JP2008195830A - Ultraviolet absorbing film and panel filter produced by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet absorbing film having excellent productivity, giving excellent transparent feeling even by shielding the light of 410 nm wavelength and having excellent transparency in the visible range and to provide a filter for a plasma display panel produced by using the film, and having excellent degradation preventing performance of an infrared absorbing colorant and excellent adhesiveness to an infrared absorbing layer and a hard-coat layer. <P>SOLUTION: The invention provides an ultraviolet absorbing film containing a fluorescent brightener and an ultraviolet absorber and having a light transmittance of ≤30% at 410 nm wavelength and ≥70% at 430 nm wavelength. Preferably, the ultraviolet absorber is a benzotriazole compound or a cyclic imino-ester compound, and the fluorescent brightener is a compound expressed by general formula (I) (in the formula, R<SP>1</SP>and R<SP>4</SP>are each a hydrogen atom, an alkyl group or the like; R<SP>2</SP>and R<SP>3</SP>are each an alkyl group; and [A] is a substituted aryl group or a substituted ethenyl group). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultraviolet absorbing film and a panel filter using the same. More specifically, UV absorption film with excellent UV absorption and visible light transmittance, suitable for plasma display filters, and prevention of malfunctions in remote control and transmission optical communication due to near infrared rays emitted from plasma displays using the same. The present invention relates to a filter for a plasma display panel in which deterioration due to ultraviolet rays of an infrared absorbing layer installed on the front surface of the display is suppressed.

In recent years, plasma display panels have been used as display panels for various types of electronic devices such as large-sized wall-mounted televisions, and their demand is increasing. The number will continue to increase in the future.
Filters for plasma display panels have a layer with functions such as a near-infrared cut layer, an electromagnetic wave cut layer, an antireflection layer that prevents external light from being reflected on the surface, a glare prevention layer, etc. Composed of multiple layers. In particular, the near-infrared cut layer is installed on the front surface of the display for the purpose of preventing malfunctions in remote control and transmission optical communication caused by near-infrared rays emitted from the plasma display panel, and has an important function.

  However, so-called infrared absorbing pigments contained in the near-infrared cut layer, such as diimmonium compounds and fluorine-containing phthalocyanine compounds, are gradually decomposed by ultraviolet rays derived from sunlight, incandescent lamps, halogen bulbs, mercury lamps, etc. There was a problem that the performance deteriorated by long-term use.

  For this reason, a method of applying a layer containing an ultraviolet absorber to the base film constituting the panel filter by coating is proposed. For example, an ultraviolet absorber (2- (2 '-Hydroxy-3', 5'-di-t-butylphenyl)) A method of laminating an ultraviolet absorbing layer by applying a cyclohexanone solution of benzotriazole with a bar coder and drying (for example, patents) However, in this UV absorption layer, it is impossible to obtain a UV blocking effect that is practically sufficient to prevent the deterioration of the infrared absorbing dye.

  Further, as another method, a method is disclosed in which an ultraviolet absorbent is kneaded directly into a base film to impart an ultraviolet absorbing ability to the base film itself (see, for example, Patent Document 2). Accordingly, it is possible to obtain an ultraviolet blocking effect sufficient to prevent the deterioration of the infrared absorbing dye. However, the cyclic imino ester compound exemplified here as an ultraviolet absorber is a suitable material in that it is difficult to sublimate compared to a general ultraviolet absorber, but when melt extruded in the resin extrusion process Since the sublimate is not zero and has a property of bleeding out on the film surface, the problem is that the sublimate or the like adheres to the production apparatus and contaminates the process as the film formation time elapses. Such an ultraviolet absorber causes a defect such as adhering to the film to cause a foreign matter defect, or causing pre-heating, stretching, or adhesion to the cooling roll in the longitudinal stretching step after film formation to cause scratches. In order to reduce the influence of contaminants, for example, roll cleaning work can be performed frequently, but this method causes an increase in cost and a decrease in productivity. In order to suppress undesired sublimation of the UV absorber, a method of dissolving and extruding the resin at a low temperature is conceivable. However, since the resin does not have sufficient fluidity at a low temperature, the filtration pressure of the filter increases. Other problems such as high-precision filtration become difficult.

  Furthermore, in such a UV absorbing film, since it is again exposed to a high temperature in the transverse stretching process, the UV absorber also sublimates in this process and accumulates in the equipment over a long period of time, and then drops and adheres to the film, resulting in foreign matter defects. These foreign matter defects and scratches are fatal defects for optical films with strict quality requirements.

  In general, most of optical films having ultraviolet absorbing ability have absorption edges shorter than 380 nm in order to suppress yellowishness (see Patent Documents 1 to 3). The fact that the absorption edge is a short wave means that the ultraviolet blocking effect is low, so that it is desired to cut light up to 410 nm in particular to block UVA.

  However, when light up to 410 nm is cut, the yellowish color usually becomes stronger. This can be improved by adding a dye / pigment for color tone adjustment, but has the disadvantage of sacrificing the transmittance in the visible region. For this reason, a white laminated polyester film excellent in weather resistance and whiteness in which a fluorescent whitening agent is blended with an ultraviolet absorber to suppress yellowing due to ultraviolet irradiation has been proposed (for example, Patent Documents 4 and 5). (See also), it is difficult to say that the light transmittance in the visible region is sufficient.

As mentioned above, there is no process contamination such as roll dirt, and it is excellent in productivity. Even if it cuts to 410 nm, it is excellent in transparency without yellowing, and it absorbs sufficient infrared rays without sacrificing transmittance in the visible region. It has been difficult to produce a base material for a plasma display panel filter and a plasma display panel filter that have a pigment deterioration prevention performance and are excellent in adhesion to an infrared absorption layer and a hard coat layer.
JP 2002-71942 A JP 2003-1703 A JP 2005-189553 A Japanese Patent Laid-Open No. 11-291432 JP 11-268214 A

  The present invention has been completed in order to solve the above-mentioned problems of the prior art. The object of the present invention is to be excellent in productivity and to be manufactured without process contamination caused by the ultraviolet absorber. A base material for a filter for a plasma display panel, which achieves ultraviolet absorption up to 410 nm, which is a longer wave region, but has no yellow tint in the film itself, excellent transparency, and does not sacrifice the transmittance in the visible region. It is an object to provide a filter for a plasma display panel which is excellent in the ability to prevent deterioration of an infrared-absorbing dye, using the useful UV-absorbing film and the UV-absorbing film of the present invention.

That is, the present invention has the following configuration.
<1> A film containing an optical brightener and an ultraviolet absorber, wherein the light transmittance at a wavelength of 410 nm is 30% or less and the light transmittance at a wavelength of 430 nm is 70% or more. UV absorbing film.
<2> The ultraviolet absorbing film according to <1>, wherein the film is a biaxially oriented polyester film and has a light transmittance of 75% or more at a wavelength of 430 nm.
<3> The ultraviolet absorber is at least one selected from the group consisting of benzotriazole compounds and cyclic imino ester compounds, and the biaxially oriented polyester film is substantially free of particles. The ultraviolet absorption film as described in <2>.
<4> The ultraviolet light absorbing film according to <2> or <3>, wherein the fluorescent brightening agent contains a compound represented by the following general formula (I).

In general formula (I), R ¹ and R ⁴ represent a hydrogen atom, an alkyl group or an alkoxy group, and R ² and R ³ represent an alkyl group. [A] represents a substituted aryl group or a substituted ethenyl group.
<5> A filter for a plasma display panel, wherein an infrared ray absorbing layer is provided on at least one side of the ultraviolet ray absorbing film according to any one of <2> to <4>.

  In general, the optical brightener comprises a compound having the property of absorbing light having a wavelength of about 320 to about 410 nm and emitting light having a wavelength of about 410 to about 500 nm. The fabric dyed with these fluorescent whitening agents is added with blue light having a wavelength of about 410 to about 500 nm which is newly emitted by the fluorescent whitening agent in addition to the original yellow reflected light. It is known that the energy of visible light is increased by the amount of the fluorescent effect, and as a result, the dyed fabric itself seems to have increased in white color and is whitened. As a result of investigations, the inventors have found that a similar effect is produced even with a resin material containing an ultraviolet absorber. That is, in a molded product in which an ultraviolet absorber is added to a thermoplastic resin, when the amount of the ultraviolet absorber is adjusted so as to cut ultraviolet rays of 410 nm or less, the reflected light feels yellow. The present invention has been completed by finding that the reflected light is whitened by adding an appropriate amount of.

  According to the present invention, the film itself is excellent in productivity, can be manufactured without process contamination due to the ultraviolet absorber, and achieves ultraviolet absorption up to 410 nm, which is a long wave region from 380 nm, while the film itself is yellowish. UV absorbing film useful as a substrate for a filter for a plasma display panel, which is superior in transparency and does not sacrifice the transmittance in the visible region, and an infrared absorbing layer using the ultraviolet absorbing film of the present invention Is capable of providing a plasma display panel filter excellent in ultraviolet absorption ability and visible light transmission.

Hereinafter, the present invention will be described in detail.
<Ultraviolet absorbing film>
First, the ultraviolet absorbing film of the present invention will be described. The ultraviolet absorbing film of the present invention is a film containing a fluorescent brightening agent and an ultraviolet absorber, and has a light transmittance of wavelength 410 nm of 30% or less and a light transmittance of wavelength 430 nm of 70% or more. It is characterized by being. This film is formed by containing a resin material used as a film base material with an ultraviolet absorber and a tendency foil increasing agent.

As the film constituting the ultraviolet absorbing film used in the present invention, a film made of a resin having desired strength and visible light permeability can be appropriately selected and used. For example, thermoplastic polyester, polycarbonate, amorphous From resins selected from olefin, polyether, polyetherketone, polyphenylene ether, polymethacrylate, polystyrene, acrylic, polyamide, polyetherimide, polyimide, polyarylate, polyethersulfone, polyarylene sulfide, silicon resin, fluororesin, etc. A polyester film is preferable.
The film substrate may be composed of a plurality of types of resins, a copolymer including a plurality of components, or a laminate composed of a plurality of layers.
More specifically, examples of the polyester film include polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, or a film made of a copolymer mainly composed of components of these resins. Among these, a biaxially stretched polyethylene terephthalate film is particularly suitable from the viewpoints of mechanical properties, heat resistance, transparency, price, and the like.
Hereinafter, the aspect using the polyester-type resin which is a preferable film base material is demonstrated.

In the case of using the copolymer having the polyester-based component as a main component, the other component includes a dicarboxylic acid component, more specifically, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid; Aromatic dicarboxylic acids such as acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid; polyfunctional carboxylic acids such as trimellitic acid and pyromellitic acid are used. The glycol component includes fatty acid glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol and neopentyl glycol; aromatic glycols such as p-xylene glycol; alicyclic groups such as 1,4-cyclohexanedimethanol. Glycol: Polyethylene glycol having an average molecular weight of 150 to 20,000 is used.
In the present invention, the film base material is preferably composed mainly of a polyester-based component, and can be used in combination as described above from the viewpoint of maintaining the film strength, transparency, and heat resistance of the polyester-based resin. The weight ratio of such copolymerization components is preferably less than 20% by weight.

  Moreover, the intrinsic viscosity of the resin pellet used for formation of the polyester-type film as a film base material based on this invention has the preferable range of 0.45-0.70gl / g. In this range, the effect of improving tear resistance can be achieved, and the filtration pressure can be maintained in an appropriate range, so that high-precision filtration can be performed.

The base film according to the present invention is usually melt-extruded into a film shape as described later, and cast into a film with a metal roll to form a film. In this casting, it is recommended to make electrostatic contact in order to improve the adhesion between the molten film and the metal roll. Therefore, it is desirable that the polyester resin constituting the base material has a low melting specific resistance value.
Specifically, the melt specific resistance value at 275 ° C. of the polyester resin is preferably 0.45 × 10 ⁸ Ωcm or less, and more preferably 0.30 × 10 ⁸ Ωcm or less. On the other hand, if the melt specific resistance value of the polyester resin is too low, the base film tends to be affected by static electricity and the handling property tends to be lowered. Therefore, the melt specific resistance value at 275 ° C. of the polyester resin is preferably 0.10 × 10 ⁸ Ωcm or more, and more preferably 0.12 × 10 ⁸ Ωcm or more. In addition, the fusion specific resistance value prescribed | regulated by this invention is a value measured by the method employ | adopted in the Example mentioned later.

The melt specific resistance value of the polyester resin can be controlled within the preferred range by including a magnesium compound and a phosphorus compound in the polyester resin.
Magnesium in the magnesium compound has an action of lowering the melt specific resistance value of the polyester resin. From the viewpoint of effectively exhibiting such an action and suppressing the generation of foreign matters due to the magnesium compound and the coloration of the polyester resin, the amount of the magnesium compound in the polyester resin is 40 ppm in terms of magnesium atom (mass basis, the same applies hereinafter). Above, preferably 45 ppm or more and 70 ppm or less, preferably 65 ppm or less is recommended.

  The phosphorus compound itself does not have an action of reducing the melt specific resistance value of the polyester resin, but can be combined with the magnesium compound to contribute to the reduction of the melt specific resistance value. The reason for this is not clear, but it is thought that the inclusion of a phosphorus compound can suppress the generation of foreign substances and increase the amount of charge carriers. Therefore, the amount of the phosphorus compound in the polyester resin is 10 ppm in terms of phosphorus atom (mass basis, the same shall apply hereinafter) from the viewpoint of effectively exhibiting the above-described effect due to the magnesium compound and suppressing the generation of foreign matter due to the phosphorus compound. Above, preferably 15 ppm or more and 55 ppm or less, preferably 50 ppm or less is recommended.

In this invention, you may include the particle | grains for providing slipperiness in a base film. When the base film is a multilayer, the particles may be included in the intermediate layer and the outermost layer of the base film, but it is preferable that the particles are included only in the outermost layer from the viewpoint of transparency. Examples of the particles in this case include calcium carbonate, calcium oxide, ammonium oxide, calcium phosphate, silica, zinc oxide, silicon carbide, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and sulfide. Examples thereof include inorganic particles such as molybdenum, crosslinked polymer particles, and organic particles such as calcium oxalate.
Among these, silica is most suitable because it has a relatively close refractive index to that of the polyester resin and high transparency can be easily obtained.
These average particle diameters are preferably 1 to 3 μm. Moreover, the addition amount of particle | grains is preferable 0.003-0.01 weight% from a viewpoint of transparency and sliding.

  In addition, in order to ensure still higher transparency, it is preferable that particles for imparting slipperiness are not substantially present in the base film. Note that “substantially no particles” means that the abundance of particles is below the detection limit of the fluorescent X-ray analysis method in the film base material itself on which the adhesive modified resin layer is not laminated.

  As means for imparting slipperiness to the polyester base film, there is a method of laminating an easy adhesion layer in-line on the film base as well as a method of adding particles to the film base itself. In this way, if the easy-adhesion layer laminated in-line is provided with slipperiness by containing fine particles with a uniform particle size, it is possible to impart good winding properties and a function to prevent scratches, so that a polyester base film The addition of particles for the purpose of easy adhesion to the inside is not particularly necessary.

Examples of particles that can be included in the easy adhesion layer laminated on the film substrate include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, Inorganic particles such as molybdenum sulfide, crosslinked polymer particles, and organic particles such as calcium oxalate can be mentioned. Among them, silica is most suitable because it has a relatively close refractive index to that of a polyester resin and high transparency is easily obtained. is there.
The average particle size of the particles contained in the easy-adhesion layer is preferably in the range of 1 μm to 3 μm.

The thickness of the ultraviolet absorbing film of the present invention is appropriately selected according to the purpose of use, but when used as a base film for a filter for plasma display, which is an optimal application, it has excellent strength, dimensional stability, and ease of handling. From the viewpoint, it is preferably a biaxially oriented thermoplastic resin film having a thickness of 50 μm or more, and the upper limit of the thickness of the base film is not particularly limited, but is 300 μm or less from the viewpoint of handleability and price as an optical member. It is recommended that there be.
If it is the said thickness, the kind of thermoplastic resin which is the constituent material will not be specifically limited.

Next, the ultraviolet absorber added to the base film in the ultraviolet absorbing film of the present invention will be described.
In general, ultraviolet absorbers are compounds that have the property of absorbing ultraviolet rays and returning them to heat, and are classified into organic ultraviolet absorbers and inorganic ultraviolet absorbers, but organic ultraviolet absorbers are preferred from the viewpoint of transparency. . Further, examples of the organic ultraviolet absorber include benzotoazole, benzophenone, salicylic acid, cyanoacrylate, cyclic imino ester, and combinations of these compounds.

Examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) -2H-benzotriazole and 2- (2′-hydroxy-5′-t-butylphenyl) -2H-benzo. Triazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -2H-benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) -5-chloro-2H-benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-amylphenyl) ) -2H-benzotriazole, 2- (2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl) -2H-benzotriazole, 2- (2′-hydroxy-5 ′-(methacryl) Royloxypropyl) phenyl) -2H-benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5 ′-(methacryloyloxyethyl) phenyl) -2H-benzotriazole, 2- (2′-hydroxy -5'-t-butyl-3 '-(methacryloyloxyethyl) phenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-(methacryloyloxyethyl) phenyl) -5-chloro-2H-benzo Although triazole etc. are mentioned, it is not limited to these.
Further, a compound having a large molecular weight in which the ultraviolet absorption skeleton is dimerized through methylene or the like such as ADK STAB LA-31 (trade name: manufactured by Asahi Denka Co., Ltd.) is also preferably used.

  Examples of the cyclic imino ester-based ultraviolet absorber include the following. 2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3, 1-benzoxazin-4-one, 2-phenyl-3,1-benzoxazin-4-one, 2- (1- or 2-naphthyl) -3,1-benzoxazin-4-one, 2- (4 -Biphenyl) -3,1-benzoxazin-4-one, 2-p-nitrophenyl-3,1-benzoxazin-4-one, 2-m-nitrophenyl-3,1-benzoxazin-4-one 2-p-benzoylphenyl-3,1-benzoxazin-4-one, 2-p-methoxyphenyl-3,1-benzoxazin-4-one, 2-o-methoxyphenyl-3,1-benzoxazine -4-one, 2 Cyclohexyl-3,1-benzoxazin-4-one, 2-p- (or m-) phthalimidophenyl-3,1-benzoxazin-4-one, 2,2 ′-(1,4-phenylene) bis ( 4H-3,1-benzoxazinon-4-one), 2,2′-bis (3,1-benzoxazin-4-one), 2,2′-ethylenebis (3,1-benzoxazine-4) -One), 2,2'-tetramethylenebis (3,1-benzoxazin-4-one), 2,2'-decamethylenebis (3,1-benzoxazin-4-one), 2,2 ' -P-phenylenebis (3,1-benzoxazin-4-one), 2,2'-m-phenylenebis (3,1-benzoxazin-4-one), 2,2 '-(4,4' -Diphenylene) bis (3,1-benzoxazi -4-one), 2,2 '-(2,6- or 1,5-naphthalene) bis (3,1-benzoxazin-4-one), 2,2'-(2-methyl-p-phenylene) ) Bis (3,1-benzoxazin-4-one), 2,2 ′-(2-nitro-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2 ′-(2 -Chloro-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2 '-(1,4-cyclohexylene) bis (3,1-benzoxazine-4-one).

  1,3,5-tri (3,1-benzoxazin-4-on-2-yl) benzene, 1,3,5-tri (3,1-benzoxazin-4-on-2-yl) naphthalene, And 2,4,6-tri (3,1-benzoxazin-4-one-2-yl) naphthalene.

  2,8-dimethyl-4H, 6H-benzo (1,2-d; 5,4-d ′) bis- (1,3) -oxazine-4,6-dione, 2,7-dimethyl-4H, 9H -Benzo (1,2-d; 5,4-d ') bis- (1,3) -oxazine-4,9-dione, 2,8-diphenyl-4H, 8H-benzo (1,2-d; 5,4-d ') bis- (1,3) -oxazine-4,6-dione, 2,7-diphenyl-4H, 9H-benzo (1,2-d; 5,4-d') bis- (1,3) -Oxazine-4,6-dione, 6,6′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-ethyl- 4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6, '-Methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6'-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6 '-Ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6'-ethylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6 , 6′-Butylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6 , 6′-oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6 , 6′-sulfonylbis ( -Methyl-4H, 3,1-benzoxazin-4-one), 6,6'-sulfonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6'-carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-carbonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7′- Methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7′- Bis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7 ′ -Oxybis (2-methyl-4H, 3,1- Benzoxazin-4-one), 7,7′-sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-carbonylbis (2-methyl-4H, 3, 1-benzoxazin-4-one), 6,7′-bis (2-methyl-4H, 3,1-benzoxazin-4-one).

  Examples of the benzophenone ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2, Examples thereof include 2′-dihydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2, -hydroxy-4-methoxy-5-sulfobenzophenone.

Examples of the salicylic acid ultraviolet absorber include phenyl salicylate, pt-butylphenyl salicylate, pn-octylphenyl salicylate, and the like.
Examples of cyanoacrylate-based ultraviolet absorbers include 2-ethylhexyl 2-cyano-3,3-diphenyl acrylate.

  In addition, it is one of preferred embodiments of the present invention to use two or more kinds of ultraviolet absorbers in combination. Among the ultraviolet absorbers described above, benzotoazole and cyclic imino ester are particularly preferable from the viewpoint of durability. From another point of view, it is preferable to use an ultraviolet absorber having a decomposition start temperature of 290 ° C. or higher in order to reduce process contamination during film formation.

Next, the fluorescent whitening agent used in the present invention will be described.
The optical brightener added to the film substrate can be arbitrarily selected from commercially available compounds or new substances depending on the intended use of the UV absorbing film from the viewpoint of durability and solubility. it can. Specific examples thereof [Exemplary Compound (1) to Exemplary Compound (12)] are listed below, but the present invention is not limited thereto.

  Other fluorescent brighteners that can be used in the present invention include those represented by the following general formula (I).

In general formula (I), R ¹ and R ⁴ represent a hydrogen atom, an alkyl group or an alkoxy group, and R ² and R ³ represent an alkyl group. [A] represents a substituted aryl group or a substituted ethenyl group.

R ¹ , R ² , R ³ , R ⁴ and [A] in the general formula (I) of the present invention will be described below. R ¹ and R ⁴ represent a hydrogen atom, an alkyl group or an alkoxy group, preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms. Specific examples of R ¹ and R ⁴ include a hydrogen atom, methyl group, ethyl group, n-propyl group, n-butyl group, n-octyl group, isopropyl group, isobutyl group, 2-ethylhexyl group, t-butyl group, t-amyl group, t-octyl group, cyclopentyl group, cyclohexyl group, methoxy group, ethoxy group, n-propoxy group, n-butoxy group, n-octyloxy group, isopropyloxy group, isobutyloxy group, 2-ethylhexyloxy Group, t-butoxy group, cyclohexyloxy group and the like. R ¹ and R ⁴ are more preferably a hydrogen atom or an alkyl group, and still more preferably a hydrogen atom.

R ² and R ³ represent an alkyl group, preferably an alkyl group having 1 to 16 carbon atoms. Specific examples of R ² and R ³ include methyl group, ethyl group, n-butyl group, n-octyl group, n-hexadecyl group, isopropyl group, isobutyl group, 2-ethylhexyl group, t-butyl group, and t-amyl. Group, t-octyl group, cyclopentyl group, cyclohexyl group and the like. R ² is more preferably a methyl group, an isopropyl group, a t-butyl group, or a cyclohexyl group, and even more preferably a t-butyl group or a cyclohexyl group. R ³ is more preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-octyl group, an n-hexadecyl group or a 2-ethylhexyl group, and more preferably a methyl group, an n-butyl group, an n -An octyl group or a 2-ethylhexyl group.

  [A] represents a substituted aryl group or a substituted ethenyl group, preferably a substituted aryl group having 6 to 40 carbon atoms or a substituted ethenyl group having 8 to 40 carbon atoms. More preferred are substituted aryl groups or ethenyl groups shown below.

In the above formulas, R ^{1 ′} , R ^{2 ′} , R ^{3 ′} and R ^{4 ′} have the same meanings as R ¹ , R ² , R ³ and R ⁴ in the general formula (I). m represents an integer of 1 to 5. X and Y represent an alkyl group, an aryl group, an alkoxy group, an amino group, an alkylamino group, an arylamino group or a hydroxyl group.

In detail, X and Y other than amino group and hydroxyl group are alkyl groups such as methyl group, ethyl group, isopropyl group, t-butyl group and cyclohexyl group, aryl groups such as phenyl group, p-tolyl group and 1-naphthyl group. Group, alkoxy group such as methoxy group, ethoxy group, isopropoxy group, methylamino group, ethylamino group, octylamino group, dimethylamino group, alkylamino group such as N-methyl-N-ethylamino group, anilino group, An arylamino group such as an N-methylanilino group can be exemplified. More preferable X and Y are an aryl group, an alkoxy group, or an anilino group.
Z represents a cyano group or an alkoxycarbonyl group.

  The compound represented by the general formula (I) is more preferably a compound represented by the following general formula (II).

In general formula (II), R ⁵ and R ⁷ have the same meaning as R ² in general formula (I), and R ⁶ and R ⁸ have the same meaning as R ³ . n represents 1 or 2. These compounds can be synthesized by the method described in JP-A-11-29556.

  Specific examples [Exemplary Compound (13) to Exemplified Compound (30)] of the fluorescent enhancer represented by Formula (II) that can be used in the present invention are listed below, but the present invention is limited to these. It is not a thing.

In the present invention, the amount of the optical brightener and the ultraviolet absorber added to the polyester varies depending on the molecular weight, physical properties, properties, etc. of the optical brightener and the ultraviolet absorber, but cannot be uniquely determined. The merchant can easily determine this by doing some testing.
The addition amount of the fluorescent whitening agent and the ultraviolet absorber is preferably 0.1 to 5% by weight, more preferably 0.3 to 3% by weight, based on the total amount of the polyester. If the addition amount is less than 0.1% by weight, the effect of preventing UV deterioration is small. Conversely, if the addition amount exceeds 5% by weight, the film forming property of the polyester film is lowered, which is not preferable.
Further, from the viewpoint of sufficient UV absorbing ability and protection of the infrared absorbing layer when applied to a panel filter described later, the content of the UV absorber in the film substrate is at least 0.1% by weight. It is preferable that
The mixing ratio of the fluorescent whitening agent and the ultraviolet absorber is usually preferably in the range of 10/90 to 90/10, more preferably in the range of 30/70 to 70/30, in terms of molar ratio.

  As a method of blending the fluorescent whitening agent and the ultraviolet absorber with the base film, known methods can be appropriately combined and employed. For example, by using a kneading extruder in advance, blending the dried UV absorber and the polyester raw material to prepare a master batch, and by mixing the predetermined master batch and the polyester raw material when forming the base film Can be blended.

At this time, the concentration of the optical brightener and the UV absorber in the master batch is preferably 5 to 30% by weight in order to disperse them uniformly and economically blend them. As a condition for producing the master batch, it is preferable to use a kneading extruder and to extrude it at a temperature not lower than the melting point of the polyester raw material and not higher than 290 ° C. for 1 to 15 minutes.
The viscosity of the master batch is appropriately maintained in the above temperature range, and uniform dispersibility can be ensured. Further, when the extrusion time is within this range, the fluorescent whitening agent and the ultraviolet absorber can be uniformly mixed. A stabilizer, a color tone adjusting agent, an antistatic agent and the like may be added as necessary when preparing the masterbatch.

The ultraviolet-absorbing film of the present invention can be obtained by forming this master batch by a conventional method. In the present invention, since a biaxially oriented thermoplastic film is suitable, the film is preferably formed by a biaxial stretching method.
Since the ultraviolet absorbing film of the present invention thus obtained contains an ultraviolet absorber and a fluorescent brightening agent, the light transmittance at a wavelength of 410 nm is 30% or less, and the light transmittance at a wavelength of 430 nm is 70%. Above, preferably 75% or more is achieved.
This light transmittance can be measured using a known spectrophotometer or the like.

(Production method of UV absorption)
The production method of the ultraviolet absorbing film useful for the plasma display filter of the present invention will be described in detail with respect to an example in which polyethylene terephthalate (hereinafter referred to as PET) pellets are used as the raw material of the base film, but the production method is naturally limited to this. Is not to be done.

  Usually, PET pellets are transferred by air using a predetermined pipe, and it is preferable to use HEPA filter and purified air to prevent dust contamination. The HEPA filter used is preferably a filter having a performance of cutting 95% or more of dust having a nominal filtration accuracy of 0.5 μm or more.

First, a master batch obtained by blending PET pellets, a fluorescent brightening agent, and an ultraviolet absorber in a predetermined ratio is sufficiently mixed. The masterbatch is a pellet that does not substantially contain particles intended to impart slipperiness. The mixed raw material pellets are sufficiently dried in vacuum, then supplied to an extruder, melted and extruded into a sheet, and cooled and solidified on a casting roll to form an unstretched PET sheet. At this time, it is preferable that the resin temperature up to the extruder melt section, kneading section, polymer tube, gear pump and filter is 280 to 290 ° C., and the resin temperature up to the subsequent polymer tube and flat die is 270 to 280 ° C.
In addition, high-precision filtration is performed at any place where the molten resin is maintained at about 280 ° C. in order to remove foreign substances contained in the resin. The filter medium used for high-precision filtration of molten resin is not particularly limited, but from the viewpoint of excellent removal performance of aggregates and high-melting-point organic substances mainly composed of Si, Ti, Sb, Ge, and Cu, a sintered stainless steel It is preferable to use a filter medium.

  The filtration particle size (initial filtration efficiency 95%) of the filter medium in the high-precision filtration treatment is preferably 20 μm or less, particularly preferably 15 μm or less. When the filter particle size of the filter medium (initial filtration efficiency 95%) exceeds 20 μm, foreign matters having a size of 20 μm or more cannot be sufficiently removed. Productivity may be reduced by performing high-precision filtration of molten resin using a filter medium with a filter particle size (initial filtration efficiency of 95%) of 20 μm or less, but to obtain a film with few projections due to coarse particles This is an important process.

  Foreign matter present in the raw polymer, or fluorescent whitening agent and ultraviolet absorber sublimate and contaminate the roll, and if they are attached to the film, polyester molecules around this foreign matter in the stretching process during film formation The orientation of the film is disturbed, and optical distortion occurs. Because of this optical distortion, it is recognized as a defect that is considerably larger than the actual size of the foreign material, so that the quality is significantly impaired. For example, a foreign substance having a size of 20 μm may be optically recognized as a size of 50 μm or more, and may be recognized as an optical defect having a size of 100 μm or more. In order to obtain a highly transparent film, it is desirable not to contain particles for imparting slipperiness in the base film, or to contain only a small amount so as not to inhibit transparency, but the particle content is low. As the transparency of the film increases, optical defects due to minute foreign substances tend to become clearer. Further, as the film becomes thicker, the content of foreign matters per unit area of the film tends to be larger than that of a thin film, and this problem is further increased.

  On the other hand, in order to increase the transparency of the film, if the base film does not contain particles, or if it is contained only in a small amount so as not to impair the transparency, the slipperiness of the film becomes insufficient and the handling properties deteriorate. . Therefore, it is necessary to add particles for the purpose of imparting slipperiness to the easy-adhesion layer, and these particles need to use particles having an extremely small average particle diameter equal to or smaller than the wavelength of visible light in order to ensure transparency. is there. However, these fine particles tend to be coarse aggregates, and if an easy-adhesion layer containing the coarse aggregates is laminated on the base film, optical defects are caused.

On the surface of the base film, the height of the convex part is 1 μm or more and the maximum diameter is 20 μm or more, and the depth of the concave part within 100 μm from the position adjacent to the convex part is 0.5 μm or more. The number of foreign matters is preferably 10 pieces / m ² or less, and more preferably 5 pieces / m ² or less.

  Next, PET pellets alone for the outermost layer, master batches containing optical brightener and UV absorber for the intermediate layer, and PET pellets are mixed and dried at a predetermined ratio, and then a known melt laminating extruder. , Extruded from a slit-shaped die into a sheet, and cooled and solidified on a casting roll to produce an unstretched film. That is, using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having a square merging portion), a film layer constituting both outer layers and a film layer constituting an intermediate layer are laminated, An unstretched film is formed by extruding a three-layer sheet from the die and cooling with a casting roll. About the lamination | stacking ratio in this case, 3-15% is preferable and, as for the ratio with respect to the total thickness of the outermost layer (one side), 5-10% is more preferable. When the ratio of the outermost layer (one side) is lower than 3%, bleeding out of the organic fluorescent whitening agent and the ultraviolet absorber contained in the intermediate layer cannot be sufficiently prevented. Conversely, if it is higher than 15%, the UV absorption effect of the intermediate layer may be insufficient, which is not preferable. For the purpose of preventing UV degradation of the outermost layer, a known polymer type UV absorber having no bleeding problem may be added to the outermost layer.

  The obtained unstretched film is stretched 2.5 to 5.0 times in the longitudinal direction (longitudinal direction: travel direction during production of the laminated film) with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented film. In addition, the process of performing this uniaxial stretching may be called "longitudinal stretching process".

Scratches having a depth of 1 μm or more and a length of 3 mm or more present on the surface of the laminated film are 100 pieces / m ² or less. Preferably, the number of scratches is 30 pieces / m ² or less, more preferably 10 pieces / m ² or less. If the number of scratches is within such a range, problems due to optical defects do not occur.

  In this case, in order to prevent the generation of scratches on the film, (a) the film surface itself or the roll surface, in particular, the roll surface in contact with the film should not generate “defects” that cause scratches, and (b) contact. It is important that the film does not shift in the machine and transverse directions on the surface of the roll to be rolled.

  The above-mentioned “defects” refer to all factors that cause fine scratches on the film by coming into contact with the film, such as scratches, deposits, deposits, and foreign matters formed on the roll surface. Therefore, by eliminating these defects, it is possible to reduce the occurrence of scratches on the film surface. In order to prevent the occurrence of the above defects, for example, the following methods can be employed.

  In order to prevent the surface roughness of the roll used in the production of the laminated film from 0.1 μm or less by Ra, or to prevent the generation of scratches such as deposits, deposits, and foreign matters on the roll surface, a longitudinal stretching process (hereinafter referred to as a roll stretching process) , "MD process") and a method of installing a roll cleaner at the preheating inlet and the cooling roll.

  In addition, there is a method in which the degree of cleanliness in the laminated film manufacturing process is class 1000 or less (1000 particles or less of 0.5 μm or more in a volume per cubic foot). It is preferable to use clean air of class 100 or less also for the blower cooling device for cooling the anti-roll surface.

  Further, there is a method of cleaning the roll by an operation of scraping a defect on the roll using an abrasive before manufacturing the laminated film. In addition, in order to prevent the film from adsorbing dust or the like due to the generation of static electricity and causing a defect, there is a method of providing a static eliminator so that the charge amount of the film becomes ± 1500 V or less in all steps. The process from the casting of the base film to the tenter described later is a process in which scratches are mainly likely to occur, and laying out this section in a compact manner and reducing the passage time to 5 minutes or less can also contribute to the suppression of the occurrence of defects. .

About a roll, it can be set as the structure where the fault of a roll surface does not contact a film directly by means, such as forming a water film on the roll surface, or using an air floating type roll.
Here, by setting the amount of oligomer deposited from the film to 1000 ppm or less, adhesion of defects on the roll surface can be reduced, and defects on the roll surface can be reduced.
Further, in the winding process after stretching described later, the surface of the end side in the width direction of the film (lateral direction: direction perpendicular to the running direction at the time of manufacturing the laminated film) is pressed with a roller with a protrusion, and the part And forming the projection on the roller with the projection into a tapered shape, and forming the projection on the roller with the projection. By rounding the top and setting the curvature radius of the top surface to 0.4 mm or less, it is possible to prevent the film and the defect from contacting each other in the film winding apparatus.

As a method for suppressing film displacement on the roll surface and scratches on the film during film formation, for example, the following methods can be employed.
Applying means such as roll diameter reduction, suction roll use, electrostatic contact, and part nip contact device to increase the adhesion of the film to the roll, thereby suppressing the occurrence of long scratches. it can. In particular, reducing the diameter of the roll also subdivides the amount of shift of the film and can contribute to the prevention of long scratches. In addition, many of the scratches increase in length and frequency toward the end in the roll width direction, and it is difficult to obtain a scratch-free portion at the end in the roll width direction. By trimming around the center of the direction, a film with few scratches can be obtained.

  As a cause of occurrence of longitudinal scratches or lateral scratches, deformations such as expansion and contraction in the longitudinal direction or the lateral direction of the film can be mentioned, respectively. These film deformations are mainly caused by temperature changes in the film. Therefore, for example, by suppressing the temperature change of the film on the roll surface, the amount of film deformation due to such temperature can be reduced, and the occurrence of vertical scratches and horizontal scratches can be prevented. Specifically, the temperature change of the film per roll is 40 ° C. or less, preferably 30 ° C. or less, more preferably 20 ° C. or less, further preferably 10 ° C. or less, and particularly preferably 5 ° C. or less. Recommended.

  Examples of the method for suppressing the temperature change of the film on the roll surface include air cooling between the rolls and water cooling through a water tank. Furthermore, the temperature change of the film on the roll surface per roll can be reduced by increasing the number of rolls. Preferably, the number of rolls in the MD process is 10 or more.

  Further, by setting the relationship between the relative speeds of the plurality of rolls to a speed profile that is closest to the amount of deformation due to the temperature and tension of the film, it is possible to reduce the vertical shift of the film.

  Furthermore, in the coating step of the coating liquid for forming the adhesive property-modified resin layer, which will be described later, the film temperature at the dryer outlet is 40 ° C. or lower by completing the drying at the initial stage of the dryer section and cooling to the outlet. As a result, the shift of the film due to temperature change can be reduced.

  If the tension during running of the film is too low, the gripping force will be reduced and deviation will occur, and if it is too high, stress deformation will increase and deviation will occur, so the optimum tension range will be 4.9-29.4 MPa. It is preferable to adjust by the driving roll speed and tension adjusting means. Moreover, the shift | offset | difference of the film on a roll surface can be suppressed by making the friction coefficient between the film and roll in the use temperature at the time of manufacture 0.2 or more.

  In the film after uniaxial stretching, stress is applied in the longitudinal direction in order to convey the film, and further, deformation stress commensurate with the Poisson's ratio and the elastic modulus is generated in the orthogonal direction. In order to reduce this stress and to reduce the heat shrinkage stress of the film, it is preferable to lower the orientation within a range that does not adversely affect the physical properties of the film. Specifically, the value of the refractive index difference in the X-axis direction [(refractive index in the X-axis direction of uniaxially stretched film) − (refractive index in the X-axis direction of unstretched film)] is 0.01 to 0.12. It is recommended to be a low-oriented uniaxially stretched film.

When the ultraviolet absorbing film of the present invention is applied to an appropriate other film or a hard substrate, such as when the ultraviolet absorbing film of the present invention is applied to a filter for a plasma display panel, etc. In an arbitrary later stage, an easy-adhesion layer may be formed and laminated on at least one surface of the polyester film by a coating method in order to obtain sufficient adhesion to the infrared absorption layer and the hard coat layer.
Hereinafter, the easily bonding layer on the ultraviolet-absorbing film provided arbitrarily is demonstrated in detail.
The easy-adhesion layer can be applied by any known method. Examples include reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method and curtain coating method. These methods can be performed alone or in combination.

Although the process of apply | coating an easily bonding layer coating liquid may be a normal application process, ie, the process of apply | coating to the base film which carried out biaxial stretching and heat-setting, it is preferable to apply during the manufacturing process of this film. More preferably, it is applied to the base film before crystal orientation is completed. The solid content concentration in the aqueous solution is usually 30% by weight or less, preferably 10% by weight or less. The aqueous coating solution is applied so that 0.01 to 5 g, preferably 0.2 to 4 g, is attached per 1 m ² of the running film. The film coated with the aqueous coating solution is guided to a tenter for stretching and heat setting, and heated there to form a stable film by a thermal crosslinking reaction, and becomes a polyester-based film. In order to obtain sufficient adhesion to the infrared absorption layer and the hard coat layer, the coating amount at this time is 0.01 g / m ² or more per 1 m ^{2 of} film, and heat treatment at 100 ° C./1 minute or more is preferable. . The degree of cleanliness when applying the coating solution is preferably class 1000 or less in order to reduce adhesion of dust.

  Examples of the resin constituting the easy-adhesion layer include copolymer polyester resins, polyurethane resins, acrylic resins, styrene-maleic acid graft polyester resins, acrylic graft polyester resins, and the like, and use at least one or more. Is preferred. Among these, a resin composed of a copolyester resin and a polyurethane resin, and a styrene-maleic acid graft polyester resin are particularly preferable because of excellent adhesiveness.

Regarding the adjustment of the coating solution used for forming the easy-adhesion layer, an example of a coating solution composed of a copolyester resin and a polyurethane resin will be described below.
The copolymerized polyester resin used in the easy-adhesion layer of the present invention has a branched glycol component as a constituent component. Examples of the branched glycol component include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol. Etc. These branched glycol components are preferably contained in the total glycol component in a proportion of 10 mol% or more, more preferably 20 mol% or more. As the glycol component other than the above compounds, ethylene glycol is most preferable.

  As the dicarboxylic acid component contained as a constituent component in the copolyester resin, terephthalic acid and isophthalic acid are most preferable.

  In addition to the dicarboxylic acid component, sodium 5-sulfoisophthalate is preferably used in the range of 1 to 10 mol% in order to impart water dispersibility, and others include sulfoterephthalic acid and 4-sulfonaphthalene isophthalate. Examples include acid-2,7-dicarboxylic acid and 5- (4-sulfophenoxy) isophthalic acid and salts thereof.

  The polyurethane resin used in the easy-adhesion layer of the present invention is, for example, a resin containing a block type isocyanate group, and a thermally reactive water-soluble urethane in which a terminal isocyanate group is blocked with a hydrophilic group (hereinafter referred to as a block), etc. Is mentioned. Examples of the isocyanate group blocking agent include bisulfites and sulfonic acid group-containing phenols, alcohols, lactam oximes and active methylene compounds. The blocked isocyanate group makes the urethane prepolymer hydrophilic or water-soluble. When thermal energy is applied to the resin during drying or heat setting during film production, the blocking agent is released from the isocyanate group, so the resin is fixed with a water-dispersible copolyester resin mixed in a self-crosslinked stitch. At the same time, it reacts with the terminal groups of the resin. The resin under preparation of the coating solution is hydrophilic and has poor water resistance, but when the thermal reaction is completed by coating, drying and heat setting, the hydrophilic group of the urethane resin, that is, the blocking agent is released, so the water resistance is good. A coating film is obtained.

  The chemical composition of the urethane prepolymer used in the above resin is (1) an organic polyisocyanate having two or more active hydrogen atoms in the molecule, or a molecular weight having at least two active hydrogen atoms in the molecule. 200 to 20000 compounds, (2) an organic polyisocyanate having two or more isocyanate groups in the molecule, or (3) a terminal obtained by reacting a chain extender having at least two active hydrogen atoms in the molecule It is a compound having an isocyanate group.

  The compound (1) generally known is a compound containing two or more hydroxyl groups, carboxyl groups, amino groups or mercapto groups in the terminal or molecule, and particularly preferred compounds include polyether polyols. And polyether ester polyols.

  Examples of polyether polyols are compounds obtained by polymerizing alkylene oxides such as ethylene oxide and propylene oxide, styrene oxide and epichlorohydrin, or the like, or random polymerization, block polymerization, or addition polymerization to a polyhydric alcohol. There are compounds. Examples of the polyester polyol and the polyether ester polyol mainly include linear or branched compounds. Polyvalent saturated or unsaturated carboxylic acids such as succinic acid, adipic acid, phthalic acid and maleic anhydride, or the carboxylic acid anhydride, and the like, ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and tri It can be obtained by condensing polyvalent saturated and unsaturated alcohols such as methylolpropane, polyalkylene ether glycols such as relatively low molecular weight polyethylene glycol and polypropylene glycol, or a mixture of these alcohols.

  Examples of the organic polyisocyanate (2) include isomers of toluylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4. -Alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, or a single or a plurality of these compounds with trimethylolpropane and the like in advance. Examples include added polyisocyanates.

  Examples of the chain extender having at least two active hydrogens in (3) above include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6-hexanediol, glycerin, trimethylolpropane, and Examples include polyhydric alcohols such as pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine, and piperazine, amino alcohols such as monoethanolamine and diethanolamine, thiodiglycols such as thiodiethylene glycol, and water. In order to synthesize the urethane polymer of the above (3), it is usually several minutes to several hours at a temperature of 150 ° C. or less, preferably 70 to 120 ° C., by a single-stage or multi-stage isocyanate polyaddition method using the chain extender. React. The ratio of isocyanate groups to active hydrogen atoms can be freely selected as long as it is 1 or more, but it is necessary that free isocyanate groups remain in the obtained urethane prepolymer. The content of free isocyanate groups may be 10% by weight or less, but in view of the stability of the urethane polymer aqueous solution after being blocked, it is preferably 7% by weight or less.

The urethane prepolymer obtained is preferably blocked using bisulfite. Mix with aqueous bisulfite solution and allow reaction to proceed with good agitation for about 5 minutes to 1 hour. The reaction temperature is preferably 60 ° C. or lower. Thereafter, it is diluted with water to an appropriate concentration to obtain a heat-reactive water-soluble urethane composition. When the composition is used, it is prepared to have an appropriate concentration and viscosity. However, when heated to about 80 to 200 ° C., the bisulfite of the blocking agent is dissociated and the active isocyanate group is regenerated, so that the prepolymer A polyurethane polymer is formed by a polyaddition reaction that occurs within or between the molecules of the polymer, and has a property of adding to other functional groups.
As an example of the resin (B) containing a block-type isocyanate group described above, a trade name Elastron manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. is typically exemplified.

  When the coating liquid is prepared by mixing the copolymerized polyester resin (A) containing a branched glycol component and the resin (B) containing a block type isocyanate group used in the present invention, the resin (A) and the resin The weight ratio of (B) is preferably (A) :( B) = 90: 10 to 10:90, more preferably (A) :( B) = 80: 20 to 20:80. If the ratio of the said resin (A) with respect to solid content weight is less than 10%, the applicability | paintability to a base film is unsuitable, and the adhesiveness between a surface layer and this film will become inadequate.

  In order to promote the thermal crosslinking reaction, a catalyst may be added to the aqueous coating solution used in the present invention, such as various inorganic substances, salts, organic substances, alkaline substances, acidic substances and metal-containing organic compounds. These chemicals are used. Moreover, in order to adjust pH of aqueous solution, you may add an alkaline substance or an acidic substance.

  When applying the aqueous coating solution to the surface of the substrate film, select from known anionic surfactants and nonionic surfactants in order to increase the wettability to the film and coat the coating solution uniformly. A necessary amount of a surfactant can be added and used.

  The solution viscosity of the coating solution is preferably 1.0 PaS (Pascal Sec) or less. Above this, streaky coating thickness spots are likely to occur.

  In the present invention, since a lubricant intended to impart easy lubricity is not added to the base film, it is preferable to add particles to the aqueous coating solution to form appropriate protrusions on the film surface. Examples of such particles include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide and other inorganic particles, crosslinked polymer particles, oxalic acid There may be mentioned organic particles such as calcium. Of these, silica is most preferable because it has a relatively close refractive index to that of the polyester resin and can easily provide high transparency.

  The average particle diameter of the particles added to the aqueous coating solution is usually 1.0 μm or less, preferably 0.5 μm or less, more preferably 0.1 μm or less. When the average particle diameter exceeds 1.0 μm, the film surface becomes rough and the transparency of the film tends to be lowered. The particle content contained in the coating solution is usually added so that the particle content of the coated film after coating and drying is 60% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less. To do. If the particle content of the coating film exceeds 60% by weight, the easy adhesion of the film may be impaired. Two or more kinds of the above particles may be blended in the film, or the same kind of particles having different particle diameters may be blended. In any case, it is preferable that the average particle diameter of the whole particle and the total content satisfy the above-mentioned range. When applying the coating liquid, in order to remove coarse aggregates of particles in the coating liquid, it is necessary to arrange a filter medium so that the coating liquid is precisely filtered immediately before the application.

The filter medium for microfiltration of the coating solution used in the present invention is required to have a filtration particle size of 225 μm or less (initial filtration efficiency 95%). The type of filter medium for microfiltration of the coating solution is not particularly limited as long as it has the above performance, and examples thereof include a filament type, a felt type, and a mesh type.
The material of the filter medium for finely filtering the coating solution has the above-described performance and is not particularly limited as long as it does not adversely affect the coating solution. Examples thereof include stainless steel, polyethylene, polypropylene, and nylon.

  Various additives such as an antistatic agent, a pigment, an organic filler, and a lubricant may be mixed in the composition of the aqueous coating solution as long as the effect is not lost. Furthermore, since the coating solution is aqueous, other water-soluble resins, water-dispersible resins, emulsions, and the like may be added to the coating solution in order to improve performance as long as the contribution effect is not lost.

  As described above, the ultraviolet absorbing film of the present invention is excellent in ultraviolet absorbing ability and excellent in light transmittance in the visible light region, so that undesired film coloring is suppressed, and various uses such as building materials and Although it can be suitably used for windowing films, packaging material films, etc. in the automotive field, the effect is remarkable when applied to a filter for a plasma display panel in consideration of this light transmittance.

Next, the panel filter of the present invention using this ultraviolet absorbing film will be described.
<Filter for panel>
The panel filter according to the present invention is disposed on the surface of a plasma display, and at least one surface of a base film is a display for the purpose of preventing malfunction in remote control and transmission optical communication due to near infrared rays emitted from the plasma display panel. A near-infrared cut layer (near-infrared absorption layer) installed on the front surface, and an electromagnetic wave cut layer that similarly absorbs electromagnetic waves radiated from the plasma display panel, and if necessary, fluorescent lamps on the display surface A combination of a plurality of layers having functions such as an antireflection layer for preventing the reflection of external light, such as a glare prevention layer, and the like. The panel filter of the present invention is characterized by using the above-described ultraviolet absorbing film of the present invention for the purpose of suppressing deterioration of the infrared absorbing dye with time in the near infrared cut layer.
Hereinafter, the infrared absorption layer which is an essential functional layer constituting the panel filter of the present invention will be described.

(Infrared absorbing layer: near infrared cut layer)
The infrared absorption layer provided in the panel filter of the present invention is not particularly limited as long as it has a performance capable of sufficiently absorbing the near infrared region emitted from a plasma display or the like. And a layer containing an infrared absorbing dye described in JP-A No. 71942 and JP-A No. 2002-226827.

  In the production of the near-infrared absorbing filter, the method for laminating the near-infrared absorbing layer on the base material is not particularly limited, but the coating method is preferable in terms of thickness uniformity and cost.

  In the case of the coating method, coating is performed by dissolving these in a solvent capable of dissolving the near-infrared absorbing compound and the polymer resin. Examples of the solvent at this time include acetone, ethyl methyl ketone, isobutyl methyl ketone, ethyl acetate, propyl acetate, methanol, ethanol, isopropyl alcohol, ethyl cellosolve, butyl cellosolve, benzene, toluene, xylene, tetrahydrofuran, n-hexane, Examples thereof include n-heptane, methylene chloride, chloroform, N, N-dimethylformamide, water and the like, and one or two or more thereof may be used together, but are not limited thereto.

  The coating method will be described in detail. A gravure coating method and a reverse coating method in which a polymer resin and at least one near-infrared absorbing compound are added and dissolved in the above-mentioned solvent, and this can be coated on a substrate at a high speed, for example. , Kiss roll coating method, roll coating method and the like can be applied, and the method is excellent in workability and productivity. The near-infrared absorbing compound in the near-infrared absorbing layer is preferably in a state dissolved in a polymer resin.

  The near-infrared absorbing filter having a configuration in which a near-infrared absorbing layer is laminated only on one surface of the ultraviolet-absorbing film substrate for plasma display of the present invention is, for example, a first near-infrared absorbing layer by the above-described method on a substrate. Then, a near-infrared absorbing layer of the second and subsequent layers can be further provided by a coating method or the like. The solvent, binder and method used to form the first and second and subsequent near-infrared absorbing layers may be the same or different. When providing the near-infrared absorption layer after the 2nd layer by a coating method, in order to avoid mixing of a layer, it is preferable to provide the 1st near-infrared absorption layer after drying.

  The near infrared absorbing layer may further contain various conventional additives. Examples of the additive include an antistatic agent, a stabilizer, and the like, but from the viewpoint of transparency, it is preferable that the additive does not substantially contain inert particles for the purpose of imparting slipperiness.

  The ultraviolet absorbing film of the present invention and a filter for a panel using the same, more specifically, a filter for a plasma display panel can be used for applications that block unnecessary near-infrared rays radiated from a display and has no yellow fruit. High transparency and excellent durability.

The following is an example of an ultraviolet absorbing film suitable for a plasma display of the present invention and a filter for a plasma display panel using the same, and a case where polyethylene terephthalate (abbreviated as PET) is used as a base material for the manufacturing method. Of course, the present invention is not limited to these.
“Parts” in Examples and Comparative Examples means “parts by weight” unless otherwise specified.

(Evaluation methods)
Values measured by the following criteria are used for the light transmittance and adhesiveness in the present invention.
(1) Light transmittance, UV cut property The transmittance was measured for each predetermined wavelength by using a spectrophotometer UV3100PC manufactured by Shimadzu Corporation and selecting the wavelength of the exposure light source.

(2) Adhesiveness between adhesive layer and hard coat layer Adhesiveness (adH1, adH2) when a photocurable acrylic hard coat layer was provided on the adhesive layer was measured as follows.
A hard coat agent (Seika Beam EXF01 (B)) manufactured by Dainichi Seika Co., Ltd. was applied to the surface of the easy-adhesion layer of the UV-absorbing polyester film for plasma display obtained in Examples and Comparative Examples using a # 8 wire bar. After drying for a minute and removing the solvent, the mixture was cured with a high-pressure mercury lamp at 80 W / cm, irradiation distance of 15 cm, and 5 m / min to form a 2 μm hard coat layer.
Adhesiveness was calculated | required with the test method according to 8.5.1 description of JIS-K5400 (adH1). Specifically, 100 grid-like cuts that penetrate the easy-adhesion layer and reach the base film are attached using a cutter guide with a gap interval of 2 mm, and cellophane adhesive tape (Nichiban 405 No. 24 mm width) is applied. The film was attached to the cut surface and rubbed with an eraser to completely adhere it, and then peeled off vertically to determine the adhesiveness from the following formula.
adH (%) = (1-peeling area / evaluation area) × 100
Moreover, after irradiating the film which formed the obtained hard-coat layer for 500 hours using the sunshine weather meter from the hard-coat surface side, adhesiveness was tested with the test method according to 8.5.1 description of JIS-K5400. Determined (adH2).

(3) Adhesiveness when a near-infrared absorbing layer is provided on the easy-adhesion layer (adNIR)
The coating liquid shown in Table 1 below was coated on one surface of the easy-adhesion layer of the UV-absorbing polyester film for plasma display obtained in Examples and Comparative Examples with a gravure roll, and hot air at 150 ° C. was applied to the film surface at a wind speed of 5 m / Drying for 1 minute while feeding in seconds. The thickness of the coating layer (near infrared absorption layer) after drying was 8.0 μm.
Adhesiveness between the adjacent easy-adhesion layer and the near-infrared absorbing layer was determined by a test method according to the description in 8.5.1 of JIS-K5400.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to carry out and they are all included in the technical scope of the present invention.

[Example 1]
(1) Production of master batch (A) 5 parts by weight of dried Adekastab LA-31 [trade name, manufactured by Asahi Denka Co., Ltd .: UV absorber], 10 parts by weight of exemplified compound (17) [fluorescent brightener], particles 85 parts by weight of PET resin (ME-553, manufactured by Toyobo Co., Ltd.) not containing bismuth was mixed, and a master batch was prepared using a kneading extruder. The extrusion temperature at this time was 285 ° C., and the extrusion time was 7 minutes.

(Adjustment of the coating liquid (A) for forming the easy adhesion layer)
A coating solution A for forming an easy-adhesion layer was prepared according to the following method. A reaction vessel was charged with 95 parts of dimethyl terephthalate, 95 parts of dimethyl isophthalate, 35 parts of ethylene glycol, 145 parts of neopentyl glycol, 0.1 part of zinc acetate and 0.1 part of antimony trioxide, and the ester was added at 180 ° C for 3 hours. An exchange reaction was performed. Next, 6.0 parts of 5-sodium isophthalic acid was added and an esterification reaction was performed over 240 ° C./1 hour, followed by a polycondensation reaction to obtain a polyester resin.

  6.7 parts of a 30% aqueous dispersion of the obtained polyester resin, 20% aqueous solution of a self-crosslinking polyurethane resin containing an isocyanate group blocked with sodium bisulfite (Daiichi Kogyo Seiyaku: trade name Elastron H-3) ), 0.5 parts of elastolone catalyst (Cat 64), 47.8 parts of water and 5 parts of isopropyl alcohol, 1% by weight of anionic surfactant, lubricant (Nissan Chemical Co., Ltd.) 5% by weight of Snowtex OL) was added to make coating solution A.

(2) Formation of UV-absorbing polyester film for plasma display 90 parts by weight of a pellet (ME-553 manufactured by Toyobo Co., Ltd.) containing no PET resin particles having an intrinsic viscosity of 0.62 dl / g as an intermediate layer raw material and a master batch (A) 10 parts was dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and then supplied to the extruder 2 (for the intermediate layer B layer). PET pellets (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles were dried at 135 ° C. under reduced pressure (1 Torr) for 6 hours, and then supplied to the extruder 1 (for outer layer A layer and outer layer C layer), respectively. The resin temperature up to the melting part, kneading part, polymer pipe, gear pump, and filter was 280 ° C., and the polymer pipe after that was 275 ° C., laminated in a three-layer confluence block, and extruded into a sheet form from the die. Each of these polymers was filtered using a stainless steel sintered filter medium (nominal filtration accuracy: 10 μm particles, 95% cut). Further, the resin temperature of the flat die was set to 275 ° C.
The extruded resin was wound around a casting drum (roll diameter: 400φ, Ra: 0.1 μm or less) having a surface temperature of 30 ° C. using an electrostatic application casting method, and solidified by cooling to produce an unstretched film. The discharge rate at this time was 48 kg / hr, and the obtained unstretched sheet had a width of 300 mm and a thickness of 1400 μm.

Moreover, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the outermost layer (A layer and C layer) was 10% with respect to the total thickness.
Next, the cast film is heated to 100 ° C. using a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction (running direction) with a roll group having a difference in peripheral speed, and a uniaxially oriented film Got.

  In addition, regarding all the rolls used at the time of film manufacture, the surface roughness of the roll was controlled to 0.1 μm or less by Ra, and roll cleaners were installed at the preheating inlet and the cooling roll in the longitudinal stretching step. The roll diameter in the longitudinal stretching step was 150 mm, and the film was brought into close contact with the roll using a suction roll, electrostatic contact, and part nip contact apparatus.

Thereafter, the coating liquid A for forming an easy-adhesion layer was microfiltered with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency of 95%) of 25 μm, applied to both sides by a reverse roll method, and dried. After coating, the end of the film is gripped with a clip, guided to a hot air zone heated to 130 ° C., dried, stretched 4.0 times in the width direction, and heat treated at 230 ° C. for 5 seconds. Among them, a relaxation treatment of 3% in the width direction was performed as necessary to obtain an ultraviolet-absorbing polyester film for plasma display. The film thickness at this time was 100 μm, and the coating amount of the easy adhesion layer at this time was 0.01 g / m ² .

[Example 2]
According to the method described in the production of the masterbatch (A) of Example 1, 5 parts by weight of dried Adekastab LA-31 (trade name), 5 parts by weight of exemplified compound (3) [fluorescent brightener], and exemplified compound (13) [Fluorescent whitening agent] 5 parts by weight and 85 parts by weight of PET resin (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles were mixed, and the same operation was performed to obtain a master batch (B). . In the following, an ultraviolet absorbing polyester film for plasma display was obtained in the same manner.

Example 3
According to the method described in the production of the master batch (A) of Example 1, 8 parts by weight of dried Adekastab LA-31 (trade name), 3 parts by weight of exemplified compound (3) [fluorescent brightener], and exemplified compound (16) [Fluorescent brightener] 4 parts by weight and 85 parts by weight of PET resin (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles were mixed, and the same operation was performed to obtain a master batch (C). . In the following, an ultraviolet absorbing polyester film for plasma display was obtained in the same manner.

Example 4
According to the method described in the production of the master batch (A) of Example 1, dried CYASORBUV-3638 [trade name, manufactured by Siatech, chemical name 2,2 ′-(1,4-phenylene) bis (4H— 3,1-benzoxazinon-4-one): ultraviolet absorber] 5 parts by weight, exemplary compound (3) [fluorescent brightener] 5 parts by weight, exemplary compound (17) [fluorescent brightener] 5 parts by weight Then, 85 parts by weight of PET resin (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles was mixed, and the same operation was carried out to obtain a master batch (D). In the following, an ultraviolet absorbing polyester film for plasma display was obtained in the same manner.

Example 5
According to the method described in the production of the master batch (A) of Example 1, dried CYASORBUV-3638 [trade name, manufactured by Siatech, chemical name 2,2 ′-(1,4-phenylene) bis (4H— 3,1-benzoxazinon-4-one): ultraviolet absorber] 8 parts by weight, exemplary compound (3) [fluorescent brightener] 7 parts by weight, PET resin not containing particles (ME-553 manufactured by Toyobo Co., Ltd.) ) 85 parts by weight were mixed, and the same operation was performed thereafter to obtain a master batch (E). In the following, an ultraviolet absorbing polyester film for plasma display was obtained in the same manner.

[Comparative Example 1]
According to the method described in the production of the master batch (A) of Example 1, dried CYASORBUV-3638 [trade name, manufactured by Siatech, chemical name 2,2 ′-(1,4-phenylene) bis (4H— 3,1-benzoxazinon-4-one): UV absorber] 10 parts by weight, 90 parts by weight of PET resin (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles were mixed, and the same operation was performed thereafter. A master batch (E) was obtained. In the following, an ultraviolet absorbing polyester film for plasma display was obtained in the same manner.

  For Examples 1 to 5 and Comparative Example 1, the light transmittance at wavelengths of 380 nm, 410 nm, and 430 nm, and the adhesion measurement results with the adjacent layer evaluated by the evaluation method are shown in Table 2 below.

  As is apparent from Table 2, the ultraviolet absorbing films of Examples 1 to 5 are all excellent in ultraviolet absorbing ability and visible light transmittance, and also have good adhesion to the adjacent easy-adhesion layer and hard coat layer. It can be seen that the filter is useful for plasma display panel filters. On the other hand, the ultraviolet absorbing film of Comparative Example 1 that does not use a fluorescent brightener in the film substrate is inferior in light blocking property at a wavelength of 410 nm, and when used for a filter for a plasma display panel, the infrared absorbing layer has poor protection. It is expected to be sufficient.

Claims (5)

  A film containing an optical brightener and an ultraviolet absorber, wherein the light transmittance at a wavelength of 410 nm is 30% or less, and the light transmittance at a wavelength of 430 nm is 70% or more. the film.   The ultraviolet absorbing film according to claim 1, wherein the film is a biaxially oriented polyester film, and has a light transmittance of 75% or more at a wavelength of 430 nm.   3. The ultraviolet absorber is at least one selected from the group consisting of benzotriazole compounds and cyclic imino ester compounds, and the biaxially oriented polyester film is substantially free of particles. The ultraviolet ray absorbing film described in 1. The ultraviolet light-absorbing film according to claim 2 or 3, wherein the fluorescent brightening agent contains a compound represented by the following general formula (I).

In general formula (I), R ¹ and R ⁴ represent a hydrogen atom, an alkyl group or an alkoxy group, and R ² and R ³ represent an alkyl group. [A] represents a substituted aryl group or a substituted ethenyl group.   A filter for a plasma display panel, wherein an infrared ray absorbing layer is provided on at least one side of the ultraviolet ray absorbing film according to any one of claims 2 to 4.