JP4433314B2 - Manufacturing method of near-infrared absorbing film - Google Patents

Description

  The present invention relates to a near-infrared absorbing film formed by laminating a near-infrared absorbing layer on one side of a transparent base film and an antistatic layer on the other side, and specifically has a wide and large absorption in the near-infrared region. In addition, the present invention relates to a near-infrared absorbing film with few micro defects that can cope with high definition of recent plasma displays.

An optical filter having a function of absorbing near infrared rays has a property of blocking near infrared rays and allowing visible light to pass therethrough, and is used in various applications.
In recent years, plasma displays, as well as liquid crystal displays, have been widely used for televisions as thin large screen displays. The plasma display has a problem that other electronic devices malfunction when using a remote control that uses near infrared rays due to the near infrared rays emitted from the inside. Therefore, a near-infrared absorption filter is provided on the front surface of the plasma display.

As a near-infrared absorption filter, (1) a filter containing metal ions such as copper or iron on phosphoric acid glass, and (2) a layer having a different refractive index is laminated, and a specific wavelength is set by causing interference with transmitted light. A transparent interference filter, (3) an acrylic resin filter containing copper ions in the copolymer, and (4) a coating solution in which an infrared-absorbing dye is dispersed or dissolved in the resin is coated on a transparent substrate film and dried. A near-infrared absorbing filter in which a near-infrared absorbing layer is formed has been proposed.
Among these, the filter (4) has good workability and productivity, has a relatively large degree of freedom in optical design, and various methods have been proposed (for example, see Patent Documents 1 to 6).
JP 2002-82219 A JP 2002-214427 A JP 2002-303720 A JP 2002-333517 A JP 2003-82302 A Japanese Patent Laid-Open No. 2003-96040

  Plasma displays, on the other hand, are being developed to save power and improve luminous brightness, and to support high-definition full high-definition broadcasting with 1920 x 1080 pixels, which is one of the main features of digital terrestrial broadcasting. It has been.

  As the size of each cell that emits light becomes smaller with the full high-definition, a small defect that has not been a problem in the prior art has been pointed out as an appearance defect. In other words, some conventional near-infrared absorption filters have the ability to sufficiently block the near-infrared rays emitted from the display. A near-infrared absorption filter that sufficiently satisfies the appearance of the absorption layer has not been obtained.

In order to cope with the high image quality and high definition of the plasma display, the present inventors added a surfactant having a specific HLB to the coating liquid used for forming the near-infrared absorbing layer. A method for improving the leveling property at the time of drying and reducing minute defects has been proposed (see, for example, Patent Documents 7 and 8). However, in optical filters for plasma displays that require high definition and high image quality by full high-definition digital terrestrial broadcasting, it has been desired to further improve the appearance of the near-infrared absorbing layer.
JP 2005-92195 A Japanese Patent Laid-Open No. 2005-92196

  In addition, in order to increase the sales volume of plasma displays and reduce costs, processing to bond near-infrared absorbing films to other components (for example, antireflection films and electromagnetic wave absorbing films) has been implemented not only in Japan but also overseas. Accordingly, the storage stability of the roll body during transportation is becoming more important.

  An object of the present invention is to solve the above-described problems in the prior art, and absorbs light having a wavelength in the near-infrared region in a large and wide range, thereby increasing display brightness and full high-definition broadcasting in recent years. An object of the present invention is to provide a near-infrared absorbing film that can cope with high definition and high image quality due to the coating film appearance of the near-infrared absorbing layer and is highly excellent.

The configuration of the near-infrared absorbing film of the present invention that has solved the above-described problems is as follows.
1st invention is a near-infrared absorption film formed by laminating | stacking a near-infrared absorption layer on the single side | surface of a transparent base film, and an antistatic layer on the other side, Comprising: This near-infrared absorption film is charged with a near-infrared absorption layer and charging. The near-infrared absorbing layer is made up of a resin and a near-infrared-absorbing dye as constituents, and the near-infrared-absorbing dye is a constituent component. A method for producing a near-infrared absorbing film , comprising a diimmonium salt compound, wherein the antistatic layer contains a π-electron conjugated conductive polymer.

  A method of removing dust and foreign matters that are appearance defects by imparting antistatic properties is known. Antistatic agents include (1) cationic antistatic agents having a cation group such as a quaternary ammonium salt, pyridinium salt, and primary to tertiary amino groups, and (2) a sulfonate group, a nitrate ester base, and phosphoric acid. Anionic antistatic agent having an anionic group such as ester base, (3) Amphoteric antistatic agent such as amino acid and amino sulfate ester, (4) Nonionic antistatic agent such as amino alcohol, glycerin and polyethylene glycol Surfactant-type antistatic agents such as an agent, and (5) a polymer type of the above-described antistatic agent are generally known.

  On the other hand, diimmonium salt compounds are widely used as near-infrared absorbing filters for displays because they have the advantage of being able to absorb large and broadly light rays having wavelengths in the near-infrared region as near-infrared absorbing dyes. .

  In the first invention of the present application, when a long near-infrared absorbing film having a layer configuration of a near-infrared absorbing layer / transparent substrate film / antistatic layer is continuously wound in a roll around a cylindrical core, The near-infrared absorbing layer and the antistatic layer of the near-infrared absorbing film are wound in contact with each other.

  However, when the near-infrared absorbing film is wound into a roll and stored, the diimmonium salt compound contained in the near-infrared absorbing layer in contact with the antistatic layer is deteriorated depending on the type of the antistatic agent constituting the antistatic layer. The present inventors have noted that the stability over time is greatly deteriorated.

  Furthermore, as a result of studying by changing the type of antistatic agent, when using a compound having a cationic or anionic polar group as the antistatic agent, these compounds have a polar group in the antistatic layer. Has been found to cause deterioration of the diimmonium salt compound in the near-infrared absorbing layer and greatly deteriorate the stability over time of the light transmittance in the near-infrared absorbing region.

  Specifically, a π-electron conjugated conductive polymer is selected from a large number of antistatic agents and contained in the antistatic layer to prevent deterioration of the diimmonium salt compound in the near-infrared absorbing layer. In addition, the inventors have found a selective effect that good stability over time can be obtained. In addition, since the antistatic effect is maintained even when an antireflection film or an electromagnetic wave absorption film is bonded to the near-infrared absorbing film of the present invention via an adhesive, dust or dust adheres to the film. It also has the effect of reducing the above.

  When the near-infrared absorption filter of the present invention is installed on the front surface of the plasma display, like the conventional near-infrared absorption filter, it absorbs unnecessary near-infrared rays emitted from the display and prevents malfunction of other electronic devices. In addition, it has the advantage that the coating appearance is highly excellent and can greatly contribute to the improvement of image quality by full high-definition plasma display.

  The material of each layer which comprises the near-infrared absorption film of this invention, suitable embodiment, the manufacturing method of a near-infrared absorption film, etc. are demonstrated in detail.

(Transparent substrate film)
In the present invention, the transparent substrate film is not particularly limited, but preferably has a total light transmittance of 80% or more and a haze of 5% or less. When the substrate film is inferior in transparency, not only the brightness of the display is lowered but also the sharpness of the image becomes poor.

  As such a transparent substrate film, for example, polyester-based, acrylic-based, cellulose-based, polyethylene-based, polypropylene-based, polyolefin-based, polyvinyl chloride-based, polycarbonate, phenol-based, urethane-based plastic film or sheet, And those obtained by laminating any two or more of these. A polyester film having a good balance between heat resistance and flexibility is preferable, and a polyethylene terephthalate film is more preferable.

  A polyester film suitable as a transparent substrate film is an aromatic dicarboxylic acid or ester thereof such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid as a dicarboxylic acid component, and ethylene glycol, diethylene glycol, 1, 4 as a glycol component. -A polyester chip obtained by performing esterification reaction or transesterification reaction of butanediol, neopentyl glycol, etc., and then polycondensation reaction is dried, melted with an extruder, and extruded into a sheet form from a T-die. It is a film produced by stretching a stretched sheet in at least one axial direction, and then performing a heat setting treatment and a relaxation treatment.

  The film is particularly preferably a biaxially stretched film from the viewpoint of strength. Examples of the stretching method include a tubular stretching method, a simultaneous biaxial stretching method, a sequential biaxial stretching method, and the like, but a sequential biaxial stretching method is preferable in view of flatness, dimensional stability, thickness unevenness, and the like. The sequential biaxially stretched film is, for example, roll-stretched in the longitudinal direction at a glass transition temperature (Tg) to (Tg + 30 ° C.) of 2.0 to 5.0 times in the longitudinal direction and then preheated with a tenter 120 Stretch in the width direction 1.2 to 5.0 times at ~ 150 ° C. Furthermore, after biaxial stretching, it can be produced by performing heat setting treatment at a temperature of 220 ° C. or higher (melting point−10 ° C.) and then relaxing by 3 to 8% in the width direction. Further, in order to further improve the dimensional stability in the longitudinal direction of the film, a longitudinal relaxation treatment may be used in combination.

  In order to provide the film with handleability (for example, rollability after lamination), it is preferable to incorporate particles and form protrusions on the film surface. As particles to be included in the film, inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, alumina, etc., heat resistant polymer particles such as acrylic, PMMA, nylon, polystyrene, polyester, benzoguanamine / formalin condensate, etc. Is mentioned. From the viewpoint of transparency, the content of particles in the film is preferably small, for example, preferably 1 ppm or more and 1000 ppm or less. Furthermore, it is preferable to select particles having a refractive index close to that of the resin used from the viewpoint of transparency. Moreover, in order to provide various functions as needed, the film may contain a light-resistant agent (ultraviolet ray inhibitor), a pigment, an antistatic agent, and the like.

  In the present invention, when an antireflection layer is provided on the surface opposite to the surface on which the near infrared absorbing layer is laminated (surface on the antistatic layer side), the near infrared absorbing dye is likely to be deteriorated by ultraviolet rays incident from the outside. It is preferable to contain an ultraviolet absorber in the base film.

  UV absorbers are broadly classified into organic UV absorbers and inorganic UV absorbers. From the viewpoint of ensuring transparency, it is desirable to use organic UV absorbers (low molecular type and high molecular type). . Although it does not specifically limit as an organic type ultraviolet absorber (low molecular type), For example, a benzotriazole type, a benzophenone type, a cyclic imino ester type, etc., and these combination are mentioned. Among these, benzotriazole type and cyclic imino ester type are preferable from the viewpoint of durability. More preferably, it is desirable to use an ultraviolet absorber that can withstand the melt extrusion temperature at the time of producing an unstretched sheet of the substrate film and has excellent heat resistance with a decomposition temperature of 290 ° C. or higher.

  The content of the ultraviolet absorber is appropriately adjusted so that the transmittance at a wavelength of 380 nm or less is 10% or less so that the photodegradation of the near-infrared absorbing layer can be suppressed. Specifically, it is preferable to contain an ultraviolet absorber in the range of 0.1-4 mass% in a transparent base film, and 0.3-2 mass% is more preferable. If the content of the ultraviolet absorber is too small, the ultraviolet absorbing ability is decreased, and if it is too large, the film may turn yellow or the film-forming property of the film may be decreased.

  The transparent substrate film used in the present invention may be a single layer film or a composite film having two or more layers in which a surface layer and a center layer are laminated. In the case of a composite film, there is an advantage that the functions of the surface layer and the center layer can be designed independently. For example, the composite substrate film as a whole can be obtained by containing particles only in a thin surface layer and maintaining the handleability by forming irregularities on the surface, but not containing particles in the thick central layer. Transparency can be further improved.

  In addition, in the case of imparting an ultraviolet absorbing ability, by including an ultraviolet absorber only in the center layer, it is possible to reduce deposition of the ultraviolet absorber with the lapse of time on the surface of the film during film production. It is possible to suppress adverse effects such as deterioration of heat resistance to the absorption layer. The method for producing the composite substrate film is not particularly limited, but considering the productivity, the raw material for the surface layer and the central layer are extruded from different extruders and led to one die to obtain an unstretched sheet. Thereafter, lamination by a so-called coextrusion method in which the film is oriented in at least one axial direction is particularly preferable.

  The thickness of the transparent substrate film varies depending on the material, but when a polyester film is used, the lower limit is preferably 35 μm, more preferably 50 μm. On the other hand, the upper limit of the thickness is preferably 260 μm, more preferably 200 μm. When the thickness of the base film is thin, not only the handling properties become poor, but also when heated at the time of drying so as to reduce the residual solvent of the near-infrared absorbing layer, heat wrinkles are generated in the film, resulting in flatness. It tends to be defective. On the other hand, when the thickness of the base film is large, not only is there a problem in terms of cost, but flatness due to curling tends to occur when it is wound and stored in a roll shape.

(Middle layer)
The near-infrared absorbing film of the present invention has a structure in which a near-infrared absorbing layer is laminated on a transparent substrate film, but the adhesion between the transparent substrate film and the near-infrared absorbing layer is improved and the transparent substrate film is transparent. It is preferable to provide an intermediate layer for the purpose of improving the properties. In addition, when not containing particle | grains in a base film, high transparency can be obtained, maintaining handling property by providing the intermediate | middle layer containing particle | grains simultaneously at the time of manufacture of a base film.

  Examples of the resin constituting the intermediate layer include polyester resins, polyurethane resins, polyester urethane resins, acrylic resins, melamine resins, etc., so that the adhesion to the base film and the near infrared absorption layer is improved. It is important to select the resin. Specifically, if the resin constituting the base film and the near-infrared absorbing layer is an ester, it is preferable to select a polyester or polyester urethane having a similar structure.

  The intermediate layer may contain a cross-linking agent for the purpose of improving adhesion and water resistance to form a cross-linked structure in the resin. Examples of the crosslinking agent include urea, epoxy, melamine, and isocyanate. In particular, when the resin is whitened under high temperature and high humidity and the strength is lowered, the effect of the crosslinking agent is remarkable. In addition, you may use the graft copolymer resin which has self-crosslinking property as resin, without using a crosslinking agent.

  The intermediate layer may contain various kinds of particles for the purpose of forming irregularities on the surface and improving slipperiness. Examples of the particles to be included in the intermediate layer include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, and alumina, organic materials such as acrylic, PMMA, nylon, styrene, polyester, and benzoguanamine / formalin condensate. Particles. In addition, it is preferable to select particles having a refractive index close to that of the resin used from the viewpoint of transparency.

  Furthermore, in order to give various functions to the intermediate layer, a surfactant, an antistatic agent, a dye, an ultraviolet absorber, or the like may be contained.

  The intermediate layer may be a single layer if it has the desired function, but may be laminated in two or more layers as necessary.

  The thickness of the intermediate layer is not particularly limited as long as it has a desired function, but is preferably 0.01 μm or more and 5 μm or less. When the thickness is small, the function as the intermediate layer is hardly exhibited, and conversely, when the thickness is thick, the transparency tends to be poor.

  As a method for providing the intermediate layer, a coating method is preferable. As the coating method, using a known coating method such as gravure coating method, kiss coating method, dip method, spray coating method, curtain coating method, air knife coating method, blade coating method, reverse roll coating method, etc. It can be provided by an in-line coating method in which a coating layer is provided, or an offline coating method in which a coating layer is provided after film production. Of these methods, the in-line coating method is not only excellent in terms of cost, but by adding particles to the coating layer, it is not necessary to include particles in the transparent substrate film, so the transparency is highly improved. Is preferable.

(Antistatic layer)
In the present invention, an antistatic layer is provided on the opposite side of the near-infrared absorbing layer of the transparent substrate film. The antistatic layer may be provided directly on the base film, or may be provided via an intermediate layer that improves the adhesiveness between the transparent base film and the antistatic layer when the adhesiveness is poor. .

In the present invention, the surface resistance of the antistatic layer is preferably 1 × 10 ⁵ to 1 × 10 ¹² Ω / □. When the surface resistance is lower than 1 × 10 ¹² Ω / □, when a near-infrared absorbing layer is provided using a roll-to-roll method, charging (unwinding charging) when unwinding the film from the roll, film Charging (friction charging) due to friction between the metal roll and the rubber roll can be greatly reduced. Therefore, before applying the coating liquid for forming the near-infrared absorbing layer, it is possible not only to greatly reduce the adhesion of foreign substances etc., but also to apply organic solvent-based coating liquids, particularly coating liquids containing toluene. It is possible to reduce repelling due to charging during application. The lower the surface resistance of the antistatic layer, the more the amount of foreign matter can be reduced and the prevention of minute foreign matter can be prevented. However, lowering the surface resistance below 1 × 10 ⁵ Ω / □ has not only a cost problem but also a problem that the transparency of the film deteriorates.

  Furthermore, by laminating the antistatic layer, the surface of the transparent substrate film is smoothed and the transparency is improved. In particular, the haze can be reduced.

  The π-electron conjugated conductive polymer contained in the antistatic layer has aniline and / or a derivative thereof, pyrrole and / or a derivative thereof, isothianaphthene and / or a derivative thereof, acetylene and / or a derivative thereof. , Thiophene and / or its derivatives are preferred. Among these, thiophene and / or its derivatives are particularly preferable because of less coloring.

  In addition to the π electron conjugated conductive polymer, other resins may be mixed in the antistatic layer in order to improve adhesion. Examples of the resin to be mixed include polyester resins, polyurethane resins, polyester urethane resins, acrylic resins, melamine resins, and the like. Select a resin that has good adhesion to the base film and the near infrared absorption layer. is important. Specifically, acrylic and ester resins, which are resins having a structure similar to the resin constituting the base film and the near-infrared absorbing layer, are preferable.

  The antistatic layer may contain a surfactant for improving the appearance, an ultraviolet absorber, a dye or pigment for color tone adjustment, and various fillers for imparting slipperiness.

  The thickness of the antistatic layer is not particularly limited as long as the desired antistatic property is achieved, but is preferably 0.01 μm or more and 10 μm or less. When the thickness of the antistatic layer is less than 0.01 μm, the antistatic property becomes insufficient and the surface smoothness becomes insufficient. On the other hand, when the thickness of the antistatic layer is thicker than 10 μm, transparency tends to be poor.

  As a method for providing the antistatic layer, a coating method is preferable. As the coating method, using a known coating method such as gravure coating method, kiss coating method, dip method, spray coating method, curtain coating method, air knife coating method, blade coating method, reverse roll coating method, etc. It can be provided by an in-line coating method in which a coating layer is provided, or an offline coating method in which a coating layer is provided after film production. In the case where the antistatic layer also serves as an intermediate layer, the in-line coating method is not only excellent in terms of cost, but also by including particles in the coating layer, it is not necessary to include particles in the transparent substrate film. Can be highly improved.

Laminating the antistatic layer is provided prior to laminating the near infrared absorbing layer on a transparent substrate film. When the near-infrared absorbing layer is provided after the antistatic layer is provided, the adhesion of dust and dust to the near-infrared absorbing layer can be further reduced. In addition, when an antistatic layer is provided after providing a near-infrared absorbing layer, the effect of improving appearance defects due to adhesion of dust or the like when laminating the near-infrared absorbing layer is reduced, but an antireflection film, an electromagnetic wave absorbing film, etc. In the post-processing step of bonding the functional film, it is possible to reduce appearance defects due to adhesion of foreign matters such as dust.

(Near-infrared absorbing layer)
The near-infrared absorbing film of the present invention has a structure in which a near-infrared absorbing layer containing a near-infrared-absorbing dye is laminated on one side of a transparent substrate film and on the other side directly or through another layer. .

  The near-infrared absorbing dye is a dye having a maximum absorption in the near-infrared region having a wavelength of 800 to 1200 nm, and is a diimmonium salt-based, phthalocyanine-based, dithiol metal complex-based, naphthalocyanine-based, azo-based, polymethine-based, anthraquinone , Naphthoquinone, pyrylium, thiopyrylium, squarylium, croconium, tetradehycholine, triphenylmethane, cyanine, azo, aminium, and the like. These compounds are used alone or in admixture of two or more.

  In the present invention, a diimmonium salt compound having a large absorption in the near infrared region, a wide absorption region, and a high transmittance in the visible light region is used as the near infrared absorbing dye in the near infrared absorbing layer. As the diimmonium salt compound, those represented by the following general formula (1) are suitable.

Specific examples of R1 to R8 in the general formula (1) include (a) methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, ter-butyl. Group, n-amyl group, n-hexyl group, n-octyl group, 2-hydroxyethyl group, 2-cyanoethyl group, 3-hydroxypropyl group, 3-cyanopropyl group, methoxyethyl group, ethoxyethyl group, butoxyethyl (B) aryl groups such as phenyl group, fluorophenyl group, chlorophenyl group, tolyl group, diethylaminophenyl and naphthyl group, (c) alkenyl groups such as vinyl group, propenyl group, butenyl group and pentenyl group (D) benzyl group, p-fluorobenzyl group, p-chlorophenyl group, phenylpropyl group, naphthylethyl group, etc. Aralkyl group, and the like. Of these, branched iso-butyl groups, ter-butyl groups, and further phenylalkyl groups having a benzene ring are preferred because the durability of the dye itself is improved. It is necessary to select it in consideration of solubility.
R1 to R8 may all be the same or different.

  R9-12 may be hydrogen, fluorine, chlorine, bromine, diethylamino group, dimethylamino group, cyano group, nitro group, methyl group, ethyl group, propyl group, trifluoromethyl group, methoxy group, ethoxy group, propoxy Groups and the like.

X ⁻ is fluorine ion, chlorine ion, bromine ion, iodine ion, perchlorate ion, hexafluoroantimonate ion, hexafluorophosphate ion, tetrafluoroborate ion, trifluoromethanesulfonate ion, toluenesulfonate ion Bis (trifluoromethanesulfonyl) imidate ion, bis (pentafluoroethanesulfone) imidate ion, and the like, and from the viewpoint of durability and dye solubility, it is preferable to use an imido ion system. However, the present invention is not limited to the above examples. Some of these are available as commercial products, for example, Kayasorb IRG-022, IRG-023, IRG-024, IRG-068, Nippon Carlit Co., Ltd. CIR-1080, CIR-1081, CIR -1083, CIR-1085, CIR-1085F, CIR-RL and the like can be preferably used.

  The near-infrared absorbing film of the present invention may contain other near-infrared absorbing pigments in the near-infrared absorbing layer in addition to the diimmonium salt compound for the purpose of expanding and adjusting the absorption region in the near-infrared region. As a near-infrared absorbing dye that can be used in combination with a diimmonium salt compound, phthalocyanine, cyanine dye, dithiol metal has an absorption peak in the wavelength range of 800 to 1100 nm and does not promote deterioration of the diimmonium salt compound. Complexes are preferred.

In the present invention, in order to control the target absorption in the near infrared region and the transmittance in the visible light region, the amount of the near infrared absorbing dye per unit area is determined on an arbitrary surface in the thickness direction of the near infrared absorption layer. it is preferable to adjust to present at 0.01 g / m ² or more 1.0 g / m ² or less. When the amount of the near-infrared absorbing dye per unit area is small, the absorbing ability in the near-infrared region tends to be insufficient. On the other hand, when the amount of the near-infrared absorbing dye per unit area is large, there is a problem that the brightness in the display is lowered due to insufficient transparency in the visible light region.

  In the near-infrared absorbing layer of the present invention, the near-infrared-absorbing dye is laminated on one side of the transparent substrate film as a composition dispersed or dissolved in the resin, using a coating method.

  The resin constituting the near-infrared absorbing layer is not particularly limited as long as it can dissolve or disperse the near-infrared absorbing dye uniformly, but polyester-based, acrylic-based, polyamide-based, polyurethane-based, polyolefin-based, and polycarbonate-based resins may be used. Is preferred. Among these resins, an acrylic resin excellent in transparency, heat resistance, and solvent resistance at the time of pigment mixing is more preferable.

  The glass transition temperature of the resin constituting the near infrared absorption layer is preferably equal to or higher than the guaranteed use temperature of the equipment to be used. When the glass transition temperature of the resin is equal to or lower than the device operating temperature, the dyes dispersed in the resin are likely to react with each other, and the resin absorbs moisture in the outside air and deterioration of the dye and the binder resin increases.

  The glass transition temperature of the resin constituting the near-infrared absorbing layer is not particularly limited as long as it is equal to or higher than the device operating temperature, but is preferably 85 ° C. or higher and 160 ° C. or lower. When the glass transition temperature is lower than 85 ° C., interaction between the dye and the resin, interaction between the dyes, and the like occur, and the modification of the dye is likely to occur.

  On the other hand, when the glass transition temperature exceeds 160 ° C., it is necessary to increase the drying temperature in order to dissolve the resin in a solvent and perform sufficient drying when it is applied on a transparent substrate film. . As a result, the base film is wrinkled by heat, the flatness tends to be poor, and the deterioration of the pigment is also likely to occur. Moreover, when it dries at low temperature, drying time becomes long and productivity worsens, and productivity becomes bad. In addition, sufficient drying may not be possible, the solvent may remain in the coating film, the apparent glass transition temperature of the resin may decrease, and the dye may be modified.

  The near-infrared absorbing pigment content in the near-infrared absorbing layer is preferably 1% by mass or more and 10% by mass or less based on the resin. When the amount of the near-infrared absorbing pigment in the resin is small, it is necessary to increase the coating amount of the near-infrared absorbing layer in order to achieve the target near-infrared absorbing ability. Therefore, if sufficient drying is attempted, drying at a high temperature or for a long time is required, and deterioration of the pigment or poor flatness of the base film tends to occur. On the other hand, when the content of the near-infrared absorbing dye in the resin is large, the distance between the dyes becomes short and the interaction between the dyes becomes strong. Therefore, even if the residual solvent in the near-infrared absorbing layer is reduced, the dye is likely to be denatured over time.

  In the present invention, the near-infrared absorbing layer is preferably formed by applying and drying a coating liquid containing a near-infrared absorbing dye, a resin, and an organic solvent on one side of the transparent substrate film. At this time, it is more preferable to include a surfactant in the coating solution. By including a surfactant in the coating solution that forms the near-infrared absorbing layer, the coating appearance of the near-infrared absorbing layer, especially dents due to minute bubbles, dents due to adhesion of foreign matter, and repellency in the drying process are reduced. Is done. Furthermore, the surface active agent bleeds on the surface by coating and drying, so that slipperiness is imparted, and handling properties are improved without forming surface irregularities on the near-infrared absorbing layer or / and the opposite surface, and the surface is wound in a roll shape. Easy to take.

  As the surfactant, a known cationic, anionic, or nonionic surfactant can be suitably used, but a nonionic surfactant that does not have a polar group is preferred in view of problems such as deterioration with a near-infrared absorbing dye. A silicon-based or fluorine-based surfactant having excellent surface activity is preferable.

  Silicone surfactants include dimethyl silicon, amino silane, acrylic silane, vinyl benzyl silane, vinyl benzyl silyl amino silane, glycid silane, mercapto silane, dimethyl silane, polydimethyl siloxane, polyalkoxy siloxane, hydrodiene modified siloxane, vinyl modified siloxane, Vitroxy modified siloxane, amino modified siloxane, carboxyl modified siloxane, halogenated modified siloxane, epoxy modified siloxane, methacryloxy modified siloxane, mercapto modified siloxane, fluorine modified siloxane, alkyl group modified siloxane, phenyl modified siloxane, alkylene oxide modified siloxane, etc. .

  Fluorosurfactants include ethylene tetrafluoride, perfluoroalkyl ammonium salt, perfluoroalkyl sulfonic acid amide, sodium perfluoroalkyl sulfonate, perfluoroalkyl potassium salt, perfluoroalkyl carboxylate, perfluoroalkyl sulfone. Acid salts, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl trimethyl ammonium salts, perfluoroalkyl amino sulfonates, perfluoroalkyl phosphate esters, perfluoroalkyl alkyl compounds, perfluoroalkyl alkyl betaines, perfluoroalkyl halides, etc. Is mentioned.

  The content of the surfactant is preferably 0.01% by mass or more and 2.00% by mass or less with respect to the resin constituting the near infrared absorption layer. When the surfactant content is low, the effect of improving the coating appearance and imparting slipperiness tends to be insufficient. On the other hand, when there is much content of surfactant, a near-infrared absorption layer becomes easy to absorb a water | moisture content and it becomes easy to accelerate | stimulate deterioration of a pigment | dye.

  The HLB of the surfactant is more preferably 2 or more and 12 or less. The lower limit value of HLB is preferably 3, particularly preferably 4. On the other hand, the lower limit value of HLB is preferably 11, particularly preferably 10. When the HLB is low, the leveling property tends to be insufficient due to insufficient surface activity. On the other hand, when the HLB is high, not only the slipping property is insufficient, but also the near-infrared absorbing layer tends to absorb moisture, and the temporal stability of the dye tends to be poor.

  Note that HLB means W.A. of Atlas Powder, Inc. of the United States. C. Griffin is named as Hydrophile Balance, and the balance between the hydrophilic group and the lipophilic group contained in the surfactant molecule is indexed as a characteristic value. The lower the value, the more hydrophilic the higher the lipophilicity. It means that the nature is high.

  In the present invention, the near-infrared absorbing layer is laminated by applying and drying a coating liquid containing a resin, a near-infrared absorbing dye, and optionally a surfactant on a transparent substrate film. It is preferable to dilute with an organic solvent from the viewpoint of coatability.

  Examples of the organic solvent include (1) alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tridecyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl alcohol, (2) ethylene glycol, Glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, glycerin, (3) ethylene glycol monomethyl ether, ethylene glycol monoethylene ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Diethylene glycol butyl ether, ethylene glycol monomethyl -Glycol ethers such as ether acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, diethylene glycol monoethyl acetate, diethylene glycol monobutyl acetate, (4) esters such as ethyl acetate, isopropylene acetate and n-butyl acetate (5) ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, isophorone, diacetone alcohol, etc., and these may be used alone or in admixture of two or more. it can.

  Preferably, ketones having excellent dye solubility are contained in an amount of 30% by mass to 80% by mass with respect to the total organic solvent used in the coating solution, and other organic solvents are considered in view of leveling properties and drying properties. It is preferable to select. The boiling point of the organic solvent is preferably 60 ° C. or higher and 180 ° C. or lower. When the boiling point of the organic solvent is low, the solid content concentration of the coating solution changes during coating, and it is difficult to stabilize the coating thickness. On the other hand, when the boiling point of the organic solvent is high, the amount of the organic solvent remaining in the coating film increases, and the stability over time tends to be poor.

  Examples of the method for dissolving or dispersing the near-infrared absorbing dye and the resin in an organic solvent include a method of stirring, dispersing and pulverizing under heating. By heating, the solubility of the pigment and the resin can be improved, and a defect in the coating appearance due to undissolved substances or the like is prevented. Moreover, it is possible to form a near-infrared absorbing layer having excellent transparency by dispersing and pulverizing and dispersing the resin and the pigment in the coating liquid in a fine particle state of 0.3 μm or less. A well-known thing can be used as a disperser and a grinder. Dispersers and pulverizers include ball mills, sand mills, attritors, roll mills, agitators, colloid mills, ultrasonic homogenizers, homomixers, pearl mills, wet jet mills, paint shakers, butterfly mixers, planetary mixers, Henschel mixers, etc. It is done.

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

  It is preferable that solid content concentration, such as resin and a pigment | dye contained in a coating liquid, is 10 mass% or more and 30 mass% or less. When the solid content concentration is low, it takes time to dry after coating, and not only productivity is inferior, but also the amount of the solvent remaining in the coating film is increased, and stability with time tends to be poor. On the other hand, when the solid content concentration is high, the viscosity of the coating solution becomes high and the leveling property is insufficient, and the coating appearance tends to be poor. The viscosity of the coating solution is preferably 10 cps or more and 300 cps or less from the viewpoint of coating appearance, and the solid content concentration, the organic solvent, etc. are adjusted so as to be in this range.

  In the present invention, as a method for applying the near infrared absorption layer on the transparent substrate film, gravure coating method, kiss coating method, dip method, spray coating method, curtain coating method, air knife coating method, blade coating method, reverse roll coating Conventionally used methods such as a method, a bar coat method, and a lip coat method can be applied. Among these, a gravure coating method that can be applied uniformly, particularly a reverse gravure method is preferable. The diameter of the gravure is preferably 80 mm or less. When the diameter is large, the frequency of occurrence of ridges in the flow direction increases.

The coating amount of the near infrared absorbing layer after drying is not particularly limited, but the lower limit is preferably 1 g / m ² , more preferably 3 g / m ² . On the other hand, the upper limit of the coating amount is preferably 50 g / m ² , more preferably 30 g / m ² . When the coating amount after drying is small, the near infrared absorption ability tends to be insufficient. Therefore, increasing the abundance of the near-infrared absorbing pigment in the resin, when an intermediate layer is provided between the near-infrared absorbing layer and the base film, the surface of the near-infrared absorbing layer and the interface between the near-infrared absorbing layer and the intermediate layer The amount of pigment present increases, and it is easily affected by the outside air and the resin of the intermediate layer. As a result, the dye is likely to deteriorate and the stability with time may be poor. Conversely, when the coating amount after drying is large, the near-infrared absorbing ability is sufficient, but the transparency in the visible light region is lowered, and the brightness of the display is lowered. Therefore, if the amount of the near-infrared absorbing dye in the resin is reduced, the optical characteristics can be adjusted, but drying tends to be insufficient. As a result, the temporal stability of the dye may be poor due to the residual solvent in the coating film. On the other hand, when the drying is sufficient, the planarity of the base film may be poor.

As a method of applying the coating liquid on one side of the transparent substrate film and drying it, known hot air drying, infrared heaters and the like can be mentioned, but hot air drying with a high drying speed is preferable.
In the initial constant rate drying stage after coating, drying is preferably performed at 20 ° C. or more and 80 ° C. or less using hot air of 2 m / sec or more and 30 m / sec. When the initial drying is performed strongly (the hot air temperature is high and the hot air volume is large), minute defects of the coating such as fine coating removal from foam, fine repellency, and cracks tend to occur. Conversely, when the initial drying is weakened (the hot air temperature is low and the hot air volume is small), the appearance is good, but the drying time is long and there is a problem in terms of cost. When a surfactant is not added to the coating solution, the above minute defects are likely to occur, and the initial drying needs to be considerably weakened.

  In the reduction drying process, it is necessary to increase the temperature higher than the initial drying to reduce the solvent in the coating film, and the preferable temperature is 120 ° C. or higher and 180 ° C. or lower. Particularly preferably, the lower limit is 140 ° C and the upper limit is 170 ° C. When the drying temperature is low, the solvent in the coating film is difficult to decrease and becomes a residual solvent, and the stability of the dye over time tends to be insufficient. On the other hand, when the temperature is high, not only the flatness of the base film becomes poor due to heat wrinkles, but also the near-infrared absorbing dye may be deteriorated by heat. Moreover, it is preferable that the time of the film which passes a drying furnace is 5 second or more and 180 second or less. When the time is short, the amount of the solvent remaining in the coating film increases and the stability over time tends to be poor. On the other hand, when the time is long, not only the productivity becomes poor, but also the base film may have a flatness due to heat wrinkles. The upper limit of the time for the film passing through the drying furnace is particularly preferably 30 seconds from the viewpoint of productivity and flatness.

  In the final stage of drying, it is preferable that the hot air temperature is lower than the glass transition temperature of the resin, and the actual temperature of the base film is lower than the glass transition temperature of the resin in a flat state. When leaving the drying furnace at a high temperature, when the coated surface comes into contact with the roll surface, slippage is poor, and not only scratches but also curls may occur.

  In the case of a composite film in which an antireflection layer is laminated on the surface opposite to the side on which the near infrared absorption layer is laminated (surface on the antistatic layer side), a protective film that can be easily peeled off is provided on the antistatic layer side. It is preferable to laminate on the surface and apply and dry the near-infrared absorbing layer in that state. By using this method, when the near-infrared absorbing layer is laminated, not only the generation of scratches due to friction with the roll can be eliminated, but also the strength of the entire film is improved. Therefore, heat wrinkles of the base film during drying can be reduced, and haze deterioration due to precipitation of oligomers in the base film during drying can be prevented.

(Near-infrared absorbing film)
In the present invention, the near infrared absorbing film is a film having a low transmittance in the near infrared region of 800 to 1200 nm and a high transmittance in the visible light region of 400 nm to 800 nm. The transmittance in the near infrared region is preferably as low as possible, specifically 40% or less, more preferably 30% or less. When the transmittance is high, absorption of near infrared rays emitted from the plasma display is insufficient, and malfunction of electronic equipment using the near infrared remote controller cannot be prevented.
The transmittance can be adjusted depending on the kind of the near infrared absorbing dye and the amount of the near infrared absorbing dye per unit area.

  As the color tone of the near-infrared absorbing film, when expressed in the Lab color system, the a value is preferably -10.0 to +10.0, and the b value is preferably -10.0 to +10.0. If it is this range, even if it installs in the front surface of a plasma display, it becomes a natural color and is preferable.

  The method for adjusting the color tone can be achieved by the kind of the above-mentioned near-infrared absorbing dye, the amount of the near-infrared absorbing dye per unit area, and further mixing with other dyes. In addition, when pasting with other members, such as an electromagnetic wave prevention film, an antireflection film, glass, using the adhesion layer colored on the front or back of the near-infrared absorption film mentioned below, it becomes a natural color as an optical filter. It is preferable to adjust the color tone.

  As a coating appearance of the near-infrared absorbing layer, a defect having a diameter of 300 μm or more, more preferably 100 μm, should not be present. The defect of 300 μm or more becomes like a bright spot when installed on the front surface of the plasma display, and the defect becomes noticeable. Defects of 100 μm or more and less than 300 μm may be emphasized due to the lens effect or the like by bonding such as adhesive processing, and should be eliminated as much as possible. Also, streaks, unevenness, etc. with a thin coating layer become prominent on the front surface of the display and become a problem.

  It is preferable that the near-infrared absorbing film does not change the transmittance of near-infrared rays and the transmittance of visible light even when left for a long period of time under high temperature and high humidity. When the stability over time at high temperature and high humidity is poor, not only the color tone of the display image changes, but also the effect of the present invention that prevents malfunction of electronic equipment using a near infrared remote control cannot be manifested There is.

  In order to improve the stability over time, the appropriate range varies depending on the type of pigment and resin and additives, but by controlling the type of organic solvent used in the coating solution, the thickness of the coating layer, the drying conditions, etc. It is preferable to reduce the residual solvent amount in the near-infrared absorbing layer or to adjust the content of the pigment in the resin. The amount of residual solvent in the near infrared absorbing layer is preferably as small as possible, and is preferably 3% by mass or less. If the amount is 3% by mass or less, there is substantially no difference in stability over time. However, in order to further reduce the amount of residual solvent, for example, if drying is performed under severe conditions, adverse effects such as poor flatness of the filter occur, and productivity such as reduced pressure drying decreases. Caution must be taken.

  The near-infrared absorbing film of the present invention has a structure in which a near-infrared absorbing layer is provided on one side and an antistatic layer is provided on the other side. A prevention layer may be laminated. By providing an anti-reflection layer and an electromagnetic wave prevention layer, not only can the number of optical filter members be reduced, the cost can be reduced, but also the interface where light interferes (the interface between layers with different refractive indexes) is reduced, improving the image quality of the plasma display. To do.

  Since the antistatic layer can reduce the adhesion of dust at the time of forming the near-infrared absorbing layer or in a subsequent process, it is possible to reduce minute defects and improve the yield in manufacturing. The easy-adhesion layer has a function of improving the adhesion when the adhesive is bonded to another member, and the easy-slip layer has a function of improving handling properties.

  In the present invention, a π-electron conjugated conductive polymer is contained as an antistatic agent used for the antistatic layer. This is because when an antistatic layer is formed before applying a near-infrared absorbing layer on a transparent substrate film, an anionic or cationic surfactant or a quaternary ammonium salt cationic resin is used as an antistatic agent. Then, the antistatic agent adheres to the surface on which the near-infrared absorbing layer is applied due to the setback in the roll state, and the deterioration of the near-infrared absorbing layer is promoted.

(Near-infrared absorbing film roll)
The near-infrared absorbing film of the present invention is obtained through a step of continuously winding a long near-infrared absorbing film in a roll shape around a cylindrical core while bringing the near-infrared absorbing layer and the antistatic layer into contact with each other. A near-infrared absorbing film roll obtained by continuously winding a long near-infrared absorbing film in a roll shape around a cylindrical core is a form in which a long near-infrared absorbing film having a length of 50 m or more and 5000 m or less is wound. When the winding length is short, the frequency of switching the film roll at the time of adhesive processing in the subsequent process is increased and workability is deteriorated. On the contrary, when the winding length is long, the near-infrared absorbing film expands and contracts due to the external environmental temperature, the winding tightening occurs, and the appearance of the core becomes poor.

  The cylindrical core around which the near-infrared absorbing film is wound is preferably a plastic core. When a commonly used paper core is used, paper dust or the like is generated and tends to adhere to the near infrared absorption layer and become defective. As the plastic core, known ones can be preferably used, but a polypropylene core and an FRP core are preferable in terms of strength. The size of the cylindrical core is preferably 3 to 6 inches in diameter. When a core having a small diameter is used, the winding core is wrinkled and the handling property in the subsequent process becomes poor. On the other hand, when the diameter is large, the roll diameter becomes large and the handling property becomes poor.

  In order to wind the near-infrared absorbing film around the core, it is preferable to start winding after fixing the near-infrared absorbing film to the core via a double-sided tape. When a double-sided tape is not used, winding deviation is likely to occur during winding or during transportation. Although a well-known thing can be used as a double-sided tape, what has an adhesion layer on both surfaces of a plastic film is preferable at the point of generation | occurrence | production of paper dust, and an intensity | strength. The thickness of the double-sided tape is preferably 5 μm or more and 50 μm or less. When it is thin, the strength is lowered and workability is deteriorated, and the fixing force of the film is lowered. On the other hand, when it is thick, the flatness of the near-infrared absorbing film at the core becomes poor due to a step due to the tape.

  In this invention, it is preferable to give an unevenness | corrugation (emboss) to the both ends of the width direction of a near-infrared absorption film. By imparting irregularities, it becomes difficult for the core part to be marked with a double-sided tape, and the contact area between the near-infrared absorbing layer and the antistatic layer is lowered, and the storage stability in roll form is improved. . The lower limit of the height of the unevenness is preferably 10 μm, more preferably 15 μm. On the other hand, the upper limit of the height of the unevenness is preferably 40 μm, more preferably 35 μm. When the height of the unevenness is too low, the effect of improving the storage stability in the roll form due to the unevenness is reduced. On the other hand, if the height of the unevenness is too high, winding deviation or the like is likely to occur during transportation. A publicly known method can be used as a method of giving unevenness. Specifically, a method of pressing the metal roll having protrusions on the surface to give irregularities can be mentioned. In addition, before forming a near-infrared absorption layer on a transparent base film, it is preferable to give uneven | corrugated processing to a transparent base film beforehand.

(Optical filter)
In the present invention, the optical filter is installed in front of the plasma display, cuts near infrared rays and electromagnetic waves generated from the display, and prevents reflection to improve display visibility, improves color reproducibility, etc. And further has a display protection function.

  An example of an optical filter is a structure in which an antireflection film, glass, an electromagnetic wave prevention film, and a near infrared absorption film are bonded with an adhesive. The adhesive has an ultraviolet absorbing ability, a color correction function, and a color reproducibility improving function. It is preferable to give. In addition, it is preferable to use a composite film having different functions on the same surface or the opposite surface of the film in terms of reducing the number of members, quantification, and the like. Furthermore, in order to reduce the weight and improve the image quality, it is also preferable to use a directly attached filter that is directly bonded to a plasma display panel without using glass.

  In the present invention, for the purpose of blocking harmful electromagnetic waves emitted from the display, a conductive layer may be provided on the same surface as the infrared absorbing layer or on the opposite surface directly or via an adhesive. The conductive layer may be either a metal mesh or a conductive thin film. When a metal mesh is used, it is necessary to have a metal mesh conductive layer with an aperture ratio of 50% or more. This is because, when the aperture ratio of the metal mesh is low, the electromagnetic shielding property is good, but the light transmittance is lowered. For this reason, in order to obtain a favorable light transmittance, an aperture ratio of 50% or more is required. For metal meshes, there are methods such as etching a metal foil with high electrical conductivity into a mesh, woven mesh using metal fibers, and plating metal on the surface of polymer fibers. You may use the fiber adhered by using. The metal used for the electromagnetic wave absorbing layer may be any metal as long as it has high electrical conductivity and good stability, and is not particularly limited, but copper, nickel, tungsten, and the like are preferable from the viewpoint of workability and cost.

  Moreover, when using a conductive thin film, the transparent conductive layer may be any conductive film, but a metal oxide is preferable. Thereby, a higher visible light transmittance can be obtained. Moreover, when it is desired to further improve the conductivity of the transparent conductive layer, it is preferable to have a repeating structure of three or more layers of metal oxide / metal / metal oxide. Conductivity can be obtained while maintaining a high visible light transmittance by multilayering the metal. The metal oxide may be any metal oxide as long as it has conductivity and visible light transmittance. Examples thereof include tin oxide, indium oxide, indium / tin composite oxide (ITO), zinc oxide, titanium oxide, and bismuth oxide. The above metal oxides are representative examples and are not particularly limited. The metal layer is preferably gold, silver or a compound containing them from the viewpoint of conductivity.

  Further, when the conductive layer is formed into multiple layers, for example, when the number of repeating layers is 3, the thickness of the silver layer is preferably 50 to 200 mm, more preferably 50 to 100 mm. When the film thickness is thicker than this, the light transmittance decreases, and when it is thin, the resistance value increases. Further, the thickness of the metal oxide layer is preferably 100 to 1000 mm, more preferably 100 to 500 mm. If it is thicker than this thickness, it is colored to change its color tone, and if it is thin, the resistance value increases. Furthermore, in the case of multi-layering to three or more layers, for example, in the case of five layers such as metal oxide / silver / metal oxide / silver / metal oxide, the thickness of the central metal oxide is other than that It is preferable that it is thicker than the thickness of the metal oxide layer. By doing in this way, the light transmittance of the whole multilayer film improves.

  The antireflection layer has a function of preventing surface reflection and preventing reflection of a fluorescent lamp or the like. The method for imparting the antireflection function can be arbitrarily selected without limitation. For example, a layer having a different refractive index is laminated on the surface of the base film, and the reflection is reduced by using interference of reflected light at the interface of the layer. Examples thereof include a method and a method of imparting unevenness to the surface. The method of forming the antireflection film of this method can be roughly divided into the following two methods.

  The first method is a method of forming an antireflection film on the surface of the base film by vapor deposition or sputtering. The second method is a method of forming an antireflection film by applying an antireflection coating liquid on the surface of a base film and drying it. As a general theory, it is said that the former is superior in terms of antireflection characteristics and the latter is superior in terms of economy, but either method may be used in the present invention.

  Next, this invention is demonstrated using an Example and a comparative example. The characteristic value measurement method and effect evaluation method used in the present invention are as follows.

<Surface resistance>
Measurement was performed under the conditions of an applied voltage of 500 V, 20 ° C., and 55% RH using a Mitsubishi Oil Chemical surface resistance meter.

<Viscosity of coating liquid>
The coating solution was adjusted to 20 ° C. and measured using a B-type viscometer (BL) manufactured by Tokyo Keiki Co., Ltd., at a rotor rotational speed of 60 rpm.

<Total light transmittance, haze>
Using a haze meter (Nippon Denshoku Industries, NDH2000), the total light transmittance and haze were measured.

<Transmissivity>
Using a spectrophotometer (Shimadzu Corporation UV-3150 type), in the wavelength range of 300 to 1200 nm, the near-infrared absorbing layer side was irradiated with light, and indoor air was measured as a reference for transmittance.

<Color tone>
Using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., ZE-2000), the near-infrared absorbing layer side is irradiated with light. Measured at viewing angle.

<Stability over time>
The color tone was measured after being allowed to stand for 48 hours in an atmosphere of temperature 80 ° C. and humidity 95%. As the amount of change in color tone, ΔE was obtained from the following equation (2). Note that ΔE indicates that the smaller the value, the smaller the change in color tone.

ΔE = √ ((a value before processing−a value after processing) ² + (b value before processing−b value after processing) ² )
... (2)

<Storage stability>
The film was left in a roll form at 50 ° C. for 30 days, and the above transmittance and color tone were measured. As the amount of change in color tone, ΔE was obtained from equation (1). Note that ΔE indicates that the smaller the value, the smaller the change in color tone.

<Appearance of coating film>
The near-infrared absorbing film was placed on a white film (Toyobo Co., Ltd., Chrispar K1212; 100 μm), and minute defects were observed under a three-wavelength fluorescent lamp.
First, mark all defects that are visually observed. If there are many defects, stop halfway. Next, the size of the defect is confirmed with an optical microscope, and a minute defect having a diameter of 100 μm or more per 100 m ² is classified into a size range of 100 μm or more and less than 200 μm, 200 μm or more and less than 300 μm, or 300 μm or more. Then, the number of defects is measured.

Example 1
(Base film)
A polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g is charged into a twin screw extruder, melt extruded from a T-die at 290 ° C., and electrostatic is applied on a cooled rotating metal roll. Then, the sheet was solidified while being adhered to obtain an unstretched sheet.
Next, the unstretched sheet was heated to 90 ° C. with a roll stretching machine and longitudinally stretched by 3.5 times, and then the coating amount after drying the following coating liquid A on the longitudinally stretched film was 0.5 g / The intermediate coating layer was formed by applying to both sides so as to be m ^2, and passing it for 20 seconds under a hot air of 10 m / second and 120 ° C. Further, the film was heated by a tenter to 140 ° C. and transversely stretched 3.7 times, and then heat treated while being relaxed 5% in the width (lateral) direction at 235 ° C. to obtain a film. Furthermore, while slitting the edge part of the obtained film, it embossed the protrusion of 20 micrometers with the width of 15 mm of both ends, and obtained the roll of 2100 m with a width of 1.3 m. The obtained biaxially stretched polyethylene terephthalate film having an intermediate coating layer had a thickness of 100 μm, a total light transmittance of 90.2%, and a haze of 0.5%.

(Composition of coating liquid A for intermediate coating layer)
・ Ion-exchanged water 50.0% by mass
・ Isopropyl alcohol 28.9% by mass
・ Acrylic-melamine resin 10.0% by mass
(Nippon Carbite, A-08, solid content: 46% by mass)
・ Polyester resin 10.0% by mass
(Toyobo, MD-1250, solid content: 30% by mass)
・ 1.0% by mass of organic particles
(Nippon Shokubai, Eposta MA1001)
・ Surfactant 0.1% by mass
(Paintad 32, manufactured by Dow Corning Co., Ltd.)

(Lamination of antistatic layer)
The following coating solution B (solid content concentration: 1% by mass) is applied on the transparent substrate film by a microgravure method so that the coating amount after drying is 0.1 g / m ² , and 10 m at 100 ° C. The antistatic layer was laminated by passing under a hot air of / sec for 10 seconds. The surface resistance was 2.1 × 10 ⁷ Ω / □.
(Coating solution B for antistatic layer)
・ Water 10.0% by mass
・ Isopropyl alcohol 80.0% by mass
-Thiophene resin (manufactured by Nagase Chemitex, Denatron P-502RG) 10.0% by mass

(Lamination of near-infrared absorbing layer)
The following coating solution C (solid content concentration: 16% by mass, viscosity: 28 cps) is opposite to the antistatic layer, and the transmittance at a wavelength of 950 nm after drying is 4.3% (coating amount: 8.0 g / m ² ) and applied with reverse using a diagonal gravure with a diameter of 60 cm, heated at 40 ° C. with hot air of 5 m / second for 20 seconds, 150 ° C. with hot air of 20 m / second for 20 seconds, and further at 90 ° C. A near-infrared absorbing film is produced by passing it through hot air of 20 m / sec for 10 seconds and drying, and further, a near-infrared absorbing film is wound around a polypropylene cylindrical core made of 6 inches in diameter. A 2000 m near-infrared absorbing film roll was prepared.

(Coating liquid C for near-infrared absorbing layer)
The mixture was mixed at the following mass ratio and stirred for 30 minutes or more to dissolve the dye. Subsequently, undissolved substances were removed with a filter having a nominal filtration accuracy of 1 μm to prepare a coating solution.
・ Toluene 23.054 mass%
・ Methyl ethyl ketone 23.054% by mass
-Acrylic resin 52.695% by mass
(GS-1030, manufactured by Soken Chemical Co., Ltd., solid content concentration: 30% by mass, Tg: 110 ° C.)
・ Diimonium salt compound 0.731% by mass
(Nippon Carlit, CIR-RL)
・ Phthalocyanine pigment 0.407% by mass
(Nippon Shokubai, IR-10A)
・ Surfactant 0.059% by mass
(Dow Corning Paintad 57, HLB: 6.7)

  The obtained near-infrared absorbing film had strong absorption in the near-infrared region and was excellent in transmittance in the visible light region. Furthermore, the stability over time was excellent, and there were few micro defects and it was good. Moreover, the storage stability in a roll form was also good. Tables 1 and 2 show the properties of the near-infrared absorbing film and the roll.

Example 2
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the coating amount after drying of the antistatic layer was adjusted to 0.02 g / m ² . The surface resistance after laminating the antistatic layer was 3.5 × 10 ¹⁰ Ω / □.
The obtained near-infrared absorbing film had excellent temporal stability and few micro defects as in Example 1.

Example 3
In Example 1, a near-infrared absorbing film roll was prepared in the same manner as in Example 1 except that a paper cylindrical core was used as the core.
Compared with Example 1, the obtained near-infrared absorption film had increased minute defects at the core.

Example 4
In Example 1, a near-infrared absorbing film roll was obtained in the same manner as in Example 1 except that the unevenness treatment was not performed on both ends during the production of the film.
The obtained near-infrared absorbing film was slightly deteriorated in storage stability as compared with Example 1.

Comparative Example 1
In Example 1, a near-infrared absorbing film was obtained in the same manner as in Example 1 except that the antistatic layer was not laminated. In addition, the surface resistance of the transparent base film before laminating | stacking a near-infrared absorption layer was 10 < ¹⁴ > ohm / square or more, and was inferior to antistatic property.
Therefore, when the near-infrared absorbing film wound up in a roll shape was unwound, charging of 7 kV occurred. As a result, the near-infrared absorbing film after unwinding adsorbed foreign matter in the air to the surface with static electricity, and the number of minute defects increased.

Comparative Example 2
In Example 1, a near-infrared absorbing film was obtained in the same manner as in Example 1 except that the following coating solution D was used as the coating solution for forming the antistatic layer. The surface resistance after forming the antistatic layer was 4.2 × 10 ⁸ Ω / □.
(Coating solution D for antistatic layer)
・ Water 50.0 mass%
・ Isopropyl alcohol 45.0% by mass
・ Cationic polymer antistatic agent 5.0% by mass
(Sanyo Chemicals, Chemist 6300H)

  Since the obtained near-infrared absorbing film used a cationic antistatic agent as an antistatic agent, the diimmonium salt compound in the near-infrared absorbing layer deteriorated in a roll form, and the storage stability was poor.

Comparative Example 3
In Example 1, a near-infrared absorbing layer was obtained in the same manner as in Example 1 except that the following coating liquid E was used as the coating liquid for forming the antistatic layer. The surface resistance after forming the antistatic layer was 4.1 × 10 ¹³ Ω / □.
(Coating solution E for antistatic layer)
・ Water 50.0 mass%
・ Isopropyl alcohol 45.0% by mass
・ Anionic polymer antistatic agent 5.0% by mass
(Sanyo Chemicals, Chemist SA-9)

  Since the obtained near-infrared absorbing film was inferior in antistatic properties, charging of 5 kV was generated when the near-infrared absorbing film wound up in a roll shape was unwound. As a result, the near-infrared absorbing film after unwinding adsorbed foreign matter in the air to the surface with static electricity, and the number of minute defects increased. Furthermore, since an anionic antistatic agent was used as the antistatic agent, the diimmonium salt compound in the near-infrared absorbing layer was deteriorated, resulting in poor storage stability in the roll form.

  The near-infrared absorbing film of the present invention has low transmittance in the near-infrared region, high transmittance in the visible light region, and good coating appearance. Even if it is installed on the front of the display, it is possible to express a good image without defects and to prevent malfunction of an electronic device using a near-infrared remote controller, contributing to the industry.

Claims (1)

A method for producing a near-infrared absorbing film comprising a near-infrared absorbing layer on one side of a transparent substrate film and an antistatic layer laminated on the other side,
After providing an antistatic layer containing a π-electron conjugated conductive polymer on the other surface of the transparent substrate film, a coating solution containing a resin and a diimmonium salt compound is applied to the one surface of the transparent substrate film and dried. And
A method for producing a near-infrared absorbing film, comprising a step of continuously winding a cylindrical core around a cylindrical core while bringing the near-infrared absorbing layer and the antistatic layer into contact with each other.