the silica] × [total weight of the silica (g)] is calculated by the formula. The total surface area of the silica is the surface area in the whole silica and is the sum of A1 and A2. From the above, the above ratio is derived from the formula A2 / Aa = [A2 / (A1 + A2)] to the following formula (1).

[0048]

Equation

[0049] In the formula, S1 is the specific surface area of the large-particle-size silica (m 2 / g), M1 is the content ratio (mass%) of the large-particle-size silica in the silica, S2 is the specific surface area of the small-particle-size silica (m 2 / g), and M2 is the content ratio (mass%) of the small-particle-size silica in the silica.

[0050] The large-particle-size silica and the small-particle-size silica are preferably both spherical silica. Specifically, when 1000 silica particles contained in the silica are observed with a scanning electron microscope, the sphericity of each particle is measured, and when the average is 0.9 or more, the silica is considered to be spherical silica. The sphericity is calculated by 4π×(area) / (perimeter length). 2 It is calculated by this formula. The measurement can be carried out using an image processing program (for example, AnalySIS manufactured by Soft Imaging System GmbH). Thereby, even if the composition contains silica in a high content, an increase in viscosity can be suppressed and high fluidity can be ensured.

[0051] Also, the large-particle-size silica and the small-particle-size silica are both preferably independent. Being independent means that it is difficult for the silica to form aggregates (both primary aggregates and secondary aggregates). Specifically, in the silica, (specific surface area) / (calculated value of specific surface area) is in the range of 0.85 or more and 1.35 or less. The specific surface area is measured by the BET method. The calculated value of the specific surface area is calculated by 6 / (density×D 50 ), and the density of silica in this calculation is 2.2 g / cm 3 . Thereby, it becomes easier for the silica to exist independently without aggregating in the composition, and stress concentration is less likely to occur, so it becomes easy to lower the storage elastic modulus of the cured body of the photocationic curable adhesive.

[0052] The content of the total silica (i.e., the sum of the large-particle-size silica and the small-particle-size silica) is, for example, 90 parts by mass or more, preferably 100 parts by mass or more, more preferably 130 parts by mass or more, with respect to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, and is, 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 blending amount of silica within the above range, it is possible to suppress an increase in viscosity and enhance fluidity while maintaining a low coefficient of linear expansion. Therefore, when the composition is used by suction or discharge, the workability can be improved, and suitable physical properties can be exhibited as an adhesive used for optical devices such as camera modules and optical sensors.

[0053] As the silica in the present composition, commercially available silica may be used for each of the large-particle-size silica and the small-particle-size silica, or it may be produced by known methods such as a dry method and a wet method. Further, the commercially available or produced silica may be used after adjusting the specific surface area to a desired range by means of a sieve, air classification, or the like. The dry method is a method of generating silica powder by burning a silicon compound and growing it in and near the flame. Specific examples of the dry method include the method described in WO2020 / 175160. In the dry method, the specific surface area and the average particle diameter can be adjusted by adjusting the combustion and cooling conditions of the flame and the amount of preheating. Examples of the wet method include the sol-gel method. The sol-gel method is a method of generating a silica sol by hydrolyzing and polycondensing a silicon alkoxide in a reaction medium containing a catalyst, and then gelling and drying it. A specific example of the sol-gel method is the method described in WO2018 / 096876. In the sol-gel method, the specific surface area and the average particle diameter can be adjusted by adjusting the reaction temperature, the concentration of the reaction solution, and the dropping rate of the reaction solution. Further, the silica may be surface-treated with a silane coupling agent or the like.

[0054] This composition has good storage stability and fluidity, and furthermore, its cured body has a low coefficient of linear expansion. Although the reason for this is not clear, the inventors of the present invention consider it as follows. Note that the present invention is not limited to the following content.

[0055] By blending silica in a high content in the adhesive, the proportion of the resin component (polymer of epoxy compound and oxetane compound) having a relatively large coefficient of linear expansion can be reduced, and the coefficient of linear expansion of the cured body of the adhesive can be reduced (improved). At this time, when silica having a large particle size and a small specific surface area is contained at a high ratio as in Patent Document 1, the large particle size silica is likely to settle, so there is a problem in terms of storage stability.

[0056] On the other hand, the inventors of the present invention have solved the above problems by containing silica having two specific specific surface areas in the adhesive composition of the present invention. Specifically, by combining and containing large particle size silica and small particle size silica whose specific surface areas satisfy a specific relationship, the small particle size silica is arranged in a well-balanced manner between the large particle size silica in the adhesive. As a result, it is considered that the sedimentation of the large particle size silica can be suppressed by the small particle size silica. Here, when small particle size silica having a large specific surface area is used, the interaction between the small particle size silica and the resin is large, which may be a factor in reducing the fluidity of the adhesive composition. However, in the present invention, the excessive interaction between the small particle size silica and the resin can be suppressed by the presence of the large particle size silica, and good fluidity can be obtained. As a result, the storage stability and fluidity are efficiently exhibited. Thus, the present composition and its cured body exhibit good storage stability and fluidity while having a low coefficient of linear expansion, even when the proportion of silica in the adhesive is the same as that of the prior art.

[0057] (Other components) The composition may contain other components other than (A) to (E) as long as the effects of the present invention are not inhibited. Examples of other components include fillers other than silica, thermal cationic polymerization initiators, curing accelerators, flame retardants, rubber particles, thickeners, defoamers, leveling agents, antioxidants, colorants, photosensitizers, and the like. In the present composition, from the viewpoint of achieving both a linear thermal expansion coefficient and a storage elastic modulus, it is preferable that the filler consists only of silica.

[0058] (Method for producing an adhesive composition) As an example of the 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-size silica, and (E-2) small-particle-size silica are mixed so that the ratio S1 / S2 of the specific surface area of the large-particle-size silica to the specific surface area of the small-particle-size silica is within the above range.

[0059] For example, (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, (E-1) large-particle-size silica, and (E-2) small-particle-size silica may be mixed simultaneously, or these components may be mixed in an appropriate order.

[0060] Alternatively, (E-1) large-particle-size silica and (E-2) small-particle-size silica may be separately mixed to prepare mixed silica (i.e., (E) silica), and this (E) silica may be mixed with (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, and (D) a photoacid generator. At this time, the mixing order of (A), (B), (C), (D), and (E) is not limited. For example, all of these may be mixed simultaneously, or they may be mixed in an appropriate order.

[0061] The mixing method is not limited. For example, it can be produced by a known method using a known mixing device such as a blender or a mixer. If necessary, the mixing may be carried out in a heating atmosphere or an inert gas atmosphere.

[0062] (Physical properties of the cured product of the adhesive composition of the present invention) The cured product of this composition can be obtained by performing the curing method described below on this composition. The linear expansion coefficient of the cured product of this composition is preferably 60 ppm / K or less, more preferably 50 ppm / K or less, still more preferably 45 ppm / K or less. If the linear expansion coefficient of the cured product is below the above upper limit, the thermal expansion and thermal contraction are small, and it is excellent in low expansibility. Therefore, when fixing parts of an optical device (for example, a lens, an imaging device, etc.) using this composition, even if the optical device is heated or cooled, the volume change at the adhesion point is alleviated, so that the positional displacement and detachment (removal) of the parts due to temperature change can be suppressed. Thus, according to this composition, an optical device that is less affected by heat can be provided. The lower limit is not limited, but for example, it is 30 ppm / K or more, preferably 35 ppm / K or more. The linear expansion coefficient can be measured, for example, by the compression loading method using a thermomechanical analyzer.

[0063] The storage elastic modulus E´ of the cured product of this composition is preferably 8 GPa or less, more preferably 7.5 GPa or less, still more preferably 7 GPa or less. If the storage elastic modulus of the cured product is below the above upper limit, it is excellent in flexibility. Therefore, when fixing parts using this composition, even if the optical device is subjected to an impact, the adhesion point absorbs the impact, so that the positional displacement or detachment of the parts due to the impact can be suppressed. Thus, according to this composition, an optical device that is less affected by mechanical forces can be provided. The lower limit is not limited, but for example, it is 4 GPa or more, preferably 5 GPa or more. The storage elastic modulus E´ is, for example, the value at 25 °C when measured under the condition of a frequency of 1 Hz using a dynamic viscoelasticity measuring device for a cured product with a thickness of 1 mm.

[0064] The glass transition point Tg of the cured product of this composition is preferably 125 °C or higher, more preferably 130 °C or higher, still more preferably 140 °C or higher. If the glass transition point of the cured product is above the above lower limit, the heat resistance of the adhesion point is excellent. The upper limit is not limited, but for example, it is 250 °C or lower, preferably 200 °C or lower.

[0065] (Use) The present composition is not limited as long as it is for adhesive use, and can be used for adhering various parts. In the present composition, it can be adhered (cured) by ultraviolet irradiation, and from the viewpoint that the cured product has a good coefficient of linear expansion, it can be suitably used for the production of optical devices. An optical device is a device equipped with optical components such as lenses and mirrors, and examples include a camera module and an optical sensor equipped with the module. Such optical components such as camera modules and optical sensors are designed according to various usage purposes such as for smartphones and in-vehicle use. Hereinafter, an example of using it for adhering a camera module will be described below as the use of the present composition.

[0066] (Camera module) An example of a camera module including the cured product of the adhesive of the present invention will be described with reference to FIG. 1.

[0067] 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 cured product 8.

[0068] The lens 2 is fixed to the lens barrel 3 via the cured product 8 inside the lens barrel 3. That is, the cured product 8 is disposed between the outer peripheral surface of the lens 2 and the inner peripheral surface of the lens barrel 3.

[0069] The lens barrel 3 is fixed to the housing 7 via the cured product 8 inside the housing 7. That is, the cured product 8 is disposed between the outer peripheral surface of the housing 3 and the inner peripheral surface of the housing 7.

[0070] The seal glass 4 is fixed to the housing 7 via the cured product 8 inside the housing 7. That is, the cured product 8 is disposed between the outer peripheral surface of the seal glass 4 and the inner peripheral surface of the housing 7. Note that the seal glass 4 may also serve as an infrared cut filter having a function of blocking infrared rays.

[0071] The circuit board 6 is fixed to the housing 7 via a cured body 8 on its upper surface (the surface on the lens 2 side). That is, the cured body 8 is disposed between the upper surface of the circuit board 6 and the lower surface of the housing 7. Further, the imaging element 5 is mounted on the circuit board 6.

[0072] The camera module 1 of the present invention is produced by applying or flowing the present composition to each of (1) the adhesion portion between the lens 2 and the lens barrel 3, (2) the adhesion portion between the seal glass 4 and the housing 7, (3) the adhesion portion between the lens barrel 3 and the housing 7, and (4) the adhesion portion between the circuit board 6 and the housing 7, and then curing it.

[0073] Examples of the curing method of the present composition include ultraviolet irradiation. The illuminance and time in ultraviolet irradiation are not limited as long as the resin component of the present composition reacts. For example, 10 mW / cm 2 to 1000 mW / cm 2 or less and 10 seconds to 10 minutes or more may be sufficient. The number of irradiations may be only once or a plurality of times. In the case of multiple irradiations, for example, first irradiate with ultraviolet light of low illuminance to perform temporary fixing, and then irradiate with ultraviolet light of high illuminance to perform permanent fixing. Further, after ultraviolet irradiation, a heating step may be performed. Thereby, post-curing can be promoted, and heat distortion due to ultraviolet irradiation can be released to increase the adhesion strength. As the heating conditions, for example, the temperature may be 50°C or higher and 150°C or lower for 0.5 hours or more and 5 hours or less. As a method for applying and flowing the present composition, for example, known coating tools such as a dropper and a dispenser may be used.

[0074] The camera module 1 thus obtained is adhered by the cured body of the present composition at the adhesion portions (1) to (4) above. Therefore, the adhesion portions are less likely to thermally expand. Thus, displacement and detachment of the lens 2, the lens barrel 3, the seal glass 4, the circuit board 6, and the housing 7 can be suppressed against temperature changes. As a result, for example, optical axis displacement and focus displacement with respect to the imaging element 5, color tone changes due to displacement of the infrared cut filter (seal glass 4), etc. can be suppressed.

[0075] In FIG. 1, the cured body 8 is disposed at all of the bonding portions (1) to (4). However, for example, although not shown, the cured body 8 may be disposed at any one of the bonding portions (1) to (4). In particular, from the viewpoint of directly affecting the lens 2, it is preferably disposed at least at the bonding portion (1).

Example

[0076] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited to these examples and comparative examples. The various materials used and the physical property measurement conditions are described below.

[0077] (A) Epoxy compound · 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)

[0078]

Chemical formula

[0079] (B) Oxetane compound · B-1: 3-ethyl-3-hydroxymethyloxetane (“OXT-101”, manufactured by Toagosei Co., Ltd.) (C) Silane coupling agent · C-1: 3-glycidoxypropyltrimethoxysilane (“KBM-403”, manufactured by Shin-Etsu Silicone Co., Ltd.) (D) Photoacid generator · D-1: Diphenyl [4-(phenylthio)phenyl] sulfonium hexafluoroantimonate (“CPI-101A”, manufactured by San-Apro Ltd.)

[0080] (E) Silica ·E-a: Sanshiru SS-15 (manufactured by Tokuyama Corporation, D50: 1.44 μm, specific surface area: 2 m 2 / g, D10 / D90: 0.53) ·E-b: Sanshiru SS-10 (manufactured by Tokuyama Corporation, D50: 1.10 μm, specific surface area: 3 m 2 / g, D10 / D90: 0.44) ·E-c: Sanshiru SS-07 (manufactured by Tokuyama Corporation, D50: 0.72 μm, specific surface area: 4 m 2 / g, D10 / D90: 0.65) ·E-d: Sanshiru SS-04 (manufactured by Tokuyama Corporation, D50: 0.41 μm, specific surface area: 8 m 2 / g, D10 / D90: 0.67) ·E-e: Sanshiru SS-03 (manufactured by Tokuyama Corporation, D50: 0.33 μm, specific surface area: 11 m 2 / g, D10 / D90: 0.63) ·E-f: Sanshiru SS-01 (manufactured by Tokuyama Corporation, D50: 0.16 μm, specific surface area: 15 m 2 / g, D10 / D90: 0.57) ·E-g: Shirufiru NSS-3N (manufactured by Tokuyama Corporation, D50: 0.12 μm, specific surface area: 30 m 2 / g, D10 / D90: 0.38)

[0081] <Measurement of D10, D50, and D90> 100 mg of silica was mixed with 40 ml of water, and the mixture was irradiated with 40 W ultrasonic waves for 10 minutes to obtain a measurement sample in which silica was dispersed in water. The particle size distribution of the measurement sample was measured using a laser diffraction scattering type particle size distribution analyzer (manufactured by Beckman Coulter, Inc.: LS13 320). In the volume frequency distribution (particle size distribution) of the obtained particle diameters, the particle diameter at which the cumulative volume frequency from the smaller particle diameter became 10% was defined as D10, the particle diameter at which the cumulative value became 50% was defined as D50, and the particle diameter at which the cumulative value became 90% was defined as D90.

[0082] <Measurement of Specific Surface Area> 2 g of silica was dried at 100 °C for 1 hour in a nitrogen gas flow to obtain a measurement sample. The specific surface area of the measurement sample was measured by the BET method (nitrogen adsorption single-point method) using a rapid specific surface area measuring device (manufactured by Shibata Scientific Technology Ltd.: SA-1000).

[0083] <Measurement of sphericity> 1000 silica particles contained in silica were observed using a scanning electron microscope (SEM), the sphericity of each particle was measured, and the average value was determined. The measurement was carried out using an image processing program (AnalySIS manufactured by Soft Imaging System GmbH), and the sphericity was calculated by 4π×(area) / (perimeter length). 2 As a result, all of the silica used had an average sphericity value exceeding 0.9, indicating that they were spherical silica.

[0084] <Independent determination> (Specific surface area) / (calculated value of specific surface area) was calculated to determine whether the silica was independent particles. The calculated value of the specific surface area was calculated by 6 / (density×D50). The density of silica was 2.2 g / cm 3 was used. As a result, all of the silica used had the above value in the range of 0.85 to 1.35, indicating that they were independent.

[0085] <Measurement of sedimentation resistance> The adhesives of each example and each comparative example were allowed to stand for 1 week. At this time, if the resin component and silica in the adhesive were not separated, it was evaluated as ○. If the resin component and silica were separated and the silica had sedimented, it was evaluated as ×.

[0086] <Measurement of fluidity> 0.2 mL of the adhesives of each example and each comparative example was aspirated and discharged using a dropper with a tip diameter of 2 mm. At this time, if the adhesive could be easily aspirated and discharged into the dropper, it was evaluated as ○. If resistance was felt during aspiration or discharge, or air was mixed into the dropper, it was evaluated as ×.

[0087] <Measurement of linear expansion coefficient> The adhesives of each example and each comparative example were poured into a block-shaped mold, irradiated with ultraviolet light from the upper and lower surfaces for 5 minutes each, and heated at 100 °C for 1.5 hours to produce cured bodies of the adhesives. These cured bodies were polished and formed to be 12 mm × 6 mm × 5.5 mm to obtain measurement samples. Using a thermomechanical analyzer (manufactured by NETZSCH: TMA4000SE), each measurement sample was measured under the conditions of a sample length of 12 mm, a load of 10 g, a temperature range of 40 to 300 °C, and a heating rate of 5 °C / min by the compression loading method. The linear expansion coefficient (CTE α1) was calculated based on the slope of the change in linear expansion rate from 50 °C to 100 °C.

[0088] <Measurement of Storage Elastic Modulus> The adhesives of each example and each comparative example were poured into a strip-shaped mold, irradiated with ultraviolet light from the upper and lower surfaces for 5 minutes each, and heated at 100 °C for 1.5 hours to produce cured bodies of the adhesives. These cured bodies were polished and formed to be 25 mm × 5 mm × 1 mm to obtain measurement samples. Using a dynamic viscoelasticity measuring device (manufactured by NETZSCH: DMA 242 E Artemis), each measurement sample was measured in the tensile measurement mode under the conditions of a sample length (distance between chucks) of 10 mm, a frequency of 1 Hz, a temperature range of 10 to 250 °C, and a heating rate of 3 °C / min. The storage elastic modulus E´ was obtained as the value at 25 °C.

[0089] <Measurement of Glass Transition Temperature> In the same manner as the measurement of the storage elastic modulus, measurement samples (cured bodies of 25 mm × 5 mm × 1 mm) of each example and each comparative example were obtained. Using a dynamic viscoelasticity measuring device, each measurement sample was measured in the tensile measurement mode under the same conditions as above. The glass transition temperature was obtained as the peak temperature of the loss tangent given by the loss elastic modulus / storage elastic modulus.

[0090] 〔Example 1〕 (A) As epoxy compounds, 20 parts by mass of A-1, 50 parts by mass of A-2 and 20 parts by mass of A-3, (B) as an oxetane compound, 10 parts by mass of B-1, (C) as a silane coupling agent, 3 parts by mass of C-1, (D) as a photoacid generator, 3 parts by mass of D-1, and (E) as silica, 128 parts by mass of E-a and 32 parts by mass of E-e were mixed to obtain a photocation-curable adhesive which is the adhesive composition of the example. Table 1 shows the physical properties of the silica used and the evaluation results of the physical properties of the cured product of the adhesive. Also shown in Table 1 are the results of calculating the ratio (S1 / S2) of the specific surface area S1 of the large-particle-size silica to the specific surface area S2 of the small-particle-size silica, and the ratio (A2 / Aa) of the surface area A2 of the small-particle-size silica to Aa with respect to the surface area of the silica.

[0091] 〔Examples 2 to 5〕 As shown in Table 1, adhesives of the examples were obtained in the same manner as in Example 1 except that the type and content of (E) silica were changed. In Example 5, 112 parts by mass of E-b and 48 parts by mass of E-d were used as (E) silica.

[0092] 〔Comparative Examples 1 to 4〕 As shown in Table 1, adhesives of the comparative examples were obtained in the same manner as in Example 1 except that the type of (E) silica was changed. In Comparative Examples 1 to 4, the total amount of (E) silica was 160 parts by mass.

[0093]

Table 1

[0094] Regarding the evaluation results, in Examples 1 to 5, in all cases, the sedimentation resistance and fluidity were good, and the linear expansion coefficient of the cured product was less than 50 ppm / K. Therefore, it was found that the adhesives of each example had good storage stability and operability during use, and good linear expansion coefficient after curing. Also, since the storage elastic modulus was less than 8 GPa, it was found that the flexibility was good, and since the glass transition point was 140°C or higher, it was also found that the heat resistance was excellent.

Explanation of Symbols

[0095] 1 Camera module 2 Lens 3 Lens barrel 4 Sealing glass 5 Image sensor 6 Circuit board 7 Housing 8 Hardened body

Claims

1. containing (A) an epoxy compound, (B) an oxetane compound, (C) a silane coupling agent, (D) a photoacid generator, and (E) silica, wherein (E) silica has (E-1) large particle size silica having an average particle size D50 of 0.8 μm or more and (E-2) small particle size silica having an average particle size D50 of less than 0.8 μm, Specific surface area S of (E-2) small particle size silica ２ to specific surface area S of (E-1) large particle size silica １ ratio S １ / S ２ is 0.10 or more and 0.45 or less, an adhesive composition.

2. (E) The ratio A ２ of the total surface area A ２ of the small particle size silica (E-2) to the total surface area Aa of the silica is 0.35 or more and 0.70 or less, and the adhesive composition according to claim 1. ２ of ２ Aa is 0.35 or more and 0.70 or less, and the adhesive composition according to claim 1.

3. The adhesive composition according to claim 1, wherein the content of (E) silica with respect to 100 parts by mass in 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.

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

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