JP2024060224A - Resin composition and display device - Google Patents

Abstract

To provide a resin composition that allows for improved visibility.SOLUTION: A resin composition according to the present invention comprises silicone particles and a curable component. The curable component comprises silicone resin. The absolute difference between the refractive index of the silicone particles and the refractive index of a cured product resulting from curing the curable component under conditions of 23°C and 5 hours is equal to or lower than 0.02.SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin composition using silicone particles. The present invention relates to a display device using the resin composition.

Various resin compositions are used as adhesives to bond two adherends. In addition, gap materials (spacers) are sometimes added to the resin compositions to make the thickness of the adhesive layer formed by the adhesive uniform and to control the distance (gap) between the two adherends.

Silicone particles and the like may be used as the gap material.

The following Patent Document 1 discloses coated silicone microparticles (coated particles) having 100 parts by mass of silicone elastomer spherical microparticles with a volume average particle size of 0.1 μm to 100 μm and 0.5 to 25 parts by mass of polyorganosilsesquioxane that coats the surfaces of the spherical microparticles. The polyorganosilsesquioxane is granular and has a size of 60 nm or less.

JP 2013-040241 A

When conventional coated silicone particles such as those described in Patent Document 1 are used as gap materials for adhesives, it is difficult to reduce the refractive index difference between the adhesive and the gap material because the particle diameter of the coated particles is small (the thickness of the coating material is thin). In addition, when the particle diameter of the coated particles is small, it is difficult to uniformly coat the surface of the silicone particles, and the refractive index difference between the adhesive and the gap material may vary. As a result, in a resin composition (adhesive) containing conventional coated silicone particles, it may be difficult to sufficiently improve visibility in the cured product after curing, because the silicone particles become visible or double images occur.

In addition, by adjusting the particle size of the coated particles in conventional coated silicone particles, the refractive index difference between the adhesive and the gap material can be reduced to some extent. However, even if the particle size of the coated particles is adjusted, the reduction in the refractive index difference is still not sufficient.

The object of the present invention is to provide a resin composition that can improve visibility. It is also an object of the present invention to provide a display device using the above resin composition.

According to a broad aspect of the present invention, there is provided a resin composition comprising silicone particles and a curable component, the curable component comprising a silicone resin, and the absolute value of the difference between the refractive index of the silicone particles and the refractive index of a cured product obtained by curing the curable component at 23°C for 5 hours is 0.02 or less.

In a particular aspect of the resin composition according to the present invention, the CV value of the particle diameter of the silicone particles is 21% or less.

In a particular aspect of the resin composition according to the present invention, the silicone particles include a silicone particle body and a plurality of inorganic oxide particles, and at least a portion of the inorganic oxide particles are present inside the silicone particle body.

In a particular aspect of the resin composition according to the present invention, the inorganic oxide particle material contains silica.

In a particular aspect of the resin composition according to the present invention, the content of the inorganic oxide particles is 0.1% by weight or more and 9% by weight or less in 100% by weight of the silicone particles.

In a particular aspect of the resin composition according to the present invention, the resin composition is cured at 23°C for 5 hours, and the cured product has a transmittance of 92% or more at a wavelength of 650 nm.

In a particular aspect of the resin composition according to the present invention, the resin composition is an adhesive for optical bonding.

According to a broad aspect of the present invention, there is provided a display device comprising a first member, a second member being an image display element, and an adhesive layer bonding the first member and the second member, the adhesive layer being a cured product of the resin matrix composition described above.

In a particular aspect of the display device according to the present invention, the first member is a transparent protective material.

The resin composition according to the present invention contains silicone particles and a curable component, the curable component contains a silicone resin, and the absolute value of the difference between the refractive index of the silicone particles and the refractive index of a cured product obtained by curing the curable component at 23°C for 5 hours is 0.02 or less. The resin composition according to the present invention has the above-mentioned configuration, and therefore can provide good visibility.

FIG. 1 is a cross-sectional view showing silicone particles in a resin composition according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing silicone particles in a resin composition according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view showing silicone particles in a resin composition according to a third embodiment of the present invention. FIG. 4 is a cross-sectional view showing an example of a display device using the resin composition according to the first embodiment of the present invention.

The details of the present invention are explained below.

<Resin Composition>
The resin composition according to the present invention includes silicone particles and a curable component. In the resin composition, the curable component includes a silicone resin. In the resin composition, the absolute value of the difference between the refractive index of the silicone particles and the refractive index of a cured product obtained by curing the curable component at 23° C. for 5 hours is 0.02 or less.

When conventional coated silicone particles are used as gap materials for adhesives, it is difficult to reduce the refractive index difference between the adhesive and the gap material because the particle diameter of the coated particles is small (the thickness of the coating material is thin). In addition, when the particle diameter of the coated particles is small, it is difficult to uniformly coat the surface of the silicone particles, and the refractive index difference between the adhesive and the gap material may vary. As a result, in resin compositions (adhesives) containing conventional coated silicone particles, the silicone particles may become visible or double images may occur in the cured product after curing, making it difficult to sufficiently improve visibility.

In addition, by adjusting the particle size of the coated particles in conventional coated silicone particles, the refractive index difference between the adhesive and the gap material can be reduced to some extent. However, even if the particle size of the coated particles is adjusted, the reduction in the refractive index difference is still not sufficient, and it is desirable to reduce the refractive index difference even further.

The resin composition according to the present invention has the above-mentioned configuration, and therefore can improve visibility. The resin composition according to the present invention can improve visibility by suppressing the manifestation of silicone particles and suppressing the occurrence of double images in the cured product after curing.

The resin composition according to the present invention is preferably an adhesive. The resin composition is preferably an adhesive for bonding two members. The resin composition is preferably an adhesive for optical bonding.

In the resin composition according to the present invention, the absolute value of the difference between the refractive index (P2) of the silicone particles and the refractive index (P3) of the cured product obtained by curing the curable component under conditions of 23° C. and 5 hours is 0.02 or less. From the viewpoint of further improving visibility, the absolute value of the difference between the refractive index (P2) of the silicone particles and the refractive index (P3) of the cured product obtained by curing the curable component under conditions of 23° C. and 5 hours is preferably 0.019 or less, more preferably 0.017 or less, even more preferably 0.015 or less, even more preferably 0.014 or less, and particularly preferably 0.01 or less. The absolute value of the difference between the refractive index (P2) of the silicone particles and the refractive index (P3) of the cured product obtained by curing the curable component under conditions of 23° C. and 5 hours is most preferably 0.001 or less. The absolute value of the difference between the refractive index (P2) of the silicone particles and the refractive index (P3) of the cured product obtained by curing the curable component under conditions of 23° C. and 5 hours may be 0 or more.

Methods for controlling the absolute value of the difference between the refractive index (P2) of the silicone particles and the refractive index (P3) of the cured product obtained by curing the curable component at 23°C for 5 hours within the above preferred range include the following methods. A method of designing the molecular structure of the monomer of the curable component so that the refractive index of the cured product falls within the desired range. A method of adding a low refractive index component (silica, fluororesin, etc.) to the curable component so that the refractive index of the cured product falls within the desired range (YOT method). The YOT method is generally used because it does not significantly change the physical properties of the cured product and is a simple method.

The refractive index of the cured product obtained by curing the resin composition at 23°C for 5 hours is preferably 1.20 or more, more preferably 1.30 or more, even more preferably 1.38 or more, even more preferably 1.39 or more, particularly preferably 1.40 or more, and most preferably 1.41 or more. The refractive index of the cured product obtained by curing the resin composition at 23°C for 5 hours is preferably 1.60 or less, more preferably 1.50 or less, even more preferably 1.45 or less, even more preferably 1.44 or less, particularly preferably 1.43 or less, and most preferably 1.42 or less. If the refractive index of the cured product obtained by curing the resin composition at 23°C for 5 hours is equal to or greater than the lower limit and equal to or less than the upper limit, the refractive index approaches that of a member (e.g., a transparent protective material) used as a display device, and visibility can be further improved (particularly, the occurrence of double images can be suppressed).

The refractive index of the cured product can be measured as follows:

The resin composition is cured at 23°C for 5 hours to obtain a cured product having a thickness of 0.1 mm. The refractive index of the cured product is measured using, for example, an Abbe refractometer (ERMA's "ER-7MW").

The transmittance at a wavelength of 650 nm of the cured product obtained by curing the resin composition at 23° C. for 5 hours is preferably 92% or more, more preferably 94% or more, and even more preferably 96% or more. The upper limit of the transmittance at a wavelength of 650 nm of the cured product obtained by curing the resin composition at 23° C. for 5 hours is not particularly limited. The transmittance at a wavelength of 650 nm of the cured product obtained by curing the resin composition at 23° C. for 5 hours may be 100% or less, or may be 99.9% or less. When the transmittance at a wavelength of 650 nm of the cured product obtained by curing the resin composition at 23° C. for 5 hours is equal to or greater than the lower limit, visibility can be further improved.

The transmittance at a wavelength of 650 nm of the cured product obtained by curing the resin composition at 23°C for 5 hours can be measured as follows.

The resin composition is cured at 23°C for 5 hours to obtain a cured product having a thickness of 0.1 mm. The obtained cured product is used to measure the transmittance at a wavelength of 650 nm at 25°C. The transmittance can be measured, for example, using a spectrophotometer (double beam spectrophotometer (U-2910 manufactured by Hitachi High-Tech Science Corporation)). An integrating sphere can be used as the detector.

(Silicone particles)
The resin composition according to the present invention includes silicone particles and a curable component. The silicone particles are different from the curable component. In the resin composition, the silicone particles are preferably incompatible with the curable component. In the resin composition, the silicone particles are preferably incompatible with the curable component and are included in the resin composition. In the resin composition, the silicone particles are preferably dispersed in the curable component. In the resin composition, the silicone particles are preferably incompatible with the curable component and dispersed in the curable component. The silicone particles are preferably present as particles in the resin composition.

The method for dispersing the silicone particles in the curable component can be a conventionally known dispersion method, and is not particularly limited. Examples of the method for dispersing the silicone particles in the curable component include the following methods. A method in which the silicone particles are added to the curable component, and then kneaded and dispersed with a planetary mixer or the like. A method in which the silicone particles are uniformly dispersed in water or an organic solvent using a homogenizer or the like, and then added to the curable component, and then kneaded and dispersed with a planetary mixer or the like. A method in which the curable component is diluted with water or an organic solvent, and then the silicone particles are added, and then kneaded and dispersed with a planetary mixer or the like.

The refractive index of the silicone particles can be measured using a method conforming to JIS K7142:2014 Plastics - Determination of refractive index, Method B.

The particle diameter of the silicone particles is preferably 30 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more, and is preferably 500 μm or less, and more preferably 200 μm or less. When the particle diameter of the silicone particles is equal to or more than the above lower limit and equal to or less than the above upper limit, the effect of the present invention is more effectively achieved.

The particle diameter of the silicone particles means the diameter when the silicone particles are spherical, and means the diameter when the silicone particles are assumed to be spherical with a volume equivalent to the volume when the silicone particles are other than spherical. The particle diameter of the silicone particles is preferably the average particle diameter, and more preferably the number average particle diameter. The particle diameter of the silicone particles can be measured by any particle size distribution measuring device. The particle diameter of the silicone particles can be measured by using a particle size distribution measuring device using the principles of laser light scattering, electrical resistance change, and image analysis after imaging. More specifically, the particle diameter of the silicone particles can be measured by using a particle size distribution measuring device (Beckman Coulter's "Multisizer 4") to measure the particle diameter of about 100,000 silicone particles and calculate the average particle diameter.

The coefficient of variation (CV value) of the particle size of the silicone particles is preferably 21% or less, more preferably 16% or less, even more preferably 15% or less, particularly preferably 13% or less, and most preferably 10% or less. If the CV value is equal to or less than the upper limit, the gap can be controlled with high precision when the silicone particles are used as a gap material. Furthermore, the silicone particles can be suitably used for optical bonding applications.

The above CV value is expressed by the following formula:

CV value (%) = (ρ/Dn) × 100
ρ: Standard deviation of the particle size of silicone particles Dn: Average particle size of silicone particles

From the viewpoint of further improving visibility, the silicone particles preferably include a silicone particle body and a plurality of inorganic oxide particles. In the silicone particles, it is preferable that at least a portion of the plurality of inorganic oxide particles is present inside the silicone particle body. In the silicone particles, a portion of the plurality of inorganic oxide particles may be present outside the silicone particle body, or all of the plurality of inorganic oxide particles may be present inside the silicone particle body.

From the viewpoint of improving the dispersibility of the silicone particles, it is preferable that the silicone particles include inorganic oxide particles in which only a portion of the inorganic oxide particles is present inside the silicone particle body. With respect to inorganic oxide particles in which only a portion of the inorganic oxide particles is present inside the silicone particle body, the volume of the portion of each inorganic oxide particle present inside the silicone particle body is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more, based on 100% of the volume of the inorganic oxide particle. With respect to inorganic oxide particles in which only a portion of the inorganic oxide particles is present inside the silicone particle body, the volume of the portion of each inorganic oxide particle present inside the silicone particle body may be less than 100% or may be 99% or less, based on 100% of the volume of the inorganic oxide particle. From the viewpoint of improving the dispersibility of the silicone particles, it is preferable that the silicone particles include inorganic oxide particles in which only a portion of the inorganic oxide particles is present inside the silicone particle body and inorganic oxide particles in which the entire portion of the inorganic oxide particles is present inside the silicone particle body.

In 100% by weight of the resin composition, the content of the silicone particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and preferably 50% by weight or less, more preferably 30% by weight or less, even more preferably 20% by weight or less, particularly preferably 10% by weight or less, and most preferably 5% by weight or less. When the content of the silicone particles is equal to or more than the lower limit and equal to or less than the upper limit, the visibility can be further improved. In addition, when the silicone particles are used as a gap material, the gap can be controlled with high precision. When the content of the silicone particles is equal to or more than the lower limit and equal to or less than the upper limit, the silicone particles can more effectively function as a spacer.

The silicone particles are preferably used to obtain an adhesive. The silicone particles are preferably used in an adhesive for bonding two members. The silicone particles are preferably used as a spacer. The silicone particles are preferably used as a spacer in the adhesive. Examples of the use of the silicone particles include a spacer for gap control and a spacer for stress relaxation. The spacer for gap control can be used for gap control of stacked chips to ensure stand-off height and flatness, and for gap control of optical components to ensure smoothness of glass surfaces and thickness of adhesive layers. The spacer for stress relaxation can be used for stress relaxation of sensor chips, stress relaxation of adhesive structures such as pressure sensors, and stress relaxation of adhesive layers bonding two adherends. The silicone particles can be used for pressure sensors, die bonding materials, conductive adhesives, optical bonding materials, and the like. The silicone particles are preferably used to obtain an adhesive for optical bonding. The silicone particles are preferably used as spacers for optical bonding materials. The silicone particles are preferably used as particles for optical bonding.

Figure 1 is a cross-sectional view showing silicone particles in a resin composition according to a first embodiment of the present invention.

The silicone particle 1 shown in FIG. 1 comprises a silicone particle body 2 and a plurality of inorganic oxide particles 3. In the silicone particle 1, at least a portion of the plurality of inorganic oxide particles 3 is present inside the silicone particle body 2. In the silicone particle 1, a portion of the plurality of inorganic oxide particles 3 is present outside the silicone particle body 2. In the silicone particle, all of the plurality of inorganic oxide particles may be present inside the silicone particle body. The inorganic oxide particles may be in contact with other inorganic oxide particles or may overlap with other inorganic oxide particles.

Figure 2 is a cross-sectional view showing silicone particles in a resin composition according to a second embodiment of the present invention.

2 includes a silicone particle body 2, a plurality of inorganic oxide particles 3, and a coated particle 4 disposed on the surface of the silicone particle 1A. In the silicone particle 1A, at least a portion of the inorganic oxide particles 3 is present inside the silicone particle body 2. In the silicone particle 1A, a portion of the inorganic oxide particles 3 is present outside the silicone particle body 2. In the silicone particle, all of the inorganic oxide particles may be present inside the silicone particle body. The inorganic oxide particles may be in contact with other inorganic oxide particles or may overlap with other inorganic oxide particles. The coated particles 4 are in contact with the surface of the silicone particle body 2 and cover the surface of the silicone particle body 2. The surface of the silicone particle body 2 is coated with the coated particles 4. The coated particles may completely cover the surface of the silicone particle body or may not completely cover the surface of the silicone particle body. The silicone particle body may have a portion that is not covered by the coated particles. The coated particles may be in contact with other coated particles or may overlap with other coated particles. In the silicone particle, a plurality of the coated particles may overlap to form a layered structure.

Figure 3 is a cross-sectional view showing silicone particles in a resin composition according to a third embodiment of the present invention.

The silicone particle 1B shown in FIG. 3 comprises a silicone particle body 2, a plurality of inorganic oxide particles 3, and a coating layer 5 arranged on the surface of the silicone particle 1B. In the silicone particle 1B, at least a portion of the plurality of inorganic oxide particles 3 is present inside the silicone particle body 2. In the silicone particle 1B, a portion of the plurality of inorganic oxide particles 3 is present outside the silicone particle body 2. In the silicone particle, all of the plurality of inorganic oxide particles may be present inside the silicone particle body. The inorganic oxide particles may be in contact with other inorganic oxide particles or may overlap with other inorganic oxide particles. The coating layer 5 is in contact with the surface of the silicone particle body 2 and covers the surface of the silicone particle body 2. The surface of the silicone particle body 2 is coated with the coating layer 5. The coating layer may completely cover the surface of the silicone particle body, or may not completely cover the surface of the silicone particle body. The silicone particle body may have a portion that is not covered by the coating layer. The coating layer may have a single layer structure or a laminated structure of two or more layers. If the coating layer has a laminated structure of two or more layers, the materials of each layer may be the same or different.

The silicone particles preferably include a silicone particle body and a plurality of inorganic oxide particles. The silicone particles preferably include a composite particle including a silicone particle body and a plurality of inorganic oxide particles.

Other details of the silicone particles are described below. In this specification, "(meth)acrylate" means either or both of "acrylate" and "methacrylate", and "(meth)acrylic" means either or both of "acrylic" and "methacrylic".

(Silicone particle body)
The material of the silicone particle body is a silicone resin. The silicone particle body includes a silicone resin.

The silicone particle body preferably does not contain a platinum catalyst or contains 100 ppm or less of platinum catalyst. When a platinum catalyst is used, the lower the platinum catalyst content, the better. If the platinum catalyst content is high, reliability tends to decrease. The platinum catalyst content is more preferably 80 ppm or less, even more preferably 60 ppm or less, even more preferably 50 ppm or less, even more preferably 40 ppm or less, particularly preferably 30 ppm or less, and particularly preferably 20 ppm or less, and most preferably 10 ppm or less.

In general, silicone particle bodies are often obtained by polymerizing monomers using a platinum catalyst. In such silicone particle bodies, even if they are washed, the platinum catalyst is contained inside, and the platinum catalyst content exceeds 100 ppm. In contrast, silicone particle bodies obtained without using a platinum catalyst generally do not contain a platinum catalyst.

The material of the silicone particle body is preferably an organopolysiloxane, more preferably a silane alkoxide. Only one type of organopolysiloxane and one type of silane alkoxide may be used, or two or more types may be used in combination.

From the viewpoint of improving visibility even further, the silane alkoxide preferably contains silane alkoxide A represented by the following formula (1A) or silane alkoxide B represented by the following formula (1B). The silane alkoxide may contain silane alkoxide A represented by the following formula (1A) or silane alkoxide B represented by the following formula (1B).

Si(R1) _n (OR2) _4-n ... (1A)

In the above formula (1A), R1 represents a hydrogen atom, a phenyl group, or an alkyl group having 1 to 30 carbon atoms, R2 represents an alkyl group having 1 to 6 carbon atoms, and n represents an integer from 0 to 2. When n is 2, multiple R1s may be the same or different. Multiple R2s may be the same or different.

When R1 in the above formula (1A) is an alkyl group having 1 to 30 carbon atoms, specific examples of R1 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an isobutyl group, an n-hexyl group, a cyclohexyl group, an n-octyl group, and an n-decyl group. The number of carbon atoms in this alkyl group is preferably 10 or less, and more preferably 6 or less. The alkyl group includes a cycloalkyl group.

Specific examples of R2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group.

Specific examples of the silane alkoxide A include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, isopropyltrimethoxysilane, isobutyltrimethoxysilane, cyclohexyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, and diphenyldimethoxysilane. Silane alkoxides other than these may also be used.

Si(R1) _n (OR2) _4-n ... (1B)

In the above formula (1B), R1 represents a hydrogen atom, a phenyl group, an alkyl group having 1 to 30 carbon atoms, or an organic group having 1 to 30 carbon atoms and a polymerizable double bond, R2 represents an alkyl group having 1 to 6 carbon atoms, and n represents an integer from 0 to 2. When n is 2, multiple R1s may be the same or different. Multiple R2s may be the same or different. However, at least one R1 is an organic group having 1 to 30 carbon atoms and a polymerizable double bond. At least one R1 is preferably a vinyl group, a styryl group, or a (meth)acryloxy group, more preferably a vinyl group or a (meth)acryloxy group, and even more preferably a (meth)acryloxy group.

When R1 in the above formula (1B) is an alkyl group having 1 to 30 carbon atoms, specific examples of R1 include a methyl group, an ethyl group, a propyl group, an isopropyl group, an isobutyl group, an n-hexyl group, a cyclohexyl group, an n-octyl group, and an n-decyl group. The number of carbon atoms in this alkyl group is preferably 10 or less, and more preferably 6 or less. The alkyl group includes a cycloalkyl group.

The polymerizable double bond may be a carbon-carbon double bond. When R1 is an organic group having 1 to 30 carbon atoms and a polymerizable double bond, specific examples of R1 include a vinyl group, a styryl group, an allyl group, an isopropenyl group, and a 3-(meth)acryloxyalkyl group. Examples of the styryl group include a p-styryl group, an o-styryl group, and an m-styryl group. Examples of the (meth)acryloxyalkyl group include a (meth)acryloxymethyl group, a (meth)acryloxyethyl group, and a (meth)acryloxypropyl group. The number of carbon atoms in the organic group having 1 to 30 carbon atoms and a polymerizable double bond is preferably 2 or more, preferably 30 or less, and more preferably 10 or less. The term "(meth)acryloxy" refers to acryloxy and methacryloxy.

Specific examples of R2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group.

From the viewpoint of improving visibility and controlling the gap with high precision, it is preferable that the silane alkoxide contains a dialkoxysilane.

In the above-mentioned hydrolysis condensation product of silane alkoxide, it is preferable that, in 100% by weight of silane alkoxide, monoalkoxysilane is 0% by weight (unused) to 20% by weight, dialkoxysilane is 70% by weight to 99.9% by weight, and the total of trialkoxysilane and tetraalkoxysilane is 0.1% by weight to 30% by weight. In the above-mentioned hydrolysis condensation product of silane alkoxide, it is preferable that, in 100% by weight of silane alkoxide, monoalkoxysilane is 0% by weight (unused) to 15% by weight, dialkoxysilane is 75% by weight to 99% by weight, and the total of trialkoxysilane and tetraalkoxysilane is 1% by weight to 25% by weight. When the above-mentioned hydrolysis condensation product of silane alkoxide satisfies the above-mentioned preferred aspects, it is possible to obtain a gap material that can further improve visibility and control the gap with high precision.

From the viewpoint of adjusting the particle size more easily, it is preferable that the silane alkoxide contains a silane alkoxide having a polymerizable functional group, and it is more preferable that the silane alkoxide contains a silane alkoxide having a polymerizable double bond. Examples of silane alkoxides having a polymerizable double bond include vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, dimethoxyethylvinylsilane, diethoxymethylvinylsilane, diethoxyethylvinylsilane, ethylmethyldivinylsilane, methylvinyldimethoxysilane, ethylvinyldimethoxysilane, methylvinyldiethoxysilane, ethylvinyldiethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane. Cyclic siloxanes and modified (reactive) silicone oils may also be used. Examples of cyclic siloxanes include decamethylcyclopentasiloxane, etc. Examples of modified silicone oils include one-end modified silicone oil, both-end silicone oil, and side-chain silicone oil, etc.

Specific methods for producing the silicone particle body include condensing the silane alkoxide to obtain an oligomer in advance, and then carrying out a polymerization reaction by a suspension polymerization method, a dispersion polymerization method, a mini-emulsion polymerization method, an emulsion polymerization method, or the like to produce silicone particles.

In 100% by weight of the silicone particles, the content of the silicone particle body is preferably 70% by weight or more, more preferably 85% by weight or more, and even more preferably 93% by weight or more, and is preferably 99.9% by weight or less, more preferably 99% by weight or less, and even more preferably 97% by weight or less.

(Inorganic oxide particles)
Examples of materials for the inorganic oxide particles include silica, silicone resin, fluororesin, alumina, barium titanate, zirconia, silicate glass, borosilicate glass, lead glass, soda-lime glass, and alumina silicate glass.

The material of the inorganic oxide particles preferably contains silica, silicone resin, or fluororesin, more preferably contains silica or silicone resin, even more preferably contains silica, and is particularly preferably silica. When the material of the inorganic oxide particles satisfies the above-mentioned preferred aspects, visibility can be further improved and the gap can be controlled with high precision.

When the silicone particles include the inorganic oxide particles, the particle diameter of the inorganic oxide particles means the diameter when the inorganic oxide particles are spherical, and when the inorganic oxide particles are other than spherical, it is preferable to mean the diameter when the inorganic oxide particles are assumed to be spherical with a volume equivalent to the inorganic oxide particles. The particle diameter of the inorganic oxide particles is preferably an average particle diameter, and more preferably a number average particle diameter. The particle diameter of the inorganic oxide particles is obtained by observing 50 arbitrary inorganic oxide particles with an electron microscope or optical microscope and calculating the average value, or by performing laser diffraction particle size distribution measurement. In the observation with an electron microscope or optical microscope, the particle diameter of each inorganic oxide particle is obtained as the particle diameter of a circle equivalent diameter. In the observation with an electron microscope or optical microscope, the average particle diameter of 50 arbitrary inorganic oxide particles with a circle equivalent diameter is almost equal to the average particle diameter of the sphere equivalent diameter. In the laser diffraction particle size distribution measurement, the particle diameter of each inorganic oxide particle is obtained as the particle diameter of a sphere equivalent diameter. The particle diameter of the inorganic oxide particles is preferably calculated by laser diffraction particle size distribution measurement.

In the silicone particles, the ratio of the particle diameter of the inorganic oxide particles to the particle diameter of the silicone particles (particle diameter of inorganic oxide particles/particle diameter of silicone particles) is preferably 0.0003 or more, more preferably 0.001 or more, and preferably 0.02 or less, more preferably 0.01 or less. When the ratio (particle diameter of inorganic oxide particles/particle diameter of silicone particles) is equal to or greater than the lower limit and equal to or less than the upper limit, visibility can be further improved. In addition, when the silicone particles are used as a gap material, the gap can be controlled with high precision.

The refractive index (P1) of the inorganic oxide particles is not particularly limited. If the absolute value of the difference between the refractive index (P1) of the inorganic oxide particles and the refractive index (P3) of the cured product obtained by curing the curable component at 23°C for 5 hours is large, the cured product of the resin composition may appear cloudy due to the small particle size of the inorganic oxide particles. From the viewpoint of further improving visibility (particularly, suppressing the cured product of the resin composition from appearing cloudy), the absolute value of the difference between the refractive index (P1) and the refractive index (P3) is preferably 0.1 or less, more preferably 0.015 or less, and even more preferably 0.

The refractive index of the inorganic oxide particles can be measured according to JIS K 7142:2014 Plastics - Determination of refractive index, Method B.

In the silicone particles, the particle diameter of the inorganic oxide particles is preferably 10 nm or more, more preferably more than 20 nm, even more preferably 30 nm or more, particularly preferably 50 nm or more, and is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, particularly preferably 120 nm or less. When the particle diameter of the inorganic oxide particles is equal to or greater than the lower limit (or exceeds the lower limit) and equal to or less than the upper limit, the visibility can be further improved (particularly, the silicone particles can be prevented from becoming apparent). In addition, when the silicone particles are used as a gap material, the gap can be controlled with high precision.

The method for disposing the inorganic oxide particles inside the silicone particle body is not particularly limited. Examples of the method for disposing the inorganic oxide particles include a method for introducing graft chains by chemical bonding, a mechanochemical method for immobilizing the inorganic oxide particles on the surface by applying mechanical energy, and a hetero-coagulation method using a surface potential difference. From the viewpoint of more easily disposing the inorganic oxide particles inside the silicone particle body, the method for disposing the inorganic oxide particles is preferably a hetero-coagulation method using a surface potential difference.

From the viewpoint of improving visibility even further, the content of the inorganic oxide particles in 100% by weight of the silicone particles is preferably 0.1% by weight or more, more preferably 1% by weight or more, even more preferably 3% by weight or more, and is preferably 30% by weight or less, more preferably 15% by weight or less, even more preferably 9% by weight or less, and particularly preferably 7% by weight or less.

(Coating Material)
As in the silicone particles shown in FIG. 2 or FIG. 3, the silicone particles may have a coating material on the surface of the silicone particles. The coating material may be a coated particle or a coating layer. From the viewpoint of improving the dispersibility of the silicone particles, it is preferable that the surface of the silicone particles is coated with a coating material. The coating material is present outside the silicone particle body. The coating material may not be present inside the silicone particle body. The coating material may not be a metal oxide particle. The coating material may completely cover the surface of the silicone particle body, or may not completely cover the surface of the silicone particle body. The silicone particle body may have a portion that is not covered by the coating material. From the viewpoint of improving the dispersibility of the silicone particles, it is preferable that the coating material completely covers the surface of the silicone particle body. For this reason, the coating material is preferably a coating layer. The coated particles may be in contact with other coated particles or may overlap with other coated particles. In the silicone particles, a plurality of the coated particles may overlap to form a laminate structure. The coating layer may have a single layer structure or a laminate structure of two or more layers. When the coating layer has a laminated structure of two or more layers, the materials of the layers may be the same or different.

The material of the coating substance is not particularly limited. The material of the coating substance may be an organic material or an inorganic material.

The organic materials include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamideimide, polyether ether ketone, polyether sulfone, and divinylbenzene polymer. The divinylbenzene polymer may be a divinylbenzene copolymer. The divinylbenzene copolymer includes a divinylbenzene-styrene copolymer and a divinylbenzene-(meth)acrylic acid ester copolymer. Since the above-mentioned coating substance can be easily prepared, it is preferable that the material of the above-mentioned coating substance is a polymer obtained by polymerizing one or more polymerizable monomers having an ethylenically unsaturated group.

When the above-mentioned coating substance is obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the above-mentioned polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer.

Examples of the non-crosslinkable monomers include vinyl compounds such as styrene monomers, α-methylstyrene, and chlorostyrene; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; acid vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; halogen-containing monomers such as vinyl chloride and vinyl fluoride; (meth)acrylic compounds such as alkyl (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, glycerol ( (meth)acrylate, polyoxyethylene (meth)acrylate, glycidyl (meth)acrylate, and other oxygen atom-containing (meth)acrylate compounds; (meth)acrylonitrile and other nitrile-containing monomers; trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, (perfluorobutyl)ethyl (meth)acrylate, perfluorobutyl-hydroxypropyl (meth)acrylate, (perfluorohexyl)ethyl (meth)acrylate, octafluoropentyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and other halogen-containing (meth)acrylate compounds; α-olefin compounds such as diisobutylene, isobutylene, linearene, ethylene, and propylene; and conjugated diene compounds such as isoprene and butadiene.

The crosslinkable monomers include vinyl compounds such as vinyl monomers like divinylbenzene, 1,4-divinyloxybutane, and divinylsulfone; (meth)acrylic compounds such as tetramethylolmethane tetra(meth)acrylate, polytetramethylene glycol diacrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate. Polyfunctional (meth)acrylate compounds such as polytetramethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate; allyl compounds such as triallyl (iso)cyanurate, triallyl trimellitate, diallyl phthalate, diallyl acrylamide, and diallyl ether; silane compounds such as tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, isopropyltrimethoxysilane, isobutyltrimethoxysilane, cyclohexylsilane, methyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, isopropyltrimethoxysilane, isobutyltrimethoxysilane, and cyclohexylsilane; silane alkoxide compounds such as n-alkyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, trimethoxysilylstyrene, γ-(meth)acryloxypropyltrimethoxysilane, 1,3-divinyltetramethyldisiloxane, methylphenyldimethoxysilane, and diphenyldimethoxysilane; vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, dimethoxyethylvinylsilane, diethoxymethylvinylsilane, diethoxyethylvinylsilane, ethylmethyldivinylsilane, methylvinyldimethoxysilane, and the like; Examples include silane alkoxides containing polymerizable double bonds such as silane, ethylvinyldimethoxysilane, methylvinyldiethoxysilane, ethylvinyldiethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane; cyclic siloxanes such as decamethylcyclopentasiloxane; modified (reactive) silicone oils such as one-end modified silicone oil, both-end silicone oil, and side-chain silicone oil; and carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride.

The coating material can be obtained by polymerizing the polymerizable monomer having the ethylenically unsaturated group. The polymerization method is not particularly limited, and examples thereof include known methods such as radical polymerization, ionic polymerization, polycondensation (condensation polymerization, polycondensation), addition condensation, living polymerization, and living radical polymerization. Another polymerization method is suspension polymerization in the presence of a radical polymerization initiator.

The above inorganic materials include silica, alumina, barium titanate, zirconia, carbon black, silicate glass, borosilicate glass, lead glass, soda-lime glass, and alumina silicate glass.

The material of the coating substance preferably contains silica, silicone resin, or fluororesin, and more preferably contains silica or silicone resin. When the material of the coating substance satisfies the above-mentioned preferred aspects, visibility can be further improved. In addition, when the silicone particles are used as a gap material, the gap can be controlled with high precision.

The material of the coating substance may be the same as the material of the inorganic oxide particles, or may be different. Since the coating substance can be easily prepared, it is preferable that the material of the coating substance is the same as the material of the inorganic oxide particles.

From the viewpoint of improving visibility even further, the refractive index of the coating material is preferably 1.39 or more, more preferably 1.395 or more, and is preferably 1.42 or less, more preferably 1.415 or less.

The refractive index of the above coating material can be measured using a method similar to JIS K 7142:2014 Plastics - Determination of refractive index, Method B.

The absolute value of the difference between the refractive index of the silicone particles and the refractive index of the coating material is preferably 0.025 or less, more preferably 0.020 or less. There is no particular limit on the lower limit of the absolute value of the difference between the refractive index of the silicone particles and the refractive index of the coating material. The absolute value of the difference between the refractive index of the silicone particles and the refractive index of the coating material may be 0 or more. When the absolute value of the difference between the refractive index of the silicone particles and the refractive index of the coating material is equal to or greater than the lower limit and equal to or less than the upper limit, visibility can be further improved.

As a method for controlling the absolute value of the difference between the refractive index of the silicone particles and the refractive index of the coating material within the above-mentioned preferred range, a method of using a silane compound having a radical polymerizable functional group containing a fluorine atom in the side chain as the material of the coating material can be given.

The area of the portion where the coating material is present (coverage rate) of the total surface area of the silicone particles (100%) is preferably 80% or more, more preferably 85% or more. There is no particular upper limit to the coverage rate. The coverage rate may be 99% or less. When the coverage rate is equal to or greater than the lower limit, visibility can be further improved. In addition, when the silicone particles are used as a gap material, the gap can be controlled with even greater precision.

The area of the portion where the coating material is present (coverage rate) out of the total surface area of the silicone particle (100%) is determined by observing the silicone particle with an electron microscope or optical microscope and calculating the percentage of the surface area of the portion where the coating material is present relative to the projected area of the silicone particle.

In the silicone particles, the thickness of the coating material (particle diameter of the coated particles or thickness of the coating layer) is preferably 30 nm or more, more preferably more than 60 nm, even more preferably 80 nm or more, and particularly preferably 100 nm or more. In the silicone particles, the thickness of the coating material is preferably 500 nm or less, more preferably 200 nm or less. When the thickness of the coating material is equal to or greater than the lower limit (or exceeds the lower limit) and equal to or less than the upper limit, visibility can be further improved. In addition, when the silicone particles are used as a gap material, the gap can be controlled with high precision.

When the silicone particles are provided with the coated particles, the particle diameter of the coated particles is the thickness of the coating material. When the silicone particles are provided with the coated particles, the particle diameter of the coated particles means the diameter when the coated particles are spherical, and when the coated particles are other than spherical, it is preferable to mean the diameter when the coated particles are assumed to be spherical with a volume equivalent thereto. The particle diameter of the coated particles is preferably the average particle diameter, and more preferably the number average particle diameter. The particle diameter of the coated particles is obtained by observing 50 random coated particles on the cross section of the silicone particles with an electron microscope or optical microscope, calculating the average value, or by performing laser diffraction particle size distribution measurement. In the observation with an electron microscope or optical microscope, the particle diameter of each coated particle is obtained as the particle diameter of the circle equivalent diameter. In the observation with an electron microscope or optical microscope, the average particle diameter of the circle equivalent diameter of the random 50 coated particles is almost equal to the average particle diameter of the sphere equivalent diameter. In the laser diffraction particle size distribution measurement, the particle diameter of each coated particle is obtained as the particle diameter of the sphere equivalent diameter. The particle size of the coated particles is preferably calculated by laser diffraction particle size distribution measurement.

When the silicone particles have the coating layer, the thickness of the coating layer can be measured by observing the cross section of the silicone particle, for example, using a transmission electron microscope (TEM). It is preferable to calculate the thickness of the coating layer by averaging the thickness of any five coating layers as the thickness of the coating layer of one silicone particle, and it is more preferable to calculate the average thickness of the entire coating layer as the thickness of the coating layer of one silicone particle. In the case of multiple silicone particles, it is preferable to calculate the thickness of the coating layer by averaging the thickness of any 10 silicone particles.

In the silicone particles, the ratio of the thickness of the coating material to the particle diameter of the silicone particles (thickness of coating material/particle diameter of silicone particles) is preferably 0.0003 or more, more preferably 0.001 or more, and preferably 0.02 or less, more preferably 0.01 or less. When the ratio (thickness of coating material/particle diameter of silicone particles) is equal to or greater than the lower limit and equal to or less than the upper limit, visibility can be further improved. Furthermore, when the silicone particles are used as a gap material, the gap can be controlled with high precision.

The method of disposing the coating substance on the surface of the silicone particles is not particularly limited. Examples of methods for disposing the coating substance include a method of introducing graft chains by chemical bonding, a mechanochemical method of immobilizing the coating substance on the surface by applying mechanical energy, a heterocoagulation method using a potential difference on the surface, and a coating substance surface localization method using phase separation between the coating substance and silicone. From the viewpoint of more easily disposing the coating substance on the surface of the silicone particles, the method of disposing the coating substance is preferably a coating substance surface localization method using phase separation between the coating substance and silicone.

(Curing component)
The resin composition according to the present invention contains silicone particles and a curable component.

In general, examples of the curable component include a thermosetting component, a photocurable component, and a room temperature curable component. When a thermosetting component or a photocurable component is used as the curable component, residual stress may occur in the cured product of the resin composition (cured product of the curable component). Residual stress in the cured product of the resin composition (cured product of the curable component) may affect reliability, so it is necessary to reduce the residual stress as much as possible. One method for reducing residual stress in the cured product of the resin composition (cured product of the curable component) is to use a room temperature curable component as the curable component. Room temperature is, for example, 25°C.

In the resin composition according to the present invention, the curable component contains a silicone resin, which makes it possible to further improve visibility, more effectively suppress the occurrence of residual stress, and more effectively increase heat resistance.

In the resin composition, the curable component includes a silicone resin. The silicone resin preferably has fluidity at 25°C. The silicone resin preferably has a paste-like form at 25°C. The paste-like form includes a liquid form.

The silicone resin may be an organopolysiloxane compound. The organopolysiloxane compound may have a hydroxyl group at the end or a vinyl group at the end. The silicone resin may be polypropylene oxide having a methyldimethoxysilyl group. As described above, from the viewpoint of reducing residual stress in the cured product of the resin composition (cured product of the curable component), the silicone resin is preferably a room temperature curable resin, and is preferably a resin that can be cured at 23°C.

The silicone resin material may be the silicone base material described above. The silicone resin can be obtained by polymerizing the silicone base material using a known method. For example, a method of forming a siloxane bond by polymerization using a silane compound can be mentioned.

The silicone resin may be an organopolysiloxane or a polyorganosilsesquioxane. From the viewpoint of improving visibility, more effectively suppressing the generation of residual stress, and more effectively increasing heat resistance, it is preferable that the silicone resin is an organopolysiloxane.

The curable component may contain a curable component other than the silicone resin. Examples of the curable component other than the silicone resin include acrylic resin.

The acrylic resin may be a polymer of a (meth)acrylic compound. When the acrylic resin is obtained by polymerizing a (meth)acrylic compound, the (meth)acrylic compound may be the non-crosslinkable (meth)acrylic compound described above, or the crosslinkable (meth)acrylic compound described above. The acrylic resin is preferably a room temperature curable resin.

The acrylic resin can be obtained by polymerizing the (meth)acrylic compound by a known method. For example, this method includes a method of suspension polymerization in the presence of a radical polymerization initiator.

Examples of the acrylic resin include polymethyl methacrylate and polymethyl acrylate. From the viewpoints of improving visibility, suppressing the occurrence of residual stress more effectively, and improving heat resistance more effectively, it is preferable that the acrylic resin be polymethyl methacrylate.

The refractive index (P3) of the cured product obtained by curing the curable component at 23°C for 5 hours is preferably 1.20 or more, more preferably 1.30 or more, even more preferably 1.38 or more, even more preferably 1.39 or more, particularly preferably 1.40 or more, and most preferably 1.41 or more. The refractive index (P3) of the cured product obtained by curing the curable component at 23°C for 5 hours is preferably 1.60 or less, more preferably 1.50 or less, even more preferably 1.45 or less, even more preferably 1.44 or less, particularly preferably 1.43 or less, and most preferably 1.42 or less. If the refractive index (P3) of the cured product obtained by curing the curable component at 23°C for 5 hours is equal to or greater than the lower limit and equal to or less than the upper limit, the refractive index approaches that of a member (e.g., a transparent protective material) used as a display device, and visibility can be further improved (especially the occurrence of double images can be suppressed).

The refractive index of the cured product can be measured as follows:

The above curable components are cured at 23°C for 5 hours to obtain a cured product with a thickness of 0.1 mm. The refractive index of the resulting cured product is measured using an Abbe refractometer (ERMA's "ER-7MW") or similar.

The transmittance at a wavelength of 650 nm of the cured product obtained by curing the curable component at 23° C. for 5 hours is preferably 92% or more, more preferably 94% or more, and even more preferably 95% or more. The upper limit of the transmittance at a wavelength of 650 nm of the cured product obtained by curing the curable component at 23° C. for 5 hours is not particularly limited. The transmittance at a wavelength of 650 nm of the cured product obtained by curing the curable component at 23° C. for 5 hours may be 99.9% or less. When the transmittance at a wavelength of 650 nm of the cured product obtained by curing the curable component at 23° C. for 5 hours is equal to or greater than the lower limit, visibility can be further improved.

The transmittance at a wavelength of 650 nm of the cured product obtained by curing the curable component at 23°C for 5 hours can be measured as follows.

The curable component is cured at 23°C for 5 hours to obtain a cured product having a thickness of 0.1 mm. The obtained cured product is used to measure the transmittance at a wavelength of 650 nm at 23°C. The transmittance can be measured, for example, using a spectrophotometer (double beam spectrophotometer (U-2910 manufactured by Hitachi High-Tech Science Corporation)). An integrating sphere can be used as the detector.

In 100% by weight of the resin composition, the content of the curable component is preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, particularly preferably 70% by weight or more, and is preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the curable component is equal to or more than the lower limit and equal to or less than the upper limit, visibility can be further improved.

(Other details of the resin composition)
The resin composition according to the present invention can be suitably used as an adhesive for optical bonding.

In recent years, optical bonding has been increasingly used in various fields. For example, the use of optical bonding has been considered to improve visibility in display devices such as in-vehicle displays. Specifically, a method has been considered in which a material used for optical bonding (optical bonding material, for example, a translucent material such as an adhesive) is applied to an image display element, a transparent protective material is placed on the surface of the optical bonding material opposite the image display element, and the optical bonding material is cured. The cured optical bonding material forms an adhesive layer that bonds the image display element and the transparent protective material.

Optical bonding materials used in display devices (e.g., in-vehicle displays, etc.) can be difficult to apply uniformly onto an image display element. In addition, the viscosity of optical bonding materials is low, and before the optical bonding material is completely cured, the optical bonding material may flow on the image display element due to, for example, the weight of a transparent protective material, etc., and it may not be possible to ensure a sufficient thickness (gap) of the cured product (adhesive layer) of the optical bonding material on the image display element. For this reason, the use of a gap material as an optical bonding material is being considered. Coated silicone particles, etc. may be used as the gap material.

When conventional coated silicone particles, etc. are used as the gap material of the optical bonding material, it is difficult to sufficiently reduce the refractive index difference between the optical bonding material and the gap material because the particle diameter of the coated particles in the coated silicone particles is small (the thickness of the coating material is thin). In addition, when the particle diameter of the coated particles in the coated silicone particles is small, it becomes difficult to uniformly coat the surface of the silicone particles, and the refractive index difference between the optical bonding material and the gap material may vary. As a result, it may be difficult to sufficiently improve visibility with conventional coated silicone particles.

In addition, when a display device (e.g., an in-vehicle display, etc.) is repeatedly exposed to temperature changes from low to high, stress may occur between the components due to differences in the linear expansion coefficients of the components (e.g., image display elements, transparent protective materials, etc.). If the thickness (gap) of the cured product (adhesive layer) of the optical bonding material cannot be sufficiently secured, the stress generated between the components cannot be sufficiently alleviated, and cracks or peeling may occur in the cured product (adhesive layer) of the optical bonding material, etc. In order to alleviate the stress generated between the components, it is required to sufficiently secure the thickness (gap) of the cured product (adhesive layer) of the optical bonding material. By using the resin composition according to the present invention, the thickness (gap) of the adhesive layer can be controlled with high precision, and the thickness (gap) of the adhesive layer can be sufficiently secured.

The resin composition according to the present invention has the above-mentioned configuration, so even if the optical bonding adhesive contains a gap material (silicone particles), the silicone particles are prevented from becoming apparent in the cured product after the adhesive is cured, and the occurrence of double images is prevented, thereby improving visibility.

The resin composition according to the present invention can be suitably used as an adhesive, and more suitably used as an adhesive for optical bonding. The adhesive preferably has fluidity at 25°C. The adhesive preferably has a paste-like form at 25°C. The paste-like form includes a liquid form.

The adhesive may be a one-part type in which the base agent and the curing agent are premixed, or a two-part type in which the base agent and the curing agent are separate. The adhesive may be a condensation curing type or an addition curing type. The adhesive may be cured using a catalyst such as platinum, or may be cured by moisture or the like. From the viewpoint of more effectively reducing residual stress in the cured product of the adhesive, it is preferable that the adhesive be cured at room temperature.

The adhesive can, for example, bond two adherends. The adhesive is preferably used to form an adhesive layer that bonds the two adherends. Furthermore, the adhesive is preferably used to relieve stress in the adhesive layer.

The adhesive may or may not contain conductive particles. The adhesive may or may not be used for conductive connection. The adhesive may or may not be used for anisotropic conductive connection. The adhesive may or may not be used for anisotropic conductive connection. The adhesive may or may not be a conductive material. The adhesive may or may not be anisotropic conductive material. The adhesive may or may not be used for a liquid crystal display element. The adhesive is preferably an optical bonding adhesive. The adhesive is preferably used in a display device to fill a gap between an image display element and a transparent protective material, reduce reflection loss occurring at the interface of the transparent protective material, and improve visibility.

The resin composition may contain, in addition to the curable component and the silicone particles, vinyl resin, thermoplastic resin, curable resin, thermoplastic block copolymer, elastomer, solvent, etc. These components may be used alone or in combination of two or more.

Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of the curable resin include epoxy resin, urethane resin, polyimide resin, and unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, and hydrogenated styrene-isoprene-styrene block copolymer. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

Examples of the solvent include water and organic solvents. Organic solvents are preferred because they can be easily removed. Examples of the organic solvent include alcohol compounds such as ethanol, ketone compounds such as acetone, methyl ethyl ketone, and cyclohexanone, aromatic hydrocarbon compounds such as toluene, xylene, and tetramethylbenzene, glycol ether compounds such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, and tripropylene glycol monomethyl ether, ester compounds such as ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate, aliphatic hydrocarbon compounds such as octane and decane, and petroleum-based solvents such as petroleum ether and naphtha.

In addition to the curable component and the silicone particles, the resin composition may contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, lubricants, antistatic agents, and flame retardants.

(Display device)
The display device according to the present invention includes a first member, an image display element as a second member, and an adhesive layer bonding the first member and the second member. In the display device according to the present invention, the adhesive layer is a cured product of an adhesive containing the silicone particles and a curable component. The adhesive layer is preferably formed by a curing agent for the adhesive.

Figure 4 is a cross-sectional view showing an example of a display device using the resin composition according to the first embodiment of the present invention.

The display device 31 shown in FIG. 4 includes a first member 32, a second member 33 that is an image display element, and an adhesive layer 34 that bonds the first member 32 and the second member 33. The adhesive layer 34 is a cured product of a resin composition that contains silicone particles 1 and a curable component. Silicone particles 1A or silicone particles 1B may be used instead of silicone particles 1.

Silicone particles 1 are present between the first member 32 and the second member 33, and a constant distance (gap) is maintained between the first member 32 and the second member 33. The thickness of the adhesive layer 34 is kept constant by the silicone particles 1, and the thickness of the adhesive layer 34 is ensured.

The thickness of the adhesive layer is preferably 30 μm or more, more preferably 50 μm or more, and preferably 500 μm or less, more preferably 200 μm or less. When the thickness of the adhesive layer is equal to or greater than the lower limit and equal to or less than the upper limit, the stress generated between the components can be more effectively alleviated, and the occurrence of cracks in the adhesive layer and the occurrence of peeling of the adhesive layer can be more effectively prevented.

The manufacturing method of the display device is not particularly limited. One example of the manufacturing method of the display device is a method in which the resin composition is placed between the first member and the second member, a laminate is obtained, and then the resin composition is cured.

The first member is preferably a transparent protective material. Examples of materials for the transparent protective material include glass and plastic. The transparent protective material is preferably a light-transmitting material. The transparent protective material is preferably a material that protects the surface of the image display element.

Examples of the display device include liquid crystal display devices and in-vehicle displays.

The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

Example 1
Preparation of silicone particles:
A mixture of 30 parts by weight of silicone oil with acrylic ends ("X-22-2445" manufactured by Shin-Etsu Chemical Co., Ltd.) and 3.3 parts by weight of silicone oil modified with methacrylic ends ("KF-2012" manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared. 0.5 parts by weight of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (polymerization initiator, "Perocta O" manufactured by NOF Corp.) and 5 parts by weight of silica particles A ("QSG-100" manufactured by Shin-Etsu Chemical Co., Ltd., particle size 110 nm) were dispersed in this mixture to obtain a dispersion liquid A. In addition, 1.5 parts by weight of Florene DOPA-100 (dispersant) and 80 parts by weight of a 5% aqueous solution of polyvinyl alcohol (polymerization degree: about 2000, saponification degree: 86.5 mol% to 89 mol%, "GOHSENOL GH-20" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) were mixed with 150 parts by weight of ion-exchanged water to prepare an aqueous solution B. The dispersion A was placed in a separable flask placed in a warm bath, and then the aqueous solution B was added and stirred. After that, it was confirmed that the particle size had reached a predetermined value, and the temperature was raised to 90° C., and polymerization was carried out for 9 hours. The entire amount of particles after polymerization was washed with water by centrifugation, classified, and then freeze-dried to obtain silicone particles (1). The obtained silicone particles (1) had a particle size of 101 μm and a CV value of the particle size of 10%.

Preparation of resin composition (optical bonding adhesive):
To 98% by weight of a silicone adhesive ("LUMISIL 102" manufactured by Wacker Asahi Kasei Silicone Co., Ltd., curable component), 2% by weight of the silicone particles (1) was added, and the mixture was stirred with a planetary stirrer to uniformly disperse the silicone particles, thereby preparing a resin composition.

(Examples 2 to 7, 10 to 12 and Comparative Example 1)
Silicone particles and resin compositions were prepared in the same manner as in Example 1, except that the content of inorganic oxide particles, the refractive index (P2) of the silicone particles, and the particle diameter, CV value of the particle diameter, and refractive index (P2) of the silicone particles were changed as shown in Tables 1 to 3 below.

(Example 8)
Silicone particles (1) and, as coated particles, silica particles B ("QSG-100" manufactured by Shin-Etsu Chemical Co., Ltd., particle size 110 nm) were prepared. Dispersion liquid B was prepared by dispersing 0.2 parts by weight of the silica particles (B) in 4.0 parts by weight of methanol.

7.0 parts by weight of silicone particles (1) and 88.5 parts by weight of distilled water were placed in a 500 ml separable flask placed in a warm bath, and the above dispersion liquid B was gently added dropwise while irradiating with ultrasonic waves. The mixture was then stirred at room temperature for 6 hours, and the surfaces of the silicone particles (1) were coated with silica particles B. The entire amount of the particles after the treatment was washed with water by centrifugation to obtain silicone particles (8). A resin composition was prepared in the same manner as in Example 1, except that silicone particles (8) were used.

Example 9
Silicone particles (1) were prepared. 7 parts by weight of silicone particles (1), 85 parts by weight of distilled water, 7 parts by weight of methanol, and 0.2 parts by weight of 28% ammonia water were placed in a 500 ml separable flask placed in a warm bath, and the mixture was heated to 80° C. with stirring and reacted for 1 hour to promote hydrolysis of the silanol groups introduced on the surface to form a silica coating layer. The obtained particles were washed with water by centrifugation to obtain silicone particles (9). A resin composition was prepared in the same manner as in Example 1, except that silicone particles (9) were used.

(Example 13)
Silicone particles (13) were obtained in the same manner as in Example 1, except that silica particles A were not added when obtaining dispersion A. The obtained silicone particles (13) had a particle diameter of 102 μm and a CV value of the particle diameter of 20%. A resin composition was prepared in the same manner as in Example 1, except that silicone particles (13) were used.

(Comparative Example 2)
A resin composition was prepared in the same manner as in Example 1, except that glass beads (glass particles, AS ONE Corporation's "BZ-01") were used.

(evaluation)
(1) Particle diameter of silicone particles or glass particles (particles for optical bonding) For the obtained silicone particles and the glass particles used, the particle diameters of approximately 100,000 silicone particles or glass particles were measured using a particle size distribution measuring device ("Multisizer 4" manufactured by Beckman Coulter, Inc.), and the average value was calculated.

(2) Particle diameter of coated particles and thickness of coating layer When the obtained silicone particles had coated particles, the particle diameters of approximately 100,000 randomly selected coated particles on the cross section of the silicone particle were measured using an electron microscope or optical microscope, and the average value was calculated to determine the particle diameter of the coated particles.

When the obtained silicone particles have a coating layer, the thickness of the coating layer was measured by observing the cross section of the silicone particle using a transmission electron microscope (TEM) (JEM2100 manufactured by JEOL Ltd.). The thickness of the coating layer was calculated by averaging the thickness of the coating layer at any five locations as the thickness of the coating layer for one silicone particle, and then calculating the average value from the thicknesses of the coating layers of any ten silicone particles.

(3) Refractive index The refractive index (P1) of the inorganic oxide particles (silica particles), the obtained silicone particles, the glass particles used, and the curable component were measured by the above-mentioned method for the refractive index (P2) of the inorganic oxide particles, the refractive index (P3) of the cured product obtained by curing the curable component at 23° C. for 5 hours. From the obtained results, the absolute value of the difference between the refractive index (P2) of the silicone particles or glass particles and the refractive index (P3) of the cured product obtained by curing the curable component at 23° C. for 5 hours was calculated.

(4) Transmittance The obtained resin composition was cured at 23° C. for 5 hours by the method described above, and the transmittance of the cured product at a wavelength of 650 nm was measured.

(5) Coverage The area of the part where the coating material was present (coverage) was measured for the obtained silicone particles (particles for optical bonding) out of the total surface area of the silicone particles (100%). The coverage was measured as follows.

How to measure coverage:
Observation was carried out using an electron microscope, and the projected area S1 per each of the obtained silicone particles and the equivalent circular area S2 of the uncoated portion were calculated using image analysis software, and the coverage rate was determined using the following formula.

Coverage rate (%) = (S1-S2)/S1 x 100

(6) Visibility The obtained resin composition (optical bonding adhesive) was filled into a syringe, and the resin composition was applied to an image display element using a dispenser to a thickness of 120 μm to form an adhesive layer, and then a transparent protective material was laminated on the formed adhesive layer to obtain a laminate. The adhesive layer of the obtained laminate was cured under conditions of 23° C. and 5 hours to bond the image display element and the transparent protective material to obtain a display device.

The resulting display device was visually evaluated for the presence of silicone particles or glass particles in the adhesive layer. The presence or absence of double images was also visually confirmed. Based on both results, visibility was judged according to the following criteria.

[Presence of silicone particles or glass particles]
〇〇: No silicone or glass particles were found. 〇: Only a small amount of silicone or glass particles were found (at a level that does not cause problems in practical use).
×: Does not meet the criteria for ○○ and ○

[Criteria for determining the occurrence of double images]
○○: No double image is observed. ○: A very slight double image is observed (at a level that does not cause any problems in practical use).
×: Does not meet the criteria for ○○ and ○

[Visibility criteria]
〇〇〇: Neither silicone particles, glass particles, nor double images were found. 〇〇: Only a small amount of either silicone particles, glass particles, or double images was found (at a level that does not cause any problems in practical use).
◯: Both silicone particles or glass particles and double images are very slightly observed (at a level that does not cause problems in practical use)
×: Does not meet the criteria for ○○○, ○○, and ○

(7) Gap controllability Ten display devices were prepared from each of the display devices obtained in the above (6) Visibility evaluation. The thickness of the adhesive layer of each of the ten display devices was measured using a stereomicroscope (Nikon Corporation's "SMZ-10"), and the average thickness of the adhesive layer for each of the ten display devices was calculated. The gap controllability was evaluated according to the following criteria.

[Gap controllability criteria]
○○○: The average thickness of the adhesive layer is 112 μm or more and 121 μm or less. ○○: The average thickness of the adhesive layer is 108 μm or more and less than 112 μm, or more than 121 μm and 132 μm or less. ○: The average thickness of the adhesive layer is 96 μm or more and less than 108 μm, or more than 132 μm and 150 μm or less. ×: The average thickness of the adhesive layer is less than 96 μm or more than 150 μm.

Details of the silicone particles and glass particles, the composition of the resin composition, and the results are shown in Tables 1 to 3 below.

Reference Signs List 1, 1A, 1B... Silicone particle 2... Silicone particle body 3... Inorganic oxide particle 4... Coated particle 5... Coating layer 31... Display device 32... First member 33... Second member (image display element)
34...Adhesive layer

Claims (9)

Contains silicone particles and a curable component,
the curable component comprises a silicone resin,
a resin composition in which the absolute value of the difference between the refractive index of the silicone particles and the refractive index of a cured product obtained by curing the curable component under conditions of 23° C. and 5 hours is 0.02 or less. The resin composition according to claim 1, wherein the CV value of the particle diameter of the silicone particles is 21% or less. The silicone particle includes a silicone particle body and a plurality of inorganic oxide particles,
The resin composition according to claim 1 , wherein at least a portion of the inorganic oxide particles are present inside the silicone particle body. The resin composition according to claim 3, wherein the inorganic oxide particle material contains silica. The resin composition according to claim 3 or 4, wherein the content of the inorganic oxide particles is 0.1% by weight or more and 9% by weight or less in 100% by weight of the silicone particles. The resin composition according to any one of claims 1 to 5, wherein the transmittance of the cured product obtained by curing the resin composition at 23°C for 5 hours is 92% or more at a wavelength of 650 nm. The resin composition according to any one of claims 1 to 6, which is an adhesive for optical bonding. A first member;
an image display element as a second member;
an adhesive layer that bonds the first member and the second member;
A display device, wherein the adhesive layer is a cured product of the resin composition according to any one of claims 1 to 7. The display device according to claim 8, wherein the first member is a transparent protective material.

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