JP2005189737A - Near-infrared ray absorption film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a near-infrared ray absorption film which has a near-infrared ray absorption layer, is capable of selectively absorbing the light of a wavelength that deteriorates color purity and near-infrared rays, hardly causes a variation of tone in the film TD direction and has an excellent appearance of the near-infrared ray absorption layer, and to provide a manufacturing method of the near-infrared ray absorption film. <P>SOLUTION: The near-infrared ray absorption film comprises the near-infrared ray absorption layer which contains a near-infrared ray absorbing pigment, a resin, a surfactant, and a transparent base material. Therein, the maximum value of a color difference Δ in the TD direction calculated from the tone measured at every prescribed measurement parts is ≤1.0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a near-infrared absorbing film suitable for a plasma display filter.

  Near-infrared absorbing films having near-infrared absorbing ability have the property of blocking near-infrared rays and allowing visible light to pass through, and are used in various applications.

  In recent years, a plasma display attracting attention as a thin large-screen display has a problem that an electronic device using a near-infrared remote controller malfunctions due to near-infrared rays emitted from the plasma display. Therefore, a near-infrared absorption filter having a near-infrared absorbing film as a constituent element is arranged on the front surface of the plasma display, and the above-described problems are solved by absorbing near-infrared rays emitted from the display. .

  As a filter having near infrared absorption ability, (1) a filter in which metal ions such as copper and iron are contained in succinic acid glass; (2) a layer having different refractive indexes is laminated to interfere with incident light. (3) Acrylic resin filter containing copper ions in an acrylic copolymer; (4) A layer in which a pigment is dispersed or dissolved on a substrate A filter laminated on the substrate has been proposed.

  Among these, many proposals have been made since the filter (4) has good processability and productivity and has a relatively high degree of freedom in optical design (for example, Patent Documents 1 to 9).

  In recent years, plasma displays have also been trending toward larger screens. However, when applied to such large screen displays, the light transmittance at a specific wavelength in the longitudinal direction of the film is considered to reduce light transmittance and color spots. There has been proposed a wavelength control film with little fluctuation (for example, Patent Document 10). In this method, after the light absorbing layer is applied to the film, laser light of a specific wavelength is irradiated before drying or cooling, and the number of coatings is controlled by controlling the rotation speed of the microgravure so that the fluctuation of the transmission intensity is reduced. When it is made uniform and pasted on a large screen such as a plasma display, light transmittance and color spots in the screen are reduced.

  By the way, in response to the recent demand for higher image quality by increasing the brightness and definition of plasma displays, not only the basic characteristics described above, but also the small variation in color tone over the entire screen and the appearance of the near-infrared absorbing layer It is also important to be good.

However, in the techniques described in the above Patent Documents 1 to 9, there is no description or suggestion regarding a method of improving the color tone variation and appearance of the near-infrared absorbing film, and when used in a filter for a plasma display, It cannot be said that the change in the color tone of the entire screen is sufficiently suppressed. In addition, the method described in Patent Document 10 can control the color tone fluctuation in the film longitudinal direction (MD direction) to some extent, but the color tone fluctuation suppression in the film width direction (TD direction) is not sufficient. When used for a plasma display filter, the change in the color tone of the entire screen cannot always be sufficiently suppressed, and the appearance cannot be said to be satisfactory.
JP 2002-82219 A JP 2002-138203 A JP 2002-214427 A JP 2002-264278 A JP 2002-303720 A JP 2002-333517 A JP 2003-82302 A JP 2003-96040 A JP 2003-114323 A JP 2002-341132 A

  The present invention has been made in view of the above circumstances, and its purpose is to select light having a near infrared absorption layer and selecting light and near infrared light having a wavelength that reduces color purity when used in a plasma display filter. It is providing the near-infrared absorptive film which can be absorbed in general, Comprising: The near-infrared absorptive film in which the fluctuation | variation of the color tone in film TD direction is small, and the external appearance of a near-infrared absorption layer is excellent, and its manufacturing method.

The near-infrared absorbing film of the present invention capable of achieving the above object includes a near-infrared absorbing layer and a transparent substrate as constituents, and the near-infrared absorbing layer comprises a near-infrared absorbing dye, a resin, and a surface active material. In the above film, the maximum value of the color difference Δ in the TD direction [direction perpendicular to the running direction (MD direction) during film production] obtained by the following measurement method (A) is 1.0 or less. It has the gist.
(A) In measuring the color tone of the film, when one end in the TD direction of the film is a first end and the other end is a second end, 1 is measured within 0.1 m from the first end. The second measurement is performed at a location within 0.1 m inside from the second end, and at three locations at approximately equal intervals between the first measurement location and the final measurement location. The color difference Δ defined by the following formula (1) is calculated at five measurement points.
ΔE = [(L _a −L _m ) ² + (a _a −a _m ) ² + (b _a −b _m ) ² ] ^1/2 (1)
Here, L _m, a _m, b _m means a color L, a, b in each measurement _{point, L a, a a, b} a , the color L, a, the average value of b in all measurement points Means.

  As the near-infrared absorbing film, a film containing a diimmonium salt compound is preferable as the near-infrared absorbing dye.

In addition, a near-infrared absorbing film manufacturing method in which a coating solution containing a near-infrared absorbing dye, a resin, a surfactant, and an organic solvent is continuously applied on a transparent substrate and dried to form a near-infrared absorbing layer. A method for producing a near-infrared absorbing film, wherein the coating solution is applied by a kiss coating method, and the tension in the MD direction at the coating portion of the transparent substrate is controlled to 0.5 N / mm ² or more and 1.2 N / mm ² or less. Are also encompassed by the present invention.

  In the method of the present invention, the coating solution is applied by a gravure / kiss coater having a gravure roll, and the speed ratio of the rotational speed G (m / min) of the gravure roll to the running speed F (m / min) of the film. G / F is preferably set to 0.8 to 1.5. The gravure / kiss coat apparatus has a mechanism for scraping off the coating liquid from the liquid supply pan with a reverse rotating gravure roll and scraping off the excess coating liquid with a doctor blade, and is in contact with at least the gravure roll of the doctor blade. The part is preferably a device made of ceramics or nickel.

Moreover, in the said invention method, it is recommended that the drying process after apply | coating the said coating liquid consists of the following 1st drying process, 2nd drying process, and a cooling process.
1st drying process: It dries with the wind whose temperature is 20-80 degreeC and a wind speed is 2-30 m / sec; 2nd drying process: It is 5 to 180 seconds with the wind whose temperature is 120-180 degreeC; Cooling process: It cools with the wind below the glass transition temperature of resin which comprises a near-infrared absorption layer.

  In this specification, “film” is a concept including so-called sheets.

  When the near-infrared absorbing film of the present invention is installed on the front surface of the plasma display as a filter member, it absorbs unnecessary near-infrared rays emitted from the display and uses a near-infrared remote control as in the conventional near-infrared absorbing film. Not only can the malfunction of electronic equipment be prevented, but the variation in color tone in the width direction of the film is small, so when used in a filter for plasma displays, the variation in color tone can be suppressed over the entire display screen. Furthermore, since the near-infrared absorbing layer has a good appearance and has very few optical defects, it can contribute to high image quality of the plasma display.

  Moreover, according to the manufacturing method of this invention, the above near-infrared absorption films can be manufactured favorably.

  Hereinafter, the near-infrared absorbing film of the present invention will be described in detail.

<Color difference Δ>
The near-infrared absorbing film of the present invention has the greatest feature in that the maximum value of the color difference Δ in the film TD direction obtained by the measurement method (A) is 1.0 or less. The color difference Δ is determined by the following measurement method.

  First, the color tone of the film is measured. The color measurement is based on the first measurement at a position within 0.1 m inside the first end and the second end when one end in the TD direction of the film is the first end and the other end is the second end. The final measurement is performed at a position within 0.1 m inside the, and three measurements are performed at approximately equal intervals between the first measurement position and the final measurement position.

  The color tone is measured by using a color difference meter (such as “ZE-2000” manufactured by Nippon Denshoku Industries Co., Ltd.), using standard light as a D65 light source, viewing angle of 10 degrees, and irradiating the near infrared absorption layer side with light. The L value, a value, and b value of the Lab display system are obtained. For the measurement of color tone, a method of cutting out measurement samples at the respective measurement points and measuring these samples may be employed, or a method of directly measuring a film without cutting out the measurement sample may be employed. .

  The L value is a measure of lightness, and the larger the value, the less darkening and the higher the lightness. The a value is a scale indicating redness, and the greater the value, the stronger the redness, and the larger the value on the negative side, the stronger the greenness. The b value is a scale indicating yellowishness. The larger the numerical value, the stronger the yellowishness, and the larger the numerical value on the minus side, the stronger the blueness.

  At each measurement location, the L value, a value, and b value are obtained, and the color difference Δ at each measurement location is calculated by the above equation (1). Of the color differences Δ at the respective measurement points obtained in this way, the one showing the maximum value must be 1.0 or less.

  In a film in which the maximum value of the color difference Δ in the TD direction exceeds the above upper limit value, it may cause color spots on the display screen when used in a filter for plasma display. The maximum value of the color difference Δ is preferably 0.5 or less, and more preferably 1.0 or less.

  As the color tone of the film, for example, the a value is preferably -10.0 or more and +10.0 or less, and the b value is preferably -10.0 or more and +10.0 or less. When the a value and the b value are within such a range, a natural color is obtained even when used for a filter for plasma display. Such color tone adjustment can be achieved by the types of near-infrared absorbing dyes, the concentration of these dyes per unit area in plan view of the near-infrared absorbing layer, and further mixing of other dyes. As will be described later, the film of the present invention may be used as a filter for plasma display by providing another optical film, an adhesive layer, or the like on the front surface and / or back surface thereof. When these are provided, it is desirable to adjust the color tone so as to obtain a natural color including these.

  A higher L value is preferable. The higher the L value, the brighter the plasma display can be provided when used as a plasma display filter. The L value is preferably 80 or more, and more preferably 85 or more.

Further, in the film of the present invention, particularly in the case of a long film, in the MD direction of the film, the maximum value of the color difference Δ obtained by the following measurement method (B) is preferably 2.0 or less, More preferably, it is 1.0 or less.
(B) In measuring the color tone of the film, when the end of the steady region where the film properties are stable is the first end and the other end is the second end in the MD direction of the film, The first measurement is performed within 2 m inside the part, the final measurement is performed within 2 m inside the second end, and the measurement is performed about every 10 m from the first measurement point. 1) The color difference ΔE defined by the equation is calculated.

  The measurement method (B) will be described in more detail. The color tone measurement of the film is performed in the steady region where the film physical properties are stable in the MD direction of the film. When one end of the steady region is the first end and the other end is the second end, The first measurement is performed within 2 m inside the I end, the final measurement is performed within 2 m inside the II end, and the measurement is performed about every 10 m from the first measurement point.

  In addition, the color measurement is measured in the steady region of the film, and the film of the present invention is subjected to a step of applying and drying a coating solution for forming a near-infrared absorbing layer on a transparent substrate as described later. Although it is manufactured, in the case of a long film, the physical properties of the film may fluctuate until the operation in the coating process or drying process of the coating liquid is stabilized. The preferred embodiment of the present invention is not intended to make the color difference Δ of the film obtained when the operation in the coating process or the drying process is unstable, but the operation in these processes. In the film having stable physical properties obtained when the production is in a steady state, the color difference Δ in the MD direction is made more uniform than before.

  In addition, the number of steady regions (film portions obtained when production enters a steady state) where the film physical properties are stable is usually one place in one film (including the case of one place over the entire length of the film). Only. However, depending on the manufacturing situation, there may be a plurality of locations. In this case, the color tone measurement may be performed only in the steady region. The steady region can be evaluated by, for example, the value of the color difference Δ. That is, a stable region where the color difference Δ is 2 or less may be regarded as a steady region.

  Also, the color tone measurement in the TD direction of the film is naturally performed in the steady region of the film.

  The color tone may be measured by the same method as in the film TD direction. At that time, the film may be wound into a film roll, the film may be drawn from the film roll, and measured while being wound on another roll. You may employ | adopt the method of measuring a color tone.

  In addition, as a measurement site | part of the film in each measurement location, it is common to match | combine the position of the TD direction of a film, However, In the film of this invention, since the fluctuation | variation of the color tone in the TD direction of a film is suppressed, Even if the measurement part of the film is changed for each measurement part, the color tone fluctuation in the film MD direction can be satisfactorily evaluated.

  At each measurement location, the L value, a value, and b value are obtained, and the color difference Δ at each measurement location is calculated by the above equation (1). It is recommended that the color difference Δ obtained at each measurement point as described above is 2.0 or less that shows the maximum value.

  In a film in which the maximum value of the color difference Δ exceeds the above upper limit value, the variation in color tone in the film MD direction is large, and in many plasma display filters obtained from the film, the color tone between products (between filters) may be different. In other words, it may be difficult to provide a plasma display filter with stable quality.

  The near-infrared absorbing film in which such variation in color tone is suppressed (that is, the maximum value of the color difference Δ in the film TD direction and further in the film MD direction is controlled to be equal to or less than the above upper limit value) By adopting the method, it can be obtained.

<Transparent substrate>
As the transparent substrate, a plastic film is preferable from the viewpoint of ensuring high transparency, cost, and ease of handling. Specifically, polyester-based, acrylic-based, cellulose-based, polyolefin-based (polyethylene, polypropylene, and other copolymer types), polyvinyl chloride-based, polycarbonate, phenol-based, urethane-based resin films, etc. Can be mentioned. Among them, a polyester film is preferable in terms of a good balance between heat resistance and flexibility, and a polyethylene terephthalate (PET) film is more preferable.

  “Transparent” of the transparent substrate means that the total light transmittance is 80% or more, preferably 90% or more. Further, the haze of the transparent substrate is preferably 5% or less, and more preferably 2% or less. When the transparency of the transparent substrate is inferior, the brightness of the display is lowered and the sharpness of the image becomes poor. In addition, the said total light transmittance and haze are the values measured by the method prescribed | regulated to JISK7136.

  Polyesters used for polyester films include esters of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, and esters thereof, and glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, and neopentyl glycol. A product obtained by conducting a polycondensation reaction or a transesterification reaction followed by a polycondensation reaction can be mentioned, and is usually supplied in the form of a polymer chip. As the polyester film, the polymer chip is melted, extruded from a T-die into a sheet to obtain an unstretched film, stretched in at least a uniaxial direction (preferably a biaxial direction) of the unstretched film, and then heat set. A film produced by performing a relaxation treatment or the like is common.

  As the polyester film, a biaxially stretched film is particularly preferable from the viewpoint of strength and the like. As the stretching method, a tubular stretching method, a simultaneous biaxial stretching method, a sequential biaxial stretching method, and the like are common, but a sequential biaxial stretching method in terms of flatness, dimensional stability, thickness unevenness, etc. of the obtained film. Is recommended. For example, the sequential biaxially stretched film is roll-stretched 2.0 to 5.0 times at a glass transition temperature (Tg) to Tg + 30 ° C. of the polyester in the longitudinal direction of the polyester-based unstretched film, and subsequently in the width direction. The film is stretched 1.2 to 5.0 times at 120 to 150 ° C. using a tenter, further heat-set at a temperature of 220 ° C. or higher after biaxial stretching, and then relaxed by 3 to 8% in the width direction. Manufactured by.

  For the purpose of improving the handling property (for example, the winding property after lamination of the near-infrared absorbing layer), it is desirable that the transparent substrate contains particles to form protrusions on the surface. Particles include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, titanium oxide; acrylic resins, polyamide resins, polystyrene resins, polyester resins, Organic particles such as benzoguanamine / formalin condensate. In order to maintain the transparency of the film, the content of particles in the transparent substrate is preferably small, for example, 1000 ppm or less. The transparent base material may contain various additives such as a coloring material, a light fastness agent, a fluorescent agent, and an antistatic agent in order to impart various functions as necessary.

  The transparent substrate may have a single layer structure, for example, a laminated structure of two or more layers (two layers, three layers, four layers, etc.). In the case of a laminated structure, there is an advantage that the function of each layer can be designed independently. For example, in the case of a two-layer structure, the surface layer of the near-infrared absorbing film is a thin layer, and the above particles are included only in the layer to form irregularities on the surface, and between the surface layer and the near-infrared absorbing layer The layer (center layer) is a thick layer, and the layer does not substantially contain the above-described particles, thereby reducing the amount of particles used and improving transparency, while providing high handling properties. It can be secured.

  The above-mentioned “substantially free of particles” state is a state in which particles are not actively included except for particles inevitably mixed from the outside. When quantitative analysis is performed by the X-ray method, it is a state that is below the detection limit (the same applies hereinafter).

  The production method of the transparent substrate having a laminated structure is not particularly limited. However, in consideration of productivity, the raw materials of each layer are extruded from separate extruders and led to one die to form an unstretched film having a laminated structure. A so-called coextrusion method in which stretching is performed can be preferably employed.

  Moreover, it is also preferable to provide an anchor layer in a transparent base material for the purpose of the improvement of the adhesiveness of this base material and a near-infrared absorption layer, and the transparency improvement of a transparent base material.

  Examples of the resin constituting the anchor layer include polyester resins, polyurethane resins, polyester urethane resins, acrylic resins, melamine resins, and the like. ) And a material excellent in adhesion to the near-infrared absorbing layer. For example, when the resin of the base layer of the transparent substrate and the near-infrared absorbing layer is a polyester resin, it is desirable to select a polyester resin or a polyester urethane resin as the resin constituting the anchor layer.

  It is also preferable to introduce a crosslinked structure into the anchor layer for the purpose of improving the adhesion with the near-infrared absorbing layer and improving the water resistance. Such a crosslinked structure can be introduced by using a crosslinking agent (various crosslinking agents such as urea, epoxy, melamine, and isocyanate). In particular, when the resin constituting the anchor layer is whitened or reduced in strength under high temperature and high humidity, the improvement effect due to the introduction of the crosslinked structure is remarkably exhibited.

  For the purpose of improving handling properties, the above-mentioned particles used for forming surface irregularities may be contained in the anchor layer. From the viewpoint of improving the transparency, it is desirable to select particles having a refractive index close to that of the resin used for the anchor layer. For example, when using a polyester-based resin (copolyester resin or the like) for the anchor layer, Silica is preferred. By adopting a configuration in which the base layer of the transparent base material contains substantially no particles but only the anchor layer contains particles, the amount of particles used is reduced and the transparency is improved, and advanced handling Can be secured.

  Furthermore, the anchor layer may contain various additives such as a surfactant, an antistatic agent, a fluorescent dye, a fluorescent brightening agent, and an ultraviolet absorber for the purpose of imparting various functions.

  The anchor layer may have a single layer structure, or may have a laminated structure of two or more layers (two layers, three layers, four layers, etc.) as necessary.

  As a method for forming the anchor layer, a transparent substrate is used by using a known method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, a reverse roll coating method, etc. An in-line coating method in which an anchor layer is provided during the manufacturing process of the base layer (the resin film) and an off-line coating method in which an anchor layer is provided after the base layer is manufactured. Of these methods, the in-line coating method is particularly preferable. The in-line coating method is not only excellent in cost but also easy to reduce the coating thickness. Therefore, when the particles are contained in the anchor layer, there is no need to substantially contain the particles in the base layer. Protrusions can be efficiently formed with particles contained in the anchor layer. Therefore, the transparency can be further improved while improving the handleability of the transparent substrate.

  The preferred thickness of the transparent substrate varies depending on the material. For example, in the case of a polyester film, it is desirably 35 μm or more, more preferably 50 μm or more, and 260 μm or less, more preferably 200 μm or less. . If the thickness is too thin, handling properties will be poor, and when forming near infrared absorption layers, if drying is performed under strict conditions to reduce the amount of residual solvent, thermal wrinkles will occur and flatness will be poor. Sometimes. On the other hand, if the thickness is too thick, it is disadvantageous in terms of cost, and flatness defects due to curling may occur when wound and stored in a roll shape.

  The thickness of the anchor layer is not particularly limited as long as the intended function can be ensured, but is preferably 0.01 μm or more and 5 μm or less, for example. When the thickness is too thin, the function as the anchor layer is difficult to be exhibited, and when it is too thick, the transparency is easily impaired.

<Near infrared absorbing layer>
The near-infrared absorbing layer is a layer mainly composed of a near-infrared absorbing dye, a resin, and a surfactant, and is formed on a transparent substrate (or on an anchor layer when the transparent substrate has an anchor layer). It is. In addition, said "main component" means that the total amount of near-infrared absorption pigment | dye, resin, and surfactant is 80-100 mass% in a near-infrared absorption layer.

  The near infrared absorbing dye is a dye having a maximum absorption wavelength at 800 to 1200 nm. Specifically, diimmonium, phthalocyanine, dithiol metal complex, naphthalocyanine, azo, polymethine, anthraquinone, pyrylium, thiopyrylium, squarylium, croconium, tetradehycholine, triphenylmethane And various compounds. These near-infrared absorbing dyes are used alone or in admixture of two or more. Among these, it is preferable to include a diimmonium salt compound represented by the following general formula (2), which has a large absorption in the near infrared region, a wide absorption region, and a high transmittance in the visible light region.

(Wherein R _{1 to} R ₈ represent a hydrogen atom, an alkyl group, an aryl group, an alkenyl group, an aralkyl group, and an alkynyl group, and may be the same or different. R _{9 to} R ₁₂ may be different from each other). Represents a hydrogen atom, a halogen atom, an amino group, a cyano group, a nitro group, a carboxyl group, an alkyl group or an alkoxyl group, which may be the same or different, and each of R _{1 to} R ₁₂ binds a substituent. can things which may have a substituent .X ^- represents an anion).
Specific examples of R _{1 to} R _{8 in} the above formula (2) include the following. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, tert-butyl group, n-amyl group, n-hexyl group, n-octyl group, Examples include 2-hydroxyethyl group, 2-cyanoethyl group, 3-hydroxypropyl group, 3-cyanopropyl group, methoxyethyl group, ethoxyethyl group, butoxyethyl group. Examples of the aryl group include a phenyl group, a fluorophenyl group, a chlorophenyl group, a tolyl group, diethylaminophenyl, and a naphthyl group. Examples of the alkenyl group include a vinyl group, a propenyl group, a butenyl group, and a pentenyl group. Examples of the aralkyl group include a benzyl group, a p-fluorobenzyl group, a p-chlorophenyl group, a phenylpropyl group, and a naphthylethyl group.

R _{9 to} R ₁₂ in the above formula (2) are 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 group and the like. X ^- includes fluorine ion, chlorine ion, bromine ion, iodine ion, perchlorate ion, hexafluoroantimonate ion, hexafluorophosphate ion, tetrafluoroborate ion and the like. However, the present invention is not limited to those mentioned above. Some of these are available as commercial products. For example, “Kayasorb IRG-022” manufactured by Nippon Kayaku Co., Ltd. and “CIR-1085” manufactured by Nippon Carlit Co., Ltd. can be suitably used.

  In the near-infrared absorbing film of the present invention, together with the diimmonium salt compound represented by the above formula (2), other near-infrared absorbing dyes may be used in combination for the purpose of expanding the absorption range in the near-infrared region and adjusting the color. preferable.

In the film of the present invention, the near-infrared absorbing dye sufficiently absorbs the target near-infrared ray, while adjusting the type and ratio so that the visible light transmittance is not impaired, and is contained in the near-infrared absorbing layer. Is required. For example, by adjusting the thickness of the near infrared absorbing layer and the content of the near infrared absorbing dye, the concentration of the near infrared absorbing dye per unit area in a plan view of the near infrared absorbing layer of the near infrared absorbing film is 0.01 to It is recommended to control to 1.0 g / m ² . If the amount of the near-infrared absorbing dye per unit area in a plan view of such a near-infrared absorbing layer is too small, the absorption ability in the near-infrared region may be insufficient. On the other hand, if the amount is too large, the transmittance in the visible light region may be insufficient. In other words, the brightness of the display may be lowered when the plasma display filter is used because of lack of (that is, transparency).

  The resin used for the near-infrared absorbing layer is not particularly limited as long as it can uniformly dissolve or disperse the near-infrared absorbing dye and can ensure transparency. For example, polyester-based, acrylic-based, polyamide-based, polyurethane-based Polyolefin-based and polycarbonate-based various resins are suitable. In particular, a polyester resin is recommended in terms of excellent properties such as flexibility. If the resin is hard, minute cracks may occur during the process of forming an adhesive layer for bonding to the plasma display panel or the process of bonding to the plasma display panel.

  Furthermore, it is desirable that the Tg of the resin be equal to or higher than the guaranteed use temperature of a device (for example, a plasma display) to which the film of the present invention is applied. When the Tg of the resin is lower than the guaranteed use temperature of the applicable device, the dyes dispersed in the resin react when the film is used, or the resin absorbs moisture during the period and deteriorates the resin and the dye May go on.

  The Tg of the resin is more preferably 85 ° C. or higher (more preferably 100 ° C. or higher) and 160 ° C. or lower. When the Tg of the resin is below the above range, the interaction between the dye and the resin, the interaction between the dyes, and the like occur, and the frequency of the modification of the dye tends to increase. As will be described later, the near-infrared absorbing layer is formed by a method in which a coating liquid containing a near-infrared absorbing dye, a resin, a surfactant and a solvent is applied onto a transparent substrate and dried. If the Tg exceeds the above range, it is necessary to heat to a high temperature in order to sufficiently remove the solvent, wrinkles will enter the transparent substrate, and the flatness will be lowered, or the deterioration of the pigment will be likely to occur. On the other hand, when drying is performed at a low temperature, a prolonged drying time is unavoidable, and productivity tends to be remarkably deteriorated. Moreover, when drying becomes inadequate, the residual amount of the coating-solution solvent in a near-infrared absorption layer will increase. When the amount of residual solvent in the near-infrared absorbing layer is increased, the apparent Tg of the resin is lowered, so that the dye is easily modified.

  The content of the near infrared ray absorbing dye in the total amount of the resin and the near infrared ray absorbing dye is preferably 1% by mass or more and 10% by mass or less. More preferably, it is 1.5 mass% or more and 5 mass% or less.

  If the content of the near-infrared absorbing dye is too small, the layer must be thickened in order to give the near-infrared absorbing layer the desired near-infrared absorbing ability. Therefore, since the coating amount of the coating liquid for forming the near infrared absorption layer also increases, it is necessary to dry at a high temperature and / or for a long time in order to increase the drying efficiency. As a result, when dried at a high temperature, the deterioration of the pigment and the poor flatness of the transparent substrate are likely to occur, and the productivity deteriorates when the drying takes a long time. On the other hand, if the content of the near-infrared absorbing dye is too large, the interaction between the dyes is likely to occur, and even if the amount of residual solvent in the near-infrared absorbing layer is reduced, the dye is likely to be modified over time. .

  The near-infrared absorbing film of the present invention is characterized in that the variation in color tone in the film TD direction is suppressed and the appearance of the near-infrared absorbing layer is extremely good. From the viewpoint of improving the appearance of the near-infrared absorbing layer, it is important to include a surfactant in the coating solution for forming the layer. Therefore, this surfactant is contained in the near-infrared absorbing layer of the film of the present invention.

  By including a surfactant in the coating solution, the appearance of the near-infrared absorbing layer, in particular, omission caused by fine bubbles contained in the coating solution, dents due to adhesion of foreign matter, repelling in the drying process, etc. Improved. Furthermore, the surfactant exerts an effect of improving the slipperiness of the surface by bleeding on the near-infrared absorbing layer surface by coating and drying of the coating solution. Therefore, even if the surface irregularity is not formed on the surface of the near-infrared absorbing layer or on the side opposite to the layer of the film by adding the above-mentioned particles, the handling property is improved and the near-infrared absorbing film is wound in a roll shape. Can be taken.

  As the surfactant, known surfactants (cationic surfactants, anionic surfactants, nonionic surfactants) can be used, but dyes due to the coexistence of surfactants (near infrared absorbing dyes) Nonionic surfactants that do not have a polar group in the molecule are preferable from the viewpoint of suppressing degradation of silicon, and silicon surfactants or fluorine surfactants are recommended because of their superior surface activity. Is done.

  Silicon-based surfactants include amino silane, acrylic silane, vinyl benzyl silane, vinyl benzilyl amino silane, glycid silane, mercapto silane, dimethyl silane, and other silane compounds; polydimethyl siloxane, polyalkoxy siloxane, hydrodiene modified siloxane, vinyl modified siloxane Siloxanes such as, oxy-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 Compound; and the like.

  Fluorosurfactants include ethylene tetrafluoride; perfluoroalkyl ammonium salt, perfluoroalkyl sulfonic acid amide, sodium perfluoroalkyl sulfonate, perfluoroalkyl potassium salt, perfluoroalkyl carboxylate, perfluoroalkyl sulfone. Perfluoroalkyl compounds such as acid salts, perfluoroalkylethylene oxide adducts, perfluoroalkyltrimethylammonium salts, perfluoroalkylaminosulfonates, perfluoroalkyl phosphates, perfluoroalkylalkyl betaines, perfluoroalkyl halides; Etc.

  In addition, it is preferable that HLB (Hydrophilic-Lyphobic-Balance) of surfactant is 3-12. If the HLB is too low, the surface activity may be insufficient, and the effect of improving the appearance of the near infrared absorption layer may be insufficient. On the other hand, if the HLB is too large, the above-mentioned slipperiness improving effect tends to decrease, and the water absorption of the near-infrared absorbing layer increases, so that the temporal stability of the dye tends to decrease. The HLB is an index indicating a balance between the surfactant, hydrophilicity and lipophilicity. The weakest hydrophilic property is defined as 1, and the strongest hydrophilic property is defined as 40. That is, the higher the HLB, the closer to water solubility, and the lower the HLB, the closer to oil solubility.

  The content of the surfactant in the near-infrared absorbing layer is desirably 0.01% by mass or more and 2% by mass or less. When there is too little content of surfactant, the appearance improvement effect of the near-infrared absorption layer by using surfactant, and the slip improvement effect may become inadequate. On the other hand, when the content of the surfactant is too large, the water absorption of the near infrared absorbing layer increases, so that the stability with time of the near infrared absorbing dye may decrease.

  The coating liquid for forming a near-infrared absorption layer contains a near-infrared absorption pigment | dye, resin, surfactant, and an organic solvent. The organic solvent is used for the purpose of dissolving or dispersing the pigment and the resin and improving the coating property. From the viewpoint of improving coatability, the coating solution is a method in which a pigment and a resin are separately dissolved or dispersed and then mixed, and further diluted with an organic solvent as necessary to adjust the solid content concentration to an appropriate range. It is preferable to produce by.

  Examples of organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, tridecyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl alcohol, and the like; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol , Glycols such as dipropylene glycol, glycerin; 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 ether acetate, ethylene glycol monoether Glycol ethers such as butyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, diethylene glycol monoethyl acetate, diethylene glycol monobutyl acetate; esters such as ethyl acetate, isopropyl acetate and n-butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone , Ketones such as cyclohexanone, cyclopentanone, isophorone, diacetone alcohol; and the like. These organic solvents can be used alone or in admixture of two or more.

  Among the organic solvents, ketones excellent in solubility of the dye are suitable, and the amount of ketones with respect to the total amount of organic solvent contained in the coating solution is preferably 30% by mass or more and 80% by mass or less. Organic solvents other than ketones may be selected in consideration of leveling properties and drying properties of the coating liquid.

  The boiling point of the organic solvent is preferably 100 ° C. or higher and 180 ° C. or lower. When the boiling point of the organic solvent is too low, the solid content concentration of the coating solution easily changes during coating. In particular, when the production of the near-infrared absorbing film takes a long time, the change in the coating amount with time becomes significant, and the color tone of the near-infrared absorbing film may change greatly at the start and end of production. On the other hand, if the boiling point of the organic solvent is too high, the amount of residual solvent in the near-infrared absorbing layer is likely to increase, so the aging stability of the dye tends to deteriorate, especially for long-term storage under high temperature and high humidity (for example, When the temperature is 60 ° C. and the relative humidity is 95% for 500 hours, the transmittance and color tone of the film tend to increase.

  As a method of dissolving or dispersing the near-infrared absorbing dye, resin and surfactant in an organic solvent, methods such as stirring, dispersion and pulverization under heating can be employed. By heating at the time of dissolution, the solubility of the pigment and the resin can be increased, and appearance defects due to undissolved materials can be prevented. Also, a near-infrared absorbing layer with excellent transparency can be formed by dispersing or crushing resins and pigments in an organic solvent and dispersing them in the coating solution in the form of fine particles having an average particle size of 0.3 μm or less, for example. It becomes possible to do. A well-known thing can be used as a disperser or a disintegrator. Specific examples include a ball mill, a sand mill, an attritor, a roll mill, an agitator, a colloid mill, an ultrasonic homogenizer, a homomixer, a pearl mill, a wet jet mill, a paint shaker, a butterfly mixer, a planetary mixer, and a Henschel mixer.

  In addition, when a near-infrared absorption layer is formed using a coating solution containing foreign matter or undissolved matter (collectively referred to as “foreign matter”) having a size of 1 μm or more, a dent or the like is generated around the foreign matter. The appearance may be deteriorated, such as a defect of 100 to 1000 μm size. Therefore, it is preferable to remove foreign matters in the coating solution by filtering with a filter or the like prior to coating. Various types of filters can be suitably used, but it is particularly preferable to use a filter that can remove 99% or more of foreign matters having a size of 1 μm or more.

  The solid content concentration in the coating solution (including near infrared absorbing dye, resin, and surfactant) is preferably 10% by mass or more and 30% by mass or less. More preferably, it is 12 mass% or more and 25 mass% or less. If the solid content concentration of the coating solution is too low, the amount of organic solvent in the coating solution increases, so drying during the formation of the near-infrared absorbing layer takes a long time and productivity deteriorates. The residual solvent amount of the dye increases and the aging stability of the dye tends to deteriorate. Especially when stored for a long time under high temperature and high humidity (for example, 60 ° C., relative humidity 95%, 500 hours), the transmittance of the film There is a tendency for changes in color tone to increase. On the other hand, when the solid content concentration of the coating solution is too high, the viscosity of the coating solution becomes large and the leveling property may be insufficient, resulting in a poor appearance of the near infrared absorption layer.

  Incidentally, the viscosity of the coating solution is preferably adjusted to 10 cps or more and 300 cps or less from the viewpoint of improving the appearance of the near infrared absorption layer. In order to adjust the viscosity of the coating solution within the above range, the solid content concentration may be adjusted or an organic solvent having a low viscosity may be used. The viscosity of the coating solution is a value measured with a B-type viscometer.

  For example, when a color tone correction function is required when the film of the present invention is used in a plasma display filter, the near-infrared absorption layer has a specific wavelength in the visible light region (absorption is required for color tone correction). An embodiment containing a dye having a maximum absorption at the same wavelength) is also preferable. On the other hand, from the viewpoint of increasing the transmittance in the visible light region, an embodiment in which the near-infrared absorbing layer according to the present invention does not contain a dye having maximum absorption in the visible light region is also preferable.

<Method for producing near-infrared absorbing film>
To produce a near-infrared absorbing film, for example, a step of continuously applying the coating liquid containing a near-infrared absorbing dye, a resin, a surfactant and an organic solvent on a transparent substrate, and continuous drying By the process of performing, the method of forming a near-infrared absorption layer continuously on a transparent base material is employable. At this time, the coating liquid is applied by a kiss coating method, and the tension in the MD direction at the coating portion of the transparent substrate is 0.5 N / mm ² or more and 1.2 N / mm ² or less (more preferably 1.0 N / mm ² or less). ), A film in which the variation in color tone in the TD direction is suppressed, that is, a film in which the maximum value of the color difference Δ in the TD direction obtained by the measurement method (A) is controlled to be equal to or less than the upper limit value is obtained. be able to.

  In the kiss coat method, only one side (application surface) of the transparent substrate is in contact with the application roll for applying the coating liquid, and the other surface is in a free state (a state in which nothing is in contact). is there. When the coating liquid is applied, the surface opposite to the coating surface of the transparent base material comes into contact with the roll or the like, so that foreign matter adheres to the roll surface or micro protrusions on the roll surface are formed. In this case, the appearance of the near-infrared absorbing layer may be affected, but if the kiss coat method is adopted, such an influence can be avoided, so that the appearance of the near-infrared absorbing layer can be made more uniform. .

  In order to stably apply the coating liquid on the transparent substrate by using the kiss coating method, rolls are installed before and after the coating portion of the transparent substrate, and tension is applied in the MD direction of the transparent substrate. However, since the coating liquid can be applied uniformly in the TD direction of the transparent substrate by controlling the tension at this time within the above range, the variation in color tone in the film TD direction is highly suppressed. The If the tension is too low, the running property of the transparent base material becomes poor, and meandering is likely to occur, the uniformity of coating of the coating liquid is impaired across the film TD direction, and color tone fluctuations occur in the film TD direction. It becomes easy. On the other hand, if the tension is too high, the transparent base material moves closer to the center of the roll (the roll before and after the coating part), and a tin-like wave is generated in parallel with the running direction (MD direction). In the direction, the uniformity of the contact between the kiss roll (coating roll) and the transparent substrate is impaired, so that the variation of the color tone in the film TD direction may be increased.

  The tension in the MD direction in the application part of the transparent substrate can be controlled by adjusting the balance of the rotation speeds of the rolls installed before and after the application part. The tension during film travel can be measured, for example, by a general method of measuring the load on the roll with a load cell.

  In addition, when manufacturing the film, after the drying step, the film color tone and / or light transmittance at a specific wavelength is measured online, and the coating conditions and / or drying conditions of the coating liquid are adjusted according to the measurement results. By doing so, a film in which variation in color tone is suppressed over the film MD direction, that is, a film in which the maximum value of the color difference Δ in the MD direction obtained by the measurement method (A) is controlled to be equal to or less than the lower limit value is obtained. be able to.

  Examples of coating conditions include adjusting the coating amount of the coating solution. Since the coating amount of the coating solution affects the L value of the film, for example, the color tone of the film being manufactured is monitored online as needed, and when the L value is high, the coating amount of the coating solution is increased. When the L value is low, the amount of coating liquid is changed so as to decrease. If the change of the color tone (L value) after the change is settled, the film production is continued with the applied amount, and if not, the applied amount is changed again.

  The coating amount of the coating liquid is, for example, the ratio of the rotation speed G of the gravure roll to the traveling speed F of the film, and the contact of the doctor blade to the gravure roll when the coating is performed by a reverse gravure / kiss coating apparatus described later. It can be adjusted by changing the pressure and contact angle. That is, in order to increase the coating amount, the G / F is increased, the contact pressure of the doctor blade is decreased, and the contact angle is decreased. In order to reduce the coating amount, the G / F may be decreased, the contact pressure of the doctor blade may be increased, and the contact angle may be increased. The adjustment of the coating amount of the coating solution may be performed by changing any one of the conditions, or may be performed by changing a plurality of conditions.

  Moreover, adjusting drying efficiency is mentioned as drying conditions. When the drying efficiency changes, the a and b values of the film are affected. For example, the color tone of the film being manufactured is monitored online as needed, and if the a or b value changes, the drying efficiency Make adjustments. As a method for adjusting the drying efficiency, the film running speed (drying time), the temperature of the drying wind, and the air volume (wind speed) may be controlled. That is, for further drying, it is only necessary to control the direction in which the film traveling speed is lowered, the temperature of the drying air is increased, and the air volume is increased. On the other hand, in order to further reduce the degree of drying, it is only necessary to increase the film traveling speed, lower the temperature of the drying air, and control the air volume to decrease. The adjustment of the drying efficiency may be performed by changing any one of the conditions, or may be performed by changing a plurality of conditions. For example, when the a value is high and / or the b value is low, the drying efficiency may be adjusted. On the other hand, when the a value is low and / or the b value is high, the drying efficiency is adjusted. Adjust to drop.

  In addition, the color tone measurement at the time of film manufacture can employ | adopt the same method as the color tone measurement for color difference (DELTA) calculation of a film.

  In addition, when the film production is managed with the light transmittance of a specific wavelength, the light transmittance of the specific wavelength is monitored online as needed, and if there is a change in the transmittance, this is stabilized. Thus, what is necessary is just to control a coating condition and / or a drying condition. For example, if the light transmittance changes in the direction of increasing, it may be changed in the direction of increasing the coating amount of the coating liquid, and if the light transmittance is changed in the direction of decreasing, it is applied. What is necessary is just to change to the direction which reduces the application quantity of a liquid. As the method for adjusting the coating amount of the coating liquid and the drying efficiency, the method described for the case where the color tone is monitored online can be adopted.

  For the light transmittance of a specific wavelength, for example, using a spectrophotometer (such as “MCPD-3000” manufactured by Otsuka Electronics Co., Ltd.), irradiate light of a specific wavelength from the near infrared absorption layer side, and refer to the transmittance of indoor air. It can be measured as a value (blank).

  As a method for applying the coating liquid on the transparent substrate, a kiss coating method and a gravure coating method (that is, a gravure / kiss coating method) are preferable, and in particular, coating from a liquid supply pan with a reverse rotating gravure roll. A “reverse gravure kiss coating method” coating method in which the liquid is scraped off and excess coating liquid is scraped off by a doctor blade is preferable. FIG. 1 shows an apparatus employing a reverse gravure / kiss coat system. By adopting such a gravure / kiss coat method, in particular, a reverse gravure / kiss coat method, more uniform coating becomes possible. Note that the near infrared absorption layer is essentially a continuous layer. Therefore, the near-infrared absorbing layer is a continuous layer also by the gravure coating method.

  In the reverse gravure / kiss coat apparatus, it is preferable to use a gravure roll having a diameter of 80 mm or less. When the diameter is large, wrinkles are likely to occur in the running direction of the film. As the doctor blade used in the reverse gravure coating apparatus, a known one can be used, but at least the surface [at least the cutting edge in contact with the gravure roll (coating liquid on the gravure roll)] is made of ceramics and is hardly worn. Recommended because it is easy to stabilize the coating amount of the coating solution. Of course, it is also preferable that the entire doctor blade is made of ceramics. In addition, for example, a doctor blade obtained by plating nickel on the surface of Swedish steel is suitable because it is inferior to a ceramic doctor blade but hardly wears.

  In the reverse gravure / kiss coat apparatus, the elements for controlling the coating amount include, as described above, the rotation speed of the gravure roll with respect to the running speed of the film, the angle with which the doctor blade is brought into contact, and the pressing pressure of the doctor blade. In order to increase the coating amount, it is preferable to increase the rotation speed of the gravure roll. Gravure transfer and coating defects can be controlled by controlling the speed ratio G / F of the rotational speed G (m / min) of the gravure roll to the running speed F (m / min) of the film to 0.8 to 1.5. And from the viewpoint of stability over time of the coating amount. It is more preferable to control the speed ratio G / F to 0.9 or more and 1.2 or less. When the speed ratio G / F is too small, the transfer amount is reduced, and the gravure is easily left without being leveled. On the other hand, if the speed ratio G / F is too large, coat defects such as horizontal spots and bubble streaks are likely to occur, the doctor blade tends to be worn, and the coating amount tends to be unstable over time. Yes, it becomes difficult to control the kiss part (adjustment of the doctor blade, the parallelism in the TD direction of the substrate, the kiss length in the TD direction, etc.). The rotation speed F (m / min) of the rotogravure roll is obtained by multiplying the rotation speed (rotation speed / min: rpm) of the gravure roll by the circumference of the gravure roll [circumference ratio × roll diameter (mm)]. It can be calculated by converting to m / min.

  The angle at which the doctor blade is brought into contact with the coating solution on the gravure roll is preferably 20 to 70 ° in terms of internal angle. If the angle is too small (situation where the gravure roll is held by the antinode of the doctor blade), the scraping power of the coating liquid on the surface of the gravure roll will decrease and the coating amount will increase, and the wear of the doctor blade will not easily occur. However, vibration and the like are likely to occur in the doctor blade, and the appearance of the near-infrared absorbing layer is likely to deteriorate. On the other hand, when the angle is large (the situation where the doctor blade is pierced into the gravure roll), the scraping power of the coating liquid on the surface of the gravure roll is improved, the coating amount is reduced, and the vibration of the doctor blade is less likely to occur. The problem of being easily worn occurs.

  It is preferable that the contact pressure of the doctor blade is adjusted to such an extent that the blade is slightly reduced because the coating amount in the film width direction can be made uniform.

The coating amount of the coating solution is not particularly limited, but the amount after drying is 1 g / m ² or more, more preferably 3 g / m ² or more, and 50 g / m ² or less, more preferably 30 g / m ² or less. It is recommended that If the coating amount is too small, the near infrared absorption ability may be insufficient. Therefore, it is necessary to increase the density per unit area in plan view of the near infrared absorption layer and adjust the near infrared absorption ability to a target level. In this case, the distance between the dyes is shortened. As a result, the deterioration of the dye tends to occur, and the stability with time tends to decrease.

  On the other hand, if the coating amount is too large, the near-infrared absorption ability will be sufficient, but the transmittance in the visible light range will decrease and the transparency will tend to decrease, so such a near-infrared absorption film is applied. In such a plasma display, the luminance may decrease. In order to avoid this, it is conceivable to increase the transmittance in the visible light range by reducing the dye concentration in plan view of the near infrared absorbing layer and increasing the distance between the dyes. The thickness of the near-infrared absorbing layer must be increased, and drying after application of the coating liquid tends to be insufficient. As a result, the amount of residual solvent in the near-infrared absorbing layer increases, the stability of the dye over time deteriorates, especially when stored for a long time under high temperature and high humidity (for example, 60 ° C., relative humidity 95%, 500 hours). In addition, the transmittance and color tone of the film tend to increase. On the other hand, if the drying conditions are severe, for example, by raising the temperature during drying or lengthening the time, for example, a heat-sensitive dye (such as a diimmonium salt compound) is not only easily denatured but also a transparent base caused by heat. The flatness of the material is likely to occur.

  For drying after the coating liquid is applied, a known drying method such as hot air drying or drying with an infrared heater can be adopted, but hot air drying with a high drying speed is preferable.

  Furthermore, it is recommended that the drying process includes the following first drying process, second drying process, and cooling process.

  The first drying step is an initial constant rate drying step after coating. In this step, drying is preferably performed using wind at a temperature of 20 ° C. to 80 ° C. and a wind speed of 2 m / second to 30 m / second. If the initial drying conditions are strict (the temperature of the wind is increased and the amount of air is increased), minute defects such as minute coating omission, minute repellency, and cracks derived from the foam contained in the coating liquid will occur in the near infrared. It tends to occur in the absorption layer. On the other hand, if the initial drying conditions are sweet (the temperature of the wind is low and the amount of air is reduced), the near-infrared absorbing layer has a good appearance, but it takes a long time to dry and the productivity deteriorates. Problems arise. In addition, it is preferable that the drying time (passage time of a film) in a 1st drying process shall be 10-120 seconds, for example.

  The second drying process is a reduction drying process after the first drying process. In this step, the temperature is higher than that in the first drying step, and the solvent in the near-infrared absorbing layer is reduced. Specifically, it is preferable to dry with a temperature of 120 ° C. or more and 180 ° C. or less. If the temperature of the wind is too low, the amount of solvent in the near-infrared absorbing layer is difficult to decrease. On the other hand, if the temperature of the wind is too high, thermal wrinkles are generated on the transparent substrate, and flatness is likely to be poor, and thermal degradation of the near infrared absorbing dye tends to occur. The drying time (film transit time) is preferably 5 seconds or more and 180 seconds or less. When the drying time is short, the residual solvent in the near infrared absorption layer tends to increase. On the other hand, when the drying time is long, productivity is lowered and thermal wrinkles are easily generated on the transparent base material, which tends to cause poor flatness. In addition, it is recommended that the wind speed in a 2nd drying process shall be 2-50 m / sec, for example.

  The cooling process is the final process of the drying process. In this step, it is preferable to cool with a wind having a temperature equal to or lower than the Tg of the resin (resin in the near-infrared absorbing layer), and to set the temperature of the transparent substrate to be equal to or lower than the Tg of the resin in a flat state. The temperature of the wind is more preferably Tg-5 ° C or lower, and further preferably Tg-10 ° C or lower. When the film leaves the drying furnace at a high temperature, the near-infrared absorbing layer surface becomes slippery when it comes into contact with the roll for film running before winding, and the layer surface is scratched. In addition to this, the film may be curled. In the cooling step, the wind speed is preferably set to 2 to 50 m / second, for example, and the cooling time is preferably set to 5 to 120 seconds, for example.

  In the drying step, it is preferable to control the drying state so as to be stable over the entire length of the film. If the dry state fluctuates, for example, the color tone may fluctuate in the film MD direction because the dye is likely to deteriorate at a location where the amount of residual solvent in the near-infrared absorbing layer is large. In particular, at the initial stage of coating, the amount of the evaporated solvent in the drying furnace increases and the amount gradually becomes stable, so that the drying efficiency is likely to change until about 500 m from the start of coating. In order to stabilize the drying efficiency, it can be controlled by adjusting the drying temperature, the volume of wind (hot air) (wind speed), the drying time, and the like.

  The drying temperature is preferably controlled within a range of, for example, ± 2 ° C. with respect to the set temperature. The temperature is accurately controlled and, for example, 30 minutes after the actual temperature in the drying furnace reaches the set temperature. It is preferable to perform film production after allowing the drying temperature to stabilize as described above. In order to accurately control the temperature and the amount of wind, a highly accurate heater or blower may be used, and for the drying time, a highly accurate drive device may be used.

  The near-infrared absorbing film obtained by the above production method is usually wound around a take-up core (core such as a paper tube or a metal tube) and stored and transported as a roll (that is, a near-infrared absorbing film roll). .

<Other properties of near-infrared absorbing film>
The near-infrared absorbing film of the present invention is a film having low transmittance in the near-infrared region of wavelength: 800 to 1200 nm and high transmittance in the visible light region (400 to 800 nm).

  The transmittance in the near infrared region is preferably as low as possible, for example, preferably 40% or less, more preferably 30% or less. If the transmittance in the near-infrared region is too high, when used in a plasma display filter, the absorption of near-infrared light emitted from the plasma display will be insufficient, and malfunction of electronic equipment using a near-infrared remote control can be sufficiently prevented. It may disappear.

  On the other hand, the transmittance in the visible light region other than the wavelength: 550 to 650 nm is preferably as high as possible, preferably 50% or more, and more preferably 60% or more. When the transmittance in these wavelength ranges is too low, the transparency is lowered, and therefore, when used in a plasma display filter, the brightness of the display is likely to be lowered.

  Thus, as a design method for selectively absorbing light at a specific wavelength, for example, two or more near-infrared absorbing dyes can be appropriately blended. Moreover, the adjustment of the light transmittance at these specific wavelengths can be achieved by appropriately changing the concentration of the near-infrared absorbing dye per unit area in a plan view of the near-infrared absorbing layer.

  As the appearance of the near-infrared absorbing layer, it is desirable that there is no defect having a diameter of 300 μm or more, more preferably 100 μm or more. The defect of the above size becomes a bright spot when installed in front of the plasma display, and the frequency of being recognized as an optical defect becomes remarkable. Also, streaks and spots with a thin near-infrared absorbing layer become prominent on the front surface of the display and are regarded as defects. Generation | occurrence | production of these external appearance defects can be prevented by employ | adopting the above-mentioned manufacturing method.

  It is preferable that the light transmittance of each wavelength region (near infrared region, visible light region) does not change even when the near infrared absorbing film is left for a long time under high temperature and high humidity. If the stability over time under high temperature and high humidity is poor, when used for a filter for plasma display, it will not only change the color tone of the image on the display but also cause malfunction of electronic equipment using near infrared remote control. In some cases, the effect of the present invention, which is to prevent, cannot be sufficiently secured.

  In order to improve the temporal stability of the light transmittance, as described above in the description of the production method, the residual in the near-infrared absorbing layer can be adjusted by adjusting the type of solvent used in the coating solution, the thickness of the coating layer, and the drying conditions. This can be achieved by reducing the amount of the solvent or adjusting the dye concentration per unit area in plan view of the near infrared absorption layer. The amount of residual solvent in the near-infrared absorbing layer (the amount of residual solvent derived from the coating solution) is preferably as small as possible. For example, it is preferably 3% by mass or less in the total amount of the near-infrared absorbing layer. If the residual solvent is 3% by mass or less, there will be no substantial difference in stability over time. On the other hand, if the drying conditions are excessively strict for the purpose of further reducing the amount of residual solvent, adverse effects such as poor flatness of the film may occur.

  In the near-infrared absorbing film of the present invention, the width (length in the TD direction) and the length (length in the MD direction) are not particularly limited. For example, the width is preferably 0.5 m or more, and 1 m or more. It is more preferable that A film having a width less than the above lower limit generally has less color tone fluctuation in the width direction (TD direction), and thus the effect of the present invention is hardly exhibited, and is industrially low in utility value. The length is preferably 100 m or more, and more preferably 300 m or more.

<Near infrared absorption filter>
The near-infrared absorption film of this invention comprises the near-infrared absorption filter suitable for a plasma display use with another component. Other components include various functional layers that are used as components of conventional plasma display filters, such as electromagnetic shielding layers, antireflection layers, and glare prevention layers. These layers absorb near infrared rays. In general, the film is laminated directly or via an adhesive layer on the surface of the near-infrared absorbing layer of the film or on the opposite side. The pressure-sensitive adhesive used in the pressure-sensitive adhesive layer is a conventionally known pressure-sensitive adhesive that does not impair the function of the near-infrared absorption filter of the present invention (for example, the transparency is impaired or the ability to absorb light of a specific wavelength is impaired. Do not do).

  Examples of the electromagnetic wave shielding layer include a metal mesh or a transparent conductive thin film. As the metal mesh, one having a metal mesh conductive layer having an aperture ratio of 50% or more is suitable. When the aperture ratio is small, the electromagnetic wave shielding property is good, but the light transmittance tends to decrease. Specific examples of metal mesh include metal foil with high electrical conductivity etched into a mesh, metal fiber woven or knitted, and metal fiber plated on the surface of polymer fiber. And those composed of fibers attached by a technique such as The metal used for the metal mesh is not particularly limited as long as it has good electrical conductivity and no problem with stability, but copper, nickel, tungsten and the like are preferable from the viewpoint of workability and cost.

  In the case of an electromagnetic wave shielding layer composed of a transparent conductive thin film, a known transparent conductive material (metal oxide) can be applied as the constituent material. In order to further increase the conductivity of the transparent conductive thin film, a multilayer film having a structure in which three or more metal oxide layers and metal layers are alternately laminated, such as metal oxide layer / metal layer / metal oxide layer, is used. Is preferred. By setting it as such a structure, electroconductivity can be improved, maintaining the visible light transmittance of a transparent conductive thin film high. The type of the metal oxide is not particularly limited as long as the desired values of conductivity and visible light transmittance can be satisfied. Specific examples include tin oxide, indium oxide, indium tin oxide, zinc oxide, titanium oxide, and bismuth oxide. In addition, the metal used for the metal layer in the case of a multilayer structure is preferably gold, silver, or a compound containing these from the viewpoint of improving conductivity.

  When the transparent conductive thin film is a multilayer film and has a three-layer structure of metal oxide layer / metal layer / metal oxide layer, for example, the thickness of the metal layer (for example, silver layer) is 50 to 200 mm (more preferably 100 mm). Or less). When the metal layer is thicker than this, the light transmittance is lowered, and when it is thin, the resistance value is increased. The thickness of the metal oxide layer is preferably 100 to 1000 mm (more preferably 500 mm or less). If the metal oxide layer is too thick, the color tone of the filter may change due to coloring, and if it is thin, the effect of reducing the resistance value may be insufficient.

  Further, in the case of five layers such as metal oxide layer / metal layer / metal oxide layer / metal layer / metal oxide layer, the central metal oxide layer is thicker than the metal oxide layers at both ends. It is desirable to do. By setting it as such a structure, the light transmittance of the whole multilayer film improves.

  In the near-infrared absorbing film and the near-infrared absorbing filter of the present invention, for the purpose of suppressing deterioration of the dye due to light with time, a layer having an ultraviolet absorbing ability is provided, or any layer is provided with an ultraviolet absorbing ability. The light resistance may be improved. In order to ensure the ultraviolet absorbing ability, for example, a near infrared absorbing layer, a transparent substrate, a pressure-sensitive adhesive layer, an antireflection layer, an antiglare layer, etc. may contain an ultraviolet absorber, It is particularly preferable to include an ultraviolet absorber in the substrate. Since layers other than the transparent substrate are generally thinner than the transparent substrate, it is necessary to increase the amount of the UV absorber in the layer in order to ensure sufficient UV absorbing ability. As a result, the function of each layer may be impaired. As the ultraviolet absorber, a known organic or inorganic ultraviolet absorber can be used.

  As an embodiment of the near-infrared absorbing filter of the present invention, as a near-infrared absorbing film, an ultraviolet absorber is added to a transparent substrate to impart an ultraviolet absorbing ability, and adhere to other functional layers (such as an antireflection layer). It is most suitable to laminate without an agent layer and cut according to the size of the plasma display. For example, when it has an antireflection layer, the layer is on the opposite side (outermost surface side) from the display. It is recommended to use it by arranging it so that it is directly attached to the display via an adhesive layer.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. In addition, the evaluation method employ | adopted by the present Example is as follows.

(1) Light transmittance Using a spectrophotometer ("U-3500 type" manufactured by Hitachi, Ltd.), in the range of wavelength: 1100 to 200 nm, light of a specific wavelength is irradiated from the near infrared absorption layer side, and the indoor air The transmittance is measured as a reference value (blank). The transmittance in the near-infrared region is evaluated by the average value of the transmittance at a wavelength of 900 to 110 nm, and the transmittance in the visible light region is evaluated by an average value of the transmittance at a wavelength of 450 to 700 nm.

(2) Color tone Color tone is measured by using a color difference meter (“ZE-2000” manufactured by Nippon Denshoku Industries Co., Ltd.), using standard light as a D65 light source, viewing angle of 10 degrees, and irradiating the near infrared absorption layer side with light. The L value, a value, and b value of the Lab display system are obtained.

(3) Color difference Δ
Regarding the TD direction of the film obtained in each of Examples and Comparative Examples described later, one end is determined as the first end, the other end is determined as the second end, and the both ends are used as measurement points. Between the both ends, three measurement points are provided at equal intervals, and the color difference Δ defined in the above formula (1) is calculated from the L value, the a value, and the b value measured according to the color tone measurement method for each measurement point. It calculates about each measurement location and makes the largest value among these the largest value of the color difference (DELTA) of film TD direction.

(4) Near-infrared absorption layer appearance A near-infrared absorption film is placed on a white film, the near-infrared absorption layer surface is visually observed under a three-wavelength fluorescent lamp, and evaluated according to the following criteria.
◎: Appearance defects are not observed even when observing while moving the near-infrared absorbing film.
○: When observing while moving the near-infrared absorbing film, there are some appearance defects.
△: When the near-infrared absorbing film is moved, the appearance defect is clearly seen.
×: Appearance defects are clearly seen even when observed in a stationary state.

<Preparation of transparent substrate>
An inherent viscosity of 0.62 dl / g and PET resin containing no particles are put into a twin screw extruder, melt extruded at 290 ° C. from a T-die, and in close contact with electrostatic application on a cooled rotating metal roll. Solidified to obtain an unstretched film. Next, this unstretched film was heated to 90 ° C. with a roll stretching machine and longitudinally stretched (longitudinal direction) 3.5 times. Thereafter, the coating solution for anchor coat having the composition shown in Table 1 was applied to the film. Then, it was applied so that the coating amount after drying was 0.5 g / m ^2, and passed through hot air at a wind speed of 10 m / second and a temperature of 120 ° C. in 20 seconds to form an anchor layer. Furthermore, after heating to 140 ° C. with a tenter and stretching 3.7 times in the width direction, heat treatment was performed while relaxing 5% in the width direction at 235 ° C., and a transparent substrate (biaxial stretching with an anchor layer on both sides) PET film) was obtained. The obtained transparent substrate had a thickness of 100 μm, a total light transmittance of 90.2%, and a haze of 0.5%. The total light transmittance and haze are values measured by a method defined in JIS K 7136. About the TD direction of the obtained film, it slit by 1.3 m width from the center part, and used it for preparation of a near-infrared absorption film.

<Preparation of coating solution for forming near-infrared absorbing layer>
Each component was mixed with the composition shown in Table 2, the dye and the resin were dissolved under heating (40 ° C.), and the undissolved material was removed using a film having a nominal filtration accuracy of 1 μm to obtain a coating solution. . The solid content concentration of the coating solution was 17% by mass, and the viscosity (viscosity obtained by the above-described measurement method) was 40 cps.

Example 1
The near-infrared absorbing layer forming coating solution was applied to the transparent substrate using a reverse gravure / kiss coater. The application roll of the apparatus is a diagonal gravure roll (diameter: 60 cm, number of lines: 45 lines / 2.54 cm, depth: 290 μm, cell volume: 139 cm ³ / m ² ), and a ceramic doctor blade is in contact therewith Then, the gravure roll was applied by reverse rotation. The running speed F of the transparent substrate is 20 m / min, the rotation speed of the gravure roll is 18 m / min (speed ratio G / F is 0.9), the kiss length is 10 mm, and the tension in the MD direction at the coated portion of the transparent substrate. Was 0.7 N / mm ² .

  After coating the coating solution, it is guided to a drying furnace and passed through the wind at a speed of 5 m / sec at 40 ° C. in 20 seconds (the first drying step), and then in the wind at a speed of 20 m / sec at 150 ° C. It was allowed to pass for 20 seconds (second drying step), and further passed through a wind of 20 m / second at 90 ° C. for 10 seconds (cooling step) to be dried. In this way, a near-infrared absorbing film having a TD direction of 1.275 m was obtained. Table 3 shows the evaluation results of this near-infrared absorbing film.

Example 2
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the tension in the MD direction in the coated portion of the transparent substrate was changed to 1.0 N / mm ² . Table 3 shows the evaluation results of this near-infrared absorbing film.

Example 3
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the tension in the MD direction in the coated part of the transparent substrate was changed to 1.2 N / mm ² . Table 3 shows the evaluation results of this near-infrared absorbing film.

Example 4
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the tension in the MD direction in the coated portion of the transparent substrate was changed to 0.5 N / mm ² . Table 3 shows the evaluation results of this near-infrared absorbing film.

Example 5
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the material of the doctor blade was changed to Swedish steel. Table 3 shows the evaluation results of this near-infrared absorbing film.

Example 6
Example 1 In the coating solution for forming a near-infrared absorbing layer, except that cyclopentanone and toluene were increased in equal amounts so that the solid content concentration was 15% by mass, and the speed ratio G / F was changed to 1.6, Example 1 In the same manner as above, a near-infrared absorbing film was obtained. Table 3 shows the evaluation results of this near-infrared absorbing film.

Example 7
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the contact angle of the doctor blade was 75 degrees and the speed ratio G / F was changed to 0.8. Table 3 shows the evaluation results of this near-infrared absorbing film.

Comparative Example 1
A near-infrared absorbing film was obtained in the same manner as in Example 1 except that the tension in the MD direction in the coated portion of the transparent substrate was changed to 1.4 N / mm ² . Table 3 shows the evaluation results of this near-infrared absorbing film.

Comparative Example 2
A near-infrared absorbing film was produced in the same manner as in Example 1, except that the MD direction tension in the coating part of the transparent base material was changed to 0.3 N / mm ^2. The material meandered and the near-infrared absorbing film could not be wound up well. Therefore, the film is not evaluated.

  As can be seen from Table 3, the near-infrared absorbing films of Examples 1 to 7 have low transmittance in the near-infrared region and high transmittance in the visible light region. Furthermore, the maximum value of the color difference Δ in the film TD direction is small, and the variation of the color tone in the film TD direction is suppressed. The appearance of the near infrared absorbing layer is also very good.

  On the other hand, in the near-infrared absorbing film of Comparative Example 1, several strip-like streaks occurred in the MD direction at the center in the TD direction, and the variation in the color tone in the TD direction also increased.

It is a schematic diagram of the reverse gravure kiss coat type coating apparatus used in the examples of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent base material before application liquid application 2 Gravure roll 3 Liquid supply pan 4 Doctor blade 5 Transparent base material after application liquid application

Claims (7)

A near-infrared absorbing film comprising a near-infrared absorbing layer and a transparent substrate as constituent elements,
The near infrared absorbing layer contains a near infrared absorbing pigment, a resin and a surfactant,
The near-infrared absorbing film according to claim 1, wherein the maximum value of the color difference Δ in the TD direction obtained by the following measurement method (A) is 1.0 or less.
(A) In measuring the color tone of the film, when one end in the TD direction of the film is a first end and the other end is a second end, 1 is measured within 0.1 m from the first end. The second measurement is performed at a location within 0.1 m inside from the second end, and at three locations at approximately equal intervals between the first measurement location and the final measurement location. At five measurement points, a color difference Δ defined by the following equation is calculated.
ΔE = [(L _a −L _m ) ² + (a _a −a _m ) ² + (b _a −b _m ) ² ] ^1/2
Here, L _m, a _m, b _m means a color L, a, b in each measurement _{point, L a, a a, b} a , the color L, a, the average value of b in all measurement points Means.   The near-infrared absorbing film according to claim 1, wherein the near-infrared absorbing dye contains a diimmonium salt compound.   The near-infrared absorption filter characterized by including the near-infrared absorption film of Claim 1 or 2 in a component. A method for producing a near-infrared absorbing film, wherein a coating solution containing a near-infrared absorbing dye, a resin, a surfactant, and an organic solvent is continuously applied on a transparent substrate and dried to form a near-infrared absorbing layer. ,
An application of the coating liquid is performed by a kiss coating method, and the tension in the MD direction in the coating portion of the transparent base material is controlled to 0.5 N / mm ² or more and 1.2 N / mm ² or less. Production method. Application of the coating liquid is performed with a gravure kiss coat apparatus having a gravure roll,
The manufacturing method according to claim 4, wherein a speed ratio G / F of a rotational speed G (m / min) of the gravure roll to a running speed F (m / min) of the film is set to 0.8 to 1.5.   The gravure / kiss coat apparatus has a mechanism for scooping up the coating liquid from the liquid supply pan with a reverse rotating gravure roll and scraping off the excess coating liquid with a doctor blade, and at least the part of the doctor blade that contacts the gravure roll The manufacturing method according to claim 5, wherein an apparatus made of ceramics or nickel is used. The manufacturing method according to any one of claims 4 to 6, wherein the drying step after applying the coating liquid includes the following first drying step, second drying step, and cooling step.
1st drying process: It dries with the wind whose temperature is 20-80 degreeC, and a wind speed is 2-30 m / sec;
Second drying step: drying at a temperature of 120 to 180 ° C. for 5 to 180 seconds;
Cooling step: By the temperature below the glass transition temperature of the resin constituting the near infrared absorption layer
Cooling.

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