JP2014172960A - Adhesive composition and sheet-like adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition having a high refractive index, capable of forming an adhesive having low haze and a high refractive index.SOLUTION: An adhesive composition contains metal oxide particles, a polymeric resin, and a dispersant. The metal oxide particles are at least one kind of particles selected from a group consisting of titanium oxide, zirconium oxide, zinc oxide, diniobium pentoxide, and a titanic acid compound, and have an average particle diameter of 20-150 nm. The amount of the metal oxide particles contained in the adhesive composition is 50-80 wt.%, and the polymeric resin has a numerical average molecular weight of 10,000 to 50,000.

Description

  The present invention relates to a high refractive index pressure-sensitive adhesive composition and a sheet-like pressure-sensitive adhesive.

  Semiconductor elements such as a light emitting diode (LED), organic electroluminescence (EL), and charge coupled device (CCD) emit light or receive light and perform photoelectric conversion, and are so-called optical elements. An optical element expresses light receiving and emitting functions, and is usually sealed as a polymer resin such as an epoxy resin, a silicon resin, an acrylic resin, or coated as a surface with glass and used as an optical device. Yes.

  An optical element is often manufactured using a high refractive index material such as a metal or a metal oxide, usually having a refractive index of 1.7 or more. For this reason, if a high refractive index polymer resin is used as the sealant, the difference in refractive index between the optical element and the sealant can be reduced, so that the influence of interface reflection is suppressed, and the light extraction efficiency or The light receiving efficiency is increased. By the way, since the refractive index of the polymer resin used for the sealant is about 1.5, a method of adding metal oxide particles to increase the refractive index has been proposed (for example, Patent Documents). 1, 2) Although the resin composition thus obtained has a high refractive index, it has no tackiness.

  When tackiness is imparted to the high refractive index resin composition, the resin composition can be used as a pressure-sensitive adhesive composition. When the pressure-sensitive adhesive composition is used for manufacturing an optical device, for example, An adhesive composition is formed into a sheet and used as a sheet-like adhesive. In this case, the optical element and glass or a conventional resin composition can be bonded via a sheet-like pressure-sensitive adhesive. Therefore, the pressure-sensitive adhesive using the above-mentioned pressure-sensitive adhesive composition is capable of forming glass or a conventional resin composition. In combination with processability, the degree of freedom in design is improved, and improvement in the characteristics or functionality of the optical device can be expected. Therefore, an adhesive composition having a high refractive index including metal oxide particles and an adhesive polymer resin has been studied.

  However, when a sheet-like pressure-sensitive adhesive is formed using a pressure-sensitive adhesive composition containing metal oxide particles and adhesive polymer resin, the optical characteristics of the sheet-like pressure-sensitive adhesive may deteriorate due to particle mixing, or metal oxide particles. There may be a problem that the adhesiveness of the sheet-like pressure-sensitive adhesive is reduced due to exposure to the surface. As a method for solving such a problem, for example, Patent Document 3 proposes a method for improving the light transmittance of the sheet-like pressure-sensitive adhesive by setting the dispersion average particle size of the metal oxide particles to 1 to 20 nm. ing. Patent Document 4 proposes a method for improving the adhesiveness of a sheet-like adhesive by chemically bonding a polymer to metal oxide particles to impart adhesiveness.

JP 2012-87316 A JP 2011-213886 A JP 2009-120726 A JP 2012-52010 A

  However, the methods proposed in Patent Documents 3 and 4 above can improve the light transmittance and tackiness of the sheet-like pressure-sensitive adhesive, but the optical properties of the sheet-like pressure-sensitive adhesive, in particular, haze, that is, haze. Cannot be improved sufficiently and is not suitable as an adhesive for optical devices. In particular, in a highly refractive sheet-like pressure-sensitive adhesive having a refractive index of 1.65 or more, it is required to reduce haze, specifically, to reduce haze to 20% or less.

  The present invention has been made in view of the above circumstances, has a low refractive index, a high refractive index adhesive composition capable of forming a high refractive index adhesive, and the adhesive composition. A high refractive index sheet-like pressure-sensitive adhesive suitable for production of an optical device is provided.

  In order to solve the above problems, the pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing metal oxide particles, a polymer resin, and a dispersant, and the metal oxide particles include titanium oxide, zirconium oxide, It is composed of at least one selected from the group consisting of zinc oxide, niobium pentoxide, and titanic acid compound, and is an average particle diameter of 20 to 150 nm. The content of the metal oxide particles is the pressure-sensitive adhesive composition. The polymer resin is characterized by having a number average molecular weight of 10,000 to 50,000.

  The 1st sheet-like adhesive of this invention forms the adhesive composition of this invention in a sheet form, It is characterized by the above-mentioned.

  The second sheet-like pressure-sensitive adhesive of the present invention is a sheet-like pressure-sensitive adhesive containing metal oxide particles, a polymer resin, and a dispersant, and the metal oxide particles include titanium oxide, zirconium oxide, zinc oxide, It consists of at least one selected from the group consisting of niobium pentoxide and a titanic acid compound, and is an average particle diameter of 20 to 150 nm. The content of the metal oxide particles in the sheet-like pressure-sensitive adhesive The glass transition temperature of the sheet-like pressure-sensitive adhesive is −45 to 10 ° C., and the refractive index of the sheet-like pressure-sensitive adhesive is 1.65 to 1.82. And

  According to the present invention, there is provided a high refractive index pressure-sensitive adhesive composition having a low haze and capable of forming a high refractive index pressure-sensitive adhesive, and a high refractive index sheet-like pressure-sensitive adhesive having a low haze and suitable for production of an optical device. Can be provided.

  Usually, a polymer resin having a number average molecular weight of several hundreds of thousands is used as the adhesive polymer resin. This is to increase the cohesive force of the pressure-sensitive adhesive and increase the holding power. By cross-linking such a polymer resin, the adhesiveness, peel strength, etc. of the adhesive can be adjusted. However, as a result of intensive studies by the present inventors, it has been found that the haze of the pressure-sensitive adhesive increases as the molecular weight of the polymer resin increases. The pressure-sensitive adhesive is formed using a pressure-sensitive adhesive composition containing fine metal particles and a pressure-sensitive polymer resin. When a polymer resin having a molecular weight as large as several hundreds of thousands is used as the pressure-sensitive polymer resin, the pressure-sensitive adhesive It is considered that the metal fine particles are aggregated and the haze of the pressure-sensitive adhesive is increased. Therefore, the present inventors have newly investigated an adhesive polymer resin suitable for a high refractive index adhesive, replacing the conventional adhesive polymer resin having a molecular weight of several hundreds of thousands. The adhesive composition was completed.

  The pressure-sensitive adhesive composition of the present invention contains metal oxide particles, a polymer resin, and a dispersant.

  Hereinafter, the configuration of the pressure-sensitive adhesive composition of the present invention will be described in detail.

(Metal oxide particles)
For the metal oxide particles contained in the pressure-sensitive adhesive composition of the present invention, at least one selected from the group consisting of titanium oxide, zirconium oxide, zinc oxide, niobium pentoxide, and titanate compounds is used. By using at least one kind of such metal oxide particles, an adhesive composition having a high refractive index can be obtained. The metal oxide particles may contain other metal oxides such as aluminum oxide and silicon oxide in order to suppress catalyst activity or improve dispersibility.

  Examples of the titanate compound include barium titanate, calcium titanate, and strontium titanate. Specific examples of titanate compounds include barium titanate “T-BTO-30RF”, “T-BTO-50RF”, “T-BTO-100RF”, “T-BTO-20RF” manufactured by Toda Kogyo, Japan. “PARCERAM AKBST (9: 1)” manufactured by Chemical Industry Co., Ltd., ultra-fine titanium oxide “TTO-55A”, “TTO-55B”, “TTO-55C”, “TTO-55D”, “TTO” manufactured by Ishihara Sangyo Co., Ltd. -51A "," TTO-51C ", Nippon Aerosil's titanium dioxide" Aeroxide P25 "," Aeroxide T805 ", titanium oxide" STX501 "and the like.

  The average particle diameter of the metal oxide particles is 20 to 150 nm. Usually, metal oxide particles cause light scattering in the pressure-sensitive adhesive and affect haze. In the present invention, by using metal oxide particles having an average particle diameter of 20 to 150 nm, the haze is 20%. A high refractive index adhesive reduced to the following can be produced. If the average particle diameter is less than 20 nm, the dispersibility of the metal oxide particles tends to be inferior and adjustment of the haze of the pressure-sensitive adhesive tends to be difficult. If the average particle diameter exceeds 150 nm, light scattering by the metal oxide particles increases. The haze tends to increase. In this specification, the average particle diameter is an average value obtained by measuring the particle diameter of 100 metal oxide particles using an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). It is shown by.

  The metal oxide particles preferably have a refractive index of 1.9 or more. When metal oxide particles having a refractive index of less than 1.9 are used, it is necessary to increase the content of metal oxide particles in order to obtain a high refractive index adhesive composition. As the amount increases, the haze of the pressure-sensitive adhesive tends to increase.

  The refractive index of the metal oxide particles can be estimated as follows. When the refractive index of the pressure-sensitive adhesive is n and the refractive index and volume fraction of each component are ni and νi, the following formula (1) is established. Therefore, the refractive index of the pressure-sensitive adhesive produced using a pressure-sensitive adhesive composition containing a polymer resin having a known refractive index and specific gravity, a dispersant having a known refractive index and specific gravity, and metal oxide particles having a known specific gravity is obtained. If measured, the refractive index of the metal oxide particles can be estimated.

  For example, barium titanate particles whose specific refractive index is unknown (specific gravity: 5.41): 94 parts by weight, dispersant (specific gravity: 1.08, refractive index: 1.48): 6 parts by weight, and a solvent are appropriately blended. Of the pressure-sensitive adhesive obtained by applying a mixture of polyester resin (specific gravity: 1.19, refractive index: 1.52): 219.3 parts by weight on a base material and drying the dispersion. The refractive index was 1.577. In this case, the weight ratio of barium titanate, dispersant, and polyester resin in the pressure-sensitive adhesive is 29.4% by weight, 1.9% by weight, and 68.7% by weight. By dividing the weight ratio by the specific gravity and converting it to a volume fraction, and substituting the respective refractive index and volume fraction into the above formula (1), the refractive index of the barium titanate particles can be obtained as 2.48. In the present invention, the refractive index of the metal oxide particles was thus determined. Even if the materials are the same, the refractive index and specific gravity differ depending on the production method and particle diameter.

  Content of the said metal oxide particle is 50 to 80 weight% in an adhesion composition. The greater the content of the metal oxide particles, the higher the refractive index of the pressure-sensitive adhesive composition, and a higher refractive index pressure-sensitive adhesive can be produced. When the content of the metal oxide particles exceeds 80% by weight, the pressure-sensitive adhesive The haze of the pressure-sensitive adhesive tends to increase due to the formation of voids. Moreover, since the refractive index of an adhesive composition will become low when there is little content of metal oxide particle | grains, in order to obtain an adhesive with a refractive index of 1.65 or more, it is preferable to set it as 50 weight% or more.

(Polymer resin)
As the polymer resin contained in the pressure-sensitive adhesive composition of the present invention, a polymer resin having a number average molecular weight of 10,000 to 50,000 is used. By using such a polymer resin, an adhesive having a haze of 20% or less can be produced.

  The pressure-sensitive adhesive composition used to form a conventional pressure-sensitive adhesive needs to be hardly soluble in a solvent (for example, tetrahydrofuran) by adding a curing agent in order to increase the cohesive force of the polymer resin and increase the holding power. This is not necessary in the invention. In the present invention, it is considered that the metal oxide particles serve as a pseudo-crosslinking point of the polymer resin and show the effect of improving the cohesive force. In addition, in the case of a high refractive index adhesive composition, if a hardener is added to make it difficult to dissolve, the crosslinking point of the polymer resin will increase too much, or the adhesive will not be adhesive and may adhere to a glass plate or the like. However, in the present invention, since no curing agent is used, the occurrence of such a problem can be prevented.

  Usually, since the adhesion operation is performed at room temperature, it is preferable to use a polymer resin that is easily deformed at room temperature in the present invention. Therefore, the glass transition temperature of the polymer resin used in the present invention is preferably 20 ° C. or less. Moreover, in order to prevent the shift | offset | difference of the bonding surface after adhesion, the glass transition temperature of the said polymer resin has preferable -40 degreeC or more.

  The content of the polymer resin is preferably 15 to 50% by weight in the adhesive composition. If the amount is less than 15% by weight, the pressure-sensitive adhesive tends to be inferior. If the amount is more than 50% by weight, the refractive index of the pressure-sensitive adhesive composition becomes low, and it is difficult to obtain a high-refractive index pressure-sensitive adhesive.

  Examples of the polymer resin include polyester resins such as polyester resins and polyester urethane resins; acrylic resins. Specific examples of polyester resins include “Byron 300”, “Byron 500”, “Byron 550”, “Byron 560”, “Byron 630”, “Byron 650”, “Byron 670”, “ “Byron GK130”, “Byron GK140”, “Byron GK150”, “Byron GK330”, “Byron GK570”, “Byron GK590”, “Byron GK680”, “Byron GK890”, “Byron BX1001”, “Byron UR2300”, “ Byron UR3200, “Byron UR3500”, “Byron UR5537”, “Byron UR6100”, “Byron UR8700” and the like can be mentioned.

(Dispersant)
In the present invention, in order to improve the dispersion state of the metal oxide particles in the pressure-sensitive adhesive composition and reduce the haze of the pressure-sensitive adhesive formed using the pressure-sensitive adhesive composition, a so-called dispersant is contained.

  The content of the dispersant is preferably 2 to 15% by weight with respect to the metal oxide particles. When the amount is less than 2% by weight, the dispersibility of the metal oxide particles is poor and the haze of the pressure-sensitive adhesive tends to increase. Moreover, when more than 15 weight%, there exists a tendency for the adhesiveness of an adhesive to be inferior.

  The dispersant preferably contains an acidic functional group that binds to the metal oxide particles. In particular, an acid value of 10 to 200 mgKOH / g is preferable. When the acid value is less than 10 mgKOH / g, the amount of the dispersant bound to the metal oxide particles decreases, the dispersibility of the metal oxide particles is poor, and the haze of the pressure-sensitive adhesive tends to increase. Moreover, when more than 200 mgKOH / g, a dispersing agent accelerates | stimulates re-aggregation of a metal oxide particle, the dispersibility of a metal oxide particle is inferior, and it exists in the tendency for the haze of an adhesive to become large.

  The dispersant is preferably flexible from the viewpoint of mixing with the polymer resin, and the melting point is preferably 60 ° C. or lower. When the melting point is higher than 60 ° C., the glass transition temperature of the pressure-sensitive adhesive is not sufficiently lowered, and the pressure-sensitive adhesive has a tendency to be inferior.

  As the dispersant, a known polymer dispersant such as a polyester resin, a resin including polyester and polyether, a polyester urethane resin, a polyurethane resin, or a polyacrylic resin can be used. Specifically, “Solspar 13240”, “Solspers 13940”, “Solspers 16000”, “Solspers 27000SC”, “Solspers 24000GR”, “Solspers 26000”, “Solspers 28000”, “Solspers 28000”, “Solspers 28000”, “ "Solsper 32000", "Sol Sparse 33000", "Sol Sparse 36600", "Sol Sparse 39000", "Sol Sparse 55000", "Sol Sparse 56000", "DISPERBYK-106", "DISPERBYK-110" manufactured by BYK Chemie, "DISPERBYK-111", "DISPERBYK-180", etc. are mentioned.

  Thus, the pressure-sensitive adhesive composition of the present invention is a high-refractive index pressure-sensitive adhesive composition having a low haze and capable of forming a high-refractive index pressure-sensitive adhesive. When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive for optical devices, the pressure-sensitive adhesive composition of the present invention is preferably formed into a sheet and used as a sheet-shaped pressure-sensitive adhesive.

  Next, the sheet-like pressure-sensitive adhesive of the present invention will be described.

  The sheet-like pressure-sensitive adhesive of the present invention is a sheet-like pressure-sensitive adhesive containing metal oxide particles, a polymer resin, and a dispersant, and the metal oxide particles include titanium oxide, zirconium oxide, zinc oxide, dipentapentoxide. It consists of at least one selected from the group consisting of niobium and a titanic acid compound and has an average particle size of 20 to 150 nm. The content of the metal oxide particles is 50 to 50 in the sheet-like pressure-sensitive adhesive. 80% by weight.

  Moreover, the glass transition temperature of the sheet-like pressure-sensitive adhesive of the present invention is −45 to 10 ° C., and the refractive index is 1.65 to 1.82. When the glass transition temperature exceeds 10 ° C, the adhesiveness is inferior. When the glass transition temperature is lower than -45 ° C, the bonded surface after the adhesion may shift with time. On the other hand, when the refractive index exceeds 1.82, the amount of metal oxide particles present on the surface of the sheet-like pressure-sensitive adhesive increases, and the tackiness tends to be inferior.

  As the metal oxide particles, the polymer resin, and the dispersant contained in the sheet-like pressure-sensitive adhesive of the present invention, the same ones as used in the above-mentioned pressure-sensitive adhesive composition of the present invention can be used.

  For example, the sheet-like pressure-sensitive adhesive of the present invention is a dispersion treatment of a mixture in which the metal oxide particles, the polymer resin, and the dispersant are dispersed in a solvent, and the mixture after the dispersion treatment is applied onto a substrate. After drying, it is obtained by removing the substrate. Without removing the substrate, it can also be used as an adhesive sheet comprising a substrate and a sheet-like adhesive. Moreover, it can be used as a pressure-sensitive adhesive sheet comprising a substrate, a sheet-like pressure-sensitive adhesive, and a peel-off type material by further providing a release-type material on the sheet-like pressure-sensitive adhesive. When using such an adhesive sheet, a base material and a peeling type material are removed as needed, and a sheet-like adhesive is affixed on arbitrary objects. The metal oxide particles, the polymer resin, and the dispersant may be simultaneously dispersed in a solvent, or after the dispersion treatment of the mixture in which the metal oxide particles and the dispersant are dispersed in the solvent, A polymer resin dissolved in may be added.

  Examples of the solvent include ketone solvents such as methyl ethyl ketone (MEK), cyclohexanone, methyl isobutyl ketone (MIBK), and isophorone; aromatic solvents such as toluene and xylene; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate. Organic solvents such as solvents; ether solvents such as tetrahydrofuran, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate;

  The dispersion treatment can be performed by a conventionally known method. For example, mechanical treatment using a dispersion medium such as a ball mill, a bead mill, a sand mill, a pico mill, or a paint conditioner, an ultrasonic disperser, a three roll mill, a planetary. Examples of the dispersion treatment include a mixer, a homogenizer, a disper, and a jet mill. Moreover, you may perform a dispersion | distribution process combining said disperser.

  As the base material, a transparent base material, a release-type material, or the like can be used. Specifically, a polyester film, a polypropylene film, a polyethylene terephthalate film, a glass plate, etc. are mentioned.

  Hereinafter, the present invention will be described in detail based on examples. “Parts” in the examples represents “parts by weight”. The following examples do not limit the present invention.

Example 1
First, a mixture containing the following components was placed in a dispersion container, and further 80 parts of zirconia beads having a diameter of 0.1 mm were added, followed by dispersion treatment using a paint conditioner.
(1) Metal oxide particles: Barium titanate particles (trade name “T-BTO-030RF”, particle size: 43 nm, manufactured by Toda Kogyo Co., Ltd.): 22.75 parts (2) Dispersant (trade name, manufactured by Avicia) “Solsperse 56000”, melting point: 55 ° C., acid value: 23 mg KOH / g) 1.98 parts (3) Polymer resin: polyester resin (trade name “Byron BX1001”, manufactured by Toyobo Co., Ltd., Tg: −18 ° C., (Molecular weight: 28000): 15.16 parts (4) Solvent: butyl acetate: 24.73 parts (5) Solvent: methyl ethyl ketone: 35.38 parts

  Next, the dispersion-treated mixture was passed through a filter with a filtration accuracy of 2 μm to remove zirconia beads, and then using an applicator, a polyethylene terephthalate (PET) film (Nakamoto Pax Co., Ltd. It was applied to a treated surface of “NS-50-MB” (thickness: 50 μm) and dried at 120 ° C. for 3 minutes to obtain a sheet-like pressure-sensitive adhesive. In the following description, a PET film in which a sheet-like adhesive is formed on one main surface is referred to as an adhesive sheet.

(Example 2)
Barium titanate particles (trade name “T-BTO-050RF”, particle diameter: 54 nm) manufactured by Toda Kogyo Co., Ltd., 22.99 parts) were used as metal oxide particles, and 1.47 parts of the dispersant was incorporated. In Example 1, except that 15.33 parts of a polyester resin (trade name “Byron 500”, Tg: 4 ° C., molecular weight: 23000) manufactured by Toyobo Co., Ltd. was used as the polymer resin. Similarly, the pressure-sensitive adhesive sheet of Example 2 was produced.

(Example 3)
As metal oxide particles, 23.23 parts of barium titanate particles (trade name “T-BTO-100RF”, particle diameter: 84 nm, manufactured by Toda Kogyo Co., Ltd.) were used, and the blending amount of the dispersant was 0.97 parts. In Example 1, except that 15.48 parts of a polyester resin (trade name “Byron GK330”, Tg: 16 ° C., molecular weight: 17000) manufactured by Toyobo Co., Ltd. was used as the polymer resin. Similarly, the pressure-sensitive adhesive sheet of Example 3 was produced.

Example 4
A pressure-sensitive adhesive sheet of Example 4 was produced in the same manner as in Example 1 except that a mixture containing the following components was used.
(1) Metal oxide particles: Barium titanate particles (manufactured by Toda Kogyo Co., Ltd., trade name “T-BTO-030RF”, particle diameter: 43 nm): 35.30 parts (2) Dispersant (trade name, manufactured by Avicia) “Solsperse 56000”, melting point: 55 ° C., acid value: 23 mg KOH / g): 3.07 parts (3) Polymer resin: polyester resin (trade name “Byron UR8700”, manufactured by Toyobo Co., Ltd.), Tg: −22 ° C. , Molecular weight: 40000): 6.98 parts (4) Solvent: butyl acetate: 38.37 parts (5) Solvent: methyl ethyl ketone: 16.28 parts

(Example 5)
A pressure-sensitive adhesive sheet of Example 5 was produced in the same manner as in Example 1 except that a mixture containing the following components was used.
(1) Metal oxide particles: Barium titanate particles (manufactured by Toda Kogyo Co., Ltd., trade name “T-BTO-030RF”, particle diameter: 43 nm): 20.40 parts (2) Dispersant (polyester dispersant, Avicia Product name “Solsperse 56000”, Melting point: 55 ° C., Acid value: 23 mgKOH / g): 1.77 parts (3) Polymer resin: Polyester resin (product name “Byron GK330”, manufactured by Toyobo Co., Ltd.) Tg: 16 ° C., molecular weight: 17000): 16.69 parts (4) Solvent: butyl acetate: 22.18 parts (5) Solvent: methyl ethyl ketone: 38.95 parts

(Example 6)
A pressure-sensitive adhesive sheet of Example 6 was produced in the same manner as in Example 1 except that a mixture containing the following components was used.
(1) Metal oxide particles: Barium titanate particles (manufactured by Toda Kogyo Co., Ltd., trade name “T-BTO-050RF”, particle diameter: 54 nm): 33.77 parts (2) Dispersant (manufactured by Avicia, trade name) “Solsperse 32000”, melting point: 45 ° C., acid value: 15 mg KOH / g): 2.16 parts (3) Polymer resin (trade name “Byron 500” manufactured by Toyobo Co., Ltd., Tg: 4 ° C., molecular weight: 23000) : 8.44 parts (4) Solvent: butyl acetate: 35.93 parts (5) Solvent: methyl ethyl ketone: 19.70 parts

(Example 7)
A pressure-sensitive adhesive sheet of Example 7 was produced in the same manner as in Example 1 except that a mixture containing the following components was used.
(1) Metal oxide particles: titanic acid particles (manufactured by Nippon Chemical Industry Co., Ltd., trade name “PARCERAM AKBST (9: 1)”, particle size: 43 nm): 34.71 parts (2) Dispersant (manufactured by Avicia) , Trade name “Solsperse 32000”, melting point: 45 ° C., acid value: 15 mg KOH / g): 3.02 parts (3) Polymer resin: polyester resin (trade name “Byron BX1001”, manufactured by Toyobo Co., Ltd.), Tg: −18 ° C., molecular weight: 28000): 7.36 parts (4) Solvent: butyl acetate: 37.73 parts (5) Solvent: methyl ethyl ketone: 17.18 parts

(Comparative Example 1)
A pressure-sensitive adhesive sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that a mixture containing the following components was used.
(1) Metal oxide particles: titanic acid particles (manufactured by Toda Kogyo Co., Ltd., trade name “T-BTO-030RF”, particle diameter: 43 nm): 37.74 parts (2) Dispersant (manufactured by Avicia, trade name) “Solsperse 56000”, melting point: 55 ° C., acid value: 23 mg KOH / g): 3.25 parts (3) Polymer resin: polyester resin (trade name “Byron BX1001”, manufactured by Toyobo Co., Ltd.), Tg: −18 ° C. , Molecular weight: 28000): 5.59 parts (4) solvent: butyl acetate: 40.68 parts (5) solvent: methyl ethyl ketone: 13.05 parts

(Comparative Example 2)
A pressure-sensitive adhesive sheet of Comparative Example 2 was produced in the same manner as in Example 1 except that a mixture containing the following components was used.
(1) Metal oxide particles: titanic acid-based particles (manufactured by Toda Kogyo Co., Ltd., trade name “T-BTO-030RF”, particle diameter: 43 nm): 15.11 parts (2) Dispersant (manufactured by Avicia, trade name) “Solsperse 56000”, melting point: 55 ° C., acid value: 23 mg KOH / g): 1.31 parts (3) Polymer resin: acrylic resin (butyl acrylate / 2 ethylhexyl acrylate copolymer, Tg: −40 ° C., molecular weight : 75000): 10.07 parts (4) Solvent: butyl acetate: 16.42 parts (5) Solvent: methyl ethyl ketone: 57.08 parts

(Comparative Example 3)
As metal oxide particles, 23.23 parts of titanic acid-based particles (manufactured by Toda Kogyo Co., Ltd., trade name “T-BTO-170RK”, particle size: 198 nm) were used, and the blending amount of the dispersant was 0.97 parts. The pressure-sensitive adhesive sheet of Comparative Example 3 was prepared in the same manner as in Example 1 except that the amount of the polyester resin as the polymer resin was changed to 15.48 parts.

  And about the sheet-like adhesive of each adhesive sheet obtained in the said Examples 1-7 and Comparative Examples 1-3, glass transition temperature, thickness, adhesiveness, haze, and refractive index were evaluated. The evaluation method is shown below.

(Glass-transition temperature)
The glass transition temperature (Tg) of the sheet-like pressure-sensitive adhesive was determined using a dynamic viscoelasticity measuring device (“RSA-2” manufactured by Rheometrics). Specifically, first, an adhesive sheet was installed in a dynamic viscoelasticity measuring apparatus, and the temperature change of the elastic modulus was measured. Moreover, the temperature change of the elastic modulus was similarly measured for the PET film. And the glass transition temperature of only a sheet-like adhesive was calculated | required from both measurement data. The glass transition temperature was the inflection point of the storage elastic modulus. The measurement was performed in the range of −100 to 50 ° C. at a temperature raising temperature of 4 ° C./min, with a measurement frequency of 1 Hz and a distortion rate of 0.2%. The tension was 120% in the automatic tracking mode.

(Thickness of sheet adhesive)
The thickness of the pressure-sensitive adhesive sheet was measured using a micrometer, and the thickness of the sheet-like pressure-sensitive adhesive was determined by subtracting the thickness of the PET film from the measured value.

(Adhesive)
After sticking the sheet-like adhesive side of the adhesive sheet to a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., large slide glass “S9111”), rubbing the PET film side of the adhesive sheet with a squeegee and peeling the PET film The adhesiveness of the sheet adhesive was evaluated by confirming the transfer state of the sheet adhesive to the slide glass. When the PET film was peeled off, the sheet-like pressure-sensitive adhesive adhered to the slide glass, and the sheet-like pressure-sensitive adhesive was not peeled off was judged to have good adhesion, and will be described later. In FIG. 1, “A” is used. On the other hand, it was judged that the adhesive having a part of the sheet-like adhesive peeled off was not good, and was described as “B” in Table 1 described later.

(Haze)
In the above-described evaluation of adhesiveness, haze was measured in a state where the evaluation result was “A” and the sheet-like adhesive was adhered to the slide glass. For the measurement, a haze meter “NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd. was used, and measurement was performed in accordance with Japanese Industrial Standard (JIS) K7361-1.

(Refractive index)
The refractive index of the sheet-like pressure-sensitive adhesive was measured using a refractometer “NAR-2TH” manufactured by Atago Co., Ltd. Similar to the evaluation of the adhesive property, the measurement was performed in a state where the surface of the adhesive sheet on the sheet-like adhesive side was attached to the main prism.

  Table 1 shows the content and particle diameter of metal oxide particles, the number average molecular weight and glass transition temperature (Tg) of the polymer resin, and the evaluation results for Examples 1 to 7 and Comparative Examples 1 to 3. .

  As is apparent from Table 1, the average particle diameter of the metal oxide particles is 20 to 150 nm, the content of the metal oxide particles is 50 to 80% by weight in the adhesive composition, and the number average molecular weight of the polymer resin is 10,000 to 50,000. In Examples 1 to 7 using the pressure-sensitive adhesive composition, the refractive index was as high as 1.65 or more, the haze was reduced to 20% or less, and a sheet-like pressure-sensitive adhesive suitable for production of an optical device was obtained. On the other hand, Comparative Example 1 formed using the pressure-sensitive adhesive composition in which the content of the metal oxide particles exceeded 80% by weight had a haze exceeding 20%. In Comparative Example 2 formed using an adhesive composition in which the molecular weight of the polymer resin exceeded 50000, the sheet-like adhesive became white, and the metal oxide particles were aggregated, so that there was no adhesiveness. The comparative example 3 formed using the adhesion composition in which the particle diameter of the metal oxide particles exceeded 150 nm had a haze exceeding 20%.

  INDUSTRIAL APPLICABILITY The present invention can be used as a pressure-sensitive adhesive composition and a sheet-like pressure-sensitive adhesive suitable for production of optical devices such as affixing optical elements such as LEDs, organic EL, and CCD.

Claims (7)

An adhesive composition comprising metal oxide particles, a polymer resin, and a dispersant,
The metal oxide particles are particles having at least one selected from the group consisting of titanium oxide, zirconium oxide, zinc oxide, niobium pentoxide, and titanate compounds, and having an average particle diameter of 20 to 150 nm.
The content of the metal oxide particles is 50 to 80% by weight in the adhesive composition,
The polymer resin has a number average molecular weight of 10,000 to 50,000.   The pressure-sensitive adhesive composition according to claim 1, wherein the polymer resin is at least one selected from the group consisting of polyester resins and acrylic resins.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the polymer resin has a glass transition temperature of -40 to 20 ° C.   The pressure-sensitive adhesive composition according to claim 1, wherein the dispersant has an acid value of 10 to 200 mg KOH / g.   A sheet-like pressure-sensitive adhesive formed by molding the pressure-sensitive adhesive composition according to any one of claims 1 to 4 into a sheet shape.   The sheet-like pressure-sensitive adhesive according to claim 5, wherein the glass transition temperature is −45 to 10 ° C. and the refractive index is 1.65 to 1.82. A sheet-like pressure-sensitive adhesive containing metal oxide particles, a polymer resin, and a dispersant,
The metal oxide particles are particles having at least one selected from the group consisting of titanium oxide, zirconium oxide, zinc oxide, niobium pentoxide, and titanate compounds, and having an average particle diameter of 20 to 150 nm.
The content of the metal oxide particles is 50 to 80% by weight in the sheet-like pressure-sensitive adhesive.
The glass transition temperature of the sheet-like pressure-sensitive adhesive is −45 to 10 ° C.,
The sheet-like pressure-sensitive adhesive has a refractive index of 1.65 to 1.82.