JP2006028437A - Method for joining functional film, optical filter and plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for joining each of functional films such as an electromagnetic wave-cutting film, a near infrared light-cutting film, an outside light reflection-preventing film, a contamination-preventing layer, a hard coat layer, a color-correcting functional film, etc., on the surface of the transparent substrate of an optical filter arranged at the front surface of a plasma display panel (PDP) or by placing a space at its front surface, capable of improving the yield of good products without having a defect on visibility by inhibiting the involvement of bubbles on the joined boundary, and the optical filter and PDP produced by the same method. <P>SOLUTION: This method for joining the functional film is provided by forming an adhesive layer consisting mainly of a thermoplastic elastomer and plasticizer on the joining surface of the functional film in advance, and overlapping and joining the adhesive layer surface with the transparent substrate surface for the optical filter, the front surface of the PDP, or the surface of the other functional film already joined on the substrate surface or the front surface of the PDP. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for manufacturing a plasma display panel (hereinafter referred to as PDP), and more particularly, to a method for bonding a functional film in an optical filter used by placing a front surface of a PDP or a space in front of the PDP. The optical filter and the PDP manufactured by

2. Description of the Related Art In recent years, PDPs that are light-emitting and flat display panels have attracted attention because they can easily increase the size of a display screen of a television or the like and have excellent screen brightness. This PDP main body part is filled with a small amount of inert gas such as neon or xenon in a thin vacuum vessel surrounded by two glass plates, and the energy of ultraviolet rays generated by plasma discharge in the container. It is an image display device using light emitted from an excited phosphor. When displaying an image, electromagnetic waves are by-produced and electromagnetic waves leaking from the front, which is the display surface, damage to the health of viewers, etc., and malfunction of devices, especially malfunction of various home appliances with remote control devices due to leaking near infrared rays, etc. Is a problem. In addition, when the viewer looks at the display screen, external light is reflected on the surface of the display surface, and there is a problem that it is difficult for the viewer to see the screen. Furthermore, since the glass surface which comprises PDP is exposed, when it breaks by some impact, a glass piece may fly.

In order to avoid the above-mentioned problems, a functional film having various functions such as electromagnetic wave shielding, infrared cut, anti-reflection of external light, anti-glare and the like is usually used for PDPs of PDP display devices currently on the market. As an optical filter configured to be bonded to one or both surfaces of a transparent substrate such as a glass plate or an acrylic plate, it is arranged with a space in front of the PDP. Such a functional film is usually one in which each functional layer selected as desired is formed on one or more layers on the surface of a plastic film or the like.

As a method for joining the above functional films constituting the optical filter, for example, a transparent resin plate for an optical filter and a light control coat layer or a hard coat layer for preventing external light reflection and anti-glare on the surface of a polycarbonate film or the like Each functional film provided with a surface coat layer such as heat-pressed with an adhesive that is a thermosetting resin such as urethane resin, acrylic resin, epoxy resin or hot melt resin such as olefin resin Acrylic pressure-sensitive adhesive between the optical system film constituting the outermost layer and other members adjacent to the optical system film in the method of manufacturing by bonding and integrating (Patent Document 1) Pressure-sensitive adhesive layers such as polyester-based adhesives, silicone-based adhesives, rubber-based adhesives, and EVA (ethylene-vinyl acetate copolymer) And a heat-adhesive film body) system such as by sequentially interposed method of thermocompression bonding (Patent Document 2) are known.
JP 2000-28813 A JP 2002-123182 A

Since the optical filter is installed between the PDP surface and the image viewer, the optical uniformity is strictly evaluated over the entire surface, such as transparency. However, for example, when a transparent substrate and a film layer having various functions are joined, bubbles are easily caught between the layers, and when they are joined by the above method, the entrained bubbles cannot be removed. And as there are more functions given to the optical filter as described above, the number of bonding steps increases and the opportunity for entraining bubbles increases. Since these bubbles are present in the transparent flat plate, they are very easy to see. As a result, the optical filter containing these bubbles becomes defective or downgraded, and the productivity and yield rate of non-defective products are greatly reduced. As a result, the cost of non-defective products increases. Such a phenomenon applies not only in the case of the optical filter described above but also in the case where each of the functional films is directly attached to the front surface of the PDP. In this case, if a defective product occurs, the expensive PDP main body becomes a defective product and the loss becomes larger. Even if the adhesive surface is carefully peeled off and rejoined, a great deal of labor is required, resulting in a total cost increase.

The object of the present invention is, as described above, to the surface of a transparent substrate for an optical filter used with a space interposed in front of the PDP, to the front surface of the PDP, or already to the surface of the substrate or the panel. In the bonding method of each functional film, such as electromagnetic wave cut, near infrared ray cut, external light reflection prevention, antifouling layer, hard coat layer, color correction function film, etc. It is an object of the present invention to provide a functional film joining method capable of suppressing the entrainment of the film and improving the yield of non-defective products with no defect in transparency.

  As a result of diligent studies to solve the above problems, the present invention has succeeded in finding a pressure-sensitive adhesive composition having excellent self-adhesiveness and reworkability at the time of joining work and having high adhesive strength after heat treatment. The invention has been reached. That is, the first gist of the present invention is that a pressure-sensitive adhesive layer mainly composed of a thermoplastic elastomer and a plasticizer is previously formed on the bonding surface of the functional film, and the surface of the pressure-sensitive adhesive layer is used as a transparent substrate for an optical filter. The present invention resides in a method for bonding a functional film, characterized in that it is bonded to the surface, to the front surface of the PDP, or to the surface of another functional film already bonded to the substrate surface or the front surface of the panel.

And the second gist of the present invention is an optical filter in which one or two or more functional films are joined and laminated on one side or both sides of the surface of the transparent substrate, and are arranged with a space interposed in front of the plasma display panel. 6. A bonding interface between the functional film and the transparent substrate surface and / or between the functional film and another functional film surface already laminated is described in any one of claims 1 to 5. The optical filter is characterized by being bonded by the bonding method of

The third aspect of the present invention is a PDP in which one or more functional films are bonded and laminated on the front surface of the PDP, and between the functional film and the front surface of the PDP, and / or the functional film. The PDP is characterized in that the bonding interface between the film and the surface of another functional film already laminated is bonded by the bonding method according to any one of claims 1 to 5.

The optical filter and the PDP manufactured by the bonding method of the present invention have a transparent substrate or a front surface of the PDP and various functional films bonded together through an adhesive layer mainly composed of a thermoplastic elastomer and a plasticizer. The self-adhesiveness and reworkability of the pressure-sensitive adhesive are excellent, the bubble entrainment at the bonding interface is suppressed, and the yield of non-defective products having no defect in the transparency after bonding can be improved. In addition, said self-adhesion means the characteristic that the adhesive film which joined this adhesive layer substantially shows adhesiveness with respect to a to-be-adhered surface by the pressure by self-weight.

The functional film joining method of the present invention and the optical filter and PDP produced by the joining method will be described below. The functional film of the present invention has a pressure-sensitive adhesive layer formed on the bonding surface thereof, the surface of the optical filter transparent substrate, or the front surface of the PDP, or another functional film surface already bonded to the substrate surface or the front surface of the panel. To be joined.

The transparent substrate is used for structurally supporting the functional film having various performances described above, and the substrate is not particularly limited and is composed of a known material. Although a thing can be used, the plate-shaped object which consists of synthetic resins, such as an acrylic resin, a polycarbonate resin, a polystyrene resin, a methyl methacrylate-styrene copolymer resin, and a glass plate are mentioned, for example. Of these, acrylic resin plates and tempered glass plates are preferred from the viewpoints of transparency, moldability, and strength. The thickness of these transparent substrates is not particularly limited, but is usually 1 to 10 mm.

Each of the above functional films is usually formed by forming a layer (functional layer) exhibiting the respective functions on the surface of the transparent base film. The base film is not particularly limited, but for example, a film having good transparency and excellent toughness is preferable. For example, a polyester film, a triacetyl cellulose film, a diacetyl cellulose film, an acetate butyrate film, a poly Examples include ether sulfone film, polyacrylic resin film, polyurethane resin film, polycarbonate film, polysulfone film, polyether film, trimethylpentene film, polyether ketone film, and (meth) acrylonitrile film. An axially stretched polyester film is practically selected from the viewpoints of transparency, durability, and versatility.

  Examples of the functional layer include, but are not limited to, an electromagnetic wave shielding layer, a near infrared shielding layer, an external light antireflection layer, an antiglare layer, an antifouling layer, a hard coat layer, and a color correction functional film. However, in addition to the functions of these layers, if a layer having another function is useful, a layer having these functions can be included.

  The electromagnetic wave shielding layer is a layer for shielding the electromagnetic wave generated inside the PDP from the image display surface, and the material constituting the functional layer is a material having both conductivity and transparency. Basically, publicly known ones can be used. Specifically, for example, one or more transparent conductive films made of metal and / or metal oxides, and conductive fibers are meshed. And conductive resin layers in which conductive fine particles such as metal fine particles and / or metal oxide fine particles are dispersed, and such layers are vacuum-deposited or sputtered on the surface of the transparent base film. Or a conductive fiber mesh can be bonded together or coated in a mesh shape.

Examples of the metal having transparent conductivity include gold, silver, platinum, palladium, copper, titanium, chromium, molybdenum, nickel, and zirconium. Among them, silver is particularly preferable because a conductive layer having excellent conductivity can be obtained, and at the same time, a near infrared wavelength region is reflected and a near infrared shielding function is provided. When this metal layer is provided as a conductive layer, it is preferably a multilayer film with a dielectric layer in order to prevent reflection of near infrared rays in the metal layer. Examples of such a dielectric layer include layers made of various metal oxides, metal nitrides, metal sulfides, and the like. Examples of the metal oxide having transparent conductivity include silicon oxide, titanium oxide, tantalum oxide, tin oxide, indium oxide, zirconium oxide, zinc oxide, and a composite oxide of indium oxide and tin oxide. Of these metals and metal oxides, one of them may be used alone, or two or more of them may be used in combination.

  The conductive fiber mesh is preferably composed of a metallized fiber fabric that is lightweight and has excellent durability and flexibility. The manufacturing method of the metallized fiber fabric itself is not important, and any metallized fiber fabric obtained by any manufacturing method can be used, but among these metallized fiber fabrics, for example, a synthetic fiber such as polyester can be used. After a surface resin treatment on a woven fabric, etc., the surface is nickel, copper, or a conductive cloth in which a conductive metal such as nickel is electroplated by 15 to 30% by mass, or a synthetic fiber mesh surface such as polyester. A conductive mesh obtained by electroless plating of a conductive metal such as silver or nickel and further blackening is excellent in durability and flexibility and is suitable as a conductive member. The fiber diameter of the conductive mesh is usually 10 to 60 μm, and the mesh size is preferably in the range of 40 to 200 mesh. The mesh size is a size defined by a Tyler standard sieve.

In addition, as the conductive metal network, a method of printing a lattice pattern on the surface of a transparent substrate using a conductive ink or the like, or a metal thin film such as copper, silver, or aluminum is provided on the surface of the transparent substrate. After that, it is possible to exemplify those in which a lattice pattern is formed by means such as etching, but also punching a metal foil of a predetermined thickness obtained by plastic processing such as rolling of a metal such as copper, silver, and aluminum A material in which a large number of holes are provided by a lattice pattern and the like can be exemplified as the conductive metal network. The lattice pattern preferably has a line width of 5 to 50 μm, a thickness of 1 to 100 μm, and a line portion pitch of 150 to 800 μm in view of electromagnetic shielding performance and transparency.

The near-infrared shielding layer is a layer for shielding near-infrared rays generated inside the PDP from leaking from the image display surface. As a material constituting such a functional film, a property of reflecting near-infrared rays or A material having a property of absorbing near infrared rays is used. Specifically, a known material can be used. For example, a near infrared reflecting material such as silver or a near infrared absorbing dye or a metal oxide can be used. A matrix thin film layer containing a near-infrared absorbing material formed on the surface of a transparent base film by a method such as vapor deposition, and the transparency of the matrix by a method of kneading the above-mentioned near-infrared absorbing dye or metal oxide. A film dispersed in a resin, or the above-mentioned near-infrared absorbing dye or metal oxide is mixed in a matrix resin solution dissolved in a solvent, and uniformly dispersed to obtain a transparent base. The film can be coated on a film by a casting method, and then the solvent is removed to form a near-infrared absorbing resin layer. In any case, the film is transparent to visible light and has a near-infrared shielding function. The film is not particularly limited as long as it has a film.

Examples of the near infrared absorbing dyes include phthalocyanine dyes, naphthalocyanine dyes, imonium compounds, diimonium dyes, aminium dyes, cyanine dyes, merocyanine dyes, (thio) pyrylium dyes, naphtholactam dyes, pentacene dyes, anthraquinones System dyes, oxyindolizine dyes, quinoid dyes, indoaniline dyes, nickel thio complex dyes, thiourea compounds, bisthiourea compounds, and the like. Examples of the metal oxide include tin-doped indium oxide (ITO) and antimony-doped tin oxide (ATO).

As the matrix layer containing the above dye, thermoplastic resins such as acrylic resins, polyester resins, styrene resins, thermosetting resins such as epoxy resins and polyurethane resins; multifunctional crosslinkable monomers such as epoxy acrylates and urethane acrylates , Oligomers; thin films having a matrix component of a silane compound such as tetraalkylsilane or a cured product of a curable compound such as a hydrolyzate thereof. These are preferably formed by applying a coating material containing the matrix component on a transparent substrate by a wet coating method such as a spin coating method, a die coating method, or a dipping method.

The total light transmittance in the visible light region of the optical filter using the near-infrared shielding layer obtained by the above means is 45% or more, preferably 60% or more, and the light transmission with a wavelength of 800 to 1100 nm. The rate is preferably 30% or less. By setting to such a range, it is possible to reliably prevent malfunction of the remote control device while ensuring sufficient transparency as an optical filter. The visible light region means a wavelength range of 450 to 650 nm. In the present invention, the near-infrared absorbing compound can be contained in the pressure-sensitive adhesive layer.

Next, the external light antireflection layer is generally formed by alternately laminating a low refractive index layer and a high refractive index, and the low refractive index layer and the high refractive index layer are sequentially laminated as viewed from the viewer side. Configured. The high refractive index layer contains fine particles of a high refractive index material such as indium oxide, titanium oxide, zirconium oxide, bismuth oxide, tin oxide, zinc oxide, antimony oxide, tantalum oxide, cerium oxide, and magnesium oxide in a curable resin. It can be formed and contained. On the other hand, the low refractive index layer is a layer having a lower refractive index than the above high refractive index layer. For example, the low refractive index layer does not contain the above fine particles in the curable resin or has a low refractive index such as magnesium fluoride, silicon oxide, or silica. It can be formed by containing fine particles of a refractive index substance. The size of the fine particles is usually 0.1 μm or less, preferably 0.05 μm or less, as the primary particle size. If the primary particle size is too large, the transparency of the layer may be reduced and the brightness of the panel may be impaired. Moreover, the content rate of said microparticles | fine-particles is 10-70 mass parts normally, Preferably it is 40-70 mass parts. Moreover, it is preferable that the thickness of each said layer is normally about 0.01-0.5 micrometer.

The antiglare layer is not particularly limited, and a known layer can be used. For example, a layer in which fine irregularities are formed by dispersing fine particles in a polymer film is bonded. Means are mentioned. As the fine particles for forming the irregularities, fine particles of inorganic compounds are preferably used. For example, inorganic oxides such as silicon dioxide, aluminum oxide, magnesium oxide, tin oxide, silicon monoxide, zirconium oxide, and titanium oxide are suitable. is there. Among these, silica fine particles whose main component is silicon dioxide are particularly suitable from the viewpoint of obtaining an inexpensive one having a small particle size distribution. Examples of such commercially available silica fine particles include Cyloid 72 (manufactured by Fuji Devison Chemical), Cyroid 244 (manufactured by Fuji Devison Chemical), Mizukasil P527 (manufactured by Mizusawa Chemical), Aerosil TT600 (manufactured by Degussa), and the like. Can be mentioned. Moreover, you may use the aggregate of colloidal silica as a silica particle. Examples of commercially available colloidal silica include Ludox AM (manufactured by DuPont), Xesol A200 (manufactured by Bayer AG), Snowtex-C (manufactured by Nissan Chemical Industries), and the like. The fine particles generally have a particle size of 0.002 to 20 μm. The blending amount of the fine particles is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the polymerizable compound to be added. As such a polymer film, a resin obtained by curing a polyfunctional acrylic monomer, or a silicone-based crosslinkable resin, a melamine-based crosslinkable resin, an epoxy-based crosslinkable resin, or the like is cured by heat or ultraviolet rays. Resins and the like can be mentioned as suitable ones, but are not particularly limited thereto. A film provided with an external light reflection preventing function is called AR (Anti).
A film provided with a reflection (reflective) film or an antiglare function may be referred to as an AG (anti glare) film.

The antifouling layer can be obtained by applying a water repellent and oil repellent coating on the surface. Examples of such water- and oil-repellent coating agents include fluorine-based coating agents such as siloxane-based and fluorinated alkylsilyl compounds. Examples of the fluorinated alkylsilyl compound include KP-801M (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.).

The hard coat layer can be formed on the surface by curing polyfunctional acrylates such as polyester acrylates such as DPHA, TMPTA, and PETA, urethane acrylates, and epoxy acrylates by heat curing or ionizing radiation. In addition, this surface hardening process can be replaced with this when there is a hardening effect by the polymer film used for the antiglare layer.

Further, the color correction function film is not particularly limited, and a known film can be used. For example, a dye having a desired hue is dispersed in a transparent base film such as a polyester film or a polycarbonate film. A method in which a pigment is previously dispersed in a polymer such as polyethylene terephthalate (PET), and a method of coating or joining the surface of a base film such as a polyester film or a polycarbonate film, or a dye or pigment for color correction in an adhesive layer. The method of adding etc. is mentioned. In the present invention, it is easy to add a color correcting dye or pigment such as the above-mentioned pigment to the pressure-sensitive adhesive to be used.

As each of the above functional films, different functional layers are formed on both sides of one base film, and another functional layer is further formed on the surface of one functional layer formed on the surface of one base film. Things can also be adopted. Thereby, it is possible to manufacture an optical filter having a plurality of desired functions by bonding with a small number of adhesive layers. For example, the above-mentioned external light antireflection layer and antiglare layer are usually placed in the outermost layer of the optical filter, but the surface thereof can be further subjected to antifouling treatment and surface hardening treatment.

  The adhesive used to bond the functional film obtained as described above to a transparent substrate, the surface of another functional film that has already been bonded, or the front surface of the PDP is mainly composed of a thermoplastic elastomer and a plasticizer. Use what

The thermoplastic elastomer having the above properties is not particularly limited, and examples thereof include those composed of a block segment composed of a block of a styrene monomer and a block of a rubber monomer. The rubber monomer is a polymerizable monomer that forms a rubber-like substance, and examples of the polymer constituting the block segment made of such a rubber monomer include isoprene polymer, polypropylene polymer, polyethylene / propylene copolymer, butylene polymer, Examples include butadiene polymers, chloroprene polymers, and isobutyl / isoprene copolymers. Therefore, the thermoplastic elastomer used in the present invention includes an elastomer containing each of the above block segments or a combination thereof and a block of styrene, and specific examples thereof include polystyrene-polyisoprene-polystyrene (SIS), Polystyrene-polybutylene-polystyrene (SBS), polystyrene-poly (ethylene / butylene) block-polystyrene (SEBS), polystyrene-poly (ethylene / propylene) block-polystyrene (SEPS), polystyrene-polyisoprene (SI), polystyrene-polybutylene (SB), polystyrene-poly (ethylene / propylene) block (SEP), and the like.

The degree of polymerization of the elastomer can be appropriately selected according to the type of plasticizer to be added, the amount added, and the properties expected as an adhesive. For example, in the case of SEBS, the mass average molecular weight is usually 15,000 to Those having 500,000 are preferably used, and those having 100,000 to 500,000 are more preferably used.

  The plasticizer is appropriately selected from components that can be added to the elastomer and impart self-adhesion depending on the type of thermoplastic elastomer component to be used. When it has a phase and a rubber phase, a high molecular weight compound having a high affinity for the rubber phase and a low affinity for the polystyrene phase is preferred. Preferred examples of the plasticizer include naphthenic oil and / or paraffin oil. In addition, said self-adhesion means the characteristic which the adhesive film which formed this adhesive layer substantially shows adhesiveness with respect to a to-be-adhered surface by the pressure by self-weight.

  As said naphthenic oil, that whose flash point is 100-300 degreeC is preferable, and the thing of 150-280 degreeC is more preferable. The pour point is preferably -30 to -5 ° C, more preferably -25 to -10 ° C. Moreover, that whose specific gravity is 0.83-0.87 is preferable, and what is 0.837-0.868 is more preferable. Furthermore, the thing whose carbon number is 3-8 is preferable, and the thing of 5-6 is more preferable.

  On the other hand, the above paraffin oil preferably has a flash point of 100 to 300 ° C, more preferably 150 to 280 ° C. The pour point is preferably -30 to -5 ° C, more preferably -25 to -10 ° C. Moreover, that whose specific gravity is 0.89-0.91 is preferable, and what is 0.8917-0.9065 is more preferable. Furthermore, that whose carbon number is 20-35 is preferable, and the thing of 21-33 is more preferable.

The pressure-sensitive adhesive is prepared as a solution of the pressure-sensitive adhesive component by dissolving the thermoplastic elastomer and the plasticizer, which are the main components constituting the pressure-sensitive adhesive, by adding an organic solvent. The mixing ratio of the thermoplastic elastomer and the plasticizer is usually 3:97 to 97: 3, preferably 5:95 to 95: 5, more preferably 10:90 to 90:10, as a mass ratio. Scope. Moreover, as said organic solvent, the solvent which can melt | dissolve said main component in common, for example, toluene, is normally used. The amount of the organic solvent used is not particularly limited, but is usually 150 to 400 parts by mass, preferably 200 to 300 parts by mass, based on a total of 100 parts by mass of the main components, the elastomer and the plasticizer. Part.

  The pressure-sensitive adhesive prepared as described above can contain the above-mentioned near-infrared absorbing compound, ultraviolet absorbing compound and the like. If the adhesiveness is hindered, the adhesive strength can be reinforced by blending the below-mentioned anchor adhesive component.

  The above-mentioned pressure-sensitive adhesive layer is usually formed by applying the above-mentioned pressure-sensitive adhesive solution to the surface constituting the adhesive interface and drying it. The amount of the pressure-sensitive adhesive solution applied is usually 10 to 100 μm after drying, and practically 25 to 50 μm. The above coating method may be a known method, and examples thereof include a method using a die coater, a bar coater, a knife coater, etc. in addition to a roller coating method, a brush coating method, a spray coating method, and a dip coating method. The coating layer is usually dried for 30 to 120 seconds in hot air at 80 to 150 ° C., preferably 40 to 90 seconds in hot air at 100 to 130 ° C., thereby forming an adhesive layer. .

When applying the above-mentioned pressure-sensitive adhesive solution, it is preferable to apply only to the surface of the layer having higher flexibility among both layers constituting the interface. That is, it is preferable that the pressure-sensitive adhesive solution is usually applied to the bonding surface of the functional film, and the pressure-sensitive adhesive surface formed after drying is sequentially superposed from the edge of the adherend surface. As a result, coupled with the property that air bubbles inherent to the pressure-sensitive adhesive are difficult to entrain, it is possible to greatly suppress entrainment of air bubbles at the adhesive interface. Furthermore, in the unlikely event that air bubbles are involved, the excellent rework property inherent to this pressure-sensitive adhesive can be easily peeled without fouling the peeled surface of the adhesive interface, and can be suitably joined again with good transparency. it can. As a result, it is possible to avoid a defective product due to entrainment of bubbles in the adhesive interface.

As described above, the pressure-sensitive adhesive layer used in the present invention can be easily peeled off without forming the so-called adhesive residue of the pressure-sensitive adhesive on the peeled surface, and can be suitably bonded again. . A release layer can be coated on the surface on which the above-mentioned pressure-sensitive adhesive layer is formed for the convenience of handling until it is adhered to the adherend surface. As a material constituting such a release layer, a known material can be adopted. Specifically, for example, a polyethylene terephthalate (PET) film whose surface is treated with a release silicone agent, and a surface having a release property are used. Examples include paper treated with a silicone agent and polyolefin film.

It should be noted that the adhesive strength is such that it cannot be easily peeled off at a predetermined quality, that is, when it can be bonded without entraining bubbles, by leaving it for a long period of time, or by aging at an elevated temperature. Can be raised. As such accelerated aging conditions, for example, the conditions of 2 to 6 days can be shown at 40 to 80 ° C., but the aging can be completed in a short time by raising the temperature further as long as the heat resistance of the layer allows. You can also. As described above, the adhesive strength is strengthened by aging. However, when it is required to separate the raw material from the substrate, the PDP surface and the functional film layer when recovered as a waste product, it is possible to select a paste by selecting the aging conditions and the peeling conditions. The adhesive interface can be peeled off without the rest.

  When it is desired to further strengthen the adhesive strength between the functional film and the pressure-sensitive adhesive layer, an anchor layer is preferably interposed between the pressure-sensitive adhesive layer and the functional film. Further, when it is desired to enhance the adhesion strength between the PDP surface or the transparent substrate at the interface where peeling is not planned at a later date, such as an adhesion interface, an adhesive component for anchor described later can be added to the adhesive. . When such an anchor adhesive component is blended, the anchor layer adhesive to be blended may basically be used as it is with the anchor adhesive described below, and the blending amount of the adhesive component The amount is 0.1 to 150 parts by mass, preferably 1 to 100 parts by mass, depending on the magnitude of adhesive strength expected as solids with respect to 100 parts by mass of solids. In addition, when the above-mentioned anchor adhesive layer is provided and when the anchor adhesive component is blended, for use in the quality stabilization, before use or shipment, it is 2 to 2 in an environment of 40 to 80 ° C. Aging for 60 days is preferred.

Although it does not specifically limit as said adhesive agent for anchors, For example, the adhesive agent component which contains a carboxylic acid modified thermoplastic elastomer and a crosslinking agent as a main component is mentioned suitably.

  As the carboxylic acid-modified thermoplastic elastomer constituting the anchor adhesive, various carboxylic acid-modified styrene-based plastic elastomers can be used. Examples of the carboxylic acid modification include aliphatic saturated monocarboxylic acids such as propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, vivalic acid, lauric acid, myristic acid, palmitic acid, stearic acid; succinic acid, Aliphatic saturated dicarboxylic acids such as glutaric acid, adipic acid, hymelic acid, suberic acid, azelaic acid and sebacic acid; aliphatic unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, oleic acid; and , May be derived from an aliphatic unsaturated dicarboxylic acid such as maleic acid, fumaric acid, citraconic acid or mesaconic acid. Among these, those modified with an aliphatic unsaturated dicarboxylic acid are preferable, and those modified with maleic acid are more preferable.

  The carboxylic acid-modified thermoplastic elastomer may be, for example, a hydrogenated carboxylic acid-modified thermoplastic elastomer, such as a hydrogenated carboxylic acid-modified styrene-butadiene elastomer, specifically a maleic acid-modified SEBS elastomer. Is mentioned. In addition, when a hydrogenated carboxylic acid-modified styrene-butadiene elastomer is used as the hydrogenated plastic elastomer, the melt index is, for example, 2.5 to 25 g / 10 min under the conditions of 200 ° C. and 5 kg. What is is preferable and what is 3-7 g / 10min is more preferable.

  In the present invention, when a hydrogenated carboxylic acid-modified thermoplastic elastomer is used, the hydrogenation rate is preferably substantially 100%, but may be less than that as long as the effect of the present invention is obtained. Good. When a carboxylic acid-modified SEBS elastomer is used, the mass ratio of styrene: ethylene + butylene is, for example, preferably 10:90 to 40:60, and more preferably 20:80 to 30:70. Further, the acid value of the hydrogenated carboxylic acid-modified thermoplastic elastomer is preferably 2 to 10. Within the range, those having an acid value of less than 3 can be colorless and transparent, while those having an acid value of 3 to 10 are yellowish. Examples of commercially available carboxylic acid-modified thermoplastic elastomers or hydrogenated products thereof include Tuftec M1911, M1913, M1943 (trademark, manufactured by Asahi Kasei Kogyo Co., Ltd.), and FG-1901X (trademark, Kraton Polymer). Company products).

  The type of the crosslinking agent to be blended in the anchor adhesive layer is not particularly limited and can be appropriately determined from known crosslinking agents in consideration of the type of carboxylic acid-modified thermoplastic elastomer to be used. For example, Coronate HL (hexamethylene diisocyanate HDI-TMP adduct) (trademark, product of Nippon Polyurethane Industry Co., Ltd.) can be used.

  The compounding ratio of the carboxylic acid-modified thermoplastic elastomer and the crosslinking agent is not particularly limited, but from the viewpoint of the balance between the adhesiveness of the adhesiveness to the base sheet and the adhesiveness to the pressure-sensitive adhesive layer. For example, 100: 1 to 2: 1, preferably 100: 1 to 4: 1, more preferably 50: 1 to 12: 1.

  In addition to the main components described above, additives such as antistatic agents can be added to the adhesive component. Examples of the antistatic agent include Elegan 264wax (trademark, manufactured by Nippon Oil & Fats Co., Ltd.) which is a cationic antistatic agent. The amount of the antistatic agent is usually based on the mass of the adhesive. 0.1 to 3.6% by mass, preferably 0.6 to 1.8% by mass. By setting the amount within such a range, the occurrence of so-called “Yuzuhada” can be satisfactorily prevented.

  The above-mentioned anchor adhesive layer is prepared by dissolving the above carboxylic acid-modified thermoplastic elastomer, crosslinking agent and other additives in an appropriate organic solvent to form an adhesive solution, which is applied to the surface of the base sheet. And dried to form. The organic solvent is not particularly limited as long as it has solubility in the above elastomer, and for example, toluene can be preferably mentioned. Further, the amount of the organic solvent used is not limited so long as the viscosity of the solution to which the organic solvent is added can be used as an adhesive solution. Usually, the total amount of the elastomer and the plasticizer as the main components is 100 parts by mass. On the other hand, it is 200-500 mass parts, Preferably it is 250-350 mass parts.

  The application method of the anchor adhesive solution may be a known method, but specific examples include a roller coating method, a brush coating method, a spray coating method, a dip coating method, a die coater, a bar coater, and a knife coater. An application method using such as is mentioned. The coating amount is not particularly limited, but usually the thickness after drying is 1 to 50 μm, preferably 1 to 15 μm, more preferably 2 to 5 μm. The coating layer of the above adhesive solution is usually used as an anchor adhesive layer by drying in warm air at 80 to 150 ° C. for 20 to 60 seconds, preferably in hot air at 100 to 130 ° C. for 30 to 50 seconds. It can be applied as an anchor layer of an adhesive layer described later. On the surface of the anchor adhesive layer thus formed, the pressure-sensitive adhesive solution having excellent reworkability can be easily applied to form a pressure-sensitive adhesive layer.

  The feature of the present invention is to use a specific adhesive for bonding. Therefore, it is not substantially affected by the structure of each functional layer, and basically adheres to the bonding surface of the base film forming the functional layer and the surface of the transparent substrate for the optical filter as the adherend or the front surface of the PDP panel. Affected by. However, when the functional films are overlapped and joined, it is affected by the characteristics of the functional layer surface. Therefore, in the present embodiment, the present invention will be described in detail by taking the case of an external light reflection preventing function film as a representative example of the function film in consideration of both of the above effects.

In the present invention, the bonding characteristics of the functional film were evaluated by the following evaluation methods.
(Evaluation method for adhesion / re-adhesion strength to adherend surface):
After cutting a strip-shaped test piece having a width of 25 mm and a length of 250 mm from the functional film with the pressure-sensitive adhesive layer to peel off the release film on the surface of the pressure-sensitive adhesive layer, JIS Z 0237 is used with an AUTOGRAPH AGS-50D manufactured by Shimadzu Corporation. According to the adhesive strength test method, the pressure-sensitive adhesive layer surface was pressure-bonded to the adherend surface, and the presence or absence of entrained bubbles at the adhesive interface was evaluated with a 100-fold microscope, and then left at 30 ° C. for 30 minutes; With respect to what was left in an oven at 80 ° C. for 30 minutes, the functional film with the adhesive layer was peeled off from the surface of the adherend by the peeling angle 180 ° method at a peeling speed of 300 mm per minute. The adhesive strength (adhesive strength to the adhesive surface) was measured, and the average value of the measured values of each of the three test pieces was taken as the adhesive strength. Furthermore, the presence or absence of adhesive residue on the adherend surface was observed with a 100 × microscope. Subsequently, for the test piece aged at 30 ° C. for reworkability evaluation, the pressure-sensitive adhesive layer surface was again pressure-bonded to the adherend surface, and the presence or absence of rough skin on the pressure-sensitive adhesive interface was observed with a 100 × microscope. Again, measure the adhesive force (adhesive surface adhesive strength) between the adhesive layer surface and the adherend surface when peeling at a peeling rate of 300 mm per minute by the 180 degree peeling method, and each of the three tests The average value of the measured values of the pieces was defined as the adhesive force during re-adhesion.

[Example 1]
(1)
High refractive index layer coating solution Pentaerythritol triacrylate 1.0 part by mass, tetraethoxysilane 0.1 part by mass, zirconium oxide particles 1.7 parts by mass with an average primary particle diameter of 0.01 μm, a polymerization initiator A coating solution for a high refractive index layer was prepared by mixing 0.2 part by mass of 1-hydroxycyclohexyl phenyl ketone and 97 parts by mass of isobutyl alcohol as a solvent.

(2)
Low refractive index layer coating solution 0.8 parts by mass of tetraethoxysilane, 98.4 parts by mass of ethanol as a solvent, and 0.8 parts by mass of 0.1N hydrochloric acid were mixed to obtain a coating solution for the low refractive index layer. .

(Adhesive solution)
17 parts by mass of SEBS elastomer (mass average molecular weight: 250,000) and 83 parts by mass of naphthenic oil (flash point: 220 ° C., pour point: -25 ° C., specific gravity: 0.8387, carbon number: 5-6) as a plasticizer: 270 It melt | dissolved using the mass part, and obtained about 27 mass% adhesive solution.

(External light anti-reflection film)
On one side of a 75 μm thick PET film (Lumirror 75T60, manufactured by Toray Industries, Inc .: hereinafter referred to as “base PET film”) as a base film, the thickness after drying the low refractive index layer coating solution is 0.4 μm. After applying for 5 minutes at room temperature and heating at 80 ° C. for 20 minutes to provide a low refractive index layer, the above high refractive index layer coating solution was dried in the same manner. The film was applied to a thickness of 0.4 μm and dried at 40 ° C. for 10 minutes. Furthermore, the low refractive index layer coating solution is applied again as the outermost layer so that the thickness after drying is 0.4 μm, dried at room temperature for 5 minutes, and then heated at 80 ° C. for 20 minutes to reduce the low refractive index. A layer was formed to obtain an external light antireflection function film.

  The adhesive coating solution is applied to the back surface (non-coated layer surface) of the external light antireflection film so that the thickness after drying is 45 μm, and is heated and dried in hot air at 100 ° C. for 1 minute. An external light antireflection function film with an adhesive layer was obtained, and a 75 μm thick PET film (hereinafter, referred to as a release film) having a surface treated with silicone as a release layer was bonded to the surface of the adhesive layer of this functional film. .

  The above external light antireflection function film with an adhesive layer was aged in a room at 45 ° C. for 4 days, and then the glass surface as the surface of the PDP and the transparent substrate was used as an adherent surface and left at 30 ° C. for 30 minutes. Measured according to the method for evaluating the adhesion / re-adhesion force to the surface of the adherend, and those that were left in an oven at 80 ° C. for 30 minutes. The protective functional film is laminated on the same kind of glass surface in two layers, the external light antireflection layer side surface of the functional film of the first layer is the adherend surface, measured in the same manner as above, The results are shown in Table 1 (in the table,-items were not measured).

[Example 2]
(Anchor layer adhesive solution)
Tuftec M1911 maleate modified SEBS (melt index is 3.5 g / 10 min, styrene: ethylene + butylene mass ratio is 30:70, acid value is 2, Asahi Kasei Kogyo Co., Ltd.) 13 parts by mass, toluene 87 mass The mixture was poured into the part and dissolved using a propeller stirrer. To 100 parts by mass of this solution, 1.04 parts by mass of Coronate HL and 0.13 parts by mass of Elegan 264wax as an antistatic agent were added at room temperature to obtain an adhesive solution.

First, the anchor layer adhesive is applied to the surface (base PET film surface) opposite to the surface that is the external light antireflection function layer of the same external light antireflection function film used in Example 1. Then, using a Mayer bar, the coating was applied so that the thickness after drying was 2 μm, and dried in hot air at 120 ° C. for 40 seconds to form an anchor adhesive layer. On this adhesive layer for anchor, the pressure-sensitive adhesive layer was applied so that the thickness after drying was 45 μm in the same manner as in Example 1, and dried to obtain an external light antireflection function film. A 75 μm thick PET film treated with silicone was bonded to the surface of this adhesive layer to obtain an external light antireflection function film with an adhesive.

About the said external light antireflection function film with an adhesive layer, it is the same as the case of Example 1, and when the glass surface as the surface of PDP and a transparent substrate is used as an adhesion surface, said adhesive layer When the external light antireflection function film is attached to the same kind of glass surface in two layers, the external light antireflection layer side surface of the functional film of the first layer is used as the adherend surface. Measured in accordance with the method for evaluating the adhesion / re-adhesion force to the surface of the adherend with respect to those left for 30 minutes at 80 ° C. for 30 minutes in an 80 ° C. oven, and the results are shown in Table 1. (In the table,-items were not measured).

The bonding method of the present invention for the functional film to the front surface of the PDP, the transparent substrate of the optical filter disposed on the front surface of the PDP, the surface of the PDP or another functional film already bonded to the transparent substrate surface of the optical filter is , Because the bonding interface is bonded through an adhesive layer that has excellent reworking properties with thermoplastic elastomer and plasticizer as the main components and less entrainment of bubbles, downgrade to defective products due to entrainment of bubbles between layers is reduced. The yield of non-defective products increases, and therefore the cost of non-defective products can be reduced, and the industrial effect is great.

Claims (7)

A pressure-sensitive adhesive layer mainly composed of a thermoplastic elastomer and a plasticizer is formed on the bonding surface of the functional film in advance, and the surface of the pressure-sensitive adhesive layer is formed on the transparent substrate surface for an optical filter, on the front surface of the plasma display panel, or A method for bonding a functional film, characterized by bonding to the surface of the substrate or another functional film already bonded to the front surface of the panel.
2. The functional film joining method according to claim 1, wherein the thermoplastic elastomer is a polymer composed of a block segment composed of a styrene monomer unit and a rubber monomer unit.
The method for joining functional films according to claim 1 or 2, wherein the plasticizer is naphthenic oil and / or paraffin oil.
4. Bonding of a functional film according to any one of claims 1 to 3, wherein an adhesive composition component further comprising a carboxylic acid-modified thermoplastic elastomer and a crosslinking agent as main components is blended with the adhesive component. Method.
5. An anchor layer made of an adhesive containing a carboxylic acid-modified thermoplastic elastomer and a crosslinking agent as main components is provided in advance on the bonding surface of the functional film before forming the pressure-sensitive adhesive layer. The functional film joining method according to any one of the above.
An optical filter in which one or two or more functional films are bonded and laminated on one or both sides of a transparent substrate surface, and is disposed with a space in front of the plasma display panel, the functional film and the transparent substrate surface And / or the bonding interface between the functional film and the surface of another functional film already laminated is bonded by the bonding method according to any one of claims 1 to 5. An optical filter.
A plasma display panel in which one or more functional films are bonded and laminated on the front surface of the plasma display panel, and between the front surface of the plasma display panel and the functional film and / or other functions already laminated A plasma display panel, wherein a bonding interface between the film surface and the functional film is bonded by the bonding method according to claim 1.