JP2009120726A - Transparent adhesive for refractive index regulating optical member, transparent adhesive layer for optics, manufacturing method of transparent adhesive for refractive index regulating optical member and manufacturing method of transparent adhesive layer for optics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent adhesive for a refractive index regulating optical member and a transparent adhesive layer for optics which both facilitate the adjustment of a refractive index, little produce the total reflection of light in the interface with a transparent base material for optics and halation, can satisfy adhesive characteristics (adhesive strength, holding strength and the like) and durability such as light resistance and resistance to heat and humidity and are free of the fear that the light transmission is adversely affected, and to provide a manufacturing method of the transparent adhesive for the refractive index regulating optical member and a manufacturing method of the transparent adhesive layer for optics. <P>SOLUTION: The transparent adhesive for the refractive index regulating optical member has metal oxide particles having a refractive index of ≥2.0 and a dispersion mean particle size of ≥1 nm and ≤20 nm dispersed in the transparent adhesive for the optical member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent adhesive for refractive index adjusting optical members, a transparent adhesive layer for optics, a transparent adhesive for refractive index adjusting optical members, and a method for producing an optical transparent adhesive layer, and more specifically, a liquid crystal display device. (LCD), organic EL display device, plasma display panel (PDP) and other image display devices and pressure sensitive adhesives such as polarizing plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion films, protective films, etc. A transparent adhesive for refractive index adjusting optical member suitable for use in preparing a layer, an optical transparent adhesive layer obtained from this transparent adhesive for refractive index adjusting optical member, and a transparent adhesive for refractive index adjusting optical member The present invention relates to a production method and a production method of this optical transparent adhesive layer.

Conventionally used for bonding image display units such as liquid crystal display devices (LCD), organic EL display devices, plasma display panels (PDP), etc., various optical members, various light sources, diffusion plates, protective films, etc., and optical disks, etc. As the pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive having an acrylic copolymer as a base polymer is used because of its good transparency and weather resistance.
The refractive index of this acrylic adhesive is almost the same as the refractive index of an acrylic copolymer as a commonly used base polymer, which is about 1.47. The refractive index of the optical member on the side on which the agent is applied is, for example, about 1.52 to 1.55 for the glass substrate and about 1.59 for the polycarbonate plate, so the refractive index of the acrylic adhesive and the optical member is There is a big difference.
For this reason, when an acrylic adhesive is used as an adhesive for an optical member, a difference in refractive index occurs at the interface between the acrylic adhesive and an optical member such as a glass substrate or a polycarbonate plate. When light is incident on the surface at a shallow angle, the light is totally reflected, which hinders effective use of light.

In order to solve such problems, various attempts have been proposed to produce an acrylic pressure-sensitive adhesive having a higher refractive index than conventional products. The acrylic adhesive with a high refractive index is roughly divided into two types, one of which is an acrylic copolymer that has a high refractive index as a base polymer of the acrylic adhesive and has a high refractive index. The other one is the refraction of the acrylic pressure-sensitive adhesive itself by adding a refractive index adjusting agent to a normal acrylic copolymer having a low refractive index. The rate is increased (Patent Documents 4 to 6).
In addition, as a technique for adding a filler to the pressure-sensitive adhesive, acrylic pressure-sensitive adhesive is used for the purpose of suppressing whitening and maintaining a highly transparent state when held for a long time under conditions such as high temperature and high humidity, immersion in warm water or boiling. A transparent adhesive film or sheet containing silica particles having a refractive index close to that of an agent has been proposed (Patent Document 7).

Furthermore, for the purpose of improving the diffusibility (paper white property), a diffusion adhesive sheet or optical laminate containing an adhesive and a filler and having a refractive index difference between the adhesive and the filler of 0.05 to 0.5 Optical members such as bodies have been proposed (Patent Documents 8 and 9).
JP 2003-535921 A JP 2002-173656 A JP 2006-188630 A JP 2003-342546 A JP 2006-342258 A JP 2007-23225 A JP 2002-348546 A JP-A-11-223712 JP 2003-90905 A

  By the way, in the conventional acrylic copolymer having a high refractive index, for example, in the case of an acrylic copolymer obtained by copolymerizing a monomer having an aromatic ring, it is the copolymerization ratio that adjusts the refractive index. Therefore, there is a trade-off relationship that the adhesive property is greatly lowered when the copolymerization ratio is increased in order to increase the refractive index. Therefore, the high refractive index and the adhesive There is a problem in that there is a limit to achieving both properties.

Therefore, in order to increase the refractive index, it is possible to use a monomer substituted with bromine as a monomer having an aromatic ring. However, non-halogenated compounds mainly for electrical and electronic applications, which have become active recently from the viewpoint of environmental measures, etc. In combination with movement, it is not preferable to use a halogen-substituted monomer.
Further, in order to adjust the refractive index of the acrylic copolymer, it is necessary to change the copolymerization ratio of the copolymer itself, and the adjustment of the refractive index is not easy and complicated.
Further, when the acrylic copolymer has an aromatic ring, it has light absorption on the short wavelength side, which is problematic in terms of effective use of light and photodegradation, and particularly for the purpose of increasing the refractive index. This problem becomes more prominent when the content of is increased.

On the other hand, in a conventional optical member containing an adhesive and a filler, the refractive index of the filler is brought close to the refractive index of the adhesive in order to maintain transparency. However, there is a problem that there is a limit to increasing the refractive index.
Further, in the conventional filler, if both the light scattering and the refractive index improving effect are achieved by increasing the filler content, there is a problem that the transmittance is lowered, and the filler content is limited.
In particular, in the adhesive layer of an optical disk, recording / reproduction with a short-wavelength laser light is evident from the demand for a large-capacity optical disk, for example, blue light using a blue laser light of about 405 nm. Is indispensable, and an increase in scattering and a decrease in transmittance cause problems in the recording / reproducing function.

  The present invention has been made in order to solve the above-described problems, and is easy to adjust the refractive index, has little total reflection and halation of light at the interface with the optical transparent substrate, and has adhesive properties ( Adhesive strength, holding power, etc.) and heat resistance, light resistance, heat resistance, moisture resistance, and other durability, and there is no risk of adversely affecting the light transmission and the transparent adhesive for optical members and optical It aims at providing the manufacturing method of the transparent adhesive layer and the transparent adhesive for refractive index adjustment optical members, and the manufacturing method of the transparent adhesive layer for optics.

  As a result of intensive studies for the purpose of adjusting the refractive index in the transparent adhesive for optical members and reducing total reflection and halation of light at the interface with the transparent substrate, the present inventors have In addition, if the metal oxide particles having a refractive index of 2.0 or more and a dispersion average particle diameter of 1 nm or more and 20 nm or less are dispersed, the refractive index can be easily adjusted, and light at the interface with the transparent substrate can be obtained. There is little total reflection and halation, and there is no possibility that the light transmission is lowered, and it is possible to satisfy adhesive properties (adhesive strength, holding power, etc.) and durability such as heat resistance, light resistance, and heat moisture resistance. The headline and the present invention were completed.

  That is, the transparent adhesive for refractive index adjusting optical member of the present invention has a refractive index of 2.0 or more and a metal oxide particle having a dispersion average particle diameter of 1 nm or more and 20 nm or less in the transparent adhesive for optical member. It is characterized by being dispersed.

The refractive index is preferably adjusted by the mixing ratio of the metal oxide particles and the transparent adhesive for optical members.
The mixing ratio of the metal oxide particles is preferably 5% by mass or more and 80% by mass or less with respect to the total amount of the metal oxide particles and the transparent adhesive for optical members.
The surface of the metal oxide particles is preferably treated with a surface modifier.
The metal oxide is preferably zirconium oxide and / or titanium oxide.
When the measurement optical path length is 10 mm, the light transmittance at each measurement wavelength in the wavelength band of 400 nm or more and 700 nm or less is preferably 80% or more.
The transparent adhesive for optical members is preferably an acrylic adhesive mainly composed of an acrylic resin.

  The transparent adhesive layer for optics of the present invention is characterized in that the transparent adhesive for refractive index adjusting optical member of the present invention is layered.

  The method for producing a transparent pressure-sensitive adhesive for refractive index adjusting optical member according to the present invention comprises a step of treating metal oxide particles having a refractive index of 2.0 or more with water or an organic solvent so that the dispersion average particle diameter is 1 nm or more and 20 nm or less. A transparent dispersion dispersed in a dispersion medium containing one or more selected from the group of organic resin monomers is mixed with a transparent adhesive for optical members.

It is preferable to adjust the refractive index by adjusting the mixing ratio of the transparent dispersion and the transparent adhesive for optical members.
The transparent dispersion has a light transmittance of 80% or more at each measurement wavelength in a wavelength band of 400 nm or more and 700 nm or less when the content of the metal oxide particles is 5 mass% and the measurement optical path length is 10 mm. It is preferable that
Preferably, the dispersion medium is water and / or an organic solvent, and the transparent dispersion is mixed with the transparent adhesive for an optical member, and then the water and / or the organic solvent is removed.
The organic resin monomer may be polymerized after the dispersion medium is an organic resin monomer and the transparent dispersion is mixed with the transparent adhesive for optical members.

  The method for producing an optical transparent adhesive layer of the present invention is characterized in that the transparent adhesive for refractive index adjusting optical member of the present invention is applied on a transparent substrate or a release material, and dried or cured.

According to the transparent adhesive for refractive index adjusting optical member of the present invention, the metal oxide particles having a refractive index of 2.0 or more and a dispersion average particle diameter of 1 nm or more and 20 nm or less are contained in the transparent adhesive for optical members. Therefore, the refractive index can be easily adjusted simply by changing the mixing ratio of the metal oxide particles and the transparent adhesive for optical members.
In addition, since the refractive index of the pressure-sensitive adhesive itself can be easily increased by increasing the mixing ratio of the metal oxide particles, even when the transparent pressure-sensitive adhesive for optical members contains a monomer having an aromatic ring. The content of the aromatic ring can be reduced, so that the light deterioration due to the aromatic ring can be reduced, and further, the total reflection and halation of light at the interface with the transparent substrate can be reduced. Also, there is no possibility that the light transmittance is lowered.
In addition, since the properties of the transparent adhesive for optical members itself that is a dispersion medium do not change, the adhesive properties (adhesive strength, holding power, etc.) and durability such as heat resistance, light resistance, and heat resistance humidity do not deteriorate.

  According to the method for producing the transparent adhesive for refractive index adjusting optical member of the present invention, the metal oxide particles having a refractive index of 2.0 or more are mixed with water so that the dispersion average particle diameter is 1 nm or more and 20 nm or less. Since the transparent dispersion dispersed in a dispersion medium containing one or more selected from the group of organic solvents and organic resin monomers is mixed with the transparent adhesive for optical members, the refractive index can be easily adjusted. It has features such as low total reflection and halation of light at the interface with the transparent base material, and low light transmission, and adhesive properties (adhesive strength, holding power, etc.), heat resistance, light resistance, and heat and humidity resistance. It is possible to easily and inexpensively produce a transparent pressure-sensitive adhesive that does not deteriorate the durability.

The best mode for carrying out the method for producing the transparent adhesive for refractive index adjusting optical member, the transparent adhesive layer for optical use, the transparent adhesive for refractive index adjusting optical member and the method for producing the optical transparent adhesive layer of the present invention will be described. To do.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Transparent adhesive for refractive index adjusting optical members"
The transparent adhesive for refractive index adjusting optical member of the present invention has a refractive index of 2.0 or more and dispersed metal oxide particles having a dispersion average particle diameter of 1 nm or more and 20 nm or less in the transparent adhesive for optical member. Transparent adhesive.

(Metal oxide particles)
Examples of the metal oxide particles include titanium oxide (2.3 to 2.7) having a refractive index of 2.0 or more, potassium titanate (2.68), barium titanate (2.3 to 2.5), and oxidation. Zirconium (2.05 to 2.4), zinc oxide (2.01 to 2.03) and the like can be mentioned. These may be used alone or in combination of two or more. Among the above metal oxide particles, preferred are titanium oxide and zirconium oxide from which particles having a small filler particle diameter can be obtained.

  Here, the reason for limiting the refractive index of the metal oxide particles to 2.0 or more is that the content of the metal oxide particles in the pressure-sensitive adhesive is minimized and the desired refractive index range, that is, the metal oxide This is because the amount of change between the refractive index of the pressure-sensitive adhesive itself before containing particles and the refractive index of the pressure-sensitive adhesive after containing particles can be adjusted in the range of 0.001 to 0.2. In particular, since the refractive index of the transparent base material used for the optical member is, for example, about 1.52 to 1.55 for a glass substrate and about 1.59 for a polycarbonate plate, the refractive index of the adhesive is 1.4 to 1.5. In the case of about 1.5, the higher the refractive index of the metal oxide particles, the lower the content, and the refractive index can be adjusted. In addition, since the characteristic of an adhesion layer will be inhibited by the fall of the transmittance | permeability, generation | occurrence | production of a crack, etc. when content of metal oxide particle increases, the one where content is small is preferable.

(Transparent adhesive for optical members)
Examples of the transparent adhesive for optical members include resins such as acrylic resins, styrene resins, epoxy resins, silicone resins, polyester resins, and polyurethane resins. These may be used alone or in combination of two or more.
In particular, acrylic resins are excellent in reliability such as water resistance, heat resistance, and light resistance, have good adhesion and transparency, and have a refractive index of a transparent substrate of an optical member such as a liquid crystal display (LCD). This is also preferable because it is easy to adjust so as to fit the side panel (transparent substrate).

  As this acrylic resin, a polymer obtained by polymerizing acrylic monomers such as acrylic acid and esters thereof, methacrylic acid and esters thereof, acrylamide and acrylonitrile, or a copolymer thereof, and further, Mention may be made of a copolymer of at least one kind and an aromatic vinyl monomer such as vinyl acetate, maleic anhydride or styrene.

As the above-mentioned polymer or copolymer, main monomers such as ethylene acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. that particularly exhibit adhesiveness, and vinyl acetate, acrylonitrile, acrylamide, styrene, methacrylate, methyl, which are cohesive components Secondary monomers such as acrylate, and methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, maleic anhydride, which provide an adhesion improvement or crosslinking starting point A polymer comprising a functional group-containing monomer such as an acid is preferred.
The polymer preferably has a Tg (glass transition point) in the range of −60 ° C. to −15 ° C. and a weight average molecular weight in the range of 200,000 to 1,000,000.

  To this acrylic resin, modified silicone oligomers, such as alkoxy-modified silicone oligomers, acrylic-modified silicone oligomers, epoxy-modified, for the purpose of preventing floating, peeling, etc. between the base material and the adhesive layer due to heat shock. Silicone oligomers, vinyl-modified silicone oligomers, mercapto-modified silicone oligomers, carboxy-modified silicone oligomers and the like may be contained.

For the purpose of adjusting the refractive index of this transparent adhesive or increasing the refractive index of the base resin, an organic compound having an aromatic ring in the molecular structure within a range that does not impair the light resistance, preferably as a monomer unit Organic compounds containing styrene may be contained.
Examples of such an organic compound include coumarone resin, styrene resin, and the like, and may have a tackifying function. In particular, a styrenic resin is preferable as a resin that does not yellow due to the color of the resin itself.

This transparent adhesive for optical members may contain a filler material such as a resin different from the base resin or an oxide in order to adjust the viscosity, mechanical properties, and the like. The refractive index of this filler material may be lower than the refractive index of the base resin, and the refractive index of the transparent adhesive containing such a filler material is lower than that of the base resin. Therefore, in order to restore the refractive index of the transparent adhesive containing the filler material, the metal oxide particles are dispersed in the transparent adhesive having a reduced refractive index, thereby returning to the same level as the base resin. It is also possible.
In this case, since the filler material is already contained, it is required to reduce the amount of the metal oxide particles to be added. Therefore, the refractive index of the metal oxide particles is preferably set to 2.0 or more.

Next, the manufacturing method of this transparent adhesive for refractive index adjustment optical members is demonstrated.
First, a transparent dispersion in which the above metal oxide particles are dispersed in a dispersion medium is prepared.
(Transparent dispersion)
Metal oxide particles having a refractive index of 2.0 or more are mixed with water or an organic solvent so that the dispersion average particle diameter is 1 nm or more and 20 nm or less, preferably 1 nm or more and 15 nm or less, more preferably 2 nm or more and 10 nm or less. And dispersing in a dispersion medium containing one or more selected from the group of organic resin monomers.

  Here, the reason why the dispersion average particle diameter is 1 nm or more and 20 nm is that when the dispersion average particle diameter is less than 1 nm, the crystallinity of the metal oxide particles becomes poor and the refractive index becomes low. When the particle size is larger than 20 nm, the dispersion of the particles is not transparent because the particles are significantly scattered. Therefore, the dispersion is not transparent when dispersed in the pressure-sensitive adhesive, and the light transmittance in the pressure-sensitive adhesive layer is reduced. In addition, the transparency of the pressure-sensitive adhesive layer and the optical member including the pressure-sensitive adhesive layer cannot be ensured.

In order to stably disperse the metal oxide particles in a dispersion medium of water, an organic solvent or an organic resin monomer, and in an adhesive, it is preferable to treat the surface of the metal oxide particles with a surface modifier.
The surface modifier is one selected from the group consisting of surfactants, silane compounds such as silane coupling agents and alkoxysilanes, siloxane compounds such as modified silicones (oil) and silicone resins, silazane compounds, and titanium coupling agents. Or 2 or more types are used suitably.

As the surfactant, an anionic surfactant, a cationic surfactant, an ionic surfactant such as an amphoteric surfactant, or a nonionic surfactant is preferably used.
Examples of the anionic surfactant include fatty acid sodium such as sodium oleate, sodium stearate and sodium laurate, fatty acid such as fatty acid potassium and sodium fatty acid ester sulfonate, and phosphoric acid such as sodium alkyl phosphate ester. And olefins such as sodium alpha olein sulfonate, alcohols such as sodium alkyl sulfate, and alkylbenzenes.
Examples of the cationic surfactant include alkyl methyl ammonium chloride, alkyl dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, and alkyl dimethyl benzyl ammonium chloride.

Examples of the zwitterionic surfactant include carboxylic acid systems such as alkylaminocarboxylates and phosphate ester systems such as phosphobetaine.
Examples of the nonionic surfactant include fatty acid-based compounds such as polyoxyethylene lanolin fatty acid ester and polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, and fatty acid alkanolamide.

  Examples of the silane compound include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane, n-butyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n- Octyltriethoxysilane, n-decyltrimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldichlorosilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, 5-hexenyltrimethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, etc. are mentioned.

  Also, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- ( (Meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, p-styryltrimethoxysilane, 3- (4-vinylphenyl) propyltrimethoxysilane 4-vinylphenylmethyltrimethoxysilane, 4-vinylphenyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane , 3-mercaptopropyl trimethoxysilane, also include 3-mercaptopropyl triethoxy silane.

Examples of the modified silicone (oil) include alkoxy-modified silicone, carboxy-modified silicone, alcohol-modified silicone, polyether-modified silicone, epoxy-modified silicone, mercapto-modified silicone, amino-modified silicone, methacrylate-modified silicone, and methylhydrogen silicone.
Examples of the silicone resin include dimethyl silicone resin and methylphenyl silicone resin.

  Examples of silazane compounds include dimethyldimethylaminosilane, dimethylaminotrimethylsilane, bis (dimethylamino) methylsilane, dimethylaminodimethylsilane, bis (methylamino) dimethylsilane, diethylaminodimethylsilane, bis (ethylamino) dimethylsilane, bis ( Dimethylamino) dimethylsilane, tris (dimethylamino) silane, 1-trimethylsilylpyrrole, 1-trimethylsilylpyrrolidine, diethylaminotrimethylsilane, methyltris (dimethylamino) silane, anilinotrimethylsilane, bis (butylamino) dimethylsilane, hexamethyldi Silazane, dianilinodiphenylsilane, 1,1,3,3-tetramethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, etc. Is mentioned.

  Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tri (dodecyl) benzenesulfonyl titanate, neopentyl (diallyl) oxy-tri (dioctyl) phosphate titanate, neopentyl (diallyl) oxy-trineo Examples include dodecanoyl titanate.

Examples of the method for treating the metal oxide particles with the surface modifier include a wet method and a dry method.
The wet method is a method of modifying the surface of metal oxide particles by mixing a surface modifier and metal oxide particles in a solvent using a homogenizer, a bead mill or the like.
The dry method is a method of modifying the surface of the metal oxide particles by putting the surface modifier and the dried metal oxide particles into a dry mixer such as a Henschel mixer and mixing them.
In any method, the surface of the metal oxide particles can be modified more efficiently by reacting while heating as necessary.

The dispersion medium must be compatible with the transparent adhesive for optical members described above. Examples of such a dispersion medium include water, an organic solvent, a liquid organic resin monomer, and a liquid organic resin oligomer. A solvent containing one or more selected from the group is preferred.
Examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, butanol, and octanol, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone. Esters, diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, benzene, toluene, Aromatic hydrocarbons such as xylene and ethylbenzene, dimethylformamide, N, N-dimethyl Amides such as acetoacetamide and N-methylpyrrolidone, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as acetylacetone and cyclohexanone, cyclic hydrocarbons such as cyclohexane, and acyclic hydrocarbons such as hexane are preferably used. One or more of these solvents can be used.

As the liquid organic resin monomer, acrylic or methacrylic monomers such as methyl acrylate and methyl methacrylate, and epoxy monomers are preferably used.
Moreover, as said liquid organic resin oligomer, a urethane acrylate oligomer, an epoxy acrylate oligomer, an acrylate oligomer, etc. are used suitably.

This transparent dispersion has a light transmittance of 80% or more at each measurement wavelength in a wavelength band of 400 nm or more and 700 nm or less when the content of the metal oxide particles is 5 mass% and the measurement optical path length is 10 mm. , Preferably 90% or more.
The light transmittance of the transparent dispersion is different between the case where titanium oxide particles are used as the metal oxide particles and the case where metal oxide particles other than titanium oxide particles, for example, zirconium oxide particles are used.

  When using metal oxide particles other than titanium oxide particles, there is no problem because the light transmittance at each measurement wavelength in the wavelength band of 400 nm or more and 700 nm or less is 80% or more, but when using titanium oxide particles, The light transmittance at each measurement wavelength in the wavelength band of 440 nm or more and 700 nm or less is 80% or more, but the light transmittance at each measurement wavelength in the wavelength band of 400 nm or more and less than 440 nm is reduced to about 70%. Care must be taken when doing so.

(Transparent adhesive for refractive index adjusting optical member)
In the transparent adhesive for refractive index adjusting optical member, first, the above transparent dispersion, the above transparent adhesive for optical member, and a curing agent as necessary are mixed and stirred.
As the mixing / stirring method, there is either one of the following methods (1) or (2).

(1) When the amount of the dispersion medium in the transparent dispersion is large Since the liquid viscosity after mixing the transparent dispersion and the transparent adhesive for optical members is low, it is easily and uniformly mixed and stirred by a simple mixing operation. It is possible. As an example of a simple mixing operation, a container containing a transparent dispersion and a transparent adhesive for optical members is shaken and stirred with a hand shake.

(2) When the amount of the dispersion medium in the transparent dispersion liquid is small Since the liquid viscosity after mixing the transparent dispersion liquid and the transparent adhesive for optical members is high, a kneader such as a lab plast mill or a three roll is used. Therefore, it is possible to mix and stir easily and uniformly.

As said hardening | curing agent, a metal chelate type, an isocyanate type, and an epoxy type crosslinking agent are used as needed, for example, and these are used 1 type or in mixture of 2 or more types.
As a result, the metal oxide particles and the transparent adhesive for optical members are uniformly dispersed, and there is no aggregation of the metal oxide particles, and a good dispersion state can be maintained for a long time. is there. Further, since it is uniformly dispersed, not only light transmission characteristics but also excellent uniformity is obtained. Therefore, if an adhesive layer is formed using this transparent adhesive for refractive index adjusting optical member, light transmission is achieved. Excellent properties and film uniformity.

Here, the refractive index of the obtained transparent adhesive for refractive index adjustment optical members can be adjusted by changing the mixing ratio of the metal oxide particles and the transparent adhesive for optical members.
The refractive index of the transparent adhesive for refractive index adjusting optical member is preferably 1.45 to 1.70, more preferably 1.5 to 1.65.
Therefore, in order to set the refractive index of the transparent adhesive for refractive index adjusting optical member within the above range, the mixing ratio of the metal oxide particles is set to the total amount of the metal oxide particles and the transparent adhesive for optical member. On the other hand, it is necessary to be 5% by mass or more and 80% by mass or less, preferably 20% by mass or more and 70% by mass or less.

  Here, the reason why the mixing ratio of the metal oxide particles is limited to 5% by mass or more and 80% by mass or less is that when the mixing ratio is less than 5% by mass, the mixing ratio is too low and the refractive index is controlled (increased refractive index). On the other hand, if the mixing ratio exceeds 80% by mass, viscosity increases and embrittlement occurs, resulting in poor application of the adhesive and deterioration of the characteristics of the adhesive (layer) itself (excessive hardness and shabbyness). This is because there is a risk of occurrence of

The transparent adhesive for refractive index adjusting optical member adjusts the mixing ratio of the metal oxide particles in the transparent dispersion and the transparent adhesive for optical member so that the adhesive strength is in the range of 100 to 2000 g / 25 mm. It is preferable.
The reason is that if the adhesive strength is less than 100 g / 25 mm, the environmental resistance is poor, and peeling may occur particularly at high temperature and high humidity. On the other hand, if the adhesive strength exceeds 200 g / 25 mm, it cannot be reattached. This is because there is a problem that the adhesive remains even if it is possible.

In addition to the above, the transparent adhesive for refractive index adjusting optical member may contain other inorganic oxide particles, resin monomers, and the like as long as the characteristics are not impaired.
Examples of inorganic oxide particles other than the metal oxide particles include metal oxide particles such as tin oxide, hafnium oxide, aluminum oxide, iron oxide, and cerium oxide, and nonmetal oxide particles such as silicon oxide.

  If the amount of the dispersion medium in the transparent dispersion is large, mixing and stirring are easy, but it takes time and effort to remove or polymerize the dispersion medium in a later step. On the other hand, if the amount of the dispersion medium in the transparent dispersion is small, the labor and time for removing or polymerizing the dispersion medium in the subsequent step are small, but mixing and stirring are difficult. Therefore, it is necessary to select a mixing / stirring method in consideration of the balance between mixing / stirring and removal of the dispersion medium or polymerization.

Next, any one of the following methods (1) and (2) is performed to obtain a transparent adhesive for refractive index adjusting optical member.
(1) When the above dispersion medium is water and / or an organic solvent, the mixture of the transparent dispersion and the transparent adhesive for optical members is heated, dried in a vacuum at room temperature, and reduced in pressure as long as the properties as an adhesive are not deteriorated. A treatment such as room temperature drying is performed to remove water and / or the organic solvent by evaporation. In this case, abrupt removal of the dispersion medium must be avoided because bubbles are generated in the pressure-sensitive adhesive, resulting in a decrease in light transmittance.

(2) When the above dispersion medium is an organic resin monomer The mixture of the transparent dispersion and the transparent adhesive for optical members is subjected to electromagnetic addition treatment such as addition of a catalyst, heat curing treatment, and ultraviolet rays to polymerize the organic resin monomer. .
In this case, the organic resin monomer and the transparent adhesive for optical members are preferably polymerized by the same method. For example, the organic resin monomer and the transparent adhesive for optical members are prepared from a resin composition made of a similar substance. It is preferable. If the polymerization method of the organic resin monomer and the transparent adhesive for optical members is different, it is difficult to polymerize both simultaneously, and the possibility of non-uniformity of the adhesive and the adhesive layer is increased due to phase separation.

Here, any of the steps of removing water and / or organic solvent and polymerizing the organic resin monomer may be performed alone, or both steps may be combined.
In these steps, various process conditions are adjusted so that the target pressure-sensitive adhesive has a viscosity and optical characteristics suitable for application. Thereby, the transparent adhesive for refractive index adjustment optical members which has the viscosity and optical characteristic suitable for application | coating are obtained.

In order to ensure sufficient transparency to visible light, the transparent adhesive for refractive index adjusting optical member has light transmission at each measurement wavelength in a wavelength band of 400 nm or more and 700 nm or less when the measurement optical path length is 10 mm. The rate is 80% or more, preferably 90% or more.
In addition, the light transmittance of the transparent adhesive for refractive index adjusting optical member is obtained when titanium oxide particles are used as metal oxide particles and when metal oxide particles other than titanium oxide particles, for example, zirconium oxide particles are used. And different.

  When using metal oxide particles other than titanium oxide particles, there is no problem because the light transmittance at each measurement wavelength in the wavelength band of 400 nm or more and 700 nm or less is 80% or more, but when using titanium oxide particles, The light transmittance at each measurement wavelength in the wavelength band of 440 nm or more and 700 nm or less is 80% or more, but the light transmittance at each measurement wavelength in the wavelength band of 400 nm or more and less than 440 nm is reduced to about 70%. Care must be taken when doing so.

"Transparent adhesive layer for optics"
This optical transparent adhesive layer can be produced by applying the above-mentioned transparent adhesive for refractive index adjusting optical member on a transparent substrate or a release material and drying or curing it.
The transparent substrate may be a substrate having transparency with respect to light in a predetermined wavelength band such as visible light or near infrared, and is thermoplastic, thermosetting, light by visible light, ultraviolet light, infrared light, or the like ( A curable resin such as an electromagnetic wave) curable resin or an electron beam curable resin by electron beam irradiation is preferably used.

Examples of such resins include acrylates such as polymethyl methacrylate (PMMA) and polycyclohexyl methacrylate, polycarbonate (PC), polystyrene (PS), polyether, polyester, polyarylate, polyacrylate, polyamide, phenol- Formaldehyde (phenolic resin), diethylene glycol bisallyl carbonate, acrylonitrile / styrene copolymer (AS resin), methyl methacrylate / styrene copolymer (MS resin), poly-4-methylpentene, norbornene polymer, polyurethane, epoxy, Examples include silicone.
On the other hand, as a release material, what is generally used as a release material for an adhesive can be used as it is.

There are no particular restrictions on the application method, and coating machines such as Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, spin coater, etc. The coating method using a tool is mentioned.
There is no restriction | limiting in particular in a drying method, Hot air drying, the heat drying by infrared irradiation, the drying by pressure reduction, etc. are mentioned. The drying condition may be room temperature (25 ° C.) to about 180 ° C., although it depends on the cured form of the transparent adhesive for refractive index adjusting optical member, the film thickness, the selected dispersion medium, and the like. Further, the thickness of the adhesive layer is not particularly limited, and may be any thickness.

In this transparent adhesive layer for optics, various conditions of application, drying or curing are adjusted so as to have hardness (flexibility) and adhesiveness suitable as an adhesive layer.
If various conditions such as viscosity suitable for coating are controlled in the manufacturing process of the transparent adhesive for refractive index adjusting optical member, the hardness (flexibility) and adhesiveness of the adhesive layer are confirmed in this process. The degree is acceptable.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
(Preparation of zirconium oxide transparent dispersion)
A zirconium oxide precursor slurry was prepared by adding dilute ammonia water in which 344 g of 28% ammonia water was dissolved in 20 L of pure water to a zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water while stirring. .
Next, an aqueous sodium sulfate solution in which 300 g of sodium sulfate was dissolved in 5 L of pure water was added to this slurry while stirring to prepare a mixture. The amount of sodium sulfate added at this time was 30% by weight relative to the zirconium oxide equivalent value of zirconium ions in the zirconium salt solution.

Next, this mixture was dried at 130 ° C. for 24 hours in the air using a dryer to produce a solid.
Next, this solid material was pulverized with an automatic mortar and then baked in the air at 500 ° C. for 1 hour using an electric furnace.
Next, the fired product is put into pure water, stirred to form a slurry, washed using a centrifuge, and after sufficiently removing the added sodium sulfate, dried in a dryer, Zirconium oxide particles were prepared.

  Next, 74 g of toluene as a dispersion medium and 6 g of methoxy-modified silicone (made by Shin-Etsu Chemical Co., Ltd., refractive index 1.5) as a surface modifier are added to 20 g of the zirconium oxide particles, and then heated to 60 ° C. using an ultrasonic homogenizer. Surface modification and dispersion treatment were carried out while heating to prepare a zirconium oxide transparent dispersion containing 20% by mass of zirconium oxide particles.

(Preparation of transparent adhesive and transparent adhesive layer)
A 10 g acrylic resin pressure-sensitive adhesive having a refractive index of 1.45 and a weight average molecular weight of 500,000 is mixed and stirred with 0.15 g of an isocyanate curing agent and 28.5 g of the above-described zirconium oxide transparent dispersion, and transparent containing zirconium oxide particles. An adhesive was prepared.
Next, an amorphous cycloolefin polymer (COP) plate having a refractive index of 1.53 is prepared as a transparent substrate, and the thickness after drying the above-mentioned transparent adhesive with a roll coater is 60 μm on this COP plate. So that it was coated. Thereafter, the solvent was removed by drying in the atmosphere at 50 ° C. for 30 minutes to produce a transparent adhesive layer containing zirconium oxide particles.

"Example 2"
(Preparation of zirconium oxide transparent dispersion)
According to Example 1, a zirconium oxide transparent dispersion was prepared.

(Preparation of transparent adhesive and transparent adhesive layer)
A transparent pressure-sensitive adhesive and a transparent pressure-sensitive adhesive layer were prepared in the same manner as in Example 1 except that 55.0 g of the zirconium oxide transparent dispersion was used and the transparent substrate was a polycarbonate (PC) plate having a refractive index of 1.59.

"Example 3"
(Preparation of titanium dioxide transparent dispersion)
To a titanium salt solution in which 2089 g of titanium tetrachloride was dissolved in 15 L of pure water, diluted ammonia water in which 1000 g of 28% ammonia water was dissolved in 35 L of pure water was added with stirring to prepare a titanium oxide precursor slurry.
Next, the titanium oxide precursor slurry was dried using a freeze dryer to produce a solid.
Next, this solid material was pulverized with an automatic mortar and then baked at 500 ° C. for 1 hour in the air using an electric furnace to produce titanium oxide particles.

  Next, 74 g of toluene as a dispersion medium and 6 g of methoxy-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd.) as a surface modifier are added to 20 g of the titanium oxide particles, and then the surface is modified while heating to 60 ° C. using an ultrasonic homogenizer. And the dispersion process was performed and the titanium oxide transparent dispersion liquid containing 20 mass% of titanium oxide particles was produced.

(Preparation of transparent adhesive and transparent adhesive layer)
A transparent adhesive and a transparent adhesive layer containing titanium oxide particles were produced in the same manner as in Example 1 except that 28.5 g of the zirconium oxide transparent dispersion was changed to 14.3 g of the titanium oxide transparent dispersion.

Example 4
(Preparation of titanium dioxide transparent dispersion)
A titanium oxide transparent dispersion was prepared according to Example 3.

(Preparation of transparent adhesive and transparent adhesive layer)
Zirconium oxide transparent dispersion 28.5 g was changed to titanium oxide transparent dispersion 26.1 g, and amorphous cycloolefin polymer (COP) plate having a refractive index of 1.53 was used as a polycarbonate (PC) plate having a refractive index of 1.59. Produced a transparent adhesive and a transparent adhesive layer according to Example 1.

"Comparative Example 1"
(Preparation of transparent adhesive and transparent adhesive layer)
A transparent adhesive was prepared by mixing and stirring 0.15 g of an isocyanate curing agent to 10 g of an acrylic resin adhesive having a refractive index of 1.45 and a weight average molecular weight of 500,000.
Subsequently, this transparent adhesive was coated on a polycarbonate (PC) plate having a refractive index of 1.59 so that the thickness after drying was 60 μm by a roll coater. Then, it was made to dry at 50 degreeC in air | atmosphere for 30 minutes, the solvent was removed, and the transparent adhesion layer was produced.

"Comparative Example 2"
(Preparation of zirconium oxide dispersion)
1.6 g of phosphate ester surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 78.4 g of toluene are added to 20 g of commercially available zirconium oxide particles (Daiichi Kagaku Kagaku Kogyo Co., Ltd., refractive index 2.10). The surface modification / dispersion treatment was carried out using, to prepare a zirconium oxide dispersion containing 20% by mass of zirconium oxide particles.

(Preparation of adhesive and adhesive layer)
A pressure-sensitive adhesive and a pressure-sensitive adhesive layer were prepared in the same manner as in Example 1 except that 28.5 g of the zirconium oxide transparent dispersion was changed to 32.4 g of the zirconium oxide dispersion.

“Comparative Example 3”
(Preparation of titanium oxide dispersion)
To 20 g of commercially available titanium oxide particles (manufactured by Ishihara Sangyo Co., Ltd.), 1.6 g of phosphate ester surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 78.4 g of toluene are added, and surface modification / dispersion treatment is performed using a bead mill. And a titanium oxide dispersion containing 20% by mass of titanium oxide particles was prepared.

(Preparation of adhesive and adhesive layer)
A pressure-sensitive adhesive and a pressure-sensitive adhesive layer were prepared in the same manner as in Example 1 except that 28.5 g of the zirconium oxide transparent dispersion was changed to 15.2 g of the titanium oxide dispersion.

“Comparative Example 4”
(Preparation of zirconium oxide transparent dispersion)
According to Example 1, a zirconium oxide transparent dispersion containing 20% by mass of zirconium oxide particles was prepared.

(Preparation of transparent adhesive and transparent adhesive layer)
A styrene monomer was added to an acrylic resin adhesive having a refractive index of 1.45 and a weight average molecular weight of 500,000 to produce an acrylic adhesive having a refractive index of 1.50.
Next, 0.15 g of an isocyanate curing agent and 28.5 g of the zirconium oxide transparent dispersion were mixed and stirred in 10 g of this acrylic pressure-sensitive adhesive to produce a transparent pressure-sensitive adhesive containing zirconium oxide particles.

"Evaluation"
About the transparent dispersion of Examples 1-4 and Comparative Example 4, the transparent adhesive and the transparent adhesive layer, the dispersion of Comparative Examples 1-3, the adhesive and the adhesive layer, the refractive index of the metal oxide particles, the dispersion of the dispersion Each evaluation item of the average particle diameter, the transmittance of the dispersion, the refractive index of the pressure-sensitive adhesive layer, the refractive index of the transparent substrate, the transmittance of the pressure-sensitive adhesive layer, and the light resistance deterioration was evaluated using the following methods.

(1) Refractive index of metal oxide particles (measurement of refractive index of metal oxide filler)
Measured with a multi-incidence angle ellipsometer (manufactured by JAWoollam).
(2) Dispersion average particle diameter of dispersion liquid Using a dynamic light scattering type particle size distribution measuring apparatus (manufactured by Malvern), the particle diameter standard was measured as a volume standard as a data analysis condition.
(3) Permeability of dispersion liquid By adding a dispersion medium having the same composition as the dispersion medium of this dispersion liquid to the dispersion liquid, the content of metal oxide particles in the dispersion liquid is adjusted to 5% by mass. The adjusted dispersion liquid is injected into a cell having an optical path length of 10 mm, and the transmittance of each wavelength from 400 nm to 700 nm is measured with an integrating sphere using a spectrophotometer (manufactured by JASCO Corporation). Was measured. In addition, what injected only said dispersion medium into said cell was made into control | contrast (blank).

(4) Refractive index of adhesive layer After drying the solvent, it was measured with an Abbe refractometer (manufactured by Atago Co., Ltd.).
Here, the case where the difference in refractive index from the transparent substrate is less than 0.01 is “◯”, and the case where the difference is 0.01 or more is “x”.
(5) Refractive index of transparent substrate It measured with the Abbe refractometer (made by Atago Co., Ltd.).
(6) Transmittance of adhesive layer The transmittance of the adhesive layer obtained by coating on a transparent substrate and drying was measured using a spectrophotometer (manufactured by JASCO Corporation) with an integrating sphere using a spectral wavelength of 400 nm to 700 nm. The transmittance of each wavelength was measured. Here, a transparent base material of the same material not coated with an adhesive was used as a control (blank), a transmittance of 80% or more was indicated by “◯”, and a transmittance of less than 80% was indicated by “X”.

(7) Light resistance deterioration The pressure-sensitive adhesive layer coated on the transparent substrate was irradiated for 40 hours using a metalling weather meter (0.4 kw / m ² ), and then applied to a spectrophotometer (manufactured by JASCO Corporation). Then, the transmittance of the adhesive layer at a spectral wavelength of 400 nm was measured with an integrating sphere, and the obtained transmittance was compared with the transmittance before irradiation. Here, a drop in transmittance of less than 10% is indicated by “◯”, and a drop of 10% or more is indicated by “x”.
These evaluation results are shown in Table 1.

According to Table 1, in Examples 1 to 4, the transparent dispersion had a transmittance of 90 or more and a dispersion average particle size of 8 nm, which was excellent as a transparent dispersion.
Moreover, the refractive index difference with the transparent base material of a transparent adhesive layer was 0.01 or less, the transmittance | permeability was 85% or more, and the light-resistant deterioration was also excellent.
On the other hand, the pressure-sensitive adhesive layer of Comparative Example 1 was very inferior with a refractive index difference of 0.14 from the transparent substrate.
In Comparative Examples 1 to 3, since the dispersion was cloudy, the resulting adhesive layer was also slightly turbid and the transmittance was as low as 71% or less.
In Comparative Example 4, the transmittance of the transparent dispersion, the difference in refractive index of the transparent adhesive layer, and the transmittance were inferior to those of Examples 1 to 4, but the light resistance was inferior.

  The transparent adhesive for refractive index adjusting optical member of the present invention has a refractive index of 2.0 or more and dispersed metal oxide particles having a dispersion average particle diameter of 1 nm or more and 20 nm or less in the transparent adhesive for optical member. As a result, the refractive index can be easily adjusted simply by changing the mixing ratio of the metal oxide particles and the transparent adhesive for optical members, and further, light degradation is reduced, and light at the interface with the transparent substrate is reduced. Can reduce the total reflection and halation of light, and maintain the light transmittance. Therefore, it is necessary to adjust the refractive index of the adhesive, such as a liquid crystal display (LCD), an organic EL display, plasma. Not to mention adhesive layers such as polarizing plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion films, protective films, etc. used in image display devices such as display panels (PDP) and optical disks And, also in various industrial fields other than this, the effect is large.

Claims (14)

  A metal oxide particle having a refractive index of 2.0 or more and a dispersion average particle diameter of 1 nm or more and 20 nm or less is dispersed in a transparent adhesive for optical members, for a refractive index-adjusting optical member Transparent adhesive.   2. The transparent adhesive for refractive index adjusting optical member according to claim 1, wherein a refractive index is adjusted by a mixing ratio of the metal oxide particles and the transparent adhesive for optical member.   The mixing ratio of the metal oxide particles is 5% by mass or more and 80% by mass or less based on the total amount of the metal oxide particles and the transparent adhesive for optical members. Transparent adhesive for refractive index adjusting optical member.   4. The transparent adhesive for refractive index adjusting optical member according to claim 1, wherein the surface of the metal oxide particles is treated with a surface modifier.   The transparent adhesive for refractive index adjusting optical members according to any one of claims 1 to 4, wherein the metal oxide is zirconium oxide and / or titanium oxide.   The refractive index according to any one of claims 1 to 5, wherein when the measurement optical path length is 10 mm, the light transmittance at each measurement wavelength in the wavelength band of 400 nm or more and 700 nm or less is 80% or more. Transparent adhesive for adjusting optical members.   The transparent adhesive for refractive index adjusting optical members according to any one of claims 1 to 6, wherein the transparent adhesive for optical members is an acrylic adhesive mainly composed of an acrylic resin.   A transparent adhesive layer for optics, wherein the transparent adhesive for refractive index adjusting optical member according to any one of claims 1 to 7 is layered.   Metal oxide particles having a refractive index of 2.0 or more are selected from one or more selected from the group of water, organic solvent, and organic resin monomer so that the dispersion average particle diameter is 1 nm or more and 20 nm or less. A method for producing a transparent adhesive for refractive index adjusting optical member, comprising mixing a transparent dispersion liquid dispersed in a dispersion medium containing the transparent adhesive for optical member.   The method for producing a transparent adhesive for refractive index adjusting optical member according to claim 9, wherein the refractive index is adjusted by adjusting a mixing ratio of the transparent dispersion and the transparent adhesive for optical member.   The transparent dispersion has a light transmittance of 80% or more at each measurement wavelength in a wavelength band of 400 nm or more and 700 nm or less when the content of the metal oxide particles is 5 mass% and the measurement optical path length is 10 mm. The method for producing a transparent adhesive for refractive index adjusting optical member according to claim 9 or 10, wherein: The dispersion medium is water and / or an organic solvent,
12. The transparent adhesive for refractive index adjusting optical member according to claim 9, wherein the water and / or the organic solvent is removed after mixing the transparent dispersion with the transparent adhesive for optical member. Manufacturing method. The dispersion medium is an organic resin monomer,
12. The method for producing a transparent adhesive for refractive index adjusting optical member according to claim 9, wherein the organic resin monomer is polymerized after mixing the transparent dispersion with the transparent adhesive for optical member. .   A transparent adhesive layer for optical use, wherein the transparent adhesive for refractive index adjusting optical member according to any one of claims 1 to 7 is applied on a transparent substrate or a release material, and dried or cured. Production method.