CN1305941C - Applied film - Google Patents

Abstract

An applied film comprising a polyester film and, formed on one surface thereof, an applied layer, characterized in that the surface of the applied layer exhibits a surface resistivity of 1 X 1013[ohm] or less, and has an polyester oligomer after the heat treatment at 180ringC for 30 min in an amount eight times that before the heat treatment or less. The applied film has excellent anti-static characteristics, is free from the attachment of dust or the like, and is reduced in optical defects.

Description

coating film

technical field

The present invention relates to a coating film having good antistatic performance, capable of preventing adhesion of dust and the like, and having few optical defects.

Background technique

Because of its excellent mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, transparency and other characteristics, biaxially oriented polyester film is widely used in the base film of magnetic recording media, plate making Applications such as films, packaging films, and optical films.

However, the common problem of plastic films is that they are easily charged due to static electricity, which causes problems such as poor running characteristics during film processing or processed products, and adsorption of surrounding dust.

The commonly used antistatic methods for polyester films are: the method of mixing low molecular weight anionic surfactant compounds such as organic sulfonates; the method of vapor deposition of metal compounds; coating anionic compounds, cationic compounds, or so-called conductive compounds on the surface method etc.

Although the method of kneading with an anionic compound has the advantage of being inexpensively manufactured, it has a limitation in the antistatic effect. And due to the use of low-molecular-weight compounds, anionic compounds will accumulate on the surface of the polyester film due to blooming, reducing the adhesion between the polyester film and the surface coating, or causing the anionic compound to attach to the film and the conveying roller instead. problem etc. This also reduces the durability of the antistatic properties.

The method of evaporating a metal compound has good antistatic properties, and its application has been extended to transparent conductive films in recent years. However, it is difficult to use as an ordinary antistatic film because of its high manufacturing cost and for special purposes.

However, although the method of coating conductive compounds such as conductive carbon has the advantages of good antistatic effect and low cost of manufacture, it has the disadvantage of poor transparency of the film.

Therefore, polyester film antistatic widely adopts the method of coating high molecular weight anionic compound and/or high molecular weight cationic compound on the film to be used as antistatic agent.

In the production method of the biaxially oriented polyester film with a coating, the method of applying a coating during the film production process is widely used, especially in consideration of economical efficiency and characteristics. A typical example is a method in which coating is applied after longitudinal stretching and before transverse stretching, followed by transverse stretching and heat setting.

Especially in recent years, with the diversification of the use of polyester film, the processing and use conditions of the film also tend to be diversified. For example, when the polyester film is placed at a high temperature of 100 ° C and above, the low Polymers can form precipitates on the surface of the membrane, thus creating various problems when processing or using the membrane under such conditions.

In the prior art, adopt the method that utilizes solid-phase polymerization to seek to reduce the oligomer contained in the raw material, or utilize terminal blocking agent to improve the hydrolysis resistance of polyester film etc. to prevent oligomer from precipitating, but the problem is, in more Strict conditions cannot be met to prevent oligomer precipitation and the production cost becomes too high, etc.

On the other hand, although various coatings have been proposed for the purpose of surface modification of polyester films as described above, there is still a problem that the deposition of oligomers is promoted due to the coating composition.

The present invention was made in view of the above circumstances, and the problem to be solved is to provide a polyester film having excellent antistatic performance, resistance to dust accumulation, etc., and few optical defects.

Contents of the invention

As a result of intensive studies on the above-mentioned problems, the inventors of the present invention found a solution to the above-mentioned problems by providing a coating layer having a specific structure, and completed the present invention.

That is, the object of the present invention is to provide a coating film, which is a polyester film with a coating on one side, characterized in that the surface resistivity of the coating surface is below 1×10 ¹³ Ω, and the film is tested at 180° C. The amount of polyester oligomers on the coating surface after heat treatment for 30 minutes is 8 times or less than the amount of polyester oligomers before the heat treatment.

The present invention is described in detail below

The polyester constituting the polyester film of the present invention is a polyester obtained by polycondensation of a dibasic acid component and a diol. The above-mentioned dibasic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedioic acid, adipic acid, sebacic acid, 4,4'-diphthalic acid, 1 , 4-cyclohexanedioic acid, etc.; and ethylene glycol components can include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, trimethylene glycol, tetramethylene diol alcohol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc.

More representative among the polyesters used in the present invention are polyethylene terephthalate, polyethylene-2,6-naphthalate, polyethylene terephthalate-1,4-ring Hexamethylene dimethyl ester and the like may be used. In addition, polyesters obtained by copolymerizing the above-mentioned acid components and diol components may be used, and other components and additives may be added as necessary.

For the convenience of handling, the polyester film of the present invention can also be added with particles that can give it easy slippage. Particles used for this purpose include silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, alumina, titanium oxide, corundum, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, etc. Inorganic particles; organic particles such as cross-linked polymer particles and calcium oxalate; and particles precipitated during the manufacture of polyester, etc.

The particle size and content of the particles used can be selected according to the use and purpose of the film, and the average particle size ranges generally from 0.005 to 5.0 μm, preferably from 0.01 to 3.0 μm. When the average particle diameter exceeds 5.0 μ, the surface of the film becomes too rough so that the particles tend to come off from the surface of the film. Whereas when the average particle diameter is less than 0.005 μm, the surface roughness is too small and sufficient slippage cannot be obtained. The particle content is based on polyester, usually 0.001 to 30.0% by weight, preferably 0.01 to 10.0% by weight. If the amount of particles is too large, the mechanical properties and transparency of the film will be damaged; if too little, the slippage will be too large. Difference.

In addition to the above particles, additives may be added as required. Examples of such additives include antistatic agents, stabilizers, lubricants, crosslinking agents, antiblocking agents, antioxidants, dyes, pigments, sunscreen agents, and ultraviolet absorbers.

As long as the conditions of the present invention are satisfied, the polyester film of the present invention may have a multilayer structure, and in the case of a multilayer structure, may contain a non-polyester layer. Of course, the coating concept of the present invention includes both single-side coating film and double-side coating film, at least one-side coating film, as long as the conditions of the present invention can be met.

The polyester film of the present invention is characterized in that the surface resistivity of the coating surface is 1×10 ¹³ Ω or less, preferably 1×10 ¹² Ω or less, more preferably 1×10 ¹⁰ Ω or less. When the surface resistivity exceeds 1×10 ¹³ Ω, there will be problems such as film blocking when winding the film into a roll and sequentially conveying stacked individual films, poor processability, and adhesion of debris and dust.

The polyester film of the present invention is preferably such that the amount of polyester oligomers on the coating surface after the film is heat-treated at 180° C. for 30 minutes is 8 times or less than the amount of polyester oligomers before the treatment. The amount of polyester oligomers on the coating surface after heat treatment at ℃ for 30 minutes is 3.0 mg/m ² or less.

When the amount of polyester oligomer on the coating surface after heat treatment exceeds the above range, the use of the polyester film will be limited. For example, it is known that there is a problem of removing the polyester film and releasing the mold after it is used as an adhesive layer provided on a polyester film provided with a mold release layer and pasted on other parts. When releasing the molded film of the first layer, oligomers precipitated from the film will crystallize in the adhesive layer, forming optical defects such as bright spots. In addition, in the case of a transparent film, the appearance is impaired due to increased turbidity; when a surface coating is used, the adhesion with the surface coating is reduced; or processing equipment is polluted, and productivity is reduced.

In order to solve the above-mentioned various problems, the present invention provides a coating layer exhibiting the performance of lowering the surface resistivity and preventing the precipitation of oligomers on the polyester film. In the present invention, a compound having a quaternary ammonium group and polyvinyl alcohol are preferably used as components constituting the coating layer provided on the surface of the film.

Compounds with quaternary ammonium groups refer to compounds with structural elements containing quaternary ammonium groups on the main chain and side chains in the molecule. Examples of such structural elements include pyrrolidinium rings, tetrasubstituted alkylamines, and copolymers thereof with acrylic acid or methacrylic acid, tetrasubstituted N-alkylaminoacrylamides, vinylbenzyl trimethyl Amine salt, 2-hydroxy-3-methacryloylpropyltrimethylamine salt, etc. And it can also be used in combination or copolymerized with other resins. Examples of the anion forming the counter ion of these quaternary ammonium salts include ions such as halide ion, alkylsulfate, alkylsulfonate, and nitrate. In the present invention, it is preferable that the compound having a quaternary ammonium group is a polymer compound. When the molecular weight is too low, there will be problems such as easy removal from the coating, resulting in gradual performance degradation or coating stickiness over time. In addition, when the molecular weight is low, the heat resistance stability may also be lowered. In order to avoid this problem, the number average molecular weight of the compound having a quaternary ammonium group is usually preferably 1,000 or more, more preferably 2,000 or more, and particularly preferably 5,000 or more. But on the other hand, when the molecular weight of the compound is too high, problems such as too high viscosity of the coating solution may occur. To avoid such problems, the number average molecular weight is preferably 500,000 or more.

The polyvinyl alcohol used in the present invention can be synthesized by a common polymerization reaction, and is preferably soluble in water.

The degree of polymerization of polyvinyl alcohol is not particularly limited, and polyvinyl alcohol having a degree of polymerization of 100 or more, preferably 300 to 40,000, is generally used. When the degree of polymerization is less than 100, there is a possibility of lowering the water resistance of the coating. The degree of saponification of polyvinyl alcohol is not particularly limited, and saponified polyvinyl acetate with a degree of saponification of 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is usually used in actual use.

One kind or two or more kinds of binder resins other than those mentioned above which are soluble or dispersible in water can also be used in the coating as needed. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin and the like. Their skeleton structure may also be a composite structure formed by copolymerization or the like. Examples of adhesive resins having a composite structure include acrylic resin grafted polyester, acrylic resin grafted polyurethane, vinyl resin grafted polyester, vinyl resin, etc. Resin grafted polyurethane, etc.

Crosslinking reactive compounds can also be added as desired. The crosslinking reactive compound is preferably capable of improving cohesiveness, surface hardness, scratch resistance, solvent resistance and water resistance of the coating layer through a crosslinking reaction with functional groups mainly contained in coating constituents.

The coating of the film of the present invention can also add surfactants, defoamers, applicability improvers, thickeners, antistatic agents, organic lubricants, organic particles, inorganic particles, antioxidants, ultraviolet absorbers, hair dyes, etc. Foaming agents, dyes, pigments and other additives. These additives may be used alone or in combination of two or more kinds as necessary.

The proportion of the compound having a quaternary ammonium group in the coating constituents is usually 10 to 99% by weight, preferably 20 to 95% by weight. When the ratio is too much higher or lower than the above range, desired antistatic performance and oligomer precipitation preventing performance cannot be obtained.

The coating solution used in the present invention is preferably an aqueous solution or a water dispersion in consideration of operability and operating environment. It uses water as the main medium, but as long as it does not exceed the scope of the present invention, it may also contain organic solvents. .

The concentration of the solid content in the coating liquid is not particularly limited, but is usually 0.3 to 65% by weight, preferably 0.5 to 30% by weight, and more preferably 1 to 20% by weight. Concentrations too much above or below this range make it difficult to apply a coating of the thickness necessary to adequately function.

In terms of thickness after drying, the coating thickness is usually 0.003-1.5 μm, preferably 0.005-0.5 μm, more preferably 0.01-0.3 μm. When the coating thickness is less than 0.003 μm, there is a possibility that sufficient performance cannot be achieved, and when it is greater than 1.5 μm, blocking between films is likely to occur.

The method of applying a coating layer on a polyester film is preferably a method of applying a coating liquid in the process of producing a polyester film. For example, the method of stretching after coating a coating liquid on an unstretched film, the method of coating a coating liquid on a uniaxially stretched film and then stretching, coating a coating liquid on a biaxially stretched film Afterwards, the method of stretching, etc. In particular, a method of simultaneously drying and stretching in a tenter after coating a coating liquid on an unstretched or uniaxially stretched film is employed in view of economic efficiency.

As a method of coating a coating liquid on a polyester film, for example, the coating technique described in "Coating Method" (written by Yuji Harasaki, published in 1979) can be used. Specifically, air knife coater, knife coater, rod coater, knife coater, extrusion coater, dip coater, reverse roll coater, transfer roll Coating machine, gravure coating machine, roller kiss coating machine, coating casting machine, spray coating machine, curtain coating machine, glue calendering machine, extrusion coating machine, bar coating machine and other technologies.

Detailed ways

The present invention will be further described in detail by citing examples below. As long as it does not exceed the scope of the gist of the present invention, the present invention is not limited by the following examples. In addition, evaluation methods, sample processing methods, and the like in Examples and Comparative Examples are as follows.

(1) Surface resistivity value

Use the Japanese Hewlett-Packard high impedance measuring instrument (HP4339B) and the measuring electrode (HP16008B), fully adjust the humidity of the sample under the measuring environment of 23 ℃ and 50% RH, then apply a voltage of 100V, and measure the surface of the coating after 1 minute resistivity.

(2) Heat treatment method of the film:

Laminate A4 size KENT paper with heat treated polyester film. At this time, the surface for measuring the amount of oligomers is placed outside, and the four corners are fixed with screws or the like so that the KENT paper and the polyester film are not moved. The above-mentioned polyester film was put into a furnace at 180° C. under a nitrogen atmosphere for 30 minutes, and heat-treated.

(3) Measurement method of the amount of oligomers on the surface of the film

The polyester film is folded into a square box with an open top and a bottom area of 250 cm ² . When setting the coating, place the coated side on the inside.

Then put into the DMF (dimethylformamide) of 10ml in the box that is made by above-mentioned method, after standing 3 minutes, reclaim DMF, the DMF that reclaims adds liquid chromatograph (Shimadzu LC-7A), obtains The amount of polyester oligomers in DMF was obtained, and the amount of oligomers was divided by the area of the membrane in contact with DMF to obtain the amount of oligomers on the surface of the membrane (mg/m ² ).

(4) Evaluation of the amount of oligomers on the surface of the film 1

A non-heat-treated film and a film heat-treated at 180° C. for 30 minutes by the method shown in (2) above were prepared. Then, according to the method described in (3) above, the amount of oligomers on the two film surfaces was measured respectively, and the value after the heat treatment was divided by the value before the heat treatment to obtain the ratio.

(5) Evaluation of the amount of oligomers on the surface of the film 2

According to the method of (2) above, the film was heat-treated at 180° C. for 30 minutes. Then, according to the method of (3) above, the amount of oligomers on the surface of the film was measured.

(6) Evaluation of dust accumulation (ash content measurement)

Fully adjust the humidity of the polyester film under the measurement environment of 23°C and 50% RH, then wipe the coating layer 10 times repeatedly with a cotton cloth, place it near the fine plant ash, and evaluate the dust accumulating property according to the following criteria.

◯: The film does not accumulate dust even in contact with dust.

△: A small amount of dust accumulated on the film in contact with the dust.

×: When the film is close to the dust, there will be a lot of dust accumulation.

(7) Optical defect inspection

The release layer shown in the following (R-1) is provided on the surface of the polyester film (the surface provided with the coating layer in the following examples and comparative examples), and the coating amount is 0.1g/m ² (after drying) , to obtain a release film. Then, an acrylic adhesive was applied on the release layer and dried at 180° C. for 5 minutes to obtain an adhesive layer with a thickness of 20 μm. Bond it to a glass plate, remove the release film, and obtain a sample of the adhesive layer, place it on the stage of a polarizing microscope, set two polarizers to clamp the sample, form Nicol polarization, and observe abnormalities such as bright spots Optical defects. Only the optical defects of 0.5 μm or more are counted, and the number is converted into the number of units per unit area of the adhesive layer, and then evaluated according to the following criteria.

○: Optical defects are less than 0.5 pieces/m ² (no problem in practical use)

△: Optical defects are more than 0.5 pieces/m ² and less than 1.0 pieces/m ² (slightly problematic in practical use)

X: Optical defects are 1.0 pieces/m ² or more (problems in practical use).

Composition of release layer (R-1)

Mix the curable silicone resin/curing catalyst/solvent at a weight ratio of 10/5/2000, and the solvent is toluene/MEK mixed solvent at a weight ratio of 1/1.

Comparative example 1

After fully drying the polyethylene terephthalate sheet with an intrinsic viscosity of 0.65, heat and melt it at 280-300°C, extrude it with a T-die, make it into a sheet, and use an electrostatic bonding method to connect it to the surface temperature. It is cooled and solidified by close contact with a mirror cooling drum at 40-50°C to make an unstretched polyethylene terephthalate film. This film was stretched 3.7 times in the longitudinal direction while passing through a set of heated rolls at 85° C. to obtain a uniaxially oriented film. Stretch the above uniaxially oriented film 4.0 times in the width direction with a tenter at 100°C, then heat-treat at 230°C to obtain a biaxially oriented polyethylene terephthalate oriented film with a film thickness of 50 μm .

Example 1

In the film forming process, the film is coated and dried. Specifically, in the film forming process using the same operation sequence as in Comparative Example 1, one side of the uniaxially oriented film after longitudinal stretching and before transverse stretching On, apply the coating liquid shown in (A) below. It is then dried using thermal energy in a tenter. Thereafter, in the same manner as Comparative Example 1, a laminated biaxially oriented polyethylene terephthalate oriented film having a coating layer of 0.05 g/m ² on a 50 μm thick base film was obtained.

Coating solution (A)

A polymer SHALLOL DC-303P having a pyrrolidinium ring in the main chain produced by Daiichi Kogyo Pharmaceutical Co., Ltd./polyvinyl alcohol with a degree of saponification=88 mol% and a degree of polymerization=500/silica gel with an average particle diameter of 0.05 μm was used to The weight composition ratio in terms of solid content was set at a ratio of 85/10/5 to prepare an aqueous coating liquid.

Embodiment 2-4

Example 2, Example 3 and Example 4 are the same except that the contents of the coating solution in Example 1 are replaced by the following (B), (C) and (D), and the result is obtained on a base film with a thickness of 50 μm. A laminated biaxially oriented polyethylene terephthalate oriented film provided with a coating layer in an amount of 0.05 g/m ² .

Coating solution (B)

Polymer SHALLOL DC-303P having a pyrrolidinium ring in the main chain produced by Daiichi Kogyo Pharmaceutical Co., Ltd./Polyvinyl alcohol with a degree of saponification=88 mol% and a degree of polymerization=500/Methoxyl produced by Dainippon Ink Chemical Industry Co., Ltd. Methylmelamine BECAMINE/silica gel with an average particle diameter of 0.05 μm was formulated as an aqueous coating liquid at a weight composition ratio of 40/20/35/5 in terms of solid content.

Coating solution (C)

Poly(trimethylaminoethyl methacrylate) tetrasubstituted product/saponification degree=88 mol% polyvinyl alcohol/polymerization degree=500/Methoxymethylolmelamine BECAMINE manufactured by Dainippon Ink Chemical Industry/average particle diameter 0.05 Silica gel of μm was prepared as an aqueous coating liquid at a weight composition ratio of 40/20/35/5 in terms of solid content.

Coating solution (D)

The compound (D-1) was obtained by copolymerizing trimethylaminoethyl methacrylate tetrasubstitute/methyl methacrylate at a weight composition ratio of 65/35 according to a conventional method. Using this compound D-1, D-1/polyvinyl alcohol with a degree of polymerization=500/saponification degree=88 mol%/methoxymethylol melamine BECAMINE manufactured by Dainippon Ink Chemical Industry/average particle diameter of 0.05 μm Silica gel was prepared as an aqueous coating liquid at a weight composition ratio of 70/10/15/5 in terms of solid content.

Comparative example 2~3

Comparative Example 2 and Comparative Example 3 are the same except that the content of the coating solution in Example 1 is replaced by the following (E), (F), and the base film with a thickness of 50 μm is provided with a quantity of 0.05 g/m ² . Coated laminated biaxially oriented polyethylene terephthalate oriented film.

Coating solution (E)

Polyvinyl alcohol with a degree of saponification = 88 mol % and a degree of polymerization = 500 / methoxymethylol melamine BECAMINE manufactured by Dainippon Ink Chemical Industry / silica gel with an average particle diameter of 0.05 μm, the weight composition ratio in terms of solid content The ratio of 85/10/5 was calculated to make a water-based coating liquid.

Coating solution (F)

Acrylic resin NIKASOL with a Tg of about 40°C obtained by copolymerizing polytrimethylaminoethyl methacrylate tetrasubstituent/alkyl acrylate and alkyl methacrylate manufactured by Nippon CARBIDE Industries/methacrylic resin manufactured by Dainippon Ink Chemical Industry Co., Ltd. Oxymethylolmelamine BECAMINE/silica gel with an average particle diameter of 0.05 μm was used to prepare an aqueous coating solution at a weight composition ratio of 40/20/35/5 in terms of solid content.

The film characteristics and usability obtained as above are shown in Table 1 and Table 2.

Table 1 Evaluation of dust accumulation Optical Defect Inspection Example 1 ○ ○ Example 2 ○ ○ Example 3 ○ ○ Example 4 ○ ○ Comparative example 1 x x Comparative example 2 x △ Comparative example 3 △ x

Table 2 Surface resistivity (Ω) Oligomer amount evaluation 1 Oligomer amount evaluation 2 (mg/m ² ) Example 1 2×10 ⁹ 1.2 0.6 Example 2 1×10 ¹⁰ 1.4 0.7 Example 3 3×10 ¹¹ 1.2 0.6 Example 4 2×10 ¹¹ 2.4 1.2 Comparative example 1 5×10 ¹⁴ twenty one 10.5 Comparative example 2 5×10 ¹⁴ 8.2 4.1 Comparative example 3 4×10 ¹¹ 22.4 11.2

Industrial applicability

According to the present invention, it is possible to provide a coating film that prevents contamination due to static electricity, does not cause problems due to oligomer precipitation even after use at high temperatures, and has few optical defects, and its industrial application value is high.

Claims (7)

1. film for one kind, it is the cated polyester film for release film of single face, it is characterized in that,

(a) surface resistivity of described coatingsurface is 1 * 10 ¹³Below the Ω,

(b) described polyester film is being below 8 times of polyester oligomer amount before heat-treating through the polyester oligomer amount of the described coatingsurface after the thermal treatment in 30 minutes under 180 ℃,

(c) described coating contains the compound with quaternary ammonium group, and this compound is the macromolecular compound that has the textural element that contains quaternary ammonium group on the macromolecular compound of the tetramethyleneimine  ring that has seasonization on the main chain or the side chain in molecule.

2. as claimed in claim 1 filming is characterized in that, described polyester film in the polyester oligomer amount of the coatingsurface after thermal treatment in 30 minutes under 180 ℃ at 3.0mg/m ²Below.

3. as claimed in claim 1 or 2 filming is characterized in that coating contains the compound with quaternary ammonium group.

4. as claimed in claim 3 filming is characterized in that, the compound with quaternary ammonium group is a macromolecular compound.

5. as claimed in claim 1 or 2 filming is characterized in that coating contains polyvinyl alcohol.

6. as claimed in claim 1 or 2 filming is characterized in that, coating is that water-based is applied after liquid is coated on the film, and the drying and the back that stretches form.

7. as claimed in claim 3 filming is characterized in that, having the ratio that the compound of quaternary ammonium group occupies in the coating constituent is the scope of 10～99 weight %.