JP2005125217A - Coating head, coating device and coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating head in which bubbles existing in a coating liquid caused by generation of pin hole defect or the like are easily eliminated and a flow rate of the coating liquid becomes approximately uniform in a width direction of a web W, a coating device and a coating method. <P>SOLUTION: The coating head is used for the coating device for coating a surface of a flexible support strip continuously traveling with a coating liquid. The coating head is provided with: a liquid reservoir part 14 extending in a width direction of the support; a slit 16 communicating with the liquid reservoir part, opposed to the support in the width direction of the support and delivering the coating liquid from an opening; and feed ports provided at one end or both ends in the width direction of the support and feeding the coating liquid to the liquid reservoir part. The liquid reservoir part 14 is upwardly formed to a projection shape and the bubbles existing in the coating liquid in the liquid reservoir part can be discharged from the opening. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating head, a coating apparatus, and a coating method, and is particularly preferably used for coating a magnetic recording layer on a flexible support that is continuously supported by a traveling guide unit such as a guide roller. The present invention relates to a coating head, a coating apparatus having the coating head, and a coating method.

  Photosensitive materials and magnetic recording media are manufactured through a coating process in which a coating film is formed by coating a predetermined coating liquid such as a magnetic liquid on a continuous belt-like support (hereinafter referred to as “web”). . In particular, magnetic recording media such as magnetic recording tape have recently been rapidly improved in capacity and recording density for broadcasting and computers, have a very thin film thickness, a uniform film thickness distribution, and a smooth surface. There is a need for a coating technique that can provide a simple magnetic layer.

  In order to respond to such market demands, the applicant can effectively suppress the occurrence of color unevenness and vertical stripes, can form a coating layer with higher quality than before, and has excellent electromagnetic conversion characteristics. There has been proposed a coating apparatus (see Patent Document 1) that can manufacture a recording medium. This technique is intended to optimize the structure of the coating head (inner diameter of the liquid reservoir, slit depth, etc.) in the extrusion type coating apparatus, thereby reducing coating defects.

  7 and 8 show the above-described conventional extrusion-type coating head 1, FIG. 7 is a perspective view, and FIG. 8 is a sectional view taken along line 8-8 of FIG. The web W is supported (wound) by the backup roll 2 and transferred at a constant speed. The tip of the coating head 1 is arranged with a slight gap with respect to the surface (lower surface) of the web W.

  The coating head 1 is provided with a liquid supply system that can supply a coating liquid. That is, the main body of the coating head 1 is connected to the liquid reservoir 4 extending in the longitudinal direction (the width direction of the web W) and the liquid reservoir 4, and the web W in the longitudinal direction (the width direction of the web W). Opposite slits 6 for discharging the coating liquid from the opening, a liquid supply port 3 for supplying the coating liquid Q1 to the liquid reservoir 4, and a liquid outlet 5 for extracting the coating liquid Q2 from the liquid reservoir 4 are provided. Yes.

  The coating liquid Q1 supplied to the liquid reservoir 4 is flowed as shown by the arrow in FIG. 8, and a predetermined amount Q3 is discharged from the tip portion of the slit 6 and the remaining amount Q2 is discharged from the liquid discharge port 5. Then, it is collected in a fixed liquid feeding means.

The liquid reservoir 4 is formed with an inclination angle θ1 in consideration of pressure loss of the coating liquid so that the flow rate of the coating liquid Q3 discharged from the opening of the slit 6 is substantially uniform in the width direction of the web W. Has been.
Japanese Patent No. 2520751

  However, even the conventional techniques as described above have problems that cannot be solved. That is, in the extrusion type coating apparatus, there are pocket-like portions 7A and 7B as shown in FIG. Then, bubbles existing in the coating liquid Q stay in the pocket-shaped portions 7A and 7B, and during the manufacturing, the bubbles are mixed into the coating liquid Q3 discharged from the opening of the slit 6 and applied to the web W. Cause pinhole defects.

  Among these, the bubbles staying in the left pocket-like portion 7A are likely to be removed during the abandonment production at the start of operation (flowing the dummy web W until stable) due to the presence of the inclination angle θ1, It doesn't matter much.

  On the other hand, the bubbles staying in the right pocket-like portion 7B are difficult to be removed at the time of discarded production at the start of operation due to the presence of the inclination angle θ1, and are discharged from the opening of the slit 6 by some trigger during the production. A pinhole defect etc. will be produced. As a result, the yield decreases.

  Further, in the conventional technique described above, a configuration is adopted in which the flow rate of the coating liquid Q3 discharged from the opening of the slit 6 is substantially uniform in the width direction of the web W. Therefore, there is a demand for a technique in which the flow rate of the ink becomes substantially uniform in the width direction of the web W.

  The present invention has been made in view of such circumstances, and it is easy to eliminate bubbles present in the coating liquid that may cause pinhole defects and the flow rate of the coating liquid is determined in the width direction of the web W. It is an object of the present invention to provide a coating head, a coating apparatus, and a coating method that are substantially uniform.

  In order to achieve the above object, the present invention provides a coating head used in a coating apparatus for coating a coating liquid on the surface of a continuously running belt-like flexible support, and a liquid extending in the width direction of the support. A reservoir, a slit communicating with the reservoir in the width direction of the support and facing the support in the width direction of the support, and discharging the coating liquid from the opening, and one or both end portions in the width direction of the support And a supply port for supplying the coating liquid to the liquid reservoir. The liquid reservoir is formed in a convex shape upward, and bubbles present in the coating liquid in the liquid reservoir are formed. Disclosed is a coating head that can be discharged from the opening, and a coating method using the coating head.

  According to the present invention, the liquid reservoir is formed in an upwardly convex shape, whereby air bubbles present in the coating liquid in the liquid reservoir can be easily discharged from the opening. Therefore, pinhole defects due to bubbles do not occur, thereby improving the yield.

  In the present invention, it is preferable that the liquid reservoir has a shape in which a plurality of linear cavities are connected in the width direction of the support. In the present invention, it is preferable that the liquid reservoir is a curved cavity in the width direction of the support. In the present invention, it is preferable that the liquid reservoir is formed at an inclination angle of 0.2 degrees or more with respect to the opening edge of the slit in the width direction of the support. By adopting such a liquid reservoir configuration, the effects of the present invention can be suitably achieved.

  In the present invention, it is preferable that the liquid reservoir is formed in such a shape that the flow rate of the coating liquid discharged from the opening of the slit is substantially uniform in the width direction of the support. By adopting such a configuration, not only the effect of discharging bubbles present in the coating solution but also the effect of uniforming the thickness of the coating film can be obtained.

  In the present invention, it is preferable to use a liquid having a viscosity η of 5 P (0.5 Pa · s) or less as the coating solution. When such a low-viscosity coating liquid is used, it has been confirmed that pinhole defects due to bubbles are remarkable. Therefore, a suitable effect of the present invention can be obtained in application of such a low-viscosity coating liquid.

  As described above, according to the present invention, the liquid reservoir portion extending in the width direction of the support, the slit for discharging the coating liquid from the opening, and one or both ends in the width direction of the support are provided. In the coating head having a supply port for supplying the coating liquid to the liquid reservoir, the liquid reservoir is formed in a convex shape upward so that bubbles present in the coating liquid in the liquid reservoir are opened. It can be easily discharged from the part. Therefore, pinhole defects due to bubbles do not occur, thereby improving the yield.

  Examples of embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing a part of a coating head 10 cut out of a coating apparatus applied to the present invention. FIG. 2 is a schematic cross-sectional view showing the positional relationship between the tip portion of the coating head 10 and a flexible support (hereinafter referred to as “web”) W. The web W is set with respect to the coating head 10. The state which has apply | coated the coating liquid is shown.

  As shown in FIGS. 1 and 2, the coating head 10 is provided with the following liquid supply system capable of supplying a coating liquid. That is, the main body 12 of the coating head 10 communicates with the liquid reservoir 14 extending in the longitudinal direction (the width direction of the web W) and the liquid reservoir 14, and the web W in the longitudinal direction (the width direction of the web W). And a slit 16 for discharging the coating liquid from the opening, a liquid supply port 18 for supplying the coating liquid to the liquid reservoir 14, and a liquid outlet 20 for extracting the coating liquid from the liquid reservoir 14. Yes.

  The liquid reservoir 14 is also referred to as a “pocket” or “manifold”, and has a substantially circular cross section. As shown in FIG. 1, the liquid reservoir 14 extends with substantially the same cross-sectional shape in the width direction of the web W. It is a cavity having a function. The effective length is usually set equal to or slightly longer than the coating width. As shown in FIG. 1, both end openings through which the liquid reservoir 14 passes are closed by closing plates 22 and 24 attached to both ends of the main body 12. The liquid supply port 18 described above is provided in the closing plate 22, and the liquid discharge port 20 is provided in the closing plate 24.

  The slit 16 passes through the inside of the main body 12 of the coating head 10 with an opening width of 0.01 to 1 mm from the liquid reservoir 14 toward the web W, and the width direction of the web W is the same as the liquid reservoir 14. The opening length in the width direction of the web W is set substantially equal to the coating width. In addition, the length of the flow path toward the web W in the slit 16 can be appropriately set in consideration of various conditions such as the liquid composition of the coating liquid, physical properties, supply flow rate, supply liquid pressure, and the like. That is, it is only necessary that the coating liquid can be supplied from the slit 16 in a laminar flow with a uniform flow rate and hydraulic pressure distribution in the width direction of the web W.

  Next, the tip portion of the coating head 10 will be described with reference to FIG. The slit 16 is formed by a front edge 26 and a back edge 28 of the main body 12 (see FIG. 1) of the coating head 10. A front edge surface 26a and a back edge surface 28a are formed on the upper surface (the surface facing the web W) of the main body 12 of the coating head 10 from the upstream side.

  As shown in FIG. 2, the front edge surface 26 a has a substantially linear cross section, and the back edge surface 28 a has a mountain shape in cross section. Further, a predetermined step is provided between the rear edge portion of the front edge surface 26a and the front edge portion of the back edge surface 28a so that a film having a predetermined thickness of the coating liquid F can be formed. The cross-sectional shapes of the front edge surface 26a and the back edge surface 28a shown in FIG. 2 are merely examples, and various cross-sectional shapes such as an arc shape and a parabolic shape can be employed.

  Next, the liquid reservoir portion 14 is formed at a predetermined inclination angle with respect to the opening portion of the slit 16, so that bubbles existing in the coating liquid F in the liquid reservoir portion 14 can be discharged from the opening portion. The structure which has become is demonstrated.

  3 is a cross-sectional view taken along line 3-3 of FIG. 1 and shows the shape of the liquid reservoir 14 and the like. Among the coating heads 10 shown in FIG. 3, (a) forms the linear liquid reservoir 14 of the conventional example, and (b), (c) and (d) relate to the present invention. The liquid reservoir portion 14 has a mountain shape. Among these, (b) has a substantially trapezoidal shape, (c) has a substantially triangular shape, and (d) has an arc shape. In addition, although the linear liquid reservoir part 14 of the conventional example of (a) is formed in parallel with the opening part of the slit 16, as shown in FIG. 8, it has a predetermined inclination with respect to the opening part of the slit 6. Some are formed at an angle θ1.

  3 (b), 3 (c) and 3 (d), the liquid reservoir 14 has a predetermined inclination angle with respect to the opening of the slit 16 (opening edge in the width direction of the web W) (FIG. 3 (c)). The through holes provided in the closing plates 22 and 24 also have a shape on this extension line. Therefore, the pinhole defect etc. by a bubble are not produced like a prior art example (structure of Fig.3 (a) and FIG. 8).

  3 (b), 3 (c), and 3 (d), from another viewpoint, the distance from the boundary of the slit 16 to the liquid reservoir 14 to the opening is the web W. Thus, the distance in the vicinity of both end portions in the width direction of the web W is larger than the distance of other portions in the width direction of the web W. Therefore, with this configuration, the flow rate of the coating liquid discharged from the opening of the slit 16 becomes substantially uniform in the width direction of the web W. That is, not only the effect of discharging bubbles present in the coating solution but also the effect of uniforming the thickness of the coating film can be obtained.

  The maximum value of the distance difference (t illustrated in FIG. 3B) varies depending on various conditions such as the liquid composition, physical properties, supply flow rate, supply liquid pressure, and the like of the coating solution. The effect is obtained.

  In addition, the distance (length of the flow path toward the web W) from the boundary part with the liquid reservoir part 14 of the slit 16 to the opening part is the opening length in the width direction of the web W of the slit 16 and the coating liquid. When the opening length in the width direction of the web W of the slit 16 (L illustrated in FIG. 3C) is about 1000 to 1200 mm, although it depends on various conditions such as liquid composition, physical properties, supply flow rate, supply hydraulic pressure, etc. A range of 30 to 80 mm can be preferably used.

  Next, various materials used in the present invention will be described. As the web W, a resin film, paper (resin coated paper, synthetic paper, etc.), metal foil (aluminum web, etc.), etc. can be used. Resin film materials include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polystyrene, polycarbonate, polyamide, PET (polyethylene terephthalate), biaxially stretched polyethylene terephthalate, polyethylene naphthalate, and polyamideimide. Known materials such as polyimide, aromatic polyamide, cellulose triacetate, cellulose acetate propionate, and cellulose diacetate can be used. Of these, polyethylene terephthalate, polyethylene naphthalate, and polyamide can be preferably used.

  The width of the web W is generally 0.1 to 3 m, the length of the web W is generally 1000 to 100000 m, and the thickness of the web W is generally 0.5 to 100 μm. . However, application of other sizes is not impeded.

  These webs W may be subjected in advance to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment and the like. The surface roughness Ra of the web W is preferably 3 to 10 nm at a cutoff value of 0.25 mm.

  Further, the web W may be a web W provided with a base layer such as an adhesive layer in advance and dried and hardened, or a web with another functional layer formed in advance on the back surface.

  When a magnetic layer is formed using a coating solution containing a magnetic material, the ferromagnetic powder used in the magnetic layer is not particularly limited, but is ferromagnetic with α-Fe as a main component. Metal powder and hexagonal ferrite powder are preferred. These ferromagnetic metal powders include Al, Si, S, Sc, Ca, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta in addition to the predetermined atoms. , W, Re, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, and B atoms may be included. In particular, at least one of Al, Si, Ca, Y, Ba, La, Nd, Co, Ni, and B is preferably included in addition to α-Fe, and further includes at least one of Co, Y, and Al. preferable.

  The ferromagnetic powder may contain a small amount of hydroxide or oxide. As the ferromagnetic metal powder, those obtained by a known production method can be used, and the following methods can be mentioned. 1) a method of reducing a complex organic acid salt (mainly oxalate) with a reducing gas such as hydrogen; 2) a method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe-Co particles; 3) A method for thermally decomposing metal carbonyl compounds, 4) A method for reducing an aqueous solution of ferromagnetic metal by adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine, and 5) A method for reducing the metal under low pressure. And a method of obtaining fine powder by evaporating in an active gas.

  The ferromagnetic metal powder obtained in this manner is a known slow oxidation treatment, that is, a method of drying after being immersed in an organic solvent, and after being immersed in an organic solvent, an oxygen-containing gas is fed to form an oxide film on the surface and then dried. Any of the methods of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent can be used.

  As the liquid composition of the coating liquid, various known compositions can be selected according to the purpose.

  When a non-magnetic layer is formed by using a coating solution that does not contain a magnetic material, the nonmagnetic configuration contained in the coating solution is not limited, but usually consists of at least a resin, preferably a powder, for example, Examples include inorganic powder or organic powder dispersed in a resin. The inorganic powder is usually preferably a nonmagnetic powder, but a magnetic powder may be used as long as this layer is substantially nonmagnetic.

  The nonmagnetic powder can be selected from, for example, inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. Examples of inorganic compounds include α-alumina, β-alumina, γ-alumina, θ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, hematite, goethite, corundum, silicon nitride with an α conversion rate of 90% or more. , Titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, etc. are used alone or in combination .

The surface of these nonmagnetic powders is subjected to surface treatment, and Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , ZnO, and Y ₂ O ₃ are preferably present. Particularly preferred for dispersibility are Al ₂ O ₃ , SiO ₂ , TiO ₂ and ZrO ₂ , but more preferred are Al ₂ O ₃ , SiO ₂ and ZrO ₂ . These may be used in combination or may be used alone. In addition, a co-precipitated surface treatment layer may be used depending on the purpose, and a method of treating the surface layer with silica after first making alumina present, or vice versa may be employed. The surface treatment layer may be a porous layer depending on the purpose, but it is generally preferable that the surface treatment layer is homogeneous and dense.

  Next, the operation of the coating apparatus will be described with the coating head 10 as a main component. As shown in FIG. 1, the coating liquid F passes through a liquid supply port 18 by a constant-volume liquid feeding means that can be continuously fed at a constant flow rate, generally a quantitative pump (not shown). It is supplied to the reservoir 14. As the metering pump, for example, a flow rate variable liquid feeding means such as a plunger pump or a gear pump can be preferably used.

  A predetermined amount of the coating liquid F supplied to the liquid reservoir 14 is discharged from the opening of the slit 16, and the remaining amount is discharged from the liquid discharge port 20 and is collected by the quantitative liquid feeding means. By performing such an operation, it is possible to prevent the coating liquid F from staying in the liquid reservoir 14 significantly. Such an operation method is extremely effective for a magnetic coating solution that has thixotropic properties and easily aggregates. However, the liquid discharge port 20 may not be provided, and a predetermined amount discharged from the opening of the slit 16 may be supplied from the liquid supply port 18. Moreover, the structure which provides a liquid supply port in the both ends of the width direction of the web W, and supplies a substantially equivalent amount of coating liquid from both liquid supply ports may be sufficient. In this case, even if it is the structure which provides a liquid discharge port in another location, the structure which does not provide a liquid discharge port is possible.

  A web W that is continuously supported by a travel guide means such as a guide roller (not shown) has a substantially constant tension between each travel guide means such as a guide roller and can be bent slightly in the thickness direction. 2 and moves at a predetermined speed in the direction of the arrow in the figure while being pressed against the upper surface (the surface facing the web W) of the coating head 10 as shown in FIG. Thereby, the coating liquid F discharged from the opening of the slit 16 is applied to a predetermined thickness with a uniform flow rate and pressure distribution in the width direction of the web W.

  The traveling speed of the web W can generally be selected within a wide range of 30 to 1500 m / min, but is not limited to this range. A configuration in which a predetermined tension is applied to the web W between the respective travel guide means so that the pressure of the web W pressed against the upper surface of the coating head 10 is uniform. As the applied tension, 49 to 490 N (5 to 50 kgf) per 1 m of the width of the web W can be preferably used. This value is preferably adjusted as appropriate according to the application conditions.

  In order to realize such a coating state, as described above, traveling guide means such as guide rollers are provided on the upstream and downstream sides of the coating head 10, and the traveling guide on the surface opposite to the coating surface of the web W is guided. Wrap around the means and run. The distance between the travel guide means and the coating head 10 is preferably set to about 50 to 300 mm. In addition, it is preferable that the travel guide means be configured to be movable and adjustable in the vertical direction in FIG. 2 so that the entrance angle and the separation angle of the web W to the coating head 10 can be adjusted.

  Furthermore, in the case of the web W having low rigidity, it is also preferable to provide an expander roll, a crown roll, a concave roll, or the like in the travel path of the web W so that generation of creases can be suppressed.

  At the start of production in which coating is performed while the web W is running, first, discard production (flowing the dummy web W until it is stabilized) is performed, and at this time, bubbles present in the coating liquid in the liquid reservoir 14 Is preferably discharged from the opening of the slit 16 and then shifted to the main production.

  As mentioned above, although the example of embodiment of the coating head, the coating device, and the coating method concerning this invention was demonstrated, this invention is not limited to the example of the said embodiment, Various aspects can be taken.

  For example, in the example of the present embodiment, the extrusion coating method shown in FIGS. 1 and 2 is adopted, but not limited to such a coating method, various modes can be adopted. As an example of this, a configuration in which two extrusion coating heads of a liquid supply system capable of supplying one type of coating liquid are arranged in series, and the first coating liquid and the second coating liquid are continuously coated, A configuration in which the coating liquid is continuously applied using an extrusion coating head provided with three sets of independent liquid supply systems so that three types of coating liquids can be supplied, upstream in advance to the web W that runs continuously The first coating liquid can be applied on the side, and the second coating liquid can be applied continuously while scraping off a part of the first coating liquid at the tip edge of the coating head.

  In addition, a configuration in which the web W is wound around a backup roller and applied with a predetermined clearance between the surface of the web W and the front end surface of the coating head 10 can be employed instead of the configuration in which the web W is pressed against the coating head 10.

  Furthermore, in the example of the embodiment, the coating liquid containing a magnetic material is used as the coating liquid and the magnetic recording medium is manufactured. However, the present invention is not limited to the manufacturing of the magnetic recording medium, but for other uses. It can be widely applied to.

  Furthermore, in the example of the present embodiment, the liquid reservoir portion 14 is a cylindrical hollow portion. However, the present invention is not limited to such a cylindrical shape, and various aspects such as a square shape and a ship bottom shape can be employed. The point is that the shape is not particularly limited as long as the pressure distribution is uniform in the width direction of the web W.

  Furthermore, the configuration of the coating head 10 is not limited to the extrusion coating method, and a bar coating method, a curtain coating method, or the like can also be employed.

  Next, examples of the present invention will be described in comparison with comparative examples. In the following examples, “part” means “part by weight”. In the following examples, stock solutions a and b having the following compositions were prepared as stock solutions of coating solutions A, B and C containing a magnetic substance.

(1) Stock solution a
300 parts of ferromagnetic metal fine powder
Composition: Co-substituted Bafe
Average particle size 0.10μm
Plate ratio 8.3
Average thickness 0.03μm
Hc 660 Oe
45 parts of vinyl chloride polymer
Vinyl chloride-vinyl acetate copolymer-maleic anhydride copolymer Aluminum stearate 10 parts Lecithin 3 parts Chromium oxide 5 parts Methyl ethyl ketone 200 parts Cyclohexanone 200 parts (2) Stock solution b
100 parts of ferromagnetic metal fine powder
Composition: Fe / Zn / Ni = 92/4/4
Average long axis length 0.08μm
Needle-shaped ratio 8.0
Hc 2000 Oe
20 parts of vinyl chloride polymer
Vinyl chloride-vinyl acetate copolymer-maleic anhydride copolymer Methyl ethyl ketone 50 parts Cyclohexanone 50 parts For the above stock solutions a and b, each component was kneaded with a continuous kneader and then dispersed using a sand mill. . The obtained dispersion was filtered using a filter having an average pore diameter of 1 μm, and then adjusted by adding methyl ethyl ketone and cyclohexanone so that a desired solid content concentration was obtained.

  The coating liquids (coating liquids A to C) used for coating were set to the compositions shown in the table of FIG. Among these, about each coating liquid, viscosity (eta) was measured with the Brookfield type viscometer, and it shows in a table | surface.

As an example, the coating head 10 shown in FIGS. 1 and 2 was used to apply a coating solution to the surface of the web W, and the number of pinholes in the coating film after drying was visually evaluated. The area of the evaluated web W was unified with 5 m ² . The shape of the liquid reservoir 14 of the coating head 10 is the shape shown in FIG. 3C, and five types with different θ2 and θ3 are produced, and the shape shown in FIG. 3A (θ is 0 degree). 1) were prepared and compared.

  The cross-sectional shape of the liquid reservoir 14 is a circle having an inner shape of 10 mm, and the opening length of the slit 16 in the width direction of the web W (L illustrated in FIG. 3C) is 500 mm. Moreover, the width | variety (plate thickness) of the closing plates 22 and 24 is 25 mm. The running speed of the web W was 100 m / min, and the flow rate of the coating liquid discharged from the slit 16 was 500 g / min. The results are shown in the table of FIG.

  As a comparative example, the coating head 1 shown in FIGS. 7 and 8 was used to apply a coating solution to the surface of the web W, and the number of pinholes in the coating film after drying was visually evaluated. The evaluation method was the same as in the example. The shape of the liquid reservoir 4 of the coating head 1 was the same as that shown in FIG. 8, and three types with different θ1 were prepared and compared. Other conditions (each dimension of the coating head 1 and coating conditions) were the same as in the example. The results are shown in the table of FIG.

  Next, the comparative example of FIG. 5 and the example of FIG. 6 will be compared. First, a comparative example (Examples 11 to 13 in FIG. 5) and an example (Examples 1 to 3 in FIG. 6) using the coating liquid A composed of the stock solution a shown in FIG. 4 will be compared.

  The viscosity η of the coating liquid A is very low, and bubbles are very easily generated. In Comparative Examples 11 to 13, pinholes are generated regardless of the value of θ1 (0.1 to 0.5 degrees). On the other hand, in Example 3 of the example (θ2, θ3 is 0.1 degree), three pinholes are generated, which is not much different from the comparative example, but Example 2 (θ2, θ3 is 0.2 degree). ), One pinhole, which is somewhat more effective than the comparative example, and in Example 1 (θ2 and θ3 are 0.3 degrees), pinholes are not generated and a clear effect can be confirmed.

  Next, a comparative example (Examples 14 and 15 in FIG. 5) using the coating liquid B consisting of the stock solution b is compared with an example (Examples 4 and 6 in FIG. 6).

  The viscosity η of the coating liquid B is quite high and bubbles are unlikely to be generated. In Comparative Example 14 (θ1 is 0.3 degrees) and Example 15 (θ1 is 0.5 degrees), no pinhole is generated. Even in Example 4 of the embodiment (θ2 is 0.1 degree, θ3 is 0.15 degree), no pinhole is generated. Further, Example 6 (θ2, θ3 is 0 degree) has the same liquid reservoir shape as that of the conventional example, but no pinhole is generated. From the above, it can be said that the coating liquid B is in a state where bubbles are hardly generated, and the effect of the present invention cannot be confirmed.

  Next, a comparative example (Example 16 in FIG. 5) using the coating liquid C composed of the stock solution b and an example (Examples 5 and 7 in FIG. 6) are compared and examined.

  The viscosity η of the coating liquid C is quite low, and bubbles are easily generated. In the comparative example 16 (θ1 is 0.5 degree), six pinholes are generated. On the other hand, in Example 5 (θ2 is 0.3 degrees and θ3 is 0.25 degrees), no pinhole is generated. Further, Example 7 (θ2, θ3 is 0 degree) has the same liquid reservoir shape as that of the conventional example, but has two pinholes. When the above three are compared, the configuration of the present invention and the effect of providing a predetermined inclination (θ2, θ3) in the reservoir can be confirmed.

  From the above results, the effect of the present invention was confirmed.

The perspective view which cut | disconnects and shows a part of coating head among coating apparatuses. Schematic sectional view showing the positional relationship between the tip of the coating head and the flexible support 3-3 sectional view of FIG. Table showing composition of coating solution Table showing results of comparative examples Table showing results of examples The perspective view which cuts and shows a part of coating head of a prior art example Schematic sectional view showing the positional relationship between the tip portion of the coating head of the conventional example and the flexible support

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Coating head, 12 ... Main body, 14 ... Liquid reservoir, 16 ... Slit, 18 ... Liquid supply port, 20 ... Liquid discharge port, 22, 24 ... Closure plate, 26 ... Front edge, 28 ... Back edge, 28a ... Back edge surface, F ... coating liquid, W ... flexible support (web)

Claims (8)

In a coating head used in a coating apparatus for coating a coating liquid on the surface of a strip-like flexible support that runs continuously,
A liquid reservoir extending in the width direction of the support;
A slit that communicates with the liquid reservoir, faces the support in the width direction of the support, and discharges the coating liquid from the opening;
A supply port that is provided at one or both ends in the width direction of the support, and that supplies a coating liquid to the liquid reservoir,
The coating head is characterized in that the liquid reservoir is formed in a convex shape upward, and bubbles present in the coating liquid in the liquid reservoir can be discharged from the opening.   The coating head according to claim 1, wherein the liquid reservoir has a shape in which a plurality of linear cavities are connected in the width direction of the support.   The coating head according to claim 1, wherein the liquid reservoir is a curved cavity in the width direction of the support.   The coating according to any one of claims 1 to 3, wherein the liquid reservoir is formed at an inclination angle of 0.2 degrees or more with respect to an opening edge of the slit in the width direction of the support. head.   The said liquid reservoir part is formed in any one of Claims 1-4 in the shape where the flow volume of the coating liquid discharged from the said opening part of the said slit becomes substantially uniform in the width direction of the said support body. The coating head described.   A coating apparatus comprising the coating head according to any one of claims 1 to 5. In the coating method of coating the coating liquid on the surface of the belt-like flexible support that runs continuously,
A liquid reservoir extending in the width direction of the support;
A slit that communicates with the liquid reservoir, faces the support in the width direction of the support, and discharges the coating liquid from the opening;
A supply port that is provided at one or both ends in the width direction of the support, and that supplies a coating liquid to the liquid reservoir,
The liquid reservoir is a coating method that uses a coating head that is formed in a convex shape upward, and bubbles that are present in the coating liquid in the liquid reservoir can be discharged from the opening,
A coating method, wherein the coating liquid is applied after the bubbles present in the coating liquid in the liquid reservoir are discharged from the opening. The coating method according to claim 7, wherein a liquid having a viscosity η of 5 P or less is used for the coating liquid.

Images