DE4304281B4 - coater - Google Patents

Abstract

Coating apparatus for applying a uniformly thick material composition to a moving carrier (1) with an extruder head comprising:
A front edge (2) which is arranged on the front side of the extruder head in the direction of movement of the carrier (1) and has a surface (5) facing the carrier (1),
A trailing edge (3) which is arranged on the rear side of the extruder head in the direction of movement of the carrier (1) and has a surface (6) facing the carrier (1) and
A gap (8) with inner surfaces (4) formed between the leading edge (2) and the trailing edge (3) and through which the material composition is extrudable,
characterized in that
in the surfaces (5, 6) and the inner surfaces (4), waves along the direction of the width of the carrier (1) are formed.

Description

The The invention relates to a coating device according to the preamble of claim 1. It is an extrusion type for coating the surface of a moving vehicle at a high speed with a thin film coating composition (-Beschichtungsmasse) in a uniform thickness.

It have already been conventional coating devices for coating the surface a moving vehicle proposed with a coating composition (coating composition). at a conventional method is an upstream side (inlet side) a coating head sealed with a pre-coating layer, to prevent that together with the coating layer Air on the carrier arrives. This procedure was carried out using a precoat having a composition with the same components throughout (see the unaudited Japanese Patent Publication No. Sho 58-205 561A). This method was also performed by coating the carrier with a solvent as a pre-coating (see the unaudited Japanese Patent Publication No. Sho 61-139,929A). These precoating methods enable the application of a thin film coating at high speed through extrusion.

If however, these precoating methods apply to a coating apparatus of the extrusion type, the precoating layer must be interposed between the Be the trailing edge of the coating head and the carrier are pressed together around the coating layer to smooth. If now the carrier a uneven width also has the thickness of the coating film unevenly along its width. Furthermore, if foreign matter on the support or in the overcoat layer or in the precoat composition the foreign material at the exit edge of the coating head which results in streaks in the coating layers.

Usually various coating compositions (coating compositions) are used, such as. a photographic photosensitive coating composition, a magnetic coating composition, a surface protection / anti-charging agent or smoothing coating composition. These compositions can for different Products, such as photographic film proof papers, magnetic Recording media and the like., Can be used.

A Improvement of the coating device described above Applicant's is, for example, in the Japanese Unexamined Patent Publication No. Sho 63-20,069A, in which variations in the coating film thickness, caused by streak defects, uneven carrier thickness, Fluctuations in Young's Module and the like., Can be prevented. With this coating device were Also reduces the pressure losses that occurred earlier when a coating composition Slit happened.

As described in Japanese Unexamined Patent Publication No. Sho 63-20,069A, and in U.S. Pat 4 In particular, such a coating device serves to produce a coating layer on a support 1 with a coating surface. The coated surface is treated with an organic solvent 11 liquid-sealed previously applied thereon using an extrusion-type coating head having a leading edge 2 located on the upstream side of the carrier (with respect to the direction of movement). The coating head has a trailing edge 3 located on the downstream side of the carrier. The trailing edge 3 has an upper end that slopes down away from the leading edge along the direction of travel of the carrier and that has an acute-angled upper end portion.

At the Operation is first the coating surface of the carrier with an organic solvent coated using a known coating apparatus, such as. a gravure, roll, blade, extrusion coater or the like. These coating devices bring a layer on, which prevents that from happening the leading edge of the coating head air is introduced into the coating layer, making it possible will maintain a flawless coating condition and perform a high-speed coating.

The leading edge 2 is on the upstream side of the carrier 1 away from the exit of the slot 8th arranged. The leading edge 2 is shaped so that the entire surface of the carrier 1 ge opposite edge surface in the direction of the carrier 1 forming a bead. Although the bead surface is generally shaped with a predetermined curved surface, the shape is not limited to this shape. Any shape may be used as long as it can prevent air from passing along with the coating layer.

The trailing edge 3 is arranged so that its upper end portion is disposed away from a Tangentiallinie extending from the exit point of the leading edge 2 and extends parallel to the carrier. As a result, by the carrier 1 no pressure on the trailing edge 3 exerted, thereby preventing foreign material between the trailing edge 3 and the carrier is included. This arrangement also prevents the carrier from being scraped off. Also, the thickness of the coating film is hardly affected by irregularities in the thickness of the support, such as depressions or the like. Therefore, this arrangement provides improved products.

In an extrusion type coating head, as in 4 however, many stripes may be formed depending on the surface roughness of a slot inner surface 4 , a leading edge surface 5 and a trailing edge surface 6 the upper end portion of the coating head and depending on the state of the edge angle sections 9 and 10 , It may therefore still undesirable conditions occur, although the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 in the above-mentioned coating head are ground with high accuracy by means of a grinding device to the desired shape.

These undesirable conditions include rough surfaces, wavy edge angle sections 9 and 10 and the like. These conditions depend on the conditions under which the grinding is carried out, such as the feeding speed, the cutting depth, the selection of the grinding stone and the like. The material used for coating the top end portion of the coating head influences the conditions such as Surface roughness, the straightness of the edge angle sections 9 and 10 and the like. These undesirable states appear directly on the coating surface.

To avoid these undesirable conditions, a conventional coating head was provided with a doctor edge (trailing edge) (see Japanese Unexamined Patent Publication No. Sho 60-238179A), which smoothes the coating composition. This allows, even if the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 Some rough or broken (cracked) surfaces, the above problems are minimized by smoothing the coating. The fluidity of the coating composition immediately after application can be increased by an internal stress generated by increasing the pressure on the coating composition during the above-described smoothing operation. Therefore, the surface roughness of the respective edge surfaces, when subjected to a finish treatment, can be minimized and compensated for by the liquid behavior of the coating composition extruded from the slot. In a coating head of the type in which no high pressure is applied to the coating composition at the time of coating ( 4 However, coating stripes and uneven thickness often occur, thereby causing deterioration of the quality of the coating surface.

Further can, if a coating device is used, the no Squeegee edge to carry a smoothing has, the surface roughness or the broken (cracked) state of a slot interior surface and a pre-edge surface cause defects other than streaks, such as uneven thickness, depending on the degree of straightness of the respective surfaces. Therefore, a surface roughness must be or a broken (cracked) condition in the slot inner surface, the Leading edge surface and the trailing edge surface be prevented. In particular, it is also necessary that the coating in the direction of the slot width is straight.

The Nature of the ground or surface treated condition of the Coating head, however, can only to a limited extent be improved by the methods described above.

In addition, occurs For the reasons given below, the problem of streaking on.

Although the slot interior surface 4 , the leading edge surface 5 and the trailing edge surface 6 In the coating head described above, to obtain the required shape, they can be ground with high accuracy by means of a grinder, undesirable conditions with respect to the surface roughness, the straightness of the edge angle sections 9 and 10 and the like, depending on the conditions in which the grinding process is performed, such as the feeding speed, the cutting depth, the selection of the grinding stone or the like, or some material from the top end portion of the coating head creates conditions such as surface roughness, straightness the edge angle sections 9 and 10 and the like, so that there is a danger that these undesirable conditions will appear directly on the coating surface.

That is, in a conventional coating head having a squeegee edge, as disclosed in, for example, Japanese Unexamined Patent Publication No. Sho 60-238179A of the like, a coating composition is smoothed by the squeegee edge (trailing edge) so that even if the slot inside surface 4 , the leading edge surface 5 and the trailing edge surface 6 as noted above, are somewhat poor in surface roughness or cracked state, the fluidity of the coating composition immediately after application is increased by an internal stress caused by the pressure exerted on the coating composition as a result of acts above smoothing function. It can therefore be considered that the final states of the surface roughness of the respective edge surfaces can be compensated by the liquid behavior of the slit extruded coating composition. However, it can be assumed that in a coating head of the type which does not exert high pressure on a coating composition at the time of coating, as in US Pat 4 as shown, coating streaks or unevenness of the thickness, which cause deterioration of the quality of the coating surface, as compared with the type in which pressure is applied.

Out JP 1-308688 is a coating apparatus having the features the preamble of claim 1 known.

A another coating device having an extruder head, is known from JP 50-138036.

A The object of the present invention is a coating device to provide, with the thickness variations along the width of a coating film reduced or suppressed can be.

According to the invention this Problem solved by the coating device according to claim 1. preferred versions The invention are specified in the subclaims.

in the Below, the invention with further details and below For example, with reference to the schematic drawing.

In this shows:

1 a perspective view of a main portion of a first embodiment of a coating device constructed according to the invention;

2 a plan view of a main portion of the embodiment of the coating device according to the invention, as shown in 1 is shown;

3 a schematic sectional view of the first embodiment of the coating device according to the invention;

4 a side sectional view of a conventional coating apparatus;

5 a schematic sectional view of a second embodiment of the coating device according to the invention;

6 a further schematic sectional view of the second embodiment of the coating device according to the invention; and

7 a schematic sectional view of a third embodiment of the coating device according to the invention.

A preferred embodiment The invention will be described below with reference to the attached Drawings closer described.

The 1 shows an enlarged perspective view of a main portion of a coating head according to a first embodiment of the invention, which 2 shows an enlarged plan view of a main portion of the coating head according to 1 and the 3 shows a schematic sectional view showing the cross-sectional shape of the Hauptabschntites of the coating head according to 1 explained.

In this embodiment, a leading edge 2 on the upstream side of a carrier 1 (With respect to the direction A of the movement of the carrier, which in 3 indicated) away from the exit of a slot 8th arranged. The leading edge 2 extends in the direction of the carrier 1 further than the upper end portion of a trailing edge 3 which is disposed on the downstream side of the coating head. Angled section (angle section) 10 the upper end of the trailing edge 3 has an acute-angled shape, as in 1 explained. This angled section 10 is arranged at a great distance downwards from a tangential line, starting from an angled section 9 the leading edge 2 runs parallel to the carrier surface.

In operation, when using this coater, a coating surface of the support becomes 1 with a coating composition 7 coated, while a distance between the coating surface and the leading edge 2 with a precoating composition 11 is sealed with low viscosity, which is previously applied to the coating surface, as in 3 shown. In particular, in this embodiment, during the sealing, a coating is performed by scraping the precoating composition 11 on the upstream side of the leading edge 2 , In the drawings, the leading edge 2 shaped so that its entire edge surface 5 that the carrier 1 opposite, towards the wearer 1 forming a bead. Although the surface 5 is generally curved in the direction of the carrier, the shape of the surface 5 Not limited to this shape, but any shape can be used as long as it can prevent, together with the composition 11 Air is absorbed.

As described, the trailing edge 3 a sharp edge at the exit point of the slot 8th closest to the wearer. In this way, the coating composition is extruded from the slot 8th is detached (severed) by the sharp edge in the upper end portion and applied in a nonuniform state without being pressed on the carrier.

The slot inside surface 4 , the leading edge surface 5 and the trailing edge surface 6 are shaped so that they have waves along the direction of the beam width ( 1 and 2 ). Since the coating head is not used to smooth the coating, these waves in the respective surfaces determine the shape when the coating composition is removed from the slot 8th exit. These waves greatly affect the properties of the coating surface during high speed coating with a thin layer. The angled section 9 is the point where the leading edge surface 5 on the slot inside surface 4 incident. The angled section 10 is the point where the slot inner surface 4 on the trailing edge surface 6 incident. The waves of the respective cross-sectional pairs of surfaces superimpose each other and be influenced to a large extent the state of the coating surface.

In consideration of the above, the surface accuracy of the ground slot inner surface became 4 , the leading edge surface 5 and the trailing edge surface 6 from the viewpoint of surface waves along the width of the carrier 1 examined exactly.

The filtration centerline wave (WCA) defined in the invention was measured by scanning the respective surfaces with a contact needle along the width of the carrier. When using the WCA, from a curve of a portion of the carrier being scanned by the needle, a component of the surface roughness having a short wavelength and a component of surface uniformity having a long wavelength are extinguished. The measured reference length L was 25 mm and the high band section value (F _b ) was 0.8 mm. Sufficient results were obtained when the filtration centerline wave was no greater than 0.2 μm and even better results were obtained when the WCA was not larger than 0.1 μm.

It is sufficient if the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 not more than 1.0 μm below the average surface centerline roughness (R _a ), which is relatively large compared to the filtration centerline wave. Although the formation of a single layer of a coating composition has been described above, the present invention can also be applied to a multi-layer coating such as two layers, three layers and the like. The low viscosity composition of the present invention containing an organic solvent as a main component may include a liquid of a single solvent or a combination of organic solvents such as toluene, methyl ethyl ketone, butyl acetate, cyclohexanone and the like, or the above-mentioned liquid in which Binder is dissolved, be. The viscosity of the liquid is selected to be not higher than 20 mPa.s (20 cP), preferably not higher than 5 mPa.s (5 cP). The binder used in the coating composition will be described below.

According to the invention coating surface a carrier first with a liquid with a low viscosity coated using a well-known coating apparatus, for example a gravure, roll, blade, extrusion coater or the like. This previously applied low viscosity liquid prevents that air on the upstream enclosed side of the leading edge when a coating composition is applied. The present invention can be practiced using one or more coating layers, for example a single magnetic layer, a magnetic layer with a multilayer structure or a combination of magnetic and non-magnetic layers, which in the case of a magnetic Recording medium has at least one magnetic layer. Naturally can also other known layer structures are used.

The 2 shows the shape of a coating head and the arrangement relationship between the coating head and a support. The leading edge 2 along the Trä gers 1 on the upstream side of the exit of the slot 8th is arranged, is denser up to the carrier 1 before than the upper end portion of the trailing edge 3 , The leading edge 2 is shaped so that the entire surface of the leading edge surface 5 that the carrier 1 opposite to the carrier 1 forms a bead. Although a curved surface having a certain curvature is generally used as a shape for the bead-forming portion toward the substrate, the shape of this surface is not limited to this specific shape. It can be used in any shape as long as it prevents air from under the leading edge 2 flowing. The trailing edge 3 is arranged so that its upper end portion is arranged in the direction away from the carrier beyond a Tangentiallinie downstream from the front edge 2 extends. The trailing edge 3 has a sharp edge, which comes closest to the carrier at the exit portion of the slot 8, so that the out of the slot 8th extruded coating composition is separated at the upper end portion of the sharp edge. However, the extruded coating composition is not smoothed on the downstream side.

During the above described coating head between two guide rollers can be arranged, another coating head between the Coating head and the guide roller on the upstream be provided side of the coating head. This second coating head applies a pre-coating composition. The overlap angle in the coating head is between 2 and 60 °. Although the gap to create an overlap in this coating head is generally 50 to 3000 mm, is he is not limited to this area.

It be different techniques for the liquid feed system applied, depending on the type of coating composition. Especially when using a magnetic coating composition For example, having coagulation properties, it is preferable to use a shearing method apply. Reference is made in particular to the Japanese Patent Application No. Sho 63-63601A and Japanese Unexamined Patent Publication No. Sho 62-95174A. If no rotor used is (Japanese Patent Application No. Sho 63-63 601A) is the diameter the piping arrangement between a pump and a coating head preferably not larger than 50 mm, the pocket diameter of the magnetic composition coating head is 2 to 20 mm, the slit width of the magnetic composition coating head is 0.05 to 1 mm and the slot length is 5 to 150 mm, and the invention is not limited to these values.

To form a magnetic layer of a magnetic recording medium according to the invention a ferromagnetic fine powder is used. As the ferromagnetic fine powder, the following known ferromagnetic fine powders can be used: γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , γ-FeO _x , Co -containing γ-FeO _x (x = 1.33 to 1.50), CrO ₂ , a Co-Ni-P alloy, a Co-Ni-Fe-B alloy, an Fe-Ni-Zn alloy, a Ni-Co alloy and a Co-Ni-Fe alloy and the like. These ferromagnetic fine powders should have a grain size of between 0.005 and 1 μm in length and a ratio of longitudinal axis to transverse axis between 1/1 and 50/1. The specific surface area of such a ferromagnetic fine powder is about 1 to 70 m ² / g. As the ferromagnetic fine powder, a plate-shaped hexagonal barium ferrite can be used. With respect to the grain size of barium ferrite, the diameter is preferably about 0.001 to 1 μm, and the thickness is preferably 1/2 to 1/20 of the diameter. The specific gravity of barium ferrite is 4 to 6 g / cm ³ and the specific surface area is 1 to 70 m ² / g. According to the invention, a binder for a magnetic layer is used together with the ferromagnetic fine powder. The binder to be used may be a thermoplastic resin, a thermosetting resin, a reaction resin or a mixture thereof.

If a thermoplastic resin is used, it should have a softening temperature from no higher as 150 ° C, an average molecular weight in the range of 10,000 to 300,000 and a degree of polymerization in the range of about 50 to 2000 have. In particular, the thermoplastic resin can be selected a vinyl chloride / vinyl acetate copolymer, a vinyl chloride / vinylidene chloride copolymer, a vinyl chloride / acrylonitrile copolymer, an acrylate / acrylonitrile copolymer, an acrylate / vinylidene chloride copolymer, an acrylate / styrene copolymer, a methacrylate / acrylonitrile copolymer, a methacrylate / vinylidene chloride copolymer, a methacrylate / styrene copolymer, a urethane elastomer, a nylon silicone system resin, a nitrocellulose polyamide resin, polyvinyl fluoride, a vinylidene chloride / acrylonitrile copolymer, a butadiene / acrylonitrile copolymer, a polyamide resin, polyvinyl butyral, cellulose derivatives (such as cellulose acetate butyrate, Cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose and the like), a styrene / butadiene copolymer, a polyester resin, a chlorovinyl ether / acrylate copolymer, an amino resin, a thermoplastic resin of various synthetic Rubber systems, mixtures thereof and the like.

If a thermosetting one or reaction resin is used, it should have a molecular weight of not more than 200,000 in the form of a coating composition to have.

If a composition for forming a magnetic layer is applied, is dried and then heated, but this resin takes on the reaction, for example, a condensation, addition and the like., part, so that it then has an unlimited molecular weight. As such a resin preferred is a resin that does not soften or dissolve before it is thermally decomposed. Examples of such a resin include Phenolic resin, an epoxy resin, a curable Polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, a reaction acrylic system resin, an epoxy-polyamide resin, a nitrocellulose-melamine resin, a mixture from a polyester resin having a high molecular weight and a Isocyanate prepolymer, a mixture of a methacrylate copolymer and a diisocyanate prepolymer, a blend of a polyester polyol and polyisocyanate, a urea-formaldehyde resin, a mixture of a low molecular weight glycol, a glycol high molecular weight and triphenylmethane triisocyanate, a polyamide resin, mixtures thereof and the like.

Similarly, the commonly used ferromagnetic fine powders may be dispersed in a binder, a solvent, an additive such as a dispersant, a lubricant, an abrasive, an anti-electrification agent, a non-magnetic support and the like the dispersant includes a selacic acid having 12 to 18 carbon atoms (R ₁ COOH wherein R _{1 represents} an alkyl or alkenyl group having 11 to 17 carbon atoms) such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid , Elaidic acid, linoleic acid, linolenic acid, stearolic acid; a metallic soap consisting of an alkali metal (Li, Na, K and the like) or an alkaline earth metal (Mg, Ca, Ba and the like) of the above-mentioned selacic acid; a fluorine-containing compound of the above-mentioned selacic acid ester; an amide of the above-mentioned selacic acid; Polyalkylenoxidalkylphosphat; lecithin; a trialkyl polyolefin-oxy-quaternary ammoniate (the number of carbon atoms of alkyl is 1 to 5, the olefin is ethylene, propylene and the like) and the like. Besides the above compounds, a higher alcohol having a number of carbon atoms of not less than 12, a sulfate and the like are used.

Although the above-mentioned dispersants also have a lubricating effect, examples of the usable lubricant (lubricant) include silicone oil such as an electroconductive fine powder of Di. alkylpolysiloxane (having 1 to 5 carbon atoms in the alkyl group), dialkoxypolysiloxane (having 1 to 4 carbon atoms in the alkoxy group), monoalkylmonoalkoxypolysiloxane (having 1 to 5 carbon atoms in the alkyl group and having 1 to 4 carbon atoms in the alkoxy group), phenylpolysiloxane, chloroalkylpolysiloxane (having 1 to 5 carbon atoms in the alkyl group) and the like, graphite and the like; non-organic fine powders such as molybdenum disulfide, tungsten dioxide and the like; fine plastic powders such as polyethylene, polypropylene, a polyethylene / vinyl chloride copolymer, polytetrafluoroethylene and the like; an α-olefin copolymer; Selacic acid esters consisting of a monobasic selacic acid having 12 to 20 carbon atoms and a monovalent alcohol having 3 to 12 carbon atoms, fluorohydrocarbons and the like.

Examples of the abrasive include molten alumina, carbonized silicon (silicon), chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components corundum and magnetite), and the like.

To Examples of the anti-electrical agents are included electrically conductive fine powder, e.g. Carbon black, a carbon black graft polymer and the like; a natural surface active Agent, such as saponin; a nonionic surfactant such as those the alkylene oxide systems, glycerol systems, glycidol systems and etc .; a cationic surfactant Agent, like higher Alkylamines, quaternary ammonates, complex rings such as pyridine and others, phosphonium or sulfonium compounds and the like; an anionic surfactant Agent containing a base, e.g. a carboxyl group, a sulfo group, a Phosphoric acid group, a sulfuric acid ester group, a phosphoric acid ester group and the like; and an amphoteric surfactant such as e.g. Amino acids, aminosulfonic acids, Sulfuric acid- or phosphoric acid ester of aminoalcohol and the like

To Examples of the organic solvent, as a coating solvent is used those of the ketone systems, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, Cyclohexanone and the like; the ester systems, such as methyl acetate, ethyl acetate, Butyl acetate, ethyl lactate, glycol acetate monoethyl ether and the like; the tar systems (aromatic hydrocarbons), such as benzene, toluene, xylene and etc .; Hydrocarbon chlorides, such as methylene chloride, ethylene chloride, Carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene and the like; and the like.

The Amount of solvent is 2 to 3 times the amount of the fine magnetic powder. 0.5 to 20 parts by weight of dispersant are used per 100 parts by weight of binder, 0.2 to 20 parts by weight of lubricant (lubricant), 0.5 to 20 parts by weight Abrasive, 0.2 to 20 parts by weight of the electrically conductive fine Powder using as the electrical charge-preventing agent and 0.1 to 10 parts by weight of the surface active agent, also used as an agent against an electrical charge. The magnetic Powder, the binder, the dispersant, the Gleitmit tel (lubricant), the Abrasive, the anti-electrical agent, the solvent and the like are mixed together to form a magnetic paint.

To Examples of the materials for the carrier, on which the magnetic layer is to be applied include polyester, such as polyethylene terephthalate, polyethylene naphthalate and the like; polyolefins such as polypropylene and the like; Cellulose derivatives, such as cellulose triacetate, Cellulose diacetate and the like; Resins of the vinyl system, such as polyvinyl chloride and the like; Plastic films made of polycarbonate, a polyamide resin, polysulfone and the like; Metallic materials such as aluminum, copper and the like; Ceramic materials, like glass and the like; and the like. These carriers may be pre-treated beforehand be subjected, for example, a corona discharge treatment, a Plasma treatment, a primer coating treatment, a heat treatment, a metal deposition treatment, an alkali treatment and the like The carriers can if desired have different forms (shapes).

As described above, the coating apparatus of the present invention is constructed so that the filtration center line (WCA) widths of the support of a slit inner surface, a leading edge surface and a trailing edge surface of a coating head to form a coating layer are not larger than 0.2 μm are. Thus, despite the fact that the coating head does not require the use of a coating composition having a smoothing function, it is possible to maintain an improved cross-sectional shape as the coating composition emerges from the slot. In this way, the coating composition is uniformly made without any influence of uneven distribution of an extruded coating amount caused by surface waves. Also, the properties of the coating surface are greatly affected when the surface is coated with a thin layer at a high speed. It is therefore possible to produce products with improved surfaces without streaking occurring, caused by an uneven coating film thickness in the width direction.

One first example of the coating device according to the invention will be closer below described.

After the below-mentioned components of the coating composition were introduced into a ball mill, mixed therein and sufficiently dispersed, an epoxy resin (epoxy equivalent 500) in an amount of 30 parts by weight was added thereto, mixed and uniformly dispersed to prepare a magnetic coating composition (a magnetic dispersion composition). When the viscosity of the magnetic coating composition thus prepared was measured by using a rotoviscometer, thixotropic viscosities indicated below were obtained at the respective shear rates. Components of the coating composition γ-Fe ₂ O ₃ powder (acicular particles having an average grain size in the direction of the length of 0.5 μm, coercive force 320 Oe) 300 parts by weight Vinyl chloride / vinyl acetate copolymer (copolymerization ratio 87:13, degree of copolymerization 400) 30 parts by weight electrically 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 xylene 300 parts by weight methyl isobutyl ketone 300 parts by weight n-butanol 100 parts by weight

It was also Methyl isobutyl ketone as a pre-coating composition used and using a bar coating system until to a thickness of 4.0 microns (wet state) applied. The thickness of the coating film was 15 μm (wet Status).

As the support, a polyethylene terephthalate film having a thickness of 15 μm and a width of 500 mm was used. The support was run under a tension of 10 kg / total width at a coating speed of 600 m / min, with the center line of filtration (WCA) of the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 of the extrusion type coating head as described in US Pat 1 are set to values of 0.05 .mu.m, 0.15 .mu.m and 0.30 .mu.m. Then, the states (layers) of the formation of uneven thickness (stripes caused by unevenness) were compared with each other in connection with the filtration centerline waves (WCA). The result is given in Table I. The average surface centerline roughness (R _a ) of the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 were set at 1.0 μm.

Table I

⦿

extrem verbessert

Ο

verbessert

Δ

während der praktischen Verwendung traten keine Probleme auf trotz des Vorliegens eines ungleichmäßigen Zustandes und

x

es traten Probleme auf.

In Table I mean

⦿

extremely improved

Ο

improved

Δ

during practical use, no problems occurred in spite of the presence of an uneven condition and

x

there were problems.

As shown in Table I, when the filtration centerline wave WCA (μm) is selected to be in the slot inner surface 4 , in the leading edge surface 5 and in the trailing edge surface 6 0.3 μm (ie, in cases Nos. (1), (4) and (6), uneven stripes were formed in the interstices of the surface waves 0.3 μm, and the quality of the products significantly varied along the width of the layer For example, before the completion of a product, a wrinkling effect could sometimes halt the operation of the device, for example as a result of an erroneous winding or cutting operation.

On the other hand, if the filtration centerline wave (WCA (μm) is not larger than 0.15 μm both in the slot inner surface 4 as well as in the leading edge surface 5 and in the trailing edge surface 6 (ie, in cases Nos. (2), (3), (5), (7) and (8)), uneven stripes were not formed and an improved magnetic recording medium could be obtained. In particular, in case No. (8) in which each filtration corrugation wave was 0.05 μm, uneven stripes did not occur and stably improved magnetic recording media were stably obtained.

in the Case No. (9) became a mean degree of unevenness generated because of the bigger waves in the trailing edge surface, however, this was during the practical use no problem.

From the above results, it can be seen that filtration centerline waves of not larger than 0.2 μm are directly correlated to the quality of the coating surface.

A Coating device for applying a magnetic coating composition for a Magnetic tape or the like in the form of a layer according to a second embodiment The present invention will be described below with reference to FIG the accompanying drawings explained.

The 5 shows a cross-sectional view of the coating apparatus of this embodiment. The location of application by the coating apparatus will be described below. In the coating device 110 as they are in 5 is shown is a leading edge 2 located on the upstream side, relative to the direction of movement of a wearer 1 , is arranged so shaped that its entire leading edge surface 2a that the carrier 1 opposite, swells to the wearer. Although a curved surface having a curvature (R) is generally applied as a form of swelling toward the support, the shape is not limited, but any shape may be used, for example, a flat shape as long as it can prevent Air, the carrier 1 accompanied, is included in it. A trailing edge 3 is shaped so that a slot 106 between the trailing edge and the leading edge 2 is arranged. A front end section 3a the trailing edge 3 and its entire trailing edge surface 104 are shaped so that they are lower than the upper portion of the leading edge 2 , That is, the front end portion 3a the trailing edge 3 is shaped to be relative to the wearer 1 decreases (decreases) with a difference in degree as compared with the rear end portion of the leading edge surface 2a ,

The slot 106 may have a portion extending to the point of coating on the carrier 1 down from a pocket (not shown) tapers or it may have a parallel portion, as shown in the drawing.

In this embodiment, a precoat composition 11 applied using a suitable coating apparatus, ie a commonly used known coating apparatus, example, a gravure, roll, blade, extrusion coating apparatus or the like.

The coating apparatus for applying the precoating composition 11 and the above-mentioned coating apparatus 10 as shown in the drawing are suitably arranged at a predetermined interval. These coating devices may be arranged separately between different pairs of guide rollers or they may be arranged in common between a pair of guide rollers.

Although the overlap angle of the vehicle 1 in the coating apparatus 10 As shown in the drawing, and the gap between the guide rollers are respectively set to generally about 2 to 60 ° and 50 to 300 mm, they are not limited to these values.

The previously applied precoat composition 11 is an organic solvent solution and a liquid with a low viscosity. This prevents the accompanying air from being trapped on the upstream side of the leading edge when the magnetic coating composition 3 is applied so that a good order condition can be maintained.

The term "low viscosity" used in the present invention means a viscosity of not more than 10 mPa.s (10 cP), especially for a liquid viscosity not higher than 10 mPa.s (10 cP) at a shear rate of 46,500 s ^-1 , measured by means of a rotoviscometer. The terminology "coating composition (coating layer)" as used in the present invention means a single magnetic coating composition (magnetic layer), a multilayer structure of magnetic coating compositions (layers), and a magnetic coating composition (magnetic layer) non-magnetic layer combination, which in the case of a magnetic recording medium is at least a magnetic layer. Also, in the case of materials other than the magnetic recording media, a known layer structure can be used.

In the case of a multi-layer coating, as in 6 shown are two slots 106a and 106b through an intermediate block 23 formed, the structure of in 6 However, the coating head shown is substantially equivalent to the structure of in 5 shown coating head. In this case, two kinds of magnetic coating compositions or a magnetic coating composition and a non-magnetic coating composition fed separately and on the two slots 106a and 106b be abandoned.

The characteristic structure of the coating device 110 in this embodiment, that of the front end portion 3a the trailing edge 3 , That is, the front end portion 3a is formed so that the contact angle with respect to the ion exchange water is not smaller than 35 °.

According to the invention, a water-repellent element is used as a material for forming the front end portion of the head in each of the coating devices 110 and 120 used. A material in which the contact angle with respect to the ion exchange water is not smaller than 35 °, preferably not smaller than 40 °, is used as an element. The "contact angle with respect to the ion exchange water" described herein can be determined not only by the quality of the element but also by the surface properties (the degree of surface finish) and the purity of the element. The "contact angle with respect to the ion exchange water" as defined in the present invention is based on the case where an angle between the spherical surface of a water droplet and the surface of an article after the lapse of 15 seconds after the dropping of 2 μl of ion exchange water the surface of the article (the contact angle is viewed from the true side of the subject) is measured by means of a contact angle measuring device CA-D manufactured by Kyowa Keimen-Kagaku Co. in the atmosphere at room temperature of 23 ° C and a humidity of 70%.

In the coating method, in particular, the front end portion 3a the trailing edge 3 shaped like a sharp edge closest to the carrier at the slot outlet portion. The coating composition F coming out of the slot 6 is extruded from the front end portion, while maintaining a delicate balance at the sharp edge-shaped front end portion, so that no smoothing occurs on the downstream side of the front end portion. When the front end section 3a which is a portion having to maintain this delicate balance shaped to satisfy the above numerical value, the coating composition F can be effectively prevented from being around the side of the trailing edge surface 4 For example, in the event that the extrusion pressure of the coating composition or the behavior of the carrier changes.

For a liquid feed system will be according to the quality the coating composition, a known technique applied. Especially in the case of a magnetic coating composition, has the coagulation properties, it is therefore preferred to use a Shearing force to act and not to condense. Especially can the method according to the Japanese Patent Application No. Sho 63-63 601A, according to Japanese Unexamined Patent Publication No. Sho 62-95174A and the like. For example, in the case of the absence of a rotor, such as in Japanese Patent Application No. Sho 63-63601A and the like, the diameter of the piping arrangement between a pump and a coating head preferably not more than 50 mm φ, the pocket diameter of a coating head for a magnetic Composition is preferably 2 to 20 mm φ, the slot width of the coating head for the magnetic composition is preferably 0.05 mm and the slot length is preferably 5 to 150 mm, however, they are not always limited to these values.

To Examples of the invention used carrier belong Paper, plastic films, metal, a resin-coated paper, a Art paper and the like.

One second example for the coating device according to the invention will be described below.

In the second example, a coating apparatus as shown in FIG 5 and the coating composition and the material were the same as those used in the first example, except for the coating apparatus.

It A coating was carried out under the following conditions: the Leading edge width W was 0.5 mm; the slot width t was 0.075 mm; the trailing edge angle was α 45 °; of the Angle Θ between the carrier and the trailing edge surface was 45 °. The difference h in height between the leading edge and the leading end of the trailing edge 0.07 mm.

As the coating head in the coating apparatus, two types of elements having different surface properties were prepared for the three material qualities of stainless steel, hard Metal and ceramic, so that a total of 6 samples were prepared. The location of the formation of streaks caused by the trailing edge contamination was examined to give the results shown in Table II.

In in terms of the degree of surface finish (the surface treatment), the surface properties determined the particular coating device, the surface was up surface treated at the grade indicated in Table II.

Table II

⊚

extreme Verbesserung der Film-Oberflächeneigenschaften

Ο

Verbesserung

Δ

bei der praktischen Verwendung traten keine Probleme auf, obgleich Probleme vorlagen, und

x

bei der praktischen Verwendung lagen Probleme vor.

In the evaluation in Table II mean:

⊚

extreme improvement of film surface properties

Ο

improvement

Δ

there were no problems in practical use, although there were problems, and

x

there were problems in practical use.

Out Table II shows that the banding rate decreases with increasing contact angle and that good results in the practical Use can be achieved regardless of the quality of the element as long as the element used has a contact angle of not less than 35 ° can.

In a third embodiment, as in the 3 and 6 is shown, it is preferable that the surface roughness of the slot inner surface 4 (including the inner surface 4 which are the slits on the intervening block 3a represent), the leading edge surface 5 and the trailing edge surface 6 at the front end portion of the coating head is small, as a result of investigations on the location of the formation of stripes caused by aggregation of the coating composition 7 and by including foreign matter, however, it was surprisingly found that streaks were scarcely formed under the condition that the center line average roughness (Ra) is not larger than 1.0 μm, which is a limit. It is particularly preferred that the average center line roughness (Ra) is not greater than 0.4 μm, and under these conditions less formation of such stripes occurs.

The surface roughness is measured according to Japanese Industrial Standard JIS-B0601 and it is reported as the average centerline roughness, which is generally used. The section value (λc) is 0.25 mm.

Although it is desired that there be no chipping at the leading edge corner portion 9 and at the trailing edge corner portion 10 occurs at the front end portion of the coating head, in the grinding process in practice, a fine chipping occur. As a result of investigations regarding the position of the formation of stripes caused by aggregation of the coating composition mensetzung 7 and by inclusion of foreign matter, therefore, it has been found that stripes having an influence on the quality thereof are scarcely formed under the condition that the size of the chips existing on the entire width of the front end portion of the coating head is not more than 10 μm. The condition that the size of the chips is not larger than 5.0 μm is particularly preferable.

The chips are formed in the grinding process by dropping a part of the particles constituting the front end member at the leading edge corner portion 9 and at the trailing edge bag portion 10 at the front end portion of the coating head or the chips appear in the edge corner portions as fine voids formed in the material sintering process. The size of a splitter can be expressed by the direction of the width of the beam and the direction of the depth thereof. The larger of the size in the width direction and the size in the depth direction relative to the carrier is used here as a fragment size. That is, the sliver size (total width) used here is the maximum sliver size obtained when checking the entire width in the width direction.

at this embodiment it is preferred that the Material for the front end portion of the coating head carbide or Ceramics is.

Although the above-described coating head is disposed between two guide rollers, another coating head for applying a precoating composition may also be used 11 be provided between the coating head and the guide roller on the upstream side of the coating head. The overlap angle in the coating head is about 2 to 60 °. Although the pitch of the guide rollers for forming an overlap in this coating head is generally 50 to 300 mm, it is not limited to this value.

The here used liquid feed system is not subject to any specific restrictions. It will be a familiar one Technique applied for a liquid charging system according to the quality the coating composition. Especially in the case of a magnetic Coating composition having coagulation properties, It is therefore preferable to allow a shearing force to act and not to condense. Particular attention is paid to the Japanese Patent Application No. Sho 63-63601A, Japanese Unexamined Patent Publication No. Sho 62-95 174A and the like. In the case of the absence of a rotor, such as in Japanese Patent Application No. Sho 63-63601A and the like, is the diameter of the piping arrangement between a pump and a coating head preferably not larger than 50 mm φ, the pocket diameter of a coating head for one magnetic composition is preferably 2 to 20 mm φ, the slot width of the coating head for the magnetic composition is preferably 0.05 to 1 mm and the slot length is preferably 5 to 150 mm, however, they are not always limited to these values.

As stated above is in the coating apparatus according to the invention the average centerline roughness (Ra) both in the slot inner surface than also in the leading edge surface and in the trailing edge surface at the front end portion of the extrusion coating head for the production a coating layer not bigger than 1.0 μm. Therefore, even for the case that the Coating composition not compressed at the time of application the stream of coating composition is hardly disordered, such that a coating layer with excellent surface properties can be obtained. Because the coating composition without any When compression is applied, hardly any fluid aggregation occurs by the projection of the coating composition, so that products with excellent surface properties, which are free from streaking due to inclusion of foreign matter caused to be produced in a stable manner. There the fragment size in the Leading edge corner and in the trailing edge corner portion at the front end portion the extrusion coating head for forming a coating layer not bigger than 10 μm, furthermore, the stream of the coating composition comes as a meniscus, starting from the front end portion of the coating head, hardly in disorder, so that products with excellent surface properties, which are free from banding caused by the aggregation the composition and caused by the inclusion of foreign material will be able to be obtained in a stable manner.

below be the new effects of the device according to the invention by means of a third example closer explained.

After this the components of the coating composition given below in a ball mill introduced, was mixed therein and sufficiently dispersed, became Epoxy resin (epoxy equivalent 500) in an amount of 30 parts by weight, mixed uniformly and dispersed to prepare a magnetic coating composition (magnetic dispersion composition).

If the viscosity the magnetic coating composition thus prepared by means of of a rotoviscometer, were measured at the respective Shear rates specified thixotropic viscosities.

In In the third example, the same materials were used as in the first example with the exception of the carrier material, hereinafter is specified.

A polyethylene terephthalate film having a thickness of 15 μm and a width of 500 mm was used as a support. The carrier was prepared to run at a tension of 10 kg / total width and at a coating speed of 600 m / min. The positions of the band formations were compared with each other while the average center line roughness (μM Ra) of the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 of extrusion type coating head as shown in FIG 1 are changed in the three stages 0.4 .mu.m, 1.0 .mu.m and 2.0 .mu.m and the splitter sizes (microns maximum) at the leading edge corner portion 9 and the trailing edge corner section 10 were changed in the three stages 5 microns, 10 microns and 20 microns. The results are given in Table III.

Table III

As shown in Table III, when the surface roughness Ra (μm) is selected to be 2.0 μm at the slot inner surface 4 , the leading edge surface 5 and the trailing edge surface 6 is, ie in the respective cases of the extruder no. (3), (4) and (5) 10 or more stripes are formed, or a considerable number of stripes are formed when stripes are counted on their properties without any problems, and the quality of the products is undesirably greatly impaired. In addition, in the after-treatment of the coating method before completion as a product, the cause of a severe disturbance which may destroy the device, for example, erroneous winding, cutting caused by creasing. The section value (λc) is 0.25 mm.

When the chip size (μm) is 20 μm in the leading edge corner portion 9 or in the trailing edge corner section 10 is, ie in the respective cases of the extruder no. (7) and (8), the banding so remarkable that a considerable number of stripes are formed if stripes are counted without problems in their properties. The quality of the products is thereby adversely affected in an undesirable manner. In addition, in the after-treatment of the coating method before completion as a product, the cause of a large disturbance, whereby the device can be destroyed, for example, an erroneous winding, a cutting caused by creasing. Strips where problems occur are particularly close to the positions where splinters (greater than 10 μm) occur in the extruder.

on the other hand occurs in the respective cases the extruder no. (1), (2) and (3) no streaking, the problems relating to on the quality of the products and in the post-treatment, so that excellent Magnetic recording media are obtained. Especially in the case of extruder no. 1 is for the case that the surface roughness and the fragment size is 0.4 μm or 5 μm, to find no coating strip, so that an excellent magnetic recording medium can be obtained.

Claims (5)

Coating device for applying a uniformly thick material composition to a moving support ( 1 ) with an extruder head comprising: - a leading edge ( 2 ), which are in the direction of movement of the carrier ( 1 ) front side of the extruder head and a the carrier ( 1 ) facing surface ( 5 ), - a trailing edge ( 3 ), which are in the direction of movement of the carrier ( 1 ) rear side of the extruder head is arranged and a the carrier ( 1 ) facing surface ( 6 ) and - a gap ( 8th ) with inner surfaces ( 4 ), which is between the leading edge ( 2 ) and the trailing edge ( 3 ) and through which the material composition is extrudable, characterized in that in the surfaces ( 5 . 6 ) and the inner surfaces ( 4 ) Waves along the direction of the width of the carrier ( 1 ) are formed. Coating device according to claim 1, characterized characterized in that the waves have a length of 0.2 μm or less exhibit. Coating device according to claim 1 or 2, characterized in that the trailing edge ( 3 ) has a surface facing the carrier, which, in comparison to the surface of the leading edge ( 2 ), step back towards the carrier. Coating device according to at least one of claims 1 to 3, characterized in that the gap-side edge ( 10 ) of the trailing edge ( 3 ) is acute-angled. Coating device according to at least one of claims 1 to 4, characterized in that the carrier ( 1 ) facing surface ( 5 ) of the leading edge ( 2 ) is curved towards the support to prevent air, along with a precoat composition, from being mixed between the leading edge (FIG. 2 ) and the carrier ( 1 ).