JP4988197B2 - Coating film - Google Patents

Description

  The present invention relates to a coated film, and more particularly to a coated film that is excellent in transparency and antistatic properties, has water resistance, and does not deteriorate antistatic performance.

  Polyester film has excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and transparency, so it can be used as a base film for magnetic recording media, film for platemaking, film for packaging, optical It is used for a wide range of applications, including film.

  However, a common problem with plastic films is that they are easily charged by static electricity. This causes problems such as poor running characteristics of the processed product or processed product, and attracting dust around the film.

  In general, as an antistatic method for a polyester film, a method of kneading a low molecular weight anionic surfactant type compound such as an organic sulfonate, a method of depositing a metal compound, an anionic compound or a cationic compound, or a so-called There is a method of applying a conductive compound to the surface.

  Although the method of kneading an anionic compound has the advantage that it can be manufactured at low cost, it has a limit in the antistatic effect. In addition, since low molecular weight compounds are used, anionic compounds gather on the surface of the polyester film by so-called blooming, the adhesive force between the polyester film and the overcoat layer is reduced, or the anionic compounds are transferred to the film or transport roll. Problem arises. This also reduces the antistatic performance.

  The method of vapor-depositing a metal compound has excellent antistatic properties, and in recent years the application has been expanded as a transparent conductive film, but the production cost is high and suitable for specific applications, but as a general antistatic film Is difficult to use.

  A method of applying a high molecular weight cationic compound or anionic compound or a film as an antistatic agent has been adopted as an excellent method with few defects as described above. In particular, a method of performing coating (in-line coating) in the film manufacturing process is widely performed from the aspect of economy and characteristics. A typical example is a method in which coating is performed after longitudinal stretching but before lateral stretching, and then transverse stretching and heat setting are performed.

  However, many of these compounds often have high intermolecular cohesive force, so that, for example, in the step of stretching after coating as described above, the coating layer cannot follow the stretching and causes fine cracks on the surface, As a result, problems such as cloudiness of the coating layer due to light scattering and a decrease in durability of the coating layer often occur.

  In order to improve this problem, for example, a method of introducing polyglycerin as a component of the coating layer is disclosed (Patent Document 1). However, in this method, although the transparency of the coating layer can be obtained, the water resistance is poor, and there is a problem that the antistatic performance is easily lost by washing with water, for example.

JP-A-5-169593

  The present invention has been made in view of the above-mentioned circumstances, and its solution is an application with excellent transparency and antistatic property, water resistance, and antistatic performance hardly changing over time. To provide a film.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by providing a coating layer composed of a combination of specific types of compounds, thereby completing the present invention. It came.

  That is, the gist of the present invention is that a coating liquid containing an antistatic agent and a polyalkylene oxide adduct of glycerin or a polyalkylene oxide adduct of polyglycerin is applied to one side of a polyester film and stretched at least in a uniaxial direction. It exists in the coating film characterized by being formed.

Hereinafter, the present invention will be described in detail.
The base film of the coated film of the present invention is preferably a thermoplastic polymer, particularly polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method. For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid or the like may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles during the polyester production process can be used.

  The particle size and content of the particles used are selected according to the use and purpose of the film, but the average particle size is usually in the range of 0.01 to 5.0 μm. If the average particle size exceeds 5.0 μm, the surface roughness of the film may become too rough, or the particles may easily fall off from the film surface. When the average particle size is less than 0.01 μm, the surface roughness is too small and sufficient slipperiness may not be obtained. About particle | grain content, it is 0.0003 to 1.0 weight% normally with respect to polyester, Preferably it is the range of 0.0005 to 0.5 weight%. When the particle content is less than 0.0003 wt%, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 1.0 wt%, the transparency of the film is insufficient. There are cases.

  In addition, various stabilizers, lubricants, antistatic agents, and the like can be appropriately added to the film of the present invention.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable.

  The polyester film in the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both surface layers can be made of different polyesters depending on the purpose.

  Although the polyester film of the present invention has a coating layer, the coating layer is naturally included in the present invention regardless of whether the coating layer is provided only on one side or both sides of the film.

  Examples of the antistatic agent used in the present invention include various compounds. Particularly, a polymer compound having a cationic group or an anionic group is preferable from the viewpoint of antistatic properties and durability. Examples of the cationic group in the antistatic agent include a quaternary ammonium salt, and examples of the anionic group include a sulfonic acid group, a sulfate ester group, a carboxyl group, and a phosphate. In this case, each of the cationic group and the anionic group is not necessarily one kind, and both may be present in one molecule. As such a polymer compound, other components may be copolymerized.

  The number average molecular weight of the polymer compound is usually 1000 or more, preferably 2000 or more, more preferably 5000 or more. When the molecular weight is lower than this range, it may be easily removed from the coating layer to cause deterioration in performance over time, or the coating layer may become sticky. Moreover, when the molecular weight is low, the heat stability may be inferior.

  On the other hand, when such a compound has a molecular weight that is too high, the viscosity of the coating solution may become too high, resulting in problems such as deterioration of coating properties. In order not to cause such a problem, the number average molecular weight is preferably 500,000 or less, more preferably 100,000 or less.

  Moreover, the coating liquid for providing the coating layer in the present invention contains a polyalkylene oxide adduct of glycerin or a polyalkylene oxide adduct of polyglycerin.

  The polyalkylene oxide adduct of glycerin or polyglycerin is obtained by addition polymerization of polyalkylene oxide or a derivative thereof to the hydroxyl group of glycerin or polyglycerin represented by the following general formula (1).

上記式（１）中のｎが１の化合物がグリセリンであり、ｎが２以上の化合物がポリグリセリンである。本発明においては、式中のｎは、１〜２０の範囲が好ましい。

In the above formula (1), the compound in which n is 1 is glycerol, and the compound in which n is 2 or more is polyglycerol. In the present invention, n in the formula is preferably in the range of 1-20.

  Moreover, the structure of the polyalkylene oxide added or its derivative may differ for every hydroxyl group of glycerol or polyglycerol skeleton. Further, it is sufficient that it is added to at least one hydroxyl group in the molecule, and polyalkylene oxide or a derivative thereof need not be added to all hydroxyl groups.

  Preferable polyalkylene oxide or a derivative thereof is a structure containing a polyethylene oxide or polypropylene oxide skeleton. When the alkyl chain in the alkylene oxide structure becomes too long, the hydrophobicity becomes strong and the compatibility with the antistatic agent tends to deteriorate. Particularly preferred is polyethylene oxide.

  In the polyalkylene oxide adduct of glycerin or polyglycerin, the ratio of the glycerin or polyglycerin skeleton to the polyalkylene oxide or a derivative thereof is preferably in the range of 1/5 to 40/1 in terms of molecular weight. If the ratio of the glycerin or polyglycerin skeleton is smaller than this range, the compatibility with the antistatic agent tends to deteriorate, and if larger than this range, the water resistance of the coating layer tends to decrease.

  In the present invention, the ratio between the antistatic agent in the coating solution and the polyalkylene oxide adduct of glycerin or polyglycerin is preferably in the range of 50/1 to 1/2 in terms of solid content weight ratio. If the ratio of the antistatic agent is smaller than this range, the antistatic performance of the coating layer may be insufficient, and if it is larger than this range, the transparency of the coating layer may be inferior.

  The ratio of the antistatic agent in the total solid content of the coating solution is preferably in the range of 5% to 90%, more preferably in the range of 10% to 80%, and still more preferably in the range of 20% to 70%. % Range. If the ratio of the antistatic agent is smaller than this range, the antistatic performance of the coating layer tends to be insufficient, and if it is larger than this range, the transparency of the coating layer and the durability of the coating layer may be inferior. is there.

  The coating solution used in the present invention may contain a crosslinking reactive compound as necessary. Crosslinking reactive compounds mainly improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the coating layer by crosslinking reactions with functional groups contained in other resins and compounds, or by self-crosslinking. be able to. As the crosslinking reactive compound that can be used, amino resins such as melamine, benzoguanamine, and urea, oxazoline, epoxy, and glyoxal are preferably used. Also included are polymer-type cross-linking reactive compounds having reactive groups in other polymer skeletons.

  If necessary, one or more water-soluble or water-dispersible binder resins can be used in combination. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, and the like. In these, each skeleton structure may have a composite structure substantially by copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, and vinyl resin graft polyurethane. By containing these resins, the strength of the resulting coating layer and the adhesion to the base film can be improved.

  Coating liquids used in the present invention are surfactants, antifoaming agents, coating property improving agents, thickeners, organic lubricants, organic particles, inorganic particles, antioxidants, ultraviolet absorbers, foaming agents, dyes, You may contain additives, such as a pigment. These additives may be used alone or in combination of two or more as necessary.

  The coating liquid in the present invention is preferably an aqueous solution or a water dispersion from the viewpoint of handling, working environment, and stability of the coating liquid composition, but water is the main medium. An organic solvent may be contained as long as it does not exceed the range.

  The coating layer according to the present invention is provided by applying a coating solution containing a specific compound to a film, and in particular, in the present invention, the coating layer is provided by in-line coating in which coating is performed during film formation.

  In-line coating is a method of coating within the process of manufacturing a polyester film. Specifically, it is a method of coating at any stage from melt extrusion of polyester to biaxial stretching and then heat setting and winding. is there. Normally, it is coated on either a substantially amorphous unstretched sheet obtained by melting and quenching, then a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. Among these, a method in which a uniaxially stretched film is coated, dried in a tenter and stretched in the transverse direction, and further heat treated together with the base film is excellent. According to such a method, since film formation and coating layer coating can be performed simultaneously, there is a merit in manufacturing cost, thin film coating is easy to perform stretching after coating, and heat treatment applied after coating is other than that. Since the high temperature is not achieved by this method, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. In particular, when the coating layer contains a cross-linking reactive compound, there is an advantage that the reaction residue hardly remains due to the high-temperature heat treatment of in-line coating. The presence of a reactive residue in the coating layer causes a reaction with the components of the overcoat layer when blocking when the film is wound into a roll or when another layer is provided on the coating layer in a later step. This is not preferable.

  As a method for applying the coating solution to the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

The coating amount of the coating layer, when viewed as a final coating, typically 0.003~1.5g / ^{m 2,} preferably from 0.005 to 0.5 / ^{m 2,} more preferably 0.01 to 0 .3 g / m ² . When the coating amount is less than 0.003 g / m ^2, sufficient performance may not be obtained, and a coating layer exceeding 1.5 g / m ² is not preferable because it deteriorates the appearance and increases the cost.

  Other coating layers and treatments may be provided on the opposite side of the coating layer of the film of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the coating film which was excellent in transparency and antistatic property, and was able to provide water resistance with antistatic performance can be provided, The industrial utility value is high.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method and the processing method of a sample in an Example and a comparative example are as follows.

(1) Transparency According to JIS-K7136, the haze of the film was measured with an integrating sphere turbidimeter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd., and the increase in haze relative to the film without the coating layer was determined. It can be said that the transparency of a coating layer is excellent, so that the raise of the haze by providing a coating layer with respect to the film which does not provide a coating layer is small. Transparency was determined according to the following criteria.
○: Haze increase is less than 0.2% ×: Haze increase is 0.2% or more

(2) Antistatic property Using a high resistance measuring instrument: HP4339B and measuring electrode: HP16008B manufactured by Hewlett-Packard Japan, the sample was conditioned for 30 minutes in a measurement atmosphere of 23 ° C. and 50% RH, then 1 at an applied voltage of 100V. The surface specific resistance value of the coating layer after a minute was measured. The measured value was evaluated according to the following criteria.
○: Good, surface specific resistance value is 1 × 10 ¹¹ Ω or less ×: Defect, surface specific resistance value is higher than 1 × 10 ¹¹ Ω

(3) Water resistance of antistatic performance After immersing the sample film in warm water at 40 ° C for 24 hours, remove the adhering water by lightly pinching with a qualitative filter paper ("No2" made by TOYO Advantech), and after drying overnight at room temperature The surface resistivity was measured by the method shown in (2) above, and compared with the value before immersion in hot water, and evaluated according to the following criteria.
○: Good, worse than the value before immersion in warm water within 3 digits (within 1000 times)
X: Poor and deterioration from the value before immersion in warm water is 3 digits or more (over 1000 times)

The polyester raw materials used in Examples and Comparative Examples are as follows.
(Polyester 1)
Polyethylene terephthalate chip having no intrinsic viscosity and having an intrinsic viscosity of 0.66 (polyester 2)
Polyethylene terephthalate chip having an intrinsic viscosity of 0.66 and containing 0.2 parts by weight of amorphous silica having an average particle size of 2.5 μm

Moreover, the following was used as a coating composition.
(A-1): Poly (diallyldimethylammonium chloride), number average molecular weight of about 30,000
(B-1): Polyethylene oxide adduct to diglycerin skeleton. Average molecular weight 450
(B-2): Polyglycerin having an average degree of polymerization of 10 (C-1): Crosslinkable resin of alkylolmelamine / urea copolymer (Beckamine manufactured by Dainippon Ink and Chemicals, Inc.)
(D-1): Acrylic resin having a Tg of about 40 ° C. copolymerized with alkyl acrylate and alkyl methacrylate (Nicarbazole manufactured by Nippon Carbide Industries).

・ Production example of polyester film Polyester 1 and polyester 2 are blended at a weight ratio of 92/8, sufficiently dried, heated and melted at 280 to 300 ° C, extruded into a sheet form from a T-shaped die, and electrostatic adhesion. The film was cooled and solidified in close contact with a mirror-cooling drum having a surface temperature of 40 to 50 ° C. using a method to prepare an unstretched polyethylene terephthalate film. This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. This uniaxially oriented film was guided to a tenter stretching machine, stretched 4.0 times in the width direction at 100 ° C., and further heat treated at 230 ° C. to obtain a biaxially oriented polyethylene terephthalate film having a film thickness of 38 μm. When the transparency of this polyester film was measured, the haze was 0.8%. Further, when the antistatic property was measured, the surface resistivity was as high as 1 × 10 ¹⁵ Ω, and the antistatic property was inferior.

Example 1:
In the process as shown in the production example of the polyester film, a coating composition as shown below was applied to one side of the uniaxially oriented film after stretching in the longitudinal direction. Next, the film was guided to a tenter stretching machine, and the coating composition was dried using the heat. Thereafter, the same process as in the polyester film production example was performed, and 0.04 g / mm on the base film having a film thickness of 38 μm. A laminated biaxially oriented polyethylene terephthalate film in which a coating layer having an amount of m ² was laminated was obtained.
-Coating liquid composition: 40 parts of (A-1), 5 parts of (B-1), 20 parts of (C-1), and 40 parts of (D-1). However, “part” represents a weight ratio in the resin solid content.

Comparative Examples 1-2:
In the same manner as in Example 1, except that the composition of the coating solution was changed to the following, a coating layer having an amount of 0.04 g / m ² was laminated on a base film having a film thickness of 38 μm. An axially oriented polyethylene terephthalate film was obtained.
・ Coating solution composition of Comparative Example 1: 40 parts of (A-1), 20 parts of (C-1), 40 parts of (D-1) Represents weight ratio, and so on)
-Coating solution composition of Comparative Example 2: 40 parts of (A-1), 5 parts of (B-2), 20 parts of (C-1), 40 parts of (D-1) or more The evaluation characteristics are shown in the following table.

  The film of the present invention can be suitably used in a wide range of applications including a magnetic recording medium base film, plate-making film, packaging film, and optical film.

Claims (1)

A coating liquid containing an antistatic agent and a polyalkylene oxide adduct of glycerin or a polyalkylene oxide adduct of polyglycerin is applied to one side of a polyester film and stretched at least in a uniaxial direction. Application film.