JP2009029838A - Near-infrared ray absorbing pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a near infrared absorbing pressure-sensitive adhesive sheet that is excellent in the near infrared absorption and in the visible light transmittance and is excellent in the antistatic property and in the moist heat resistance. <P>SOLUTION: The near infrared absorbing pressure-sensitive adhesive sheet comprises a composition mainly comprising a near infrared absorbing pigment and a self-adhesive resin. The near infrared absorbing pressure-sensitive adhesive sheet contains an ionic liquid in the composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive sheet that absorbs near-infrared rays, and more specifically, a near-infrared-absorbing pressure-sensitive adhesive sheet having high near-infrared absorption and antistatic properties, low haze, excellent transparency, and excellent moisture and heat resistance. About.

  In recent years, the development of flat panel displays such as plasma displays, liquid crystal displays, and organic electroluminescence has been remarkable. However, these flat panel displays may generate light having an unnecessary wavelength other than visible light. For example, in a plasma display, xenon gas is sealed in a cell serving as a light emitting unit. However, near infrared rays are generated due to xenon gas, and an electronic device using a near infrared remote controller causes a malfunction. For this reason, a member having near infrared absorption ability is used on the front surface of the plasma display.

As a member having the ability to absorb near infrared rays, (1) a phosphoric acid glass containing metal ions such as copper and iron, (2) a layer having different refractive indexes is laminated, and the transmitted light is interfered with, so An interference filter that transmits wavelengths, (3) an acrylic resin film containing copper ions in a copolymer, and (4) a film in which a layer in which a pigment is dispersed or dissolved in a resin are laminated. Among these, the film (4) has good workability and productivity, has a relatively large degree of freedom in optical design, and various methods have been proposed (see Patent Documents 1 to 9).
JP 2002-82219 A JP 2002-138203 A JP 2002-214427 A JP 2002-264278 A JP 2002-303720 A JP 2002-333517 A JP 2003-82302 A Japanese Patent Laid-Open No. 2003-96040 JP 2003-114323 A

  By the way, some functional films are used on the front surface of the flat panel display. For example, plasma displays are emitted from a near-infrared absorbing film that absorbs near-infrared rays, an electromagnetic shielding film that reduces electromagnetic waves radiated from the plasma display, an antireflection film that reduces reflection of outside light on the screen, and a plasma display. There is a color correction film that adjusts the light to correct the color tone. In actual use, these functional films are generally bonded together with an adhesive sheet or the like and used as a front filter. However, due to the high image quality and high definition of the display, the appearance of defects such as slight foreign matter and air entrainment mixed at the time of bonding has become an increasing number of defective products. Furthermore, when used as a front filter for a large area display such as a plasma display, the frequency of occurrence of defects increases. Moreover, in order to produce the above-mentioned front filter, an increase in the number of members and an increase in the number of times of bonding lead to an increase in cost.

  For the above reasons, when the front filter of the display is produced by bonding a plurality of functional films, it is desirable to reduce the number of times of bonding as much as possible.

  As a method of reducing the number of times of bonding, it is preferable to provide a plurality of functions in one functional film or one functional layer. Specifically, it is conceivable to combine the adhesive function and the function having near infrared absorption.

  By the way, a pressure-sensitive adhesive sheet is usually provided with a release sheet on the pressure-sensitive adhesive surface, and is used by being peeled off when being attached to an adherend. However, when peeled off, static electricity is generated on the sheet, and dust, dust, etc. are easily caught. . In particular, when used for a display or the like, it becomes a defect in appearance and the quality is lowered. An example of countermeasures against static electricity is to add an antistatic agent to the adhesive sheet. However, the addition of an antistatic agent may reduce the quality when used for a display or the like. For example, when an inorganic antistatic agent is used, the haze value (cloudiness) increases. Also, depending on the type of antistatic agent, it may react with a near-infrared absorbing compound to reduce near-infrared absorbing ability or cause discoloration, and further, when left at high temperature and high humidity for a long time, Similarly, near-infrared absorptivity may decrease and discoloration may occur.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and is a near-infrared-absorbing pressure-sensitive adhesive sheet that has excellent near-infrared absorption and visible-light transmittance, and excellent antistatic properties and moisture and heat resistance. Is to provide.

  The near-infrared-absorbing pressure-sensitive adhesive sheet of the present invention that can solve the above problems has the following configuration.

  1st invention is a near-infrared absorption adhesive sheet which consists of a composition which has a near-infrared absorption compound and an adhesive resin as a main component, Comprising: An ionic liquid is contained in the said composition, The near-infrared characterized by the above-mentioned It is an absorption adhesive sheet.

  2nd invention is a near-infrared absorption adhesive sheet of 1st invention that a near-infrared absorption compound contains either a diimonium salt type compound, a phthalocyanine type compound, and a metal complex type compound.

  A third invention is the near-infrared absorbing pressure-sensitive adhesive sheet according to the first or second invention, wherein the ionic liquid is contained in an amount of 0.1% by mass to 30.0% by mass with respect to the adhesive resin component. is there.

In the fourth invention, the ionic liquid is PF ₆ ⁻ , ClO ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , Any one of (CN) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) (CF ₃ CO) N ⁻ is included as an anion. It is the near-infrared absorption adhesive sheet of any of invention.

A fifth invention is an ionic liquid _{(CF 3 SO 2) 2 N} - is the first to fourth one of the near infrared absorbing pressure-sensitive adhesive sheet invention, which comprises as an anion.

  A sixth invention is the near-infrared absorbing pressure-sensitive adhesive sheet according to any one of the first to fifth inventions, wherein the pressure-sensitive adhesive resin is an acrylic resin.

  7th invention is the near-infrared absorption adhesive sheet in any one of 1st-6th invention characterized by installing in the front surface of a display.

The near-infrared absorbing pressure-sensitive adhesive sheet of the present invention has a high near-infrared absorbing ability and transparency in the visible region, and also has an adhesive function. Can be reduced. Therefore, it is possible to reduce the frequency of appearance defects due to the inclusion of foreign matter or air mixed during bonding, and it is possible to improve the yield and reduce the cost. Moreover, since the ionic liquid is contained in the composition containing the near-infrared absorbing compound and the adhesive resin as main components, it is excellent in antistatic property, wet heat resistance, and transparency. Since it has antistatic performance, it prevents the inclusion of foreign matter, dust, dust, etc., and contributes to the improvement of appearance characteristics. In addition, the near-infrared absorptivity and color tone are stable over a long period of time even in a high-temperature and high-humidity atmosphere.
Further, since it has a high transmittance in the visible light region, it is suitable as an optical filter used in image display devices such as a plasma display, a liquid crystal display, an electroluminescence display, a fluorescent display tube, and a field emission display.

  The near-infrared-absorbing pressure-sensitive adhesive sheet of the present invention is a near-infrared-absorbing pressure-sensitive adhesive sheet comprising a composition mainly composed of a near-infrared-absorbing compound and a pressure-sensitive adhesive resin, and contains an ionic liquid in the composition. And Hereinafter, the present invention will be described in detail.

(Adhesive resin)
The pressure-sensitive adhesive resin in the present invention is not particularly limited, such as an acrylic resin, a silicon resin, or a rubber resin, but an acrylic resin suitable for optical use is preferable.

  The acrylic adhesive resin can be produced by polymerizing monomers such as (meth) acrylic acid alkyl ester. Specific examples of monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, and t-butyl (meth). Alkyls (meth) such as acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc. ) Acrylate compounds.

  Furthermore, a monomer having a hydrophilic group can be copolymerized. By copolymerizing a monomer having a hydrophilic group, adhesion to an adherend can be increased. Specifically, it is a monomer having a hydroxyl group, a carboxyl group, an amide group, an amino group or the like. More specifically, acrylic acid, methacrylic acid, maleic anhydride, styrene containing a carboxyl group, 2-hydroxylethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, acrylamide, methacrylamide, dimethylaminoethyl (meth) ) Acrylate and the like.

  In the case of an acrylic resin, the pressure-sensitive adhesive resin can be produced by sequentially polymerizing the monomers, but a polymerization initiator is added to accelerate the polymerization reaction. After completion of the polymerization reaction, the unreacted portion of the polymerization initiator is used without being separated from the obtained acrylic adhesive resin. The unreacted content of the polymerization initiator affects the near-infrared absorbing compound and lowers the durability performance such as moist heat resistance. Therefore, it is necessary to reduce the unreacted amount of the polymerization initiator as much as possible. Specifically, it is 0.2% by mass or less with respect to the acrylic adhesive resin component. Furthermore, it is preferable that it is 0.1 mass% or less, and it is most preferable that it is 0.05 mass% or less. The unreacted amount of the polymerization initiator can be controlled by the polymerization time, the polymerization temperature, the addition amount of the polymerization initiator, and the like.

  In the present invention, specific examples of the polymerization initiator include benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-hexyl peroxide. Oxide, t-butyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate , Organic peroxides such as lauroyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyrate) And azo compounds such as (ronitrile).

  The glass transition temperature of the adhesive resin is preferably −80 ° C. or higher and 5 ° C. or lower, and more preferably −70 ° C. or higher and −20 ° C. or lower. The molecular weight is preferably 10,000 to 3,000,000, more preferably 50,000 to 2,000,000 in terms of weight average molecular weight. When it is less than 10,000, when forming the adhesive layer, the viscosity is too low and the fluidity becomes too large, and it becomes difficult to form a uniform layer as a sheet. On the other hand, if it exceeds 3,000,000, the viscosity becomes too high and the leveling action is not sufficiently exhibited, and it becomes difficult to form a uniform layer as well.

  In the present invention, when the adhesive resin is an acrylic resin, a methacrylic ester resin can be added for the purpose of improving the dispersibility and durability of the near-infrared absorbing compound to be added. A methacrylic ester resin is more preferable as the affinity with the near-infrared absorbing compound is higher. When the affinity is increased, the action of preventing the near-infrared absorbing compound from agglomerating and further suppressing the chemical change is increased, and the stability is improved.

  Furthermore, in the adhesive resin, when the structural unit of (Formula 1) is a main component, the methacrylic ester resin to be added preferably includes the structural unit of (Formula 2).

  (In formulas 1 and 2, A represents an alkyl group, an aryl group, an alkenyl group, an aralkyl group, or an alkynyl group, and may have a substitution)

  In the methacrylate ester resin, having the structural unit of (Formula 2) that is structurally similar to (Formula 1) improves compatibility with the acrylic ester resin and maintains high transparency. It becomes possible. In the methacrylic acid ester-based resin, the proportion including the structural unit of (Formula 2) is preferably 20 to 100% by mass, and more preferably 30 to 100% by mass. Most preferably, it is 40-100 mass%. When the amount is less than 20% by mass, the compatibility with the adhesive resin is deteriorated. As a result, the transparency is lowered, the haze is increased, and the requirement for display is not satisfied.

  The methacrylic ester resin can be produced by polymerizing a methacrylic ester monomer. Specific examples of methacrylic acid esters include ethyl methacrylate, propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, and iso-octyl methacrylate. , Lauryl methacrylate and stearyl methacrylate are preferred. In addition, alkyl methacrylate compounds such as methyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate can also be used.

  Furthermore, a monomer having a hydrophilic group can be copolymerized with the methacrylic ester resin. By copolymerizing a monomer having a hydrophilic group, adhesion with an adherend can be increased. Specifically, it is a monomer having a hydroxyl group, a carboxyl group, an amide group, an amino group or the like. More specifically, acrylic acid, methacrylic acid, maleic anhydride, styrene containing a carboxyl group, 2-hydroxylethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, acrylamide, methacrylamide, dimethylaminoethyl (meth) ) Acrylate and the like.

  The glass transition temperature of the methacrylic ester resin is preferably 30 ° C. or higher and 160 ° C. or lower, more preferably 40 ° C. or higher and 150 ° C. or lower, and most preferably 50 ° C. or higher and 130 ° C. or lower. When the glass transition temperature is less than 30 ° C., the dispersibility of the near-infrared absorbing compound is decreased, causing aggregation, and the absorption in the near-infrared region is decreased. Furthermore, the chemical stability of the near-infrared absorbing compound is also lowered, and the color tone is greatly changed. When it exceeds 160 degreeC, the adhesiveness fall as an adhesive sheet is caused.

  The molecular weight of the methacrylic ester resin is preferably 5,000 to 3,000,000, more preferably 10,000 to 2,000,000 in terms of weight average molecular weight.

  When the adhesive resin is (resin A) and the methacrylic ester resin is (resin B), the mass ratio is preferably (resin A) / (resin B) = 70/30 to 98/2. More preferably, it is 20-95 / 5. When the ratio of (resin A) is lower than (resin A) / (resin B) = 70/30, the adhesive performance is lowered and the adhesion to the adherend is lowered. When the ratio of (resin B) is lower than 98/2, the dispersibility of the near-infrared absorbing compound, in particular, the diimonium salt-based compound is lowered, and the agglomeration of the near-infrared absorbing compound occurs particularly in the moisture and heat resistance test. Decreases. Both (Resin A) and (Resin B) can be obtained by sequentially polymerizing the monomers, but as an actual method, they can be obtained by solution polymerization, emulsion polymerization or the like.

  Furthermore, in the near-infrared absorbing pressure-sensitive adhesive sheet of the present invention, a crosslinking agent can be added for the purpose of increasing the cohesive force. For example, polyfunctional compounds such as isocyanate, epoxy, melamine, urea, and metal chelate are listed. The cross-linking agent is preferably contained in the pressure-sensitive adhesive sheet component in an amount of 0.01 to 10% by mass. The cross-linking agent can be subjected to a cross-linking reaction by heating after sheet formation, and can be aged at an appropriate temperature as necessary to further promote the cross-linking reaction.

(Near-infrared absorbing compound)
Although there is no restriction | limiting in particular as a near-infrared absorption compound which can be used in this invention, It is preferable to use an organic pigment | dye, Among them, it is preferable to use the compound which has maximum absorption in 800 nm-1200 nm, and the transmittance | permeability of visible region is used. High is preferred. Examples of organic dyes include diimonium salt, phthalocyanine, metal complex, naphthalocyanine, azo, polymethine, anthraquinone, naphthoquinone, pyrylium, thiopyrylium, squarylium, croconium, tetradehydride Examples include ocholine-based, triphenylmethane-based, cyanine-based, azo-based, and aminium-based compounds. These can be used alone or in combination. In the present invention, it is preferable that any of a diimonium salt-based compound, a phthalocyanine-based compound, and a metal complex-based compound is included from the viewpoint of excellent durability. Examples of the diimonium salt compound include a compound represented by (Formula 3).

(In the formula, R1 to R8 represent a hydrogen atom, an alkyl group, an aryl group, an alkenyl group, an aralkyl group, and an alkynyl group, and may be the same or different. R9 to R12 are hydrogen atoms) Represents an atom, a halogen atom, an amino group, a cyano group, a nitro group, a carboxyl group, an alkyl group, or an alkoxy group, which may be the same or different. X ⁻ represents a trifluoromethanesulfonyl imido acid ion ((CF ₃ SO ₂ ) ₂ N ⁻ ).

  Specific examples of R1 to R8 in the formula (3) include alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, t-butyl, n -Aryl group, n-hexyl group, n-octyl group, 2-hydroxyethyl group, 2-cyanoethyl group, 3-hydroxypropyl group, 3-cyanopropyl group, methoxyethyl group, ethoxyethyl group, butoxyethyl group, etc. are aryl Examples of the group include a phenyl group, a fluorophenyl group, a chlorophenyl group, a tolyl group, diethylaminophenyl, and a naphthyl group. Examples of the alkenyl group include a vinyl group, a propenyl group, a butenyl group, and a pentenyl group. Examples of the aralkyl group include a benzyl group. , P-fluorobenzyl group, p-chlorophenyl group, phenylpropyl group, naphthylethyl R9 to R12 are hydrogen, fluorine, chlorine, bromine, diethylamino group, dimethylamino group, cyano group, nitro group, methyl group, ethyl group, propyl group, trifluoromethyl group, methoxy group, ethoxy group, and the like. Group, propoxy group and the like. Moreover, it can also obtain as a commercial item, for example, Nippon Kayaku Kayasorb IRG-068, Nippon Carlit CIR-1085, CIR-RL etc. can be used suitably.

  Examples of the phthalocyanine compound include IR-1, IR-10A, IR-12, IR-14, TX-EX906B, and TX-EX910B manufactured by Nippon Shokubai Co., Ltd. as commercially available products.

  Examples of the metal complex compounds include commercially available products such as Yamamoto Kasei SIR-128, SIR-130, SIR-132, SIR-159, Midori Kagaku MIR-101, MIR-102, MIR-103, and MIR-105. , MIR-111, MIR-121, NKX-1199 manufactured by Hayashibara Biochemical Laboratory, and the like.

  In the present invention, the composition ratio of the near infrared absorbing compound to the adhesive resin is preferably 0.01% by mass or more and 10.0% by mass or less, more preferably 0.01% by mass or more and 5.0% by mass or less. . Most preferably, it is 0.01 mass% or more and 3.0 mass% or less. When the amount of the near-infrared absorbing compound in the adhesive resin is small, it is necessary to increase the coating amount in order to achieve the target near-infrared absorbing ability. Increases the load on the drying process. Moreover, since the coating amount of the adhesive resin increases, the adhesive force may become stronger than necessary. Conversely, when the amount of the near-infrared absorbing compound in the adhesive resin is large, the agglomeration of the near-infrared absorbing compound occurs particularly under heating such as drying or heat resistance test after coating, and the absorption ability in the near-infrared region is increased. Adverse effects such as lowering and higher haze appear. Moreover, since the coating amount of adhesive resin reduces, required adhesive force may not be acquired.

  In the plasma display, a discharge occurs between electrodes, which becomes a light emission source. Neon gas is sealed in a space where discharge occurs, and orange so-called neon light is emitted. As a display, it is not preferable to emit orange light, and it is desirable to suppress neon light. In the present invention, if necessary, a compound that cuts off neon light can also be added.

  As a compound that cuts off neon light, it is preferable that there is a maximum absorption between 570 nm and 600 nm, and the absorption in the other visible light region is small. Furthermore, the half width of the absorption peak is preferably 60 nm or less, and more preferably 50 nm or less. Moreover, it is preferable that a maximum absorption value is the transmittance | permeability 10-60 (%).

  Specific examples of the compound that cuts off neon light include cyanine, polymethine, squarylium salt, phthalocyanine, naphthalocyanine, quinone, azo, azo chelate, azurenium, pyrylium, croconium, Examples include indoaniline chelate, indonaphthol chelate, azo chelate, dithiol metal complex, pyromethene, azomethine, xanthene, oxonol, tetraazaporphyrin, and the like. These are also available as commercial products, and specifically, ADE-102 TY-102, (Yamada Chemical Industries) TAP-2, TAP-12, TAP-18, TAP-45, Kyowa Hakko Chemical SD- 184, SD-883, SD-929, Mitsui Chemicals PD-311, PD-319, and the like.

(Ionic liquid)
The near-infrared absorbing pressure-sensitive adhesive sheet of the present invention contains an ionic liquid. By containing the ionic liquid, the antistatic performance is improved while maintaining the transparency without deteriorating the near-infrared absorbing compound and further increasing the haze value.

  In the present invention, the ionic liquid is a liquid salt composed of anion and cation ions.

Examples of the anion species constituting the ionic liquid include Cl ⁻ , Br ⁻ , I ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , and CH ₃ COO ^−. , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , ^{_{TaF 6 -, F (HF)}} n -, (CN) 2 n -, C 4 F 9 SO 3 -, (C 2 F 5 SO 2) 2 n -, C 3 F 7 COO -, (CF 3 SO 2 ) _(CF 3 CO) N ^- and the like are go up. In particular, when a diimonium salt compound is used as the near-infrared absorbing compound, PF ₆ ⁻ , ClO ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF _{6 ^{-, NbF 6 -, (CN}} ) 2 N -, (C 2 F 5 SO 2) 2 N -, (CF 3 SO 2) (CF 3 CO) N - are preferred, in the case of using these color tone Is stable and the heat and humidity resistance is improved. Moreover, preferably _{(CF 3 SO 2) 2 N} - is the case of. The reason why the heat-and-moisture resistance is good is not clearly understood. Is considered small.

  As the cation species, it is preferable to use those comprising nitrogen-containing onium, sulfur-containing onium, or phosphorus-containing onium. Specific examples include imidazolium, pyridinium, ammonium, sulfonium, phosphonium, and the like.

  A commercially available ionic liquid as described above may be used, but it can also be synthesized as follows. The method for synthesizing the ionic liquid is not particularly limited as long as the target ionic liquid is obtained. In general, the document “ionic liquids—the forefront and future of development” [CMC Publishing Co., Ltd.] A halide method, a hydroxide method, an acid ester method, a complex formation method, a neutralization method and the like as described in “Issuance” are used.

  The content of the ionic compound is preferably 0.1% by mass or more and 30.0% by mass or less in the near infrared absorption layer. If it is less than 0.1% by mass, the antistatic performance is hardly exhibited, and if it exceeds 30.0% by mass, the adhesive performance is deteriorated.

  Furthermore, in this invention, it is also possible to mix an ultraviolet absorber for the purpose of improving light resistance. UV absorbers are broadly classified into organic UV absorbers and inorganic UV absorbers. From the viewpoint of ensuring transparency, it is desirable to use organic UV absorbers (low molecular type and high molecular type). . Although it does not specifically limit as an organic type ultraviolet absorber (low molecular type), For example, a benzotriazole type, a benzophenone type, a cyclic imino ester type, etc., and these combination are mentioned. Among these, benzotriazole type and cyclic imino ester type are preferable from the viewpoint of durability.

  The content of the ultraviolet absorber is preferably adjusted so that the transmittance at a wavelength of 380 nm or less is 10% or less so that the photodegradation of the near-infrared absorbing layer can be suppressed. Specifically, the content of the ultraviolet absorber is preferably 0.1 to 4% by mass and more preferably 0.3 to 2% by mass with respect to the adhesive resin. When the amount of the ultraviolet absorber is too small, the ultraviolet absorbing ability is decreased, and when it is too large, the yellowing may occur.

(Formation of near-infrared absorbing adhesive sheet)
In this invention, a near-infrared absorption adhesive sheet is produced by forming a thin layer on a base material. As a forming method, a coating method in which a near-infrared absorbing compound or the like and a resin are dissolved in a solvent, applied onto a substrate, dried, and laminated is preferable because uniformity in the width direction and the flow direction of the layer can be easily obtained.

  The solvent in the coating method needs to be a solvent that can uniformly dissolve or disperse a resin, a near-infrared absorbing compound, and the like. In the present invention, an organic solvent is preferable.

  Examples of the organic solvent include (1) alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tridecyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl alcohol, and (2) ethylene glycol. , Glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, glycerin, (3) diethyl ether, tetrahydrofuran, dioxolane, ethylene glycol monomethyl ether, ethylene glycol monoethylene ether, ethylene glycol monobutyl ether, diethylene glycol Monomethyl ether, diethylene glycol monoethyl ether, diethylene Glycol ethers such as recall butyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, diethylene glycol monoethyl acetate, diethylene glycol monobutyl acetate, (4) ethyl acetate, isopropylene acetate, Esters such as n-butyl acetate, (5) Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, isophorone, diacetone alcohol, (6) n-hexane, n-heptane, toluene, xylene Can be used, and these can be used alone or in admixture of two or more.

  The boiling point of the solvent is preferably 40 ° C. or higher and 180 ° C. or lower, and more preferably 60 ° C. or higher and 150 ° C. or lower. When the boiling point is low, the solvent evaporates too much during coating, the solid content concentration of the coating solution changes, and the coating thickness becomes unstable. On the other hand, when the boiling point is high, it takes a load on the drying process to evaporate the solvent. In addition, the amount of the organic solvent remaining in the coating film increases, resulting in poor stability over time.

  In the present invention, a surfactant can also be contained. By including the surfactant, the coating appearance of the near-infrared absorbing pressure-sensitive adhesive sheet, in particular, dents due to minute bubbles and adhesion of foreign substances, etc., and repellency in the drying process are improved. As the surfactant, known cationic, anionic and nonionic surfactants can be preferably used.

  Examples of the method for dissolving or dispersing the near-infrared absorbing compound and the resin in an organic solvent include stirring, dispersion and pulverization methods under heating. By heating, the solubility of the additive and the resin can be improved, and the defective appearance to the coating due to the undissolved material is prevented. Moreover, it becomes possible to form a layer having excellent transparency by dispersing and pulverizing the resin and the additive in a fine particle state of 0.3 μm or less in the coating solution. As the disperser and the pulverizer, known ones can be used. Specifically, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a colloid mill, an ultrasonic homogenizer, a homomixer, a pearl mill, a wet jet mill, a paint Examples include a shaker, a butterfly mixer, a planetary mixer, a Henschel mixer, and the like.

  When contamination or undissolved material of 1 μm or more is present in the coating solution, the appearance after coating becomes poor. Therefore, it is necessary to remove it with a filter or the like before coating. Various filters can be suitably used as the filter, but it is preferable to use a filter that removes 99% or more of a 1 μm size filter. When a coating liquid containing 1 μm or more of contamination or undissolved material is applied and dried, a dent or the like is generated around the coating liquid, which may be a defect of a size of 100 to 1000 μm.

  The solid content concentration of the resin and additives contained in the coating solution is preferably 10% by mass or more and 60% by mass or less. When the solid content concentration is low, the viscosity of the coating solution becomes too low, and uneven coating tends to occur during drying. On the other hand, when the solid content concentration is high, the viscosity of the coating solution becomes high and the leveling property is insufficient, and the coating appearance tends to be poor. The viscosity of the coating solution is preferably 10 cp or more and 100 p or less in view of the coating appearance, and it is preferable to adjust the solid content concentration, the organic solvent, etc. so as to be in this range.

  In the present invention, it is preferable that a coating liquid containing the near-infrared absorbing compound, adhesive resin, ionic liquid, etc. is applied on a substrate and dried to form a layer having a uniform thickness. As a specific method of application, for example, in the case of a small scale as produced in a laboratory, there is a method of forming a layer by applying and drying on a substrate using a wire bar, applicator, etc. Applicable. In addition, when the scale is relatively large and the substrate is in the form of a roll and forms layers continuously, the gravure coating method, kiss coating method, dip method, spray coating method, curtain coating method, air knife coating method, blade Conventionally used methods such as a coating method, reverse roll coating method, bar coating method, lip coating method, and die coating method can be applied.

  Examples of the method for drying the coating solution include known heat drying, hot air drying, and drying using an infrared heater. A preferable temperature during drying is 60 ° C. or higher and 180 ° C. or lower. Particularly preferably, the lower limit is 80 ° C. and the upper limit is 160 ° C. When the temperature is low, the solvent in the coating film is difficult to decrease, which affects the adhesive performance. On the other hand, when the temperature is high, the near-infrared absorbing compound is deteriorated by heat. The drying time is preferably 5 seconds or more and 300 seconds or less. When the time is short, the amount of the solvent remaining in the layer increases, which affects the adhesive performance. Conversely, when the time is long, the near-infrared absorbing compound deteriorates.

  As the coating appearance of the near-infrared absorbing pressure-sensitive adhesive sheet, it is necessary not to have a defect having a diameter of 300 μm or more, more preferably 100 μm. The defect of 300 μm or more becomes like a bright spot when installed on the front surface of the plasma display, and the defect becomes noticeable. Also, streaks, unevenness, etc. with a thin coating layer become prominent on the front surface of the display and become a problem.

  In the present invention, the base material for forming the near-infrared absorbing pressure-sensitive adhesive sheet as described above is not limited, but is generally formed on a plastic film or glass. When a plastic film is used, the type is not particularly limited, and examples thereof include polyolefin, polyester, polycarbonate, and nylon. The thickness of the plastic film is preferably 10 to 500 μm, and more preferably 25 to 250 μm. When the plastic film is used as it is as a part of a member such as a front filter, the near-infrared absorbing adhesive sheet can be formed as it is on the plastic film without treating the surface of the plastic film. Furthermore, when it is necessary to improve the adhesiveness with the adhesive sheet, an undercoat layer can be provided on the surface of the plastic film that contacts the adhesive sheet. The material used for the undercoat layer is not particularly limited, and examples thereof include polymer materials such as acrylic, polyester, polycarbonate, polystyrene, and cellulose derivatives. A release layer may be provided on the surface of the plastic film, and the near-infrared absorbing pressure-sensitive adhesive sheet may be adhered to another member and then removed and used as a release film.

The coating amount after drying of the near infrared absorbing pressure-sensitive adhesive sheet of the present invention is not particularly limited, 3 g / ^{m 2} or more 100 g / ^{m 2} or less, and more preferably 10 g / ^{m 2} or more 50 g / ^{m 2} or less. When the coating amount is less than 3 g / m ² , the adhesive strength is insufficient and the absorption of near infrared rays may be insufficient. Moreover, when it exceeds 50 g / m < ² >, adhesive force will become strong too much and the transmission of visible light may become inadequate.

  As the coating appearance of the near-infrared absorbing pressure-sensitive adhesive sheet of the present invention, it is necessary not to have a defect having a diameter of 300 μm or more, more preferably 100 μm. The defect of 300 μm or more becomes a bright spot when placed on the front surface of the display, and the defect becomes noticeable. Defects of 100 μm or more and less than 300 μm may be emphasized due to the lens effect or the like by bonding, and should be avoided as much as possible. Also, thin stripes, unevenness, etc. become prominent on the front surface of the display and become a problem.

(Combination with other functional materials)
The near-infrared absorbing adhesive sheet of the present invention can be combined with other functional materials required for the front surface of the display. For example, the conductive layer may be provided directly or via a substrate for the purpose of blocking harmful electromagnetic waves emitted from the display. Either a metal mesh or a conductive thin film may be used for the conductive layer. When a metal mesh is used, it is necessary to have a metal mesh conductive layer having an aperture ratio of 50% or more. If the aperture ratio of the metal mesh is low, the electromagnetic shielding property is good, but there is a problem that the light transmittance is lowered. For this reason, an aperture ratio of 50% or more is necessary to obtain a good light transmittance. Become. As the metal mesh used in the present invention, a metal foil having a high electrical conductivity is subjected to etching treatment to form a mesh, a woven mesh using metal fibers, or metal on the surface of polymer fibers. You may use the fiber adhered using methods, such as plating. The metal used for the electromagnetic wave absorbing layer is not particularly limited as long as it has high electrical conductivity and good stability, but from the viewpoint of workability, cost, etc., copper, nickel, Tungsten etc. are good.

  When a conductive thin film is used, the transparent conductive layer may be any conductive film, but is preferably a metal oxide. Thereby, a higher visible light transmittance can be obtained. Further, in the present invention, when it is desired to improve the conductivity of the transparent conductive layer, it is preferably a repeating structure of three or more layers of metal oxide / metal / metal oxide. Conductivity can be obtained while maintaining a high visible light transmittance by multilayering the metal. Used in the present invention. The metal oxide may be any metal oxide as long as it has electrical conductivity and visible light transmittance. Examples include tin oxide, indium oxide, indium tin oxide, zinc oxide, titanium oxide, and bismuth oxide. The above is an example and is not particularly limited. The metal layer used in the present invention is preferably gold, silver or a compound containing them from the viewpoint of conductivity.

  Furthermore, when the conductive layer is multi-layered, for example, when the number of repeated layers is 3, the thickness of the silver layer is preferably 50 to 200 mm, more preferably 50 to 100 mm. When the film thickness is thicker than this, the light transmittance decreases, and when it is thin, the resistance value increases. Further, the thickness of the metal oxide layer is preferably 100 to 1000 mm, more preferably 100 to 500 mm. If it is thicker than this, it will be colored to change its color tone, and if it is thin, the resistance value will increase. In addition, when three or more layers are formed, for example, when five layers are formed such as metal oxide / silver / metal oxide / silver / metal oxide, the thickness of the central metal oxide is the other metal. It is preferable that it is thicker than the thickness of the oxide layer. By doing so, the light transmittance of the entire multilayer film is improved.

  Also, it can be combined with an antireflection function. The antireflection function has a function of preventing surface reflection and preventing reflection of a fluorescent lamp or the like. The method of imparting the antireflection function can be arbitrarily selected without limitation. For example, a method of laminating layers having different refractive indexes on the surface of a base material and reducing the interference by using interference of reflected light at the interface of the layers And a method of providing irregularities on the surface. As a method for forming the antireflection film of this method, the following two methods can be broadly mentioned. One method is to form an antireflection film on the surface of the substrate by vapor deposition or sputtering, and the other method is to apply an antireflection coating solution to the surface of the substrate and dry it. This is a method for forming an antireflection film. As a general theory, it is said that the former is superior in terms of antireflection characteristics and the latter is superior in terms of economy, but either method may be used in the present invention. The antireflection film can be provided with a base material such as a transparent polyester film. The near-infrared-absorbing pressure-sensitive adhesive sheet of the present invention can be combined by forming it on the opposite surface of the base material provided with the antireflection film.

(Optical filter)
In the present invention, the optical filter is installed on the front surface of the display. For example, the front surface of the plasma display cuts near infrared rays and electromagnetic waves generated from the display and reflects for improving the visibility of the display. A filter that integrates each function such as prevention, improvement of color reproducibility, and further protection of the display is installed. The near-infrared-absorbing pressure-sensitive adhesive sheet of the present invention is suitable for use in the optical filter because it cuts near-infrared rays and adjusts the color tone as necessary, and can bond the functional film or functional layer.

  A glass plate is usually used as the base material of the optical filter. However, in order to reduce the weight and increase the image quality, it is also possible to use a direct attachment filter that is directly attached to the plasma display panel without using a glass plate. is there. The near-infrared absorbing pressure-sensitive adhesive sheet of the present invention can also be suitably used as a directly attached filter.

  Next, examples and comparative examples of the present invention will be shown. The characteristic value measurement method and effect evaluation method used in the present invention are as follows.

<Transmissivity>
Using a spectrophotometer (UV-3150 model manufactured by Shimadzu Corporation), measurement was performed in the wavelength range of 300 nm to 1200 nm, and the visible light range was 550 nm, the near infrared range was 850 nm, and the transmittance of 950 nm was evaluated. Moreover, the transmittance | permeability of 590 nm was evaluated as an evaluation at the time of adding the compound which cuts neon light.

<Haze>
The turbidity meter (Nippon Denshoku Industries make, NDH-2000) was used, and it evaluated according to JISK7105. 1.0% or less was considered good.

<Adhesive strength>
The near-infrared absorbing adhesive sheet prepared as described below was cut to a width of 25 mm, bonded to a glass plate, left for 30 minutes in an environment of 23 ° C. and 50% RH, and then used with Shimadzu Autograph AGS-1kNG. Then, the adhesive sheet was peeled off from the glass plate at a rate of 300 mm / min in the 180 ° C. direction, and the adhesive force at that time was measured.

<Antistatic performance>
Using a high resistivity meter (Hiresta UP MCP-HT450, manufactured by Mitsubishi Chemical Corporation), the surface resistance values were compared at an applied voltage of 500 V and a measurement time of 10 seconds.

<Heat and heat resistance>
The pressure-sensitive adhesive sheet sample whose transmittance was measured was left in an atmosphere of 60 ° C. and 90% RH for 500 hours, and then the near-infrared transmittance (850 nm, 950 nm) was evaluated, and the difference between before and after the test was compared.

Example 1
An adhesive resin and its solution were prepared as follows.

  Into a nitrogen-substituted reaction vessel, n-butyl acrylate [95 parts by mass], acrylic acid [5 parts by mass], ethyl acetate [150 parts by mass], and benzoyl peroxide [0.1 parts by mass] After reacting for 6 hours while heating and stirring, the temperature was raised to 80 ° C. and reacted for 1 hour. After the reaction, the unreacted product was removed, and the reaction product was diluted with a mixed solvent of toluene / 2-butanone (50/50; mass ratio) to prepare an adhesive resin solution A having a solid content concentration of 18% by mass.

  Next, a methacrylic ester resin and a solution for improving the dispersibility and durability of the near-infrared absorbing compound were prepared as follows.

  Into a reaction vessel purged with nitrogen, n-butyl methacrylate [50 parts by mass], methyl methacrylate [50 parts by mass], ethyl acetate [150 parts by mass], and benzoyl peroxide [0.1 parts by mass] were charged, and the temperature reached 70 ° C. After reacting for 6 hours while heating and stirring, the temperature was raised to 80 ° C. and the reaction was performed for 1 hour. After the reaction, unreacted substances are removed, the reaction product is dissolved in a mixed solvent of toluene / 2-butanone (50/50; mass ratio), and a methacrylic ester resin solution A having a solid content concentration of 14% by mass is obtained. Produced.

Next, the coating liquid A was prepared at the following mass ratio, and then coated on a polyester film (manufactured by Toyobo Co., Ltd., trade name Cosmo Shine A4100, thickness 100 μm) using an applicator (manufactured by Tester Sangyo). After coating, the film was dried in a dry oven (trade name: DS64, manufactured by Yamato Kagaku) at 120 ° C. for 1 minute and 30 seconds to prepare a near-infrared absorbing adhesive sheet. The coating amount of the formed adhesive layer was 25 g / m ² .

(Coating liquid A)
The materials of the coating solution were mixed at the following mass ratio and stirred for 30 minutes or more.
-Adhesive resin solution A 85.6 parts by mass-Methacrylate resin solution A 12.2 parts by mass-Cross-linking agent 0.0856 parts by mass (product name: Coronate L, manufactured by Nippon Polyurethane Industry)
-Diimonium salt compound 0.205 parts by mass (Nippon Carlit, product name CIR-RL)
-Phthalocyanine compound 0.0597 parts by mass (made by Nippon Shokubai, trade name IR-12)
-Phthalocyanine compound 0.0691 parts by mass (Nippon Shokubai, trade name IR-14)
-Ionic liquid 1.74 parts by mass (1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl)
Imide)

  The produced adhesive sheet was cut into a predetermined size, and the adhesive strength was measured. Furthermore, it cut out to a suitable magnitude | size and evaluated antistatic property. In addition, a polyester film (trade name Cosmo Shine A4100, 100 μm in thickness, manufactured by Toyobo Co., Ltd.) was bonded to the remaining part, and then cut into an appropriate size to obtain a sample for evaluation.

  When the transmittance of the prepared sample was measured under the above conditions, the transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high, which was 69.7%. Moreover, the haze value was low and good antistatic properties were observed. Further, the evaluated samples were left in an environment of 60 ° C. and 90% RH for 500 hours, and a moisture and heat resistance test was performed. The measured values before and after the test were compared, but there was no significant difference, and good wet heat resistance was shown. The obtained results are shown in Table 1.

Example 2
A coating liquid B was prepared using the adhesive resin solution A used in Example 1, and an adhesive sheet was produced in the same manner as in Example 1. The coating amount of the adhesive layer was 25 g / m ² .

(Coating solution B)
The materials of the coating solution were mixed at the following mass ratio and stirred for 30 minutes or more.
-Adhesive resin solution A 97.77 parts by mass-Crosslinking agent 0.0880 parts by mass (product name: Coronate L, manufactured by Nippon Polyurethane Industry)
-Phthalocyanine compound 0.0827 parts by mass (made by Nippon Shokubai, trade name IR-12)
-Phthalocyanine compound 0.0625 parts by mass (made by Nippon Shokubai, trade name IR-14)
-Phthalocyanine compound 0.0827 parts by mass (made by Nippon Shokubai, trade name TX-EX906B)
-Phthalocyanine compound 0.124 parts by mass (made by Nippon Shokubai, trade name TX-EX910B)
-Ionic liquid 1.79 parts by mass (1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl)
Imide)

  Samples for measurement were prepared in the same manner as in Example 1 and evaluated in the same manner. The transmittance in the near infrared region was sufficiently low and was 10% or less. The transmittance at a wavelength of 550 nm was high and was 51.1%. Further, the haze value was low, and the antistatic property and wet heat resistance were good. The obtained results are shown in Table 1.

Example 3
A coating liquid C was prepared using the adhesive resin solution A used in Example 1, and an adhesive sheet was produced in the same manner as in Example 1. The coating amount of the adhesive layer was 25 g / m ² .

(Coating liquid C)
The materials of the coating solution were mixed at the following mass ratio and stirred for 30 minutes or more.
-Adhesive resin solution A 97.70 parts by mass-Crosslinking agent 0.0879 parts by mass (product name: Coronate L, manufactured by Nippon Polyurethane Industry)
-Phthalocyanine compound 0.0326 parts by mass (Nippon Shokubai, trade name IR-14)
-Phthalocyanine compound 0.137 parts by mass (made by Nippon Shokubai, trade name TX-EX910B)
・ Metal complex compound 0.253 parts by mass (trade name NKX-1199, manufactured by Hayashibara Biochemical Research Institute)
-Ionic liquid 1.79 parts by mass (1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl)
Imide)

  Samples for measurement were prepared and evaluated in the same manner as in Example 1. The transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high and was 59.6%. Moreover, the haze value was low, and good antistatic properties and wet heat resistance were observed. The obtained results are shown in Table 1.

Example 4
A sample was prepared and evaluated in the same manner as in Example 1 except that the ionic liquid used in the coating liquid A in Example 1 was changed to 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide. It was. As a result, the transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high and was 69.0%. Moreover, the haze value was low, and good antistatic properties and wet heat resistance were observed. The obtained results are shown in Table 1.

Example 5
A sample was prepared and evaluated in the same manner as in Example 1 except that the ionic liquid used in the coating liquid A in Example 1 was changed to 1-ethyl-3-methylimidazolium hexafluorophosphate. As a result, the transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high, 69.4%. Moreover, the haze value was low, and good antistatic properties and wet heat resistance were observed. The obtained results are shown in Table 1.

Example 6
A coating solution D obtained by adding a compound that cuts neon light to the coating solution A used in Example 1 was prepared, and an adhesive sheet was produced in the same manner as in Example 1. The coating amount of the adhesive layer was 25 g / m ² .

(Coating solution D)
The materials of the coating solution were mixed at the following mass ratio and stirred for 30 minutes or more.
-Adhesive resin solution A 85.6 parts by mass-Methacrylate resin solution A 12.2 parts by mass-Cross-linking agent 0.0856 parts by mass (product name: Coronate L, manufactured by Nippon Polyurethane Industry)
-Diimonium salt compound 0.205 parts by mass (Nippon Carlit, product name CIR-RL)
-Phthalocyanine compound 0.0597 parts by mass (made by Nippon Shokubai, trade name IR-12)
-Phthalocyanine compound 0.0691 parts by mass (Nippon Shokubai, trade name IR-14)
-Neon light cut compound 0.0397 parts by mass (made by Yamada Chemical Co., Ltd., trade name TAP-2)
-Ionic liquid 1.74 parts by mass (1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl)
Imide)

  Samples for measurement were prepared and evaluated in the same manner as in Example 1. The transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high, which was 55.1%. Further, an absorption peak appeared in the vicinity of a wavelength of 590 nm, and the transmittance at a wavelength of 590 nm was 27.2%. Moreover, the haze value was low, and good antistatic properties and wet heat resistance were observed. The obtained results are shown in Table 1.

Example 7
When coating in Example 1, a sample was prepared in the same manner as in Example 1 except that the polyester film used was antireflective processed on one side (Nippon Yushi Co., Ltd., trade name: Realik, thickness: 100 μm). did. The polyester film was coated on the surface opposite to the antireflective surface. Furthermore, as a result of evaluating in the same manner as in Example 1, the transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high and was 74.0%. Further, the haze value was low, and the antistatic property and wet heat resistance were good. The obtained results are shown in Table 1.

Comparative Example 1
Except for the ionic liquid contained in the coating liquid A used in Example 1, a coating liquid E having the same composition ratio as that of the coating liquid A was prepared, and the adhesive sheet was used in the same manner as in Example 1 using the coating liquid E. Was made. The coating amount of the formed adhesive layer was 25 g / m ² .

(Coating liquid E)
The materials of the coating solution were mixed at the following mass ratio and stirred for 30 minutes or more.
-Adhesive resin solution A 87.2 parts by mass-Methacrylate ester resin solution A 12.4 parts by mass-Crosslinking agent 0.0872 parts by mass (trade name Coronate L, manufactured by Nippon Polyurethane Industry)
-Diimonium salt compound 0.209 parts by mass (Nippon Carlit, product name CIR-RL)
-Phthalocyanine compound 0.0608 parts by mass (made by Nippon Shokubai, trade name IR-12)
-Phthalocyanine compound 0.0704 parts by mass (made by Nippon Shokubai, trade name IR-14)

  Samples for measurement were prepared and evaluated in the same manner as in Example 1. Although there was no difference from Example 1 regarding the transmittance in the near infrared region, the transmittance at a wavelength of 550 nm, the haze value, and the heat and humidity resistance, the antistatic property was inferior to that of Example 1. The obtained results are shown in Table 1.

Comparative Example 2
A pressure-sensitive adhesive sheet was prepared and evaluated in the same manner as in Example 1 except that an alkyl phosphate type antistatic agent was used instead of the ionic liquid of the coating liquid A used in Example 1. The coating amount of the adhesive layer was 25 g / m ² . Further, a measurement sample was prepared and evaluated in the same manner as in Example 1. The transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high, 69.2%. Moreover, the haze value was low and good antistatic properties were observed. However, after the moisture and heat resistance test, the transmittance in the near infrared region was 10% or more, and the moisture and heat resistance was insufficient. The obtained results are shown in Table 1.

Comparative Example 3
A pressure-sensitive adhesive sheet was prepared and evaluated in the same manner as in Example 1 except that zinc oxide fine particles were used instead of the ionic liquid of the coating liquid A used in Example 1. The transmittance in the near infrared region was sufficiently low and was 10% or less. Further, the transmittance at a wavelength of 550 nm was high, 69.2%. Moreover, although good antistatic property was seen, the haze value was 5.0% and the transparency was lowered. The obtained results are shown in Table 1.

Comparative Example 4
A pressure-sensitive adhesive sheet was prepared and evaluated in the same manner as in Example 1 except that the coating liquid F except the near-infrared absorbing compound of the coating liquid A used in Example 1 was prepared and the coating liquid F was used. The coating amount of the adhesive layer was 25 g / m ² .

(Coating fluid F)
The materials of the coating solution were mixed at the following mass ratio and stirred for 30 minutes or more.
-Adhesive resin solution A 85.9 parts by mass-Methacrylate resin solution A 12.2 parts by mass-Crosslinking agent 0.0859 parts by mass (product name: Coronate L, manufactured by Nippon Polyurethane Industry)
-Ionic liquid 1.75 parts by mass (1-butyl-3-methylpyridinium bis (trifluoromethanesulfonyl)
Imide)

  A sample for measurement was prepared and evaluated in the same manner as in Example 1. The transmittance in the near infrared region was 85% or more, and there was almost no absorption in the near infrared region. The obtained results are shown in Table 1.

  The near-infrared absorbing pressure-sensitive adhesive sheet of the present invention has high near-infrared absorbing ability and visible transmittance, and is not only adhesive, but also excellent in antistatic properties, moist heat resistance, and transparency. It is possible not only to prevent malfunction of precision equipment using the remote control used, but also to reduce the cost by simplifying the filter manufacturing process, to improve the yield by preventing the attachment of foreign matters such as dust and dust, and to reduce the change in color tone due to wet heat. Therefore, it is suitable as an optical filter used in an image display device such as a plasma display, a liquid crystal display, an electroluminescence display, a fluorescent display tube, and a field emission display.

Claims (7)

  A near-infrared-absorbing pressure-sensitive adhesive sheet comprising a composition comprising a near-infrared-absorbing compound and an adhesive resin as main components, wherein the composition contains an ionic liquid.   The near-infrared absorbing pressure-sensitive adhesive sheet according to claim 1, wherein the near-infrared absorbing compound contains any one of a diimonium salt compound, a phthalocyanine compound, and a metal complex compound.   The near-infrared-absorbing pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the ionic liquid is contained in an amount of 0.1% by mass to 30.0% by mass with respect to the adhesive resin component. The ionic liquid is PF ₆ ⁻ , ClO ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , (CN) ₂ N ^−. , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) (CF ₃ CO) N ⁻ , as an anion. Near-infrared absorbing adhesive sheet. The near-infrared-absorbing pressure-sensitive adhesive sheet according to claim 1, wherein the ionic liquid contains (CF ₃ SO ₂ ) ₂ N ⁻ as an anion.   The near-infrared absorbing adhesive sheet according to claim 1, wherein the adhesive resin is an acrylic resin.   The near-infrared absorbing adhesive sheet according to claim 1, wherein the near-infrared absorbing adhesive sheet is installed on the front surface of the display.