Adhesive composition and method for producing the same and optical device

Abstract

To provide an adhesive composition which has good operability in use and a low linear expansion coefficient and storage modulus of a cured body and a method for producing the same and an optical device whose components hardly shift against temperature changes and shocks.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 and (E-2) a small particle diameter silica, (E-1) the average particle diameter D50 of the large particle diameter silica is 0.5 μm or more and 1.5 μm or less, (E-2) the average particle diameter D50 of the small particle diameter silica is less than 0.5 μm, the difference between (E-1) the average particle diameter D50 of the large particle diameter silica and (E-2) the average particle diameter D50 of the small particle diameter silica is 0.5 μm or more and the content of the small particle diameter silica (E-2) in the silica (E) is 10 mass% or more and 50 mass% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In the production of optical devices such as camera modules for smartphones and in-vehicle optical sensors, when mounting optical components such as lenses and image sensors 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, from the viewpoint of exhibiting excellent adhesive strength and mounting accuracy, an adhesive composition containing an epoxy compound, an oxetane compound, a photocationic polymerization initiator, a silane coupling agent, and silica has been proposed (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 the use environment. 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, and flexibility for relaxing impact, that is, a low storage elastic modulus is required. Further, when using the adhesive, the adhesive is smoothly sucked or discharged by a coating tool such as a syringe 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 operability during use, a cured product having a low linear expansion coefficient and a low storage elastic modulus, and a method for producing the same, and an optical device in which components are less likely to shift with respect to temperature changes and impacts.

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) large-particle-size silica and (E-2) small-particle-size silica, the average particle diameter D50 of (E-1) large-particle-size silica is 0.5 μm or more and 1.5 μm or less, the average particle diameter D50 of (E-2) small-particle-size silica is less than 0.5 μm, the difference between the average particle diameter D50 of (E-1) large-particle-size silica and the average particle diameter D50 of (E-2) small-particle-size silica is 0.5 μm or more, and the content of (E-2) small-particle-size silica in (E) silica is 10% by mass or more and 50% by mass or less, and includes an adhesive composition.

[0008] The present invention [2] includes the adhesive composition according to [1], in which the content of (E) silica with respect to a total of 100 parts by mass of (A) an epoxy compound and (B) an 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 including 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 including mixing (E-1) a large-particle-size silica having an average particle diameter D50 of 0.5 μm or more and 1.5 μm or less and (E-2) a small-particle-size silica having an average particle diameter D50 of less than 0.5 μm and a difference from the average particle diameter D50 of the (E-1) large-particle-size silica of 0.5 μm or more so that 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.

Effects of the Invention

[0011] According to the adhesive composition of the present invention, the operability during use is good, and the linear expansion coefficient and storage elastic modulus after curing are good. Further, according to the optical device of the present invention, displacement of components can be suppressed against temperature changes and impacts.

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 photocation-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, this composition can be cured by a polymerization reaction to bond parts together. Further, since the epoxy compound has a plurality of epoxy groups, the strength of the cured product of this composition is further improved.

[0016] As the epoxy compound, preferably, an alicyclic epoxy compound having an alicyclic structure and an epoxy group is exemplified, 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 exemplified. Since such an epoxy compound has rigidity, in the cured product of this 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 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 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 1represents an alkylene group having 4 to 8 carbon atoms or the like, 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 or the like. R 2 represents an alkylene group having 1 to 3 carbon atoms or the like.

[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., and the like. These may be used alone or in combination of two or more.

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

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

[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] The weight-average molecular weight of the bisphenol type epoxy resin is, from the viewpoint of the linear expansion coefficient of the cured product, for example, 1200 or less, preferably 800 or less, more preferably 600 or less, and, 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.; Epiklon 830, Epiklon 830-S, Epiklon 835, Epiklon 840, Epiklon 840-S, Epiklon 850, Epiklon 850-S, Epiklon 850-LC manufactured by DIC Corporation, etc. 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: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. Also, 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, 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 growth reaction rate of the oxetane compound is faster than that of 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 novolak 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 epoxy compound: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 body 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 in this composition, the adhesive strength 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 mentioned.

[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 the present composition can be further improved.

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

[0035] Examples of the photoacid generator include onium salts that release a Lewis acid upon irradiation with an energy ray or the like. Examples of such onium salts include sulfonium salts, iodonium salts, etc., 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), etc. Examples of the iodonium salt include compounds represented by the following formula (D3) or (D4), etc. These may be used alone or in combination of two or more.

[0036] [Chemical formula]

[0037] In the above formula, X - each 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 for 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 average particle diameter D50 of the large particle size silica is 0.5 μm or more and 1.5 μm or less, preferably 0.7 μm or more and 1.5 μm or less, more preferably 1.2 μm or more and 1.5 μm or less. The value of D10 / D90 of the large particle size silica is preferably 0.7 or less. D10 / D90 is an index indicating the uniformity of the particle size distribution. The smaller this value, the higher the uniformity of the particle size distribution, which means that the number of silica particles of 0.5 μm or more and 1.5 μm or less is large. Thereby, due to the interaction between the large particle size silica and the small particle size silica, it is easy to lower the storage elastic modulus. 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%. Specifically, 100 mg of silica is mixed with 40 ml of water, and the sample dispersed for 10 minutes at an output of 40 W using an ultrasonic homogenizer is measured using a laser diffraction type particle size distribution measuring device, and D10, D50 and D90 can be obtained from the obtained particle size distribution curve.

[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, and, for example, 5 m 2 / g or less, preferably 4.5 m 2 / g or less, more preferably 4 m 2It is below / g. 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 the silica is the BET specific surface area measured by the BET method.

[0042] The 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, with respect to 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 diameter D50 of less than 0.5 μm, and, for example, is 0.1 μm or more, preferably 0.3 μm or more. In the small-particle-size silica, it is preferable that D10 / D90 is 0.7 or less.

[0044] The specific surface area of the small-particle-size silica is, for example, 5 m 2 / g or more, preferably 6.5 m 2 / g or more, more preferably 8 m 2 / g or more, and, for example, 20 m 2 / g or less, preferably 18 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 the silica during storage of the composition can be suppressed, and it has excellent sedimentation resistance. 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 composition can be further improved.

[0045] The content (content ratio) of the small particle size silica in the silica is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and is 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less. Further, with respect to 100 parts by mass of the total amount of the epoxy compound and the oxetane compound, for example, it is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and is, 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 components can be suppressed.

[0046] The difference (particle size difference) between the average particle size D50 of the large particle size silica and the average particle size D50 of the small particle size silica is 0.5 μm or more, preferably 0.8 μm or more, more preferably 1.1 μm or more, and is, for example, 5.0 μm or less, preferably 3.0 μm or less, more preferably 2.0 μm or less. When the particle size difference is less than the above lower limit, in the cured product of the present composition, the voids generated between the silica particles become large, and a delaminated state in which the silica region and the resin region are separated is likely to occur. As a result, the hard silica regions are unevenly distributed, stress concentration is likely to occur in the silica region, and there is a possibility that the storage elastic modulus becomes high.

[0047] The large particle size silica and the small particle size silica are preferably both spherical silica. Specifically, when the shapes of 1000 silica particles contained in the silica are observed with a scanning electron microscope, the sphericity is measured for each particle, and when the average is 0.9 or more, the silica is considered to be spherical silica. The sphericity is 4π×(area) / (perimeter length) 2It is calculated by. 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.

[0048] Also, the large-particle-size silica and the small-particle-size silica are both preferably independent. Being independent means that it is difficult for silica to form aggregates (both primary aggregates and secondary aggregates). Specifically, in 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 × D50), and the density of silica in this calculation is 2.2 g / cm 3 is set to. Thereby, it becomes easy for 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 product of the photocationic curable adhesive.

[0049] The content of the total amount of silica (that is, the total 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, based on 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, while maintaining a low coefficient of linear expansion, an increase in viscosity can be suppressed and fluidity can be enhanced. Therefore, the workability when using the composition by suction or discharge can be improved, or suitable physical properties can be exhibited as an adhesive used for optical devices such as camera modules and optical sensors.

[0050] The silica in this composition may be a commercially available silica for each of the large-particle-size silica and the small-particle-size silica, or may be produced by known methods such as the dry method and the 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 sieving, 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 a flame. Specific examples of the dry method include the method described in WO2020 / 175160. In the dry method, the average particle diameter and the specific surface area 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 average particle diameter and the specific surface area 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.

[0051] This composition has good fluidity, and further, the cured product thereof has a low linear expansion coefficient and a low storage elastic modulus. The reason for this is not clear, but the inventors of the present invention consider it as follows. Note that the present invention is not limited to the following.

[0052] By blending silica in a high content in the adhesive, the proportion of a resin component (a polymer of an epoxy compound and an 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). However, on the other hand, since the proportion of relatively hard silica increases, the storage elastic modulus of the cured body of the adhesive increases, and the flexibility of the cured body decreases. In addition, due to the high content of silica, the fluidity of the adhesive decreases, so that during use, suction and discharge with respect to the discharge device are not smooth, and the operability decreases. Thus, it has been considered difficult to achieve both a low storage elastic modulus and good fluidity while reducing the coefficient of linear expansion with the conventional blending of single silica.

[0053] On the other hand, the inventors of the present invention have solved the above problems by containing, in the adhesive composition of the present invention, two specific types of silica, that is, specific large-particle-size silica and specific small-particle-size silica having a specific particle size difference relationship, in a specific amount. Specifically, by substituting a part of the large-particle-size silica having a low coefficient of linear expansion with small-particle-size silica having a low coefficient of linear expansion, the concentrated stress on the large-particle-size silica is dispersed in the surrounding resin. In addition, by making the particle size difference between the large-particle-size silica and the small-particle-size silica equal to or greater than a specific value, the small-particle-size silica is appropriately arranged in the gaps of the large-particle-size silica, the delamination (separation of silica and resin) is suppressed, and the concentrated stress on the silica region is reduced. By reducing these concentrated stresses, the storage elastic modulus has been reduced. In addition, by adjusting the amount of the small-particle-size silica to an appropriate amount, the decrease in fluidity is suppressed, and it has been achieved to reduce both the coefficient of linear expansion and the storage elastic modulus while having good fluidity.

[0054] (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 the 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.

[0055] (Method for producing the 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 content of the small-particle-size silica in the silica is 10% by mass or more and 50% by mass or less.

[0056] 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.

[0057] Alternatively, (E-1) large-particle-size silica and (E-2) small-particle-size silica may be separately mixed to prepare mixed silica (that is, (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.

[0058] 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.

[0059] (Physical properties of the cured product of the adhesive composition of the present invention) The cured product of this composition is 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, and even more preferably 45 ppm / K or less. If the linear expansion coefficient of the cured product is at or below the above upper limit, 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 site is alleviated, so that displacement and detachment (removal) of the parts due to temperature change can be suppressed. Therefore, according to this composition, an optical device that is less affected thermally 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.

[0060] 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, and even more preferably 7 GPa or less. If the storage elastic modulus of the cured product is at or below the above upper limit, it is excellent in flexibility. Therefore, when fixing parts using this composition, even if the optical device is impacted, the adhesion site absorbs the impact, so that displacement or detachment of the parts due to the impact can be suppressed. Therefore, according to this composition, an optical device that is less affected mechanically 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.

[0061] The glass transition point Tg of the cured product of this composition is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. If the glass transition point of the cured product is at or above the above lower limit, the heat resistance of the adhesion site is excellent. The upper limit is not limited, but for example, it is 250°C or lower, preferably 200°C or lower.

[0062] (Use) The present composition is not limited as long as it is for adhesive use and can be used for adhering various parts. In this composition, it can be adhered (cured) by ultraviolet irradiation, and from the viewpoint that the cured product has a good coefficient of linear expansion and storage modulus, it can be suitably used for manufacturing 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.

[0063] (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.

[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 cured product 8.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The circuit board 6 is fixed to the housing 7 via the 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.

[0069] 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.

[0070] 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 multiple times. In the case of multiple irradiations, for example, first, ultraviolet rays with low illuminance may be irradiated to perform temporary fixing, and then ultraviolet rays with high illuminance may be irradiated 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 application tools such as a dropper and a dispenser may be used.

[0071] The camera module 1 obtained in this way is adhered by the cured product of this composition at the adhesion points (1) to (4) described above. Therefore, the adhesion points are less likely to thermally expand and are excellent in appropriate flexibility. 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 and impacts. As a result, for example, deviation of the optical axis and defocus with respect to the imaging element 5, and color tone changes due to displacement of the infrared cut filter (seal glass 4) can be suppressed.

[0072] In addition, in FIG. 1, the cured product 8 is disposed at all of the adhesion points (1) to (4). However, for example, although not shown, the cured product 8 may be disposed at any one of the adhesion points (1) to (4). In particular, from the viewpoint of being directly affected by the lens 2, it is preferably disposed at least at the adhesion point (1).

Example

[0073] 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.

[0074] (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)

[0075]

Chemical formula

[0076] (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.)

[0077] (E) Silica · E-a: Sansil SS-15 (manufactured by Tokuyama Corporation, D50: 1.44 μm, specific surface area: 2 m 2 / g, D10 / D90: 0.53) · E-b: Sansil SS-10 (manufactured by Tokuyama Corporation, D50: 1.10 μm, specific surface area: 3 m 2 / g, D10 / D90: 0.44) · E-c: Sansil SS-07 (manufactured by Tokuyama Corporation, D50: 0.72 μm, specific surface area: 4 m 2 / g, D10 / D90: 0.65) · E-d: Sansil SS-04 (manufactured by Tokuyama Corporation, D50: 0.41 μm, specific surface area: 8 m 2 / g, D10 / D90: 0.67) · E-e: Sansil SS-03 (manufactured by Tokuyama Corporation, D50: 0.33 μm, specific surface area: 11 m 2 / g, D10 / D90: 0.63) · E-f: Sansil 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 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 volume frequency was accumulated from the smaller particle diameters, and the particle diameter at which the cumulative value 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.

[0079] <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. For the measurement sample, the specific surface area 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).

[0080] <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 the silica used had an average sphericity value exceeding 0.9, indicating that they were spherical silica.

[0081] <Independent Judgment> (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 the silica used had the above value in the range of 0.85 to 1.35, indicating that they were independent.

[0082] <Measurement of Fluidity> 0.2 mL of the adhesive in 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 ×.

[0083] <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.

[0084] <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.

[0085] <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.

[0086] 〔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 photocationic curable adhesive as 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.

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

[0088] [Comparative Examples 1 to 6] 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 and 2, only 160 parts by mass of (E-1) large-particle-size silica was mixed as (E) silica. In Comparative Example 3, 152 parts by mass of E-b and 8 parts by weight of E-d were mixed as (E) silica. In Comparative Example 4, 72 parts by mass of E-b and 88 parts by weight of E-d were mixed as (E) silica. In Table 1, in Comparative Example 6, two types of (E-1) large-particle-size silica are contained, but for the sake of the table, E-c is entered in the column of (E-2) small-particle-size silica.

[0089]

Table 1

[0090] Regarding the evaluation results, in Examples 1 to 6, all had good fluidity, and since the linear expansion coefficient of the cured product was less than 50 ppm / K and the storage elastic modulus was less than 8 GPa, it was found that the adhesives of each example had good operability during use and good linear expansion coefficient and storage elastic modulus after curing. Also, since the glass transition temperature was 140°C or higher, it was also found that they had excellent heat resistance.

Description of Symbols

[0091] 1 Camera module 2 Lens 3 Lens barrel 4 Sealing glass 5 Image sensor 6 Circuit board 7 Housing 8 Hardened body

Claims

1. 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 (E) silica has (E-1) large particle size silica and (E-2) small particle size silica, the average particle size D50 of (E-1) large particle size silica is 0.5 μm or more and 1.5 μm or less, the average particle size D50 of (E-2) small particle size silica is less than 0.5 μm, the difference between the average particle size D50 of (E-1) large particle size silica and the average particle size D50 of (E-2) small particle size silica is 0.5 μm or more, and the content of (E-2) small particle size silica in (E) silica is 10% by mass or more and 50% by mass or less.

2. The adhesive composition according to Claim 1, wherein the content of (E) silica is 100 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass in total of (A) an epoxy compound and (B) an oxetane compound.

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, wherein (E-1) large particle size silica having an average particle size D50 of 0.5 μm or more and 1.5 μm or less and (E-2) small particle size silica having an average particle size D50 of less than 0.5 μm and a difference from the average particle size D50 of (E-1) large particle size silica of 0.5 μm or more are mixed so that the content of (E-2) small particle size silica in (E) silica is 10% by mass or more and 50% by mass or less.

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