JP2010002825A - Antireflection material having near-infrared ray absorptivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflection material which has near-infrared absorptivity by using tungsten oxide particles as a near-infrared absorber, has excellent transparency, does not show blue reflection color hue and is used as a front filter for an image display apparatus. <P>SOLUTION: The antireflection material is constituted by successively laminating, on one surface of a base material, a near-infrared absorption layer which contains a resin and the near-infrared absorber, consisting of tungsten oxide compound particles and a layer which more strongly reflects light of a wavelength region which is longer than the light of a region from violet to blue and which has a refractive index lower than that of the near-infrared absorption layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antireflection material, and more particularly to an antireflection material having a near-infrared absorbing ability that is particularly excellent as a filter for a plasma display panel (hereinafter also referred to as “PDP”).

In recent years, PDPs have attracted attention as displays become larger and thinner. PDPs are known to emit near-infrared rays, which may adversely affect nearby electronic devices such as cordless phones and video decks that use near-infrared remote control devices, and may hinder normal operation. It was. Therefore, various near-infrared filters for PDPs have been proposed. Particularly, a near-infrared absorbing material having a large near-infrared absorbing power and excellent durability, a tungsten oxide fine particle having an average dispersed particle size of 800 nm or less and / or Alternatively, a near infrared absorption filter using composite tungsten oxide fine particles has been proposed (see Patent Document 1).
Furthermore, an antireflection material has been proposed in which a low refractive index layer is laminated thereon to provide an antireflection function (see Patent Documents 1 and 2). However, only those inventions in which the low refractive index layer is considered to prevent reflection over the entire visible light wavelength range are disclosed in these.

JP 2006-154516 A JP 2006-201443 A

When tungsten oxide compound particles are used as a near-infrared absorbing agent, in order to ensure sufficient transparency in the visible light wavelength band, the tungsten oxide compound particles need to have a particle size of 100 nm or less. In that case, the hue becomes bluish due to Rayleigh scattering of the particles (the scattering cross section is inversely proportional to the fourth power of the wavelength; the short wavelength blue light is reflected more strongly). This is inconvenient for use in a front filter for an image display device, because it prevents the hue of an image from being reproduced.
Therefore, the object of the present invention is to use tungsten oxide compound particles as a near-infrared absorber, which has excellent transparency and a near-infrared absorptivity used for a front filter for an image display device, in which the reflection color does not show blue. It is providing the antireflection material which has this.

As a result of intensive studies, the present inventors have found that an anti-reflective material in which a tungsten oxide compound particle-containing near-infrared absorbing layer and a low refractive index layer are laminated on a substrate, the interference color of the low refractive index layer (antireflection) By setting the residual reflection color during processing to visible light in the longer wavelength range than the band from purple to blue, and mixing with the scattering color of the tungsten oxide compound particles, it is achromatic, so The present inventors have found that blue can be reduced and completed the present invention.
That is, the present invention provides a near-infrared absorbing layer H1 containing a near-infrared absorber composed of a resin and tungsten oxide compound particles on one surface of a base material, and visible light having a wavelength longer than the band from purple to blue. The antireflective material in which the layer L1 having a refractive index lower than that of the near-infrared absorbing layer H1 is sequentially laminated is provided.

  According to the present invention, the tungsten oxide compound particles are used as a near-infrared absorber, and the near-infrared absorbing ability used in the front filter for an image display device is excellent in transparency and the reflection color does not show blue. An antireflective material can be provided.

The antireflective material of the present invention has a near-infrared absorbing layer H1 containing a near-infrared absorber composed of a resin and tungsten oxide compound particles on one surface of the substrate, and a longer wavelength region than a band from purple to blue. A layer L1 having a refractive index lower than that of the near-infrared absorbing layer H1 that reflects visible light more strongly is sequentially laminated.
There is no restriction | limiting in particular as a base material, A transparent thing can be suitably selected and used from a well-known thing as a base material of an antireflection material conventionally, ie, a material, from a plastic or glass. Moreover, as a form of a base material, various forms of a film, a sheet, or a plate can be used, and the thing of the range of about 20-5000 micrometers is used as thickness.

As described above, the plastic substrate can be used in any form of a film, a sheet, or a plate, and specific materials include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyethylene, Polyolefin film such as polypropylene, polymethylpentene, cycloolefin resin, norbornene resin; polycarbonate film; acrylic resin film such as poly (meth) methyl acrylate and poly (meth) ethyl acrylate; polystyrene film; polyvinyl chloride, poly Vinyl chloride films such as vinylidene chloride; Cellulosic films such as cellophane, diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate; polyvinyl acetate Vinyl acetate resin films such as ethylene and vinyl acetate copolymers; polysulfone films such as polysulfone and polyethersulfone; polyimide films such as polyimide and polyetherimide; polyamide films; polyvinyl alcohol films; Examples thereof include a film; a fluororesin film; a polyvinyl butyral film.
Glass is mainly used in the form of a plate, and specific materials include soda glass, potash glass, quartz glass, borosilicate glass, and the like.
Among these, from the viewpoint of transparency, surface smoothness, mechanical strength and the like, a film having a thickness of about 50 to 200 μm made of a polyester resin is preferable, and a polyethylene terephthalate film is particularly preferable.
A glass substrate is also preferable from the viewpoint of optical properties and mechanical properties.

The substrate may be transparent or translucent, and may be colored, but is preferably colorless and transparent for PDP.
The thickness of these base materials is not particularly limited, and those having a thickness of about 20 to 5000 μm are appropriately selected as described above according to the usage form. In the case of film or sheet form, it is in the range of 25 to 250 μm, preferably 30 to 200 μm, and in the case of plate form, it is in the range of about 1000 to 5000 μm. Moreover, when using the said plastic film as a base material, in order to improve the adhesiveness with the layer provided in the surface, surface treatment is given by the oxidation method, the uneven | corrugated method, etc. on one side or both surfaces as needed. be able to. Examples of the oxidation method include corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment and the like, and examples of the unevenness method include sand blast method and solvent treatment method. Is mentioned. These surface treatment methods are appropriately selected depending on the type of substrate, but in general, the corona discharge treatment method is preferable from the viewpoints of effects and operability.

The near-infrared absorbing layer H1 in the present invention is a near-infrared absorbing layer containing a near-infrared absorber composed of a resin and tungsten oxide compound particles, and is also a high refractive index layer for forming an antireflection layer as will be described later. Moreover, the near-infrared absorbing layer H1 can also function as a hard coat layer by selecting a crosslinked or polymerized (cured) resin as the resin to be used.
The resin used here is not particularly limited as long as it functions as a binder for binding a near infrared absorber composed of tungsten oxide compound particles and can form a near infrared absorption layer on a substrate. And ionizing radiation curable resin, thermosetting resin, thermoplastic resin, and the like. Among these, ionizing radiation curable resins and thermosetting resins are preferable in terms of processability and durability. These resins can be used alone or in combination of two or more.
Further, from the viewpoint of being able to be cured in a very short irradiation time and high production efficiency, an ionizing radiation curable resin is preferable, and an ultraviolet curable resin with a particularly simple apparatus is preferable.

  The ionizing radiation curable resin means a resin that is cured by crosslinking or polymerization reaction when irradiated with electromagnetic waves or charged particle beams such as ultraviolet rays or electron beams. Examples of such an ionizing radiation curable resin include an ionizing radiation polymerizable prepolymer and / or an ionizing radiation polymerizable monomer.

Examples of the ionizing radiation-polymerizable prepolymer (also referred to as oligomer) include prepolymers having radically polymerizable unsaturated groups in the molecule, such as polyester (meth) acrylate, epoxy (meth) acrylate, and urethane (meth). Examples include acrylate-based, polyol (meth) acrylate-based, triazine (meth) acrylate-based (meth) acrylate-based prepolymers, unsaturated polyester-based prepolymers, and the like. Here, “(meth) acrylate” means “acrylate or methacrylate”. Examples of the cationic polymerizable prepolymer include novolac type epoxy resin prepolymers and aromatic vinyl ether resin prepolymers. Examples of the polythiol-based prepolymer include trimethylolpropane trithioglycolate prepolymer and pentaerythritol tetrathioglycolate prepolymer.
Next, as the ionizing radiation polymerizable monomer (also referred to as a monomer), a polyfunctional (meth) acrylate is preferable. Specifically, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate , Dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (me ) Acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) Acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (Meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, etc. It is below. These ionizing radiation polymerizable prepolymers and ionizing radiation polymerizable monomers are used alone, in combination of two or more selected from the prepolymers, in combination of two or more selected from the monomers, or One or more selected from the prepolymers and one or more selected from the monomers may be used in combination.

When an ultraviolet curable resin is used as the ionizing radiation curable resin, it is desirable to add about 0.1 to 5 parts by mass of the photopolymerization initiator with respect to 100 parts by mass of the resin. The initiator for photopolymerization can be appropriately selected from those conventionally used and is not particularly limited. For example, for a polymerizable monomer or polymerizable oligomer having a radically polymerizable unsaturated group in the molecule. Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2 -Phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propane-1 - 4- (2-hydroxyethoxy) phenyl-2 (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4′-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2 -Tertiary butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal It is done.
Examples of the polymerizable oligomer having a cationic polymerizable functional group in the molecule include aromatic sulfonium salts, aromatic diazonium salts, aromatic iodonium salts, metallocene compounds, and benzoin sulfonic acid esters.
Moreover, as a photosensitizer, p-dimethylbenzoic acid ester, tertiary amines, a thiol type sensitizer, etc. can be used, for example.

  Thermosetting resins include phenolic resins, phenol-formalin resins, urea resins, urea-formalin resins, melamine resins, polyester-melamine resins, melamine-formalin resins, alkyd resins, epoxy resins, epoxy-melamine resins, unsaturated polyesters. Examples thereof include resins, polyimide resins, acrylic resins, polyurethane resins, and general-purpose two-component curable acrylic resins (acrylic polyol cured products).

As the near-infrared absorber used for the near-infrared absorbing layer H1 in the present invention, a tungsten oxide compound represented by the following general formula (I) is used because it has a high near-infrared absorptivity and a high visible light transmittance. use.
MxWyOz (I)
Here, the M element is at least one selected from the group consisting of Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe, and Sn, W represents tungsten, and O represents oxygen. .
Of the tungsten oxide compounds represented by the above general formula (I), cesium-containing tungsten oxide in which the M element is represented by Cs is particularly preferable because of its high near-infrared absorptivity.

In addition, in the above general formula (I), the added amount of the M element satisfies the relationship of 0.001 ≦ x / y ≦ 1.1 as the value of x / y based on the tungsten content. In particular, x / y is preferably in the vicinity of 0.33 from the viewpoint of suitable near infrared absorption ability. Further, when x / y is around 0.33, a hexagonal crystal structure is easily obtained, and the use of this crystal structure is also preferable in terms of durability.
The oxygen content in the general formula (I) preferably satisfies the relationship of 2.2 ≦ z / y ≦ 3.0 as the value of z / y based on the content of tungsten. More specifically, Cs _0.33 WO ₃ , Rb _0.33 WO ₃ , K _0.33 WO ₃ , Ba _0.33 WO _{3 and the} like can be mentioned.
The said tungsten oxide type compound may be used individually by 1 type, or can also use 2 or more types together.

It is important that the tungsten oxide compound particles used in the present invention have an average particle diameter of 40 to 100 nm in order to ensure sufficient transparency in the visible light wavelength band. When the average particle size is less than 40 nm, the near infrared ray absorbing ability is insufficient. On the other hand, when the average particle size exceeds 100 nm, the transparency is lowered. In order to exhibit more preferable near infrared absorption performance, the average particle size is preferably 40 to 80 nm, and more preferably 40 to 60 nm.
In addition, the measurement of the average particle diameter in the present invention is obtained by taking an image with a transmission electron microscope, randomly extracting, for example, 50 near-infrared absorbers, measuring the particle diameter, and averaging these. . Moreover, when the shape of particle | grains is not spherical, it defines as what was calculated by measuring a major axis.

Content in the near-infrared absorption layer H1 of the near-infrared absorbing agent, when expressed in content per unit area is preferably in the range of ^{0.01g / m 2 ~10g / m 2} . If the content is 0.01 g / m ² or more, a sufficient near-infrared absorption effect appears, and if it is 10 g / m ² or less, a sufficient amount of visible light can be transmitted.

  In the present invention, the tungsten oxide compound particles are used as the near-infrared absorber as described above, but other near-infrared absorptions such as organic and metal complexes are within the scope of the effects of the present invention. An agent can also be used in combination. For example, diimonium compounds, aluminum compounds, phthalocyanine compounds, organometallic complexes, cyanine compounds, azo compounds, polymethine compounds, quinone compounds, diphenylmethane compounds, triphenylmethane compounds, and the like can be used in combination.

The layer H1 in the present invention may further contain metal oxide fine particles in addition to the formation of the low refractive index layer L1 in order to more reliably reduce the bluish color due to the tungsten oxide compound. preferable. The metal oxide fine particles are not limited in the material itself as long as the effect of the present invention is achieved, but those having a small difference in refractive index from the near infrared absorber are preferable, particularly zirconium oxide and titanium oxide. Are preferable. For example, the refractive index of Cs _0.33 WO ₃ (cesium-containing tungsten oxide) is 2.5 to 2.6, while the refractive indexes of zirconium oxide and titanium oxide are 2.0 to 2.2 and 2.2 to 2.2, respectively. Since it is the range of 2.7, the refractive index difference with the said near-infrared absorber can be made into about 0.3 or less. These metal oxide fine particles can be used alone or in combination of two or more.

In the present invention, when the near-infrared absorbing layer H1 contains metal oxide fine particles, the average particle size is preferably 5 to 30 nm. If the average particle size is less than 5 nm, the blueness of the transmitted color tone cannot be reduced, and if the average particle size exceeds 30 nm, the blue color of the transmitted color tone cannot be reduced and white turbidity may occur. From the viewpoint of achieving the effect of the present invention at a higher level, the average particle diameter of the metal oxide fine particles is more preferably in the range of 10 to 20 nm.
The shape of the metal fine particles is not particularly limited, but usually a spherical shape is used.
In addition, the average particle diameter of metal oxide fine particles is measured by a method using a transmission electron microscope in the same manner as the near infrared absorber.

  The content of the metal oxide fine particles in the near-infrared absorbing layer H1 is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the tungsten oxide compound. When the amount is 50 parts by mass or more, the bluish color of the transmitted color tone can be eliminated, while when it is 200 parts by mass or less, the problem of cloudiness does not occur.

  The thickness of the near-infrared absorbing layer H1 of the present invention is preferably in the range of 2 to 20 μm when formed by various coating methods. When the thickness is 2 μm or more, near-infrared rays can be absorbed sufficiently, and when the thickness is 20 μm or less, it can be formed by a normal coating method. From the above viewpoint, the thickness of the near-infrared absorbing layer H1 is more preferably in the range of 3 to 15 μm, particularly preferably in the range of 5 to 10 μm. In addition, the near-infrared absorption efficiency can be controlled by changing the thickness of the near-infrared absorption layer H1.

In the present invention, the near-infrared absorbing layer H1 is preferably formed by a method in which a near-infrared absorbing layer-forming coating solution is applied on a substrate, dried and cured to form a near-infrared absorbing layer.
The coating solution for forming a near-infrared absorbing layer in the present invention includes the resin, a tungsten oxide compound, the metal oxide fine particles added as required, and the photopolymerization used as required in an appropriate solvent as necessary. It can prepare by adding an initiator and the additive added as needed in a predetermined ratio, and making it melt | dissolve or disperse | distribute.
In the present invention, it is important to disperse the tungsten oxide compound particles and the metal oxide fine particles added as required in a solvent. Examples of the dispersion method include various methods such as a dry method and a wet method. In the present invention, a wet method is effective, and specific examples include a ball mill, a sand mill, a medium stirring mill, and ultrasonic irradiation. In addition, when dispersing the tungsten oxide compound particles, which are near infrared absorbers, the near infrared absorber can be stably dispersed and held in the liquid by selecting a solvent, selecting a dispersant, and adjusting the pH. . Various dispersants can be selected depending on the compatibility with the solvent and binder used.

Examples of the solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol, butanol, and 1-methoxy. Examples include alcohols such as 2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, methyl isobutyl ketone, and isophorone; esters such as ethyl acetate and butyl acetate; cellosolv solvents such as ethyl cellosolve, and water.
Moreover, as various additives which can be added here, antioxidant, a ultraviolet absorber, a light stabilizer, a leveling agent, an antifoamer etc. are mentioned, for example.
The concentration and viscosity of the coating solution are not particularly limited as long as the concentration and viscosity can be coated.

As a method for applying the coating liquid to the substrate, a conventionally known method such as a bar coating method, a knife coating method, a roll coating method, a gravure roll coating method, a blade coating method, or a die coating method can be used. . After coating and forming a coating film, it is dried. When the resin is an ionizing radiation curable resin, it is irradiated with ionizing radiation, or when the resin is a thermosetting resin, it is heated. Then, the near-infrared absorbing layer is formed by curing the coating film.
Examples of the ionizing radiation include electromagnetic waves such as ultraviolet rays, visible rays, X-rays and γ rays, and charged particle beams such as electron beams, α rays, and various ion rays. It is an electron beam. Ultraviolet rays are obtained with a high-pressure mercury lamp, a plasma-excited mercury lamp, a black light (ultraviolet radiation fluorescent lamp), a xenon lamp, or the like. On the other hand, the electron beam is obtained by an electron beam accelerator or the like. Among these ionizing radiations, ultraviolet rays can be irradiated into the atmosphere, which is preferable in that a simple irradiation device can be used. In addition, when using an electron beam, there exists an advantage that a cured film can be obtained, without adding a polymerization initiator.

  Since the near-infrared absorbing layer H1 in the present invention contains tungsten oxide-based particles that are fine particles with a high refractive index (the refractive index of cesium-containing tungsten oxide is about 2.5), it constitutes a high refractive index layer and has the following low By stacking the refractive index layer L1, an antireflection layer can be formed.

Next, the low refractive index layer L1 constituting the antireflection material of the present invention will be described.
The low refractive index layer L1 in the present invention is a layer having a lower refractive index than the near-infrared absorbing layer H1 that reflects visible light in a longer wavelength region more strongly than a band from violet to blue, and the near-infrared absorbing layer H1. Laminate on top. Here, “reflects the visible light in a longer wavelength region more strongly than the band from purple to blue” means that the spectral reflectance distribution (spectrum) of the reflected light from the low refractive index layer L1 is relative. In addition, it means that the reflectance in the long wavelength region (green to yellow to orange to red) is larger than the reflectance in the band from purple to blue.
That is, in the laminate of transparent substrate / tungsten oxide-based particle-containing near infrared absorption / high refractive index layer H1 / low refractive index layer L1, interference color of the low refractive index layer L1 (residual reflected color during antireflection treatment) Is set to visible light in a longer wavelength range than the band from purple to blue (partial band or all band of green to yellow to orange to red band), and light in the band from purple to blue of the tungsten oxide particles Blue color is reduced by achromatic color mixing with scattered colors containing a large amount of.
The interference color of the low refractive index layer L1 (residual reflected color during antireflection treatment) is set to visible light (partial band or entire band of green to yellow to orange to red) in a longer wavelength range than the blue band. This means that the minimum reflectance wavelength λ ₁ of the laminate is set to 380 to 600 nm (any wavelength in the range of purple to blue to green to orange), and can be performed, for example, as follows.

As shown in FIG. 1A, the reflected color of the near-infrared absorption and high refractive index layer 10 in which cesium-containing tungsten oxide particles (particle size of about 70 nm) are dispersed in the resin layer is bluish due to Rayleigh scattering. As shown in (B), it exhibits a spectral reflectance R (λ) _{10 in} which the reflectance increases as the wavelength becomes shorter.
On the other hand, in order to construct an anti-reflection film that reflects a large amount of red light (the anti-reflection performance decreases relative to red light), as shown in FIG. A first low refractive index layer 20 (refractive index n _L1 , thickness h _L1 ) is laminated on the layer 10 (refractive index n _H1 ). At this time, the reflection minimum wavelength λ ₁ is adjacent to the red band, and is a well-known theoretical formula in the field of the antireflection film in order to make the shorter wavelength band green to orange (wavelength of about 500 to 600 nm). Using formulas 1 and 2, the refractive index n _L1 and thickness h _L1 of the first low refractive index layer 20 are selected such that λ ₁ is about 500 to 600 nm.

In this case, the spectral reflectance R (λ) _{10 + 20} of the laminated body is purely due to light interference, ignoring the contribution to the spectral characteristics due to Rayleigh scattering of the cesium-containing tungsten oxide particles (FIG. 1A). If only the contribution of the antireflection effect is illustrated, the principle is as shown in FIG. That is, in addition to the red region, light in the blue to violet region is also reflected, and the reflected light is not pure red, but a violet color. However, this is still practically sufficient as a reduction in blue taste (based on cesium-containing tungsten oxide particles).

The antireflective material of the present invention is obtained by laminating a low-refractive index layer L1 on a near-infrared absorbing and high-refractive index layer H1 on one surface of a substrate, but the remaining blue in FIG. In order to reduce the reflected light in the violet region and not attenuate the reflected light in the red region, the reflected minimum wavelength λ ₂ is adjacent to the λ ₁ (green to orange region) as shown in FIG. Further, it is preferable to additionally laminate an antireflection film having a shorter wavelength range of green to purple (wavelength of about 380 to 500 nm).
However, since it is necessary to form a layer having a lower refractive index than the layer immediately below the antireflection film, it is not formed directly on the first low refractive index layer 20, but as shown in FIG. After forming the second high refractive index layer 30 (refractive index n _H2 ) again, it is necessary to laminate the second low refractive index layer 40 (refractive index n _L2 , thickness h _L2 ) immediately above it.
Each parameter at that time is obtained using Equation 3 and Equation 4. That is, the refractive index n _L2 and thickness h _L2 of the second low refractive index layer 40 are selected so that λ ₂ is about 380 to 500 nm.

Then, as shown in FIG. 3B, the reflection minimum wavelength λ ₂ is shifted to the short wavelength side as compared with the case of the laminated body of the near infrared absorption / high refractive index layer 10 / first low refractive index layer 20 described above. Spectral reflectance R (λ) _{30 + 40} can be obtained. However, FIG. 3B purely illustrates only the contribution of the antireflection effect due to optical interference of the second low refractive index layer 40 and the second high refractive index layer 30.
Then, a laminate of the above layers (near infrared absorption and high refractive index layer 10 / first low refractive index layer 20 / second high refractive index layer 30 / second low refractive index layer 40; FIG. 4 (A)). When it is made, the total spectral reflectance characteristic R (λ) _{10 + 20 + 30 + 40} is as shown in FIG. 4B in the case of the near infrared absorption and high refractive index layer 10 only in FIG. R (λ) ₁₀ ) becomes relatively flat and achromatic, and the object of the present invention is better achieved. Of course, the reflectance itself is reduced over the entire visible light band, and a good antireflection effect is also achieved.
In addition, in the above, the laminated structure of the high refractive index layer and the low refractive index layer including the near infrared absorption and high refractive index layer 10 is one set (FIG. 2A) and two sets (FIG. 3A). ) An example of formation was given. However, if it is necessary to neutralize the blue color attributed to the near-infrared absorption and high-refractive-index layer 10, the laminated structure of the high-refractive-index layer and the low-refractive-index layer is based on the same design procedure as above. In addition, three or more sets can be combined (the illustrations and detailed examples are omitted).

  That is, the present invention is not limited to the form in which the low refractive index layer L1 is laminated on the near infrared absorption and high refractive index layer H1 (the first form of the antireflection material of the present invention), but the uppermost layer is a low refractive index layer. Thus, a form in which two or more pairs of high refractive index layer / low refractive index layer are laminated (second form of the antireflection material of the present invention) is also provided as a preferred aspect.

As a material constituting the low refractive index layer, silicon oxide, fluoride, fluorine-containing resin or the like is used. Specifically, SiO ₂ (refractive index n = 1.45), MgF ₂ (refractive index n = 1). .38), LiF (refractive index n = 1.36), NaF (refractive index n = 1.33), CaF ₂ (refractive index n = 1.44), 3NaF · AlF ₃ (refractive index n = 1.4). ), AlF ₃ (refractive index n = 1.37), Na ₃ AlF ₆ (refractive index n = 1.33), and the like. In the present invention, a material in which these inorganic materials are finely divided and dispersed in a binder resin such as a thermosetting resin or ionizing radiation curable resin is preferable in that a low refractive index layer can be easily provided.
As a method for forming the low refractive index layer, first, the material described above is diluted with a solvent, for example, and a low refractive index layer forming material is applied by a wet coating method using spin coating, roll coating, gravure roll coating, etc. After drying, a method of curing the coating film with heat or ionizing radiation (in the case of ultraviolet rays, the above-mentioned photopolymerization initiator is used), or a vapor phase by vacuum deposition, sputtering, plasma CVD, ion plating, etc. By a method, it can be obtained by a method of depositing a low refractive index layer forming material.

  Further, fine particles having voids may be used for the low refractive index layer. Fine particles having voids form a structure in which fine particles are filled with gas and / or a porous structure containing gas, and the occupancy of the gas in the fine particles is increased as compared with the original refractive index of the fine particles. It means a fine particle whose refractive index decreases. A structure (nanoporous structure) in which fine voids or fine bubbles are included or accompanied in at least a part of the inside and / or the surface depending on the form, structure, aggregation state, and dispersion state of the fine particles inside the coating film. Also included are fine particles that can be formed. The fine particles having voids may be either inorganic or organic, and examples thereof include metals, metal oxides, and resins, and preferably silicon oxide (silica) fine particles.

Furthermore, a material in which a sol obtained by dispersing ultrafine silica particles of 5 to 30 nm in water or an organic solvent and a fluorine-based film forming agent can be used. The sol in which the ultrafine silica particles of 5 to 30 nm are dispersed in water or an organic solvent is obtained by a method of dealkalizing alkali metal ions in alkali silicate salt by ion exchange or the like, or neutralizing alkali silicate salt with mineral acid. A known silica sol obtained by condensing active silicic acid known by the method, etc., a known silica sol obtained by condensing alkoxysilane with hydrolysis in an organic solvent in the presence of a basic catalyst, and the above-mentioned An organic solvent-based silica sol (organosilica sol) obtained by substituting water in the aqueous silica sol with an organic solvent by a distillation method or the like is used. These silica sols can be used in both aqueous and organic solvent systems. In producing the organic solvent-based silica sol, it is not necessary to completely replace water with the organic solvent. The silica sol contains solids 0.5 to 50 wt% concentration as SiO _2. Various structures such as a spherical shape, a needle shape, and a plate shape can be used for the structure of the ultrafine silica particles in the silica sol.

The second high refractive index layer 30 in the second form of the antireflection material of the present invention can be formed by the following general method for forming a high refractive index layer.
The high refractive index layer is formed by using a binder resin having a high refractive index in order to increase the refractive index, adding ultrafine particles having a high refractive index to the binder resin, or using these in combination. To do. The refractive index of the high refractive index layer is preferably in the range of 1.55 to 2.70.

  As the resin used for the high refractive index layer, any resin can be used as long as it is transparent, and thermosetting resins, thermoplastic resins, ionizing radiation (including ultraviolet rays) curable resins, and the like can be used. . Thermosetting resins include phenolic resin, melamine resin, polyurethane resin, urea resin, diallyl phthalate resin, guanamine resin, unsaturated polyester resin, aminoalkyd resin, melamine-urea co-condensation resin, silicon resin, polysiloxane resin, etc. A curing agent such as a crosslinking agent and a polymerization initiator, a polymerization accelerator, a solvent, a viscosity modifier and the like can be added to these resins as necessary.

As ultrafine particles having a high refractive index, for example, ZnO (refractive index n = 1.9), TiO ₂ (refractive index n = 2.3 to 2.7), which can also have an ultraviolet shielding effect, Fine particles of CeO ₂ (refractive index n = 1.95), antimony-doped SnO ₂ (refractive index n = 1.95) or antistatic effect, which can prevent dust adhesion Examples thereof include fine particles of ITO (refractive index n = 1.95). Other fine particles include Al ₂ O ₃ (refractive index n = 1.63), La ₂ O ₃ (refractive index n = 1.95), ZrO ₂ (refractive index n = 2.05), Y ₂ O _3. (Refractive index n = 1.87). These fine particles are used singly or in combination, and those in the form of a colloid dispersed in an organic solvent or water are good in terms of dispersibility, and the particle size is 1 to 100 nm, the transparency of the coating film To preferably 5 to 20 nm.
In order to provide the high refractive index layer, the material described above is diluted with a solvent, for example, provided on a substrate by a method such as spin coating, roll coating, or printing, dried, and then subjected to heat or radiation (in the case of ultraviolet rays, the above-mentioned). The photopolymerization initiator may be used for curing.

The antireflection material having near infrared absorption ability of the present invention is provided with an adhesive layer on the other surface of the substrate so that it can be directly or indirectly provided on the surface of an image display device such as a PDP. .
Further, an electromagnetic wave shielding layer, a neon light absorbing layer, an ultraviolet absorbing layer, a toning layer, an impact resistant layer, a microlouver layer (described in Japanese Patent Application Laid-Open No. 2007-272161, etc.) are provided on the image display device side under the antireflection material of the present invention. Etc.) and other functions can be added to the antireflection material of the present invention. Note that the neon light absorbing layer, the ultraviolet absorbing layer, etc. do not necessarily have to be individually provided as layers, and each of the layers constituting the antireflection material of the present invention or the pressure-sensitive adhesive layer may contain the material. Good.

The antireflection material having near-infrared absorption ability of the present invention has both visible light transparency and near-shielding properties, and therefore image display devices such as a plasma display (PDP), a cathode ray tube (CRT) display, and a liquid crystal display (LCD). It is suitable for use, particularly for plasma displays.
In addition, it is installed on the windows of buildings to block infrared rays in sunlight and improve the indoor warming effect, infrared light shielding members for windows, silicon photo diodes of exposure meters, infrared spectrum of photosensitive films An infrared shielding filter for a photographic camera for correcting sensitivity, protective glasses for protecting eyes from infrared rays, and a night vision apparatus using a photosensitive element (silicon photodiode, etc.) having high spectral sensitivity for infrared rays. Infrared shielding filter to protect from intense infrared sources, agricultural sheets to control the growth of crops by absorbing infrared rays that affect plant growth, germination, flowering, fruiting, etc., incandescent bulbs, mercury lamps, Absorbs infrared radiation from lighting fixtures such as fluorescent lamps, and is used for various applications such as infrared cut-off filters for lighting fixtures to prevent temperature rise in indoors, illuminated objects, or the surrounding atmosphere It is a function.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
(Evaluation methods)
(1) Evaluation of reflection color The antireflection material in the form of a film manufactured in each Example and Comparative Example was used on a black acrylic resin plate using a transparent adhesive (CS-9621 manufactured by Nitto Denko Corporation). After pasting, it was held for 30 minutes at 70 ° C. and 0.5 MPa in an autoclave manufactured by Kyoshin Engineering Co., Ltd. After that, it was irradiated with artificial sun rays. The brightness on the acrylic resin plate was 2500 lux. As for the positional relationship between the artificial sun lantern, human beings, and acrylic resin plate, place the acrylic plate horizontally and observe from an angle of 30 degrees diagonally upward (the angle is measured from the normal line of the acrylic resin plate, the same applies hereinafter), and the light is Irradiation was performed from a direction of 45 degrees obliquely above. The reflection color was evaluated by human eyes.
(2) Near-infrared transmittance The light transmittance was measured by a method according to JIS A 5759. The transmittance measurement was performed using a spectrophotometer (“UV3100” manufactured by Shimadzu Corporation) to determine the light transmittance at wavelengths of 850 nm and 1000 nm.

Example 1
(1) Preparation of coating liquid for forming hard coat layer (near infrared absorbing layer) 5 parts by mass of urethane acrylate prepolymer [manufactured by Nihon Gosei Co., Ltd., trade name “UV1700B”], polyester acrylate prepolymer [manufactured by Toagosei Co., Ltd. The name “M9050”] is added to 5 parts by mass as a photopolymerization initiator, 0.4 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone [Ciba Specialty Chemicals, trade name “Irgacure 184”] Next, 55 parts by mass of a cesium-containing tungsten oxide dispersion [manufactured by Sumitomo Metal Mining Co., Ltd., trade name “YMF-01”, a dispersion containing cesium-containing tungsten oxide (containing 33 mol% of cesium and an average particle size of 44 nm with respect to tungsten)] After mixing the solid content), add 10 parts by mass of methyl isobutyl ketone (MIBK) Thus, a coating liquid 1 for forming a hard coat layer (near infrared absorbing layer) in the form of an ultraviolet curable resin composition was prepared.
(2) Preparation of coating solution for forming low refractive index layer 1.95 parts by mass of pentaerythritol triacrylate (PETA), 1-hydroxy-cyclohexyl-phenyl-ketone [Ciba Specialty Chemicals Co., Ltd.] Manufactured, trade name “Irgacure 184”] 0.1 parts by mass, and then treated silica sol-containing solution [fine particles having voids (average particle size 60 nm), silica sol solid content 20% by mass, solvent; methyl isobutyl ketone] 3 parts by mass and a solution containing silica particles [manufactured by Nacalai Tesque, trade name “sicastar”, giant particles (average particle size 100 nm), solid content of silica particles 20% by weight, solvent: methyl isobutyl ketone] After mixing, 83.5 parts by mass of methyl isobutyl ketone is added to the ultraviolet curable resin composition. The coating liquid 1 for forming a low refractive index layer of the state was prepared.
(3) Production of antireflection film As a substrate, a triacetate cellulose (TAC) film having a thickness of 80 μm is prepared, and a hard coat layer forming coating solution containing an ultraviolet curable monomer and a near infrared absorber on the surface of the film. 1 was applied (bar coating) with a wet weight of 20 g / m ² (dry weight of 10 g / m ² ), and then dried at 40 ° C. for 60 seconds to remove the solvent. Thereafter, the coating solution was cured by irradiating with an ultraviolet ray at an irradiation dose of 50 mJ / cm ² using an ultraviolet irradiation device to form a 10 μm thick hard coat layer.
Next, the low refractive index layer coating liquid 1 was applied to the surface of the formed hard coat layer with a dry weight of 0.1 g / m ² (bar coating), and then dried at 40 ° C. for 60 seconds. Then, the antireflection film of Example 1 was manufactured by performing ultraviolet irradiation with an irradiation dose of 200 mJ / cm ² using an ultraviolet irradiation device. The film thickness after curing of the low refractive index layer was 90 nm, and the refractive index was 1.44. The reflectance minimum wavelength of the low refractive index layer formed here is calculated to be 520 nm, and the reflected light is red.
This antireflection film was evaluated by the above method. The evaluation results are shown in Table 1.

Example 2
An antireflection film was produced in the same manner as in Example 1 except that the coating liquid 1 for low refractive index layer was applied at a dry weight of 0.07 g / m ² and the film thickness after curing was changed to 65 nm. The reflectance minimum wavelength of the low refractive index layer formed here is calculated to be 380 nm, and the reflected light is orange. Table 1 shows the results of evaluating the antireflection film in the same manner as in Example 1.

Comparative Example 1
In Example 1, the hard coat layer was the same as in Example 1 except that the hard coat layer forming coating solution 1 was formed from the hard coat layer forming coating solution 2 having a composition in which the cesium-containing tungsten oxide dispersion was not added. Thus, an antireflection film was produced. The minimum reflectance wavelength of the low refractive index layer formed here is calculated to be 520 nm as in Example 1, and the reflected light is red. Table 1 shows the results of evaluating the antireflection film in the same manner as in Example 1.

Comparative Example 2
In Example 1, an antireflection film was produced in the same manner as in Example 1 except that the composition for low refractive index layer 1 was applied at a dry weight of 0.05 g / m ² and the film thickness after curing was changed to 45 nm. . The reflectance minimum wavelength of the low refractive index layer formed here is calculated to be 260 nm, and the reflected light is slightly reddish and colorless. Table 1 shows the results of evaluating the antireflection film in the same manner as in Example 1.

Comparative Example 3
In Example 1, an antireflection film was produced in the same manner as in Example 1 except that the composition for low refractive index layer 1 was applied at a dry weight of 0.15 g / m ² and the film thickness after curing was 140 nm. . The reflectance minimum wavelength of the low refractive index layer formed here is calculated as 810 nm, and the reflected light is slightly bluish and colorless. Table 1 shows the results of evaluating the antireflection film in the same manner as in Example 1.
Comparative Example 4
In Example 1, an antireflection film was produced in the same manner as in Example 1 except that the composition for low refractive index layer 1 was not formed on the hard coat layer. The reflected color was blue. This is presumably due to Rayleigh scattering of the cesium-containing tungsten oxide particles dispersed in the hard coat layer. Table 1 shows the results of evaluating the antireflection film in the same manner as in Example 1.

(A) is a schematic diagram which shows a cesium containing tungsten oxide particle containing near-infrared absorption layer, (B) is a conceptual diagram which shows the spectral reflectance curve of itself. (A) is a schematic diagram which shows the laminated structure which laminated | stacked the 1st low-refractive-index layer on the cesium containing tungsten oxide particle containing near-infrared absorption layer, (B) is a conceptual diagram which shows the spectral reflectance curve of itself. (A) is a schematic diagram which shows the laminated structure which laminated | stacked the 2nd low refractive index layer on the 2nd high refractive index layer, (B) is a conceptual diagram which shows the spectral reflectance curve itself. (A) is a schematic diagram showing a laminated structure in which the laminated structure of FIG. 3 is formed on the laminated structure of FIG. 2, and (B) is a conceptual diagram showing its own spectral reflectance curve.

Explanation of symbols

1 Cesium-containing tungsten oxide particles 2 Resin 10 Near-infrared absorbing layer H1
20 1st low refractive index layer L1
30 2nd high refractive index layer H2
40 Second low refractive index layer L2

Claims (6)

  A near-infrared absorbing layer H1 containing a near-infrared absorber composed of a resin and tungsten oxide compound particles on one surface of the substrate, and more strongly reflect visible light in a longer wavelength range than a band from purple to blue; An antireflection material having near-infrared absorbing ability, wherein a layer L1 having a refractive index lower than that of the near-infrared absorbing layer H1 is sequentially laminated.   The antireflection material according to claim 1, wherein the tungsten oxide compound particles are cesium-containing tungsten oxide particles.   The antireflection material according to claim 1, wherein metal oxide fine particles are contained in the near-infrared absorbing layer H <b> 1.   The antireflection material according to any one of claims 1 to 3, wherein the low refractive index layer L1 contains hollow silica.   The antireflection material according to any one of claims 1 to 4, further comprising an adhesive layer on the other surface of the substrate.   An image display device comprising the antireflection material according to any one of claims 1 to 5 installed on an image display side front surface.

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