JPH05220437A - Coating device - Google Patents

Abstract

PURPOSE:To stably produce a thin layer coated product having uniform coating thickness and not generating trouble such as irregular streaks at a high speed while suppressing the fluctuations of coating thickness in the lateral direction of a support and the generation of irregular steaks. CONSTITUTION:An extrusion type coating head has a front edge positioned on the upstream side in the moving direction of a support and the back edge having a sharp tip end part positioned on the downstream side in the moving direction of the support so that the tip thereof retreats in the direction opposite to the support so as to provide difference in level from the front edge. The wave center line undulation WCA of the slit inner surface 4, front edge surface 5 and back edge surface 6 of the leading end part of the coating head forming a coating layer in a state sealed with the low viscosity liquid 11 preliminarily applied to the coating surface of the support is set to 0.2mum or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus, and more particularly to a coating solution continuously extruded toward a moving support surface.
The present invention relates to an extrusion type coating apparatus for coating a high-speed thin layer having a uniform thickness on the surface of a support.

[0002]

2. Description of the Related Art Conventionally, there are various types of coating devices. For example, a coating liquid continuously extruded toward a moving support surface has a uniform thickness on a support surface at high speed. A variety of extrusion type coating devices for layer coating have been studied, and as a method for sealing the upstream edge of the coating head with a precoat layer to block air entrainment in the coating layer, a method of precoating a liquid of the same composition (Patent Document 1) 58-
No. 2055561), a method of applying a solvent as a precoat onto a support (see JP-A-61-139929), and the like. By these coating methods, thin layer coating at high speed can be realized. However, this coating apparatus is an extrusion type coating apparatus, in which a pressure is applied between the downstream edge and the support, and the coating layer is smoothed. Also becomes non-uniform in the width direction. Further, when foreign matter is mixed on the support or in the precoat coating solution or the coating layer coating solution, the foreign matter is likely to be trapped on the downstream side edge, whereby streaks are likely to occur.

The coating solution referred to here is, for example, a photographic photosensitive coating solution, a magnetic coating solution, a surface protection / antistatic or lubricity coating solution, and its typical products are various photographic films. There are photographic papers, magnetic recording media, etc.

The applicant of the present invention has previously improved these characteristics to avoid streak failures and fluctuations in the coating film thickness due to nonuniformity of the support thickness, Young's modulus, etc., and further, when the coating solution passes through the slots. As a coating apparatus capable of reducing pressure loss, the coating apparatus described in Japanese Patent Application Laid-Open No. 63-20069 was filed. In Japanese Patent Laid-Open No. 63-20069, as shown in FIG. 4, a liquid is sealed by an organic solvent 6 previously applied to the coating surface of the support 1 and is positioned upstream in the moving direction of the support. Front edge 2 and a back edge 3 located on the downstream side with respect to the moving direction of the support and having a tip stepped back from the front edge in the direction opposite to the support and having a sharp tip. A coating device for forming a coating layer on a support by using the extrusion type head has been disclosed.

An organic solvent is first applied to the coated surface of the support by a gravure coater, a roll coater, a blade coater,
It is applied by a commonly used well-known coating device such as an extrusion coater, and this layer prevents entrainment of entrained air from the upstream side of the front edge into the coating layer and maintains a defect-free coating state. High speed coating is possible.

The front edge 2 is located on the upstream side of the support 1 from the exit of the slit 8 and is formed so that the entire edge surface facing the support 1 bulges toward the support. A curved surface having a curvature is generally used as a form of bulging toward the support side, but is not limited to this as long as entrainment of entrained air can be prevented. The back edge 3 is arranged such that its tip is located in the direction opposite to the support body with respect to the tangent line at the exit of the slit 8 of the front edge 2. As a result, the pressing force of the support 1 on the back edge portion 3 does not work, it is possible to prevent trapping of foreign matter and scraping of the support at the same portion, and the thickness of the coating film is affected by unevenness of the support such as a stick. It became difficult and a very good coated product was obtained.

[0007]

However, in the extrusion type coating head as shown in FIG.
The surface roughness of the slit inner surface 4, the front edge surface 5, and the back edge surface 6 and the edge corner portions 9 and 10
It has become clear that streaks frequently occur depending on the state of.

This is because the slit inner surface 4, the front edge surface 5 and the back edge surface 6 of the coating head are the same.
Is highly accurately polished by a grinder into a required shape.Depending on the polishing conditions such as feed rate, cutting depth, selection of grindstone during this processing, and the material of the tip of the coating head,
The state such as the surface roughness and the straightness of the edge corner portions 9 and 10 becomes an unfavorable state, and this state tends to directly appear on the coated surface.

That is, hitherto, for example, JP-A-60-2
In the case of a doctor edge known in Japanese Patent No. 38179, etc., the coating liquid is smoothed at the doctor edge (back edge), so that the inner surface 4 of the slit and the front edge surface 5 also have surface roughness and chipping of the back edge surface 6. Even if the state of is slightly bad, the smoothing action may cause the internal stress generated by the pressure applied to the coating liquid to enhance the flow action of the coating liquid immediately after the coating liquid. It can be presumed that the finished state of the surface roughness of each edge surface could be canceled out as a result by the liquid behavior of the above, but the so-called coating type of the type shown in FIG. It is considered that the coating head is more likely to have coating streaks and uneven thickness, as compared with the pressure type, leading to deterioration of the quality of the coating surface.

As described above, in the coating apparatus according to the present invention, since the smoothing by the doctor edge is not performed, if the surface roughness of the inner surface of the slit and the front edge surface and the state of chipping are bad, streaks or the like will be directly caused. Not only that, but in particular, the thickness unevenness occurred due to the accuracy of the straightness of each surface. Therefore, it goes without saying that the inner surface of the slit and the front edge surface have no surface roughness or chipping like the back edge surface, and in particular, the straightness is required in the slit width direction.

However, since it is impossible to enhance the polishing and surface finish of the coating head endlessly,
In the past, it has been the present situation that how much the finishing state of the coating head should be configured depends on experience, that is, skill, in consideration of cost.

The object of the present invention is to solve the above-mentioned problems of the prior art and to suppress variations in the coating film thickness in the width direction due to non-uniformity in the width direction of the support in a non-pressurizing type coating head, resulting in uniform coating thickness and uneven defects. In the case of a thin-layer coating product having no magnetic field, particularly in the case of a magnetic recording medium, it is an object of the present invention to provide a coating device for stably producing a magnetic recording medium having a good electromagnetic conversion characteristic at a high speed.

[0013]

The object of the present invention is to provide a front edge located upstream with respect to the moving direction of a support and a front edge located downstream with respect to the moving direction of the support. In a coating apparatus for coating at least one kind of coating liquid by an extrusion type coating head having a back edge having a step higher than the edge and receding in the direction opposite to the support and having a sharp front edge, The coating surface of the coating head is sealed with a low-viscosity liquid that has been coated in advance, and the inner surface of the slit of the coating head that forms the coating layer is supported by the inner surface of the slit, the front edge surface, and the back edge surface. This is achieved by a coating device characterized in that the filtered centerline waviness (WCA) in the body width direction is set to 0.2 μm or less.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is an enlarged perspective view of an essential part of the coating head of this embodiment, FIG. 2 is an enlarged plan view of the essential part of the coating head, and FIG. 3 shows a cross-sectional shape of the essential part of the coating head and a coating state of the coating liquid. It is a schematic sectional drawing which shows.

In this embodiment, the front edge 2
Is located on the upstream side (upstream side with respect to the moving direction A of the support body) of the support body 1 from the exit of the slit 8 and projects closer to the support body 1 than the tip portion of the back edge 3 arranged on the downstream side. ing. The corner portion 10 at the tip of the back edge 3 has an acute shape as shown in the drawing, and is located below the tangent line (approximately the passage line of the support 1) drawn from the front corner portion 9 of the slit 8 of the front edge 2. It is located away from.

As shown in FIG. 3, the coating by this coating device is performed by a liquid seal between the coating surface and the front edge 2 by a low-viscosity precoat liquid 11 previously coated on the coating surface of the support 1. In this state, the coating liquid 7 is applied. That is, in both of the embodiments, the application is performed while the precoat liquid 11 is appropriately scraped off and liquid-sealed on the upstream side of the front edge 2. Further, in the figure, the front edge 2 is formed such that the entire edge surface facing the support 1 bulges toward the support. A curved surface having a curvature is generally used as a form of bulging toward the support side, but if entrainment of entrained air can be prevented,
It is not limited to this.

As described above, since the back edge 3 has a sharp edge shape that is closest to the support at the exit of the slit 8, the coating liquid 7 discharged from the slit 8 has a sharp edge tip. The parts are separated from each other, and downstream of this part, they are applied in a non-smoothed, so-called unpressurized state. Strictly speaking, the slit inner surface 4, the front edge surface 5, and the back edge surface 6 have undulations in the width direction of the support, as shown in FIGS. 1 and 2, for example. Since the undulations on each surface do not utilize the smoothing action of the coating head, they affect the shape when the slit 8 and the coating liquid are separated from each other. Have a great impact. Particularly, the corner portion 9 is a portion where the front edge surface 5 and the slit inner surface 4 are combined,
Further, also in the above-mentioned 10, since the slit inner surface 4 and the back edge surface 6 are combined, the undulations on both surfaces overlap each other, and the state of the coated surface is greatly affected.

In consideration of the above, as the polishing surface accuracy of the slit inner surface 4, the front edge surface 5 and the back edge surface 6, the surface waviness in the width direction of the support 1 is studied. It was found that, when the center line waviness (WCA) of the filtrate was 0.2 μm or less, the thickness unevenness of the coating film hardly occurred compared to the case where the concentration was more than this value.

The center line waviness (W
CA) means that traces are made by contacting each surface with a stylus along the width direction of the support 1, and a cross-section curve picked up by the stylus picks up a component with a short surface roughness and a long wavelength. The straightness component was removed and measured. The measured reference length L is 25 mm, and the high cutoff value (fh) is 0.8 mm. Sufficient results can be obtained when the filtrate centerline waviness is 0.2 μm or less, but as a more preferable range, the filtrate centerline waviness is 0.1 μm or less.

Further, the center line average roughness (Ra) of the surfaces of the slit inner surface 4, the front edge surface 5 and the back edge surface 6 may be 1.0 μm or less. It is relatively large compared to the above. In the present embodiment, the case where the coating liquid is a single layer has been described, but the present invention can naturally be applied to multi-layer coating such as two-layer or three-layer coating.

The low-viscosity liquid containing an organic solvent as a main component in the present invention means a liquid in which an organic solvent such as toluene, methyl ethyl ketone, butyl acetate or cyclohexanone is used alone or in combination, or a liquid in which a binder is dissolved in these liquids. The viscosity is 20 cp or less, more preferably 5 cp or less. As the binder, the binder used in the coating liquid described later is used.

In the present invention, the low-viscosity liquid is applied to the coated surface of the support in advance by a commonly used known coating apparatus such as a gravure coater, a roll coater, a blade coater and an extrusion coater. With this pre-applied low viscosity liquid,
Entrainment of entrained air on the upstream side of the front edge when the application liquid is applied is prevented, and a suitable application state is maintained.

In the present invention, at least one or more coating layers are, in a magnetic recording medium, a combination of a magnetic layer only, a magnetic layer having a multilayer structure, and a magnetic layer and a non-magnetic layer. In which the magnetic layer has at least one magnetic layer. Similarly, other than the magnetic recording medium, a known layer structure is possible. The shape of the coating head and the positional relationship with the support are shown in FIG.

The front edge 2 is located on the upstream side of the support from the exit of the slit 8 and projects closer to the support than the tip of the back edge 3 disposed on the downstream side. Further, the front edge 2 is formed such that the entire front edge surface 5 facing the support 1 bulges toward the support. A curved surface having a curvature is generally used as a form of bulging toward the support side, but is not limited to this as long as entrainment of entrained air can be prevented.

The back edge 3 is arranged so that its tip portion is located in the direction opposite to the support body with respect to the tangent line at the exit portion of the slit 8 of the front edge 2. Further, the back edge 3 has a sharp edge shape that is closest to the support at the exit of the slit 8, and the coating liquid discharged from the slit 8 is separated at the tip of the sharp edge and is not smoothed downstream thereof.

Although the coating head is installed between the two guide rollers, a precoat liquid coating head may be installed between the guide roller and the guide roller on the upstream side of the coating head.
The wrap angle in the coating head is about 2 ° to 60 °. The span for forming a wrap in this coating head is generally 50 to 3000 mm, but is not limited to this.

For the liquid feeding system, known techniques depending on the properties of the coating liquid are used. In particular, in the case of a magnetic coating liquid, it generally has a cohesive property, and therefore, it is preferable to give shearing to the extent that it does not coagulate. Specifically, Japanese Patent Application Sho 63
-63601, JP-A-62-95174, etc. When there is no rotor as shown in Japanese Patent Application No. 63-63601, the diameter of the pipe from the pump to the coating head is φ5.
0 mm or less, the pocket size of the magnetic liquid coating head is φ2 to 2
0mm, slit width of magnetic liquid coating head is 0.05mm
It is suitable that the slit length is ˜1 mm and the slit length is 5 mm to 150 mm, but the slit length is not limited to this.

Further, ferromagnetic fine powder is used in the magnetic layer of the magnetic recording medium of the present invention. As ferromagnetic fine powder, γ
-Fo ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , Fe
₃ O ₄ , Co-containing Fe ₃ O ₄ , γ-FeOx, Co-containing γ-FeOx (X = 1.33 to 1.50), CrO
₂ , Co-Ni-P alloy, Co-Ni-Fe-B alloy,
Fe-Ni-Zn alloy, Ni-Co alloy, Co-Ni-
Known ferromagnetic fine powders such as Fe alloys can be used. The particle size of these ferromagnetic fine powders is about 0.005 to 1 micron, and the ratio of axial length / axial width is 1/1 to 50 /. It is about 1. The specific surface area of these ferromagnetic fine powders is 1 m.
² / ^g~70m is about ² / g.

Further, plate-like hexagonal barium ferrite can be used as the ferromagnetic fine powder. The particle size of barium ferrite is about 0.001 to 1 micron in diameter and the thickness is 1/2 to 1/20 of the diameter. The specific gravity of barium ferrite is ^{4 to} 6 g / cc, and the specific surface is 1 m ² / g to 70.
m ² / g.

In the present invention, a binder is used in the magnetic layer together with the ferromagnetic fine powder. Examples of the binder used include conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. The thermoplastic resin has a softening temperature of 150 ° C. or lower and an average molecular weight of 10,0.
Those having a degree of polymerization of about 00 to 300,000 and about 50 to 2,000, for example, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer Combined, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon-
Silicone resin, nitrocellulose-polyamide resin,
Polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene diacrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene A butadiene resin, a polyester resin, a chlorovinyl ether acrylate copolymer, an amino resin, various synthetic rubber type thermoplastic resins, and mixtures thereof are used.

As the thermosetting resin or the reactive resin,
The coating liquid has a molecular weight of 200,000 or less, and when the magnetic layer-forming composition is applied, dried and then heated, these resins undergo reactions such as condensation and addition to give an infinite molecular weight. It can be great. Further, among these resins, it is desirable that the resin does not soften or melt until the resin is thermally decomposed. Specifically, for example, phenol resin, epoxy resin, curable polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, reactive acrylic resin, epoxy polyamide resin, nitrocellulose melamine resin, high molecular weight polyester resin and isocyanate. Prepolymer mixture, methacrylate copolymer and diisocyanate prepolymer mixture, polyester polyol and polyisocyanate mixture, urea formaldehyde resin, low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate mixture, polyamide resin and There is a mixture of these.

The ferromagnetic fine powder dispersed in the binder, the solvent, the dispersant as an additive, the lubricant, the abrasive, the antistatic agent, the non-magnetic support and the like are the same as those conventionally used. To be done. Examples of the dispersant include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and stearolic acid having 12 to 18 carbon atoms (R ₁ COOH, R ₁ is an alkyl or alkenyl group having 11 to 17 carbon atoms): Alkali metal (Li, Na, K, etc.) or alkaline earth metal (M) of the above fatty acid
g, Ca, Ba) metal soap: Fluorine-containing compound of the above fatty acid ester: Amide of the above fatty acid:
Polyalkylene oxide alkyl phosphate ester: Resinine: Trialkylpolyolefinoxy quaternary ammonium salt (alkyl has 1 to 5 carbon atoms, olefin has ethylene, propylene, etc.): etc. are used. In addition to these, higher alcohols having 12 or more carbon atoms, and other than these, sulfuric acid ester and the like can be used.

As the lubricant, the above-mentioned dispersant is also effective, but dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxy polysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkyl. Monoalkoxy polysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms), phenyl polysiloxane, fluoroalkyl polysiloxane (alkyl has 1 to 5 carbon atoms)
Conductive fine powder such as silicon oil, graphite, etc .: Inorganic fine powder such as molybdenum disulfide, tungsten dioxide: Plastic fine powder such as polyethylene, polypropylene, polyethylene vinyl chloride copolymer, polytetrafluoroethylene: α- Olefin polymer: unsaturated aliphatic hydrocarbon that is liquid at room temperature (α-olefin in which a double bond is bonded to the terminal carbon, about 20 carbon atoms): monobasic fatty acid having 12 to 20 carbon atoms and 3 carbon atoms Fatty acid esters, fluorocarbons and the like composed of 12 monohydric alcohols can be used.

As the abrasive, fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet,
Emery (main component: corundum and magnetite) is used. Electrostatic fine powder such as carbon black and carbon black graft polymer as an antistatic agent: Natural surfactant such as saponin: Nonionic surfactant such as alkylene oxide type, glycerin type and glycidol type:
Cationic surfactants such as higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, phosphonium or sulfoniums: acidic such as carboxylic acid group, sulfonic acid group, phosphoric acid group, sulfuric acid ester group, phosphoric acid ester group Group-containing anionic surfactants: amphoteric surfactants such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, etc. are used.

The organic solvent used as the coating solvent includes ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone: esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and glycol monoethyl ether acetate: benzene. ,toluene,
Tar-based (aromatic hydrocarbons) such as xylene: chlorinated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene.

The amount of solvent is 2-3 times that of the magnetic fine powder.
The dispersant is 0.5 to 2 with respect to 100 parts by weight of the binder.
0 parts by weight, the lubricant is 0.2 to 20 parts by weight, and the abrasive is 0.
5 to 20 parts by weight, 0.2 to 20 parts by weight of conductive fine powder used as an antistatic agent, and 0.1 to 10 parts by weight of a surfactant similarly used as an antistatic agent.

The magnetic powder and the above-mentioned binder, dispersant, lubricant, abrasive, antistatic agent, solvent and the like are kneaded to form a magnetic paint. Examples of the material for the support on which these magnetic layers are provided are polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, and polycarbonate. , Plastic films such as polyamide resin and polysulfone, metal materials such as aluminum and copper, and ceramics such as glass. These supports have corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, metal vapor deposition treatment,
Pretreatment such as alkali treatment may be performed. The support may be of any desired shape.

[0038]

As described above, according to the coating apparatus of the present invention, the inner surface of the slit at the tip of the coating head forming the coating layer, the front edge surface and the back edge surface of each surface of the coating head in the support width direction. Noroha centerline swell (WCA) is 0.
Since the coating head is configured to have a thickness of 2 μm or less, the smoothing action of the coating liquid is not used in the coating head, but the shape at the time of separating the slit from the coating liquid can be maintained in a good cross-sectional shape, and the liquid is discharged from the slit. The coating liquid becomes uniform without being affected by the discharge amount distribution due to surface waviness, and especially in the case of high-speed coating of thin layers, it greatly affects the coating surface property, and there are stripes due to fluctuations in the width direction coating film thickness and unevenness. It is possible to stably produce a product having a good surface property with less generation.

[0039]

EXAMPLES Next, the novel effects of the device of the present invention will be further clarified by examples. After putting each component of the coating liquid composition shown below in a ball mill and thoroughly mixing and dispersing, 30 parts by weight of an epoxy resin (epoxy equivalent of 500) was added and uniformly mixed and dispersed to obtain a magnetic coating liquid (magnetic dispersion liquid). did.

The viscosity of the magnetic coating liquid thus obtained was measured with a Rotovisco viscometer, and it showed thixotropic viscosity characteristics at each shear rate. Composition of coating liquid: γ-Fe ₂ O ₃ powder (acicular particles having an average particle size in the major axis direction of 0.5 μ, coercive force of 320 oersted) ... 300 parts by weight Vinyl chloride-vinyl acetate copolymer (copolymerization ratio 87 : 13, polymerization degree 400) ・ ・ ・ 30 parts by weight Conductive carbon ・ ・ ・ 20 parts by weight Polyamide resin (amine value 300) ・ ・ ・ 15 parts by weight Lecithin ・ ・ ・ 6 parts by weight Silicone oil (dimethylpolysiloxane) ・··· 3 parts by weight Xylol ・ ・ ・ 300 parts by weight Methyl isobutyl ketone ・ ・ ・ 300 parts by weight n-butanol ・ ・ ・ 100 parts by weight Further, the pre-coat liquid uses methyl isobutyl ketone and has a thickness of 4.0 μm by a bar coating method. (Wet state).

The coating film thickness was 15 μm (wet state). A polyethylene terephthalate film having a thickness of 15 μm and a width of 500 mm is used as a support, and the tension is 10 kg /
The filter was run at a coating speed of 600 m / min over the entire width, and the filtered center line waviness (WCA) of the slit inner surface 4, front edge surface 5, and back edge surface 6 of the extrusion type coating head shown in FIGS. 05μm, 0.15μ
m and 0.30 .mu.m were changed to three levels, and the conditions of occurrence of thickness unevenness (streaks due to unevenness) were compared and examined in combination. The results are shown in Table 1.

The center line average roughness (Ra) of the inner surface of the slit 4, the front edge surface 5 and the back edge surface 6 was set to 1.0 μm.

[0043]

[Table 1]

As shown in Table 1, the filtered center line swell WCA
(Μm) is 0.3 μm in any of the slit inner surface 4, the front edge surface 5 and the back edge surface 6, that is, in the case of the coating head Nos. Unevenness occurs, and the product quality greatly varies in the width direction, which is not preferable. In addition, before the product is completed, it may cause a large trouble in the post-application process such as winding failure or cutting due to wrinkles, which may damage the equipment.

On the other hand, in all of the inner surface of the slit 4, the front edge surface 5 and the back edge surface, when the waviness of the filtered center line is 0.15 μm or less, that is, the coating head No.
In the case of ,,, and, good magnetic recording media were obtained without the occurrence of unevenness that would cause problems in product quality and subsequent processes. Especially, the swell of the filtered center line is 0.0
No coating unevenness was observed in the coating head No. in the case of 5 μm, and a very good magnetic recording medium could be stably obtained.

In the coating head No., although there was some unevenness due to the waviness of the back edge surface, it was to a degree practically usable. From the above results, it is understood that the filtered center line waviness can be directly connected to the judgment of the quality of the coated surface at the boundary of 0.2 μm.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a coating device according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of the coating apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a main part showing a cross-section of a main part and a coating state of a coating device according to an embodiment of the present invention.

FIG. 4 is a side sectional view of a conventional coating device.

[Explanation of symbols]

 1 Support 2 Front Edge 3 Back Edge 4 Slit Inner Surface 5 Front Edge Surface 6 Back Edge Surface 7 Coating Liquid 8 Slit 9 Corner of Front Edge of Slit 10 Corner of Back Edge of Slit

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[Procedure amendment]

[Submission date] March 10, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

The applicant of the present invention has previously improved these characteristics to avoid streak failures and fluctuations in the coating film thickness due to nonuniformity of the support thickness, Young's modulus, etc., and further, when the coating solution passes through the slots. As a coating apparatus capable of reducing pressure loss, the coating apparatus described in Japanese Patent Application Laid-Open No. 63-20069 was filed. In JP-A-63-20069, as shown in FIG. 4, the support 1 is positioned on the upstream side with respect to the moving direction of the support in a state of being liquid-sealed by an organic solvent 11 previously applied to the application surface of the support 1. Front edge 2 and a back edge 3 located on the downstream side with respect to the moving direction of the support and having a tip stepped back from the front edge in the direction opposite to the support and having a sharp tip. A coating device for forming a coating layer on a support by using the extrusion type head has been disclosed.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

That is, hitherto, for example, JP-A-60-2
In the case of a doctor edge known in Japanese Patent No. 38179, etc., the coating liquid is smoothed at the doctor edge (back edge), so that the inner surface 4 of the slit and the front edge surface 5 also have surface roughness and chipping of the back edge surface 6. even if a state somewhat poor, since this Smoothing action, the coating liquid by the internal stresses caused by pressure applied to the coating solution or enhanced the flow action immediately applied, discharged from the slit coating It can be presumed that the finished state of the surface roughness of each edge surface could be canceled out as a result of the liquid behavior of the liquid, but the so-called type shown in FIG. It is considered that the coating head of (3) is more likely to have coating streaks and particularly uneven thickness as compared with the pressure type, which causes deterioration of the quality of the coated surface.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The object of the present invention is to solve the above-mentioned problems of the prior art and to suppress variations in the coating film thickness in the width direction due to non-uniformity in the width direction of the support in a non-pressurizing type coating head, resulting in uniform coating thickness and uneven defects. In the case of a thin-layer coating product having no magnetic field, particularly in the case of a magnetic recording medium, it is an object of the present invention to provide a coating device for stably producing a magnetic recording medium having a good electromagnetic conversion characteristic at a high speed.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013]

The object of the present invention is to provide a front edge located upstream with respect to the moving direction of a support and a front edge located downstream with respect to the moving direction of the support. In a coating apparatus for coating at least one kind of coating liquid by an extrusion type coating head having a back edge having a step higher than the edge and receding in the direction opposite to the support and having a sharp front edge, The coating surface of the coating head is sealed with a low-viscosity liquid that has been coated in advance, and the inner surface of the slit of the coating head that forms the coating layer is supported by the inner surface of the slit, the front edge surface, and the back edge surface. This is achieved by a coating device characterized in that the filtered centerline waviness (W _CA ) in the body width direction is set to 0.2 μm or less.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

In consideration of the above, as the polishing surface accuracy of the slit inner surface 4, the front edge surface 5 and the back edge surface 6, the surface waviness in the width direction of the support 1 is studied. It was found that, surprisingly, when the filtered wave center line waviness (W _CA ) is 0.2 μm or less, the thickness unevenness of the coating film hardly occurs as compared with the case where it is more than this value.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

The center line waviness (W
_CA ) means that traces are made by contacting each surface with a stylus along the width direction of the support 1, and a cross-section curve picked up by the stylus picks up a component having a short surface roughness and a long wavelength. The straightness component was removed and measured. The measured reference length L is 25 mm, and the high cutoff value (f _h ) is 0.8 mm. In filtered centerline waviness is 0.2μm or less, it is possible to obtain sufficient results, A more preferred range, filtered centerline waviness was 0.1μm or less.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Further, the center line average roughness of the slit inner surface 4 and the front edge surface 5 and the surface of the back edge surface 6 (Ra) may be composed to 1.0 [mu] m or less, the filtered center line waviness It is relatively large compared to the above. In the present embodiment, the case where the coating liquid is a single layer has been described, but the present invention can naturally be applied to multi-layer coating such as two-layer or three-layer coating.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

Further, ferromagnetic fine powder is used in the magnetic layer of the magnetic recording medium of the present invention. As ferromagnetic fine powder, γ
-F e ₂ O _3, Co-containing γ-Fe ₂ O _3, Fe
₃ O ₄ , Co-containing Fe ₃ O ₄ , γ-FeOx, Co-containing γ-FeOx (X = 1.33 to 1.50), CrO
₂ , Co-Ni-P alloy, Co-Ni-Fe-B alloy,
Fe-Ni-Zn alloy, Ni-Co alloy, Co-Ni-
Known ferromagnetic fine powders such as Fe alloys can be used. The particle size of these ferromagnetic fine powders is about 0.005 to 1 micron, and the ratio of axial length / axial width is 1/1 to 50 /. It is about 1. The specific surface area of these ferromagnetic fine powders is 1 m.
² / ^g~70m is about ² / g.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

[0038]

As described above, according to the coating apparatus of the present invention, the inner surface of the slit at the tip of the coating head forming the coating layer, the front edge surface and the back edge surface of each surface of the coating head in the support width direction. Noroha centerline swell (W _CA ) is 0.
Since the coating head is configured to have a thickness of 2 μm or less, the smoothing action of the coating liquid is not used in the coating head, but the shape at the time of separating the slit from the coating liquid can be maintained in a good cross-sectional shape, and the liquid is discharged from the slit. The coating liquid becomes uniform without being affected by the discharge amount distribution due to surface waviness, and especially in the case of high-speed coating of thin layers, it greatly affects the coating surface property, and there are stripes due to fluctuations in the width direction coating film thickness and unevenness. It is possible to stably produce a product having a good surface property with less generation.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction content]

The coating film thickness was 15 μm (wet state). A polyethylene terephthalate film having a thickness of 15 μm and a width of 500 mm is used as a support, and the tension is 10 kg /
The entire width and coating speed of 600 m / min were run, and the filtered center line waviness (W _CA ) of the slit inner surface 4, front edge surface 5, and back edge surface 6 of the extrusion type coating head shown in FIGS. 1 to 3 was set to 0. 0.05 μm, 0.15 μ
m and 0.30 .mu.m were changed to three levels, and the conditions of occurrence of thickness unevenness (streaks due to unevenness) were compared and examined in combination. The results are shown in Table 1.

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

[0043]

[Table 1]

[Procedure Amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

As shown in Table 1, the filtered center line swell W _CA
(Μm) is 0.3 μm in any of the slit inner surface 4, the front edge surface 5 and the back edge surface 6, that is, in the case of the coating head Nos. Unevenness occurs, and the product quality greatly varies in the width direction, which is not preferable. In addition, before the product is completed, it may cause a large trouble in the post-application process such as winding failure or cutting due to wrinkles, which may damage the equipment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Tomaru 2-12-1, Ogimachi, Odawara City, Kanagawa Fuji Photo Film Co., Ltd.

Claims (2)

[Claims] 1. A front edge located upstream of a support moving direction, and a front edge located downstream of the support moving direction with its tip stepped from the front edge, in a direction opposite to the support direction. In the coating device for coating at least one or more kinds of coating liquid by the extrusion type coating head having the back edge having a sharp angle with the back end sharpened, the coating surface of the support has a low viscosity previously coated. In the state of being liquid-sealed by the above liquid, the filter center line waviness (WCA) in the width direction of the support on each of the inner surface of the slit, the front edge surface, and the back edge surface of the tip of the coating head forming the coating layer. ) Is less than 0.2 μm. 2. The coating apparatus according to claim 1, wherein the center line average roughness (R) of the inner surface of the slit, the front edge surface, and the back edge surface of the tip of the coating head.
A coating apparatus characterized in that a) is configured to be 1.0 μm or less.