JP2004351291A - Coating method and coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method which realizes an in-plane uniformity with a desired degree of precision in an optical film or the like in a method for coating a supporting body with a coating liquid using a die, and to provide a method for preparing an irregularity-free coating film and a coating film obtained by the method, and to provide an optical film laminated by the coating film and an image display device applying the optical film. <P>SOLUTION: The coating liquid is fed to the die while controlling the liquid surface of the coating liquid in a coating liquid tank 3 without using a feed device in a section from the coating liquid tank 3 to the die 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coating method capable of forming a coating film excellent in surface smoothness and free from defects such as streaks by continuously applying a coating solution on a continuously transported support using a die. Things. Further, the present invention relates to a coating film using the coating method or an optical film using the coating film as an optical layer, and an image display device using the optical film.
[0002]
[Prior art]
Conventionally, when producing an optical film or various resin sheets, as a method of applying a coating solution to a support, a gravure roll coating method, a reverse roll coating method, a dip coating method, a blade coating method, an air knife coating method, The wire block coating method, reblocking coating method, reblocking roll coating method, extrusion coating method, rod coating method, wire bar coating method, slide coating method, curtain coating method, and the like are known. For the production of optical films and the like which are not susceptible to deterioration and contamination of foreign substances and unevenness in the thickness of the coating film surface, a coating method using an extrusion coating method (extrusion method) capable of uniformly coating the surface of the support with a closed system is preferable. Used.
[0003]
Conventionally, the application method by the extrusion method uses a supply device such as a pump or a piston or a capillary phenomenon to supply a coating liquid into a die, and continuously supplies the coating liquid through a wide slit (discharge port) provided at the tip of the die. The coating liquid continuously extruded toward the surface of the support to be conveyed is applied to the surface of the support with a uniform thickness (for example, see Patent Document 1).
[0004]
However, it has been found that when the above-described supply device is used as a method of supplying the coating liquid, pulsation occurs in the coating liquid to a considerable extent, which causes uneven coating. To cope with such a problem, a coating apparatus that eliminates coating unevenness by providing a vibration isolator (pulsation removing apparatus) has been proposed (for example, see Patent Document 2).
[0005]
However, even with a method using a device such as an anti-vibration device, coating unevenness has not been completely removed, and in particular, in recent years, in addition to the demand for thinner and larger coating films, more precise in-plane It was insufficient for an optical film or the like requiring uniformity.
[0006]<Conventional publication>
[Patent Document 1]
JP-A-2002-86041
[0007]
[Patent Document 2]
JP-A-5-31434
[0008]
[Problems to be solved by the invention]
Therefore, in the present invention, in a method of applying a coating liquid using a die on a support, there is obtained a coating film which does not have coating unevenness and can realize a precise in-plane uniformity required for an optical film or the like. An object of the present invention is to provide a coating method to be obtained, a coating film obtained by the coating method, an optical film having the coating film laminated thereon, and an image display device using the optical film.
[0009]
[Means for Solving the Problems]
Means for Solving the Problems The present inventors have conducted intensive studies in order to study the above problems, and have found that the above object can be achieved by using the coating apparatus described below, and have completed the present invention.
[0010]
The present invention provides a method of supplying a coating liquid to a die from a coating liquid tank and applying the coating liquid on a support using the die without using a supply device in a section from the coating liquid tank to the die. The present invention relates to a coating method characterized by supplying a coating liquid to a die while controlling the liquid level of the coating liquid in a liquid tank.
[0011]
As a method of controlling the coating liquid level in the coating liquid tank, a sufficient amount of the coating liquid filling the tank is supplied to the coating liquid tank, so that the coating liquid overflows from the coating liquid tank, There is a method of keeping the liquid level of the liquid tank constant.
[0012]
In the coating method of the present invention, it is preferable that at least one vibration isolator is provided in a section from the coating solution tank to the die, and the section is vibrated.
[0013]
Furthermore, the present invention relates to a coating film formed by the above coating method, and relates to an optical film in which the coating film is laminated as an optical layer on a film, and an image display device having the optical film.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
1 shows an example of a coating apparatus used in the coating method of the present invention. For example, as shown in FIG. 1, this coating device includes an inner tank 31 and an outer tank 32 through a supply pipe (1) 5 provided with a liquid supply pump 4. It is supplied to the inner tank 31 of the coating liquid tank 3. The coating liquid tank 3 has a function as a buffer tank by supplying the coating liquid from the storage tank 2 to the inner tank 31 so that the coating liquid overflows from the upper part of the inner tank 31. As a result, the liquid level of the application liquid is always constant, and the supply device is not used in the middle of the supply pipe (2) 6, so that the coating liquid is supplied to the die 1 at the same pressure by its own weight. At this time, the coating liquid overflowing from the inner tank 31 of the coating liquid tank is received by the outer tank 32 and then returned to the storage tank 2 for reuse. Further, in a section from the coating solution tank 3 to the die 1, it is preferable to install a vibration isolator made of a vibration-proof rubber or the like on the installation base, the supply pipe, or the like. As described above, the coating liquid supplied from the supply port 12 of the die is sequentially applied onto the support 8 which is continuously conveyed from the ejection port 11 to form a coating film before drying. The coating film thus formed before drying is subjected to necessary steps such as a drying step and a curing treatment step as required, and becomes a target coating film. After the above-mentioned process, this coating film can be peeled off from the support and recovered.
[0015]
The coating method according to the present invention is used for a coating method in which a coating liquid is sequentially discharged from a die onto a support, and is particularly preferably used for a coating method using an extrusion die by an extrusion method. This extrusion method is a coating method widely used as a high-precision coating method due to the excellent uniformity of the film thickness and the smoothness of the coating film surface, and extrudes the coating liquid from the discharge port at the tip of the die. Is applied to a continuously transported support. The extrusion die has a supply port for supplying the coating liquid, a distribution section (manifold) for holding the supplied coating liquid in the width direction and uniformly supplying the coating liquid, and a supply port for supplying the coating liquid from the distribution section. It has a slit-shaped discharge port for discharging uniformly in the direction. By devising the structure of this die, simultaneous multilayer coating is also possible.
[0016]
The die is made of an appropriate material such as a metal, a plastic, and a ceramic, for example, and the width of the discharge port for determining the coating width can also be appropriately determined according to the required coating film. However, it is necessary to pay close attention to the dimensional accuracy and assembly accuracy of the device, especially for the distance between the tip of the discharge port of the die for discharging the coating liquid and the support that is the object to be coated. Requires high-precision settings. If the distance between the tip of the discharge port and the support is too large, coating becomes impossible, streak-like defects or uneven coating appear on the coated surface, and if too small, the total amount of coating liquid supplied from the die Is not applied, and a liquid pool is generated on the upstream side of the die in the flow direction of the support, so that a problem arises in that a prescribed coating film thickness cannot be obtained, streak-like defects and coating unevenness appear. Therefore, there is an appropriate range for the distance between the tip of the discharge port and the support. However, the physical properties of the coating liquid, the coating conditions, and the structure of the coating apparatus (for example, extra coating liquid on the upstream side of the die in the support flow direction) The appropriate range varies depending on the device for sucking the liquid and stabilizing the shape of the coating liquid. For example, even if a distance equal to or more than 100 times the coating film thickness is provided between the die outlet and the support, the coating can be performed depending on the physical properties of the coating liquid and the coating conditions.
[0017]
The shape of the distribution section (manifold) is not limited to this, and an optimal shape can be designed using an analysis technique such as flow analysis according to the physical properties of the application liquid, application conditions, and the like. However, shapes such as a coat hanger type, a fish tail type, and a straight manifold (T manifold) type are usually used. Above all, it is preferable to use a coat hanger type distribution unit because the flow velocity distribution in the width direction is constant and a stagnant portion is not easily formed in the distribution unit.
[0018]
The peripheral portion of the discharge port is a final portion for discharging the coating liquid, and is provided continuously in the width direction of the die, that is, in the width direction of the coating film formed by discharging the coating liquid. As the shape of this part, a tapered type, a spear type, etc., and any suitable shape can be used without limitation, and the surface is coated with a water-repellent coat for the purpose of improving liquid drainage. Is also good. As a forming agent of the water-repellent coat, for example, an appropriate water-repellent such as a fluorine-based or silicone-based water-repellent can be used, and a polymer-based water-repellent is preferably used from the viewpoint of long life of the coat film. This water-repellent coat may be provided on the entire die for the purpose of preventing contamination. Furthermore, in the present invention, since the purpose is to make the pressure of the liquid flowing out from the discharge port constant, a sensor for measuring the liquid pressure and the flow velocity may be provided near the discharge port.
[0019]
The coating liquid tank used in the present invention has a function of keeping the liquid pressure of the coating liquid flowing out from the outlet by controlling the liquid level, or is not limited as long as it does not hinder the function. be able to. For example, as described above, a coating liquid tank having an inner tank serving as a buffer tank, supplying a coating liquid of an allowable amount or more to the inner tank, and having a function of overflowing excess coating liquid from the upper edge portion, or an inner tank. Even if it does not have a tank, by providing a discharge unit separately provided for supply to the die, the liquid level can be kept constant and the liquid pressure flowing out from the discharge port can be kept constant (overflow type). One that adjusts the liquid pressure by linking the liquid pressure or flow rate sensor provided at the outlet or supply pipe with the liquid level of the coating liquid (sensor type), and that the discharge pressure of the coating liquid at the die discharge port becomes constant To apply pressure to the upper part of the coating liquid level in the coating liquid tank, for example, to apply pressure to the upper part of the coating liquid level using regulated compressed air (Air type), Pressure is applied by the pressing member Obtain those using the method of (plunger) or the like, various methods to the fluid pressure constant flowing out of the outlet of the coating liquid tank can be used. Among them, the overflow type is preferably used because the coating liquid can be continuously supplied and the method is simple. When applying the coating liquid to the die by applying its own weight without applying pressure to the upper part of the liquid surface, the upper part of the coating liquid tank in the coating liquid tank is It is necessary to be at a position higher than the discharge port, but in other cases, an appropriate position may be set by designing in consideration of the condition of the supply process to the die.
[0020]
In the coating method according to the present invention, the supply of the coating liquid to the die is performed without using a supply device in a section from the coating liquid tank to the die. The supply device applies a force to the coating liquid with some power, and examples thereof include devices such as various pumps and pistons. In the present invention, by using the method of supplying the coating liquid to the die without using the supply device, an effect of reducing the uneven supply of the coating liquid to the die can be obtained.
[0021]
As the vibration isolator used in the coating method of the present invention, a conventionally known one can be appropriately used without any limitation as long as it reduces vibration of the coating liquid in the section from the coating liquid tank to the die. For example, a spring type, an air spring type, a coil spring type, an anti-vibration rubber type, and a pulsation removing device disclosed in JP-A-5-31434, so-called metal sintered filters, ceramic filters, fiber filters, foaming A commonly used vibration isolator such as a body filter or an accumulator for an organic solvent can be applied. In addition, as a method of installing the vibration damping device, in the section from the coating solution tank to the die, it may be appropriately installed according to the effect obtained by the various vibration damping devices, and the method from the coating solution tank to the die may be used. The section is not particularly limited as long as it is an installation method that reduces the vibration of the coating liquid. Also, the installation position is not limited, and it may be installed in a section from the coating liquid tank to the die, and is installed in a section from the discharge port of the coating liquid tank to the supply port of the die. Is more preferred. Further, it is most preferable to install it in the entire section from the coating liquid tank to the die. However, depending on the type of the device, it is sufficient that at least one device is installed in an effective place, and a plurality of vibration isolating devices of the same type or different types may be installed. Since the section from the coating solution tank to the die also includes a column or a base that supports the coating solution tank, the supply pipe, the die, and the like, the section may be installed in this portion to prevent external vibration. For example, when using a vibration-isolating rubber as the vibration damping device, it is preferable that the vibration-damping device be installed on all of the base portions of the application liquid tank and the supply pipe.
[0022]
The coating liquid that can be used in the coating method of the present invention can be selected according to the required use as long as it can form a coating film, and is not particularly limited. For example, a magnetic recording medium Magnetic coating solution for general use, coating solution for general and industrial silver halide photosensitive materials, coating solution for heat-sensitive material, coating solution for photothermographic material, coating solution for liquid crystal material including liquid crystal material, or other functional materials Examples thereof include a solution dissolved in a solvent or water, a pigment dispersion, and a colloidal dispersion. In addition, these coating liquids may be those in which additives such as a leveling agent are appropriately mixed.
[0023]
The viscosity of the coating liquid is not particularly limited, but is usually 0.5 mPa · s to 1000 mPa · s, and preferably 0.5 mPa · s to 800 mPa · s in the application method by the extrusion method. , And more preferably 0.5 mPa · s to 500 mPa · s. In general, those having a viscosity of less than 0.5 mPa · s or exceeding 1000 mPa · s are less likely to cause coating unevenness, which is an object of the present invention, and are considered to have little effect according to the present invention. A conventionally known coating method may be used without applying the coating method according to (1).
[0024]
The viscosity used in the present application as a method for measuring the viscosity of the coating solution is as follows: a viscosity measuring device (manufactured by HAAKE: Rheometer RS-1) at a temperature of 25 ° C. and a shear rate of 10 to 100 [1 / s]. It is the average value measured in the range. Further, the measurement of the viscosity is preferably performed with the coating liquid discharged from the discharge port of the die, but unless a coating liquid having a large viscosity change such that the viscosity changes in the coating apparatus is used, the viscosity of the coating liquid in the coating liquid tank is not measured. The viscosity may be measured with a coating solution.
[0025]
Examples of the coating film formed by using the coating method according to the present invention include an optical layer, an antistatic layer, a surface protective layer, a conductive functional layer, and an adhesive layer. Such a coating film may have at least one layer, but if necessary, may be applied to a method of simultaneously or sequentially coating two or more coating films, and is not limited to the number of coating films. Absent.
[0026]
As a method of controlling the thickness of the coating film, a desired thickness can be obtained by appropriately adjusting the supply amount and the transport speed of the support according to the physical properties of the coating solution. ) Is generally from 1 μm to 500 μm, preferably from 1 μm to 100 μm. At this time, if the thickness is less than 1 μm, it is difficult to apply the coating solution because the physical properties of the coating solution and the adjustment of the coating device are difficult, and if it exceeds 500 μm, unevenness in appearance caused by drying unevenness or the like is likely to occur. Further, the thickness after drying is not particularly limited as long as it has the required performance, but is preferably 0.01 μm or more and 50 μm or less, more preferably 0.01 μm or more and 20 μm or less. It is particularly preferable that the thickness be 0.05 μm or more and 10 μm or less. If the thickness of the coating film is less than 0.01 μm, it is difficult to control the uniformity of the coating film, and if it exceeds 50 μm, the drying is generally insufficient, and the residual solvent tends to remain.
[0027]
Appropriate measuring devices such as those using an optical method and those measured by a physical or direct method are limited as the method of measuring the coating film thickness according to the properties of the coating film. It can be used without. For example, when the coating film is an optical layer, an optical method using light interference is preferably used.
[0028]
The support used in the present invention is not limited by type, and paper, a polymer film, a metal sheet, or the like can be appropriately used. Examples of the paper include resin-coated paper and synthetic paper, and a typical example of the metal sheet is an aluminum plate.
[0029]
The polymer film is not particularly limited as long as it does not cause a problem in the required surface state and durability of the film. For example, polyethylene terephthalate, polyester polymers such as polyethylene naphthalate, diacetyl cellulose, triacetyl cellulose and the like. And a film made of a transparent polymer film such as a cellulose polymer, a polycarbonate polymer, and an acrylic polymer such as polymethyl methacrylate. In addition, polystyrene, styrene-based polymers such as acrylonitrile-styrene copolymer, polyethylene, polypropylene, polyolefin having a cyclic or norbornene structure, olefin-based polymers such as ethylene-propylene copolymer, vinyl chloride-based polymer, aromatic polyamide, etc. A film made of a transparent polymer such as an amide polymer is also included. Furthermore, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers Examples of such films include polymers, epoxy polymers, and films made of transparent polymers such as various binary and ternary copolymers, graft copolymers, and blends thereof. Further, a material which is cured by heat or ultraviolet irradiation may be used. In the case of forming such a curable film, for example, a layer which can be easily peeled from the support is formed first, and a cured film is formed thereon. The obtained film can be peeled and collected from the support by a method of forming a film. Therefore, it is also possible to form a film having a multilayer structure.
[0030]
The shape of the support at the time of transport is not particularly limited, and the coating liquid can be sequentially and continuously discharged and applied such as a drum shape, a belt shape such as an endless belt, and a plate shape, and the coating film is supported. Then, an appropriate shape that can be maintained in a sheet shape can be used. Further, as the surface shape, for example, a surface having an appropriate surface shape such as a mirror surface, a prism-shaped unevenness, or an embossed surface can be used. Further, the surface of the support may be preliminarily subjected to a pretreatment such as a corona discharge treatment, a plasma treatment, an undercoat treatment, a heat treatment, a metal deposition treatment, and an alkali treatment.
[0031]
The coating film formed by the coating method of the present invention can be used as an optical film by being laminated on another film as an optical layer on or after the support is peeled off from the support. As a film for laminating the peeled coating film, the same film as the above-mentioned support having an appropriate adhesive layer can be used. Examples of the optical film include those used for forming an image display device, and the type thereof is not particularly limited. For example, a polarizing plate, a retardation plate, an elliptically polarizing plate, a viewing angle compensation film, and a brightness enhancement Films and the like.
[0032]
The coating method of the present invention can be used for forming a coating film, mainly for forming an optical layer for forming the optical film. For example, dyeing of a polarizer in the production of a polarizing plate, formation of a transparent protective layer or hard coating It can be used for forming a surface treatment layer such as a coating treatment or an anti-glare treatment. Further, a liquid crystal material such as a liquid crystal polymer and / or a liquid crystal monomer is coated on a support, and is appropriately oriented and fixed to form an optical film such as a retardation plate, a viewing angle compensation film, and a brightness enhancement film. Can be. In order to orient and fix the liquid crystal substance, rubbing the polymer film in advance before application, or a method of applying heat or light irradiation after application are appropriately used according to the characteristics of the liquid crystal substance. As described above, an optical layer or an optical film formed by the method of the present invention can be obtained with little in-plane variation in optical characteristics such as a refractive index and a transmittance. The variation is preferably 20% or less, and more preferably 15% or less. In addition, the method according to the present invention is a method for producing a film-like substance such as a polymer film by a method such as combining the coating liquid with a solution serving as a raw material of the polymer film and combining with a known method such as a melt extrusion method or a casting method. Can also be used.
[0033]
The polarizing plate generally has a transparent protective layer on one or both sides of a polarizer. Various types of polarizers can be used without limitation. For example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film is dyed with a dichroic substance such as iodine or a dichroic dye. And uniaxially stretched, polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.
[0034]
A polarizer which is obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching the dye is, for example, immersing the polyvinyl alcohol film in an aqueous solution of iodine, or dyeing the polyvinyl alcohol film by applying iodine to the original film, thereby increasing the original length to 3 to 7 times. It can be created by stretching. If necessary, it may contain boric acid, zinc sulfate, zinc chloride or the like, and can be immersed in an aqueous solution of potassium iodide or the like. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an anti-blocking agent can be washed, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing can be obtained. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be stretched and then dyed with iodine. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.
[0035]
As a material for forming the transparent protective layer provided on one or both surfaces of the polarizer, a material having excellent transparency, mechanical strength, heat stability, moisture shielding property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin). Polymers and polycarbonate polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and directional polyamides, imide polymers, and sulfone polymers , A polyether sulfone polymer, a polyether ether ketone polymer, a polyphenylene sulfide polymer, a vinyl alcohol polymer, a vinylidene chloride polymer, a vinyl butyral polymer, an arylate polymer, a polyoxymethylene polymer, an epoxy polymer, or the above. Blends of polymers and the like are also examples of the polymer forming the transparent protective layer. The transparent protective layer can also be formed as a cured layer of a thermosetting or ultraviolet curable resin such as an acrylic, urethane, acrylic urethane, epoxy or silicone resin. Among these, those having a hydroxyl group having reactivity with an isocyanate crosslinking agent are preferable, and a cellulose-based polymer is particularly preferable. The thickness of the transparent protective layer is not particularly limited, but is generally 500 μm or less, preferably 1 to 300 μm. In particular, the thickness is preferably 5 to 200 μm.
[0036]
Examples of the transparent protective layer include polymer films described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in a side chain; B) A resin composition containing a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in a side chain, and specific examples thereof include an alternating copolymer of isobutene and N-methylmaleimide and acrylonitrile. And a film of a resin composition containing a styrene copolymer. As the film, a film made of a mixed extruded product of a resin composition or the like can be used.
[0037]
The thickness of the transparent protective layer is not particularly limited, but is generally 500 μm or less, preferably 1 to 300 μm. In particular, the thickness is more preferably 5 to 200 μm. In addition, it is preferable that the surface of the protective film is saponified with an alkali or the like from the viewpoint of polarization characteristics and durability.
[0038]
These transparent protective layers may be formed by applying the transparent protective layer forming material as a solution and applying the solution to the polarizer.
[0039]
Further, it is preferable that the transparent protective layer has as little coloring as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive indices in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness). A transparent protective layer having a retardation value in the film thickness direction of -90 nm to +75 nm is preferably used. By using the retardation value (Rth) in the thickness direction of -90 nm to +75 nm, coloring (optical coloring) of the polarizing plate due to the transparent protective layer can be almost eliminated. The retardation value (Rth) in the thickness direction is more preferably −80 to +60 nm, and particularly preferably −70 to +45 nm.
[0040]
The surface of the transparent protective layer to which the polarizer is not adhered and various optical films can be subjected to a hard coat, an antireflection treatment, a sticking prevention, and a surface treatment for the purpose of diffusion or antiglare.
[0041]
The hard coat treatment is not limited to this. For example, a transparent resin forming a hard coat layer is applied for the purpose of preventing the polarizing plate surface from being damaged. The hard coat layer formed by this hard coat treatment has excellent hard coat properties (a hardness of H or more in a pencil hardness test according to JIS K 5400), has sufficient strength, and is excellent in light transmittance. Any method may be used as long as it is a method in which a cured film made of an appropriate UV-curable resin such as an acrylic, silicone, or polyester resin and having excellent hardness and sliding properties is added to the surface of the transparent protective layer. The anti-reflection treatment is performed for the purpose of preventing the reflection of external light on the polarizing plate surface, and can be achieved by forming an anti-reflection film or the like according to the related art. In addition, the anti-sticking treatment is performed for the purpose of preventing adhesion to an adjacent layer.
[0042]
The anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the visibility of the light transmitted through the polarizing plate. It can be formed by imparting a fine uneven structure to the surface of the transparent protective layer by an appropriate method such as a surface forming method or a method of blending transparent fine particles. As the fine particles to be contained in the formation of the surface fine uneven structure, for example, a conductive material composed of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide and the like having an average particle size of 0.5 to 50 μm. Transparent fine particles such as inorganic fine particles that may be used and organic fine particles made of a crosslinked or uncrosslinked polymer or the like are used. When forming the fine surface unevenness structure, the amount of the fine particles to be used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, per 100 parts by weight of the transparent resin forming the fine surface unevenness structure. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle expanding function) for diffusing light transmitted through the polarizing plate to increase the viewing angle and the like.
[0043]
When a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer and an anti-glare layer are formed on the polarizing plate, the hard coat layer, anti-reflection layer, anti-glare layer and the like can be provided on the transparent protective layer itself. It can be provided separately from the protective layer. Further, the respective layers may appropriately contain various fine particles such as conductivity, inorganic or organic spherical or amorphous fillers, leveling agents, thixotropic agents, antistatic agents and the like.
[0044]
The bonding treatment between the polarizer and the transparent protective layer is not particularly limited, but, for example, an adhesive made of a vinyl polymer, or a boric acid or borax, glutaraldehyde, melamine, or a vinyl alcohol-based material such as oxalic acid This can be performed via an adhesive or the like composed of at least a water-soluble crosslinking agent for the polymer. This adhesive layer can be formed as a coating and drying layer of an aqueous solution, but when preparing the aqueous solution, other additives and a catalyst such as an acid can be blended as necessary.
[0045]
As the liquid crystal monomer forming the retardation plate or the brightness enhancement film, any of lyotropic properties and thermotropic properties can be used, but thermotropic properties are preferable from the viewpoint of workability. For example, those having a basic skeleton of a biphenyl derivative, a phenylbenzoate derivative, a stilbene derivative, or the like into which a functional group such as an acryloyl group, a vinyl group, or an epoxy group has been introduced may be used. Such a liquid crystal monomer is, for example, a method by heat or light, a method of rubbing on a substrate, a method of adding an alignment aid, or the like, is appropriately aligned using a known method, and then, while maintaining this alignment. A method of fixing the orientation by crosslinking and polymerizing with light, heat, an electron beam or the like is preferably used.
[0046]
Further, as the liquid crystal polymer, for example, various types of main chain type and side chain type in which a conjugated linear atomic group (mesogen) for imparting liquid crystal orientation is introduced into the main chain or side chain of the polymer. Is raised. Specific examples of the main-chain type liquid crystalline polymer include a structure in which a mesogen group is bonded by a spacer portion that imparts flexibility, such as a nematic-oriented polyester-based liquid crystalline polymer, a discotic polymer, and a cholesteric polymer. . Specific examples of the side chain type liquid crystal polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a paraffin having a nematic alignment imparting property via a spacer portion including a conjugated atomic group as a side chain. And those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystal polymers are, for example, rubbed on the surface of a thin film of polyimide or polyvinyl alcohol formed on a glass plate, or spread a liquid crystalline polymer solution on an alignment-treated surface such as obliquely deposited silicon oxide. And heat treatment.
[0047]
In the optical film according to the present invention, various optical layers can be laminated for practical use. The optical layer is not particularly limited as long as it satisfies the required optical characteristics, and includes an optical layer composed of a coating film according to the present invention. For example, on one or both surfaces of the polarizer, a transparent protective layer for the purpose of protecting the polarizer, the surface opposite to the surface of the transparent protective layer that adheres to the polarizer, or one or both surfaces of the polarizer itself, Hard coat treatment, anti-reflection treatment, surface treatment for sticking prevention, diffusion or anti-glare, or alignment liquid crystal layer for viewing angle compensation, etc., and adhesive layer for laminating other films There is a method. Further, as an optical layer, an image such as a polarization conversion element, a reflection plate or a semi-transmission plate, a retardation plate (including a wavelength plate (λ plate) such as や or ４), a viewing angle compensation film, and a brightness enhancement film. One in which one or two or more optical films used for forming a display device or the like are laminated is also exemplified. In particular, a polarizing plate obtained by laminating the polarizer and the transparent protective layer, a reflective polarizing plate or a transflective polarizing plate obtained by laminating a reflecting plate or a transflective reflecting plate, an elliptically polarizing plate obtained by laminating a retardation plate or A circular polarizing plate, a wide viewing angle polarizing plate in which a viewing angle compensation layer or a viewing angle compensation film is laminated, or a polarizing plate in which a brightness enhancement film is laminated is preferable. Further, the timing of laminating the optical layer or the optical film with the transparent protective layer may be after the lamination with the polarizer or before the lamination with the polarizer.
[0048]
The reflection type polarizing plate is provided with a reflection layer on a polarizing plate, and is used to form a liquid crystal display device of a type that reflects incident light from a viewing side (display side) and displays the reflected light. The light source can be omitted, and the liquid crystal display device can be easily made thinner. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one surface of the polarizing plate via a transparent protective layer or the like as necessary.
[0049]
Specific examples of the reflective polarizing plate include, as necessary, a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum to one surface of a transparent protective layer that has been matted. . Further, there may be mentioned a transparent protective layer containing fine particles to form a fine surface unevenness structure, and a reflective layer having a fine unevenness structure formed thereon. The reflective layer having the above-mentioned fine uneven structure has an advantage of diffusing incident light by irregular reflection, preventing directivity and glare, and suppressing unevenness in brightness and darkness. Further, the transparent protective layer containing fine particles also has an advantage that the incident light and the reflected light are diffused when transmitting the light, and the unevenness in brightness can be further suppressed. The reflective layer having a fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective layer is formed by, for example, depositing a metal by an appropriate method such as a vacuum evaporation method, an ion plating method, an evaporation method such as a sputtering method or a plating method. It can be carried out by a method of directly attaching to the surface of the transparent protective layer.
[0050]
The reflection plate can be used as a reflection sheet or the like in which a reflection layer is provided on an appropriate film according to the transparent film, instead of the method of directly applying the reflection film to the transparent protective layer of the polarizing plate. Since the reflective layer is usually made of a metal, the use form in which the reflective surface is covered with a transparent protective layer, a polarizing plate, or the like is intended to prevent a decrease in the reflectance due to oxidation and to maintain the initial reflectance for a long time. It is preferable in terms of avoiding separately providing a protective layer.
[0051]
The transflective polarizing plate can be obtained by forming a transflective reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, an image is displayed by reflecting incident light from the viewing side (display side). In a relatively dark atmosphere, a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of a transflective polarizing plate can be formed. That is, the transflective polarizing plate can save energy for use of a light source such as a backlight in a bright atmosphere, and is useful for forming a liquid crystal display device of a type that can be used with a built-in light source even in a relatively bright atmosphere. It is.
[0052]
An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. When changing linearly polarized light to elliptically or circularly polarized light, changing elliptically or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light, a phase difference plate or the like is used. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that converts linearly polarized light into circularly polarized light or converts circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is generally used to change the polarization direction of linearly polarized light.
[0053]
The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of a super twisted nematic (STN) type liquid crystal display device, and is effectively used in the case of black-and-white display without the coloring. Can be Further, the one in which the three-dimensional refractive index is controlled is preferable because coloring which occurs when the screen of the liquid crystal display device is viewed from an oblique direction can be compensated (prevented). The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflection type liquid crystal display device that displays an image in color, and also has an antireflection function.
[0054]
Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer film, an alignment film obtained by aligning a liquid crystal monomer, and then crosslinking and polymerizing the same, an alignment film of a liquid crystal polymer, an alignment layer of a liquid crystal polymer. Supported by a film. The stretching treatment can be performed, for example, by a roll stretching method, a long gap stretching method, a tenter stretching method, a tubular stretching method, or the like. The stretching ratio is generally about 1.1 to 3 times in the case of uniaxial stretching. Although the thickness of the retardation plate is not particularly limited, it is generally 10 to 200 μm, preferably 20 to 100 μm.
[0055]
The retardation plate may have an appropriate retardation depending on the purpose of use, such as, for example, a color plate due to birefringence of various wave plates or a liquid crystal layer, or a target for compensation of a viewing angle or the like. A retardation plate may be laminated to control optical characteristics such as retardation.
[0056]
Further, the elliptically polarizing plate or the reflection type elliptically polarizing plate is obtained by laminating a polarizing plate or a reflection type polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like may be formed by sequentially and separately laminating a (reflection type) polarizing plate and a retardation plate in the manufacturing process of the liquid crystal display device so as to form a combination. An optical film such as a polarizing plate is excellent in quality stability, laminating workability, and the like, and has an advantage that manufacturing efficiency of a liquid crystal display device or the like can be improved.
[0057]
The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed not in a direction perpendicular to the screen but in a slightly oblique direction. Such a viewing angle compensating retardation plate includes, for example, a retardation plate, an alignment film such as a liquid crystal polymer, and a transparent substrate on which an alignment layer such as a liquid crystal polymer is supported. The ordinary retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas the retardation plate used as the viewing angle compensation film has a biaxially stretched biaxially stretched polymer film. Polymer films with refraction, biaxially stretched films such as uniaxially stretched in the plane direction and birefringent polymer with a controlled refractive index in the thickness direction, stretched in the thickness direction, and bidirectionally refracted films Is used. Examples of the obliquely oriented film include a film obtained by bonding a heat shrinkable film to a polymer film and subjecting the polymer film to a stretching treatment and / or a shrinkage treatment under the action of the shrinkage force caused by heating, and a film obtained by obliquely aligning a liquid crystal polymer. No. As the raw material polymer of the retardation plate, the same polymer as described in the above retardation plate is used to prevent coloring or the like due to a change in the viewing angle based on the phase difference due to the liquid crystal cell and to enlarge the viewing angle for good visibility. Any appropriate one for the purpose can be used.
[0058]
In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation layer in which an optically anisotropic layer composed of a liquid crystal polymer alignment layer, particularly a discotic liquid crystal polymer inclined alignment layer is supported by a triacetyl cellulose film. A retardation plate can be preferably used.
[0059]
A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell and used. The brightness enhancement film reflects linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from a backlight or a back side of a liquid crystal display device, and has a property of transmitting other light. A polarizing plate obtained by laminating a brightness enhancement film and a polarizing plate, while transmitting light of a predetermined polarization state by making light from a light source such as a backlight incident, light other than the predetermined polarization state is reflected without transmitting. You. The light reflected on the surface of the brightness enhancement film is further inverted via a reflection layer or the like provided on the rear side thereof and re-entered on the brightness enhancement film, and a part or all of the light is transmitted as light of a predetermined polarization state to achieve brightness. In addition to increasing the amount of light that passes through the enhancement film, the polarized light that is hardly absorbed by the polarizer is supplied to increase the amount of light that can be used for a liquid crystal image display or the like, thereby improving the luminance. In other words, when light is incident through the polarizer from the back side of the liquid crystal cell with a backlight or the like without using a brightness enhancement film, light having a polarization direction that does not match the polarization axis of the polarizer is almost completely polarized. Is absorbed by the polarizer and does not pass through the polarizer. That is, although it depends on the characteristics of the polarizer used, about 50% of the light is absorbed by the polarizer, and accordingly, the amount of light available for liquid crystal image display and the like decreases, and the image becomes darker. The brightness enhancement film reflects light having a polarization direction that is absorbed by the polarizer without being incident on the polarizer, but reflects the light once with the brightness enhancement film, and further inverts the light through a reflection layer or the like provided on the rear side thereof. And then re-incident on the brightness enhancement film.Repeated between the two, only the polarized light whose polarization direction is such that the polarization direction of the inverted light can pass through the polarized light is transmitted to the polarizer. Since the light is supplied, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.
[0060]
A diffusion plate may be provided between the brightness enhancement film and the above-mentioned reflection layer or the like. The light in the polarization state reflected by the brightness enhancement film goes to the reflection layer and the like, but the diffuser provided diffuses the passing light evenly, and at the same time, eliminates the polarization state and changes to a non-polarization state. That is, it returns to the original natural light state. The light in the non-polarized state, that is, the natural light state is repeatedly directed to the reflection layer or the like, reflected through the reflection layer or the like, passed through the diffusion plate again, and re-enters the brightness enhancement film. By providing the diffuser for returning to the original natural light state, the brightness of the display screen can be maintained, the unevenness of the brightness of the display screen can be reduced, and a uniform bright screen can be provided. By providing a diffuser that returns to the original natural light state, the number of repetitions of the first incident light is increased moderately, and a uniform bright display screen can be provided in combination with the diffusion function of the diffuser. Can be
[0061]
The brightness enhancement film has a property of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies. As shown in the figure, such as a cholesteric liquid crystal polymer oriented film or a film in which the oriented liquid crystal layer is supported on a film substrate, it exhibits the property of reflecting either left-handed or right-handed circularly polarized light and transmitting other light. Any suitable one such as one can be used.
[0062]
Therefore, in the brightness enhancement film of the type that transmits the linearly polarized light having the predetermined polarization axis, the transmitted light is incident on the polarization plate with the polarization axis aligned as it is, while suppressing absorption loss by the polarization plate and efficiently. Can be transmitted. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light, such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on a polarizing plate. By using a quarter-wave plate as the retardation plate, circularly polarized light can be converted to linearly polarized light.
[0063]
A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region shows, for example, a retardation plate that functions as a quarter-wave plate with respect to monochromatic light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method in which a phase difference plate, for example, a phase difference plate functioning as a half-wave plate is superimposed. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or two or more layers.
[0064]
Note that the cholesteric liquid crystal layer also has a structure in which two or three or more layers are overlapped by combining those having different reflection wavelengths, thereby obtaining a material that reflects circularly polarized light in a wide wavelength range such as a visible light region. Based on this, it is possible to obtain circularly polarized light transmitted in a wide wavelength range.
[0065]
Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers as in the above-mentioned polarized light separating type polarizing plate. Therefore, a reflective elliptically polarizing plate or a transflective elliptically polarizing plate obtained by combining the above-mentioned reflective polarizing plate, semi-transmissive polarizing plate, and retardation plate may be used.
[0066]
An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating the optical film in a manufacturing process of a liquid crystal display device or the like. It is excellent in stability and assembling work, and has an advantage that a manufacturing process of a liquid crystal display device or the like can be improved. For the lamination, an appropriate adhesive means such as a pressure-sensitive adhesive layer can be used. When bonding the above-mentioned polarizing plate and other optical layers, their optical axes can be set at an appropriate arrangement angle according to the target retardation characteristics and the like.
[0067]
The optical film according to the present invention can be preferably used for forming an image display device such as a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED).
[0068]
The optical film according to the present invention can be preferably used for forming various devices such as a liquid crystal display device, for example, a reflection type or a semi-transmission type in which a polarizer or a polarizing plate is arranged on one side or both sides of a liquid crystal cell, Alternatively, it can be used for a liquid crystal display device such as a transmissive / reflective type. The liquid crystal cell substrate may be any of a plastic substrate and a glass substrate. The liquid crystal cell forming the liquid crystal display device is optional, for example, an appropriate type such as an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twisted nematic type or a super twisted nematic type, or the like. A liquid crystal cell may be used.
[0069]
When a polarizing plate or an optical member is provided on both sides of the liquid crystal cell, they may be the same or different. Furthermore, in forming the liquid crystal display device, one or more layers of appropriate components such as a prism array sheet, a lens array sheet, a light diffusion plate, and a backlight can be arranged at appropriate positions.
[0070]
Next, an organic electroluminescence device (organic EL display device) will be described. In general, in an organic EL display device, a luminous body (organic electroluminescent luminous body) is formed by sequentially laminating a transparent electrode, an organic luminescent layer, and a metal electrode on a transparent substrate. Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like, and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a stacked body of such a light emitting layer and an electron injection layer made of a perylene derivative, or a stacked body of a hole injection layer, a light emitting layer, and an electron injection layer is known. Has been.
[0071]
In an organic EL display device, holes and electrons are injected into an organic light emitting layer by applying a voltage to a transparent electrode and a metal electrode, and energy generated by recombination of these holes and electrons excites a fluorescent substance. Then, light is emitted on the principle that the excited fluorescent substance emits light when returning to the ground state. The mechanism of recombination on the way is the same as that of a general diode, and as can be expected from this, the current and the emission intensity show strong nonlinearity accompanying rectification with respect to the applied voltage.
[0072]
In an organic EL display device, at least one of the electrodes must be transparent in order to extract light emitted from the organic light emitting layer. Usually, a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used. Used as anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually a metal electrode such as Mg-Ag or Al-Li is used.
[0073]
In the organic EL display device having such a configuration, the organic light emitting layer is formed of an extremely thin film having a thickness of about 10 nm. Therefore, the organic light emitting layer transmits light almost completely, similarly to the transparent electrode. As a result, when light is incident from the surface of the transparent substrate during non-light emission, light transmitted through the transparent electrode and the organic light-emitting layer and reflected by the metal electrode again exits to the surface side of the transparent substrate, and when viewed from the outside, The display surface of the organic EL display device looks like a mirror surface.
[0074]
In an organic EL display device including an organic electroluminescent luminous body having a transparent electrode on the front side of an organic luminescent layer that emits light by applying a voltage and a metal electrode on the back side of the organic luminescent layer, the surface of the transparent electrode A polarizing plate can be provided on the side, and a retardation film can be provided between the transparent electrode and the polarizing plate.
[0075]
Since the retardation film and the polarizer have a function of polarizing light incident from the outside and reflected on the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, if the retardation film is formed of a 波長 wavelength plate and the angle between the polarization directions of the polarizing plate and the retardation film is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded. .
[0076]
That is, as for the external light incident on the organic EL display device, only the linearly polarized light component is transmitted by the polarizing plate. The linearly polarized light generally becomes elliptically polarized light by the retardation film. In particular, when the retardation film is a １ ／ wavelength plate and the angle between the polarization directions of the polarizing plate and the retardation film is π / 4, the light becomes circularly polarized light. .
[0077]
The circularly polarized light passes through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, passes through the organic thin film, the transparent electrode, and the transparent substrate again, and becomes linearly polarized again by the retardation film. The linearly polarized light is orthogonal to the polarization direction of the polarizing plate and cannot pass through the polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.
[0078]
The PD generates an electric discharge in a rare gas sealed in the panel, particularly a gas mainly composed of neon, and the R, G, B phosphor applied to the panel cells by vacuum ultraviolet rays generated at that time. , The image can be displayed.
[0079]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples.
[0080]
Example 1
Using an application die shown in FIG. 1, an extrusion die having a total width of 1500 mm, an application width of 1100 mm, and a slit width of the discharge port (distance between parallel flat plates after the distributing portion inside the die) of 0.15 mm is used to obtain a width of 1330 mm. A coating liquid (solvent: toluene, viscosity: 3 mPa · s) made of acrylic urethane having a solid content of 40% is coated on a support made of a triacetyl cellulose (TAC) film having a thickness of 80 μm to a thickness (before drying) of 12 μm. Was applied at an application speed of 10 m / min. Then, it dried at 100 degreeC for 4 minutes, and formed the coating film.
[0081]
As a method for evaluating a coated film composed of a formed coated film and a support, a coated film was cut out as a sample in a size of 300 mm square, a black tape was stuck on the surface opposite to the coated film, and a stand type three-sided film was formed on the coated film surface. By irradiating a wavelength fluorescent lamp, interference fringes due to the reflected light were visually observed. As a result, slightly irregular horizontal stripe-like unevenness was partially generated, but the appearance was good with a level having no practical problem.
[0082]
Example 2
In Example 1, except that a vibration damping device made of a vibration isolating rubber (manufactured by Kurashiki Kako Co., Ltd .: vibration isolating pad KH-10) was installed on the supply pipe (2) in FIG. A coating film was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. As a result, the uniformity of the coating film surface was good and the appearance was good.
[0083]
Comparative Example 1
In the coating apparatus shown in FIG. 2, a gear pump type liquid supply pump (manufactured by Takachiho Machine Co., Ltd.) having a flow rate of 2.92 cc / rotation was applied to a coating liquid (solvent: toluene, viscosity: 3 mPa · s) composed of acrylic urethane having a solid content of 40%. Using an extrusion die having a total width of 1500 mm, an application width of 1100 mm, and a slit width of the discharge port of 0.15 mm, a support made of a triacetyl cellulose (TAC) film having a width of 1330 mm and a thickness of 80 μm was used. Coating was performed at a coating speed of 10 m / min to a thickness (before drying) of 12 μm. Then, it dried at 100 degreeC for 4 minutes, and formed the coating film. The same evaluation as in Example 1 was performed on the coating film comprising the coating film and the support. As a result, the appearance was poor, and periodic horizontal stripe-like unevenness occurred.
[0084]
Comparative Example 2
In Comparative Example 1, a coated film was produced in the same manner as in Comparative Example 1, except that the same vibration damping device as in Example 2 was installed on the supply pipe (3) in FIG. 2 and the pedestal portion of the coating liquid tank. Was evaluated. As a result, the appearance was poor, and uneven horizontal stripes occurred.
[0085]
As is clear from the results of the above Examples and Comparative Examples, without using a supply device for supplying the coating liquid to the die, by supplying the coating liquid while keeping the level of the coating liquid in the coating liquid tank constant, The coating unevenness generated in the coating film can be greatly reduced. Further, by using the vibration isolator in combination, it is possible to obtain a coating film having no coating unevenness and excellent appearance uniformity.
[0086]
【The invention's effect】
As described above, the present invention provides a method of applying a coating liquid using a die on a support, without using a supply device in a section from the coating liquid tank to the die, by controlling the liquid level in the coating liquid tank. By supplying a coating liquid to a die, it has been found that a method of obtaining a coating film having good appearance uniformity suitable for an optical film or the like can be obtained. A display device is obtained.
[Brief description of the drawings]
FIG. 1 is a configuration example of a coating apparatus according to the present invention.
FIG. 2 is a configuration example of a conventional coating apparatus.
[Explanation of symbols]
1: die
11: Discharge port
12: Supply port
2: Storage tank
3: Application liquid tank
31: Inner tank
32: Outer tank
33: outlet
4: Liquid supply pump
5: Supply pipe (1)
6: Supply pipe (2)
7: Supply pipe (3)
8: Support

Claims (6)

In a method in which a coating liquid is supplied from a coating liquid tank to a die, and the coating liquid is applied to the support by the die, the coating liquid in the coating liquid tank is used without using a supply device in a section from the coating liquid tank to the die. And supplying a coating liquid to the die while controlling the liquid level of the coating liquid. By supplying a sufficient amount of the coating liquid to the coating liquid tank, the coating liquid overflows from the coating liquid tank, and the liquid level in the coating liquid tank is maintained by keeping the liquid level of the coating liquid tank constant. The coating method according to claim 1, wherein the liquid level of the liquid is controlled. 3. The coating method according to claim 1, wherein at least one vibration isolator is provided in a section from the coating solution tank to the die, and the section is vibrated. A coating film formed by the coating method according to claim 1. An optical film in which the coating film according to claim 4 is an optical layer, and the optical layer is laminated on the film. An image display device comprising the optical film according to claim 5.

Images