JP2003237005A - Coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film which has excellent antistatic performance and small optical defect and which prevents a dust from being adhered. <P>SOLUTION: The polyester film comprises a coating layer on one side surface so that a surface specific resistance on the surface of the layer is 1×10<SP>13</SP>Ω/square or less, and an amount of a polyester oligomer on the surface of the coating layer after the film is heat treated at 180° for 30 min is eight times or less as large as that of the polyester oligomer before the heat treatment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating film having good antistatic performance, preventing adhesion of dust and the like, and having few optical defects.

[0002]

2. Description of the Related Art Biaxially stretched polyester films have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and transparency, and are therefore used as base films for magnetic recording media and plate making. It is used in a wide range of applications, including film for film, packaging film, and optical film.

However, a problem common to all plastic films is that they are prone to static electricity and are easily charged, which causes problems such as poor runnability of the film or processed product, and attraction of dust around it.
In general, as an antistatic method for a polyester film, a method of kneading a compound that is a low molecular weight anionic surfactant type such as an organic sulfonate, a method of depositing a metal compound, an anionic compound or a cationic compound,
Alternatively, there is a method of applying a so-called conductive compound on the surface. The method of kneading an anionic compound has an advantage that it can be manufactured at low cost, but has a limit in the antistatic effect. Furthermore, since a low molecular weight compound is used, the anionic compound collects on the surface of the polyester film by so-called blooming, the adhesion between the polyester film and the overcoat layer is reduced, and the anionic compound is transferred to the film or the transport roll. Problem arises. Therefore, the durability of antistatic performance is also reduced.

The method of vapor-depositing a metal compound has excellent antistatic properties, and although its application as a transparent conductive film has been expanding in recent years, it is high in manufacturing cost and suitable for a specific application. It is difficult to use as a prevention film. The method of applying a conductive compound such as conductive carbon has an advantage that the antistatic effect is relatively good and can be produced at a relatively low cost, but has a drawback that the transparency of the film is deteriorated. For this reason, a method of coating a film with a high molecular weight anionic compound or a high molecular weight cationic compound as an antistatic agent has been widely adopted as an antistatic method for polyester films.

As a method for producing a biaxially stretched polyester film having a coating layer, in particular, a method of performing coating in the film production process is widely used from the viewpoint of economy and its characteristics. A typical example is a method in which coating is performed after longitudinal stretching and before lateral stretching, and then lateral stretching and heat setting are performed. Also,
Particularly, in recent years, as the use of polyester film has been diversified, the processing and use conditions of the film have also diversified. For example, if the polyester film is left at a high temperature of 100 ° C. or higher, oligomers leached from the inside will be deposited on the film surface. , Process the film under these conditions,
Alternatively, various problems have occurred due to its use.

Conventionally, as a method for preventing the precipitation of oligomers, solid-phase polymerization is used to reduce the amount of oligomers contained in the raw material, and an end-capping agent is used to improve the hydrolysis resistance of the polyester film. However, under more severe conditions, there are problems that the prevention of oligomer precipitation is not satisfied and the manufacturing cost becomes too high. Also,
As described above, various coating films have been proposed for the purpose of modifying the surface of the polyester film, but depending on the composition to be coated, the problem of accelerating the precipitation of oligomers occurs.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the problem to be solved is to have an excellent antistatic property, prevent adhesion of dust and the like, and prevent optical defects. It is to provide less polyester film.

[0008]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by providing a coating layer having a specific structure, and completed the present invention. Came to do.

That is, the gist of the present invention is a polyester film having a coating layer on one side, and the surface resistivity of the coating layer surface is 1 × 10 ¹³ Ω / □ or less, and the film is 180 ° C. for 30 minutes. The coated film is characterized in that the amount of the polyester oligomer on the surface of the coating layer after the heat treatment is 8 times or less the amount of the polyester oligomer before the heat treatment.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyester constituting the polyester film of the present invention is a polyester obtained by polycondensation of a dicarboxylic acid component and a glycol component. These dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4'-diphenyldicarboxylic acid, 1,4
-Cyclohexyldicarboxylic acid and the like, as the glycol component, ethylene glycol, diethylene glycol,
Triethylene glycol, propylene glycol, butanediol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol and the like can be mentioned.

Typical examples of the polyester used in the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate and the like. The polyester may be a copolymer of a glycol component and a glycol component, and may contain other components and additives as necessary. The polyester film of the present invention may contain particles for the purpose of imparting slipperiness, for easy handling. The particles used for such a purpose include, for example, silica, calcium carbonate, magnesium carbonate, calcium phosphate,
Kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, inorganic particles such as molybdenum sulfide, crosslinked polymer particles, organic particles such as calcium oxalate, and the polyester production process Precipitated particles or the like can be used.

The particle size and content of the particles used are selected according to the application and purpose of the film.
Usually 0.005 to 5.0 μm, preferably 0.01 to
It is in the range of 3.0 μm. If the average particle size exceeds 5.0 μm, the surface roughness of the film may become too coarse, or the particles may easily fall off the film surface. If the average particle size is less than 0.005 μm, the surface roughness may be too small and sufficient slipperiness may not be obtained. The particle content is usually 0.00 based on polyester.
1 to 30.0% by weight, preferably 0.01 to 1
It is 0.0% by weight. When the amount of particles is large, the mechanical properties and transparency of the film tend to be impaired, and when the amount is small, the slipperiness tends to be poor.

If desired, additives may be added in addition to the above particles. Examples of such additives include an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an antioxidant, a dye, a pigment, a light blocking agent, and an ultraviolet absorber. The polyester film in the present invention may have a multi-layer structure as long as the requirements of the present invention are satisfied, and in the case of the multi-layer structure, a layer other than polyester may be included. Further, the coating layer is provided only on one side of the film, whether provided on both sides, it is naturally included in the concept of the present invention, as long as at least one coating layer satisfies the requirements of the present invention Good.

The polyester film of the present invention is a coated film characterized by having a surface specific resistance of 1 × 10 ¹³ Ω / □ or less on the surface of the coating layer, preferably 1 × 10 ¹² Ω / □. □ or less, more preferably 1
× 10 ¹⁰ Ω / □ or less. Surface resistivity is 1 × 10
If it exceeds ¹³ Ω / □, when the film wound into a roll is unwound, or when the stacked single-sheet films are sequentially conveyed, adhesion between the films or defective processing,
It causes problems such as adhesion of foreign matter and dust.

Further, in the polyester film of the present invention, the amount of the polyester oligomer on the surface of the coating layer after the film was heat-treated at 180 ° C. for 30 minutes was 8 times or less the value before the treatment, and the film was 180 ℃
It is preferable that the amount of polyester oligomer on the surface of the coating layer is 3.0 mg / m ² or less after heat treatment for 10 minutes. If the amount of polyester oligomer on the surface of the coating layer after heat treatment exceeds these ranges, the use of the polyester film may be limited. For example, when an adhesive layer is provided on a polyester film provided with a release layer and the product is used as a release film for removing the polyester film and the release layer after bonding to another member, the oligomer precipitated from the film adheres. It is known that there is a problem that crystallization occurs in the layer and causes optical defects such as bright spots. In addition, in the case of a transparent film, it may hurt the appearance due to haze-up, or when using with an overcoat layer, the adhesion with the overcoat layer may be reduced, or the processing equipment may be soiled and productivity may be reduced. Have problems.

In order to solve various problems as described above,
In the present invention, the polyester film is provided with a coating layer exhibiting the surface resistivity and the ability to seal the precipitation of oligomers. In the present invention, a compound having a quaternary ammonium salt group or polyvinyl alcohol is preferably used as a component constituting the coating layer provided on the film.

The compound having a quaternary ammonium salt group refers to a compound having a constituent element containing a quaternary ammonium salt group in the main chain or side chain in the molecule. Examples of such constituent elements include a pyrrolidinium ring, a quaternary compound of an alkylamine, a copolymer of these with acrylic acid or methacrylic acid, a quaternary compound of N-alkylaminoacrylamide, a vinylbenzyltrimethylammonium salt, and -Hydroxy 3-methacryloxypropyl trimethyl ammonium salt etc. can be mentioned. Furthermore, these may be combined or copolymerized with other resins. Examples of the anion serving as the counter ion of these quaternary ammonium salts include ions such as halogen, alkyl sulfate, alkyl sulfonate and nitric acid.

Further, in the present invention, the compound having a quaternary ammonium salt group is preferably a polymer compound. If the molecular weight is too low, it may be easily removed from the coating layer to cause deterioration of performance over time, or the coating layer may become sticky. Further, when the molecular weight is low, the heat stability may be poor. In order to prevent such a problem, the compound having a quaternary ammonium salt group has a number average molecular weight of usually 1,000 or more, more preferably 200 or more.
It is preferably 0 or more, and particularly preferably 5000 or more. On the other hand, if the molecular weight of such a compound is too high, problems such as excessively high viscosity of the coating liquid may occur. In order to prevent such a problem, the number average molecular weight is preferably 500000 or less.

The polyvinyl alcohol used in the present invention is
It can be synthesized by an ordinary polymerization reaction and is preferably water-soluble. The polymerization degree of polyvinyl alcohol is not particularly limited, but is usually 100 or more,
It is preferably 300 to 40,000. When the degree of polymerization is 100 or less, the water resistance of the coating layer tends to decrease. The degree of saponification of polyvinyl alcohol is not particularly limited, but saponified polyvinyl acetate having a saponification degree of usually 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is practically used. Furthermore, in the coating layer, one or more water-soluble or water-dispersible binder resins other than the above may be used in combination, if necessary. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, and amide resin. Each of these skeleton structures may have a substantially composite structure 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, vinyl resin graft polyurethane and the like.

Further, a cross-linking reactive compound may be contained if necessary. The crosslinking-reactive compound can improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the coating layer mainly by crosslinking reaction with the functional groups contained in the coating layer constituent components. preferable. The coating layer of the film of the present invention comprises a surfactant, a defoaming agent, a coating property improving agent, a thickener, an antistatic agent, an organic lubricant, organic particles, inorganic particles, an antioxidant, an ultraviolet absorber, and a foaming agent. It may contain additives such as agents, dyes and pigments. These additives may be used alone or in combination of two or more if necessary.

The proportion of the compound having a quaternary ammonium salt group in the constituents of the coating layer is usually 10 to 99% by weight, preferably 20 to 95% by weight. If the ratio is higher or lower than these ranges, the desired antistatic performance and oligomer deposition prevention performance may not be obtained. The coating solution used in the present invention is preferably an aqueous solution or an aqueous dispersion in terms of handling, working environment, but it contains water as a main medium and contains an organic solvent within the range not exceeding the gist of the present invention. You may have. The solid content concentration of the coating solution is not particularly limited, but is usually 0.3 to 65% by weight, preferably 0.5 to 30% by weight,
More preferably, it is 1 to 20% by weight. When the concentration is either higher or lower than these ranges, it may be difficult to provide a coating layer having a thickness necessary for sufficiently exhibiting the function.

The thickness of the coating layer is a dry thickness, usually 0.00
3 to 1.5 μm, preferably 0.005 to 0.5 μm,
More preferably, it is 0.01 to 0.3 μm. If the thickness of the coating layer is less than 0.003 μm, sufficient performance may not be obtained, and if it exceeds 1.5 μm, blocking between films tends to occur. As a method of providing a coating layer on the polyester film, a method of applying a coating solution in the step of producing the polyester film is suitably adopted. For example, a method of stretching after coating on an unstretched film, a method of stretching after coating on a uniaxially stretched film,
There is a method of stretching after coating on a biaxially stretched film. In particular, it is economical to apply a coating solution to an unstretched or uniaxially stretched film, and then simultaneously perform drying and stretching in a tenter.

A method for applying a coating solution to a polyester film is described in, for example, Yuji Harazaki, Maki Shoten, 1979.
It is possible to use a coating technique as shown in "Coating method", published annually. 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 , Extrusion coaters, bar coaters and the like.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The evaluation methods and sample processing methods in Examples and Comparative Examples are as follows.

(1) Surface specific resistance value High resistance measuring device (HP
4339B) and a measurement electrode (HP16008B), the sample was sufficiently conditioned in a measurement atmosphere at 23 ° C. and 50% RH, and the surface resistivity of the coating layer was measured after 1 minute at an applied voltage of 100V.

(2) Heat treatment method of film A4 size Kent paper and polyester film to be heat treated are superposed. At that time, clip the four corners with a paper clip so that the surface for measuring the amount of oligomer is on the outside, and stop the Kent paper and the polyester film. In a nitrogen atmosphere, the polyester film is left in an oven at 180 ° C. for 30 minutes for heat treatment.

(3) Method for measuring the amount of oligomer on the film surface A square box is prepared by folding the polyester film so that the top is open and the area of the bottom is 250 cm ² . When a coating layer is provided, the surface of the coating layer should be on the inside. Then, in the box created by the above method,
DMF (dimethylformamide) (10 ml) was added and left for 3 minutes, and then DMF was recovered. The recovered DMF was supplied to liquid chromatography (Shimadzu LC-7A) to obtain the oligomer amount of polyester in DMF, and the value of this oligomer amount was divided by the film area in contact with DMF to obtain the film surface oligomer amount ( mg / m ² ).

(4) Evaluation of Film Surface Oligomer Amount 1 A film not heat-treated and a film heat-treated at 180 ° C. for 30 minutes by the method described in (2) above are prepared. Then, the amounts of both film surface oligomers are measured by the method described in (3) above, and the value after heat treatment is divided by the value before heat treatment to obtain the ratio.

(5) Evaluation of film surface oligomer amount 2 The film is heat-treated at 180 ° C. for 30 minutes by the method described in (2) above. Next, the amount of oligomer on the film surface is measured by the method described in (3) above.

(6) Evaluation of Dust Adhesion (Ash Test) After sufficiently controlling the humidity of the polyester film in a measurement atmosphere of 23 ° C. and 50% RH, the coated layer is rubbed 10 times with a cotton cloth. This was gently brought close to the finely crushed cigarette ash, and the ash adhesion state was evaluated according to the following criteria. ◯: Does not adhere even if the film is contacted with ash. Δ: When the film is brought into contact with ash, it adheres a little. X: A large amount is attached only by bringing the film close to ash.

(7) Optical Defect Inspection On the surface of the polyester film (the surface on which the coating layer is provided in the following Examples and Comparative Examples), the release layer shown in the following (R-1) is coated in an amount of 0.1 g. / M ² (after drying) to obtain a release film. Then, an acrylic pressure-sensitive adhesive was applied onto the release layer and dried at 180 ° C. for 5 minutes to form a pressure-sensitive adhesive layer having a thickness of 20 μm. The adhesive layer sample obtained by adhering this to a glass plate and removing the release film is placed on the stage of a polarizing microscope to sandwich the sample 2
Optical polarizers such as bright spots were observed by setting the polarizers in a crossed Nicol pattern. Optical defect size is 0.5
Only those having a size of μm or more were counted, the number was converted to the area of the adhesive layer, and then evaluated according to the following criteria. ◯: Optical defects are less than 0.5 / m ² (no problem in practical use) Δ: Optical defects are 0.5 / m ² or more, 1.0 / m ²
Less than (somewhat practically problematic) x: 1.0 or more optical defects / m ² (more practically problematic) Release layer (R-1) composition: curable silicone resin / curing catalyst / solvent In a weight ratio of 100/5/2000, but the solvent is a solvent in which toluene / MEK is mixed in a weight ratio of 1/1.

Comparative Example 1 A polyethylene terephthalate chip having an intrinsic viscosity of 0.65 was sufficiently dried, then heated and melted at 280 to 300 ° C., extruded in a sheet form from a T-shaped die, and electrostatically adhered to the surface. An unstretched polyethylene terephthalate film was prepared by allowing it to cool and solidify while being in close contact with a mirror surface cooling drum at a temperature of 40 to 50 ° C. This film was stretched 3.7 times in the longitudinal direction while passing through a group of heating rolls at 85 ° C. to obtain a uniaxially oriented film. This uniaxially oriented film was stretched 4.0 times in the width direction at 100 ° C. by a tenter stretching machine and further heat-treated at 230 ° C. to give a film thickness of 5
A 0 μm biaxially oriented polyethylene terephthalate film was obtained.

Example 1 During the film manufacturing process, the film was coated and dried. Specifically, in the film production process according to the same procedure as in Comparative Example 1, the coating solution as shown in (A) below was applied to one surface of the uniaxially oriented film after longitudinal stretching and before transverse stretching. Then, drying was performed by utilizing the heat in the tenter stretching machine. After that, the same procedure as in Comparative Example 1 was performed.
A laminated biaxially oriented polyethylene terephthalate film provided with a coating layer in an amount of m ² was obtained. Coating liquid (A) A polymer having a pyrrolidinium ring in the main chain, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Charol DC-303P / saponification degree = 88 mol%, polyvinyl alcohol having a polymerization degree = 500 / silica sol having an average particle diameter of 0.05 μm. Is an aqueous coating solution containing 85/10/5 in terms of solid composition weight composition ratio.

Examples 2 to 4 In Example 1, the content of the coating liquid is as follows (B),
The thickness is 5 in the same manner except that the thickness is changed to (C) and (D).
A laminated biaxially oriented polyethylene terephthalate film having a coating layer in an amount of 0.05 g / m ² on a 0 μm base film was obtained, which were referred to as Example 2, Example 3, and Example 4, respectively.

Coating liquid (B) is a polymer having a pyrrolidinium ring in the main chain, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Charol DC-303P / polyvinyl alcohol / methoxymethylol melamine having a saponification degree of 88 mol% and a polymerization degree of 500. An aqueous coating solution containing Beckamine / silica sol having an average particle size of 0.05 μm manufactured by Dainippon Ink and Chemicals, Inc. at a ratio of 40/20/35/5 by weight in terms of solid content.

Coating liquid (C) quaternary polytrimethylaminoethyl methacrylate /
Polyvinyl alcohol / methoxymethylol melamine having a saponification degree of 88 mol% and a polymerization degree of 500, which is a beckamine manufactured by Dainippon Ink and Chemicals Inc./a silica sol having an average particle diameter of 0.05 μm, is used in a solid composition equivalent weight composition ratio of 40/20. /
Aqueous coating liquid containing 35/5.

Coating solution (D) Trimethylaminoethyl methacrylate 4 by a conventional method
Graded product / methyl methacrylate as a weight composition ratio of 6
A compound (D-1) copolymerized at a ratio of 5/35 was obtained.
Using this compound D-1, D-1 / saponification degree = 88 mol%, polymerization degree = 500, polyvinyl alcohol / methoxymethylol melamine, Beckamine manufactured by Dainippon Ink and Chemicals / silica sol with an average particle size of 0.05 μm. Is an aqueous coating solution containing 70/10/15/5 in terms of solid composition weight ratio.

Comparative Examples 2 to 3 In Example 1, the contents of the coating liquid are the following (E) and (F).
A laminated biaxially oriented polyethylene terephthalate film in which a coating layer having an amount of 0.05 g / m ² was provided on a base film having a thickness of 50 μm was obtained in the same manner as in Comparative Example 2 and Comparative Example, respectively. Example 3 is set.

Coating solution (E) Beckamine manufactured by Dainippon Ink and Chemicals / silica sol having an average particle size of 0.05 μm, which is polyvinyl alcohol / methoxymethylolmelamine having a degree of saponification of 88 mol% and a degree of polymerization of 500, is solid content. 85/10 / in terms of weight composition ratio
An aqueous coating solution containing 5 parts.

Coating liquid (F) quaternary polytrimethylaminoethyl methacrylate /
Nikazole / Methoxymethylol melamine manufactured by Nippon Carbide Kogyo Co., Ltd., which is an acrylic resin having an acrylic acid alkyl ester and methacrylic acid alkyl ester copolymerized and a Tg of about 40 ° C., Becamine manufactured by Dainippon Ink and Chemicals / average particle size 0. An aqueous coating solution containing 05 μm of silica sol at a weight composition ratio of 40/20/35/5 in terms of solid content. The properties and practical properties of the film thus obtained are shown in Tables 1 and 2 below.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

Industrial Applicability According to the present invention, it is possible to provide a coating film which prevents stains due to static electricity and does not cause a problem due to the precipitation of oligomers even after use at high temperature, and has few optical defects. Its industrial utility value is high.

Continued front page    F-term (reference) 4F006 AA36 AB20 BA07 CA02 CA07                       DA04                 4F100 AH03B AK01B AK21 AK21B                       AK36 AK41A AK42 BA02                       CC00B EH46 EJ38 EJ42                       EJ86 GB15 GB41 JG03 JG04B                       JL06 YY00B

Claims (7)

[Claims] 1. A polyester film having a coating layer on one side, wherein the surface resistivity of the coating layer surface is 1 × 10.
It is less than ¹³ Ω / □ and the film is 30 at 180 ° C.
The coated film, wherein the amount of the polyester oligomer on the surface of the coating layer after the heat treatment for 1 minute is 8 times or less the amount of the polyester oligomer before the heat treatment. 2. The amount of polyester oligomer on the surface of the coating layer is 3. after heat treatment of the film at 180 ° C. for 30 minutes.
The coated film according to claim 1, wherein the coated film is 0 mg / m ² or less. 3. The coating layer contains a compound having a quaternary ammonium salt group.
The coated film described. 4. The coated film according to claim 3, wherein the compound having a quaternary ammonium salt group is a polymer compound. 5. The coated film according to any one of claims 1 to 4, wherein the coated layer contains polyvinyl alcohol. 6. The coated film according to claim 1, wherein the coating layer is formed by coating an aqueous coating liquid on the film, followed by drying and stretching. 7. The coating according to claim 3, wherein the proportion of the compound having a quaternary ammonium salt group in the constituents of the coating layer is in the range of 10 to 99% by weight. the film.