JP7449117B2 - adhesive composition - Google Patents

Description

The present invention relates to a technique for dispersing metal oxide particles in an adhesive composition.

Adhesive compositions in which metal oxide particles are dispersed are known (for example, Patent Documents 1 and 2). These Patent Documents 1 and 2 describe an image display section, a light source section, a recording section, a polarizing plate, a phase difference, etc. in an image display device or optical disk such as a liquid crystal display device (LCD), an organic EL display device, or a plasma display panel (PDP). An adhesive with metal oxide particles dispersed therein is used as a high refractive index transparent adhesive when bonding plates, optical compensation films, brightness enhancement films, light diffusion films, protective films, etc. as appropriate.

JP2014-172960A Japanese Patent Application Publication No. 2014-159557

However, when metal oxide particles are dispersed in a sticky (meth)acrylic polymer, agglomeration occurs, probably because the sticky (meth)acrylic polymer forms a structure that is ionically crosslinked by the metal oxide. However, it was difficult to stably disperse the metal oxide particles.
Therefore, the problem to be solved by the present invention is to stably disperse metal oxide particles in an adhesive (meth)acrylic polymer.

The configuration of the present invention that can solve the above problems is as follows.
[1] An adhesive composition containing an adhesive (meth)acrylic polymer, metal oxide particles, and a non-aromatic polymer having a weight average molecular weight of 50,000 or less.
[2] The non-aromatic polymer is an amino group, an amide group, a carboxyl group, a phosphoric acid group, a phosphonic acid group, a hydrolyzable alkoxysilyl group, an isocyanate group, a hydroxyl group, a thiol group, an epoxy group, and an oxazoline group. The adhesive composition according to the above [1], which is a polymer of the monomer (A) having one or more selected functional groups.
[3] The adhesive according to [2] above, wherein the non-aromatic polymer contains, as a copolymerized unit, a low Tg (meth)acrylic acid ester (B) unit whose homopolymer has a glass transition temperature of 0° C. or lower. agent composition.
[4] The adhesive (meth)acrylic polymer contains a low Tg (meth)acrylic acid ester (D) unit,
The mass proportion (PB) of the low Tg (meth)acrylic acid ester (B) units in the non-aromatic polymer is the same as that of the low Tg (meth)acrylic acid ester (D) units in the adhesive (meth)acrylic polymer. The pressure-sensitive adhesive composition according to any one of [1] to [3] above, which is 0.3 to 3 times the mass percentage (PD).
[5] The adhesive (meth)acrylic polymer is a copolymer of the low Tg (meth)acrylic ester (D) and a polar group-containing monomer (C), and the polar group is a carboxyl group. The adhesive composition according to any one of [1] to [4] above, wherein the proportion of units composed of group-containing monomers is 1% by mass or less based on 100% by mass of the adhesive (meth)acrylic polymer.
[6] The adhesive composition according to any one of [1] to [5] above, wherein the metal oxide particles have a refractive index of 2.02 or more.
[7] The adhesive composition according to any one of [1] to [6] above, which contains 20% by mass or more of the metal oxide particles.

According to the present invention, metal oxide particles can be stably dispersed in a sticky (meth)acrylic polymer.

The adhesive composition of the present invention comprises an adhesive (meth)acrylic polymer, metal oxide particles, and a non-aromatic polymer having a weight average molecular weight of 50,000 or less (hereinafter simply referred to as "non-aromatic polymer"). ). Since the non-aromatic polymer functions as a polymer dispersant, metal oxide particles can be stably dispersed in the adhesive (meth)acrylic polymer.

(1) Non-aromatic polymer (polymer dispersant)
A non-aromatic polymer refers to a polymer containing a monomer having no aromatic ring (also referred to as a non-aromatic monomer) as an essential polymer constituent unit. The non-aromatic polymer is a polymer dispersant that acts on metal oxide particles to improve their dispersibility. Since the molecular weight is 50,000 or less, the polymer itself can be prevented from agglomerating even if it is attracted to the metal oxide particles by interaction, and the metal oxide particles can be highly dispersed. Furthermore, since it is a non-aromatic polymer, it has a high affinity with adhesive (meth)acrylic polymers, and metal oxide particles can be stably dispersed in adhesive (meth)acrylic polymers. Furthermore, since it is a non-aromatic polymer, it also has excellent optical properties.

The weight average molecular weight of the non-aromatic polymer is, for example, 10,000 or less, preferably 8,000 or less, more preferably 6,000 or less. The smaller the weight average molecular weight, the better the dispersion stability tends to be. The lower limit of the weight average molecular weight is, for example, 1000 or more, preferably 2000 or more, and more preferably 3000 or more.

The non-aromatic monomer constituting the non-aromatic polymer includes a monomer (A) having a metal oxide adsorption site, a low Tg (meth)acrylic ester (B), etc. The polymer is preferably a copolymer of a monomer (A) having adsorption sites for these metal oxides and a low Tg (meth)acrylic ester (B). By having metal oxide adsorption sites and low Tg (meth)acrylic acid ester units, the dispersibility of metal oxide particles can be further improved.

The monomer (A) having a metal oxide adsorption site includes an amino group, an amide group, a carboxyl group, a phosphoric acid group, a phosphonic acid group, a hydrolyzable alkoxysilyl group, an isocyanate group, a hydroxyl group, a thiol group, an epoxy group, and a monomer (A) having one or more functional groups (hereinafter sometimes referred to as adsorption groups) selected from oxazoline groups. The hydrolyzable alkoxysilyl group is preferably a silyl group having a total of 1 to 3 methoxy or ethoxy groups bonded to silicon atoms.

Examples of the monomer (A) having an amino group include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate. Examples of the monomer (A) having an amide group include N-vinylpyrrolidone, (meth)acryloylmorpholine, (meth)acrylamide, and N-methylolacrylamide. Examples of the monomer (A) having a carboxyl group include (meth)acrylic acid, itaconic acid, crotonic acid, maleic anhydride, maleic acid, 2-acryloyloxyethylsuccinic acid, 2-acryloyloxyethyl phthalic acid, 2- Examples include acryloyloxyethylhexahydrophthalic acid, and (meth)acrylic acid is preferred. Examples of the monomer (A) having a phosphoric acid group include 2-hydroxyethyl acryloyl phosphate. Examples of the monomer (A) having a phosphonic acid group include [3-(acryloyloxy)propyl]phosphonic acid. Examples of the monomer (A) having a hydrolyzable alkoxysilyl group include vinylalkoxysilanes such as vinyltrimethoxysilane and vinyltriethoxysilane, dimethylvinylmethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxysilane. Examples include (meth)acryloxy C _1-4 alkyl alkoxysilanes such as propylmethyldimethoxysilane. Examples of the monomer (A) having an isocyanate group include 2-methacryloyloxyethyl isocyanate. Examples of the monomer (A) having a hydroxyl group include (meth)acrylic acid hydroxy C _1-10 alkyl esters such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. Examples of the monomer (A) having a thiol group include 3-mercaptopropyltrimethoxysilane. Examples of the monomer (A) having an epoxy group include glycidyl (meth)acrylate. Examples of the monomer (A) having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl- Examples include 2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.
The monomer (A) having adsorption sites for metal oxides may be used alone or in combination.

Monomers (A) having adsorption sites for metal oxides include carboxy groups, phosphoric acid groups, phosphonic acid groups, hydrolyzable alkoxysilyl groups, amino groups, amide groups, isocyanate groups, hydroxyl groups, thiol groups, epoxy groups, Monomers (A) having one or more adsorption groups selected from A monomer (A) having the following is more preferred.

The proportion of units derived from the monomer (A) having metal oxide adsorption sites in 100% by mass of the non-aromatic polymer is, for example, 1 to 30% by mass, preferably 2 to 20% by mass, more preferably 3% by mass. ~15% by mass.

The low Tg (meth)acrylic ester (B) means a (meth)acrylic ester (preferably a (meth)acrylic acid alkyl ester) whose homopolymer glass transition temperature is 0° C. or lower. Examples of the low Tg (meth)acrylic ester (B) include the following. Note that the value in parentheses indicates the glass transition temperature of the homopolymer.
Methacrylic acid C _8-20 alkyl esters such as n-butyl methacrylate (-20°C);
Ethyl acrylate (-24°C), n-butyl acrylate (-54°C), 2-methoxyethyl acrylate (-50°C), n-octyl acrylate (-80°C), 2-ethylhexyl acrylate (-70°C), iso Acrylic acid C _2-20 alkyl esters such as octyl acrylate (-58°C).

The above-mentioned low Tg (meth)acrylic acid ester (B) may be used alone or in combination. As the low Tg (meth)acrylic ester (B), a C _2-20 alkyl acrylate is preferred, and a combination of two or more C _2-20 alkyl acrylates is preferred. When two or more types of acrylic acid C _2-20 alkyl esters are combined, acrylic acid C _3-20 alkyl ester (A) in which the alkyl group is branched and acrylic acid C _3-20 in which the alkyl group is linear It is preferable to combine C _3-20 acrylic acid alkyl ester (A) in which the alkyl group is branched and C _3-20 acrylic acid alkyl ester (B) in which the alkyl group is linear. It is more preferable that the mass ratio (A/B) of

The glass transition temperature of the low Tg (meth)acrylic ester (B) is preferably -150 to -10°C, more preferably -120 to -30°C, even more preferably -90 to -40°C. It is also preferable that the low Tg (meth)acrylic ester (B) and the low Tg (meth)acrylic ester (D) described below are the same.

The proportion (PB) of units derived from the low Tg (meth)acrylic ester (B) in 100% by mass of the non-aromatic polymer is, for example, 70 to 99% by mass, preferably 80 to 98% by mass, more preferably is 85 to 97% by mass.

In the non-aromatic polymer, a monomer (A) having a metal oxide adsorption site and a monomer (P) other than the low Tg (meth)acrylic acid ester (B) may be copolymerized. The proportion of units derived from the monomer (A) having a metal oxide adsorption site and the low Tg (meth)acrylic acid ester (B) in 100% by mass of the non-aromatic polymer is, for example, 71 to 100% by mass, It is preferably 80 to 100% by weight, more preferably 90 to 100% by weight.

The monomer (P) may be a non-aromatic monomer or an aromatic monomer, for example, methyl (meth)acrylate, ethyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl. High Tg (meth)acrylic acid esters with homopolymer glass transition temperatures higher than 0°C such as (meth)acrylate and isobornyl (meth)acrylate; Aromatic monomers such as styrene and α-methylstyrene; Vinyl acetate, propion Vinyl esters such as acid vinyl; nitrile group-containing monomers such as (meth)acrylonitrile; and the like.

The proportion of units derived from non-aromatic monomers in 100% by mass of the non-aromatic polymer is, for example, 71 to 100% by mass, preferably 80 to 100% by mass, and more preferably 90 to 100% by mass.

The amount of the non-aromatic polymer is, for example, 10 to 300 parts by weight, preferably 20 to 200 parts by weight, and more preferably 30 to 100 parts by weight, based on 100 parts by weight of the metal oxide particles.
The amount of the non-aromatic polymer is, for example, 15 to 50 parts by weight, preferably 18 to 40 parts by weight, and more preferably 20 to 30 parts by weight, based on 100 parts by weight of the adhesive composition.

(2) Adhesive (meth)acrylic polymer Adhesive (meth)acrylic polymer is a single or copolymer of low Tg (meth)acrylic acid ester (D) whose homopolymer glass transition temperature is 0°C or lower. It is. Specific examples and preferred ranges of the low Tg (meth)acrylic ester (D) are the same as those for the above-mentioned low Tg (meth)acrylic ester (B).

The proportion (PD) of units derived from low Tg (meth)acrylic acid ester (D) in 100% by mass of the adhesive (meth)acrylic polymer is, for example, 50 to 100% by mass, preferably 60 to 95% by mass. , more preferably 70 to 90% by mass.

Also, the mass proportion (PD) of low Tg (meth)acrylic acid ester (D) units in the adhesive (meth)acrylic polymer and the low Tg (meth)acrylic acid ester (B) units in the non-aromatic polymer. It is preferable that the mass percentage (PB) of is close to that of PB. If these mass ratios are close, the affinity between the adhesive (meth)acrylic polymer and the non-aromatic polymer will be good. The mass proportion (PB) of low Tg (meth)acrylic acid ester (B) units in the non-aromatic polymer is the mass proportion (PB) of low Tg (meth)acrylic acid ester (D) units in the adhesive (meth)acrylic polymer. For example, it is 0.3 to 3 times, preferably 0.5 to 2 times, more preferably 0.7 to 1.5 times the mass percentage (PD).

The adhesive (meth)acrylic polymer is preferably a copolymer of the low Tg (meth)acrylic acid ester (D) and a polar group-containing monomer (C). By copolymerizing the polar group-containing monomer (C), the strength of the adhesive (meth)acrylic polymer can be increased.

The polar group-containing monomer (C) includes an amino group, an amide group, a carboxyl group, a phosphoric acid group, a phosphonic acid group, a hydrolyzable alkoxysilyl group, an isocyanate group, a hydroxyl group, a thiol group, an epoxy group, and an oxazoline group. Examples include monomers (C) having one or more selected polar groups. Specific examples of the polar group-containing monomer (C) are the same as those for the monomer (A) having a metal oxide adsorption site described above, and may be used alone or in combination.

The polar group-containing monomer (C) is preferably a monomer (C) having one or more polar groups selected from an amino group, an amide group, a carboxyl group, a phosphoric acid group, a phosphonic acid group, a hydroxyl group, and a thiol group. More preferred is a monomer (C) having one or more polar groups selected from an amino group, an amide group, a hydroxyl group, and a thiol group.

Proportion of units derived from the polar group-containing monomer (C) in 100% by mass of the adhesive (meth)acrylic polymer (particularly the proportion of units derived from the polar group-containing monomer (C) whose polar group is other than carboxyl group) is, for example, 1 to 50% by weight, preferably 5 to 40% by weight, and more preferably 10 to 30% by weight. The proportion of units derived from a polar group-containing monomer whose polar group is a carboxyl group may be 1% by mass or less, 0.5% by mass or less, or 0% by mass. By using a polar group-containing monomer whose polar group is other than a carboxyl group, the non-gelling property of the pressure-sensitive adhesive composition can be further improved.

The weight average molecular weight of the adhesive (meth)acrylic polymer is, for example, 200,000 or more, preferably 250,000 or more, more preferably 300,000 or more, and for example, 1 million or less, preferably 800,000 or less, more preferably It is less than 600,000.

The amount of the adhesive (meth)acrylic polymer is, for example, 10 to 500 parts by weight, preferably 20 to 300 parts by weight, and more preferably 30 to 200 parts by weight, based on 100 parts by weight of the metal oxide particles.
The amount of the adhesive (meth)acrylic polymer is, for example, 10 to 500 parts by weight, preferably 30 to 300 parts by weight, and more preferably 50 to 200 parts by weight, based on 100 parts by weight of the non-aromatic polymer.

The adhesive (meth)acrylic polymer may be copolymerized with a polar group-containing monomer (C) and a monomer (Q) other than the low Tg (meth)acrylic acid ester (D). The proportion of units derived from the polar group-containing monomer (C) and the low Tg (meth)acrylic acid ester (D) in 100% by mass of the adhesive (meth)acrylic polymer is, for example, 71 to 100% by mass, preferably The amount is 80 to 100% by weight, preferably 90 to 100% by weight. Examples of the monomer (Q) include the same monomers (P) as described above.

(3) Metal oxide particles Examples of metals constituting metal oxide particles include Ti, Al, Zr, In, Zn, Sn, La, Y, Ce, Mg, Ba, Ca, etc. From the viewpoint of increasing the refractive index of the particles, at least one selected from the group consisting of Ti, Al, Zr, Zn, Sn, and Ce is preferable, Ti, Zn, and Zr are more preferable, and Ti and Zr are even more preferable. Zr is particularly preferred. The metal oxide may be an oxide of a single metal, a solid solution of two or more types of oxides, or a composite oxide. Examples of single metal oxides include aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), and tin oxide. (SnO ₂ ), lanthanum oxide (La ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), cerium oxide (CeO ₂ ), and magnesium oxide (MgO). Examples of solid solutions of two or more oxides include indium tin oxide (ITO) and antimony tin oxide (ATO). Examples of the composite oxide include barium titanate (BaTiO ₃ ), perovskite (CaTiO ₃ ), and spinel (MgAl ₂ O ₄ ).
In particular, metal oxide particles (including composite oxide particles) are preferably particles with a refractive index of 2.02 or more, such as titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), zinc oxide (ZnO), etc. . Particles with a high refractive index have a large deterioration in appearance when their dispersibility is slightly inferior, so if such high refractive index particles can be blended at a high concentration while maintaining a good appearance, it would be a great advantage.

The amount of metal oxide particles is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, and, for example, 60% by mass or less, preferably It is 50% by mass or less. In particular, in the present invention, metal oxide particles having a refractive index of 2.02 or more can be blended at a high concentration, for example, 20% by mass or more, preferably 25% by mass or more, more preferably 30% by mass. Above, it can be particularly preferably 35% by mass or more.

The number average particle diameter of the particles is, for example, 50 nm or less, preferably 30 nm or less, more preferably 20 nm or less, and, for example, 1 nm or more, preferably 2 nm or more, more preferably 5 nm or more. When the number average particle diameter of the metal oxide particles is within the above range, the transparency of the adhesive composition will be higher.

The ratio (dv/dn) of the volume average particle diameter (dv) and the number average particle diameter (dn) of the metal oxide particles is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less, Preferably it is 1 or more.

The metal oxide particles may be granular, ellipsoidal, cubic, rectangular, pyramidal, needle-like, columnar, rod-like, cylindrical, scale-like, plate-like, flaky, irregularly shaped, etc., and can be dispersed. From the viewpoint of properties and the like, it is preferable that the shape is spherical, granular, or columnar.

The metal oxide particles are preferably surface-treated with at least one of a carboxylic acid compound, a silane coupling agent, and an organic phosphorus compound, and are preferably surface-treated with at least an organic phosphorus compound. When the metal oxide particles have a surface treatment layer, the dispersibility in the adhesive composition can be further improved.
Examples of carboxylic acid compounds include (meth)acrylic acids (for example, (meth)acryloxy C _1-6 alkyl carboxylic acids such as acrylic acid, methacrylic acid, and 3-acryloxypropionic acid); C _3-9 aliphatic dicarboxylic acids (meth)acryloxy of C _1-6 alkyl alcohol half esters (e.g. 2-acryloxyethylsuccinic acid, 2-methacryloxyethylsuccinic acid, etc.), (meth)acryloxy of C _5-10 alicyclic dicarboxylic acid Half esters with C _1-6 alkyl alcohols (e.g. 2-acryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl hexahydrophthalic acid, etc.), (meth)acryloxy C ₁ of C _8-14 aromatic dicarboxylic acids Carboxylic acids with ester groups such as half esters with _-6 alkyl alcohols (e.g. 2-acryloxyethylphthalic acid, 2-methacryloxyethylphthalic acid, etc.); butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid , nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, stearic acid and other linear carboxylic acids having 4 to 20 carbon atoms; pivalic acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,2 -dimethylvaleric acid, 2,2-diethylbutyric acid, 3,3-diethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 3-methylhexanoic acid, 3-ethylhexanoic acid, 2-methylheptanoic acid, 4 - Branched carboxylic acids having 5 to 20 carbon atoms such as methyloctanoic acid and neodecanoic acid; cyclic carboxylic acids such as naphthenic acid and cyclohexanedicarboxylic acid; and the like. Preferred are half esters of C _3-9 aliphatic dicarboxylic acids with (meth)acryloxyC _1-6 alkyl alcohols, branched carboxylic acids having 5 to 20 carbon atoms, and the like. These carboxylic acid compounds may be used alone or in combination of two or more.
The amount of the carboxylic acid compound treated layer on the surface of the metal oxide particles (coating amount) is, for example, 0 to 40% by mass, preferably 1 to 35% by mass, more preferably 5 to 35% by mass, based on 100% by mass of the entire coated particles. It is 30% by mass.

As the silane coupling agent, alkoxysilane compounds having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl) -Alkoxysilane compounds having an amino group such as -3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyltrimethoxysilane; 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyl Alkoxysilane compounds having a (meth)acryloyl group such as trimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane; 3-mercaptopropyltrimethoxy Alkoxysilane compounds having a mercapto group such as silane, 3-mercaptopropyltriethoxysilane; 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Examples include alkoxysilane compounds having an epoxy group such as triethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. These silane coupling agents may be used alone or in combination of two or more.
The amount (coating amount) of the silane coupling agent treated layer on the surface of the metal oxide particles is, for example, 0 to 30% by mass, preferably 0.1 to 20% by mass, more preferably is 1 to 15% by mass.

Examples of organic phosphorus compounds include phosphoric acid esters, phosphorous acid esters, and phosphonic acid esters to which an alkyl group having 1 to 30 carbon atoms is bonded; phosphoric acid esters, phosphorous acid esters, phosphonic acid esters having a polyether chain, etc. Among them, phosphoric acid esters, phosphorous acid esters, phosphonic acid esters, and the like having polyether chains are preferred.
Examples of phosphoric acid esters, phosphorous acid esters, and phosphonic acid esters to which an alkyl group having 1 to 30 carbon atoms are bonded include compounds represented by the following formulas.

Examples of the phosphoric acid ester, phosphorous acid ester, and phosphonic acid ester having a polyether chain include compounds represented by the following formulas.

In the formula, a is 1 or 2, preferably 1. p11, p12, and p15 are each independently 4 to 15, and the total of p11, p12, and p15 is 1 to 50, preferably 1 to 30. r1 and r12 are 1 to 20.

Examples of the organic phosphorus compounds include Nucor 1000-FCP (manufactured by Nippon Nyukazai Co., Ltd.), Antox EHD-400 (manufactured by Nippon Nyukazai Co., Ltd.), Phoslex series (manufactured by SC Organic Chemical Co., Ltd.), and Light Acrylate P-1A (manufactured by Kyoeisha Co., Ltd.). ), Light Acrylate P-1M (manufactured by Kyoeisha Kagaku), TEGO (registered trademark) Dispers 651, 655, 656 (manufactured by Evonik), DISPERBYK-110, 111, 180 (manufactured by BYK Chemie Japan), KAYAMERPM- 2. KAYAMER PM-21 (manufactured by Nippon Kayaku Co., Ltd.) etc. can be used.
The above organic phosphorus compounds may be used alone or in combination of two or more.
The amount of organic phosphorus compound on the surface of the metal oxide particles (coating amount) is, for example, 0 to 30% by mass, preferably 0.1 to 15% by mass, more preferably 0.1% by mass, based on 100% by mass of the entire coated particles. It is 5 to 10% by mass.

(4) Crosslinking agent The adhesive composition may contain a crosslinking agent as necessary. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy compounds, melamine compounds, metal chelate compounds, aziridine compounds, mercapto compounds, oxazoline compounds, etc., preferably metal chelate compounds, isocyanate crosslinking agents, etc., and more preferably It is an isocyanate-based crosslinking agent. Metal chelate compounds and isocyanate crosslinking agents, particularly isocyanate crosslinking agents, have high reactivity with hydroxyl groups and are excellent as crosslinking agents.

Examples of isocyanate-based crosslinking agents include aromatic diisocyanates such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate, and polymethylene polyphenylisocyanate; butane diisocyanate, pentane diisocyanate, and hexamethylene diisocyanate ( Aliphatic diisocyanates such as HDI), trimethylhexamethylene diisocyanate, lysine diisocyanate, and butylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,4-cyclohexane diisocyanate, cyclopentylene diisocyanate, and isophorone diisocyanate. ; adduct polyisocyanate compounds; bullet polyisocyanate compounds; polyisocyanate compounds having an isocyanurate ring, and the like.

As the adduct polyisocyanate compound, for example, "Sumidur L" (manufactured by Sumitomo Bayer Urethane Co., Ltd.); "Coronate L", "Coronate HL" (both manufactured by Nippon Polyurethane Co., Ltd.), etc. can be used. As the bullet polyisocyanate compound, for example, "Sumidur N" (manufactured by Sumitomo Bayer Urethane) can be used. Examples of the polyisocyanate compound having an isocyanurate ring include "Desmodur IL" and "Desmodur HL" (both manufactured by Bayer AG); "Coronate EH" and "Coronate HX" (both manufactured in Japan) (manufactured by Polyurethane Industries, Ltd.); "Takenate D110N" and "Takenate D120N" (both manufactured by Mitsui Chemicals).

The crosslinking agent is, for example, 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the adhesive (meth)acrylic polymer. It is.

(5) Diluent The adhesive composition may also contain a diluent, if necessary. The diluent is preferably an organic solvent, such as an aliphatic hydrocarbon compound such as n-hexane or n-heptane; cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, or decahydronaphthalene. , bicycloheptane, tricyclodecane, hexahydroindene cyclohexane, cyclooctane, α-pinene, terpinolene, limonene, and other alicyclic hydrocarbon compounds; toluene, xylene, benzene, solvent naphtha, and other aromatic hydrocarbon compounds; ethyl acetate , ester compounds such as butyl acetate; ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.
The amount of the organic solvent is, for example, 0 to 1000 parts by weight, preferably 50 to 700 parts by weight, and more preferably 100 to 500 parts by weight, based on 100 parts by weight of the adhesive (meth)acrylic polymer.

(6) Other components The adhesive composition may contain other components as necessary. Other ingredients include crosslinking accelerators (acid catalysts such as para-toluenesulfonic acid, phosphoric acid, hydrochloric acid, ammonium chloride, etc.), tackifiers ((polymerization) rosin-based tackifiers, (polymerization) rosin ester-based tackifiers) agent, terpene tackifier, terpene phenol tackifier, coumaron tackifier, coumaron indene tackifier, styrene resin tackifier, xylene resin tackifier, phenolic resin tackifier, (petroleum resin tackifiers, etc.), fillers, pigments, anti-aging agents, ultraviolet absorbers, ultraviolet stabilizers, etc.

Since the metal oxide particles are highly dispersed in the adhesive composition of the present invention, the transmittance, haze, holding power, adhesive strength, etc. are reduced compared to adhesive compositions that do not contain metal oxide particles. Virtually invisible. For example, the transmittance measured by the method of Examples described below is, for example, 80% or more (preferably 85 to 95%). The haze is, for example, 5% or less (preferably 1 to 4%). The holding force (SUS) is less than 0.5 mm (preferably less than 0.2 mm). Adhesive strength (SUS) is 3N/25mm or more (preferably 5N/25mm or more). Adhesive force (glass) is 3N/25mm or more (preferably 5N/25mm or more).

The adhesive composition can be used in an image display section, a light source section, a recording section, a polarizing plate, and a retardation plate in image display devices such as liquid crystal display devices (LCDs), organic EL display devices, and plasma display panels (PDPs), and optical discs. It can be used as an adhesive when appropriately laminating optical compensation films, brightness enhancement films, light diffusion films, protective films, etc.
Further, the adhesive composition can be processed into various product forms as required, such as adhesive sheets, adhesive labels, adhesive tapes, double-sided tapes, etc.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the Examples below, and modifications may be made as appropriate within the scope of the spirit of the preceding and following. Of course, other implementations are also possible, and all of them are included within the technical scope of the present invention.

Note that "parts" hereinafter mean parts by mass unless otherwise specified.
Furthermore, the molecular weights of the polymers obtained in the following examples were measured in the following manner.
(1) Molecular weight measurement The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (ratio of weight average molecular weight to number average molecular weight, Mw/Mn) of the polymer are measured using gel permeation chromatography (GPC). Calculated using standard polystyrene conversion method. For GPC, a measuring device (product number: HLC-8220GPC, manufactured by Tosoh Corporation) was used. Then, the values measured under the following measurement conditions were converted using standard polystyrene (manufactured by Tosoh Corporation), and the obtained converted values were used as the weight average molecular weight (Mw) and number average molecular weight (Mn) of the measured polymer. . Furthermore, the molecular weight distribution (Mw/Mn) was calculated from the ratio of the weight average molecular weight and the number average molecular weight.
(Measurement condition)
Separation column: manufactured by Tosoh Corporation, product number: TSKgel Super HZM-H
Extraction solvent: Tetrahydrofuran Flow rate: 0.35mL/min
Injection volume: 10μL/time Sample concentration: 0.2% by weight

Various properties of the adhesive compositions obtained in the following examples were evaluated as follows.
(2) Dispersion stability The adhesive composition was visually observed and evaluated based on the following criteria.
○: None of cloudiness, sedimentation, or gelation is observed. ×: Any of cloudiness, sedimentation, or gelation is observed.

(3) Refractive index The refractive index was measured under the following conditions.
Equipment: ATAGO multi-wavelength Abbe refractometer DR-M4 type Interference filter: Wavelength 589 (D) nm
Measurement temperature: 20℃

(4) Transmittance Transmittance was measured using a turbidity meter (NDH7000, manufactured by Nippon Denshoku Kogyo Co., Ltd.).

(5) Haze Haze was measured using a turbidity meter (NDH7000, manufactured by Nippon Denshoku Industries).

(6) Adhesive sheet properties Polyisocyanate ethyl acetate solution (solid concentration: approx. 55% by mass, NCO content: approx. 9.5; trade name: “Coronate L-55E” (Tosoh Co., Ltd.) per 100 parts of the adhesive composition company's product) at the mass ratio (based on solid content) shown in Table 1 and stirred uniformly, the mixture was applied onto a 25 μm thick PET film using an applicator, and then heated at a temperature of 80°C for 3 minutes. It was dried. The thickness of the adhesive layer was 25 μm. Release paper (manufactured by Toyobo Co., Ltd., trade name: E-7002) was laminated on the top surface of this adhesive layer. A pressure sensitive adhesive sheet having one side as an adhesive surface was obtained by aging for a period of time.

(6.1) Holding power A test tape was prepared by cutting the adhesive sheet obtained above into a rectangle with a length of 50 mm and a width of 25 mm. After peeling off the release paper from the obtained test tape, the test tape was placed on a stainless steel plate with a polished surface at a temperature of 23°C so that the adhesive area was 25 mm x 25 mm, and the mass was 2 kg from the top of the test tape. The test tape was pressed against the stainless steel plate by making one reciprocation with a rubber roller. After leaving the crimped test piece at a temperature of 80°C for 20 minutes, attach a 1 kg weight to the end of the test tape and suspend it, and leave it at that temperature for 1440 minutes to determine the time required for the test tape to peel off. Or, the length of positional shift of the test tape after 1440 minutes had elapsed from the start of the test was measured.

(6.2) Adhesive strength (SUS)
A test tape was prepared by cutting the adhesive sheet into a rectangle with a length of 50 mm and a width of 25 mm. The release paper was peeled off from the obtained test tape, the test tape was placed on a stainless steel plate with a polished surface, and a roll having a mass of 2 kg was made to reciprocate once on the adherend. After the test piece was left standing at a temperature of 23° C. for 25 minutes, the peeling force was measured when peeling at a peeling angle of 180° and a peeling rate of 300 mm/min, and the adhesive force to the stainless steel plate was measured.
(6.3) Adhesive strength (glass)
The procedure was the same as in (6.2) Adhesive strength (SUS) except that the adherend was changed from a stainless steel plate to glass.

Production example 1 (metal oxide)
Pure water (268 parts) was mixed with a zirconium 2-ethylhexanoate mineral spirit solution (782 parts, zirconium 2-ethylhexanoate content 44% by mass, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.). The obtained liquid mixture was charged into an autoclave equipped with a stirrer, and the atmosphere inside the autoclave was replaced with nitrogen gas. Thereafter, the mixed solution was heated to 180° C. and kept at this temperature for 16 hours (autoclave internal pressure was 0.94 MPa) to react, thereby producing zirconium oxide particles. Subsequently, the mixed solution after the reaction was taken out, and the precipitate accumulated at the bottom was filtered off, washed with acetone, and then dried. When the dried precipitate (100 parts) was dispersed in toluene (700 parts), a cloudy white solution was obtained. Next, as a purification step, the mixture was filtered again using quantitative filter paper (manufactured by Advantech Toyo Co., Ltd., No. 5C) to remove coarse particles in the precipitate. Furthermore, white zirconium oxide nanoparticles (metal oxide 1) were recovered by concentrating the filtrate under reduced pressure to remove toluene.

Measurement of number average particle size using an electron microscope The number average particle size of the zirconium oxide nanoparticles was measured by observing with an ultra-high resolution field emission scanning electron microscope (manufactured by Hitachi High-Technologies, S-4800). The zirconium oxide nanoparticles were observed at a magnification of 150,000 times, and the length in the longitudinal direction of each particle was measured for 100 arbitrary particles, and the average value was taken as the number average particle diameter. The average particle diameter (number average particle diameter) of the zirconium oxide nanoparticles obtained by measurement using an electron microscope was 12 nm.

Production example 2 (non-aromatic polymer)
155 parts of toluene, 62.0 parts of 2-ethylhexyl acrylate (2EHA), 30.0 parts of butyl acrylate (BA), and acrylic were placed in a reaction vessel equipped with a cooling tube, a nitrogen gas introduction tube, a thermometer, a dropping funnel, and a stirrer. After adding 8.0 parts of acid and 5.0 parts of normal dodecyl mercaptan (NDM), 0.5 part of an azo polymerization initiator (manufactured by Nippon Hydrazine Industries Co., Ltd., trade name: ABN-E) was added, and a nitrogen gas atmosphere was added. A non-aromatic polymer (polymer dispersant 1) having a solid content of 40% by mass and a weight average molecular weight of 4,000 was obtained by reacting the mixture at 85°C for 6 hours.

Production example 3 (adhesive (meth)acrylic polymer)
In a reaction vessel equipped with a cooling tube, a nitrogen gas introduction tube, a thermometer, a dropping funnel, and a stirrer, 100 parts of ethyl acetate, 58.9 parts of 2-ethylhexyl acrylate (2EHA), 20.5 parts of butyl acrylate (BA), After adding 20.0 parts of N-vinylpyrrolidone and 0.6 parts of 2-hydroxyethyl methacrylate (HEMA), 0.2 parts of an organic peroxide polymerization initiator (manufactured by NOF Corporation, trade name: Perbutyl O) was added. A sticky (meth)acrylic polymer (adhesive polymer 1) having a solid content of 50% and a weight average molecular weight of 400,000 was obtained by reacting for 8 hours at 80° C. in a nitrogen gas atmosphere.

Example 1
After dissolving the zirconium oxide nanoparticles (metal oxide 1) obtained in Production Example 1 in toluene to make a 70% by mass toluene solution, the solid content mass ratio was 1 metal oxide/1 polymer dispersant/1 adhesive polymer. By mixing the polymer dispersant 1 obtained in Production Example 2 and the adhesive polymer 1 obtained in Production Example 3 in a ratio of =50/30/50 and stirring the mixture uniformly, an adhesive composition was prepared. was prepared.

Example 2
Except that the mixing ratio of polymer dispersant 1 and adhesive polymer 1 in Example 1 was set to metal oxide 1/polymer dispersant 1/adhesive polymer 1 = 50/30/30 (solid content mass ratio). The same procedure as in Example 1 was carried out.

Comparative example 1
Adhesive Polymer 1 was used as an adhesive composition.

The characteristics of the adhesive compositions obtained in Examples and Comparative Examples were investigated.
The results are shown in Table 1.

Claims (7)

Contains an adhesive (meth)acrylic polymer, metal oxide particles, and a non-aromatic polymer with a weight average molecular weight of 50,000 or less,
The adhesive (meth)acrylic polymer is a copolymer of a low Tg (meth)acrylic acid ester (D) and a polar group-containing monomer (C) whose homopolymer glass transition temperature is 0 ° C. or lower,
In 100% by mass of the adhesive (meth)acrylic polymer, the proportion of units composed of a polar group-containing monomer whose polar group is a carboxyl group is 1% by mass or less,
The non-aromatic polymer is a copolymer of a monomer (A) having a carboxyl group and a low Tg (meth)acrylic acid ester (B) whose homopolymer glass transition temperature is 0° C. or lower,
An adhesive composition in which the proportion of units derived from the monomer (A) having a carboxyl group is 1 to 30% by mass in 100% by mass of the non-aromatic polymer. The mass proportion (PB) of the low Tg (meth)acrylic acid ester (B) units in the non-aromatic polymer is the same as that of the low Tg (meth)acrylic acid ester (D) units in the adhesive (meth)acrylic polymer. The adhesive composition according to claim 1 , which is 0.3 to 3 times the mass percentage (PD). The low Tg (meth)acrylic ester (B) is a C _3-20 alkyl acrylate (a) in which the alkyl group is branched, and a C _3-20 alkyl acrylate in which the alkyl group is linear. ester (b);
Claim 1 or 2 , wherein the mass ratio ((a)/(b)) of the acrylic acid C _3-20 alkyl ester (a) and the acrylic acid C _3-20 alkyl ester (b) is more than 1.0. The adhesive composition described in . The low Tg (meth)acrylic ester (D) includes C _3-20 alkyl acrylate (a) in which the alkyl group is branched, and C _3-20 alkyl acrylate in which the alkyl group is linear. (b) and
Claims 1 to 3 , wherein the mass ratio ((a)/(b)) of the acrylic acid C _3-20 alkyl ester (a) and the acrylic acid C _3-20 alkyl ester (b) is more than 1.0. The pressure-sensitive adhesive composition according to any one of the above. The adhesive according to any one of claims 1 to 4 , wherein the proportion of units derived from the polar group-containing monomer (C) in 100% by mass of the adhesive (meth)acrylic polymer is 1 to 50% by mass. agent composition. The adhesive composition according to any one of claims 1 to 5 , wherein the metal oxide particles have a refractive index of 2.02 or more. The adhesive composition according to any one of claims 1 to 6 , wherein the metal oxide particles are contained in an amount of 20% by mass or more based on 100% by mass of the adhesive composition.