JP6666181B2 - Adhesive composition, adhesive member and method for producing the same, adhesive sheet and method for producing the same, and electronic equipment including the adhesive member - Google Patents

Description

  The present invention relates to an adhesive composition, an adhesive member and a method for producing the same, an adhesive sheet and a method for producing the same, and an electronic device including the adhesive member.

  In recent years, various electronic devices have been used, and the performance of the electronic devices has been improved. With the high performance of electronic devices, the frequency of electronic devices used in electronic circuits of electronic devices has been increasing, and the components and members of electronic devices used in the high frequency region have proper dielectric constants and Low dielectric loss characteristics are required. The same applies to polymer materials used in electronic devices, and polymer materials with controlled dielectric constant are being developed.

  In particular, portable communication electronic devices such as smartphones, which have been rapidly used in recent years, are being assembled and used as devices by bonding various electronic members using an adhesive tape, an adhesive, or the like. For example, in a smartphone, a transparent adhesive tape is used for joining a touch panel and a display, and a transparent adhesive tape having a low dielectric constant is required to avoid malfunction of the smartphone.

  In order to lower the dielectric constant of the pressure-sensitive adhesive tape, it is preferable to lower the dielectric constant of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape, by changing the molecular structure of the polymer constituting the pressure-sensitive adhesive conventionally, Control of the dielectric constant of an adhesive has been performed (for example, Patent Documents 1, 2, and 3).

  As a method of lowering the dielectric constant of the pressure-sensitive adhesive, addition of hollow silica to the pressure-sensitive adhesive is also considered as one means. On the other hand, if hollow silica is added to the pressure-sensitive adhesive, the light transmittance of the pressure-sensitive adhesive is reduced and the transparency is lost, so that the pressure-sensitive adhesive cannot be used for bonding optical electronic members such as a touch panel of a smartphone and a display.

  Conventionally, various additions of hollow particles to an adhesive have been proposed (for example, Patent Documents 4 and 5), but there is no example of using hollow particles to reduce the dielectric constant of the adhesive. Also, a transparent pressure-sensitive adhesive to which hollow particles are added has not been proposed.

  For example, in Patent Document 4, fine hollow particles are blended in the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape, and both impact resistance and waterproofness of the pressure-sensitive adhesive tape are compatible, and polyacrylonitrile hollow particles having an average particle diameter of 20 to 40 μm Although black pigment adhesion treatment is performed to ensure light-curing performance while being black, the pressure-sensitive adhesive layer has no transparency.

  In Patent Document 5, the shear strength is improved by including hollow particles in a viscoelastic layer supporting the pressure-sensitive adhesive layer, and the peel strength of the pressure-sensitive adhesive sheet is improved. The hollow particles used are hollow glass. Balloons, hollow alumina balloons, hollow ceramic balloons and the like, and hollow particles having a relatively large average particle diameter of 1 μm to 500 μm are used. Such hollow particles have light scattering properties and are used as adhesives. No transparency.

  Prior art documents related to the present invention include Patent Documents 6 to 11 and Non-Patent Documents 1 and 2.

JP-A-2005-20947 JP 2015-189939 A JP 2015-129211 A JP-A-2015-180720 JP 2015-54954 A Japanese Patent No. 4046921 (Japanese Patent Application Laid-Open No. 2001-233611) Japanese Patent No. 4654428 (Japanese Patent Application Laid-Open No. 2005-263550) Japanese Patent No. 4861634 (Japanese Patent Application Laid-Open No. 2006-256921) Japanese Patent No. 4853662 (Japanese Patent Application Laid-Open No. 2008-247664) Japanese Patent No. 5194935 (Japanese Patent Application Laid-Open No. 2009-234848) Japanese Patent No. 4135072 (Japanese Patent Application Laid-Open No. 2004-115594)

Masamitsu Fuji, Nagoya Institute of Technology Advanced Ceramics Research Center Annual Report, 2, 25 (2013) Hideki Sakai et al., Material Technology, 30, 147 (2012)

  As described above, there is an example in which hollow particles are included in an adhesive, but an adhesive having a low dielectric constant and transparency has not yet been realized.

  The present invention has been made in view of the above circumstances, and provides a pressure-sensitive adhesive having a low dielectric constant and transparency.

  The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing hollow particles and a polymerizable compound, wherein the average particle diameter of the primary particles of the hollow particles is 30 nm or more and 500 nm or less, and the hollow particles Is 20% by volume or more and 95% by volume or less, the number average molecular weight of the polymerizable compound is 10,000 or less, and the content of the hollow particles is less than the hollow particles. The amount is 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the solid component.

  Further, the adhesive member of the present invention is an adhesive member containing hollow particles and a resin, wherein the average particle diameter of the primary particles of the hollow particles is 30 nm or more and 500 nm or less, and the voids of the hollow particles Ratio is 20% by volume or more and 95% by volume or less, the content of the hollow particles is 10% by mass or more and 150% by mass or less with respect to 100% by mass of the resin, and the glass transition temperature is 0 ° C or less. It is characterized by being.

  The pressure-sensitive adhesive sheet of the present invention is characterized in that the pressure-sensitive adhesive member of the present invention is formed into a sheet.

  According to another aspect of the invention, an electronic apparatus includes the adhesive member according to the aspect of the invention.

  Further, the method for producing a pressure-sensitive adhesive member of the present invention includes a step of preparing the pressure-sensitive adhesive composition of the present invention, and a step of polymerizing the polymerizable compound contained in the pressure-sensitive adhesive composition. I do.

  Further, the method for producing a pressure-sensitive adhesive sheet of the present invention includes a step of preparing the pressure-sensitive adhesive composition of the present invention, and a step of polymerizing the polymerizable compound contained in the pressure-sensitive adhesive composition to form a sheet. It is characterized by including.

  According to the present invention, a pressure-sensitive adhesive having a low dielectric constant and transparency can be provided.

FIG. 1 is a schematic sectional view showing an example of the adhesive sheet of the present invention.

(Adhesive composition of the present invention)
Various means for maintaining the transparency of the adhesive sheet including the hollow particles were examined. In general, it is known that there is a relationship represented by the following equation (1) between the dielectric constant (ε) and the refractive index (n).
ε = n ² (1)

  From the above equation (1), it can be seen that the dielectric constant can be lowered by lowering the refractive index. For that purpose, it has been thought that hollow particles conventionally used for an antireflection film or the like may be included in the adhesive. However, even if hollow particles having a particle diameter of 100 nm or less used for an antireflection film or the like are simply added to a conventional adhesive to form an adhesive layer, the transparency of the adhesive layer is not sufficiently improved. I understood that. Thus, the present inventors have conducted intensive studies and found that in order to impart transparency to the pressure-sensitive adhesive to which the hollow particles were added, the number average molecular weight of the polymerizable compound used to produce the pressure-sensitive adhesive had to be 10,000 or less. The present invention has been completed, and the present invention has been completed.

  That is, the pressure-sensitive adhesive composition of the present invention contains hollow particles and a polymerizable compound, the average particle size of the primary particles of the hollow particles is 30 nm or more and 500 nm or less, and the porosity of the hollow particles is 20% by volume or more and 95% by volume or less, the number average molecular weight of the polymerizable compound is 10000 or less, and the content of the hollow particles is 100 mass% of a solid component containing the polymerizable compound other than the hollow particles. Parts by mass and not less than 10 parts by mass and not more than 150 parts by mass.

  The pressure-sensitive adhesive composition of the present invention is a polymer having hollow particles having an average particle diameter of primary particles of 30 to 500 nm and a porosity of 20 to 95 volume%, and a number average molecular weight of 10,000 or less. Since it contains a conductive compound, a pressure-sensitive adhesive having a low dielectric constant and transparency can be provided. However, since the pressure-sensitive adhesive composition of the present invention generates a pressure-sensitive adhesive force by polymerizing the polymerizable compound, the pressure-sensitive adhesive composition of the present invention itself has no pressure-sensitive adhesive force or only a small pressure-sensitive adhesive force. It does not have.

  Further, the content of the hollow particles is required to be set to 10 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the solid component containing the polymerizable compound other than the hollow particles, and 20 parts by mass or more. 120 parts by mass or less is more preferable. When the content of the hollow particles is less than 10 parts by mass, the effect of reducing the dielectric constant of the pressure-sensitive adhesive decreases, and when the content of the hollow particles exceeds 150 parts by mass, the transparency of the pressure-sensitive adhesive may decrease. is there.

  Hereinafter, each component of the adhesive composition of the present invention will be described in detail.

<Hollow particles>
The average particle size of the hollow particles used in the present invention needs to be 30 nm or more and 500 nm or less, and more preferably 50 nm or more. When the average particle diameter is less than 30 nm, the glass transition temperature of the pressure-sensitive adhesive tends to increase, and the pressure-sensitive adhesive may have poor adhesion. This is presumably because the smaller the average particle diameter of the hollow particles, the larger the number of particles contained in a unit mass, the hollow particles become pseudo-crosslinking points in the adhesive, and the glass transition temperature of the adhesive increases. On the other hand, if the average particle diameter exceeds 500 nm, the haze increases due to an increase in light scattering, and the transparency is not improved.

  The porosity of the hollow particles needs to be 20% by volume or more and 95% by volume or less. When the porosity is less than 20% by volume, the dielectric constant of the pressure-sensitive adhesive does not easily decrease. On the other hand, if the porosity exceeds 95% by volume, the shell wall of the particles becomes thin and easily crushed, or the dielectric constant of the pressure-sensitive adhesive hardly decreases.

  The average particle diameter and porosity of the hollow particles can be calculated by observing the hollow particles with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). In the above observation, the hollow particles may be directly observed, or the hollow particles may be observed by cross-section processing by ion milling, or the hollow particles may be cross-section processed by a microtome or the like after being embedded in a resin. May be observed. In any case, for 10 or more of the above hollow particles, the particle diameter and the thickness of the shell wall are measured, and the average particle diameter and the average thickness of the shell wall are obtained. What is necessary is just to find the rate. Here, the particle diameter of the hollow particles refers to the size of so-called primary particles, and when the hollow particles are spherical or ellipsoidal in which the ratio of the major axis length to the minor axis length is 1 to 3.5. The maximum passing diameter is defined as the particle diameter, and in the case of other particles, the major axis diameter is defined as the particle diameter of the particle.

Porosity (%) = [(average particle diameter−average thickness of shell wall × 2) / average particle diameter] ³ × 100 (2)

  The content of the hollow particles contained in the adhesive composition of the present invention is, as described above, 10 parts by mass or more and 150 parts by mass or less based on 100 parts by mass of the solid component containing the polymerizable compound other than the hollow particles. Although set, the solid components other than the polymerizable compound include, for example, optional components such as a photopolymerization initiator, a resin polymer, a dispersant, and a tackifier. The content of the hollow particles can be measured, for example, by a thermal analysis method. That is, after the non-solid components such as a solvent are removed by heating the adhesive composition, the mass of the remaining solid components is measured, and further heated to around 700 ° C. to burn off solid components other than the hollow particles. The mass of the residue after the measurement is measured. Since the mass of the residue is considered to be the mass of the hollow particles, the content of the hollow particles contained in the adhesive composition can be determined from the mass of the residue and the mass of the solid component. Similarly, the content of hollow particles contained in an adhesive member (adhesive) described later can be measured.

The material of the hollow particles is not limited, and any of hollow inorganic particles and hollow organic particles can be used, and hollow silica particles, which are hollow inorganic particles, are particularly preferable. This is because the hollow silica particles have high physical strength and excellent dispersibility in the adhesive composition. The hollow silica particles may contain other metal elements in addition to SiO ₂ as a component thereof, or may be a hydrated compound.

  The method for producing the hollow silica particles having an average particle diameter of 30 nm or more and 500 nm or less is not particularly limited. For example, the hollow silica particles can be produced by a template method as described in Non-Patent Document 1 described above. More specifically, the method using the air bubbles described in Non-Patent Document 2 as a template, the inorganic template method using the inorganic particles described in Patent Documents 6, 7, and 8 as templates, the Patent Document 9 described above, It can be produced by an organic template method using the organic particles described in 10 as a template.

  Further, the hollow silica particles may be subjected to a surface treatment in order to improve the compatibility with the resin constituting the adhesive. The surface treatment may be performed, for example, by adding a silicon coupling agent to a dispersion or suspension of hollow silica particles. Although the organic functional group that modifies the surface of the hollow silica particle varies depending on the silicon coupling agent used, it is preferable to modify the surface with a methyl group, a phenyl group, or the like for surface treatment.

<Polymerizable compound>
The number average molecular weight of the polymerizable compound used in the present invention must be 10,000 or less. By using the above polymerizable compound, a pressure-sensitive adhesive having transparency can be provided. The number average molecular weight can be measured by an osmotic pressure method, a vapor pressure method, a gel permeation chromatography (GPC) method, or the like, but is preferably measured by a GPC method using polystyrene as a standard.

  If the number average molecular weight of the polymerizable compound exceeds 10,000, the transparency of the pressure-sensitive adhesive after curing may be lowered, possibly due to aggregation of hollow particles in the pressure-sensitive adhesive composition before the curing treatment. As described above, it is reported in Patent Document 11 that the aggregation of particles is related to the molecular weight of the polymerizable compound used. In Patent Document 11, solid particles (non-hollow particles) having a high refractive index are used, and since hollow particles are used in the present invention, it is presumed that the molecular weights at which aggregation starts are different.

  As long as the number average molecular weight of the polymerizable compound is 10,000 or less, various monomers or oligomers can be used alone or in combination. However, the polymerizable compound preferably contains at least the oligomer. As the above oligomer, urethane acrylate, polyether acrylate, polyester acrylate, butadiene oligomer, acrylic oligomer and the like can be suitably used. When the oligomer is used, the so-called film-forming property is improved, the molecular weight between cross-linking points is increased, and the adhesiveness is improved as compared with the case where the monomer is used alone.

  Examples of the monomer include monofunctional monomers such as acrylic acid, 2-ethylhexyl acrylate, and butyl acrylate, and polyfunctional monomers such as bifunctional monomers containing an acrylic group at both ends of polyethylene glycol. By adding the above-mentioned monomer as the above-mentioned polymerizable compound, it is possible to adjust the properties of the pressure-sensitive adhesive such as pressure-sensitive adhesiveness.

  The polymerizable compound is a resin containing a functional group that reacts when irradiated with radiation such as gamma rays, electron beams, and ultraviolet rays. As the functional group that reacts when irradiated with radiation, an acryl group or a methacryl group is preferable. When ultraviolet rays are used as the radiation, the adhesive composition of the present invention preferably contains a photopolymerization initiator together with the polymerizable compound. Examples of the photopolymerization initiator include 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, and 2-hydroxy-2-methyl-1-phenylpropan-1-one. , 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethyl Benzoyl-diphenyl-phosphine oxide and the like can be preferably used. The addition amount of the photopolymerization initiator may be 0.1 to 10 parts by mass, and preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the polymerizable compound.

<Other ingredients>
A tackifier may be added to the adhesive composition of the present invention as needed. Examples of the tackifier include terpene resins, terpene phenol resins, rosin resins, petroleum resins, phenol resins, and the like.

  The method for producing the pressure-sensitive adhesive composition of the present invention is not particularly limited, and for example, the above-described components may be mixed with a solvent as needed, and the solid components may be sufficiently dispersed. Although the mixing method is not particularly limited, for example, mixing can be performed using a disper, a homomixer, a ribbon mixer, a paddle mixer, a planetary mixer, a roll mill, a kneader, a ball mill, a sand mill, a high-pressure homogenizer, an ultrasonic disperser, or the like.

  Examples of the solvent include ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone, alcohols such as ethanol, propanol and butanol, ethyl acetate, butyl acetate, esters such as γ-butyrolactone, toluene and xylene. And the like can be used alone or as a mixture.

(Adhesive member of the present invention)
The pressure-sensitive adhesive member of the present invention is formed by polymerizing the polymerizable compound contained in the pressure-sensitive adhesive composition of the present invention, and includes hollow particles and a resin, and has an average of primary particles of the hollow particles. particle diameter, is at 30nm or more 500nm or less, the porosity of the hollow particles is not more than 20 vol% to 95 vol%, the content of the hollow particles relative to the resin 100 parts by weight 10 parts by weight 150 parts by mass or less, and the glass transition temperature of the adhesive member is 0 ° C. or less.

  Since the pressure-sensitive adhesive member of the present invention is formed by polymerizing the polymerizable compound contained in the pressure-sensitive adhesive composition of the present invention, it has a low dielectric constant and transparency.

  The resin is preferably at least one selected from a urethane resin, a polyether resin, a polyester resin, and an acrylic resin. By using these resins, the adhesiveness is improved.

  The pressure-sensitive adhesive member of the present invention can be produced by a production method including a step of preparing the pressure-sensitive adhesive composition of the present invention and a step of polymerizing the polymerizable compound contained in the pressure-sensitive adhesive composition. The method of polymerizing the polymerizable compound is not particularly limited, but a method of irradiating the adhesive composition with ionizing radiation such as ultraviolet rays can be used.

  As the ionizing radiation, for example, ultraviolet rays, electron beams, β rays, etc. can be used, but ultraviolet rays are frequently used because they can be easily used. As an ultraviolet light source, a high-pressure mercury lamp, a metal halide lamp, an ultraviolet LED lamp, or the like can be used. When ultraviolet rays are used as the ionizing radiation, it is preferable that the adhesive composition contains a photopolymerization initiator as described above.

(Adhesive sheet of the present invention)
The pressure-sensitive adhesive sheet of the present invention is obtained by forming the pressure-sensitive adhesive member of the present invention into a sheet. Since the pressure-sensitive adhesive sheet of the present invention is formed by molding the above-mentioned pressure-sensitive adhesive member of the present invention, it has a low dielectric constant and transparency.

  The thickness of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and can be adjusted in a usage scene, and can be, for example, 10 to 250 μm.

  The adhesive sheet of the present invention may further include a release substrate on at least one surface. The provision of the release substrate facilitates handling of the pressure-sensitive adhesive sheet of the present invention.

  In addition, the pressure-sensitive adhesive sheet of the present invention includes a step of preparing the pressure-sensitive adhesive composition of the present invention, and a step of polymerizing the polymerizable compound contained in the pressure-sensitive adhesive composition to form a sheet. Can be manufactured by the method.

  The method of polymerizing the polymerizable compound contained in the adhesive composition to form a sheet is not particularly limited.For example, after forming the coating film by applying the adhesive composition on a substrate, It is possible to use a method of drying if necessary, further arranging a base material on the coating film if necessary, and then irradiating ionizing radiation such as ultraviolet rays. In that case, if a release substrate is used as the substrate, a pressure-sensitive adhesive sheet with a release substrate can be easily obtained. Also. When ultraviolet rays are used for ionizing radiation, it is preferable to use a transparent substrate on at least one of the above-mentioned substrates, on the side of irradiation with ultraviolet rays. Here, by adjusting the thickness of the coating film to the thickness of the pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet having a desired thickness can be produced.

  The method for applying the adhesive composition is not particularly limited as long as it is a coating method capable of forming a smooth coating film. For example, a gravure roll method, a microgravure roll method, a microgravure coater method, Examples include a slit die coating method, a comma coating method, a spin method, a knife method, a kiss method, a squeeze method, a reverse roll method, a dip method, and a bar coating method.

  The base material is not particularly limited, for example, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, cellulose resins such as cellulose triacetate, amide resins such as nylon and aramid, polyphenylene ether, polysulfone ether and the like. Films or sheets made of materials such as polyether-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyamide-imide-based resins, aromatic polyamide-based resins, cycloolefin polymers, and paper can be used.

  In order to impart releasability to the base material, a release layer made of a silicone resin or the like may be formed on at least one surface of the base material.

  Next, the pressure-sensitive adhesive sheet of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the adhesive sheet of the present invention. In FIG. 1, an adhesive sheet 10 of the present invention includes a sheet-like adhesive 12 between release films 11 and 13. When the pressure-sensitive adhesive sheet 10 is used, the release films 11 and 13 may be removed, the sheet-shaped pressure-sensitive adhesive 12 may be disposed between the bonding members, and bonded by pressing or the like.

(Electronic device of the present invention)
An electronic device of the present invention includes the adhesive member of the present invention, and the optical electronic members having transparency are joined to each other by the adhesive member. Since the electronic device of the present invention joins the optical electronic members using the above-mentioned adhesive member having a low dielectric constant and transparency, the electronic device can cope with a higher frequency of the electronic element.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples. In the following examples, “parts” means “parts by mass”.

(Example 1)
<Preparation of adhesive composition>
First, the following components (1) to (3) were placed in a stainless steel container and stirred and mixed to prepare a mixed solution.
(1) Polymerizable compound (urethane acrylate: trade name “Evecryl 230”, manufactured by Daicel Psytech Co., Ltd., number average molecular weight: 2500): 50 parts (2) photopolymerization initiator [bis (2,4,6-trimethylbenzoyl) ) -Phenylphosphine oxide]: 0.25 parts (3) Solvent (methyl ethyl ketone): 5 parts

Next, after mixing and stirring and mixing the following component (4) with the above mixture, the mixture is subjected to ultrasonic dispersion treatment while further cooling the container with water, and finally filtered through a filter having a pore size of 1 μm for adhesion. The composition was obtained.
(4) Methyl isobutyl ketone solution of hollow silica particles (manufactured by Nikki Shokubai Kasei Co., Ltd., trade name "Suria", solid content concentration: 25 mass%): 200 parts

<Preparation of adhesive sheet>
The above-mentioned adhesive composition is applied to a 38 μm-thick polyethylene terephthalate (PET) film with a release layer (manufactured by Nakamoto Pax Co.) using a film applicator capable of adjusting the coating film thickness, and dried at room temperature. Thus, a coating film was formed. Subsequently, the coating film was dried at 100 ° C., and a 50 μm-thick PET film with a release layer (manufactured by Nakamoto Pax Co., Ltd.) was laminated on the coating film. The film was brought into close contact with the film. Thereafter, the coating film was cured by irradiating ultraviolet rays to produce an adhesive sheet with a release PET film. The thickness of the coating film (adhesive layer) was adjusted to 25 μm. The ultraviolet irradiation was performed using a high-pressure mercury lamp so that the integrated light amount became 250 mJ / cm ² .

(Example 2)
An adhesive sheet was prepared in the same manner as in Example 1, except that the amount of the solvent was 55 parts and the amount of the solution of the hollow silica particles in the methyl isobutyl ketone was 60 parts.

(Example 3)
<Preparation of hollow silica particles>
75 parts of a polystyrene particle suspension (manufactured by Polyscience, amino group modification, average particle diameter of particles: 0.1 μm, solid content concentration: 2.5% by mass) was heated to 40 ° C. The following components (1) to (4) were blended with stirring, and further stirred for 30 minutes to prepare a mixed solution.
(1) Water: 155 parts (2) Isopropanol: 800 parts (3) Ammonia water (concentration: 28%): 30 parts (4) Tetraethoxysilane: 15 parts

  Subsequently, the mixture was allowed to stand at 40 ° C. for 10 hours, and then returned to room temperature. Thereafter, the generated particles were collected by centrifugation and dispersed in water. The above-described centrifugation, particle collection, and aqueous dispersion were repeated twice, and after filtration with a filter, the particles were collected by centrifugation. Thereafter, the collected particles were dried at 100 ° C. for 5 hours, and the obtained powder was placed in a firing furnace, heated to 600 ° C. at a rate of 1 ° C./min while airflow, and fired at 600 ° C. for 2 hours. Further, the temperature was raised to 800 ° C. at a rate of 5 ° C./min, and calcined at 800 ° C. for 3 hours, and then gradually cooled to room temperature to obtain hollow silica particles.

<Preparation of adhesive composition>
First, the following components (1) to (3) were placed in a stainless steel container and stirred and mixed to prepare a mixed solution.
(1) Polymerizable compound (urethane acrylate: manufactured by Nippon Synthetic Chemical Company, trade name “Shikko UV-3000B”, number average molecular weight: 9000): 50 parts (2) Photopolymerization initiator [bis (2,4,6- Trimethylbenzoyl) -phenylphosphine oxide]: 0.25 part (3) Solvent (methyl ethyl ketone): 50 parts

  30 parts of the hollow silica particles prepared above and 190 parts of a solvent (methyl ethyl ketone) were sufficiently stirred and mixed to prepare a hollow silica particle suspension. Next, after mixing and stirring and mixing the above-mentioned hollow silica particle suspension with the above-mentioned liquid mixture, an ultrasonic dispersion treatment was further performed while cooling the container with water to obtain an adhesive composition.

  Except having used the said adhesive composition, it carried out similarly to Example 1, and produced the adhesive sheet.

(Example 4)
<Preparation of hollow silica particles>
Using 75 parts of a polystyrene particle suspension (manufactured by Polyscience Inc., amino group modification, average particle diameter of particles: 0.2 μm, solid content concentration: 2.5% by mass), the blending amount of tetraethoxysilane was 7.5. The hollow silica particles were produced in the same manner as in Example 3, except that the parts were changed to parts.

  The above-prepared hollow silica particles: 60 parts and a solvent (methyl ethyl ketone): 280 parts were sufficiently stirred and mixed to prepare a hollow silica particle suspension. Except having used the said hollow silica particle suspension, it carried out similarly to Example 3, and obtained the adhesive composition.

  Except having used the said adhesive composition, it carried out similarly to Example 1, and produced the adhesive sheet.

(Example 5)
<Preparation of hollow silica particles>
Using 75 parts of a polystyrene particle suspension (manufactured by Polyscience, amino group modification, average particle diameter of particles: 0.2 μm, solid content concentration: 2.5% by mass), the blending amount of tetraethoxysilane to 40 parts Except having been changed, hollow silica particles were produced in the same manner as in Example 3.

  The above-prepared hollow silica particles: 60 parts and a solvent (methyl ethyl ketone): 210 parts were sufficiently stirred and mixed to prepare a hollow silica particle suspension. Except having used the said hollow silica particle suspension, it carried out similarly to Example 3, and obtained the adhesive composition.

  Except having used the said adhesive composition, it carried out similarly to Example 1, and produced the adhesive sheet.

(Comparative Example 1)
<Preparation of adhesive composition>
First, the following components (1) to (3) were placed in a stainless steel container and stirred and mixed to prepare a mixed solution.
(1) Polymerizable compound (urethane acrylate: trade name “Evecryl 230” manufactured by Daicel Cytec Co., Ltd., number average molecular weight: 2500): 40 parts (2) photopolymerization initiator [bis (2,4,6-trimethylbenzoyl) ) -Phenylphosphine oxide]: 0.2 parts (3) Solvent (methyl ethyl ketone): 60 parts

  The mixture was filtered through a filter having a pore size of 1 μm to obtain a sticky composition containing no hollow silica particles. Except having used the said adhesive composition, it carried out similarly to Example 1, and produced the adhesive sheet.

(Comparative Example 2)
<Preparation of adhesive composition>
First, the following components (1) to (3) were placed in a stainless steel container and stirred and mixed to prepare a mixed solution.
(1) Adhesive resin solution (manufactured by Soken Chemical Co., trade name "SK Dyne 1435", number average molecular weight: 100,000, solid content concentration: 30% by mass): 50 parts (2) Crosslinking agent (manufactured by Soken Chemical Company, product Name "TD-75"): 0.15 parts (3) Solvent (methyl ethyl ketone): 10 parts

Next, after mixing and stirring and mixing the following component (4) with the above mixture, the mixture was subjected to ultrasonic dispersion while further cooling the container with water.
(4) Methyl isobutyl ketone solution of hollow silica particles (manufactured by Nikki Shokubai Kasei Co., Ltd., trade name "Suria", solid content concentration: 25 mass%): 60 parts

  When the above-mentioned adhesive composition was observed, it was confirmed that precipitation occurred in the liquid. That is, it was found that in the adhesive composition of Comparative Example 2, the hollow silica particles were precipitated without being uniformly dispersed. Therefore, in Comparative Example 2, no pressure-sensitive adhesive sheet was produced.

(Comparative Example 3)
An adhesive sheet was prepared in the same manner as in Example 1 except that the amount of the solvent was changed to 60 parts and the amount of the solution of the hollow silica particles in the methyl isobutyl ketone was changed to 360 parts.

(Comparative Example 4)
Hollow silica particles were produced in the same manner as in Example 3, except that the amount of tetraethoxysilane was changed to 125 parts. Except having used the said hollow silica particle, it carried out similarly to Example 3, and obtained the adhesive composition.

  Except having used the said adhesive composition, it carried out similarly to Example 1, and produced the adhesive sheet.

(Comparative Example 5)
Except for using 75 parts of a polystyrene particle suspension (manufactured by Polyscience, amino group modification, average particle diameter of particles: 0.5 μm, solid content concentration: 2.5% by mass), the same as in Example 3 was used. Hollow silica particles were produced. Except having used the said hollow silica particle, it carried out similarly to Example 3, and obtained the adhesive composition.

  Except having used the said adhesive composition, it carried out similarly to Example 1, and produced the adhesive sheet.

  Next, the properties of the pressure-sensitive adhesive sheets with a release PET film produced in Examples 1 to 5 and Comparative Examples 1 and 3 to 5 were evaluated as follows. However, the evaluation of Comparative Example 2 in which no adhesive sheet was produced was not performed.

<Optical characteristics>
One PET film is peeled off from the produced pressure-sensitive adhesive sheet with a release PET film, and the pressure-sensitive adhesive sheet after peeling off the PET film is attached to a slide glass ("S9111" manufactured by Matsunami Glass Co., Ltd.), and further the other. Was also peeled off to obtain a sample for evaluation. The haze of this evaluation sample was measured using a turbidity meter “NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd. according to a method corresponding to JIS K7361-1.

<Tackiness>
The adhesiveness was evaluated using the evaluation sample used for the evaluation of the optical characteristics. Specifically, when the slide glass of the sample for evaluation was vertically shaken lightly perpendicular to the ground, the case where the adhesive sheet was not peeled off from the slide glass was judged as having good adhesiveness, and the case where the adhesive sheet was peeled off. Was judged to have poor tackiness.

<Dielectric constant>
One PET film was peeled off from the prepared PSA film-attached PSA sheet, and the PSA sheet after peeling the PET film was applied to the main prism surface of an Abbe refractometer (Atago, "NAR-2T"). After sticking and further peeling off the other PET film, the refractive index of the adhesive sheet was measured, and the value of the refractive index was squared to obtain the dielectric constant.

<Glass transition temperature (Tg)>
Using a differential scanning calorimeter (Rigaku Corporation, “DSC8230”), peeling off all the PET films from the prepared release sheet with the PET film and peeling off the PET film from the pressure-sensitive adhesive sheet, The DSC curve was measured, and the obtained DSC curve was analyzed with an analysis program manufactured by Rigaku Corporation to determine the glass transition temperature of the adhesive sheet.

<Average particle diameter and porosity of hollow silica particles>
A sample was prepared by processing the cross-section of the pressure-sensitive adhesive sheet after the PET film was peeled off, the sample was observed by SEM, the particle diameter of the primary particles of 20 hollow silica particles and the thickness of the shell wall were measured, and the arithmetic mean was obtained. The average particle diameter of the hollow silica particles and the average thickness of the shell wall were determined. The porosity of the hollow silica particles was determined from these values. However, for Comparative Example 2, the prepared adhesive composition was dried, and the powder after drying was observed with a TEM, and the average particle diameter and porosity of the hollow silica particles were determined in the same manner as described above.

  Table 1 shows the above results. In Table 1, the content of the hollow silica particles used is shown in terms of the amount based on 100 parts by mass of the solid component containing the polymerizable compound other than the hollow particles.

  From Table 1, in Examples 1 to 5, the hollow particles having an average particle diameter of 30 to 500 nm and a porosity of 20 to 95% by volume are used, and the polymer particles having a number average molecular weight of 10,000 or less are used. Of the solid component containing the polymerizable compound other than the hollow particles was 10 to 150 parts by mass, so that the haze was 2% or less, the transparency was good, and the hollow particles were not added. The dielectric constant was lower than that of Comparative Example 1. In Examples 1 to 5, the glass transition temperature was 0 ° C. or lower, and the adhesiveness was good.

  As described above, Comparative Example 1, in which no hollow particles were added, had a high dielectric constant. In Comparative Example 2, since a pressure-sensitive resin having a number average molecular weight of 100,000 was used, hollow particles were aggregated during the preparation of the pressure-sensitive adhesive composition to cause precipitation, and a pressure-sensitive adhesive sheet could not be prepared. In Comparative Example 3, since the content of the hollow particles exceeded 150 parts by mass, the particles were aggregated, the haze was 3%, and the transparency was poor. In Comparative Example 3, it is considered that the adhesion was inferior because the number of added particles was large. In Comparative Example 4, the porosity of the hollow particles was less than 20% by volume, so the dielectric constant was as high as in Comparative Example 1, and the haze was more than 2% and the transparency was poor. In Comparative Example 5, since the average particle diameter of the hollow particles exceeded 500 nm, it was considered that the haze exceeded 2% and the transparency was poor.

  INDUSTRIAL APPLICABILITY The present invention can provide a pressure-sensitive adhesive having a low dielectric constant and transparency, and can be used for a pressure-sensitive adhesive member of an optical electronic member requiring a low dielectric constant and transparency. It is possible to cope with higher frequencies of electronic elements used in electronic circuits.

10 adhesive sheet 11, 13 release film 12 adhesive

Claims (11)

Hollow particles, a pressure-sensitive adhesive composition comprising a polymerizable compound,
The average particle diameter of the primary particles of the hollow particles is 30 nm or more and 500 nm or less,
The porosity of the hollow particles is 20% by volume or more and 95% by volume or less,
The number average molecular weight of the polymerizable compound is 10,000 or less,
The content of the hollow particles, other than the hollow particles, the per 100 parts by mass of the solid component containing a polymerizable compound, Ri least 10 parts by weight 150 parts by der less,
The hollow particles are tacky composition characterized Oh Rukoto hollow silica particles. The pressure-sensitive adhesive composition according to claim 1 , wherein the polymerizable compound includes a polymerizable oligomer. The adhesive composition according to claim 2 , wherein the polymerizable oligomer is at least one selected from urethane acrylate, polyether acrylate, and polyester acrylate. The pressure-sensitive adhesive composition according to any one of claims 1 to 3 , further comprising a photopolymerization initiator. An adhesive member formed from the adhesive composition according to any one of claims 1 to 4,
And hollow particles, and the resin only contains,
The average particle diameter of the primary particles of the hollow particles is 30 nm or more and 500 nm or less,
The porosity of the hollow particles is 20% by volume or more and 95% by volume or less,
The content of the hollow particles is 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the resin,
An adhesive member having a glass transition temperature of 0 ° C. or lower. The adhesive member according to claim 5 , wherein the resin is at least one selected from a urethane resin, a polyether resin, a polyester resin, and an acrylic resin. Adhesive sheet, characterized in that the adhesive member according to claim 5 or 6 is obtained by forming into a sheet. The pressure-sensitive adhesive sheet according to claim 7 , further comprising a release substrate on at least one surface. An electronic apparatus comprising an adhesive member according to claim 5 or 6. A step of preparing the adhesive composition according to any one of claims 1 to 4 ,
Polymerizing the polymerizable compound contained in the adhesive composition. A step of preparing the adhesive composition according to any one of claims 1 to 4 ,
Polymerizing the polymerizable compound contained in the adhesive composition to form a sheet.

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