JP2961676B2 - Application method - Google Patents

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 solution 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 producing a photographic film or a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, when a magnetic recording medium such as a magnetic disk or a magnetic tape or a photographic film is manufactured,
Production is performed by applying a predetermined coating solution to a flexible support. As the coating method, for example, a method using a roll-type coating device, a method using a bead-type coating device, a method using a slide coat-type coating device, a coating method using an extrusion-type coating device, etc. Among them, a coating method using an extrusion type coating apparatus is widely used. The basic configuration of the extrusion type coating apparatus is such that a back edge is provided on the upstream side and a doctor edge is provided on the downstream side in the moving direction of the flexible support such as a film, and the back edge and the back edge are provided. The coating liquid is extruded onto the surface of the support from a slit formed between the support and the edge of the support, and a predetermined meniscus of the coating liquid is formed between the support and the edge while the gap between the support and the edge is formed. Is applied so as to be kept constant.

[0003] However, in the above-mentioned basic configuration, the support and the edge are separated from each other at a fixed interval during the coating process, but the surface of the support, in other words, the coating surface contacts the edge. Occurs. This contact occurs at the ears (both ends) of the support, and there is a problem that the support is likely to be scraped. Therefore, the applicant of the present application has disclosed Japanese Patent Application Laid-Open No.
No. 57268 has proposed a coating method. In this disclosed coating method, in the ear portion, a solvent is pre-applied to a portion where the edge of the coating device and the support directly rub, and a wet solvent is applied between the edge and the support. The contact force was reduced by intervening to prevent the scraping. On the other hand, taking a magnetic recording medium as an example, one of the technical trends in recent years is a thin layer, and as a result, the support itself is also thin and the behavior during running tends to be unstable, and it is delicate. For this reason, even with the disclosed coating method, shaving may occur.

[0004]

The shaving can be prevented by increasing the amount of the solvent applied to the ears. However, if the amount of the solvent is increased, the shavings may be mixed with the coating solution. However, if the mixture is to a certain extent, the applicant of the present application has disclosed in
This can be improved by the coating method disclosed in Japanese Patent No. 107381. However, when the mixing amount is large, if the amount of the solvent is extremely large and overflow becomes remarkable, the solvent stains the edge. This edge stain is one of the causes of streaks on the surface of the coating surface, and further causes transfer failure and
It is not preferable because it leads to the occurrence of liquid return.

In order to solve such a problem, the present applicant has proposed a coating method as disclosed in Japanese Patent Application Laid-Open No. 3-116524. That is, by applying a polymer, a monomer, or a UV resin to at least the ears, the contact force between the edge of the coating device and the support is reduced, and the scraping 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 strength of the support is becoming weaker because the support is thinner as described above. Serious accidents such as cutting could be caused. SUMMARY OF THE INVENTION An object of the present invention is to solve a problem caused by scraping of both side edges (ears) when applying a coating liquid to a flexible support, and to cause an adhesion failure of ears in a processing step after application. An object of the present invention is to provide an application method that does not cause the application.

[0006]

An object of the present invention is to provide a coating method using an extrusion type coating apparatus for applying a coating solution by extruding a coating solution from a slit onto a surface of a continuously moved flexible support. In the method, after forming an undercoat layer of a dry film with a predetermined width on the coating surface of the support, a solvent is applied to both edges and outside of the edges of the undercoat layer, and the solvent is in a wet state. In the meantime, the coating liquid for forming the lowermost layer is applied to a width smaller than that of the undercoat layer in a non-contact state with the solvent on the inner side of the width of the support than the solvent, and thereafter, above the lowermost layer. This is achieved by a coating method in which both edge portions in the width direction of the coating liquid for forming the above layer are positioned on the solvent, and the coating width is wider than that of the undercoat layer.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment 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 in the width direction of the magnetic recording medium immediately after a coating process in this embodiment,
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.
It is a B sectional view. First, a sectional structure of a magnetic recording medium coated with a magnetic coating liquid according to the present embodiment will be described with reference to FIG. A magnetic layer formed of a magnetic coating solution and a highly adhesive undercoat layer 2 for firmly bonding the support 1 are applied to the coating surface of the support 1, and have already been 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 the non-application area 2 a
Is left. The solvent 3 is applied so as to cover the non-coating 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 constituting a lowermost magnetic layer is applied to a region surrounded from both sides by the solvent 3. As described later, when the magnetic liquid 4 is applied, a gap G is formed between the applied solvent 3 and the solvent 3 (the gap G is not actually formed after the application). Applied to

A magnetic liquid 5 is further applied on the magnetic liquid 4. The magnetic liquid 5 is applied so that both edges (both ends) protrude above the solvent 3 and is wider than the undercoat layer 2.

Next, the coating method will be described with reference to FIGS. First, the application of the solvent 3 will be described with reference to FIG. The undercoat layer 2 has already been applied to the surface of the support 1 (the lower surface in FIG. 2) and dried.
The support 1 on which the dry film of the undercoat layer 2 is formed is transported in a predetermined direction. The coating apparatus 10 shown in FIG. 2 is for applying the solvent 3 to both ends of the support 1, and for example, a reverse roll 11 having a structure arranged in the width direction of the support is placed in a coating liquid pan 12. The distance between the pair of reverse rolls 11 is set such that the solvent 3 can be applied to desired positions on both side ends of the support 1. 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 the solvent 3 is applied,
The support 1 is conveyed such that both side edges of the surface on which the undercoat layer 2 is formed are 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 to the non-application area 2 a and both end portions of 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, an application device 100 shown in FIG. The coating apparatus 100 shown in FIG. 3 is an apparatus capable of simultaneously applying the magnetic liquids 4 and 5 in a multi-layer manner, and is provided downstream of the coating apparatus 10. The coating apparatus 100 includes a slit 10 for discharging the magnetic liquids 4 and 5.
1,102 are two doctor edges 104,105 and 1
Formed by one back edge 106. However, since the application width of the magnetic liquid 4 is narrower than the application width of the magnetic liquid 5 as described with reference to FIG. 1, the length of the slit 101 is formed longer than the length of the slit 102. Have been. Further, the length of the slit 102 is shorter than the width of the undercoat layer 2,
The length of 01 is long.

In the coating by the coating device 100, when the support 3 is conveyed in a state where the solvent 3 is coated, the magnetic liquids 4 and 5 pass through the slits 101 and 102 as shown in FIG. Since the solvent 3 is applied to the support 1 in advance, the ears of the support 1 may not directly contact the doctor edges 104 and 105 and the back edge 106. When the magnetic liquid 4 in the lower layer is applied, a gap G is formed between the magnetic liquid 4 and the solvent 3. Thus, a sufficient effect of preventing ear shaving can be exhibited without deteriorating the stable state of the meniscus. Furthermore, since the upper magnetic liquid 5 is applied wider than the width of the undercoat layer 2, when dried in a drying step after this coating step, the solvent 3 evaporates and the uppermost layer of the magnetic liquid 5 Covers the undercoat layer 2. As a result, the undercoat layer 3
Is not exposed, so that even after the support 1 is wound up, it is possible to avoid the problem of adhesion between the supports by the undercoat layer 2 as in the related art.

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

The composition of the magnetic liquid used in the present embodiment will be described in more detail. The thermoplastic resin has a softening temperature of 150 ° C. or less and an average molecular weight of 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, acrylate acrylonitrile copolymer Polymer, acrylate vinylidene chloride copolymer, acrylate styrene copolymer, methacrylate acrylonitrile copolymer, methacrylate vinylidene chloride copolymer, methacrylate styrene copolymer, urethane elastomer, nylon-
Silicone resin, nitrocellulose-polyamide resin,
Polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, poyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), Styrene butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubber-based 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. When the composition for forming a magnetic layer is applied, dried, and heated, these resins undergo reactions such as condensation and addition to have an infinite molecular weight. Can be a big one. Further, among these resins, it is preferable 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, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacryl Examples include a mixture of an acid copolymer and a diisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, a urea formaldehyde resin, a mixture of a low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, a polyamide resin, and a mixture thereof. As the ferromagnetic fine powder and solvent dispersed in the binder, and the dispersant, lubricant, abrasive, antistatic agent, nonmagnetic support and the like as additives, those conventionally used can be used in the same manner.

As dispersants, caprylic acid, capric acid,
Fatty acids having 12 to 18 carbon atoms such as lauric acid, myristic acid, barmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, 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,
Metal soap consisting of Ca, Ba): Fluorine-containing compound of the above fatty acid ester: Amide of the above fatty acid: Polyalkylene oxide alkyl phosphate: Lecithin: Trialkyl polyolefinoxy quaternary ammonium salt: (Alkyl is carbon number 1 to 5, olefins such as ethylene and propylene). In addition, higher alcohols having 12 or more carbon atoms, and sulfate esters and the like can also be used.

As the lubricant, the above-mentioned dispersant also has its effect, but dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxy polysiloxane (alkyl has 1 to 4 carbon atoms), monoalkyl Monoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms), phenylpolysiloxane, fluoroalkylpolysiloxane (alkyl has 1 to 5 carbon atoms)
Fine powders such as silicon oil, graphite, etc .: inorganic fine powders such as molybdenum disulfide, tungsten dioxide: plastic fine powders such as polyethylene, polypropylene, polyethylene vinyl chloride copolymer, polytetrafluoroethylene: α- Olefin polymer: unsaturated aliphatic hydrocarbon liquid at room temperature (α-olefin having a double bond 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 composed of up to 12 monohydric alcohols, fluorocarbons and the like can be used.

Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet,
Emery (main component: corundum and magnetite) or the like is used.

As the antistatic agent, conductive fine powders such as carbon black and carbon black graft polymer:
Natural surfactants such as saponins: alkylene oxide-based, glycerin-based, glycidol-based, nonionic surfactants: higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, cations such as phosphonium or sulfoniums Surfactant: Anionic surfactant containing acidic group such as carboxylic acid group, sulfonic acid group, phosphoric acid group, sulfate group, phosphate group, etc .: Amino acid, aminosulfonic acid, sulfuric acid or phosphate of amino alcohol, etc. An amphoteric activator or the like is used.

As the organic solvent used for the coating solvent, 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: benzene ,toluene,
Tar-based (aromatic hydrogenated hydrocarbons) such as xylene: chlorinated hydrocarbons such as methylene chloride, ethulene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene. The amount of the solvent is 2
~ 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 an 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 binders, dispersants, lubricants,
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, polycarbonates and polyamides. Examples include plastic shutter films such as resin and polysulfone, metal materials such as aluminum and copper, and ceramics such as glass. These supports are pretreated by corona discharge treatment, plasma treatment,
A pretreatment such as an undercoating treatment, a heat treatment, a metal deposition treatment, and a calcare treatment may be performed. The support may be of any desired shape.

The coating device 100 is installed between two guide rolls. The wrap angle of the support in the coating device 100 is about 2 ° to 60.
In (2), the guide roll span for forming the wrap may be, for example, about 50 to 300 mm, but is not limited thereto. As the liquid feeding system, a known technique according to 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 a shearing force that does not cause coagulation. Specifically, for example, the pipe diameter is 50 mm or less, the pocket diameter (liquid pool inner diameter) of the coating apparatus is 2 to 20 mm, the slit width is 0.05 mm to 1 mm, and the length from the liquid pool to the slit tip is 5 mm to 150 mm. But can be, but not limited to.

An apparatus for carrying out the coating method of the present invention is shown in FIG.
However, the present invention is not limited to the devices shown in FIGS. 3 and 4 and various devices can be used. In the present invention, the application of the magnetic liquid does not have to be a simultaneous multilayer coating, and is naturally applicable to the case of a coating liquid of three or more layers.

[0023]

As described above, according to the present invention, after forming an undercoat layer of a dry film with a predetermined width on the coating surface of a support, a solvent is applied to both edges of the undercoat layer and to the outside of the edges. While the solvent is in a wet state, the coating liquid for forming the lowermost layer is narrower than the undercoat layer in a state in which the solvent is not in contact with the solvent on the inside of the support width than the solvent. A method in which both edges in the width direction of the coating liquid forming a layer above the lowermost layer are positioned on the solvent, and the coating width is wider than that of 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 coated on the support, since the solvent is already applied to the support, the support is The ear part does not directly contact the edge surface of the coating device, and when applying the coating liquid on the lower layer side,
Since a gap where the coating liquid and the solvent are not in contact with each other is formed, even when a large amount of the solvent is applied, the stable state of the meniscus of the coating liquid is not disrupted, and a sufficient effect of preventing ear shaving is exhibited. can do. Furthermore, since the coating liquid on the upper layer side is applied wider than the width of the undercoat layer, when dried in a drying step after this coating step, the solvent evaporates and the uppermost layer of the coating liquid becomes Since the undercoat layer is covered, exposure of the undercoat layer can be avoided, and even after the support is wound up, problems of adhesion between supports by the undercoat layer as in the related art can be avoided. can do.

[0024]

EXAMPLES The effects of the present invention can be further clarified by the following examples. After each component of the composition shown in Table 1 was sufficiently mixed and dispersed in a ball mill, 30 parts by weight of an epoxy resin (epoxy equivalent: 500) was added and uniformly mixed, and the mixture was uniformly mixed with the magnetic liquids 4 (lower layer) and 5 (upper layer). ).

[0025]

[Table 1]

The coating apparatus used was the extrusion type coating apparatus 100 described with reference to FIGS. 3 and 4. The support 1 was made of a polyethylene terephthalate film having a thickness of 9 μm. . Table 2 shows the dimensions of the coating apparatus.
m / min, tension: 20 kgf / m, coating thickness: upper layer: 1.0 μm (equivalent to 5 cc / m ² ), upper layer: 3.0 μm (equivalent to 15 cc / m)
² equivalent).

[0027]

[Table 2]

The application width of the upper and lower layers is set to the central axis distribution, and the position of the solvent in the ear part is 0 to 3 in terms of the distance from the end of the lower layer.
The coating was performed while changing the thickness in the range of mm.

[0029]

[Table 3]

The evaluation method was as follows. The coating was performed for 20 minutes (6000 m), and the observation was made mainly on the shaving of the base.
Observed after 3 hours in a rolled state, Table 3
Evaluation results as shown in the following were obtained. Thereby, good results could be obtained when the conditions of the present invention were satisfied.

[Brief description of the 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 applying a coating liquid in the present invention.

FIG. 4 is a sectional view of a portion taken along line BB in FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 support 2 undercoat layer 3 solvent 4,5 magnetic liquid 10 solvent coating device 11 reverse roll 12 coating solution pan 100 extrusion type coating device 101,102 slit 104,105 doctor edge 106 back edge G gap

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mikio Tomaru 2-12-1, Ogimachi, Odawara City, Kanagawa Prefecture Inside Fuji Photo Film Co., Ltd. (56) References JP-A-5-293425 (JP, A) Special Table Hei 3-500858 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) B05D 1 / 26,1 / 36 G11B 5 / 84,5 / 842 B05C 5/02

Claims (1)

(57) [Claims] In a coating method using an extrusion-type coating apparatus for applying a coating solution by extruding a coating solution from a slit onto a surface of a flexible support that is continuously moved, a predetermined width is applied to a coating surface of the support. After forming an undercoat layer of a dry film with, a solvent is applied to both edges and the outside of the edges of the undercoat layer,
While the solvent is in a wet state, the coating liquid for forming the lowermost layer is coated more narrowly than the undercoat layer in a state in which the solvent is not in contact with the solvent on the inside of the support width than the solvent,
Thereafter, the width direction both edges of the coating liquid forming a layer above the lowermost layer are positioned on the solvent, and the coating width is applied wider than the undercoat layer. .