WO2008060078A1 - Optical filter for display panel and method of manufacturing same - Google Patents

Optical filter for display panel and method of manufacturing same Download PDF

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Publication number
WO2008060078A1
WO2008060078A1 PCT/KR2007/005668 KR2007005668W WO2008060078A1 WO 2008060078 A1 WO2008060078 A1 WO 2008060078A1 KR 2007005668 W KR2007005668 W KR 2007005668W WO 2008060078 A1 WO2008060078 A1 WO 2008060078A1
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WIPO (PCT)
Prior art keywords
weight
boiling point
layer
optical filter
electromagnetic radiation
Prior art date
Application number
PCT/KR2007/005668
Other languages
French (fr)
Inventor
Seong-Keun Cho
Kyu-Jung Cho
Original Assignee
Dongjin Semichem Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dongjin Semichem Co., Ltd. filed Critical Dongjin Semichem Co., Ltd.
Priority to CN2007800420330A priority Critical patent/CN101558334B/en
Priority to JP2009536170A priority patent/JP5156753B2/en
Publication of WO2008060078A1 publication Critical patent/WO2008060078A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
    • C03C17/006—Surface treatment of glass, not in the form of fibres or filaments, by coating with materials of composite character
    • C03C17/007—Surface treatment of glass, not in the form of fibres or filaments, by coating with materials of composite character containing a dispersed phase, e.g. particles, fibres or flakes, in a continuous phase
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/22—Absorbing filters
    • G02B5/223—Absorbing filters containing organic substances, e.g. dyes, inks or pigments
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
    • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
    • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
    • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
    • C03C17/3668—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having electrical properties
    • C03C17/3676—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having electrical properties specially adapted for use as electromagnetic shield
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/208—Filters for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J11/00—Gas-filled discharge tubes with alternating current induction of the discharge, e.g. alternating current plasma display panels [AC-PDP]; Gas-filled discharge tubes without any main electrode inside the vessel; Gas-filled discharge tubes with at least one main electrode outside the vessel
    • H01J11/10—AC-PDPs with at least one main electrode being out of contact with the plasma
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J11/00—Gas-filled discharge tubes with alternating current induction of the discharge, e.g. alternating current plasma display panels [AC-PDP]; Gas-filled discharge tubes without any main electrode inside the vessel; Gas-filled discharge tubes with at least one main electrode outside the vessel
    • H01J11/20—Constructional details
    • H01J11/34—Vessels, containers or parts thereof, e.g. substrates
    • H01J11/44—Optical arrangements or shielding arrangements, e.g. filters, black matrices, light reflecting means or electromagnetic shielding means
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K9/00—Screening of apparatus or components against electric or magnetic fields
    • H05K9/0073—Shielding materials
    • H05K9/0094—Shielding materials being light-transmitting, e.g. transparent, translucent
    • H05K9/0096—Shielding materials being light-transmitting, e.g. transparent, translucent for television displays, e.g. plasma display panel
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2217/00—Coatings on glass
    • C03C2217/40—Coatings comprising at least one inhomogeneous layer
    • C03C2217/43—Coatings comprising at least one inhomogeneous layer consisting of a dispersed phase in a continuous phase
    • C03C2217/44—Coatings comprising at least one inhomogeneous layer consisting of a dispersed phase in a continuous phase characterized by the composition of the continuous phase
    • C03C2217/445—Organic continuous phases
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2218/00—Methods for coating glass
    • C03C2218/10—Deposition methods
    • C03C2218/11—Deposition methods from solutions or suspensions
    • C03C2218/119—Deposition methods from solutions or suspensions by printing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2211/00—Plasma display panels with alternate current induction of the discharge, e.g. AC-PDPs
    • H01J2211/20—Constructional details
    • H01J2211/34—Vessels, containers or parts thereof, e.g. substrates
    • H01J2211/44—Optical arrangements or shielding arrangements, e.g. filters or lenses
    • H01J2211/446—Electromagnetic shielding means; Antistatic means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2211/00—Plasma display panels with alternate current induction of the discharge, e.g. AC-PDPs
    • H01J2211/20—Constructional details
    • H01J2211/34—Vessels, containers or parts thereof, e.g. substrates
    • H01J2211/44—Optical arrangements or shielding arrangements, e.g. filters or lenses
    • H01J2211/448—Near infrared shielding means

Definitions

  • the present invention relates to an optical filter for a display panel and a method of manufacturing same. More particularly, the preset invention relates to an optical filter for a plasma display panel (PDP), wherein an electromagnetic radiation-shielding layer is directly formed on a glass substrate by a gravure offset method.
  • PDP plasma display panel
  • Display panels are generally equipped with optical filters capable of, among others, blocking electromagnetic radiation and near-infrared rays (NIRs) which cause adverse effects on human health as well as malfunction of electronic equipment.
  • optical filters capable of, among others, blocking electromagnetic radiation and near-infrared rays (NIRs) which cause adverse effects on human health as well as malfunction of electronic equipment.
  • a metal mesh film produced by attaching a copper film on a polyester (e.g., polyethylene terephthalate) substrate film and patterning the copper film by an etching process
  • a fiber mesh film produced by processing a metal fiber or a metal-coated organic fiber on a substrate film and patterning the fiber
  • a multilayered conductive film produced by alternately stacking a metal (Ag) layer and a dielectric layer using a dry coating process such as sputtering.
  • a method of manufacturing an optical filter for a display panel comprising a transparent glass substrate and an electromagnetic radiation-shielding layer, which comprises forming the electromagnetic radiation-shielding layer by printing on the glass substrate a composition comprising (a) 5 to 30% by weight of an acrylate polymer resin, (b) 5 to 35% by weight of a high boiling point solvent having a boiling point of 200 ° C or higher, (c) 5 to 35% by weight of a low boiling point solvent having a boiling point of 200 °C or lower, and (d) 50 to 85% by weight of a metal powder.
  • a composition comprising (a) 5 to 30% by weight of an acrylate polymer resin, (b) 5 to 35% by weight of a high boiling point solvent having a boiling point of 200 ° C or higher, (c) 5 to 35% by weight of a low boiling point solvent having a boiling point of 200 °C or lower, and (d) 50 to 85% by weight of a metal powder.
  • FIG. 1 is a sectional view illustrating the structure of a conventional optical filter
  • FIG. 2 is a sectional view illustrating the structure of an optical filter according to an embodiment of the present invention
  • FIG. 3 is a sectional view illustrating the structure of an optical filter according to another embodiment of the present invention.
  • antireflection layer 110 substrate film 120: adhesive layer 130: glass substrate
  • substrate film 220 adhesive layer
  • adhesive layer 260 glass substrate 270: electromagnetic radiation-shielding layer
  • antireflection layer 310 substrate film
  • electromagnetic radiation-shielding layer 350 adhesive layer
  • an electromagnetic radiation- shielding layer is formed by forming a conductive mesh pattern directly on a glass substrate, e.g., using a gravure offset printing process.
  • the electromagnetic radiation-shielding layer thus-formed has excellent mechanical characteristics (e.g., film adhesion property) and electrical conductivity.
  • the composition for forming the electromagnetic radiation-shielding layer according to the present invention comprises (a) 5 to 30% by weight of an acrylate polymer resin, (b) 5 to 35% by weight of a high boiling point solvent having a boiling point of 200 ° C or higher, (c) 5 to 35% by weight of a low boiling point solvent having a boiling point of 200 "C or lower, and (d) 50 to 85% by weight of a metal powder.
  • the component (a), the acrylate polymer resin may be selected from acrylate polymer resins commonly known in the art.
  • the acrylate polymer resin may be prepared by polymerizing an unsaturated carboxylic acid monomer, an aromatic monomer, and a monomer other than the unsaturated carboxylic acid monomer and the aromatic monomer.
  • the unsaturated carboxylic acid monomer is used to increase the elasticity of the acrylate polymer resin through enhanced hydrogen bonding.
  • the unsaturated carboxylic acid monomer may be acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl acetic acid, or an acid anhydride thereof.
  • the unsaturated carboxylic acid monomer may be used in an amount of 20 to 50% by weight based on the total amount of monomers used in the preparation of the acrylate polymer resin.
  • the content of the unsaturated carboxylic acid monomer is within the above range, it is possible to obtain desired elasticity characteristics of the polymer resin and a desired degree of polymerization, and also to prevent gelation upon polymerization.
  • the aromatic monomer is an acrylic monomer which provides good adhesibility to a glass substrate to allow stable patterning, e.g., styrene, benzylmethacrylate, benzylacrylate, phenylacrylate, phenylmethacrylate, 2- nitrophenylacrylate, 4-nitrophenylacrylate, 2-nitrophenylmethacrylate, 4- nitrophenylmethacrylate, 4-chlorophenylacrylate, etc.
  • the aromatic monomer may be used in an amount of 10 to 30% by weight, more preferably 15 to 20% by weight, based on the total amount of the monomers used in the preparation of the acrylate polymer resin. When the content of the aromatic monomer is within the above range, it is possible to satisfy all of the following requirements: good adhesion of a pattern to a substrate, good directionality of the pattern, stable patterning, and easy removal of organic materials upon sintering.
  • the monomer other than the unsaturated carboxylic acid monomer and the aromatic monomer (hereinafter, referred to simply as "the other monomer"), which is used in the preparation of the acrylate polymer resin, serves to adjust the glass transition temperature and polarity of the acrylate polymer resin.
  • the other monomer may be an acrylic monomer such as 2-hydroxyethyl (meth)acrylate, 2-hydroxyoctyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, or n-butyl acrylate.
  • the other monomer may be used in an amount of 20 to 60% by weight based on the total amount of the monomers used in the preparation of the acrylate polymer resin, which affect the glass transition temperature of the acrylate polymer resin, the heat resistance of the resultant pattern, and the intimate contact of the pattern with a substrate.
  • the acrylate polymer resin may be prepared by polymerizing the unsaturated carboxylic acid monomer, the aromatic monomer, and the other monomer in the presence of a solvent to prevent gelation of these monomers and to provide an appropriate evaporation rate during an offset printing process.
  • the solvent may be propylene glycol monomethylether, dipropylene glycol monomethylether, propylene glycol monomethylether propionate, ethylether propionate, terpineol, propyleneglycol monomethylether acetate, dimethylaminoformaldehyde, methyl ethyl ketone, butylcarbitol, butylcarbitol acetate, ⁇ -butyrolactone, ethyllactate, or a mixture thereof.
  • the acrylate polymer resin obtained by polymerizing the unsaturated carboxylic acid monomer, the aromatic monomer, and the other monomer in the presence of a solvent may have a weight average molecular weight of 10,000 to 100,000, more preferably 20,000 to 50,000.
  • the weight average molecular weight of the acrylate polymer resin is within the above range, the glass transition temperature of the acrylate polymer resin is lowered, and thus, the flowability of the acrylate polymer resin becomes satisfactory for transferring a pattern in a gravure groove to a blanket during an offset printing process, and the delivery of the composition into a gravure groove also becomes satisfactory owing to good elasticity characteristics of the acrylate polymer resin.
  • the acrylate polymer resin is used in an amount of 5 to 30% by weight in the composition according to the present invention. If the content of the acrylate polymer resin is less than 5% by weight, the offset printing process may not be efficiently performed due to the lowered elasticity of the composition. On the other hand, if the content of the acrylate polymer resin exceeds 30% by weight, the electric resistivity of the resultant pattern may increase.
  • the component (b), the high boiling point solvent having a boiling point of 200 °C or higher may be ⁇ -butyrolactone, butylcarbitol acetate, carbitol, methoxymethylether propionate, terpineol, or a mixture thereof.
  • the high boiling point solvent is used in an amount of 5 to 35% by weight in the composition of the present invention. If the content of the high boiling point solvent is less than 5% by weight, the flowability of the composition becomes unsatisfactory for transferring a pattern during an offset printing process. On the other hand, if the content of the high boiling point solvent exceeds 35% by weight, the off characteristics and directionality of the resultant pattern may become poor.
  • the component (c), the low boiling point solvent having a boiling point of 200 ° C or lower may be propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether propionate, ethylether propionate, propylene glycol monomethyl ether acetate, methylethyl ketone, ethyllactate or a miture thereof.
  • the low boiling point solvent is included in an amount of 5 to 35% by weight in the composition of the present invention. If the content of the low boiling point solvent is less than 5% by weight, the off characteristics and directionality of the resultant pattern may become poor. On the other hand, if the content of the low boiling point solvent exceeds 35 by weight, the flowability of the compositon becomes unsatisfactory for transferring a pattern during an offset printing process.
  • the combined amount of the high boiling point solvent and the low boiling point solvent is 40% by weight or less based on the total weight of the composition of the present invention. If the combined amount of the high boiling point solvent and the low boiling point solvent exceeds 40 by weight, the printing characteristics may become poor due to the low viscosity of the composition.
  • the high boiling point solvent and the low boiling point solvent may be blended appropriately so that the composition of the present invention has a viscosity ranging from 5,000 to 20,000 cP.
  • the component (d), the metal powder is not particularly limited and it may be a powder of a metal which can be used in the formation of an electrode for a display or a metal powder which can be used for blocking electromagnetic radiation.
  • the metal powder is a powder of silver, copper, nickel, ATO (antimony tin oxide), or an alloy thereof.
  • the metal powder is used in an amount of 50 to 85% by weight in the composition of the present invention. If the content of the metal powder is less than 50% by weight, it may be difficult to achieve desired electromagnetic radiation-shielding property. On the other hand, if the content of the metal powder exceeds 85% by weight, poor dispersion may occur due to the increased viscosity of the composition.
  • the composition of the present invention may further comprise an additive selected from a dispersant for dispersing the metal powder, a black pigment for adjusting the contrast ratio, a glass powder for increasing the adhesibility to the glass substrate upon sintering, etc.
  • the additive may be used in an amount of 0.01 to 10% by weight, more preferably 0.1 to 3% by weight, in the composition of the present invention.
  • the electromagnetic radiation-shielding layer formed of the composition according to the present invention has a low surface resistivity of about 0.2 to 1.2 ⁇ /D.
  • the optical filter according to the present invention may comprise functional layers commonly known in the art, i.e., an antireflection layer and a near-infrared ray (NIR)-blocking and selective light-absorbing layer.
  • the NIR-blocking and selective light-absorbing layer comprises a NIR- blocking material and a selective light-absorbing material.
  • the NIR-blocking material may be a mixture of a nickel complex-based compound and a diammonium-based compound, a pigment compound containing a copper or zinc ion, an organic pigment, or the like, and the selective light-absorbing material may be a metal complex derivative pigment having a metal element positioned in the center of an octaphenyltetraazaporphyrin or tetraazaporphyrin ring, a material selected from the group consisting of ammonia, water, and halogen being coordinated to the metal element.
  • the NIR-blocking and selective light-absorbing layer may be formed by mixing the above-described pigments for the NIR-blocking material and the selective light-absorbing material and a transparent plastic resin in a solvent to prepare a solution mixture and coating the solution mixture to a thickness of 1 to 20/"m on a transparent substrate.
  • the transparent plastic resin may be poly(methyl methacrylate)(PMMA), polyvinylalcohol (PVA), polycarbonate (PC), ethylenevinylacetate (EVA), poly(vinyl butyral)(PVB), polyethylene terephthalate (PET), or the like
  • the solvent may be toluene, xylene, acetone, methyl ethyl ketone (MEK), propylalcohol, isopropylalcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide (DMF), or the like.
  • a monolayered low refractive index film may be formed by subjecting a substrate film to a scratch resistance treatment and then hard coating with an acryl resin, or alternatively, it may be a layer obtained by alternately stacking a high refractive index transparent film and a low refractive index transparent film.
  • the antireflection layer may be formed by vacuum deposition or by wet coating (e.g., roll coating or die coating) using a solution containing the above materials.
  • the antireflection layer and the NIR-blocking and selective light- absorbing layer may be formed on different substrates, or alternatively, may be formed on the front and back surfaces of a substrate, respectively.
  • the NIR- blocking and selective light-absorbing layer may also be formed of a mixture obtained by mixing an adhesive with an NIR-blocking pigment and a selective light-absorbing pigment.
  • FIGS. 2 and 3 Preferable embodiments of the optical filter according to the present invention are illustrated in FIGS. 2 and 3. Referring to FIG.
  • an antireflection layer 200 for preventing the reflection of external light is disposed on an NIR-blocking and selective light-absorbing layer 240 via a transparent adhesive layer 220 to face the outside, an electromagnetic radiation-shielding layer 270 is directly formed on a glass substrate 260 by the above-described method, and the NIR-blocking and selective light-absorbing layer 240 is stacked at the front side of the glass substrate 260 opposite to the electromagnetic radiation-shielding layer 270 via a transparent adhesion layer 250 to obtain an optical filter for a display panel.
  • an antireflection layer 300 for preventing the reflection of external light is disposed to face the outside, an electromagnetic radiation-shielding layer 340 is directly formed on a glass substrate 330 by the above-described method, and an NIR-blocking and selective light-absorbing layer 360 is stacked at the rear side of the glass substrate 330 to face the electromagnetic radiation-shielding layer 340 via a transparent adhesion layer 350 to obtain an optical filter for a display panel.
  • an optical filter for a display panel may also be formed by directly forming an antireflection layer and an NIR-blocking and selective light- absorbing layer on the front and back surfaces of a substrate film, respectively.
  • an electromagnetic radiation-shielding layer and an antireflection layer may be disposed on a surface of a substrate film.
  • an adhesive may have a NIR-blocking function and a selective light-absorbing function.
  • the optical filter according to the present invention has a transmittance of 30 to 60% at a wavelength range of 380 to 780 nm.
  • the optical filter exhibits a very low haze value of 1 to 6% as measured in a state wherein no transparent sheet is adhered to each layer.
  • An optical filter manufactured as described above can be connected to a TV set by means of a fixing jig.
  • An optical filter for a display panel manufactured according to the method of the preset invention employs an electromagnetic radiation-shielding layer formed by directly applying a paste suitable for gravure offset printing to a glass substrate, unlike a conventional optical filter comprising an electromagnetic radiation-shielding mesh film formed by a conventional etching process. Therefore, the inventive method does not require the use of a polyester film and an adhesive layer, which markedly simplifies the filter structure and enhances the light transparency. Moreover, an optical filter according to the present invention can be applied to common household PDP TVs since it has low resistivity owing to its simple manufacture process, which also markedly reduces the manufacturing cost.
  • a paste composition was prepared as follows.
  • 15 parts by weight of an acrylate polymer resin having a weight average molecular weight was 25,000 which consisted of methacrylic acid (MA), benzyl methacrylate (BM), 2-hydroxyethyl (meth)acrylate (2-HEMA), and methyl (meth)acrylate (MMA) in a weight ratio of 30 : 20 : 10 : 40; 10 parts by weight of terpineol ( ⁇ -, ⁇ -, y - terpineol mixture) as a high boiling point solvent; 10 parts by weight of propylene glycol monomethyl ether propionate(PGMEP) as a low boiling point solvent; 63 parts by weight of silver powder as a metal powder; and 2 parts by weight of an amine group-containing organic dispersant, DS-IOl (San Nopco Korea, Ltd.) were mixed and stirred at room temperature, and milled in 3-roll mill to obtain a desired paste composition for printing.
  • MA methacrylic acid
  • BM benzy
  • the paste composition was gravure-offset printed on the surfaces of a glass substrate to form an electromagnetic radiation-shielding layer.
  • the paste composition prepared above was coated on a gravure plate and evenly spread to a given thickness using a blade, and then transferred to a blanket ("off process).
  • the pattern transferred to the blanket was subjected to a first curing process using a UV lamp, and the resulting pattern was transferred to a glass substrate ("set" process).
  • the pattern transferred to the glass substrate was subjected to a secondary curing process using a UV lamp and thermally treated to remove impurities, to obtain an electromagnetic radiation-shielding layer.
  • Electromagnetic radiation-shielding layers were formed by repeating Example 1 using the component listed in Table 1.
  • Example 3 The optical filter schematically illustrated in FIG. 2 was manufactured as follows.
  • a hard coating layer, a zirconium oxide-based film having a high refractive index, and a fluorosiloxane-based low refractive index film were sequentially stacked on a polyester film by a wet coating process to obtain an antireflection layer.
  • 300 g of poly(methyl methacrylate) was completely dissolved in 1,000 ml of methyl ethyl ketone (MEK), and 100 mg of octaphenyltetraazaporphyrin and 150 mg of IFG022 (Japan Chemical Co., Ltd.) were dissolved therein.
  • an acrylic transparent adhesive was continuously coated on the silicone release layer of a release film using a comma coating method, and subjected to thermal wind drying. Then, another release film was attached to the other surface of the adhesive layer to obtain a double-side releasably-treated transparent adhesive layer in the form of a roll.
  • the antireflection layer and the NIR-blocking and selective light-absorbing layer were attached to the glass substrate having thereon the electromagnetic radiation-shielding layer formed in Example 1 under a pressure of 3 kgf/m .
  • An optical filter for a display panel was manufactured by the procedure of Example 3 except that the electromagnetic radiation-shielding layer obtained in Example 2 was used. Comparative Example 3
  • An optical filter for a display panel was manufactured by the procedure of Example 3 except that the electromagnetic radiation-shielding layer obtained in Comparative Example 1 was used.
  • An optical filter for a display panel was manufactured by the procedure of Example 3 except that the electromagnetic radiation-shielding layer obtained in Comparative Example 2 was used.
  • An antireflection layer, an adhesive layer, and an NIR-blocking and selective light-absorbing layer were formed by the procedure of Example 3, except that a transparent adhesive was coated on an etching type mesh film
  • the electromagnetic radiation-shielding layer thus obtained was attached to a glass substrate under a pressure of 3kgf/m 2 and the release film was removed, to obtain an optical filter for a display panel illustrated in FIG. 1.
  • the optical filters manufactured in Examples 3 and 4 i.e., optical filters including electromagnetic radiation-shielding layers obtained by directly forming paste compositions according to the present invention on glass substrates using a gravure offset printing process, exhibited a haze value of about 3%, showing that the transparency of the optical filters manufactured in Examples 3 and 4 is better than that of the optical filters manufactured in Comparative Examples 3 to 5.
  • the optical filters manufactured in Examples 3 and 4 exhibited a uniform 15 ⁇ 20 ⁇ m linewidth.
  • the optical filters manufactured in Comparative Example 3 exhibited poor appearance, such as a wide pattern linewidth of 50 ⁇ m and poor pattern directionality.
  • the optical filter manufactured in Comparative Example 3 exhibited a wide mesh linewidth and poor pattern directionality having a markedly low transmittance of 36%, which is less than the filter transmittance of the inventive NIR-blocking and selective light-absorbing layer.
  • the optical filter manufactured in Example 4 exhibited a poor pattern, and, thus, it is difficult to estimate the surface resistivity and linewidth of the mesh pattern.
  • the electromagnetic radiation- shielding layers of the optical filters manufactured in Examples 3 and 4 exhibited a surface resistivity of 0.4 ⁇ 0.8 ⁇ /D, which is slightly higher than that (0.05 ⁇ /D) of the etched-mesh films used in conventional optical filters (Comparative Example 5).
  • an electromagnetic radiation-shielding layer formed as a multilayered sputtered- conducting film currently employed for household PDP TVs has a surface resistivity of 0.8 ⁇ 1.2 ⁇ /D
  • the optical filters manufactured in Examples 3 and 4 have a better electromagnetic radiation-shielding effect.

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  • Surface Treatment Of Optical Elements (AREA)

Abstract

An electromagnetic radiation-shielding layer included in an optical filter is formed by a printing process, thereby making it possible to manufacture an optical filter having good characteristics using a simple process.

Description

OPTICAL FILTER FOR DISPLAY PANELAND METHOD OFMANUFACTURING SAME
FIELD OF THE INVENTION
The present invention relates to an optical filter for a display panel and a method of manufacturing same. More particularly, the preset invention relates to an optical filter for a plasma display panel (PDP), wherein an electromagnetic radiation-shielding layer is directly formed on a glass substrate by a gravure offset method.
BACKGROUND OF THE INVENTION
Display panels are generally equipped with optical filters capable of, among others, blocking electromagnetic radiation and near-infrared rays (NIRs) which cause adverse effects on human health as well as malfunction of electronic equipment.
Currently available optical filters for plasma display panels (PDPs) for blocking harmful electromagnetic radiation can be generally classified into three types: i) a metal mesh film produced by attaching a copper film on a polyester (e.g., polyethylene terephthalate) substrate film and patterning the copper film by an etching process, ii) a fiber mesh film produced by processing a metal fiber or a metal-coated organic fiber on a substrate film and patterning the fiber, and iii) a multilayered conductive film produced by alternately stacking a metal (Ag) layer and a dielectric layer using a dry coating process such as sputtering.
However, such electromagnetic radiation-shielding filters are expensive to produce due to their complicated manufacturing processes and inefficient use of materials. Furthermore, when using a separate substrate film to manufacture a filter containing an electromagnetic radiation-shielding layer, an adhesive layer is needed to attach the electromagnetic radiation-shielding layer to the substrate film. In particular, the use of conventional mesh type electromagnetic radiation-shielding filters such as that shown in FIG. 1 makes it difficult to achieve vivid images due to high haziness. Thus, in order for the mesh type electromagnetic radiation-shielding layer to be used as an improved filter, it is necessary to form a transparent resin as adhesive layers separately to make the filter transparent to visible light.
Therefore, there has been an increasing need of developing a PDP filter that exhibits excellent electromagnetic radiation-shielding property and optical characteristics, which can be easily manufactured at a low cost.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved method of manufacturing an optical filter for a display panel.
In accordance with an aspect of the present invention, there is provided a method of manufacturing an optical filter for a display panel comprising a transparent glass substrate and an electromagnetic radiation-shielding layer, which comprises forming the electromagnetic radiation-shielding layer by printing on the glass substrate a composition comprising (a) 5 to 30% by weight of an acrylate polymer resin, (b) 5 to 35% by weight of a high boiling point solvent having a boiling point of 200 °C or higher, (c) 5 to 35% by weight of a low boiling point solvent having a boiling point of 200 °C or lower, and (d) 50 to 85% by weight of a metal powder. BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and features of the present invention will become apparent from the following description of the invention, when taken in conjunction with the accompanying drawings, which respectively show:
FIG. 1 is a sectional view illustrating the structure of a conventional optical filter;
FIG. 2 is a sectional view illustrating the structure of an optical filter according to an embodiment of the present invention; and FIG. 3 is a sectional view illustrating the structure of an optical filter according to another embodiment of the present invention.
<Brief description of the reference numerals in drawings>
100: antireflection layer 110: substrate film 120: adhesive layer 130: glass substrate
140: adhesive layer 150: substrate film
160: electromagnetic radiation-shielding layer
170: adhesive layer
180: near-infrared ray-blocking and selective light-absorbing layer 190: substrate film 200: antireflection layer
210: substrate film 220: adhesive layer
230: substrate film
240: near-infrared ray-blocking and selective light-absorbing layer
250: adhesive layer 260: glass substrate 270: electromagnetic radiation-shielding layer
300: antireflection layer 310: substrate film
320: adhesive layer 330: glass substrate
340: electromagnetic radiation-shielding layer 350: adhesive layer
360: near-infrared ray-blocking and selective light-absorbing layer
370: substrate film
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, an electromagnetic radiation- shielding layer is formed by forming a conductive mesh pattern directly on a glass substrate, e.g., using a gravure offset printing process. The electromagnetic radiation-shielding layer thus-formed has excellent mechanical characteristics (e.g., film adhesion property) and electrical conductivity.
The composition for forming the electromagnetic radiation-shielding layer according to the present invention comprises (a) 5 to 30% by weight of an acrylate polymer resin, (b) 5 to 35% by weight of a high boiling point solvent having a boiling point of 200 °C or higher, (c) 5 to 35% by weight of a low boiling point solvent having a boiling point of 200 "C or lower, and (d) 50 to 85% by weight of a metal powder.
The component (a), the acrylate polymer resin, may be selected from acrylate polymer resins commonly known in the art. Preferably, the acrylate polymer resin may be prepared by polymerizing an unsaturated carboxylic acid monomer, an aromatic monomer, and a monomer other than the unsaturated carboxylic acid monomer and the aromatic monomer.
The unsaturated carboxylic acid monomer is used to increase the elasticity of the acrylate polymer resin through enhanced hydrogen bonding. Specifically, the unsaturated carboxylic acid monomer may be acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl acetic acid, or an acid anhydride thereof. The unsaturated carboxylic acid monomer may be used in an amount of 20 to 50% by weight based on the total amount of monomers used in the preparation of the acrylate polymer resin. When the content of the unsaturated carboxylic acid monomer is within the above range, it is possible to obtain desired elasticity characteristics of the polymer resin and a desired degree of polymerization, and also to prevent gelation upon polymerization.
The aromatic monomer is an acrylic monomer which provides good adhesibility to a glass substrate to allow stable patterning, e.g., styrene, benzylmethacrylate, benzylacrylate, phenylacrylate, phenylmethacrylate, 2- nitrophenylacrylate, 4-nitrophenylacrylate, 2-nitrophenylmethacrylate, 4- nitrophenylmethacrylate, 4-chlorophenylacrylate, etc. The aromatic monomer may be used in an amount of 10 to 30% by weight, more preferably 15 to 20% by weight, based on the total amount of the monomers used in the preparation of the acrylate polymer resin. When the content of the aromatic monomer is within the above range, it is possible to satisfy all of the following requirements: good adhesion of a pattern to a substrate, good directionality of the pattern, stable patterning, and easy removal of organic materials upon sintering.
The monomer other than the unsaturated carboxylic acid monomer and the aromatic monomer (hereinafter, referred to simply as "the other monomer"), which is used in the preparation of the acrylate polymer resin, serves to adjust the glass transition temperature and polarity of the acrylate polymer resin. The other monomer may be an acrylic monomer such as 2-hydroxyethyl (meth)acrylate, 2-hydroxyoctyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, or n-butyl acrylate. The other monomer may be used in an amount of 20 to 60% by weight based on the total amount of the monomers used in the preparation of the acrylate polymer resin, which affect the glass transition temperature of the acrylate polymer resin, the heat resistance of the resultant pattern, and the intimate contact of the pattern with a substrate.
The acrylate polymer resin may be prepared by polymerizing the unsaturated carboxylic acid monomer, the aromatic monomer, and the other monomer in the presence of a solvent to prevent gelation of these monomers and to provide an appropriate evaporation rate during an offset printing process. The solvent may be propylene glycol monomethylether, dipropylene glycol monomethylether, propylene glycol monomethylether propionate, ethylether propionate, terpineol, propyleneglycol monomethylether acetate, dimethylaminoformaldehyde, methyl ethyl ketone, butylcarbitol, butylcarbitol acetate, γ -butyrolactone, ethyllactate, or a mixture thereof.
The acrylate polymer resin obtained by polymerizing the unsaturated carboxylic acid monomer, the aromatic monomer, and the other monomer in the presence of a solvent may have a weight average molecular weight of 10,000 to 100,000, more preferably 20,000 to 50,000. When the weight average molecular weight of the acrylate polymer resin is within the above range, the glass transition temperature of the acrylate polymer resin is lowered, and thus, the flowability of the acrylate polymer resin becomes satisfactory for transferring a pattern in a gravure groove to a blanket during an offset printing process, and the delivery of the composition into a gravure groove also becomes satisfactory owing to good elasticity characteristics of the acrylate polymer resin.
The acrylate polymer resin is used in an amount of 5 to 30% by weight in the composition according to the present invention. If the content of the acrylate polymer resin is less than 5% by weight, the offset printing process may not be efficiently performed due to the lowered elasticity of the composition. On the other hand, if the content of the acrylate polymer resin exceeds 30% by weight, the electric resistivity of the resultant pattern may increase.
The component (b), the high boiling point solvent having a boiling point of 200 °C or higher, may be γ -butyrolactone, butylcarbitol acetate, carbitol, methoxymethylether propionate, terpineol, or a mixture thereof. The high boiling point solvent is used in an amount of 5 to 35% by weight in the composition of the present invention. If the content of the high boiling point solvent is less than 5% by weight, the flowability of the composition becomes unsatisfactory for transferring a pattern during an offset printing process. On the other hand, if the content of the high boiling point solvent exceeds 35% by weight, the off characteristics and directionality of the resultant pattern may become poor.
The component (c), the low boiling point solvent having a boiling point of 200 °C or lower, may be propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether propionate, ethylether propionate, propylene glycol monomethyl ether acetate, methylethyl ketone, ethyllactate or a miture thereof.
The low boiling point solvent is included in an amount of 5 to 35% by weight in the composition of the present invention. If the content of the low boiling point solvent is less than 5% by weight, the off characteristics and directionality of the resultant pattern may become poor. On the other hand, if the content of the low boiling point solvent exceeds 35 by weight, the flowability of the compositon becomes unsatisfactory for transferring a pattern during an offset printing process. Preferably, the combined amount of the high boiling point solvent and the low boiling point solvent is 40% by weight or less based on the total weight of the composition of the present invention. If the combined amount of the high boiling point solvent and the low boiling point solvent exceeds 40 by weight, the printing characteristics may become poor due to the low viscosity of the composition.
Accordingly, the high boiling point solvent and the low boiling point solvent may be blended appropriately so that the composition of the present invention has a viscosity ranging from 5,000 to 20,000 cP. The component (d), the metal powder, is not particularly limited and it may be a powder of a metal which can be used in the formation of an electrode for a display or a metal powder which can be used for blocking electromagnetic radiation. Preferably, the metal powder is a powder of silver, copper, nickel, ATO (antimony tin oxide), or an alloy thereof.
The metal powder is used in an amount of 50 to 85% by weight in the composition of the present invention. If the content of the metal powder is less than 50% by weight, it may be difficult to achieve desired electromagnetic radiation-shielding property. On the other hand, if the content of the metal powder exceeds 85% by weight, poor dispersion may occur due to the increased viscosity of the composition.
If necessary, the composition of the present invention may further comprise an additive selected from a dispersant for dispersing the metal powder, a black pigment for adjusting the contrast ratio, a glass powder for increasing the adhesibility to the glass substrate upon sintering, etc. The additive may be used in an amount of 0.01 to 10% by weight, more preferably 0.1 to 3% by weight, in the composition of the present invention.
The electromagnetic radiation-shielding layer formed of the composition according to the present invention has a low surface resistivity of about 0.2 to 1.2 Ω/D.
In addition to the electromagnetic radiation-shielding layer, the optical filter according to the present invention may comprise functional layers commonly known in the art, i.e., an antireflection layer and a near-infrared ray (NIR)-blocking and selective light-absorbing layer. The NIR-blocking and selective light-absorbing layer comprises a NIR- blocking material and a selective light-absorbing material. The NIR-blocking material may be a mixture of a nickel complex-based compound and a diammonium-based compound, a pigment compound containing a copper or zinc ion, an organic pigment, or the like, and the selective light-absorbing material may be a metal complex derivative pigment having a metal element positioned in the center of an octaphenyltetraazaporphyrin or tetraazaporphyrin ring, a material selected from the group consisting of ammonia, water, and halogen being coordinated to the metal element. The NIR-blocking and selective light-absorbing layer may be formed by mixing the above-described pigments for the NIR-blocking material and the selective light-absorbing material and a transparent plastic resin in a solvent to prepare a solution mixture and coating the solution mixture to a thickness of 1 to 20/"m on a transparent substrate. Here, the transparent plastic resin may be poly(methyl methacrylate)(PMMA), polyvinylalcohol (PVA), polycarbonate (PC), ethylenevinylacetate (EVA), poly(vinyl butyral)(PVB), polyethylene terephthalate (PET), or the like, and the solvent may be toluene, xylene, acetone, methyl ethyl ketone (MEK), propylalcohol, isopropylalcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide (DMF), or the like.
For the antireflection layer, a monolayered low refractive index film may be formed by subjecting a substrate film to a scratch resistance treatment and then hard coating with an acryl resin, or alternatively, it may be a layer obtained by alternately stacking a high refractive index transparent film and a low refractive index transparent film. The antireflection layer may be formed by vacuum deposition or by wet coating (e.g., roll coating or die coating) using a solution containing the above materials.
The antireflection layer and the NIR-blocking and selective light- absorbing layer may be formed on different substrates, or alternatively, may be formed on the front and back surfaces of a substrate, respectively. The NIR- blocking and selective light-absorbing layer may also be formed of a mixture obtained by mixing an adhesive with an NIR-blocking pigment and a selective light-absorbing pigment. Preferable embodiments of the optical filter according to the present invention are illustrated in FIGS. 2 and 3. Referring to FIG. 2, an antireflection layer 200 for preventing the reflection of external light is disposed on an NIR-blocking and selective light-absorbing layer 240 via a transparent adhesive layer 220 to face the outside, an electromagnetic radiation-shielding layer 270 is directly formed on a glass substrate 260 by the above-described method, and the NIR-blocking and selective light-absorbing layer 240 is stacked at the front side of the glass substrate 260 opposite to the electromagnetic radiation-shielding layer 270 via a transparent adhesion layer 250 to obtain an optical filter for a display panel. Referring to FIG. 3, an antireflection layer 300 for preventing the reflection of external light is disposed to face the outside, an electromagnetic radiation-shielding layer 340 is directly formed on a glass substrate 330 by the above-described method, and an NIR-blocking and selective light-absorbing layer 360 is stacked at the rear side of the glass substrate 330 to face the electromagnetic radiation-shielding layer 340 via a transparent adhesion layer 350 to obtain an optical filter for a display panel. Although not shown, an optical filter for a display panel may also be formed by directly forming an antireflection layer and an NIR-blocking and selective light- absorbing layer on the front and back surfaces of a substrate film, respectively. In some cases, an electromagnetic radiation-shielding layer and an antireflection layer may be disposed on a surface of a substrate film. In addition, an adhesive may have a NIR-blocking function and a selective light-absorbing function.
The optical filter according to the present invention has a transmittance of 30 to 60% at a wavelength range of 380 to 780 nm. The optical filter exhibits a very low haze value of 1 to 6% as measured in a state wherein no transparent sheet is adhered to each layer.
An optical filter manufactured as described above can be connected to a TV set by means of a fixing jig.
An optical filter for a display panel manufactured according to the method of the preset invention employs an electromagnetic radiation-shielding layer formed by directly applying a paste suitable for gravure offset printing to a glass substrate, unlike a conventional optical filter comprising an electromagnetic radiation-shielding mesh film formed by a conventional etching process. Therefore, the inventive method does not require the use of a polyester film and an adhesive layer, which markedly simplifies the filter structure and enhances the light transparency. Moreover, an optical filter according to the present invention can be applied to common household PDP TVs since it has low resistivity owing to its simple manufacture process, which also markedly reduces the manufacturing cost.
Hereinafter, the present invention will be described more specifically by Examples. However, the following Examples are provided only for illustrations and thus the present invention is not limited to or by them.
Example 1
A paste composition was prepared as follows.
15 parts by weight of an acrylate polymer resin having a weight average molecular weight was 25,000 which consisted of methacrylic acid (MA), benzyl methacrylate (BM), 2-hydroxyethyl (meth)acrylate (2-HEMA), and methyl (meth)acrylate (MMA) in a weight ratio of 30 : 20 : 10 : 40; 10 parts by weight of terpineol ( α -, β -, y - terpineol mixture) as a high boiling point solvent; 10 parts by weight of propylene glycol monomethyl ether propionate(PGMEP) as a low boiling point solvent; 63 parts by weight of silver powder as a metal powder; and 2 parts by weight of an amine group-containing organic dispersant, DS-IOl (San Nopco Korea, Ltd.) were mixed and stirred at room temperature, and milled in 3-roll mill to obtain a desired paste composition for printing.
The paste composition was gravure-offset printed on the surfaces of a glass substrate to form an electromagnetic radiation-shielding layer. Specifically, the paste composition prepared above was coated on a gravure plate and evenly spread to a given thickness using a blade, and then transferred to a blanket ("off process). Then, the pattern transferred to the blanket was subjected to a first curing process using a UV lamp, and the resulting pattern was transferred to a glass substrate ("set" process). The pattern transferred to the glass substrate was subjected to a secondary curing process using a UV lamp and thermally treated to remove impurities, to obtain an electromagnetic radiation-shielding layer.
Example 2 and Comparative Examples 1 and 2
Electromagnetic radiation-shielding layers were formed by repeating Example 1 using the component listed in Table 1.
Table 1
Figure imgf000013_0001
Example 3 The optical filter schematically illustrated in FIG. 2 was manufactured as follows.
First, a hard coating layer, a zirconium oxide-based film having a high refractive index, and a fluorosiloxane-based low refractive index film were sequentially stacked on a polyester film by a wet coating process to obtain an antireflection layer. On the other hand, 300 g of poly(methyl methacrylate) was completely dissolved in 1,000 ml of methyl ethyl ketone (MEK), and 100 mg of octaphenyltetraazaporphyrin and 150 mg of IFG022 (Japan Chemical Co., Ltd.) were dissolved therein. Then, a solution of 120 mg of acridine orange (Aldrich Chemical Co., Ltd.) in 50 ml of isopropylalcohol was gradually added thereto, and the resultant solution was coated on a biaxially elongated film by a wet coating process, to obtain an NIR-blocking and selective light-absorbing layer (dry thickness: about 5 /^).
Next, an acrylic transparent adhesive was continuously coated on the silicone release layer of a release film using a comma coating method, and subjected to thermal wind drying. Then, another release film was attached to the other surface of the adhesive layer to obtain a double-side releasably-treated transparent adhesive layer in the form of a roll.
While the release film of the transparent adhesive layer was delaminated, the antireflection layer and the NIR-blocking and selective light-absorbing layer were attached to the glass substrate having thereon the electromagnetic radiation-shielding layer formed in Example 1 under a pressure of 3 kgf/m .
Example 4
An optical filter for a display panel was manufactured by the procedure of Example 3 except that the electromagnetic radiation-shielding layer obtained in Example 2 was used. Comparative Example 3
An optical filter for a display panel was manufactured by the procedure of Example 3 except that the electromagnetic radiation-shielding layer obtained in Comparative Example 1 was used.
Comparative Example 4
An optical filter for a display panel was manufactured by the procedure of Example 3 except that the electromagnetic radiation-shielding layer obtained in Comparative Example 2 was used.
Comparative Example 5
An antireflection layer, an adhesive layer, and an NIR-blocking and selective light-absorbing layer were formed by the procedure of Example 3, except that a transparent adhesive was coated on an etching type mesh film
(Nippon Filcon Co., Ltd.) having a linewidth of 10 βn, a line pitch of 300μm, and an aperture ratio of about 93%, which was then dried, and a release film was laminated on the surface of the adhesive layer, to obtain an electromagnetic radiation-shielding layer.
The electromagnetic radiation-shielding layer thus obtained was attached to a glass substrate under a pressure of 3kgf/m2 and the release film was removed, to obtain an optical filter for a display panel illustrated in FIG. 1.
Evaluation of characteristics For the optical filters manufactured in Examples 3 and 4 and Comparative Examples 3 and 5, surface resistivities were measured using a 4 point probe consisting of four probes positioned at a same interval, according to ASTM D257 standard, and the transmittance and haze values were measured using a spectrometer (model: NDH, Nippon Denshoku Kogyo K.K.). In addition, the minimum linewidth of the mesh patterns of the electromagnetic radiation-shielding layers was measured using an optical microscope. The shapes of the mesh patterns were also observed using the same optical microscope. The results are summarized in Table 2.
Table 2
Figure imgf000016_0001
As shown in Table 1, the optical filters manufactured in Examples 3 and 4, i.e., optical filters including electromagnetic radiation-shielding layers obtained by directly forming paste compositions according to the present invention on glass substrates using a gravure offset printing process, exhibited a haze value of about 3%, showing that the transparency of the optical filters manufactured in Examples 3 and 4 is better than that of the optical filters manufactured in Comparative Examples 3 to 5.
With respect to the shapes of the mesh patterns, the optical filters manufactured in Examples 3 and 4 exhibited a uniform 15~20μm linewidth. On the other hand, the optical filters manufactured in Comparative Example 3 exhibited poor appearance, such as a wide pattern linewidth of 50^m and poor pattern directionality. With respect to the light transmittance, the optical filter manufactured in Comparative Example 3 exhibited a wide mesh linewidth and poor pattern directionality having a markedly low transmittance of 36%, which is less than the filter transmittance of the inventive NIR-blocking and selective light-absorbing layer.
The optical filter manufactured in Example 4 exhibited a poor pattern, and, thus, it is difficult to estimate the surface resistivity and linewidth of the mesh pattern.
The optical filter manufactured in Comparative Examples 5, including etched-mesh films commonly employed in the art, exhibited a markedly high haze value due to the presence of the mesh film.
With respect to surface resistivity generally used as a barometer of an electromagnetic radiation-shielding effect, the electromagnetic radiation- shielding layers of the optical filters manufactured in Examples 3 and 4 exhibited a surface resistivity of 0.4~0.8 Ω/D, which is slightly higher than that (0.05 Ω/D) of the etched-mesh films used in conventional optical filters (Comparative Example 5). However, considering the fact that an electromagnetic radiation-shielding layer formed as a multilayered sputtered- conducting film currently employed for household PDP TVs has a surface resistivity of 0.8~1.2 Ω/D, it can be seen that the optical filters manufactured in Examples 3 and 4 have a better electromagnetic radiation-shielding effect.
While the invention has been described with respect to the above specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art which also fall within the scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS
1. A method of manufacturing an optical filter for a display panel comprising a transparent glass substrate and an electromagnetic radiation-shielding layer, which comprises forming the electromagnetic radiation-shielding layer by directly printing on the glass substrate a composition comprising (a) 5 to 30% by weight of an acrylate polymer resin, (b) 5 to 35% by weight of a high boiling point solvent having a boiling point of 200 °C or higher, (c) 5 to 35% by weight of a low boiling point solvent having a boiling point of 200 "C or lower, and (d) 50 to 85% by weight of a metal powder, based on the total weight of the composition.
2. The method of claim 1, wherein the optical filter further comprises at least one selected from the group consisting of an antireflection layer and a near- infrared ray-blocking and selective light-absorbing layer.
3. The method of claim 1, wherein the surface resistivity of the electromagnetic radiation-shielding layer is 0.2 to 1.2 Ω/α.
4. The method of claim I5 wherein the composition is printed by a gravure offset printing method.
5. The method of claim 2, wherein the haze value of the optical filter is 1 to 6% as measured in a state wherein no transparent sheet is adhered to each of the electromagnetic radiation-shielding layer, the antireflection layer, and the near- infrared ray-blocking and selective light-absorbing layer.
6. The method of claim 1, wherein the acrylate polymer resin of the component (a) is prepared by polymerizing i) 20 to 50% by weight of an unsaturated carboxylic acid monomer, ii) 10 to 30% by weight of an aromatic monomer, and iii) 20 to 60% by weight of at least one monomer selected from the group consisting of 2-hydroxyethyl(meth)acrylate, 2-hydroxyoctyl(meth)acrylate, methyl(meth)acrylate, ethyl(meth)acrylate, and n-butylacrylate, in the presence of a solvent, the % by weight being based on the total weight of the polymer.
7. The method of claim 6, wherein the unsaturated carboxylic acid monomer is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl acetic acid, acid anhydrides thereof, and a mixture thereof.
8. The method of claim 6, wherein the aromatic monomer is selected from the group consisting of styrene, benzylmethacrylate, benzylacrylate, phenylacrylate, phenylmethacrylate, 2-nitrophenylacrylate, 4-nitrophenylacrylate, 2- nitrophenylmethacrylate, 4-nitrophenylmethacrylate, 2-nitrobenzylmethacrylate, 4-nitrobenzylmethacrylate, 2-chlorophenylmethacrylate, 4-chlorophenylacrylate, 2-chlorophenylmethacrylate, 4-chlorophenylmethacrylate, and a mixture thereof.
9. The method of claim 1, wherein the acrylate polymer resin component (a) has a weight average molecular weight of 10,000 to 100,000.
10. The method of claim 1, wherein the high boiling point solvent (b) is 7 - butyrolactone, butylcarbitol acetate, carbitol, methoxymethylether propionate, terpineol, or a mixture thereof.
11. The method of claim 1, wherein the low boiling point solvent (b) is propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether propionate, ethylether propionate, propylene glycol monomethyl ether acetate, methylethyl ketone, ethyllactate, or a miture thereof.
12. The method of claim 1, wherein the combined amount of the high boiling point solvent and the low boiling point solvent is 40% by weight or less based on the total weight of the composition.
13. The method of claim 1, wherein the composition has a viscosity ranging from 5,000 to 20,00O cP.
14. The method of claim 2, wherein the antireflection layer is formed at the outermost layer.
15. The method of claim 2, wherein the near-infrared ray-blocking and selective light-absorbing layer and the antireflection layer are respectively formed on either side of the transparent glass substrate.
16. The method of claim 2, wherein the near-infrared ray-blocking and selective light-absorbing layer is formed of a mixture of a near-infrared ray-blocking pigment and a selective light-absorbing pigment with an adhesive.
17. An optical filter for a display panel, manufactured by any one of the methods of claims 1 through 16.
18. The optical filter of claim 17, having a transmittance of 30 to 60% at a wavelength range from 380 to 780 nm.
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