JPH05309317A - Coating method - Google Patents

Abstract

PURPOSE:To obtain a coating method capable of eliminating the trouble due to the shaving of both side end parts (tab parts) of a flexible support at the time of the coating of the support with a coating solution and not generating the bonding trouble of the tab parts in a treatment process after coating. CONSTITUTION:In a coating method using an extrusion type coating device extruding coating solutions 4, 5 from slits to apply the same to the surface of a continuously moved flexible support, an undercoat layer 2 of a dry film is formed on the coated surface of the flexible support 1 in predetermined width and a solvent 3 is preliminarily applied to both edge parts of the undercoat layer and the outsides of their edge parts. When the solvent 3 is in a wet state, the coating solution 4 forming the lowermost layer is applied to the area inside the solvent coated parts in the lateral direction of the support in width narrower than that of the undercoat layer 2 in a state not in contact with the solvent 3 and both end parts in the lateral direction of the coating solution 5 forming the layer above the lowermost layer 4 are positioned on the layers of the solvents and the coating width thereof is made larger than that of the undercoat layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for coating a coating liquid having a uniform thickness on the surface of a continuously moving flexible support, and more particularly to a coating method using an extrusion type coating apparatus. The present invention relates to a coating method suitable for use in manufacturing a photographic film or a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a magnetic recording medium such as a magnetic disk or a magnetic tape or a photographic film,
A flexible support is coated with a predetermined coating liquid to manufacture it. As this coating method, for example, various coating methods such as a method using a roll type coating apparatus, a method using a bead type coating apparatus, a method using a slide coating type coating apparatus, a coating method using an extrusion type coating apparatus, etc. However, among them, the coating method using an extrusion type coating device is often used. The basic configuration of the extrusion type coating apparatus is that a back edge is provided on the upstream side and a doctor edge is provided on the downstream side with respect to the moving direction of a flexible support such as a film, and the back edge and the The coating liquid is extruded onto the surface of the support through a slit formed between the support and the edge, and a predetermined meniscus of the coating liquid is formed between the support and the edge, and the distance between the support and the edge is increased. Is kept constant and is applied.

However, in the basic structure, the support and the edge are separated from each other by a constant distance during the coating process, but the surface of the support, in other words, the coating surface is in contact with the edge. Occurs. This contact occurs at the ears (both ends) of the support, and there is a problem that the support is easily scraped. Therefore, the applicant of the present application has proposed that the problems described above be solved by Japanese Patent Laid-Open No. 61-2.
The coating method disclosed by Japanese Patent No. 57268 was proposed. This published coating method is such that, in the ear portion, a solvent is previously coated on a portion where the edge of the coating device and the support are directly rubbed, and a wet solvent is applied between the edge and the support. The interposition was made to reduce the contact force to prevent the scraping. On the other hand, taking a magnetic recording medium as an example, one of the recent technical trends is thinning of the layer, and therefore the support itself is thin and the behavior during running is easily destabilized. Therefore, even the disclosed coating method may cause abrasion.

[0004]

The scraping can be prevented by increasing the amount of the solvent applied to the ears, but when the amount of the solvent is increased, a situation of mixing with the coating liquid occurs. However, if there is a certain degree of mixing, the applicant of the present invention discloses that
It can be improved by the coating method disclosed in Japanese Patent No. 107381. However, when the mixing amount is large and the amount of the solvent is extremely large and the overflow becomes remarkable, the solvent stains the edge. This edge stain is one of the causes of the occurrence of streaks on the surface of the coating surface, and further causes a transfer failure,
It is not preferable because it may lead to liquid return.

In order to solve such a problem, the applicant of the present application has proposed a coating method as disclosed in Japanese Patent Laid-Open No. 3-116524. That is, by applying a polymer, a monomer, or a UV resin to at least the ear portion, the contact force between the edge of the coating device and the support is reduced, and abrasion is prevented. However, the polymer or the like applied to the ears causes a failure such as ear adhesion in a later step, and the support is thin as described above, so that the support strength is weakened and the support is weakened. It sometimes caused a serious accident such as disconnection. An object of the present invention is to eliminate a failure due to abrasion of both end portions (ears) when applying a coating liquid to a flexible support, and to cause adhesion failure of the ears in a processing step after application. The object is to provide a coating method that does not allow it.

[0006]

The above object of the present invention is to apply a coating using an extrusion type coating apparatus for coating a coating liquid on a surface of a continuously moving flexible support by pushing it out from a slit. In the method, after forming a dry film undercoat layer with a predetermined width on the coated surface of the support, a solvent is applied to both edges and the outside of the edge of the undercoat layer, and the solvent is in a wet state. Among them, the coating solution for forming the lowermost layer is applied narrower than the undercoat layer in a state of being in non-contact with the solvent on the widthwise inner side of the support than the solvent, and then higher than the lowermost layer. The coating solution is formed by arranging both widthwise edges of the coating liquid for forming the layer on the solvent and coating the coating width wider than that of the undercoat layer.

[0007]

Embodiments of the present invention will be described below with reference to FIG. Note that this embodiment shows an example of application to a magnetic recording medium, and FIG. 1 is a cross-sectional view of the magnetic recording medium immediately after the coating step in this embodiment, cut in the width direction thereof,
FIG. 2 is a perspective view of the solvent coating device. FIG. 3 is a perspective view of the extrusion type coating apparatus, and FIG. 4 is B- of FIG.
It is a B line sectional view. First, the cross-sectional structure of a magnetic recording medium coated with the magnetic coating liquid according to this embodiment will be described with reference to FIG. On the coated surface of the support 1, a magnetic layer formed by a magnetic coating solution and a highly adhesive undercoat layer 2 that firmly bonds the support 1 to each other are coated, and are formed as a dried dry film. .. Then, the undercoat layer 2 is not applied to the entire area of the width W of the support 1, but to the non-application areas 2a on both side ends.
Is left. The solvent 3 is applied so as to cover the non-coated area 2a and both ends of the undercoat layer 2, and both ends of the support 1 are covered with the solvent 3. On the upper surface of the undercoat layer 2, a magnetic liquid 4 forming a lowermost magnetic layer is applied in a region surrounded by the solvent 3 from both sides. As will be described later, when the magnetic liquid 4 is applied, a gap G (the gap G is not actually formed after the application) is formed between the magnetic liquid 4 and the already applied solvent 3. Applied to.

A magnetic liquid 5 is further applied onto the magnetic liquid 4. The magnetic liquid 5 is applied so that both edges (both ends) of the magnetic liquid 5 project over the solvent 3 and wider than the undercoat layer 2.

Next, the coating method will be described with reference to FIGS. First, application of the solvent 3 will be described with reference to FIG. The undercoat layer 2 has already been applied to the surface (lower surface in FIG. 2) of the support 1 and dried.
The support 1 on which the dry film of the undercoat layer 2 is formed is conveyed in a predetermined direction. The coating device 10 shown in FIG. 2 coats the both ends of the support 1 with the solvent 3. For example, a reverse roll 11 having a structure arranged in the support width direction is placed in a coating liquid pan 12. The pair of reverse rolls 11 are provided so that the gap between the pair of reverse rolls 11 is set so that the solvent 3 can be applied to desired positions on both end portions of the support 1. Then, by rotating the reverse roll 11, the solvent 3 supplied or stored in the coating liquid pan 12 is continuously applied to the surface of the support 1.

That is, when applying the solvent 3,
The both sides of the surface of the support 1 on which the undercoat layer 2 is formed are conveyed so as to be in contact with the reverse roll 11. As a result, as shown on the downstream side in FIG. 2, the solvent 3 is applied in a strip shape on both end portions of the non-application area 2a and the undercoat layer 2. Then, while the solvent 3 is in a wet state, the magnetic liquids 4 and 5 are applied by, for example, the application device 100 shown in FIG. The coating device 100 shown in FIG. 3 is a device capable of performing simultaneous multilayer coating of the magnetic liquids 4 and 5, and is installed on the downstream side of the coating device 10. The coating device 100 includes a slit 10 for discharging the magnetic liquids 4 and 5.
1,102 has two doctor edges 104,105 and 1
It is formed by one back edge 106. However, since the coating width of the magnetic liquid 4 is narrower than the coating width of the magnetic liquid 5 as described with reference to FIG. 1, the length of the slit 101 is longer than that of the slit 102. Has been done. Further, the length of the slit 102 is shorter than the width of the undercoat layer 2,
The length of 01 is configured to be long.

In the coating by the coating device 100, when the support 3 is conveyed with the solvent 3 coated thereon, as shown in FIG. 4, the magnetic liquids 4, 5 are discharged from the slits 101, 102. However, since the solvent 3 is applied to the support 1 in advance, the ear portion of the support 1 does not come into direct contact with the doctor edges 104, 105 and the back edge 106. In addition, since the gap G is formed between the magnetic liquid 4 and the solvent 3 when the magnetic liquid 4 in the lower layer is applied, the magnetic liquid 4 can be applied even when a large amount of the solvent 3 is applied. The stable state of the meniscus can be maintained and a sufficient effect of preventing ear abrasion can be exerted. Furthermore, since the magnetic liquid 5 in the upper layer is applied wider than the width of the undercoat layer 2, the solvent 3 is evaporated and the uppermost layer of the magnetic liquid 5 is evaporated when dried in the drying step after this application step. Covers the undercoat layer 2. As a result, the undercoat layer 3
Since the film is not exposed, it is possible to avoid the conventional problem of adhesion between the supports due to the undercoat layer 2 even after the support 1 is wound up.

The magnetic liquids 4 and 5 may have the same composition or different compositions. Further, as the solvent 3, for example, cyclohexanone, methyl cellosolve, acetone, methanol, trifluoroacetic acid or the like can be used.

Further, the composition of the magnetic liquid used in this embodiment will be described in more detail. As a thermoplastic resin, the softening temperature is 150 ° C. or less and the average molecular weight is 10,000.
0 to 300,000 and a polymerization amount of 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 Polymer, 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 acrylonitrile copolymer, polyamide resin, poei vinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), Styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber thermoplastic resins, and mixtures thereof are used.

As the thermoplastic 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, those which do not soften or melt before the resin is thermally decomposed are desirable. 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, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacryl Mixtures of acid copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycol / high molecular weight diols / triphenylmethane triisocyanates, polyamide resins and mixtures thereof. 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.

As the dispersant, caprylic acid, capric acid,
Fatty acids having 12 to 18 carbon atoms such as lauric acid, myristic acid, valmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and stearolic acid (R ₁ COOH, R ₁ is 11 to 11 carbon atoms) 17 alkyl or alkenyl groups): Alkali metals (Li, Na, K, etc.) or alkaline earth metals (Mg,
Ca, Ba) metal soap: Fluorine-containing compound of the above fatty acid ester: Amide of the above fatty acid: Polyalkylene oxide alkyl phosphate ester: Lecithin: Trialkylpolyolefin quaternary ammonium salt: (Alkyl is carbon number 1 to 5, olefins such as ethylene and propylene): 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 (alkyl 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)
Silicone oil such as graphite), dielectric fine powder such as graphite: 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 double bond is bonded to terminal carbon, carbon number about 20): monobasic fatty acid having 12 to 20 carbon atoms and 3 carbon atoms It is possible to use fatty acid esters, fluorocarbons and the like consisting of ˜12 monohydric alcohols.

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.

As the antistatic agent, conductive fine powder such as carbon black or carbon black graft polymer:
Natural surfactants such as saponin: alkylene oxide-based, glycerin-based, glycidol-based, etc. nonionic surfactants: higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, cations such as phosphonium or sulfonium Surfactant: Anionic surfactant containing an acidic group such as carboxylic acid group, sulfonic acid group, phosphoric acid group, sulfuric acid ester group, phosphoric acid ester group, etc. Amphoteric activators and the like 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 carbon hydride) such as xylene: methylene chloride, ethlene chloride, carbon tetrachloride, chlorinated hydrocarbon such as chloroform, ethylene chlorohydrin, dichlorobenzene and the like. The amount of solvent is 2 for magnetic fine powder.
~ 3 times. The dispersant is 0.5 to 20 parts by weight, the lubricant is 0.2 to 20 parts by weight, the abrasive is 0.5 to 20 parts by weight, and the conductive fine particles used as the antistatic agent are 100 parts by weight of the binder. The powder is 0.2 to 20 parts by weight, and the surfactant used as an antistatic agent is 0.1 to 10 parts by weight. Magnetic powder and the aforementioned binder, dispersant, lubricant,
An abrasive, an antistatic agent, a solvent and the like are kneaded to form a magnetic paint.

Examples of the material of the support include 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, polycarbonate and polyamide. There are resins, films of plastic shutters such as polysulfone, metal materials such as aluminum and copper, and ceramics such as glass. These supports are previously corona discharge treated, plasma treated,
Pretreatment such as undercoating treatment, heat treatment, metal vapor deposition treatment, and calcare treatment may be performed. The support may be of any desired shape.

The coating apparatus 100 is installed between two guide rolls, the wrap angle of the support in the coating apparatus 100 is about 2 ° -60, and the coating apparatus 100 is also used.
In the above, the guide roll span for forming the wrap can be set to, for example, about 50 to 300 mm, but is not limited thereto. For the liquid feeding system, a known technique depending on the properties of the coating liquid is 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, for example, the pipe diameter is 50 mm or less, the pocket diameter (liquid reservoir inner diameter) of the coating device is 2 to 20 mm, the slit width is 0.05 mm to 1 mm, and the length from the liquid reservoir to the slit tip is 5 mm to 150 mm. Yes, but it is not limited to this.

An apparatus for carrying out the coating method of the present invention is shown in FIG.
It is not limited to the device shown in FIG. 3 and the devices shown in FIGS. 3 and 4, and various devices can be used. In the present invention, the coating of the magnetic liquid does not have to be simultaneous multi-layer coating, and can be naturally applied to the case of a coating liquid having three or more layers.

[0023]

As described above, according to the present invention, after forming a dry film undercoat layer with a predetermined width on the coated surface of a support, a solvent is applied to both edges of the undercoat layer and the outside of the edge. While the solvent is in a wet state, the coating solution for forming the lowermost layer is made narrower than the undercoat layer in a state in which it is in non-contact with the solvent on the widthwise inner side of the support than the solvent. It is a method of applying the coating, and then positioning both widthwise edges of the coating liquid forming a layer above the lowermost layer above the solvent, and applying the coating width wider than the undercoat layer. .. Therefore, when the coating liquid is discharged from the slit for applying the coating liquid in a state where the solvent is applied to the support, the solvent is already applied to the support, so the support is The ears of the do not directly contact the edge surface of the coating device, and when applying the coating liquid on the lower layer side,
Since a gap is formed so that the coating liquid and the solvent do not come into contact with each other, even when a large amount of the solvent is coated, the stable state of the meniscus of the coating liquid does not collapse, and a sufficient ear abrasion preventing effect is exhibited. can do. Furthermore, since the coating solution on the upper layer side is applied wider than the width of the undercoat layer, when dried by the drying step after this coating step, the solvent evaporates and the uppermost layer formed by the coating solution becomes As it covers the undercoat layer, it is possible to avoid the exposure of the undercoat layer, and avoid the problem of adhesion between the supports due to the undercoat layer as in the conventional case even after the support is wound up. can do.

[0024]

EXAMPLES The effects of the present invention can be further clarified by the following examples. The components shown in Table 1 were placed in a ball mill and thoroughly mixed and dispersed. Then, 30 parts by weight of an epoxy resin (epoxy equivalent of 500) was added and uniformly mixed to obtain the magnetic liquids 4 (lower layer) and 5 (upper layer). ).

[0025]

[Table 1]

As the coating apparatus, the extrusion type coating apparatus 100 described with reference to FIGS. 3 and 4 was used, and the support 1 was made of polyethylene terephthalate film having a thickness of 9 μm. .. The size of the coating device is as shown in Table 2, but the coating speed is 300
m / min, tension 20 kgf / m, coating thickness of the upper layer is 1.0 μm (corresponding to coating amount of 5 cc / m ² ), lower layer is 3.0 μm (coating amount of 15 cc / m ² ).
² equivalent).

[0027]

[Table 2]

The setting of the coating width of the upper and lower layers is performed by dividing the central axis, and the position of the solvent in the ears is 0 to 3 depending on the distance from the end of the lower layer.
The coating was performed by changing the thickness in the range of mm.

[0029]

[Table 3]

The evaluation method was as follows: coating for 20 minutes (6000 m) and observing mainly the abrasion of the base.
Table 3
The evaluation results as shown in are obtained. As a result, good results could be obtained when the conditions of the present invention were satisfied.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium to which the present invention is applied.

FIG. 2 is a perspective view of a coating device for coating a solvent according to the present invention.

FIG. 3 is a perspective view of an extrusion type coating apparatus for coating a coating liquid according to the present invention.

FIG. 4 is a sectional view of a portion taken along the line BB in FIG.

[Explanation of symbols]

 1 Support 2 Undercoat layer 3 Solvent 4,5 Magnetic liquid 10 Solvent coating device 11 Reverse roll 12 Coating liquid pan 100 Extrusion type coating device 101, 102 Slits 104, 105 Doctor edge 106 Back edge G Gap

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

Claims (1)

[Claims] 1. A coating method using an extrusion-type coating device, wherein a coating liquid is extruded from a slit and coated on the surface of a flexible support which is continuously moved, in a predetermined width on the coating surface of the support. After forming a dry film undercoat layer with, a solvent is applied to both edges and the outside of the edge of the undercoat layer,
While the solvent is in a wet state, while applying the coating liquid forming the lowermost layer to the solvent widthwise inner side of the solvent than the solvent in a state of non-contact with the solvent, the coating liquid is narrower than the undercoat layer,
After that, both widthwise edges of the coating liquid for forming a layer above the lowermost layer are positioned on the solvent, and the coating width is applied wider than the undercoat layer. ..