JP2009210974A - Near-infrared absorbing film and optical filter for plasma display panel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a near-infrared absorbing film of which the layer (hereafter referred to as an adhesive layer) prepared by applying an adhesive has near-infrared absorbing capacity, which is excellent in dry heat resistance and wet heat resistance, and which retains excellent optical characteristics, and to provide an optical filter for a plasma display panel (PDP) using it. <P>SOLUTION: The optical filter for the PDP is obtained by using the near-infrared absorbing film produced by disposing the adhesive layer formed of the adhesive containing an acrylic resin, a diimmonium-based pigment expressed by formula (1), and an ionic liquid on a surface of a transparent substrate film as an indispensable component, and laminating another functional film thereon. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a near-infrared absorbing film that absorbs a wide range of wavelengths in the near-infrared region, has excellent heat resistance and moist heat resistance, and has an adhesive function, and an optical filter for a plasma display panel (hereinafter referred to as PDP) using the same. .

  The principle of PDP is that a voltage is applied to a rare gas (neon, xenon, etc.) enclosed in a cell sandwiched between two plate-like glasses, and ultraviolet light emitted from the rare gas in a plasma state is applied to the cell wall. The visible light necessary for the image is generated by hitting the light, but at the same time as the visible light, near-infrared rays, electromagnetic waves harmful to the human body, neon gas, and the orange light near the wavelength of 595 nm which lowers the color purity of the red light (hereinafter referred to as the following) Neon light) is also emitted together, so visible light necessary for video is transmitted, but harmful electromagnetic waves such as near infrared rays need to be shielded, and various optical filters are necessary for this purpose. It is said. (See Patent Document 1)

  Among the light emitted by rare gases in plasma state, near infrared rays in particular cause malfunctions in remote controllers for electrical devices that use near infrared rays and communication devices that use near infrared rays such as personal computers and cordless phones. In order to prevent this, it is essential to install an optical filter having a function of shielding near infrared rays on the front surface of the PDP.

  As a filter for shielding near infrared rays, a method using an optical filter having a near infrared absorbing film as a constituent element has been proposed. Here, the near-infrared absorbing film is made of, for example, a binder resin containing a near-infrared absorbing pigment (for example, a polyester-based resin, a polymethyl methacrylate-based resin, a polycarbonate-based resin, or a polystyrene-based resin), or a transparent material such as polyethylene terephthalate (PET). It is created by coating on a substrate film. The near-infrared absorbing dye to be used has a maximum absorption wavelength at 800 to 1100 nm, for example, diimonium dye, cyanine dye, indocyanine dye, polymethine dye, squarylium dye, phthalocyanine dye, dithiol complex dye Alternatively, azo dyes are widely used. Among these, diimonium dyes having a relatively wide absorption wavelength range in the near infrared region are frequently used alone or in combination with other near infrared absorbing dyes based on this.

Generally, as described above, the optical filter having near-infrared absorption ability is a method in which a separately prepared near-infrared absorbing film is bonded to a transparent substrate film such as a film or glass through a newly provided adhesive layer. However, in such a method, the manufacturing process becomes long and the production efficiency decreases. If the near-infrared absorbing dye can be contained in the pressure-sensitive adhesive layer, near-infrared absorbing performance can be imparted between any layers constituting the optical filter, so that the efficiency of optical filter production can be expected to improve. For example, Patent Document 1 describes an infrared absorption film in which an acrylic pressure-sensitive adhesive contains a near-infrared absorbing dye and a pressure-sensitive adhesive layer is provided with near-infrared absorption ability. However, when a near-infrared absorbing dye typified by a diimonium-based dye is included in the pressure-sensitive adhesive layer, there is a problem that the heat stability and heat-and-moisture resistance are deteriorated. Various studies on stabilization methods have been conducted. For example, Patent Document 2 proposes to use a silicon-based adhesive as the adhesive, but the silicon-based adhesive is difficult to handle, and in particular, it is difficult to form an adhesive layer. Patent Document 3 proposes a pressure-sensitive adhesive made of an acrylic acid polymer having a specific structure, but sufficient stabilization of the near-infrared absorbing dye is not obtained. Patent Document 4 proposes a near-infrared absorbing film in which a near-infrared absorbing layer containing a near-infrared absorbing dye and an ionic liquid is laminated on a transparent base material using an acrylic resin as a transparent binder resin. The description about the near-infrared absorption film which contained the infrared rays absorption pigment | dye in the adhesion layer itself is not seen.
Japanese Patent No. 3621322 JP 2005-62506 A JP 2006-257223 A JP 2007-206259 A

  A near-infrared absorbing film in which a layer provided by applying an adhesive (hereinafter also referred to simply as an adhesive layer) has near-infrared absorbing ability, is excellent in heat resistance and heat-and-moisture resistance, and maintains good optical properties. It is an object of the present invention to produce and provide an optical filter for PDP using the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by including a near-infrared absorbing dye in the pressure-sensitive adhesive layer and also by including an ionic liquid, thereby completing the present invention. I let you.

（式（１）中、Ｒ₁乃至Ｒ₈はそれぞれ独立に水素原子又は置換基を有していてもよい脂肪族炭化水素残基を、Ｘ^-は一価の陰イオンをそれぞれ表す。）
（４）イオン液体を構成するアニオンがビス（トリフルオロメタンスルホニル）イミド酸イオンである（１）乃至（３）のいずれか一項に記載の近赤外線吸収フィルム、
（５）イオン液体を構成するカチオンがヘテロ芳香族基を有するイオンである（１）乃至（４）のいずれか一項に記載の近赤外線吸収フィルム、
（６）粘着剤が架橋剤を含有する粘着剤である（１）乃至（５）のいずれか一項に記載の近赤外線吸収フィルム、
（７）（１）乃至（６）のいずれか一項に記載の近赤外線吸収フィルム、電磁波遮蔽機能を有するフィルム及び減反射機能を有するフィルムを必須の構成要素とするプラズマディスプレイパネル用光学フィルタ、
（８）アクリル系樹脂、近赤外線吸収色素及びイオン液体を含有する近赤外線吸収性粘着剤、
に関する。 That is, the present invention is (1) a near-infrared absorbing film in which an adhesive layer formed of an adhesive containing an acrylic resin, a near-infrared-absorbing dye and an ionic liquid is provided on one surface of a transparent substrate film,
(2) The near-infrared absorbing film according to (1), wherein the glass transition temperature (Tg) of the acrylic resin is in the range of −80 to 0 ° C.,
(3) The near-infrared absorbing film according to (1) or (2), wherein the near-infrared absorbing dye is a diimonium-based dye represented by the following formula (1):

(In Formula (1), R _{1 to} R ₈ each independently represents an aliphatic hydrocarbon residue which may have a hydrogen atom or a substituent, and X ⁻ represents a monovalent anion.)
(4) The near-infrared absorbing film according to any one of (1) to (3), wherein the anion constituting the ionic liquid is a bis (trifluoromethanesulfonyl) imidate ion,
(5) The near-infrared absorbing film according to any one of (1) to (4), wherein the cation constituting the ionic liquid is an ion having a heteroaromatic group,
(6) The near-infrared absorbing film according to any one of (1) to (5), wherein the pressure-sensitive adhesive is a pressure-sensitive adhesive containing a crosslinking agent,
(7) An optical filter for a plasma display panel comprising the near-infrared absorbing film according to any one of (1) to (6), a film having an electromagnetic wave shielding function, and a film having an anti-reflection function as essential constituent elements,
(8) A near-infrared absorbing pressure-sensitive adhesive containing an acrylic resin, a near-infrared absorbing dye, and an ionic liquid,
About.

  The near-infrared absorbing film of the present invention has good near-infrared absorbing ability, excellent durability such as dry heat resistance and moist heat resistance, and also has a function as an adhesive layer, so that it can be easily combined with other functional films. It is very easy to prepare an optical filter for PDP and the like.

Hereinafter, the present invention will be described in detail.
The near-infrared absorbing film of the present invention is provided with an adhesive layer on one surface of a transparent substrate film, and the adhesive that forms the adhesive layer is an acrylic resin, which is represented by the formula (1). It is a functional film that contains a near-infrared absorbing dye such as a system dye and an ionic liquid, and has both a function as an adhesive layer and a near-infrared absorbing function.

  In the present invention, as the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive containing an acrylic resin as an essential component is used because it is excellent in transparency, adhesiveness, heat resistance and the like. Here, as the acrylic resin, a (meth) acrylic acid alkyl ester having no functional group as a main component is copolymerized with a (meth) acrylic acid monomer having a functional group or an unsaturated polybasic acid. Those are preferably used. Here, the (meth) acrylic acid-based monomer having a functional group is utilized as a reaction point in the case of using a cross-linking agent, and improves cohesiveness and heat resistance by controlling the glass transition temperature of the copolymer by cross-linking. Improvements can be expected. In the weight of all monomers constituting the copolymer of (meth) acrylic acid alkyl ester having no functional group and (meth) acrylic acid type monomer or unsaturated polybasic acid having a functional group other than (meth) acrylic acid alkyl ester The proportion of the amount is generally 0.1 to 10% by weight, more preferably 2 to 6% by weight.

  Specific examples of the alkyl acrylate having no functional group include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and isosoacrylate. -Butyl, tert-butyl acrylate, iso-amyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, The alkyl group has 1 to 12 carbon atoms such as octyl (meth) acrylate, phenethyl acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate or dodecyl (meth) acrylate. Examples include acrylic acid alkyl esters or methacrylic acid alkyl esters. But it may be used in combination of two or more as necessary.

Specific examples of the (meth) acrylic acid monomer having a functional group include monomers having a carboxyl group such as acrylic acid or methacrylic acid, 2-hydroxylethyl (meth) acrylate or hydroxybutyl (meth) acrylate. (Meth) acrylic acid ester having a hydroxy group, (meth) acrylamide, (meth) acrylamide, morpholylacrylamide, N, N-dimethylaminoethyl acrylate or N-tert-butylaminoethyl acrylate (meth) acrylic acid ester And (meth) acrylic acid ester having an epoxy group such as glycidyl (meth) acrylate.
Specific examples of the unsaturated polybasic acid include monomers having a carboxyl group such as itaconic acid, maleic acid, crotonic acid or fumaric acid.

  In this invention, a crosslinking process can be performed by mix | blending a crosslinking agent with acrylic resin. Specific examples of crosslinking agents that can be used include aromatic diisocyanates such as hexamethylene diisocyanate or trimethylene propane adduct of hexamethylene diisocyanate, aromatics such as tolylene diisocyanate, xylylene diisocyanate, or trimethylol propane adduct of tolylene diisocyanate. Polyisocyanates such as aliphatic diisocyanates, melamine compounds such as trimethylol melamine, polyamines such as hexamethylenediamine or triethyldiamine, epoxy compounds such as polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether or bisphenol A epichlorohydrin, aluminum acetylacetone Such as metal chelate compounds, metal salts such as aluminum chloride, etc. It is. The compounding quantity is 0.005-5 weight part normally per 100 weight part of acrylic resins, Preferably it is 0.01-3 weight part.

  The above acrylic resin adhesives are excellent in adhesive strength and cohesive strength, and have no unsaturated bond in the polymer, so they are highly stable against light and oxygen, and have a high degree of freedom in selecting the type and molecular weight of the monomer. For this reason, it is suitable for the purpose of the present invention and has a relatively high molecular weight (degree of polymerization) in order to maintain adhesion to the transparent substrate film, that is, the weight average molecular weight (Mw) of the main polymer is 60. It is preferably about 10,000 to 2,000,000, more preferably about 800,000 to 1,800,000.

  The glass transition temperature (Tg) of the acrylic resin is −80 to 0 ° C., and −60 to −20 ° C. is a preferable range. It is said that the acrylic resin usually used for coating has a Tg of 85 ° C. or higher and cannot be used at 80 ° C. or lower.

  As the pressure-sensitive adhesive in the present invention, in addition to the above-mentioned components, a polyester resin, a polyamide resin, a polyurethane resin, a polyolefin resin, a polycarbonate resin, a natural or synthetic rubber resin, a silicon resin, or the like is appropriately selected as necessary. Can be blended. In order to improve the durability of the pressure-sensitive adhesive layer containing a near-infrared absorbing dye, an antioxidant, an ultraviolet absorber, and the like can be added. Examples of the antioxidant include phenol-based, amine-based, hindered phenol-based , Hindered amine-based, sulfur-based, phosphoric acid-based, phosphorous acid-based or metal complex-based ones, and examples of the UV absorber include benzophenone-based or benzotriazole-based ones. Furthermore, a color tone correction dye, a neon light absorption dye, a leveling agent, an antistatic agent, and the like having a maximum absorption wavelength in the range of 300 to 800 nm may be contained as long as the effects of the present invention are not impaired.

  As a near-infrared absorbing dye used in the present invention, those having a maximum absorption wavelength at 800 to 1100 nm and excellent compatibility with acrylic resins can be used without limitation. Diimonium dyes, nitroso compounds and their metal salts, cyanine dyes, squarylium dyes, thiol nickel complex compounds, phthalocyanine dyes, naphthalocyanine dyes, triallylmethane dyes, naphthoquinone dyes, anthraquinone dyes, etc. Is mentioned. Of these near-infrared absorbing dyes, diimonium dyes are preferred.

In the present invention, a diimonium dye that is particularly preferably used is a diimonium dye represented by the formula (1).
In the diimonium dye represented by the formula (1), R _{1 to} R ₈ each independently represents a hydrogen atom or an aliphatic hydrocarbon group which may have a substituent. An aliphatic hydrocarbon group means a group obtained by removing one hydrogen atom from a saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon. Examples of the carbon number include 1 to 36, preferably 1 to 20 carbon atoms, particularly preferably 1 to 6 carbon atoms.

  Specific examples of the saturated linear and branched aliphatic hydrocarbon groups having no substituent include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, and an iso-butyl group. , Sec-butyl group, tert-butyl group, n-pentyl group, iso-pentyl group, tert-pentyl group, n-hexyl group, iso-hexyl group, n-octyl group, iso-octyl group, decyl group or neopentyl group Etc.

  The aliphatic hydrocarbon group is an aryl group (eg, phenyl group, benzyl group, phenylethyl group, etc.), halogen atom (eg, fluorine, chlorine, bromine), hydroxy group, alkoxy group (eg, methoxy group, ethoxy group, Propoxy group, etc.), alkoxyalkyl group (eg, methoxyethyl group, ethoxyethyl group), aryloxy group, acyloxy group (eg, acetyloxy group, butyryloxy group, benzoyloxy group), N, N-dialkylamino group, cyano A substituent such as a group, a sulfoalkyl group (eg, sulfomethyl group), a carboxyl group or an alkoxycarbonyl group (eg, methoxycarbonyl group).

  Preferable specific examples of the aliphatic hydrocarbon group having a substituent include a cyanomethyl group, 2-cyanoethyl group, 2- or 3-cyanopropyl group, 2-, 3- or 4-cyanobutyl group, 2-, 3-, Cyano-substituted alkyl group such as 4- or 5-cyanopentyl group, methoxyethyl group, ethoxyethyl group, 3-methoxypropyl group, 3-ethoxypropyl group, 4-methoxybutyl group, 4-ethoxybutyl group, 5-methoxy Alkoxy-substituted alkyl group such as pentyl group or 5-ethoxypentyl group, monofluoromethyl group, trifluoromethyl group, trifluoroethyl group, tetrafluoroethyl group, pentafluoroethyl group, heptafluoropropyl group, perfluorobutyl group, perfluoro A pentyl group, a perfluorohexyl group or a perfluorooctyl group Examples thereof include a nitrogen-substituted alkyl group.

  Specific examples of unsaturated linear and branched aliphatic hydrocarbon groups include vinyl, allyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl, isohexenyl or octenyl. These groups may have a substituent such as a halogen atom, a hydroxy group, an alkoxy group or a carboxy group.

  Specific examples of the cyclic aliphatic hydrocarbon group include a cyclopentyl group, a cyclohexyl group, and a cyclohexenyl group, which may have the above substituents.

In the present invention, at least one of R _{1 to} R ₈ is a linear or branched C1-C6 alkyl group, and at least one of R _{1 to} R ₈ is a linear C1-C4 alkyl group. preferably not more, also, as at least one of R ₁ to R ₈ is a branched alkyl group, especially a are more preferably an alkyl group which is branched by R ₁ to R ₈ are all terminated. Examples of the alkyl group in which R _{1 to} R ₈ are all branched at the terminal include an iso-propyl group, an iso-butyl group, an iso-amyl group, an iso-hexyl group, and the like, and R _{1 to} R ₈ Particularly preferred are those in which all are iso-propyl groups or iso-butyl groups.

X ⁻ in the formula (1) is a monovalent anion, and examples thereof include an inorganic anion, an organic acid anion, and an organic metal anion.

  Examples of organic acids and organic metals include anions of organic carboxylic acids such as acetic acid, lactic acid, trifluoroacetic acid, propionic acid, benzoic acid, oxalic acid, succinic acid or stearic acid, methanesulfonic acid, toluenesulfonic acid, naphthalene monosulfone Acids, naphthalenedisulfonic acid, chlorobenzenesulfonic acid, nitrobenzenesulfonic acid, dodecylbenzenesulfonic acid, anion of organic sulfonic acid such as benzenesulfonic acid, ethanesulfonic acid or trifluoromethanesulfonic acid, tetraphenylboric acid, butyltriphenylboric acid or Organic boric acid anions such as tetrakis (pentafluorophenyl) boric acid, bis (trifluoromethanesulfonyl) imidic acid, tris (trifluoromethanesulfonyl) methidoic acid, bis (fluorosulfonyl) imidic acid or Examples include anions of fluorine-containing organic acids such as n-fluorophenylbis (trifluoromethanesulfonyl) methido acid, and preferred ones are tetrakis (pentafluorophenyl) boric acid, bis (trifluoromethanesulfonyl) imidic acid, tris which are strong acid anions. Each anion corresponding to (trifluoromethanesulfonyl) methido acid or pentafluorophenylbis (trifluoromethanesulfonyl) methide acid can be mentioned.

  Examples of inorganic substances include halogen anions such as fluorine, chlorine, bromine and iodine, thiocyanic acid, hexafluoroantimonic acid, perchloric acid, periodic acid, nitric acid, tetrafluoroboric acid, hexafluorophosphoric acid, molybdenum Anions such as acid, tungstic acid, titanic acid, vanadic acid, phosphoric acid, boric acid, tetrafluorotantalic acid or tetrafluoroniobic acid are preferred, and preferred are strong acid anions such as perchloric acid, tetrafluoroboron. Each anion corresponding to an acid, hexafluorophosphoric acid or hexafluoroantimonic acid can be used.

  Of these anions, each anion corresponding to hexafluoroantimonic acid, bis (trifluoromethanesulfonyl) imidic acid, tris (trifluoromethanesulfonyl) methide acid or pentafluorophenylbis (trifluoromethanesulfonyl) methide acid is particularly preferable.

The diimonium dye preferably used in the present invention may be used singly, but one or more other near-infrared rays may be used in consideration of the desired absorption wavelength range or absorption ratio of near-infrared rays or difficulty in obtaining them. Examples of other near-infrared absorbing dyes that may be used in combination with absorbing dyes include diimonium dyes other than the diimonium dyes, nitroso compounds and their metal salts, cyanine dyes, squarylium dyes, thiol nickel Examples thereof include complex salt compounds, phthalocyanine dyes, naphthalocyanine dyes, triallylmethane dyes, naphthoquinone dyes, and anthraquinone dyes.
The near-infrared absorbing dye containing the diimonium dye used in the present invention can be easily obtained from the market.

  The ionic liquid used in the present invention is a salt that is liquid at room temperature and is sometimes referred to as room temperature molten salt. The ionic liquid is composed only of anions and cations, and ionic liquids in various combinations are synthesized. For example, “Ionic Liquid II” supervised by Hiroyuki Ohno (published by CMC Publishing 2006) describes various methods for synthesizing various ionic liquids in addition to the introduction of commercial products.

  In the present invention, by containing an ionic liquid in the adhesive layer having near-infrared absorbing ability, it is possible to reduce deterioration of near-infrared absorbing dyes, particularly diimonium salt compounds, due to heat. When the anion of the dimonium salt compound and the anion of the ionic liquid are the same, it is considered that the heat resistance is improved by preventing the ion exchange between the anion contained in another dye or resin and the anion of the dimonium salt compound. .

The ionic liquid used in the present invention will be described in detail below.
In the present invention, the anion species constituting the ionic liquid is not particularly limited, and examples thereof include chlorine, bromine, iodine, tetrafluoroboric acid, hexafluorophosphoric acid, thiocyanic acid, perchloric acid, and trifluoromethanesulfone. Preferred examples include acid, trifluoroacetic acid, bis (trifluoromethanesulfonyl) imidic acid, bis (pentafluoroethanesulfonyl) imidic acid or tris (trifluoromethanesulfonyl) methic acid, and bis (trifluoromethanesulfonyl) imidic acid, Tris (trifluoromethanesulfonyl) methido acid or tetrafluoroboric acid is more preferred. Further, when the counter ion of the dimonium salt is bis (trifluoromethanesulfonyl) imidic acid, the effect of improving heat resistance can be obtained by using the same counter ion.

Examples of the cation species constituting the ionic liquid include cations having heteroaromatic groups such as imidazolium and pyridinium, cations such as aliphatic ammonium and alicyclic ammonium.
Among these cations, examples of the imidazolium-based cation include a cation represented by the following formula (2).

Examples of the pyridilinium cation include a cation represented by the following formula (3).

Furthermore, as an aliphatic ammonium type cation, the cation represented by following formula (4) is mentioned.

Furthermore, examples of the alicyclic ammonium cation include a cation represented by the following formula (5).

(In the formulas (2) to (6), R _{9 and} R ₂₀ are each independently a substituted or unsubstituted alkyl group (preferably having 1 to 20 carbon atoms, even if it is linear, branched) Or alicyclic, specific examples include, for example, methyl, ethyl, propyl, iso-propyl, pentyl, hexyl, octyl, 2-ethylhexyl, tert -Octyl group, decyl group, dodecyl group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclopentyl group, cyclohexyl group, etc.), or a substituted or unsubstituted alkenyl group (preferably having 2 to 20 carbon atoms) And may be linear or branched, and specific examples include, for example, a vinyl group, an allyl group, or a butenyl group, and more preferably a carbon number. Examples of preferable substituents include halogen atoms (F, Cl, Br, I), cyano groups, alkoxy groups, (methoxy groups, ethoxy groups, etc.), aryloxy groups (phenoxy groups, etc.). ), Alkylthio groups (such as methylthio groups and ethylthio groups), alkoxycarbonyl groups (such as ethoxycarbonyl groups), acyl groups (such as acetyl groups and propionyl groups), sulfonyl groups (such as methanesulfonyl groups and benzenesulfonyl groups), acyloxy groups (such as Acetoxy group, benzoyloxy group, etc.), amide group (acetylamide group, benzoylamino group, etc.), carbamoyl group (N, N-dimethylcarbamoyl group, etc.), alkyl group (methyl group, ethyl group, propyl group, butyl group, etc.) ), Aryl group (phenyl group, toluyl group, etc.) or heterocyclic group (pyridyl group, imidazo) Yl group, furanyl group, etc.).

Among these cations, a cation having an imidazolium-based or pyridinium-based heteroaromatic group is preferable, and more preferably an imidazolium-based or pyridinium-based cation whose substituent is an alkyl group having 2 to 6 carbon atoms. .
And as an anion of the ionic liquid used by this invention, bis (trifluoromethanesulfonyl) imide acid, a tris (trifluoromethanesulfonyl) methide acid, or a tetrafluoro boric acid is mentioned as a preferable example.
Specific examples of the ionic liquid preferably used in the present invention include Nn-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl) imide, N, N, N-trimethyl-N-propylammonium bis (trifluoromethanesulfonyl). Examples thereof include imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-allyl-3-ethylimidazolium bromide, and the like, which are easily available from the market. These ionic liquids can be used in combination of two or more.

  Hereinafter, a method for forming a near-infrared absorbing film by forming an adhesive layer containing an acrylic resin, a near-infrared absorbing pigment and an ionic liquid on a transparent substrate film will be described in detail. When several kinds of near-infrared absorbing dyes are used in combination, it is reasonable to mix and apply the coating liquid prepared in the same manner as the coating liquid using the following dimonium dye. Is.

  The near-infrared absorbing film of the present invention is preferably designed so that the transmittance of near-infrared light having a wavelength of 800 to 1100 nm is 20% or less. What is necessary is just to contain in an adhesive so that it may become weight%. If necessary, it may be used in combination with one or more other near-infrared absorbing dyes. In that case, it may be contained in the pressure-sensitive adhesive so as to be about 0.01 to 10% by weight with respect to the pressure-sensitive adhesive.

  In producing the near-infrared absorbing film of the present invention, it is preferable that the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer having near-infrared absorbing ability is prepared as a coating solution dissolved in a solvent and then used for coating. That is, for example, 100 parts by weight of the acrylic resin, 0.1 to 10 parts by weight of a diimonium dye as a near infrared absorbing dye, 1.0 to 70.0 parts by weight of an ionic liquid, and other additives such as an ultraviolet absorber A coating solution obtained by dissolving or dispersing 0 to 10 parts by weight in a solvent may be applied on a transparent substrate film and dried. The total content of the pressure-sensitive adhesive component in the coating solution is usually adjusted to be 10 to 30% by weight, and preferably 15 to 25%.

  The near-infrared absorbing film of the present invention can be produced, for example, by coating the above-described coating liquid on the transparent substrate film described below and drying it. The thickness of the pressure-sensitive adhesive layer containing a near-infrared absorbing dye, an ionic liquid and other additives is usually 5 to 50 μm, preferably 10 to 30 μm, and is 80 to 140 ° C., preferably 100 to 130 ° C. By drying, the components of the adhesive layer excluding the solvent are fixed on the transparent substrate film.

  A pressure-sensitive adhesive layer containing an acrylic resin, a near-infrared absorbing dye, an ionic liquid and other additives was provided on a release (release) film such as a polyethylene terephthalate film in the same manner as described above, and this was then described later. It is also possible to adopt a method in which the pressure-sensitive adhesive layer is transferred by bonding to a surface opposite to the surface provided with the layer having the functionality of the functional film.

  Examples of the solvent that can be used in preparing the coating liquid in the above include alcohols such as methanol, ethanol, isopropyl alcohol or diacetone alcohol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, tetrahydrofuran , Ethers such as dioxane, ethyl cellosolve or methyl cellosolve, amides such as N, N-dimethylformamide or N, N-dimethylacetamide, esters such as methyl acetate, ethyl acetate or butyl acetate, chloroform, methylene chloride or dichloroethylene Halogenated hydrocarbons such as benzene, toluene, xylene or monochlorobenzene, etc., or aliphatic hydrocarbons such as n-hexane or n-heptane, tetrafluoropropyl Fluorine-based solvents such as alcohol or pentafluoropropyl alcohol can be exemplified. These organic solvents may be used alone, or may be appropriately mixed and used as necessary.

  Coating of the coating solution is known per se such as flow coating, spraying, bar coating, gravure coating, roll coating, blade coating, air knife coating, lip coating or die coater. A coating method can be employed. By these methods, as described above, the coating solution is applied so that the finished film thickness is usually 5 to 50 μm, preferably 15 to 30 μm, and dried at 80 to 140 ° C. to form an adhesive layer. Is done. Usually, an aging process is performed thereafter. The conditions for the aging treatment vary depending on the acrylic resin to be used, the type and amount of the crosslinking agent, etc., but in the present invention, a method of storing in a constant temperature bath at 25 to 50 ° C. for about 1 day to 1 week is preferable.

  The transparent substrate film used in the present invention is not particularly limited as long as it is highly transparent, has no scratches, and can withstand use as an optical film, but the thickness is 10 to 500 μm. It can be said to be a preferable range because of good properties. Films include polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polycarbonates (PC), triacetates, polyacrylates, polymethyl methacrylate (PMMA), celluloses, polyolefins such as polypropylene The film can be appropriately selected from films of polystyrene, polystyrenes, urethane, etc., but preferably a film of PET, PC, PMMA or the like is used. The surface of the transparent substrate film can be coated with a corona discharge treatment, a plasma treatment, a glow discharge treatment, an anchor coating agent, a primer or the like in order to improve the adhesion with the coating film. The transparent substrate film itself is more preferably a film having a single function or a plurality of functions such as anti-reflection, anti-glare / anti-reflection, antistatic, antifouling, electromagnetic shielding or color adjustment, The rational production of the optical filter becomes possible.

  The near-infrared absorbing film of the present invention can be used alone as an optical film, but in a preferred embodiment, one or more films having any functionality other than the near-infrared absorbing film of the present invention are laminated. And used as an optical filter. Here, as a film having arbitrary functionality, for example, a film (anti-reflection film) having an anti-glare function and an anti-glare function for preventing the reflection of a background on the display unit and at the same time improving the contrast of a display image. ), A film having electromagnetic wave shielding ability (electromagnetic wave shielding film) for cutting electromagnetic waves emitted from a display device such as PDP, a film for cutting neon light, a hard coat layer for imparting scratch resistance, or a stain on the outermost surface. Examples thereof include a film having an antifouling layer for prevention.

Next, although the example of the film which has the said various functions is demonstrated below, a functional film is not limited to these.
The anti-reflection film reduces reflected light by causing surface reflected light and interface reflected light to interfere with each other. A film having a low refractive index layer in which a low refractive index agent such as magnesium fluoride or silica is coated with a binder resin on the surface of a transparent base film such as PET, or between the transparent base film and the low refractive index layer The film is provided with a hard coat layer, for example, a high refractive index layer containing titanium oxide, zinc oxide, zirconia and the like, and is controlled so as to cancel reflected light from each layer to improve visibility. Anti-glare and anti-reflective film is made by dispersing fine particles such as polystyrene resin and acrylic resin in the high refractive index layer and other layers of the anti-reflective film, and diffused reflection of external light to further improve visibility. It is a improved film.

  The electromagnetic shielding film has a mesh type in which ultrafine metal wires such as copper are held in a transparent substrate film in a mesh-like geometric pattern, and a transparent substrate made of a metal ultrathin film within the visible light transmission range There is a thin film type held in a film, and the latter thin film type generally does not reflect near infrared rays and does not transmit, so a near infrared absorption film is not particularly required, so the near infrared absorption film of the present invention is a mesh type electromagnetic wave. The shielding film can be suitably used as a transparent substrate film.

In PDP, neon light of orange color with a wavelength of 550 to 620 nm derived from Ne gas generated at the time of applied voltage needs to be cut to some extent in front of the display to reduce the color purity of red light. A neon light absorption filter held on a base film is usually used. Examples of the neon light absorbing compound include azaporphyrin, cyanine, squarylium, azomethine, xanthene, oxonol, and azo compounds. In addition, the method of obtaining the layer which can absorb a near-infrared ray and a neon light simultaneously by making the adhesive layer which has a near-infrared absorptivity contain the compound which has a neon light absorptivity can also be employ | adopted.
A film having a hard coat layer for imparting scratch resistance or an antifouling layer for preventing stains on the outermost surface, an adhesive layer or an adhesive film for laminating each layer, and the like are prepared by known methods, respectively. Or commercial products can be used as they are.

  The optical filter of the present invention is obtained by sequentially laminating the above films having other functions such as an electromagnetic wave shielding function and a reduced reflection function, using the near-infrared absorbing film of the present invention as an essential component. The optical filter of the present invention may be bonded to a glass plate or a plastic plate in advance and attached to the front surface of the plasma display, or may be used by directly bonding to the front surface of the PDP.

  The near-infrared-absorbing pressure-sensitive adhesive of the present invention includes, for example, 100 parts by weight of the acrylic resin, 0.1 to 10 parts by weight of near-infrared absorbing dye, 1.0 to 70 parts by weight of ionic liquid, and other ultraviolet absorbers It is obtained by dissolving or dispersing 0 to 10 parts by weight of the additive in the solvent. The total content of the pressure-sensitive adhesive component in the coating solution is preferably adjusted to be 10 to 30% by weight, and preferably 15 to 25%. The near-infrared absorbing adhesive of the present invention is preferably used for preparing a near-infrared absorbing film.

  The near-infrared absorbing film of the present invention has a simple manufacturing method, excellent near-infrared absorptive stability over time, and at the same time, adhesiveness to glass, PET film, polycarbonate, etc. that are frequently used as substrates for functional optical films. Are better. In addition, the optical filter obtained by laminating another functional film on this near infrared absorbing film is an excellent near infrared absorbing effect combined with the functions of various laminated functional films as an optical filter for PDP. give.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the examples, “parts” means parts by weight and “%” means percent by weight unless otherwise specified.

Example 1 (Preparation of near-infrared absorbing film)
A comma coater was prepared by applying the adhesive coating solution obtained by mixing and dissolving the materials shown in Table 1 uniformly onto a transparent base film PET • 3811 (trade name, peeled PET film, manufactured by Lintec). With a coating speed of 0.8 m / min and a drying temperature of 110 ° C., an adhesive layer was formed by coating so that the thickness of the adhesive layer was 18 μm. This was combined with KAYACOAT ARS-D510 (trade name, reduced A near-infrared absorbing film of the present invention having a low reflection property was obtained by pasting the opposite surface of the reflection film (manufactured by Nippon Kayaku Co., Ltd.).

Table 1
Materials Amount used • Acrylic resin (PTR-104) 111.0 parts • Near infrared absorbing dye (IRG-068) 0.50 parts • Ionic liquid (Nn-butyl-3-methylpyridinium bis (trifluoromethane sulfonyl) Imide) 50.0 parts UV absorber (Tinuvin 109) 0.90 parts Curing agent (M12ATY) 0.86 parts Curing agent (L45EY) 1.0 part Methyl ethyl ketone 520.0 parts (Amber)
PTR-104; trade name, heat crosslinkable acrylic resin (Tg = −40 ° C.), Nippon Kayaku IRG-068; trade name, diimonium dye (in formula (1), R _{1 to} R ₈ are all isopropyl A compound in which X ^{− is} di (trifluoromethanesulfonyl) imidic acid), Nippon Kayaku Tinuvin 109; trade name, benzotriazole compound, Ciba Geigy M12ATY; trade name, metal chelate compound, Nippon Kayaku L45EY Product name, isocyanate compound, Nippon Kayaku

<Creation of optical filter for PDP>
The near-infrared absorption is performed on the surface opposite to the surface provided with the adhesive layer and the protective film of ES-1534U (HCD-42-02) (trade name, electromagnetic shielding film, manufactured by Hitachi Chemical Co., Ltd.) having the adhesive layer. The film was bonded via an adhesive layer to obtain an optical filter for PDP of the present invention. This optical filter may be applied directly to the front surface of the PDP module, or may be attached to the front of the module after being applied to a transparent plate such as a glass plate, and all of them exhibit the necessary performance as an optical filter for PDP. Met.

Comparative Example 1
A comparative near-infrared absorbing film was obtained in the same manner as in Example 1 except that no ionic liquid was used in Example 1.

○ Evaluation test The luminous transmittance (Y /%) and chromaticity coordinates (x, y) of the test piece of the film of Example 1 and the film of each Comparative Example 1 before the test were measured, and the durability was set to 0 hours. A sex test was performed.
In the durability test, a dry heat resistance test for 500 hours in a constant temperature bath at 80 ° C. and a wet heat resistance test for 500 hours in a constant temperature and humidity bath at 60 ° C. and 90% relative humidity were performed.
The transmittance is UV-3150 (trade name, spectrophotometer, manufactured by Shimadzu Corporation), and luminous transmittance (Y /%) and chromaticity coordinates (x, y) are based on the XYZ color system of JIS Z 8701. Calculation was performed according to the color display method.
For the measurement of haze, TC-HIIIDPK (trade name, haze meter, manufactured by Tokyo Denshoku) was used.
The results of the durability test are shown in Table 2 and Table 3.

Table 2 Change with time in durability test (1) (dry heat resistance test)

Storage time Example 1 Comparative example 1
Luminous transmittance 0 hour 78.255 81.491
Y (%) 500 hours 78.198 83.230
Difference 0.057 1.639
Chromaticity coordinates 0 hour 0.322 0.320
x 500 hours 0.325 0.344
Difference 0.003 0.024
Chromaticity coordinates 0 hour 0.339 0.341
y 500 hours 0.350 0.395
Difference 0.011 0.054
Wavelength 950 nm 0 hour 0.76 2.03
Transmittance at 500 hours 1.89 21.34
(%) Difference 1.13 19.31
Haze 0 hours 0.50 0.50
500 hours 0.60 0.60
Difference 0.10 0.10

Table 3 Change with time in durability test (2) (Moisture and heat resistance test)

Storage time Example 1 Comparative example 1
Luminous transmittance 0 hour 78.756 81.593
Y (%) 500 hours 77.986 80.320
Difference 0.770 1.271
Chromaticity coordinates 0 hour 0.321 0.320
x 500 hours 0.327 0.343
Difference 0.006 0.023
Chromaticity coordinates 0 hour 0.339 0.341
y 500 hours 0.352 0.391
Difference 0.013 0.050
Wavelength 950 nm 0 hour 0.59 2.03
Permeability at 500 hours 1.29 19.97
(%) Difference 0.70 17.94
Haze 0 hours 0.50 0.50
500 hours 0.60 0.60
Difference 0.10 0.10

Discussion of results Example 1 containing an ionic liquid gave good results in both dry heat and wet heat durability tests. In Comparative Example 1 containing no ionic liquid, the change in luminous transmittance and color change are large, and the change in transmittance at a wavelength of 950 nm is large, and the performance of the near-infrared absorbing film is not practical.

Claims (8)

A near-infrared absorbing film comprising an adhesive layer formed of an adhesive containing an acrylic resin, a near-infrared absorbing dye, and an ionic liquid on one surface of a transparent substrate film. The near-infrared absorbing film according to claim 1, wherein the glass transition temperature (Tg) of the acrylic resin is in the range of -80 to 0 ° C. The near-infrared absorbing film according to claim 1 or 2, wherein the near-infrared absorbing dye is a diimonium-based dye represented by the following formula (1).

(In Formula (1), R _{1 to} R ₈ each independently represents an aliphatic hydrocarbon residue which may have a hydrogen atom or a substituent, and X ⁻ represents a monovalent anion.) The near-infrared absorbing film according to any one of claims 1 to 3, wherein the anion constituting the ionic liquid is a bis (trifluoromethanesulfonyl) imido ion. The near-infrared absorbing film according to any one of claims 1 to 4, wherein a cation constituting the ionic liquid is an ion having a heteroaromatic group. The near-infrared absorbing film according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive is a pressure-sensitive adhesive containing a crosslinking agent. An optical filter for a plasma display panel comprising the near-infrared absorbing film according to any one of claims 1 to 6, a film having an electromagnetic wave shielding function, and a film having an anti-reflection function as essential constituent elements. A near-infrared absorbing pressure-sensitive adhesive containing an acrylic resin, a near-infrared absorbing dye, and an ionic liquid.