JP4264887B2 - Application method - Google Patents

Description

  The present invention relates to a coating method, and more particularly to a coating method suitably used for coating a magnetic recording layer or the like on a flexible support that is supported by a travel guide means such as a guide roller and continuously travels.

  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 have been proposals such as a coating method (see Patent Documents 1 and 2) that can produce a recording medium.

This technique is to apply various devices in a coating method using an extrusion type coating apparatus, thereby reducing coating defects. Patent Document 1 discloses the timing of contact between a coating head and a web. The application is started in accordance with the above, and Patent Document 2 instantaneously sets a predetermined coating liquid flow rate when starting the application.
Japanese Patent Publication No. 6-091980 Japanese Patent Publication No. 6-009672

  However, even the conventional techniques as described above have problems that cannot be solved. That is, the conventional technique in the coating method for forming two or more coating layers is a so-called coating method in which a lower layer coating solution is applied to the surface of a continuously running web and an upper layer coating solution is applied immediately thereafter. It was a “wet on wet” method. In this method, if a disturbance occurs when the upper-layer coating solution is applied, the meniscus of the coating solution formed at the tip of the coating head is broken, which makes the coating state unstable. It was.

  In particular, when the coating start portion of the lower layer coating liquid passes through the coating head of the upper layer coating liquid at the start of coating, it becomes an upper layer due to a sudden change in thickness or drastic change in coating properties. In many cases, the meniscus of the coating solution is broken, and this causes the liquid to scrape back to the upstream portion, causing streaky coating thickness unevenness. As a result, there has been a strong demand for improvement because of problems such as a reduction in operating rate and a decrease in yield.

  The present invention has been made in view of such circumstances. In an application method for forming two or more application layers, an unstable phenomenon during application can be eliminated, the film thickness distribution is uniform, and the surface is smooth. It is an object of the present invention to provide a coating method capable of forming a simple coating layer and achieving an improvement in operating rate and yield.

In order to achieve the above-mentioned object, the present invention applies a first coating liquid to the surface of a continuously running belt-like flexible support with a first coating device and then dries the first coating liquid. A coating method comprising: forming a lower layer; and applying a second coating liquid to the surface of the lower layer with a second coating apparatus to form an upper layer. In the step of starting the application of the second coating liquid after the first coating liquid application start portion has passed through the second coating apparatus , and forming the upper layer with the second coating liquid. Provided is a coating method, characterized in that the application of the second coating liquid is terminated before the application of the first coating liquid in the lower layer of the flexible support passes through the second coating device. To do.

According to the present invention, the second coating liquid is applied to a web (flexible support) having a dried lower layer to form an upper layer. And application | coating of a 2nd coating liquid is started after the application | coating start part of a lower layer passes a 2nd coating device. Therefore, when the application of the second coating liquid is started, a stepped portion that becomes a disturbance does not pass through, and the meniscus of the second coating liquid does not break. Thereby, an unstable phenomenon at the time of application can be eliminated, an application layer having a uniform film thickness distribution and a smooth surface can be formed, and an improvement in operating rate and an improvement in yield can be achieved. In the present invention, in the step of forming the upper layer with the second coating liquid, the application end portion of the lower first coating liquid of the flexible support passes through the second coating apparatus. The application of the second coating solution is terminated before. Even when the application is completed, if such a method is adopted, a stepped portion or the like that becomes a disturbance will not pass, and the effect of the present invention can be further exhibited.

  In this invention, it is preferable to apply | coat by pressing the said flexible support body to the coating liquid supply part of a said 2nd coating device. The effect of the present invention can be suitably exhibited when performing such a coating method.

  In the present invention, in the step of forming the upper layer with the second coating liquid, the application end portion of the lower first coating liquid of the flexible support passes through the second coating apparatus. It is preferable to finish the application of the second coating solution before. Even when the application is completed, if such a method is adopted, a stepped portion or the like that becomes a disturbance will not pass, and the effect of the present invention can be further exhibited.

  Further, in the present invention, it is preferable that the application of the second coating liquid is started 0.2 seconds or more after the application start portion of the lower first coating liquid passes through the second coating apparatus. . By adopting such conditions, the effects of the present invention as will be described later can be suitably exhibited.

  Further, in the present invention, it is preferable that the application of the second coating solution is terminated at least 0.5 seconds before the lower coating portion of the first coating solution passes through the second coating apparatus. By adopting such conditions, the effects of the present invention as will be described later can be suitably exhibited.

  In the present invention, the coating liquid supply unit of the second coating apparatus is provided with a slit that faces the support in the width direction of the support and discharges the coating liquid from the opening. The radius of curvature of the upstream edge of the portion is preferably 5 μm or less. By using the coating apparatus having such a configuration, a coating layer having a uniform film thickness distribution and a smooth surface can be formed.

  As described above, according to the present invention, the first coating solution is applied to the surface of the web (flexible support), and the first coating solution is dried to form a lower layer. A second coating solution is applied to the web having the upper layer. And application | coating of a 2nd coating liquid is started after the application | coating start part of a lower layer passes a 2nd coating device. Therefore, when the application of the second coating liquid is started, a stepped portion that becomes a disturbance does not pass through, and the meniscus of the second coating liquid does not break. Thereby, an unstable phenomenon at the time of application can be eliminated, an application layer having a uniform film thickness distribution and a smooth surface can be formed, and an improvement in operating rate and an improvement in yield can be achieved.

  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 coating 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. ing.

  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 0.05 to 1.0 mm from the liquid reservoir 14 toward the web W, and is similar to the liquid reservoir 14 in the web W. This is a relatively narrow channel extending in the width direction, and the opening length of the web W in the width direction is set to be 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 26b of the front edge surface 26a and the front edge 28b of the back edge surface 28a, so that a film having a predetermined thickness of the coating solution F can be formed.

  The radius of curvature of the trailing edge portion 26b corresponding to the upstream edge of the opening of the slit 16 is 5 μm or less. By using the coating apparatus 10 having such a rear edge portion 26b, a coating layer having a uniform film thickness distribution and a smooth surface 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.

  The distance from the boundary of the slit 16 to the liquid reservoir 14 to the opening (the length of the flow path toward the web W) is the opening length in the width direction of the web W of the slit 16 and the liquid composition of the coating liquid. Depending on various conditions such as physical properties, supply flow rate, supply hydraulic pressure, etc., a range of 30-80 mm is preferably employed when the opening length of the slit 16 in the width direction of the web W is about 1000-1200 mm.

  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 fill 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 known production methods 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 by adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine to an aqueous solution of a ferromagnetic metal. 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. It is also possible to use any one of the method of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent.

  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 having 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, a coating method using a coating apparatus with the coating head 10 as a main component will be described. 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 lower layer is formed on the web W by applying a first coating liquid in advance by another coating means (first coating apparatus) and drying the first coating liquid. The lower layer shown in FIG. 2 is formed by the first coating solution, but is not limited to one layer, and may be a lower layer composed of two or more layers. The point is that the lower layer is in a dry state (so-called “wet-on-dry” method) when the upper layer is formed by applying the coating liquid (second coating liquid) with the coating head 10. .

  Further, when the coating film is formed in three or more layers, the effect of the present invention can be obtained if this wet-on-dry coating method is introduced in the formation of any layer.

  The application of the first coating liquid by another coating means (first coating apparatus) and the formation of the lower layer by drying the first coating liquid are continuous production means provided on the upstream side of the coating apparatus. Alternatively, an off-line production method for supplying the coating head 10 to the coating head 10 while feeding and running the web W from an original roll obtained by winding the web W formed on another line in a roll shape in a roll shape. It may be.

  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, a range of 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.

  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.

  In FIG. 2, the coating start portion F1S of the coating layer in which the lower layer (first coating solution F1) of the web W is formed passes through the coating head 10, more precisely the slit 16, and then the coating head 10 Application of the second coating liquid F2 is started.

  If such a coating method is employed, a stepped portion or the like (coating start portion F1S) that becomes a disturbance does not pass at the start of coating of the second coating solution F2, and the meniscus of the second coating solution F2 is broken. There is nothing. Thereby, an unstable phenomenon at the time of application can be eliminated, an application layer having a uniform film thickness distribution and a smooth surface can be formed, and an improvement in operating rate and an improvement in yield can be achieved.

  That is, in the meniscus portion when applying with such an application head 10, 1) the pressure generated by the air accompanying the web W, 2) the pressure generated in the second coating liquid F2, and 3) the second The three of the surface tension of the coating liquid F2 are balanced mechanically, so that stable coating is performed. Then, the mechanical balance is broken, and the meniscus is broken. As a result, the liquid is scraped back to the upstream portion, causing streaky coating thickness unevenness. However, according to the present invention, such a phenomenon can be eliminated.

  In addition, when exchanging the web supply roll wound with the web W with a new web supply roll, the following two methods are employed. 1) Stop the production line, replace the finished web supply roll with a new web supply roll, connect the rear end of the web W and the front end of the new web W, and restart the operation of the production line. 2) The rear end portion of the web W and the front end portion of the new web W are automatically connected without stopping the production line.

  In particular, when the method 2) is employed, the connecting portion of the web W may come into contact with the opening of the slit 16 of the coating head 10 and damage the coating head 10. Therefore, in this case (when the connecting portion of the web W passes through the coating head 10), the coating is temporarily stopped, the web W is separated from the coating head 10, and the connecting portion of the web W causes the coating head 10 to be separated. It is preferable to resume application after passing.

  As mentioned above, although the example of embodiment of the coating method which concerns on 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, The present invention can be widely applied to a configuration in which a coating solution is continuously applied using an extrusion coating head provided with three sets of independent liquid supply systems so that three types of coating solutions can be supplied.

  Representative examples of these are shown in FIGS. As shown in FIGS. 3 and 4, the coating head 10 ′ is provided with two independent liquid supply systems so that two types of coating liquids can be supplied by a so-called “wet-on-wet” method. . Since the numbers assigned to the respective components are the same as those of the coating head 10 of FIGS. 1 and 2, the detailed description thereof is omitted. However, the upstream liquid supply system is distinguished by adding A after the member number, and the downstream liquid supply system is distinguished by adding B after the member number.

  As shown in FIG. 4, a front edge surface 26a, a first back edge surface 28a, and a second back edge 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. Each surface 30a is formed. The front edge surface 26a is formed in a substantially linear cross section, and the first back edge surface 28a and the second back edge surface 30a are formed in circular arcs having curvature radii R1 and R2, respectively.

  Further, a predetermined step is provided between the rear edge portion of the front edge surface 26a and the front edge portion of the first back edge surface 28a so that a film having a predetermined thickness of the coating liquid F1 can be formed. . Similarly, a predetermined step is provided between the rear edge portion of the first back edge surface 28a and the front edge portion of the second back edge surface 30a so that a film having a predetermined thickness of the coating liquid F2 can be formed. It has become.

  Note that a lower layer F0 is formed on the web W in advance, and so-called “wet-on-dry” coating can be performed.

  Next, other modes that can be adopted will be described. The configuration using the coating head 10 is not configured to press the web W against the coating head 10 as in the example of the above embodiment, but the web W is wound around the backup roller, and the surface of the web W and the tip surface of the coating head 10 are used. It is also possible to adopt a configuration in which application is performed with a predetermined clearance between the two.

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

  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.

  Examples of the present invention will be described in comparison with comparative examples. In the following examples, “parts” means “parts by weight”. In each of the following examples (Examples 1 to 4), three types of coating solutions (coating solutions 1 to 3) were used. The composition of each coating solution was common as follows.

(1) Coating liquid 1
Nonmagnetic powder α-Fe ₂ O ₃ 80 parts
Average long axis length 0.1μm
Specific surface area by BET method 48m ² / g
pH 8, Fe ₂ O ₃ content 90% or more
DBP oil absorption 27-38ml / 100g
Surface coating compound Al ₂ O ₃
20 parts of carbon black
Average primary particle size 16μm
DBP oil absorption 80ml / 100g
pH 8
Specific surface area by BET method 250m ² / g
Volatiles 1.5%
10 parts of vinyl chloride copolymer
MR-110 manufactured by Nippon Zeon Co., Ltd.
Polyester polyurethane resin 5 parts
Molecular weight 35,000
Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1
-SO ₃ Na group 1 × 10 −4 eq / g contained
Stearic acid 1 part Methyl ethyl ketone 100 parts Cyclohexanone 50 parts Toluene 50 parts (2) Coating liquid 2
Ferromagnetic metal fine powder Composition: Fe / Co = 80/20 100 parts
Hc 183 kA / m (2300 Oe)
Specific surface area by BET method 54m ² / g
Crystallite size 16.5nm
Surface coating compound Al ₂ O ₃
Particle size (major axis diameter) 0.10 μm
Needle ratio 8
σs 150A · m ² / kg (emu / g)
5 parts of vinyl chloride polymer
MR-110 manufactured by Nippon Zeon Co., Ltd.
Polyester polyurethane resin 3 parts
Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1
-SO ₃ Na group 1 × 10-4 eq / g-containing α-alumina (particle size 0.1 μm) 5 parts Carbon black (particle size 0.1 μm) 0.5 parts Stearic acid 0.5 parts Methyl ethyl ketone 90 parts Cyclohexanone 30 parts Toluene 60 parts (3) Coating liquid 3
100 parts of ferromagnetic metal fine powder
Composition: Co-substituted barium ferrite
Specific surface area by BET method 35m ² / g
Average particle size 0.06μm
Plate ratio 5
9 parts of vinyl chloride polymer
MR-110 manufactured by Nippon Zeon Co., Ltd.
CrO ₂ (particle size 0.3 μm) 7 parts Polyester polyurethane resin 10 parts
Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1
Stearic acid 0.5 parts Methyl ethyl ketone 70 parts Toluene 20 parts Cyclohexanone 60 parts For the above coating liquid (coating liquids 1 to 3), each component is kneaded with a continuous kneader, and then using a sand mill using steel balls. The dispersion process was performed for 6 hours. Three parts of polyisocyanate was added to the obtained dispersion, and a mixed solvent of methyl ethyl ketone and cyclohexanone was added as appropriate, and the viscosity was adjusted to 1 to 50 P (poise) with a Brookfield viscometer. The viscosities after the viscosity adjustment were 10.7 P (poise) for coating solution 1, 32.5 P (poise) for coating solution 2, and 3.4 P (poise) for coating solution 3, respectively.

  First, a web W for performing wet-on-dry coating was prepared. That is, using a coating head having the same specifications as the coating head 10, a coating film by the coating liquid 1 was formed in advance as a lower layer (first layer), and this coating film was dried. The web W after coating / drying was used as a raw roll wound in a roll shape, and the web W was fed from the roll and fed to the coating head 10 while running.

  As the web W, polyethylene terephthalate having a thickness of 6 μm was used. The traveling speed of the web W was 200 m / min. Then, the discharge amount of the coating liquid F1 was controlled so that the wet thickness of the coating liquid 1 layer was 10.0 μm. The opening width (gap) of the slit 16 of the coating head 10 was 0.2 mm. The front edge surface 26a (see FIG. 2) has a straight cross section, and has an inclination of 5 degrees with respect to the incident angle of the web W. The back edge surface 28a has a cross-sectional arc shape with a radius of curvature of 3 mm so that the leading edge portion 28b is parallel to the retraction angle of the web W. A back layer was previously formed on the back surface of the web W by coating.

  The back layer includes conductive carbon black having an average primary particle size of 30 nm or less, an average primary particle size of 30 nm or more, a standard deviation σ of the average primary particle size of 30% or less of the average particle diameter, and an average primary It is preferable that a nonmagnetic inorganic powder having a particle size of 25 to 100% of the thickness of the back layer is contained.

  As this non-magnetic inorganic powder, the average primary particle size and the standard deviation σ of the average primary particle size are in the above range, and metal oxides such as alumina, silica, chromium oxide, α-iron oxide, calcium carbonate, barium sulfate And the like, resin particles such as melamine and benzoguanamine, and carbon black particles can be used. The average primary particle size of these nonmagnetic inorganic powders is preferably 30 to 500 nm, and more preferably 80 to 300 nm.

  Further, the average primary particle size of these nonmagnetic inorganic powders is preferably 20 to 100% of the thickness of the backcoat layer, and more preferably 35 to 85%. Furthermore, the standard deviation σ of the average primary particle size of these nonmagnetic inorganic powders is preferably 30% or less, more preferably 25% or less of the average primary particle size.

  The addition amount of the nonmagnetic inorganic powder can be optimized by the backcoat thickness, particle size, etc. to satisfy claim 1 of the present application, but with respect to 100 parts of conductive carbon black having an average primary particle size of 30 nm or less. A range of about 2 to 20 parts is preferred. The thickness of the back coat is usually set to 0.2 to 1 μm.

  The following can be enumerated as specific trade names of the particulate carbon black. RAVEN2000B (18 mμ), RAVEN1500B (17 mμ) (above, manufactured by Columbia Carbon Co., Ltd.), BP800 (17 mμ) (manufactured by Cabot Corporation), PRINTEX90 (14 mμ), PRINTEX95 (15 mμ), PRINTEX85 (16 mμ), PRINTEX75 (17 mμ) (and above) Degussa), # 3950 (16 mμ) (manufactured by Mitsubishi Chemical Industries).

  Furthermore, the strength can be improved by adding a hard inorganic powder having a Mohs hardness of 5 to 9 to the back coat. Also in this case, it is preferable to use a powder that matches the size of the nonmagnetic inorganic powder.

[Example 1]
The coating liquid 2 was applied using the coating head 10 shown in FIGS. The traveling speed of the web W was 200 m / min. And the discharge amount of the coating liquid 2 was controlled so that the thickness of the layer of the coating liquid 2 might be 1-5 micrometers. The opening width (gap) of the slit 16 of the coating head 10 was 0.15 mm. The front edge surface 26a (see FIG. 2) has a straight cross section, and has an inclination of 5 degrees with respect to the incident angle of the web W. The back edge surface 28a has an arc shape with a radius of curvature of 1.5 mm, and the leading edge portion 28b is parallel to the retraction angle of the web W.

  The time from when the coating start portion of the coating layer 1 (F1S in FIG. 2) passes through the opening of the slit 16 of the coating head 10 to start coating the coating liquid 2 with the coating head 10 (in the table of FIG. 5 described later, “Time until coating liquid 2 starts to be applied after passing coating liquid 1”) was changed from −0.3 to 1.2 seconds, and the coating state at this time was evaluated. In addition, what is negative in this time means that the coating head 10 starts coating the coating liquid 2 before the coating start portion F1S of the coating layer 1 passes through the opening of the slit 16 of the coating head 10. means. The results are shown in the table of FIG.

  The application state was evaluated by visually observing whether or not the coating liquid was scraped off at the meniscus portion upstream of the opening of the slit 16. Repeated application 3 times under the same conditions, x for scraping state 2 times or more, △ for scraping state 1 time, and no scraping state 1 time Classified as ○.

  The thickness of the coating liquid 2 in the wet state is determined by providing a flow meter in the liquid supply pipe from the quantitative liquid feeding means (quantitative pump), measuring the liquid supply amount, and applying the coating area (the width of the web W). , Calculated from the traveling speed of the web W).

  In addition, an optical sensor is provided on the upstream side of the opening of the slit 16 to detect the passage timing of the coating start part F1S until the application start part F1S starts application of the coating liquid 2 after passing through the opening of the slit 16. At the same time, it is obtained by detecting the application start timing of the coating liquid 2 by a control unit of the coating head 10 (not shown).

  According to the results shown in the table of FIG. 5, in each of the comparative examples (Examples 4, 8, and 9), the application start of the application liquid 2 after the application start portion F1S passes through the opening of the slit 16 is started. The time was -0.3 seconds, and the evaluation was Δ or × (not ○). However, among these three cases, Example 9 with the smallest coating thickness (coating thickness of 1.3 μm) is evaluated as Δ, and it can be said that the conditions are easy to apply.

  Example 3 in which the time until the application start of the coating liquid 2 after the application start portion F1S passes through the opening of the slit 16 is 0.1 second is evaluated as “good”, and in Example 7, the evaluation is “good”. The result was better than the comparative example having the same coating thickness. However, among these two cases, Example 3 with a small coating thickness (coating thickness of 3.2 μm) is evaluated as “good”, and Example 7 with a large coating thickness (coating thickness of 5.1 μm and evaluation is Δ) It can be said that the conditions are easier to apply.

  After the application start portion F1S has passed through the opening of the slit 16, the time until the application of the coating liquid 2 starts is 1.2 seconds, 0.5 seconds, 2, 5, and 0.2 seconds. The evaluations were all good, and all of the results were better than the comparative examples having the same coating thickness.

[Example 2]
The coating liquid 3 was applied using the coating head 10 shown in FIGS. The traveling speed of the web W was 200 m / min. And the discharge amount of the coating liquid 3 was controlled so that the thickness of the layer of the coating liquid 3 might be 1-5 micrometers. The opening width (gap) of the slit 16 of the coating head 10 was 0.15 mm. The front edge surface 26a (see FIG. 2) has a straight cross section, and has an inclination of 5 degrees with respect to the incident angle of the web W. The back edge surface 28a has an arc shape with a radius of curvature of 1.5 mm, and the leading edge portion 28b is parallel to the retraction angle of the web W.

  The time from when the coating start portion of the coating layer 1 (F1S in FIG. 2) passes through the opening of the slit 16 of the coating head 10 to start coating the coating liquid 3 with the coating head 10 (in the table of FIG. 6 described later, “Time until coating liquid 3 starts to be applied after passing coating liquid 1”) was changed from −0.3 to 1.2 seconds, and the coating state at this time was evaluated. Note that, as in the first embodiment, when the time is negative, the coating liquid 3 is applied by the coating head 10 before the coating start portion F1S of the coating layer 1 passes through the opening of the slit 16 of the coating head 10. Means to start application of The results are shown in the table of FIG.

  Evaluation of the application state and measurement of the application thickness were performed in the same manner as in Example 1.

  According to the results shown in the table of FIG. 6, in all of the comparative examples (Examples 15, 19, and 20), the application start of the application liquid 3 after the application start portion F1S passes through the opening of the slit 16 is started. The time was -0.3 seconds, and the evaluation was x regardless of the thickness of the coating (the coating thickness was 1.3 to 5.1 μm).

  Examples 14 and 18 in which the time until the start of application of the coating liquid 3 after the application start portion F1S has passed through the opening of the slit 16 is 0.1 seconds are evaluated as Δ, and both are comparative examples having the same application thickness. Better results.

  After the application start portion F1S has passed through the opening of the slit 16, the time until the application of the coating liquid 3 is started is 1.2 seconds, the 0.5 seconds example 12, 16 and the 0.2 seconds example 13 No. 17 and No. 17 were both evaluated as good, and both were better results than the comparative example having the same coating thickness.

[Example 3]
The coating liquid 2 and the coating liquid 3 were applied using the coating head 10 ′ shown in FIGS. The traveling speed of the web W was 200 m / min. Then, the discharge amount of the coating liquid 2 is controlled so that the wet thickness of the layer of the coating liquid 2 is about 7 μm, and the wet thickness of the layer of the coating liquid 3 is about 2 μm. The discharge amount of the coating liquid 3 was controlled. The opening widths (gap) of the slits 16A and 16B of the coating head 10 ′ were both 0.15 mm. The lower layer F0 (see FIG. 4) of the web W is formed by the coating liquid 1.

  The front edge surface 26a (see FIG. 4) has a straight cross section, and has an inclination of 5 degrees with respect to the incident angle of the web W. The first back edge surface 28a has a cross section with an arc shape with a radius of curvature of 2 mm, the second back edge surface 30a has a cross section with an arc shape with a radius of curvature of 3 mm, and the leading edge portion has an exit angle of the web W. I tried to be parallel.

  The time from when the coating start portion of the coating layer 1 passes through the opening of the slit 16A of the coating head 10 ′ to when the coating head 2 ′ starts coating the coating solution 2 (in the table of FIG. The time until the coating liquids 2 and 3 start to be applied after the passage ”was changed from −0.3 to 1.2 seconds, and the coating state at this time was evaluated. As in the first and second embodiments, this time is negative when the coating start portion F1S of the coating layer 1 passes through the opening of the slit 16A of the coating head 10 ′ before the coating head 10 ′. This means that the application of the coating liquid 2 is started. The results are shown in the table of FIG.

  Evaluation of the coating state and measurement of the coating thickness were performed in the same manner as in Examples 1 and 2.

  According to the results shown in the table of FIG. 7, in the comparative example (Example 25), the time until the application start of the application liquid 2 after the application start portion F1S passes through the opening of the slit 16A is −0.3 seconds. The evaluation was x.

  In Example 24, in which the time from the start of application F1S passing through the opening of the slit 16A to the start of application of the coating liquid 2 was 0.1 seconds, the evaluation was x. Example 21 where the time until the application start portion F1S passes the opening of the slit 16A and starts application of the coating liquid 2 is 1.2 seconds, Example 22 is 0.5 seconds, and Example 23 is 0.2 seconds. In all cases, the evaluation was good, and all of the results were better than the comparative example having the same coating thickness.

  Further, according to the result of visual observation of the coating state, it took 0.2 seconds for the coating liquid 2 to spread stably, and the coating liquid 2 was coated after the coating start portion F1S passed through the opening of the slit 16A. In the case where the time until the start of the coating is 0.1 seconds, it was confirmed that the coating start portion F1S reached the slit 16A before the coating liquid 2 spreads stably. This observation result is consistent with the experimental result shown in the table of FIG.

The following can be derived from the results of Examples 1 to 3 described above.
1) When the lower layer coating start portion F1S passes the coating means after the upper layer coating starts, the upper layer of the meniscus of the coating liquid is broken, and the liquid is scraped back to the upstream portion, causing streaky coating thickness unevenness. Often caused.
2) The above phenomenon becomes more remarkable as the viscosity of the upper coating solution is lower and the thickness of the upper coating layer is larger.
3) In the case of two-layer simultaneous coating by the extrusion coating method, the same results as in the above 1) and 2) are obtained.

[Example 4]
In the above-described Examples 1 to 3, in the step of applying the second coating liquid to the surface of the lower layer obtained by applying and drying the first coating liquid on the surface of the web W, the lower-layer coating start portion is the second. This was an experiment for confirming the effect of the coating method of starting the coating of the second coating liquid after passing through the coating device. On the other hand, the present Example 4 is an experiment for confirming the effect of the coating method for ending the application of the second coating liquid before the lower-layer coating end portion passes through the second coating device.

  The coating liquid 1 and the coating liquid 2 were applied using two sets (10A and 10B) of the coating heads 10 shown in FIGS. The distances between the coating heads 10A and 10B were sufficiently separated, and a drying means was provided in the middle so that the drying of the coating liquid 1 was completed before the coating liquid 2 was coated. In addition, the web W which did not apply | coat the lower layer was used.

  The traveling speed of the web W was 200 m / min. Then, the discharge amount of the coating liquid 1 is controlled so that the wet thickness of the coating liquid 1 layer is about 10 μm, and the wet thickness of the coating liquid 2 layer is about 3.2 μm. In addition, the discharge amount of the coating liquid 2 was controlled. The slit 16 opening width (gap) of the coating head 10A was 0.2 mm, and the slit 16 opening width (gap) of the coating head 10B was 0.15 mm.

  The front edge surface 26a (see FIG. 2) of the coating head 10A has a straight cross section, and has an inclination of 5 degrees with respect to the incident angle of the web W. The back edge surface 28a of the coating head 10A has an arc shape with a radius of curvature of 3 mm, and the tip edge portion is parallel to the retraction angle of the web W. The front edge surface 26a (see FIG. 2) of the coating head 10B has a straight cross section and is inclined by 5 degrees with respect to the incident angle of the web W. The back edge surface 28a of the coating head 10B has an arc shape with a radius of curvature of 1.5 mm so that the tip edge portion is parallel to the retraction angle of the web W.

  In this way, an experiment was conducted in which the condition for terminating the application of the coating liquid was changed before the lower-layer application end portion passed through the application apparatus. FIG. 8 is a conceptual diagram showing the configuration of the fourth embodiment, and FIG. 9 is a timing chart showing the operation of the fourth embodiment.

  In FIG. 8, when the web W is wound and the web W of the web supply roller 36 that feeds out the web W becomes small, the web W is automatically replaced with a new web supply roller 38. At this time, the end portion of the web W is automatically joined to the front end portion of the web W of the new web supply roller 38. The web W that is continuously supplied is processed in the order of the coating head 10 </ b> A, the first drying unit 40, the coating head 10 </ b> B, and the second drying unit 42, and is stored in the web winding roller 44. The timing chart of FIG. 9 shows the application timing before and after the web W is joined.

  Application | coating is not performed when the junction part of the web W passes coating head 10A, 10B. In the coating head 10B, the coating by the coating head 10B is finished before passing through the joint portion of the web W, and 5 seconds later, after passing through the joint portion of the web W, by the coating head 10A. Application is started, and further 0.5 seconds later, application by the application head 10B is started.

  The time until the application of the coating liquid with the coating head 10 ends after the lower layer coating end portion passes through the openings of the slits 16 of the coating heads 10A and 10B (in the table of FIG. The time until completion of the upper layer application "is changed from -3 to 0.5 seconds, and the application state at this time was evaluated. In addition, as in Examples 1 to 3, the time when the time is negative is that the coating heads 10A and 10B before the coating end portion of the lower layer passes through the openings of the slits 16 of the coating heads 10A and 10B. This means that the application of the coating liquid is terminated. The results are shown in the table of FIG.

  Evaluation of the application state was performed by measuring the number of streaks generated after application by visual observation after the timing indicated by the thick arrows shown in the timing chart of FIG.

  According to the results shown in the table of FIG. 10, in the comparative examples (Examples 31 and 32), the coating liquid at the coating head 10 is applied after the lower coating end portion passes through the openings of the slits 16 of the coating heads 10A and 10B. The application is finished. The number of streaks is 7 and 9, respectively, and is in a defective state. The generation of the streaks is considered to occur due to the influence of the step and the dirt at the lower end of the coating applied to the vicinity of the opening of the slit 16.

  In Example 33, application of the coating liquid with the coating head 10 was completed at the moment when the lower layer coating end portion passed through the openings of the slits 16 of the coating heads 10A and 10B. Application of the coating liquid with the coating head 10 was completed 0.2 seconds before the portion passed through the openings of the slits 16 of the coating heads 10A and 10B, and the number of streaks was three. Although it is better than the comparative example, it is in a defective state.

  In Example 35, coating of the coating liquid with the coating head 10 was terminated 0.5 seconds before the lower layer coating end portion passed through the openings of the slits 16 of the coating heads 10A and 10B. This is one, which is an improvement over Examples 33 and 34.

  In Examples 36 and 37, the application of the coating liquid with the coating head 10 was completed one second and three seconds before the lower coating end portion passed through the openings of the slits 16 of the coating heads 10A and 10B, respectively. Yes, no streak is found and the condition is good.

  From the above results, it can be said that it is preferable to finish the application of the coating liquid with the coating head 10 at least 0.5 seconds before the lower layer coating end portion passes through the openings of the slits 16 of the coating heads 10A and 10B.

  In Examples 1 to 4, the influence of the coating start portion and the coating end portion of the back layer was also observed, but no correlation with the performance of the coating film was observed.

  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 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 Table showing results of Example 1 Table showing results of Example 2 Table showing results of Example 3 Conceptual diagram showing the configuration of the fourth embodiment. Timing chart showing operation of embodiment 4 Table showing results of Example 4

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, 26a ... Front edge surface, 26b ... rear end edge part, 28 ... back edge, 28a ... back edge surface, 28b ... tip edge part, F1 ... first coating liquid, F2 ... second coating liquid, W ... flexible support (web)

Claims (5)

Applying a first coating liquid to the surface of the belt-like flexible support that runs continuously with a first coating apparatus, and drying the first coating liquid to form a lower layer;
Applying a second coating liquid to the surface of the lower layer with a second coating device to form an upper layer, and a coating method comprising:
The application of the second coating liquid is started after the application start portion of the lower first coating liquid of the flexible support has passed through the second coating apparatus , and the second coating is applied. In the step of forming the upper layer with the liquid, the application of the second coating liquid is performed before the application end portion of the first coating liquid of the lower layer of the flexible support passes through the second coating apparatus. A coating method characterized by terminating .   The coating method according to claim 1, wherein the flexible support is pressed against a coating liquid supply unit of the second coating apparatus to perform coating. 3. The coating according to claim 1 , wherein the coating of the second coating liquid is started 0.2 seconds or more after the coating start portion of the lower first coating liquid passes through the second coating apparatus. Method. First of any one of claims 1 to 3 coating end portion of the coating liquid to terminate the application of the second coating solution before 0.5 seconds or more which passes through the second coating apparatus of the lower layer The coating method described in 1. The coating liquid supply section of the second coating apparatus is provided with a slit that faces the support in the width direction of the support and discharges the coating liquid from the opening, and is provided at the upstream edge of the slit opening. The coating method according to claim 1 , wherein the radius of curvature is 5 μm or less.

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