JP2006272129A - Coating method of coating liquid, coating device of coating liquid and optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which stably supplies coating liquid to a slot die and suppresses liquid supply pulsation of the coating liquid even when supplying the coating liquid by using a gear pump. <P>SOLUTION: The gear pump 42 supplies the coating liquid to the slot die 18 so that the coating liquid is applied with an application amount of ≤10 cc/m<SP>2</SP>from the slot die to a web 14. Further, the gear pump 42 is adjusted so as to satisfy the following relation; V/N≤0.07 cc, wherein V is volume of liquid supply of the coating liquid per one rotation of the gear and N is the number of teeth of the gear. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating liquid coating method, a coating liquid coating apparatus, and an optical film, and more particularly to a technique using a gear pump that feeds the coating liquid.

  Conventionally, as a coating apparatus for coating a coating film having a desired thickness on the surface of a web (support), a bar coater method, a reverse roll coater method, a gravure roll coater method, a slot die coater method such as an extrusion coater, etc. are known. It has been. Among these, slot die coater type coating apparatuses are frequently used because they can coat thin layers at a higher speed than other systems.

  In recent years, in fields such as an optical film in which fluctuations in the thickness of the coating film have a significant effect on performance, the thickness of the coating film (coating layer) has been dramatically reduced. Since the optical characteristics of the optical film vary depending on the film thickness in the dry film state, an antireflection film or the like requires a film thickness in the dry film state of about 100 nm. Therefore, the wet film thickness immediately after being discharged from the slot die to the web needs to be reduced to 15 μm or less, and further improvement of the coating method by the slot die coater method is desired.

  In the slot die coater system represented by the extrusion coater, a coating solution is applied by laying a bead between the web and the slot die, but the coating solution is applied to the web by preventing coating defects such as so-called unevenness. It is important to stabilize the bead for uniform application. Factors that hinder the stabilization of the bead include, for example, vibration of the slot die and its peripheral devices, fluctuation of the internal pressure of the decompression chamber that sucks the bead, and liquid supply pulsation. In particular, the pulsation of the coating liquid directly changes the discharge state of the coating liquid in the slot die, so that the bead shape tends to become unstable, causing a surface defect of the coating film called “step unevenness”. As a result, the quality of the product deteriorates.

  When applying the coating solution in a state where the coating amount is small, it is necessary to reduce the lip clearance to reduce the bead in consideration of the crosslinking limit of the beads. Similarly, when the web conveyance speed (coating speed) is increased, it is necessary to reduce the lip clearance and the bead. However, when the bead is made smaller by reducing the lip clearance, the bead tends to lose its shape under the influence of disturbance. Furthermore, even when using a coating solution having a low viscosity of about 5 cp used for an optical film or the like, the bead is liable to lose its shape under the influence of disturbance. Therefore, especially when the lip clearance, low coating speed, and low viscosity of the coating liquid are important, it is important to minimize the effect on the coating film by reducing the pulsation of the coating liquid as much as possible. .

The liquid feeding pulsation described above strongly depends on the performance of a pump that is a driving source of the liquid feeding of the coating liquid. In order to suppress such a liquid-feeding pulsation of the coating liquid caused by the pump, for example, Patent Document 1 discloses a volume rotary type or volume reciprocating type pump in which a flywheel is provided in a rotation drive unit. This pump achieves liquid feeding accuracy that can cope with thinning of the coating film to be applied to the flexible support and stricter thickness variation standards.
Japanese Patent Laid-Open No. 2003-13845

  The pump disclosed in Patent Document 1 can reduce the liquid supply pulsation of the coating liquid by increasing the rotational accuracy of the pump, but fundamentally solves the problem of liquid pulsation caused by the performance of the pump. It is not a thing.

  By the way, as a general pump used for liquid feeding of a coating liquid, a gear pump, a diaphragm pump, a plunger pump, etc. are mentioned, for example. Especially when the application amount of the application liquid is small and the application amount is low, the liquid supply amount can be determined on the basis of the displacement volume (liquid supply volume) of the application liquid by the gear, and even if the application amount is low, the application amount can be controlled. Possible gear pumps are suitable. Gear pumps have a relatively simple structure, and there are many types of gear pumps depending on applications. Therefore, there is a demand for a technique that can stably feed the coating liquid to the slot die using a gear pump.

  On the other hand, in an optical film such as an antireflection film, even if the step unevenness in the coating film is slight based on a fluctuation of about 1 nm, the step unevenness may become visible due to light interference. Therefore, a very high level of coating accuracy is required in the field of optical films.

  The present invention has been made in view of the above circumstances, and its purpose is to stably feed the coating liquid to the slot die even when the coating liquid is fed using a gear pump. And providing an application method and an application device for an application liquid that suppresses pulsation of the application liquid, and an optical film and an antireflection film including an application layer obtained by such an application device and an application method. .

In order to achieve the above object, the invention according to claim 1 is characterized in that the coating liquid is supplied to the slot die by a gear pump having a gear, and the slot is directed toward the surface of the support that continuously runs while being supported by the backup roller. The present invention relates to a coating liquid coating method in which a coating liquid is discharged from a die, a bead of the coating liquid is installed between the slot die and the support, and the coating liquid is applied to the surface of the support by the bead. In this coating solution coating method, the gear pump supplies the coating solution to the slot die so that the coating solution is applied from the slot die to the support at a coating amount of 10 cc / m ² or less. With
V / N ≦ 0.07cc
V: The volume of the coating liquid to be fed per one rotation of the gear, and N: the number of teeth of the gear.

  As in the present invention, the liquid feeding volume (pushing volume) V of the coating liquid per one rotation of the gear and the number N of teeth of the gear satisfy the above formula, thereby effectively preventing the liquid feeding fluctuation by the gear pump. be able to. Thereby, the liquid-feed pulsation of a coating liquid is suppressed and a high quality coating film is obtained.

  According to a second aspect of the present invention, the distance between the coating liquid discharge tip of the slot die and the support may be 100 μm or less.

  In general, in order to reduce the thickness of the coating film, it is necessary to reduce the distance (lip clearance) between the coating liquid discharge tip of the slot die and the support, and the pulsation of the coating liquid is caused by the pulsation of the coating liquid. Greatly affects quality. Against such a background, the present invention exhibits the above-described effect particularly when the distance between the coating liquid discharge tip of the slot die and the support is set to 100 μm or less.

  In addition, as described in claim 3, the viscosity of the coating solution may be 5 cp or less.

  Generally, when a coating liquid having a low viscosity is used, it is necessary to reduce the distance (lip clearance) between the coating liquid discharge tip of the slot die and the support, and the coating liquid is applied to the generated coating film. The pulsation of liquid feeding greatly affects Against such a background, the present invention exhibits the above-described effects particularly when the viscosity of the coating solution is 5 cp or less.

  In order to achieve the above object, the invention described in claim 4 relates to an optical film characterized in that it has at least one coating layer obtained by the coating solution coating method described above.

  According to the present invention, a good optical film using a high-quality coating film is provided.

  Further, as described in claim 5, the optical film may be an antireflection film.

  In this case, a good antireflection film using a high-quality coating film is provided.

In order to achieve the above object, the invention according to claim 6 is directed to a surface of a support body that continuously feeds a coating solution supplied to a slot die by a gear pump having a gear and is supported by a backup roller. A coating liquid coating apparatus that discharges a coating liquid from the slot die, constructs a bead of the coating liquid between the slot die and the support, and coats the coating liquid on the surface of the support by the bead. About. In this coating solution coating apparatus, the gear pump supplies the coating solution to the slot die so that the coating solution is applied from the slot die to the support at a coating amount of 10 cc / m ² or less. With
V / N ≦ 0.07cc
V: the volume of the coating liquid fed per rotation of the gear, N: the gear is set so as to satisfy the number of teeth of the gear.

  According to the present invention, it is possible to prevent fluctuations in the liquid feeding by the gear pump, effectively suppress the liquid feeding pulsation of the coating liquid, and obtain a high-quality coating film.

  According to the coating liquid coating apparatus and the coating method of the present invention, the coating liquid feeding volume V per gear rotation and the number of teeth N of the gear are appropriately set to prevent variation in feeding by the gear pump, The influence of the pulsation of the coating liquid on the coating film can be reduced.

  In addition, the optical film of the present invention has a good quality because it includes a coating layer that is generated in a state in which coating defects such as unevenness due to liquid-feed pulsation of the coating solution are prevented.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a slot die coater type coating system 10 according to an embodiment of the present invention. In addition, the arrow in the vicinity of the backup roller 12 and the web 14 in the drawing indicates the “conveying direction of the web 14 by the backup roller 12”, that is, the “traveling direction of the web 14” in the present embodiment.

  In the slot die coater type coating system 10 of the present embodiment, the coating liquid is supplied to the slot die 18 by the gear pump 42 having a gear, and the slot die is directed toward the surface of the web 14 continuously running while being supported by the backup roller 12. The coating solution is discharged from 18, and a coating solution bead 20 is installed between the slot die 18 and the web 14. Then, in a state where the web upstream side of the bead 20 is decompressed by the decompression chamber 26, the coating liquid of the bead 20 is applied to the surface of the web 14, and a coating film is generated on the web 14.

  With reference to the position where the coating liquid is applied by the slot die 18 (hereinafter also referred to as “application position”), the portion preceding the application position with respect to the web traveling direction is referred to as “web upstream” and the latter stage. The portion is referred to as “web downstream”. Therefore, in the horizontal slot die 18 shown in FIG. 1, the lower side of the bead 20 is the “web upstream side” and the upper side of the bead 20 is the “web downstream side”. A web width direction perpendicular to the web conveyance direction is referred to as a “web width direction”.

  The slot die 18 includes a manifold 22 provided therein, a slot 24 extending from the manifold 22 to the tip end portion of the slot die 18, a coating liquid supply path 25 extending from the manifold 22 toward the outside of the slot die 18, Have The slot die 18 includes two blocks, an upstream die block 18A and a downstream die block 18B. The manifold 22 and the slot 24 are part of the boundary between the upstream die block 18A and the downstream die block 18B. It has become. Thus, by making the slot die 18 have a multi-block structure, it is possible to increase the manufacturing accuracy of the slot die 18 and facilitate post-processing such as cleaning. The specific shape and size of the slot die 18 are determined based on its own weight, the environment during use, the temperature of the coating liquid, the manufacturing specification limit, and the like.

  The tip end portion of the slot die 18 is formed in a tapered shape, and the tip end is called a lip land 16. The lip land 16 on the web upstream side (lower side in FIG. 1) of the slot 24 is referred to as upstream lip land 16A, and the lip land 16 on the downstream side (upper side in FIG. 1) is referred to as downstream lip land 16B. The slot die 18 of the present embodiment has an over bite structure, and the downstream lip land 16B is disposed closer to the web 14 wound around the backup roller 12 than the upstream lip land 16A. Such an over bite structure is formed substantially uniformly over the entire length of the slot die 18 in the web width direction.

  The distance between the lip land 16 which is the coating liquid discharge tip of the slot die 18 and the web 14 is referred to as “lip clearance”. In particular, in the case of the overbite structure as in the present embodiment, the “lip clearance” means the distance between the downstream lip land 16 </ b> B closer to the web 14 and the web 14.

  A coating liquid tank 44 is connected to the coating liquid supply path 25 of the slot die 18 via a coating liquid supply pipe 46, and a gear pump 42 is provided in the coating liquid supply pipe 46. The coating liquid tank 44 is a tank that stores the coating liquid discharged from the slot die 18 toward the web 14. The gear pump 42 sends the coating solution in the coating solution tank 44 to the manifold 22 via the coating solution supply pipe 46 and the coating solution supply path 25.

  The manifold 22 is a liquid reservoir that spreads the coating liquid supplied from the coating liquid tank 44 to the slot die 18 in the coating width direction (web width direction). The cross-sectional shape of the manifold 22 is not limited to the substantially circular shape shown in FIG. 1, and may be, for example, a semicircular shape, a rectangular shape such as a trapezoid, or a similar shape.

  The slot 24 constitutes a narrow flow path for coating liquid from the manifold 22 to the tip of the slot, and coating width regulating plates (not shown) for regulating the coating width are inserted at both ends of the slot 24 in the web width direction. The In the slot 24, the coating liquid is discharged from the opening 24 </ b> A at the tip of the slot die 18, and the bead 20 is installed between the slot die 18 and the web 14.

  A decompression chamber 26 for decompressing the web upstream side of the bead 20 is provided below the front end portion of the slot die 18 having the above-described configuration. The decompression chamber 26 includes a back plate 26A, a side plate 26B, a rear plate 26C, and a bottom plate 26D that form a space therein, and has a box shape for maintaining operating efficiency related to decompression.

  The back plate 26 </ b> A is located on the most upstream side in the web conveyance direction in the decompression chamber 26, and is disposed along the width direction of the web 14. The side plate 26 </ b> B is disposed so as to be perpendicular to the back plate 26 </ b> A to constitute both side walls of the decompression chamber 26, and an edge portion (not shown) adjacent to the backup roller 12 has substantially the same curvature as the backup roller 12. The rear plate 26C is disposed below the slot die 18 and substantially parallel to the back plate 26A. The bottom plate 26D constitutes the bottom portion of the decompression chamber 26 and is joined to the back plate 26A, the side plate 26B, and the rear plate 26C at the edge portion. A gap of a predetermined size exists in each of “between the back plate 26A and the web 14” and “between the side plate 26B and the web 14”.

  A suction port 40 is formed in the back plate 26 </ b> A, and an air pipe 28 is connected to the suction port 40. A blower 30 is connected to the decompression chamber 26 via a suction port 40 and an air pipe 28, and a valve 32 and a buffer device 34 are provided in the middle of the air pipe 28. The blower 30 sucks the inside of the decompression chamber 26 through the suction port 40 and the air pipe 28 to make the inside of the decompression chamber 26 have a negative pressure. The valve 32 adjusts the degree of decompression in the decompression chamber 26 according to the opening degree. The buffer device 34 serves as a buffer unit for reducing the pressure fluctuation in the decompression chamber 26.

  A pressure gauge 36 for measuring the pressure in the decompression chamber 26 is provided in the decompression chamber 26, and the measurement result of the pressure gauge 36 is sent to the controller 38. The controller 38 adjusts the opening degree of the valve 32 based on the measurement result of the pressure gauge 36, and maintains the pressure in the decompression chamber 26 at a predetermined pressure. In the present embodiment, “pressure in the decompression chamber 26” corresponds to “pressure upstream of the web of the bead 20”.

  Next, a manufacturing example, an assembly example, and the like of the slot die 18 for discharging the coating liquid with high accuracy will be described.

  The upstream die block 18A and the downstream die block 18B constituting the slot die 18 of the present embodiment have a main body portion made of stainless steel and a tip portion including the lip land 16 made of a super hard material. The upstream die block 18A and the downstream die block 18B are joined so that the main body portions and the tip portions thereof correspond to each other, thereby preventing the influence of deformation due to heat or the like.

  At the time of assembling the slot die 18, the upstream die block 18A and the downstream die block 18B are combined while monitoring the overbyte amount L with a measuring instrument such as a microscope. At the time of this assembly, it is preferable to use a surface plate with an accuracy of 3 μm or more and assemble the upstream die block 18A and the downstream die block 18B on the surface plate with the lip land 16 facing upward. .

  When the slot die 18 is held on the gantry, it is preferable that the upstream die block 18A is held by the gantry and at least one of the downstream die blocks 18B is sandwiched and held by the gantry.

  Further, when the coating liquid is discharged from the slot die 18, the temperature of the coating chamber in which the slot die 18 is installed is kept at room temperature, and the temperature of the slot die 18 is kept at almost room temperature. It is preferable to check with a measuring instrument such as a thermometer. Further, by keeping the temperature of the coating liquid supplied from the coating liquid tank 44 to the manifold 22 at room temperature, a change in the temperature of the slot die 18 can be prevented. At that time, the flow rate and temperature of the coating solution supplied from the coating solution tank 44 to the manifold 22 are measured using a flow meter and a thermometer, and the measured values are used as a heat retention device (not shown) for the coating solution tank 44. You may make it feedback.

  Next, the relationship between the gear of the gear pump 42 of the present embodiment and the liquid feeding volume of the coating liquid by the gear pump 42 (the displacement volume of the coating liquid by the gear) will be described. FIG. 2 is a side sectional view schematically showing the gear pump 42 and mainly shows a gear 48 having a plurality of teeth 50.

  The gear pump 42 has a set of gears 48 that mesh with each other. When the pair of gears 48 rotate in the gear pump 42, the coating liquid in the coating liquid supply pipe 46 is sent from the coating liquid tank 44 toward the manifold 22. Note that the shape and number of teeth 50 of the gear 48 are not limited to those shown in FIG. 2, and various shapes and numbers can be used.

  In general, the liquid pulsation caused by the gear pump is often caused by fluctuations in the displacement amount (liquid supply amount) during the rotation of the gear, and a step unevenness called a gear mark is imparted to the coating film on the web 14. May end up. The frequency of the step unevenness imparted to the coating film by the pulsation of the coating liquid almost corresponds to the number of gear steps. Therefore, from the viewpoint of precisely feeding the coating liquid by reducing the liquid pulsation, it is effective to reduce the amount of displacement per flow rate of the coating liquid by reducing the displacement (liquid feeding amount) when the gear rotates. Is.

  As a result of earnest research, the present inventor has obtained the following findings as suggested in [Examples] described below. That is, by setting the gear pump 42 so as to satisfy the following expression (1), it is possible to effectively suppress the liquid-feed pulsation of the coating liquid and prevent unevenness imparted to the coating film.

V / N ≦ 0.07cc (1)
V: Volume of coating liquid fed per rotation of gear 48 (displacement volume)
N: Number of teeth 50 included in the gear 48 In the above formula (1), “V / N” indicates a liquid feeding volume (a displacement volume) of the coating liquid per one tooth 50 of the gear 48. Therefore, the expression (1) defines the characteristics of the gear pump 42 so that the “liquid feeding volume of the coating liquid per tooth 50 of the gear 48” is 0.07 cc or less. In this way, by setting the “liquid feeding volume of the coating liquid per tooth 50 of the gear 48” to 0.07 cc or less, the amount of fluctuation in the liquid feeding volume of the coating liquid between the adjacent teeth 50. Can be suppressed. In particular, when the gear pump 42 sends a predetermined amount of coating liquid to the manifold 22 of the slot die 18 so that a coating liquid of 10 cc / m ² or less is applied to the web 14, the above formula (1) ) Can be effectively reduced by using the gear pump 42 satisfying (see [Example] described below).

  In order to maintain the condition of the above formula (1) for a long period of time, it is preferable that the gear 48 of the gear pump 42 be formed of a material that is strongly resistant to corrosion by an organic solvent or the like. Therefore, the gear pump 42 (gear 48) can be formed of a strong member such as stainless steel or stellite.

  The above-described matters exemplify one aspect of the present invention, and various modifications such as design changes can be added based on the knowledge of those skilled in the art, and known elements can be applied. Such various aspects can also be included in the scope of the present invention.

  For example, the web 14 and the coating liquid may include those containing various components according to the purpose. As an example, polyethylene terephthalate, polyethylene-2,6-naphthalate, cellulose diacetate, cellulose triacetate, cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyimide, polyamide and other known plastic films, paper, On the surface of a strip-shaped substrate such as various laminated papers coated with α-polyolefins having 2 to 10 carbon atoms, such as polyethylene, polypropylene, ethylene butene copolymer, etc. on paper, metal foils such as aluminum, copper, tin, etc. A material in which a preliminary processed layer is formed or various composite materials obtained by laminating them can be used as the material of the web 14.

  In addition, as a solvent for the coating solution, water, various halogenated hydrocarbons, alcohols, ethers, esters, ketones, or the like can be used alone or in combination.

  In addition, as a coating solution, an optical compensation sheet coating solution, an antireflection film coating solution, an antiglare providing liquid, a magnetic coating solution, a photographic photosensitive coating solution, a magnetic coating solution, a viewing angle widening coating solution, a surface protection solution, and an antistatic solution. Further, a lubricating coating solution, a color filter pigment solution, or other optical film coating solution can be used.

  Further, the backup roller 12, the slot die 18, and the decompression chamber 26 in the slot die coater coating system 10 may have any arrangement and configuration as long as the coating liquid can be properly coated on the web 14.

  The supply method of the application liquid to the manifold 22 may be any method as long as the application liquid can be appropriately supplied to the manifold 22 by the gear pump 42. For example, a system for supplying the coating liquid from one end side of the manifold 22, a system for supplying the coating liquid from the central portion of the manifold 22, and a stopper for preventing the coating liquid from leaking out at both ends of the manifold 22 are provided. A method of supplying a new coating solution from one end and circulating a part of the coating solution extracted from the other end to the other end can be used.

  Although the Example using the above-mentioned slot die coater type coating system 10 is described below, the present invention is not limited to the following examples.

(Preparation of coating solution)
The coating solution used in each of the following examples was prepared as follows. That is, "MEK-ST (average particle size of 10 nm to 20 nm, solid content concentration of 30% by weight) with respect to 93 g of a 6% by weight methyl ethyl ketone solution (JN-7228, manufactured by JSR Corporation) of a thermally crosslinkable fluorine-containing polymer" SiO ₂ sol dispersed in methyl ethyl ketone of the Nissan chemical Co., Ltd.) 8 g "and, with the addition of" Methyl ethyl ketone 94g ", and" cyclohexanone 6g ", stir. And the solution prepared by filtering the stirred solution with the filter (PPE-01) made from a polypropylene with a hole diameter of 1 micrometer was prepared as a coating liquid. This coating solution is used as a coating solution for an antireflection film in the optical film, and is adjusted to have a refractive index of 1.42, a viscosity of 0.5 cp, and a surface tension of 0.024 N / m. Moreover, the solution which added the thickener to this coating liquid and adjusted the viscosity to the range of 0.5-7.5 cp was prepared as a coating liquid.

(Application conditions, etc.)
In the following examples, the film thickness in the width direction (web width direction) of the coating film on the web 14 based on the data obtained by applying the coating liquid to the web 14 within the following coating conditions. Distribution is evaluated.

Application amount of coating solution 2.5 to 15 cc / m ²
Application speed of coating solution 10-50 m / min
Lip clearance 40-120 μm
Viscosity of coating solution 0.5-7.5 cp
Application width on web 0.5-1.3 m
In addition, the evaluation of the coating surface of the coating film formed on the web 14 is performed at an interval of 2 mm in the longitudinal direction of the coating film using an optical interference type film thickness measuring device (instant multi-photometry system MCPD manufactured by Otsuka Electronics Co., Ltd.). Measurement was performed by measuring 650 points at intervals of 2 mm with respect to 300 points and the width direction. And it was judged that the coating film whose film thickness distribution is 1.5% or less satisfies the quality level as a product.

(Gear pump)
As the gear pump 42, a KA-1 gear pump manufactured by Kawasaki Heavy Industries, Ltd. was used. This gear pump can appropriately adjust the liquid feeding volume (displacement volume) of the coating liquid by the gear 48.

Example 1
Tables 1 to 5 below show “application amount of application liquid”, “application speed of application liquid”, and “feeding volume (displacement volume) of application liquid per tooth 50 of gear 48” (V / N) "shows the film thickness distribution in the width direction of the coating film on the web 14 when appropriately changed. The specific coating conditions in each table are as follows: Table 1 “Coating amount 15 cc / m ² , coating speed 10 m / min” Table 2 “Coating amount 5 cc / m ² , coating speed 10 m / min Table 3 is “Application amount is 10 cc / m ² , Application speed is 10 m / min”, Table 4 is “Application amount is 15 cc / m ² , Application speed is 10 m / min”, Table 5 is “Application amount is 10 cc / M ² , and the coating speed is 10 to 50 m / min ”. In Tables 1 to 5, the coating width on the web 14 is 1.3 m, the viscosity of the coating solution is 0.8 cp, and the lip clearance is 60 μm. In addition, “X” in each table indicates “liquid feeding volume (displacement volume) (V / N) of the coating liquid per tooth 50 of gear 48”, and “None” in each table indicates a slot die. 18 indicates that the coating liquid was not sufficiently applied by 18 and reliable data could not be acquired.

As suggested by each of the above tables, when the coating amount of the coating solution is 10 cc / m ² or less, “the feeding volume of the coating solution per tooth 50 of the gear 48 (the displacement volume) ( = X) "is set to 0.07 cc or less, it was confirmed that the film thickness distribution in the width direction of the coating film can be improved. This is because the lip clearance can be set to 100 μm or more and the size of the bead 20 can be set large in a range where the coating liquid coating amount is larger than 10 cc / m ² (for example, 15 cc / m ² ). Therefore, it is considered that even if there is some fluctuation in the coating liquid feeding by the gear pump 42, the relative fluctuation value with respect to the bead becomes small and it is difficult to cause defects such as unevenness. In particular, when a coating film is generated in a thin layer region, the surface state of the coating film changes sensitively to fluctuations in the coating liquid feeding by the gear pump 42. Therefore, “per tooth 50 of the gear 48” It is considered that it is very effective to set the coating liquid feeding volume (displacement volume) (= V / N) ”to 0.07 cc or less to reduce the coating liquid feeding fluctuation as much as possible. .

  Further, as shown in Table 5, even if the application speed of the application liquid is varied within a range of 50 m / min or less, “the liquid supply volume of the application liquid per tooth 50 of the gear 48 (the displacement volume). ) (= V / N) ”is set to 0.07 cc or less, it was confirmed that the film thickness distribution of the coating film can be improved.

  Note that the reason why the coating film thickness distribution value does not become 0% even when the variation of the coating liquid feeding by the gear pump 42 is reduced is due to the vibration and decompression of the devices such as the web 14 and the slot die 18. This may be due to reduced pressure fluctuations in the chamber 26, uneven feeding, or other disturbances.

(Example 2)
Tables 6 and 7 below show "application liquid application speed", "liquid supply volume of the application liquid per tooth 50 of gear 48 (displacement volume) (= V / N)", and "lip clearance". ] Shows the film thickness distribution in the width direction of the coating film on the web 14 when appropriately changed. The specific coating conditions in each table are as follows: Table 6 “Coating amount is 10 cc / m ² and coating speed is 10 m / min”, Table 7 is “Coating amount is 10 cc / m ² and coating speed is 50 m / min. " In Tables 6 and 7, the coating width on the web 14 is 1.3 m, and the viscosity of the coating solution is 0.8 cp.

As suggested by Table 6 and Table 7 above, it was confirmed that the thickness distribution in the width direction of the coating film can be improved when the lip clearance is set to 100 μm or less. This is because setting the lip clearance to 100 μm or less makes the bead 20 extremely susceptible to flow rate fluctuations and liquid pulsation, so that the liquid volume of the coating liquid per tooth 50 of the gear 48 ( This is considered to be because the effect obtained when (V / N) is reduced is very large. In addition, when the lip clearance is set to 120 μm under the conditions shown in Table 7 (application amount is 10 cc / m ² and application speed is 50 m / min), the so-called sticking limit is exceeded and sufficient application liquid is applied. Could not be implemented.

On the other hand, when the lip clearance was set to 120 μm in Tables 6 and 7, the film thickness distribution in the width direction of the coating film did not vary much regardless of the performance of the gear pump 42. This is because, as described in the first embodiment, even if there is a slight variation in the amount of the coating liquid fed by the gear pump 42, the relative variation value with respect to the bead is small, and defects such as unevenness are unlikely to occur. it is conceivable that. In a thin layer region where the coating amount of the coating solution is 10 cc / m ² or less, the lip clearance needs to be sufficiently narrowed in order to stably crosslink the beads 20, and thus the coating amount distribution is likely to deteriorate. .

(Example 3)
Table 8 below shows the web 14 when the “viscosity of the coating solution” and the “feeding volume of the coating solution per tooth 50 of the gear 48 (displacement volume) (= V / N)” are appropriately changed. The film thickness distribution in the width direction of the upper coating film is shown. The specific coating conditions in Table 8 are as follows: “The coating amount of the coating liquid is 5 cc / m ² , the coating speed of the coating liquid is 10 m / min, the coating width on the web is 1.3 m, and the lip clearance is 60 μm”. It has become.

  As suggested by Table 8 above, when the viscosity of the coating liquid is a low viscosity of 5 cp or less, the liquid feeding volume (= V / N) of the coating liquid per tooth 50 of the gear 48 is 0. It was confirmed that the thickness distribution in the width direction of the coating film can be improved by setting the thickness to 0.07 cc. When using a high-viscosity coating liquid of 7.5 cp or more, it is necessary to narrow the lip clearance in order to improve the stability of the liquid crosslinking of the bead 20, but the coating liquid for forming the bead 20 Increasing the viscosity makes it difficult for the bead shape to change, and as a result, it becomes difficult to cause defects such as unevenness due to high viscosity of the coating liquid.

Example 4
Table 9 below shows that “application width on the web 14” is set to 0.5 m, and “liquid feeding volume (displacement volume) of the coating liquid per tooth 50 of the gear 48 (= V / N)” ] Shows the film thickness distribution in the width direction of the coating film on the web 14 when appropriately changed. The specific coating conditions in Table 9 are as follows: “The coating amount of the coating liquid is 3.5 cc / m ² , the coating speed of the coating liquid is 10 m / min, the viscosity of the coating liquid is 0.8 cp, and the lip clearance is 60 μm”. It has become.

  As suggested by Table 9 above, even when the application width is set to 0.5 m, the tooth 50 of the gear 48 is similar to the above-described Example 1 in which the application width is 1.3 m. It was confirmed that the thickness distribution in the width direction of the coating film can be improved by setting the liquid feeding volume (= V / N) per coating liquid to 0.07 cc.

As suggested in Examples 1 to 4 above, in the case of coating conditions where the coating amount of the coating solution is 10 cc / m ² or less, the lip clearance is 100 μm or less, and the viscosity of the coating solution is 5 cp or less, the gear pump 42 The liquid feed fluctuation and the liquid feed pulsation caused by the above are likely to affect the coating performance of the slot die 18 and satisfy the above formula (1). ) (= V / N) ”was confirmed to be very effective.

It is a block diagram of the slot die coater in one embodiment of this invention. It is a figure which shows the outline of the internal structure of a gear pump, and is a figure which mainly shows the gear which has several teeth.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Slot die coater, 12 ... Backup roller, 14 ... Web, 16 ... Lip land, 16A ... Upstream lip land, 16B ... Downstream lip land, 18 ... Slot Die, 18A ... upstream die block, 18B ... downstream die block, 20 ... bead, 22 ... manifold, 24 ... slot, 24A ... opening, 25 ... coating Liquid supply path, 26 ... decompression chamber, 26A ... back plate, 26B ... side plate, 26C ... rear plate, 26D ... bottom plate, 28 ... air piping, 30 ... Blower, 32 ... Valve, 34 ... Buffer device, 36 ... Pressure gauge, 38 ... Controller, 40 ... Suction port, 42 ... Gear pump, 44 ... The coating liquid tank, 46 ... coating liquid supply pipe, 48 ... gear, 50 ... teeth

Claims (6)

A coating liquid is supplied to the slot die by a gear pump having gears, and the coating liquid is discharged from the slot die toward the surface of the support that continuously runs in a state of being supported by the backup roller, and the slot die and the support In the coating liquid coating method, the bead of the coating liquid is laid between and the coating liquid is coated on the surface of the support by the bead.
The gear pump supplies the coating liquid to the slot die so that the coating liquid is applied from the slot die to the support at a coating amount of 10 cc / m ² or less,
V / N ≦ 0.07cc
V: Volume of the coating liquid fed per rotation of the gear N: A coating liquid coating method that satisfies the number of teeth of the gear.   The coating liquid coating method according to claim 1, wherein a distance between the coating liquid discharge tip of the slot die and the support is 100 μm or less.   The coating solution coating method according to claim 1 or 2, wherein the coating solution has a viscosity of 5 cp or less.   An optical film comprising at least one coating layer obtained by the coating liquid coating method according to claim 1.   The optical film according to claim 4, wherein the optical film is an antireflection film. A coating liquid is supplied to the slot die by a gear pump having gears, and the coating liquid is discharged from the slot die toward the surface of the support that continuously runs in a state of being supported by the backup roller, and the slot die and the support In the coating liquid coating apparatus, the bead of the coating liquid is installed between and the coating liquid is coated on the surface of the support by the bead.
The gear pump supplies the coating liquid to the slot die so that the coating liquid is applied from the slot die to the support at a coating amount of 10 cc / m ² or less,
V / N ≦ 0.07cc
V: Volume of feeding liquid of the coating liquid per one rotation of the gear N: A coating liquid coating apparatus that is set so as to satisfy the number of teeth of the gear.

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