JP2006082059A - Method and apparatus for bar coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To coat a web with a thin film without generating a coating failure such as transversely step-like nonuniformity, fluid nonuniformity, a streak, or the like, in a bar coating. <P>SOLUTION: In a bar coating apparatus 10 for coating the web 18 with a coating liquid using a cylindrical bar 20 which is supported by a bar receiving member 22 and rotated, a cross-sectional shape corresponding in a bar diameter direction in a bar support face 46 of the bar receiving member 22 is formed into a recessed shape having at least an arc part 48 receiving the bar 20, and if the radius of the bar 20 denotes R1, the radius of curvature of the arc part 48 of the bar support face 46 denotes R2, a hold angle holding the bar 20 among the bar support face 46 denotes θ1, a bar support face area angle made by a virtual line 56 which links the center 52 of a virtual circular form 50 having a curvature of R2 with both edges 54 and 54 of the bar support face 46 denotes θ2 and a distance from the outer periphery of the virtual circular form 50 among the virtual line 56 to the edge 54 denotes Δ, the equation expressed by 40°≤θ1<θ2≤180°, 1.01≤R2/R1≤1.20 and Δ≥0.03 mm is satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bar coating method and apparatus, and more particularly to a bar coating method and apparatus for coating a coating liquid on a continuously running web with a thin cylindrical bar having a diameter of 5 mm to 15 mm.

Various methods have been proposed as methods for applying a coating solution to a continuously running web. However, as disclosed in Japanese Examined Patent Publication No. 58-4589, etc., operation is easy and a large space is required. A bar coating method that does not require is widely used. However, since the bar is elongated, stepwise coating thickness unevenness (hereinafter referred to as stepwise unevenness) easily occurs in the running direction of the web due to slight vibrations of the web and the bar. In Document 1, when the wrap angle of the web and the bar is 2.5 to 30 °, the maximum diameter of the bar section is Rb, and the radius of curvature of the arc of the bar receiving section of the bar support member is Rh, A bar coating method has been proposed in which Rb / Rh is in the range of 0.9 to 1.0 and the bar holding angle of the bar support member is 90 ° to 180 °. Thereby, stepped unevenness can be solved.
Japanese Patent Laid-Open No. 9-201563

  However, even if the bar coating method of Patent Document 1 is used, the unevenness of the horizontal step appearing in the width direction of the web generated in one rotation cycle of the bar on the surface of the coating film coated with the coating liquid on the web. There is a problem in that coating failure such as discontinuous flow unevenness caused by flow and vertical stripes appearing linearly in the longitudinal direction (conveying direction) of the web may occur. In particular, in a thin film coating having a wet film thickness of 15 μm or less applied to a web, such as coating in the production of an optical functional film such as an optical compensation film, it is difficult to obtain a leveling effect after coating. A coating failure is easily manifested and becomes a problem.

  The present invention has been made in view of such circumstances, and in bar coating, a coating solution can be applied to a web in a thin film so as not to cause a coating failure such as horizontal step unevenness, flow unevenness, and vertical stripes. Therefore, an object of the present invention is to provide a bar coating method and apparatus suitable for the production of an optical functional film, for example.

  The inventor has obtained the following knowledge as the cause of application failure such as horizontal unevenness, flow unevenness, and vertical stripes in bar coating. That is, both ends of the bar in the bar coating are rotatably supported by the bearings, and the bar is supported by the bar support surface having a concave cross section of the bar receiving member so that the bar is not easily bent. However, when the coating solution is applied to a continuously running web with a bar, the bar does not rotate in a complete circle around its axis, but the web wraps around the bar and vibrates. The bar swings (rotates while swinging) due to slight deflection of the bar. In particular, when the bar diameter is made as thin as 5 to 15 mm for thin film coating, the swinging of the bar tends to occur. It has been found that the above-mentioned coating failure occurs due to the whirling and the bar hitting the edge of the bar support surface due to the whirling. In order to prevent these coating failures from occurring, the bar support surface of the bar receiving member has a shape having a specific relationship with the bar, thereby ensuring the holdability of the bar with respect to the bar support surface and swinging. It was found that the problem can be solved by making it difficult for the bar to hit the edge of the bar support surface by turning. The present invention has been made based on such findings.

  In order to achieve the object, the bar coating apparatus according to claim 1 of the present invention applies a coating liquid to a continuously running web by using a cylindrical bar that is supported by a bar receiving member and rotates. In the coating apparatus, the cross-sectional shape corresponding to the bar radial direction of the bar support surface that supports the bar of the bar receiving member is formed in a concave shape having at least an arc portion that receives the bar, and the bar is not rotated. When supported on the bar support surface in a state, the radius of the bar is R1, the radius of curvature of the arc portion of the bar support surface is R2, and the hold angle of the bar support surface that holds the bar is θ1, the bar support surface area angle formed by the virtual straight line connecting the center of the virtual circle having the curvature of R2 and both edges of the bar support surface is θ2, the outer circumference of the virtual circle of the virtual straight lines When the distance from the edge to the edge is Δ, 40 ° ≦ θ1 <θ2 ≦ 180 ° Equation 1, 1.01 ≦ R2 / R1 ≦ 1.20 Equation 2, Δ ≧ 0.03 mm, Equation 3 The bar support surface is formed so as to satisfy all requirements.

  Here, the hold angle θ <b> 1 is a straight line drawn from the center of an imaginary circle formed by the radius of curvature of R <b> 2 to both ends of the contact arc portion where the bar and the bar support surface are in contact with each other. Says the angle formed by. That is, it refers to the angle at which the bar is held (held) in contact with the bar support surface. An edge is a horizontal tangent that gradually rises from the center position of the bar support surface (center position of the arc portion) toward the end of the bar support surface in order. Says the switching position when switching to sleep. In other words, a convex edge is formed by switching from the rising edge of the tangent to the sleeping direction.

  According to claim 1, since the bar support surface is formed with respect to the bar so as to satisfy all of the above-described formulas 1 to 3, the coating failure such as horizontal step unevenness, flow unevenness, vertical stripe, etc. The coating liquid can be applied to the web in a thin film so as not to cause the occurrence of the problem. That is, by satisfying Expressions 1 and 2, the edge of the bar support surface can be released from the bar peripheral surface to the outside while ensuring good holdability of the bar to the bar support surface. By setting the escape distance of the edge at this time, that is, Δ to 0.03 mm or more, it is possible to prevent the bar from hitting the edge of the bar support surface due to the swinging.

  A second aspect of the present invention is characterized in that, in the first aspect, the diameter of the bar is in the range of 5 to 15 mm. This is because such a thin bar is easy to bend because it is easy to bend, and the effect of the present invention is further exhibited.

  A third aspect of the present invention is characterized in that, in the first or second aspect, a straight line extends continuously from the end of the arc portion on the bar support surface to the edge.

  Claim 3 is a preferable example of forming the bar support surface so as to satisfy the three formulas of claim 1, and the bar support surface with respect to the bar peripheral surface while enhancing the holdability of the bar to the bar support surface. As the shape of the bar support surface for effectively escaping the edge to the outside, a straight line is formed from the end of the arc portion on the bar support surface to the edge.

  A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the bar is a wire bar obtained by winding a wire around a cored bar.

  There are three types of bars used in the bar coating device: flat bar, wire bar, and grooving bar. Of these, the wire bar is the easiest to control the coating amount with the most accuracy. This is because it is preferable.

  A fifth aspect of the present invention according to the fourth aspect is characterized in that the diameter of the wire wound around the wire bar is 0.06 mm to 0.4 mm.

  A coating film having a wire diameter of 0.4 mm and a thickness of about 15 μm is formed, and application failures such as horizontal step unevenness, flow unevenness, and vertical stripes are easily manifested when such a thin film is applied. This is because it is further demonstrated. The effect of the present invention is further exhibited when the wire diameter is 0.06 mm to 0.2 mm.

  A sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the straightness in the longitudinal direction of the bar support surface is 0.2 mm or less per 1 m of the bar.

  By reducing the straightness of the longitudinal direction of the bar support surface to 0.2 mm or less per 1 m of the bar, the swing of the bar can be reduced and the holdability of the bar to the bar support surface is improved. Prevents local contact with the bar support surface.

  According to a seventh aspect of the present invention, in order to achieve the above object, the bar coating apparatus according to any one of the first to sixth aspects applies the coating liquid to the web.

  Thereby, in the bar coating, the coating solution can be applied to the web in a thin film so as not to cause a coating failure such as horizontal step unevenness, flow unevenness, and vertical stripes.

  An eighth aspect of the present invention is characterized in that, in the seventh aspect, the coating liquid is applied to the web so as to have a wet thickness of 15 μm or less by the bar coating device.

  Application troubles such as horizontal unevenness, flow unevenness, and vertical stripes are easily manifested when a thin film is applied to the web so that the wet thickness is 15 μm or less. The effect of the present invention is effective in such thin film application. This is because it is further demonstrated.

  According to the bar coating method and apparatus of the present invention, a coating solution can be applied to a web in a thin film so as not to cause a coating failure such as horizontal unevenness, flow unevenness, and vertical stripes. Therefore, the present invention is extremely effective in improving the surface property of the coating film surface in thin film coating, for example, in the production of an optical functional film.

  Hereinafter, preferred embodiments of a bar coating method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a side sectional view of a bar coating apparatus showing an embodiment of the present invention, and FIG. 2 is a perspective view showing a part of a bar coating head in section.

  As shown in FIGS. 1 and 2, the bar coating apparatus 10 is configured such that the web 18 is barbed by a pair of outer guide rollers 14 and 16 provided on the upstream side and the downstream side in the web running direction with the bar coating head 12 interposed therebetween. The coating liquid is applied in a state of being wrapped by the bar 20 of the coating head 12.

  The bar coating head 12 is mainly provided over the entire length of the bar 20 rotatably supported by bearings (not shown) at both ends, and prevents the bar 20 from being bent and applies the coating liquid to the bar 20. A bar receiving member 22 having a function as a liquid feeder to be supplied, and an upstream weir member 28 and a downstream weir member 30 that form liquid supply paths 24 and 26 for coating liquid between the bar receiving member 22 and Composed. The liquid supply paths 24 and 26 are constituted by a manifold 32 and a slot 34, and the coating liquid supplied to the manifold 32 is uniformly pushed out in the width direction of the web 18 through the slot 34. As a result, a primary bead 36 is formed on the upstream side (hereinafter referred to as the primary side) of the web 18 in the conveying direction of the web 18, and the secondary side is formed on the downstream side (hereinafter referred to as the secondary side). A bead 38 is formed. The secondary bead 38 acts so as not to entrain air between the bar 20 and the bar receiving member 22. The coating liquid forming the primary and secondary beads 36 and 38 is picked up by the rotating bar 20 and applied to the web 18 that wraps around the bar 20 and runs continuously. In addition, of the coating liquid supplied from the liquid supply paths 24 and 26 to the primary and secondary beads 36 and 38, excess coating liquid flows down the outsides 28 </ b> A and 30 </ b> A of the weir members 28 and 30.

  The rotation of the bar 20 may be either the case where the web 18 is driven to rotate by the traveling of the web 18 or the case where the driving source is provided for the rotational driving. It may be a rotation in the direction. As the type of the bar 20, a wire bar or a grooving bar can be preferably used. A thin film having a wet film thickness of 15 μm or less applied to the web 18 as in the production of an optical functional film such as an optical compensation film. For coating, the wire bar 20 is easy to control the coating amount with high accuracy and is suitable for thin film coating. As shown in FIG. 3, the wire bar 20 is created by winding a wire 42 around the surface of a cylindrical cored bar 40 to form a wire row 44. As shown in FIG. 4, the wire bar 20 can change the amount of the coating liquid retained between the wires 42 of the wire row 44 by changing the thickness of the wire 42, and thereby the coating film having a desired thickness. Can be applied with high accuracy.

As shown in FIG. 5, the cross-sectional shape corresponding to the bar radial direction of the bar support surface 46 that supports the bar 20 of the bar receiving member 22 is formed into a concave shape having at least an arc portion 48 that receives the bar 20. When the bar is supported on the bar support surface 46 without rotating, the radius of the bar 20 is R1, the radius of curvature of the arc portion 48 of the bar support surface 46 is R2, and the bar 20 of the bar support surface 46 is held. The bar support surface region angle formed by virtual straight lines 56 and 56 connecting the center 52 of the virtual circle 50 having the curvature of θ1 and R2 and both edges 54 and 54 of the bar support surface 46 is θ2 and the virtual straight line 56 , 56, when the distance from the outer periphery of the virtual circle 50 to the edges 54, 54 is Δ,
40 ° ≦ θ1 <θ2 ≦ 180 ° Formula 1
1.01 <= R2 / R1 <= 1.20 ... Formula 2,
Δ ≧ 0.03 mm The bar support surface 46 is formed on the bar 20 so as to satisfy all of the formula 3.

  Here, the hold angle θ1 is a contact arc portion where the bar 20 and the bar support surface 46 come into contact with each other from the center 52 of the virtual circle 50 formed by the radius of curvature of R2 in the arc portion 48 of the bar support surface 46. The angle formed between the straight lines 58 and 58 drawn down at both ends. That is, it refers to the angle at which the bar 20 is held (held) in contact with the bar support surface 46. The edge 54 is a horizontal line at the center position 60 when a tangent line is drawn sequentially from the center position 60 (center position of the arc portion) of the bar support surface 46 toward the end of the bar support surface 46. The tangent line gradually rises and refers to the switching position when switching to the sleeping direction. In other words, a convex edge is formed by switching from the rising edge of the tangent to the sleeping direction. The definition of the edge 54 will be described in detail with reference to FIGS. Reference numeral 62 denotes the center of the bar 20.

  FIG. 6 is a preferred example of forming the bar support surface 46 so as to satisfy the above three formulas 1 to 3. The bar support surface 46 is continuously extended from both ends of the arc portion 48 to the edge 54. The straight line portion 64 having a length L is formed. Thus, by forming the bar support surface 46 with the arc portion 48 and the straight portion 64, the hold angle θ1 for holding the bar 20 on the bar support surface 46 by the arc portion 48 can be increased, and the arc portion 48 is continuous. The straight portion 64 that makes it easy to allow the edge 54 to escape outward from the outer periphery 20 </ b> A of the bar 20. The length L of the straight line is a length that allows Δ to be 0.03 mm or more. The boundary 66 between the arc portion 48 and the straight portion 64 is preferably positioned closer to the edge 54 than the region of the hold angle θ1. Thereby, an obtuse corner (edge) that contacts the bar 20 is not formed at the boundary 66 between the arc portion 48 and the straight portion 64.

  Further, when the bar support surface 46 is formed by the arc portion 48 and the straight portion 64, as shown in FIG. 6, the tangent line transitions in a direction in which the tangent line gradually rises as shown in FIG. And overlap. And it switches from the standing | starting-up | rise to the direction which lies at the tangent 6 which touches an edge surface. Therefore, the intersection of the tangent line 5 and the tangent line 6 becomes the edge 54 on the right side (right side in FIG. 6) of the bar support surface 46. Similarly, the edge 54 on the left side (right side in FIG. 6) of the bar support surface 46 is a position where the tangent rises and switches to the sleeping direction.

  The straightness in the longitudinal direction of the bar support surface 46 is preferably 0.2 mm or less per 1 m of the bar, and more preferably 0.1 mm or less.

  Next, a coating method for coating the web 18 with a coating solution using the bar coating apparatus 10 configured as described above will be described.

  The coating liquid is supplied into the liquid supply paths 24 and 26 of the coating head 12 to form primary and secondary beads 36 and 38, which are picked up by the rotating bar 20 and applied to the web 18. At this time, the coating liquid is measured at the contact portion between the web 18 and the bar 20, and only a desired coating amount is applied to the web 18, and the others flow down along the outer surfaces of the weir members 28 and 30. That is, in the bar coating, the coating solution is applied to the web 18 through the beads 36 and 38.

  In order for the coating liquid to form and maintain the beads 36 and 38, the coating liquid amount Q1 picked up by the bar 20 is equal to or larger than the coating liquid amount Q2 applied to the web 18. It is required to be. In general, when Q1> Q2, the input of the coating liquid to the primary bead 36 is larger than the output. Therefore, when the size of the primary bead 36 is kept constant, this excess coating liquid is 1 It flows out of the secondary bead 36. That is, a part of the excessive coating liquid scraped off by the bar 20 overflows over the dam member 28 and flows down along the outer surface of the dam member 28. The coating solution overflowing and flowing in this way is collected and reused again as the coating solution.

  Also, if the rotation of the bar 20 becomes too large, depending on the type of coating liquid, bubbles may stay near the downstream contact portion between the bar 20 and the web 18 and a coating failure may occur. This bubble is considered to be generated by the air existing between the bar 20 and the bar receiving member 22 being entrained by the rotation of the bar 20, and in order to prevent this, as shown in FIG. Even on the side, the coating liquid is supplied toward the bar 20 and is allowed to overflow from the weir member 30 to form a secondary bead 38 for preventing bubbles so that air is not caught up to the upstream side. preferable.

  In such bar coating, in the present invention, the bar support surface 46 is formed with respect to the bar 20 so as to satisfy all of the above-described formulas 1 to 3, so that horizontal step unevenness, flow unevenness, vertical stripes are formed. A coating solution can be applied to the web 18 in a thin film so that a coating failure such as the above does not occur. That is, it is necessary to satisfy 40 ° ≦ θ1 <θ2 ≦ 180 ° according to Equation 1. This is because by making the bar support surface region angle θ2 larger than the hold angle θ1, the shape of the bar support surface 46 can secure the distance between the bar peripheral surface and the edge 54, and the hold angle θ1 exceeds 40 °. Large and not exceeding 180 °. When the hold angle θ1 is less than 40 °, the holdability of the bar 20 to the bar support surface 46 is deteriorated, and the bar 20 is easily swung around. Conversely, when the hold angle θ1 exceeds 180 °, the edge 54 of the bar support surface 46 approaches the bar circumferential surface direction, and it is difficult to secure the distance Δ. It becomes easy to hit.

  Further, according to the formula 2, it is necessary to satisfy 1.01 ≦ R2 / R1 ≦ 1.20. In order to secure the distance Δ between the bar peripheral surface and the edge, the bar 20 is supported by the bar support surface 46, and it is necessary that R2 / R1 is 1.01 or more, and R2 / R1 is If it exceeds 1.20 and becomes too large, Δ will be easily increased, but the holdability of the bar 20 with respect to the bar support surface 46 will deteriorate. As a result, when the bar 20 swings, the bar 20 easily climbs the bar support surface 46 and hits the edge 54.

  Further, according to Equation 3, Δ ≧ 0.03 mm needs to be satisfied. This Δ = 0.03 mm means that the bar 20 does not hit the edge 54 when the bar 20 swings after securing the holding property to the bar support surface 46 of the bar 20 according to the above formulas 1 and 2. This is the minimum distance required.

  As a specific example, as shown in FIG. 6, by forming a straight line portion 64 that is continuous with a downwardly projecting circular arc portion 48 that holds the bar 20, good holdability for the bar support surface of the bar 20 is ensured. In addition, a distance Δ of 0.03 mm or more can be secured between the bar outer periphery and the edge 54, and the edge 54 can escape to the outside. As a result, in the bar coating, the coating liquid can be applied to the web 18 in a thin film so as not to cause a coating failure such as horizontal step unevenness, flow unevenness, and vertical stripes.

  Furthermore, when the bar support surface 46 satisfying the above formulas 1 to 3 is formed, a wedge-shaped space 72 is formed between the bar 20 and both ends of the bar support surface 46 to prevent the above-mentioned coating failure. It is thought to be a cause to do. That is, the wedge-shaped space 72 makes it easy for the coating liquid of the beads 36 and 38 to flow between the bar 20 and the bar support surface 46, thereby forming a lubricating film between the bar 20 and the bar support surface 46. It is inferred that this lubricating film allows the bar 20 to rotate smoothly and reduces the swirl.

  Further, by setting the straightness of the bar support surface 46 to 0.2 mm or less per 1 m of the bar, more preferably 0.1 mm or less, the rotating bar 20 can be moderated from hitting the bar support surface 46 locally, Thereby, generation | occurrence | production of application | coating failure can be suppressed further. Further, a combined effect of this straightness and the above-described lubricating film can be expected.

  In the present invention, the coating liquid used is not particularly limited, and water or an organic solvent liquid of a polymer compound, a pigment aqueous dispersion, a colloidal solution, and the like can be used. The physical properties of the coating solution are not particularly limited, but a lower viscosity is suitable, and a coating solution of 100 cp or less, particularly 50 cp or less is suitable. The surface tension is not particularly limited, but particularly preferable results can be obtained at 50 dyne / cm or less.

  The web 18 used in the present invention includes paper, plastic film, resin-coated paper, synthetic paper, and the like. Examples of the plastic film material include polyolefins such as polyethylene and polypropylene, vinyl polymers such as polyvinyl acetate, polyvinyl chloride, and polystyrene, polyamides such as 6,6-nylon and 6-nylon, polyethylene terephthalate, polyethylene-2, Polyester such as 6-naphthalate, cellulose acetate such as polycarbonate, herulose triacetate and cellulose diacetate are used. The resin used for the resin-coated paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto. The thickness of the web is not particularly limited, but a thickness of about 0.01 mm to 1.0 mm is advantageous from the viewpoint of handling and versatility.

  The bar 20 used in the present invention may be either a wire bar or a grooving bar. When a wire bar is used in the present invention, the diameter of the bar 20 is 5 mm to 15 mm, preferably 5 mm to 10 mm. The diameter of the bar 20 used in the present invention is a narrow diameter in the range of 5 to 15 mm, and a length of 2 m or less is used. This is because, since the bar 20 is elongated, the runout due to the deflection is likely to occur when the bar 20 rotates. Further, if the bar 20 has a diameter of less than 5 mm, it will be difficult to manufacture. The diameter of the wire 42 is 0.06 to 0.4 mm, preferably 0.06 to 0.2 mm. If it is larger than this, the coating amount becomes too large, which is not suitable as a method of using a bar coating method effective for high-speed thin film coating, and if it is smaller than this, it is difficult to produce a high-precision wire bar by winding the wire 42. The problem also comes out in strength. A metal is used as the material of the wire 42, but stainless steel is most suitable in terms of corrosion resistance, wear resistance, strength, and the like. In order to further improve the wear resistance, the surface of the wire 42 can be plated. Hard chrome plating is particularly suitable.

  Thus, a thin coating film having a wet thickness of 5 to 15 μm is obtained by applying a coating solution having a viscosity of 2 cP to the web 18 with a wire bar having a bar diameter of 5 mm to 15 mm and a wire diameter of 0.06 to 0.4 mm. be able to.

  Moreover, also when using a grooved bar in this invention, the diameter of a bar is 5 mm-15 mm, Preferably it is 5 mm-10 mm. The pitch of the grooves is 0.1 to 0.5 mm, preferably 0.2 to 0.3 mm, and the cross-sectional shape is particularly suitable that approximates a sine curve. However, it is not necessarily limited to such a cross-sectional shape, and other cross-sectional shapes can also be used. In general, the grooving bar and the wire bar have a certain correspondence relationship, and are the same under the same conditions when the area per unit length between the chambers below the line connecting the tops of the protrusions in the cross section is the same. It is said that it is suitable for application of a coating amount. Therefore, based on such a correspondence, an appropriate sliced bar can be selected based on the knowledge in the wire bar. The material of the bar 20 is preferably a metal from the viewpoint of corrosion resistance and strength, and stainless steel is particularly suitable. As the material of the grooving bar, metal, particularly stainless steel, is suitable in terms of corrosion resistance, strength and wear resistance.

  Since the bar 20 rotates at a high speed, the bar receiving member 22 must be made of a material having a small frictional resistance with the bar (wire in the case of a wire bar) 20. Examples of the material of the bar receiving member 22 preferably used in the present invention include a fluororesin, a polyacetal resin, a polyethylene resin, a polystyrene resin, and the like. Among these, the name is Teflon (trade name of DuPont, USA). A polyacetal resin known under the name of known polytetrafluoroethylene or Delrin (trade name of DuPont, USA) is particularly suitable in terms of friction coefficient and strength. Furthermore, what added fillers, such as glass fiber, a graphite, disulfide morbuden, to these plastic materials can also be used. Further, after the bar receiving member 22 is made of a metal material, the surface of the bar receiving member 22 may be coated or pasted with the plastic material as described above to reduce the coefficient of friction with the bar 20. Alternatively, a bar support member made of various metal materials impregnated with a plastic material as described above, for example, aluminum impregnated with polytetrafluoroethylene can be used.

  In the present invention, the appropriate size of the beads 36 and 38 varies depending on each condition. This is due to the physical properties such as the viscosity of the coating liquid, the structure and rotational speed of the bar 20, and the traveling speed of the web 18. Therefore, it is not so meaningful to define the size of the beads 36 and 38. It is practical to consider how to select these parameters that can be controlled. How to select these conditions should be determined by experiment after all since a plurality of parameters are complicatedly entangled, but generally speaking, the rotational peripheral speed Vb of the bar 20 and the web 18 are determined. The relative ratio Vb / Vw of the running speed Vw is 1. When this relative ratio is 1, the limit speed of Vw in coating is such that the viscosity of the coating solution decreases and the bar diameter decreases. Although it tends to increase, the decrease in the density of the coating liquid aimed at lowering the viscosity and the reduction in the diameter of the bar will cause deterioration of drying unevenness and swirling of the bar. An optimized combination is required.

  FIG. 7 shows an optical compensation sheet production line 80 incorporating the bar coating apparatus 10 of the present invention.

  As shown in FIG. 7, the optical functional film production line 80 is fed out of a web 18 that is a transparent support on which a polymer layer for forming an alignment film is formed in advance from a feeder 82. Next, the web 18 is guided by the guide roller 84 and fed into the rubbing processing device 86, and the rubbing roller 88 performs the rubbing processing on the polymer layer. A dust remover 90 is provided downstream of the rubbing roller 88 to remove dust adhering to the surface of the web 18. A bar coating head 12 of the present invention is provided downstream of the dust remover 90, and a coating liquid containing disconematic liquid crystal is applied to the web 18. A drying zone 92 and a heating zone 94 are sequentially provided downstream of the coating head 12, and the coating liquid on the web 18 is dried and heated to form a liquid crystal layer. Further, an ultraviolet lamp 96 is provided on the downstream side, and the liquid crystal is cross-linked by ultraviolet irradiation to form a desired polymer. As a result, an optical compensation film is manufactured, and the manufactured optical compensation film is wound around the winder 98.

Example 1
An optical compensation film was produced under the following conditions by the optical compensation film production line 80 incorporating the bar coating apparatus 10 of the present invention shown in FIG.

The web 18 was coated on a surface of 100 μm thick triacetyl cellulose (Fujitack, manufactured by Fuji Photo Film Co., Ltd.) with a 2 wt% solution of long-chain alkyl-modified poval to give 25 ml per 1 m ² of film. What dried at 1 degreeC for 1 minute and formed the resin layer for alignment films was used. While this web 18 was sent out from the delivery device 82 and conveyed at 50 m / min, the rubbing treatment device 86 rubbed the surface of the alignment layer resin layer to form an alignment film. The pressing pressure of the rubbing roller 88 in the rubbing treatment was 10 kgf / cm ² per 1 cm ² of the alignment film resin layer, and the rotational peripheral speed was 5.0 m / second.

そして、真直度がバー１ｍ当たり０．１ｍｍのバー支持面４６に、バー径８ｍｍ及びワイヤー径０．０６ｍｍのワイヤーバー２０を支持すると共に、ウエブ１８を走行速度２０ｍ／分で走行させながらワイヤーバー２０も同速で順回転させ、バー塗布ヘッド１２から塗布液をウエブ１ｍ² 当たり５ｍｌ（湿潤膜厚５μｍ）になるように配向膜上に塗布した。 And the coating liquid was apply | coated using the bar coating apparatus 10 of this invention on the orientation film obtained by rubbing the resin layer for orientation films. The coating solution was ethylene oxide-modified trimethylolpropane triacrylate (V # 360, Osaka Organic Chemical Co., Ltd.) with respect to a 4: 1 mixture of R (1) and R (2) by weight ratio of the discotic compound TE-8 shown below. Science Co., Ltd.) 10% by weight, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.6% by weight, photopolymerization initiator (Irgacure 907, Nippon Ciba Geigy Co., Ltd.) 3% 1% by weight of a sensitizer (Kayacure DET-X, manufactured by Nippon Kayaku Co., Ltd.) was added and finally a 32% by weight methyl ethyl ketone solution of the mixture was obtained. To the liquid containing the liquid crystal compound, 0.3% by weight of a fluorosurfactant (fluoroaliphatic group-containing copolymer, Megafac F780, manufactured by Dainippon Ink Co., Ltd.) is added and used as a coating liquid. did.

And while supporting the wire bar 20 having a bar diameter of 8 mm and a wire diameter of 0.06 mm on a bar support surface 46 having a straightness of 0.1 mm per 1 m of the bar, the wire bar is allowed to travel while the web 18 is traveling at a traveling speed of 20 m / min. No. 20 was also rotated forward at the same speed, and the coating solution was applied from the bar coating head 12 onto the alignment film so as to be 5 ml (wet film thickness 5 μm) per m ² of web.

  At this time, the bar support surface 46 of the bar receiving member 22 of the coating head 12 has an R2 / R1 of 1.07, a hold angle θ1 of the bar 20 on the bar support surface 46 of 74 °, and a bar support surface region angle θ2 of 102 °. The distance Δ was 0.09 mm. That is, this is a case where all the conditions of Formulas 1 to 3 required for the bar support surface 46 of the bar receiving member 22 in the present invention are satisfied.

40 ° ≦ θ1 <θ2 ≦ 180 ° Formula 1
1.01 <= R2 / R1 <= 1.20 ... Formula 2,
Δ ≧ 0.03 mm Equation 3
The web 18 coated with the coating liquid by the bar coating head 12 having the bar receiving member 22 passes through the drying zone 92 adjusted to 100 ° C. and the heating zone 94 adjusted to 130 ° C. to pass the nematic phase. Then, the surface of the liquid crystal layer was irradiated with ultraviolet rays by an ultraviolet lamp 96 while continuously transporting the web 18 coated with the alignment film and the liquid crystal compound phase. Thereby, an optical compensation film was produced.

(Example 2)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.09, the hold angle θ1 of the bar 20 on the bar support surface 46 was 68 °, the bar support surface region angle θ2 was 108 °, and the distance Δ was 0.14 mm. That is, all the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention are satisfied.

(Comparative Example 1)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.00, the hold angle θ1 of the bar 20 on the bar support surface 46 was 74 °, the bar support surface region angle θ2 was 74 °, and the distance Δ was 0 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, the definition of θ1 <θ2, the definition of 1.01 <R2 / R1 <1.20, and Δ ≧ 0.03 mm. This is a case where the edge 54 of the bar support surface 46 is in contact with the peripheral surface of the bar as shown in FIG.

(Comparative Example 2)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.00, the hold angle θ1 of the bar 20 on the bar support surface 46 was 90 °, the bar support surface region angle θ2 was 90 °, and the distance Δ was 0 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, the definition of θ1 <θ2, the definition of 1.01 <R2 / R1 <1.20, and Δ ≧ 0.03 mm. This is a case where the regulation is not satisfied, and a case where the edge 54 of the bar support surface 46 is in contact with the peripheral surface of the bar as shown in FIG. The difference between Comparative Example 1 and Comparative Example 2 is that Comparative Example 2 has larger θ1 and θ2 than Comparative Example 1.

(Comparative Example 3)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.09, the hold angle θ1 of the bar 20 on the bar support surface 46 was 180 °, the bar support surface region angle θ2 was 206 °, and the distance Δ was 0.20 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, this is a case where θ2 at 40 ° ≦ θ1 <θ2 ≦ 180 ° exceeds the upper limit of 180 °, as shown in FIG. In this case, the edge 54 of the bar support surface 46 is formed so as to protrude in the upper half of the bar 20.

(Comparative Example 4)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.09, the hold angle θ1 of the bar 20 on the bar support surface 46 was 30 °, the bar support surface region angle θ2 was 60 °, and the distance Δ was 0.12 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, this is the case where θ1 at 40 ° ≦ θ1 <θ2 ≦ 180 ° is below the lower limit of 40 °, as shown in FIG. In addition, the hold angle θ1 is extremely small.

(Example 3)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.09, the hold angle θ1 of the bar 20 on the bar support surface 46 was 120 °, the bar support surface region angle θ2 was 180 °, and the distance Δ was 0.52 mm. That is, all the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention are satisfied.

(Comparative Example 5)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.07, the hold angle θ1 of the bar 20 on the bar support surface 46 was 82 °, the bar support surface region angle θ2 was 90 °, and the distance Δ was 0.02 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, Δ ≧ 0.03 mm is not satisfied, and as shown in FIG. This is a case where a straight line portion 64 is formed at the end of the line but Δ is not sufficiently secured.

(Comparative Example 6)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.00, the hold angle θ1 of the bar 20 on the bar support surface 46 was 74 °, the bar support surface region angle θ2 was 104 °, and the distance Δ was 0.08 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, the condition is below the lower limit 1.01 of 1.01 <R2 / R1 <1.20. At first glance, it resembles FIG. 11 of Comparative Example 5, but since Comparative Example 5 has R2 / R1 of 1.07, Comparative Example 6 has R2 / R1 of 1.00. This is a case where an obtuse angle (edge) that contacts the bar 20 is formed at the boundary between the straight line portion 64 and the straight line portion 64.

(Comparative Example 7)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.40, the hold angle θ1 of the bar 20 on the bar support surface 46 was 42 °, the bar support surface region angle θ2 was 74 °, and the distance Δ was 0.19 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, the upper limit of 1.01 <R2 / R1 <1.20 is exceeded. As shown in FIG. / R1 is 1.40 and the radius R1 of the bar 20 is only about 70% of the radius of curvature R2 of the arc portion 48 of the bar support surface 46.

Example 4
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.07, the hold angle θ1 of the bar 20 on the bar support surface 46 was 60 °, the bar support surface region angle θ2 was 102 °, and the distance Δ was 0.33 mm. That is, all the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention are satisfied.

(Example 5)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.20, the hold angle θ1 of the bar 20 on the bar support surface 46 was 60 °, the bar support surface region angle θ2 was 98 °, and the distance Δ was 0.20 mm. That is, all the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention are satisfied.

(Example 6)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 is 1.01, the hold angle θ1 of the bar 20 on the bar support surface 46 is 74 °, the bar support surface region angle θ2 is 76 °, and the distance Δ from the outer periphery to the edge of the virtual circle of the virtual line is 0. 0.03 mm. That is, all the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention are satisfied.

(Comparative Example 8)
An optical compensation film was produced in the same manner as in Example 1 except that the bar support surface 46 of the bar receiving member 22 of the coating head 12 was changed as follows. R2 / R1 was 1.09, the hold angle θ1 of the bar 20 on the bar support surface 46 was 160 °, the bar support surface region angle θ2 was 190 °, and the distance Δ was 0.12 mm. That is, among the conditions required for the bar support surface 46 of the bar receiving member 22 of the present invention, θ2 at 40 ° ≦ θ1 <θ2 ≦ 180 ° exceeds the upper limit of 180 ° by 10 °. As shown in FIG. 9, the edge 54 of the bar support surface 46 is formed at a position slightly protruding from the upper half of the bar 20.

  The results of Examples 1 to 6 and Comparative Examples 1 to 8 are shown in Table 1.

(Evaluation methods)
Evaluation items are horizontal unevenness in coating unevenness generated in the width direction of the web 18 in one rotation cycle of the bar 20, discontinuous unevenness due to the flow of the coating liquid, and longitudinal direction (conveying direction) of the web 18. The straight stripes that occurred in a straight line were visually evaluated as vertical streaks.

  In the quality evaluation of the optical compensation film, a three-step evaluation is performed with a level that satisfies the manufacturing quality level as ◎, a level that satisfies the manufacturing quality as ◯, and a level that fails without satisfying the manufacturing quality as x. It was.

  The evaluation results are shown in Table 1.

表１の比較例１、２及び図８から分かるように、バー２０の半径Ｒ１とバー支持面４６の円弧部分４８の曲率半径Ｒ２が同じ場合には、距離Δが無くなってバー２０の円周面がバー支持面４６のエッジ５４に接触した状態になるので、バー２０の振れ回りによりバー２０がエッジ５４に強く接触した部分から縦スジが発生し易くなる。

As can be seen from Comparative Examples 1 and 2 in Table 1 and FIG. 8, when the radius R1 of the bar 20 and the radius of curvature R2 of the arc portion 48 of the bar support surface 46 are the same, the distance Δ disappears and the circumference of the bar 20 Since the surface is in contact with the edge 54 of the bar support surface 46, vertical streaks are likely to occur from the portion where the bar 20 is in strong contact with the edge 54 due to the swing of the bar 20.

  As can be seen from Comparative Example 3 and Comparative Example 8 and FIG. 9, when the bar support surface region angle θ2 exceeds 180 °, the edge 54 is too close to the web 18, so that flow unevenness is likely to occur. In this case, as can be seen from the comparison between Example 3 and Comparative Example 8, Example 3 in which θ2 is just 180 ° has a flow unevenness, whereas Comparative Example 8 in which θ2 is 190 ° has a flow unevenness. Since it becomes x, the upper limit of θ2 is 180 °.

  As can be seen from Comparative Example 4 and FIG. 10, when the hold angle θ <b> 1 is less than 40 °, the holdability of the bar 20 to the bar support surface 46 is deteriorated, so the swinging of the bar 20 is increased and the horizontal unevenness is increased. And vertical stripes are likely to occur. In this case, as can be seen from the comparison between Example 5 and Comparative Example 4, Example 5 in which θ1 is just 40 ° evaluates both horizontal unevenness and vertical stripes as good, but Comparative Example in which θ1 is 30 °. Since the evaluation of 4 for horizontal unevenness and vertical stripes is x, the lower limit of θ1 is 40 °.

  As can be seen from Comparative Example 5 and FIG. 11, when the distance Δ is less than 0.03 mm, vertical stripes are likely to occur. In this case, as can be seen from the comparison between Comparative Example 5 and Example 6, Example 6 with Δ of 0.03 mm has a vertical stripe evaluation of ○, whereas Comparative Example 5 with Δ of 0.02 mm Since the evaluation of the vertical stripe is x, the boundary value of Δ is 0.03 mm. That is, since Δ is affected by the swinging characteristic of the bar, in order to stably ensure good quality on the coated surface, the bar 20 does not contact the edge 54 by securing a minimum distance of 0.03 mm. It is necessary to do so.

  As in Comparative Example 6, when the ratio (R2 / R1) of the radius of curvature R2 of the arc portion 48 of the bar support surface 46 to the radius R1 of the bar 20 is less than 1.01, the bar 20 and the bar support surface 46 Contact with each other strongly, and vertical stripes are likely to occur. In this case, as can be seen from the comparison between Comparative Example 6 and Example 6, in Example 6 where R2 / R1 is 1.01, the vertical streak is evaluated as ◯, whereas R2 / R1 is 1.00. In Example 6, since the evaluation of the vertical stripe is x, the lower limit of R2 / R1 is 1.01. On the contrary, as can be seen from Comparative Example 7 and FIG. 12, when R2 / R1 exceeds 1.20 times and is excessively large, the rotation of the bar 20 becomes unstable, and horizontal unevenness is likely to occur. In this case, as can be seen from the comparison between Comparative Example 7 and Example 5, in Example 5 where R2 / R1 is 1.20, the evaluation of horizontal unevenness is ○, whereas R2 / R1 is 1.40. In Comparative Example 7, since the evaluation of the horizontal step-like unevenness is x, the upper limit of R2 / R1 is 1.20.

  FIG. 13 is not shown in Table 1, but in the conventional coating head, the shape of the bar support surface is V-shaped. Although this type has a high effect of fixing the rotational position of the bar 20, the bar 20 is strongly pressed against the bar support surface 46, and vertical stripes are likely to be generated from a portion where the bar 20 and the bar support surface 46 are in contact with each other.

  From the above test results, in the bar coating, the relationship between the bar support surface 46 of the bar receiving member 22 and the bar 20 satisfies all the following three expressions, so that horizontal step unevenness, flow unevenness, vertical stripes A coating solution can be applied to the web 18 in a thin film so that a coating failure such as the above does not occur. Therefore, the present invention is extremely effective in improving the surface property of the coating film surface in thin film coating, for example, in the production of an optical functional film.

40 ° ≦ θ1 <θ2 ≦ 180 ° Formula 1
1.01 <= R2 / R1 <= 1.20 ... Formula 2,
Δ ≧ 0.03 mm Equation 3

Side sectional view of the bar coating apparatus of the present invention The perspective view which showed a part of bar coating apparatus of this invention in the cross section Illustration of wire bar Explanatory drawing of coating liquid adjustment in wire bar Explanatory drawing explaining the relationship between the bar | burr in the coating head of the bar | burr coating apparatus of this invention, and a bar support surface. Explanatory drawing explaining an edge in case a bar support surface is comprised by a circular arc part and a linear part Explanatory drawing of the production line of the optical compensation sheet incorporating the bar coating apparatus of the present invention Sectional drawing which shows the relationship between the bar and bar support surface in Comparative Examples 1 and 2 Sectional drawing which shows the relationship between the bar and bar support surface in Comparative Examples 3 and 8 Sectional drawing which shows the relationship between the bar and bar support surface in the comparative example 4 Sectional drawing which shows the relationship between the bar | burr and bar support surface in the comparative example 5. Sectional drawing which shows the relationship between the bar and bar support surface in the comparative example 7 Sectional view of a conventional bar coating device having a V-shaped bar support surface

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Bar coating device, 12 ... Bar coating head, 14, 16 ... Guide roller, 18 ... Web, 20 ... Bar, 22 ... Bar receiving member, 24, 26 ... Liquid supply path, 28 ... Upstream weir member, 30 ... Downstream weir member, 32 ... manifold, 34 ... slot, 36 ... primary bead, 38 ... secondary bead, 40 ... core bar of wire bar, 42 ... wire, 44 ... wire row, 46 ... bar support surface, 48 ... Arc portion of the bar support surface, 50 ... Virtual circle, 52 ... Virtual circle center, 54 ... Edge, 56 ... Virtual straight line, 58 ... Line, 60 ... Center position of the bar support surface, 62 ... Bar center, 64 ... Linear part of bar support surface, 72 ... Wedge shaped space

Claims (8)

In a bar coating apparatus that applies a coating liquid to a continuously running web using a cylindrical bar that is supported by a bar receiving member and rotates,
The cross-sectional shape corresponding to the bar radial direction on the bar support surface that supports the bar of the bar receiving member is formed into a concave shape having at least an arc portion that receives the bar,
When the bar is supported on the bar support surface while not rotating, the radius of the bar is R1, the radius of curvature of the arc portion of the bar support surface is R2, and the bar of the bar support surface is The holding angle of holding is θ1, the bar supporting surface area angle formed by the virtual straight line connecting the center of the virtual circle having the curvature of R2 and both edges of the bar supporting surface is θ2, and the virtual of the virtual straight lines When the distance from the circular periphery to the edge is Δ,
40 ° ≦ θ1 <θ2 ≦ 180 ° Formula 1
1.01 <= R2 / R1 <= 1.20 ... Formula 2,
Δ ≧ 0.03 mm ... The bar coating apparatus, wherein the bar support surface is formed so as to satisfy all of the formula 3.   The bar coating apparatus according to claim 1, wherein the bar has a diameter in a range of 5 to 15 mm.   The bar coating apparatus according to claim 1, wherein a straight line is formed from an end of the arc portion on the bar support surface to the edge.   4. The bar coating apparatus according to claim 1, wherein the bar is a wire bar obtained by winding a wire around a cored bar.   The bar coating apparatus according to claim 4, wherein the wire wound around the wire bar has a diameter of 0.06 mm to 0.4 mm.   The bar coating apparatus according to any one of claims 1 to 5, wherein a straightness in a longitudinal direction of the bar supporting surface is 0.2 mm or less per 1 m of the bar.   A bar coating method, wherein the coating liquid is applied to the web by the bar coating apparatus according to claim 1. 8. The bar coating method according to claim 7, wherein a coating liquid is applied to the web so as to have a coating thickness of 15 [mu] m or less by the bar coating device.

Images