JPH0449572B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a surface-coated polyester film having an easily adhesive interface. For more details,
A polyester that has an easily adhesive interface that allows the primer to be scattered and fixed on the surface in a granular state, and to provide adhesion over a wide range not only between the base material and the granular primer but also between the coating layer of the topcoat material. Regarding film. Polyesters synthesized from aromatic dibasic acids or their ester-forming derivatives and diols or their ester-forming derivatives, such as polyethylene terephthalate or copolymers thereof, polyalkylene naphthalates, and also this polymer and small proportions of other resins. It is well known to melt-extrude a blended product with the above to form a film. This biaxially stretched polyester film has better heat resistance, gas barrier properties, electrical properties, and chemical resistance than films made of other resins. However, since the surface is highly crystal oriented, the surface has high cohesiveness and poor receptivity to paints, adhesives, and inks. Therefore, when a synthetic resin layer is provided on the surface of a polyester film, in order to strengthen the adhesion between the two, the surface of the substrate is subjected to corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, or flame treatment to activate the surface. Additionally, a method of coating with a synthetic resin coating film has been applied. However, although these methods of activating the substrate surface can be expected to improve adhesion to the coating material layer by increasing secondary bonding force due to wetting, the activation period decreases with time, and surface treatment The adhesion force obtained by this method is not necessarily satisfactory and cannot be a sufficient means. Etching methods in which the surface is swollen or partially dissolved with various agents have been proposed as another method for increasing the receptivity of the polyester film surface.
This process involves immersing the surface in an aqueous acid, alkali, or amine solution, trichloroacetic acid, or phenols, and etching the surface to relax the crystal orientation near the surface, reduce cohesiveness, and increase the adhesion of the binder resin. This method is based on the principle of achieving the desired effect, and is the most reliable in terms of its effectiveness, and the adhesion between the base material and the synthetic resin coating layer provided thereon is strong. However, some of the chemicals used in this method are harmful and may be dangerous to handle, and extreme care must be taken to prevent the release of chemical gas into the atmosphere and causing environmental pollution. There are disadvantageous problems. In addition, when coating and impregnating these, not only does the equipment and machinery become rusty and corrode, but the processing solution remains in the base film after processing, and over time it leaches out and has an adverse effect on the upper coating layer. Sometimes. Therefore, this type of technology is gradually disappearing. As a further development of this method, there is a method in which a primer layer (undercoat layer) is previously provided on a base material, a thin surface layer that is different from the base material is formed, and then a desired synthetic resin is coated. When forming the undercoat layer, the coating process is generally performed in a process separate from the film forming process, so there is a risk that dust such as dirt and debris may be mixed in during the process. For this reason, it is necessary to maintain the delicate quality of highly processed film products such as audio magnetic tape, video magnetic tape, computer magnetic tape, X-ray photographic film, photographic film for printing, and diazo microfilm. Even if an easily adhesive interface is successfully formed, the base film cannot be used in applications where surface defects are caused by dust. In particular, when finishing the base film into the desired processed product,
In the middle, in order to transform the surface into one that is highly workable,
Providing a step of primer coating lacks rationality and cannot be said to be advantageous from an economical or industrial technical point of view. Therefore, if the process of applying the undercoat is carried out in an atmosphere that is as dust-free as possible, that is, in the sequence of polyester film production, it will be possible to fully support the use of the above-mentioned advanced film-processed foods. Become. Therefore, it is desirable to perform subbing treatment in an in-line process, but in the conventional technology, the formation of an easily adhesive interface by primer coating on the surface of a polyester film is almost impossible by coating the surface layer with a composition dissolved in an organic solvent. This has been achieved through engineering. Therefore, if this method is attempted to be carried out during the film forming process, the surrounding organic solvent gas will volatilize, creating an environment that is unfavorable from a safety and hygiene perspective, and the main equipment involved in film forming must be made explosion-proof. There are other annoyances. Therefore, although it is theoretically possible to incorporate subbing processing in-line into the production process, it actually causes a number of obstacles, and in reality it has to be carried out off-line. Moreover, the surface modification effect of primer coating has a wide range of effects, with conventionally known primers showing remarkable effects on certain topcoat compositions but not on others. It is difficult to say that there is a material that has surface receptivity that is fully satisfactory over the entire range. In addition, applying a primer coating, even if its amount is minimal, results in the formation of a flat thin film on the surface layer, which significantly impairs the handling of the base and makes it less slippery.
Wrinkles are more likely to occur. This tendency is particularly pronounced for bases such as magnetic tape bases whose surfaces are made as flat as possible to improve electromagnetic properties, and not only is it extremely difficult to wind up and unwind after applying a primer, but if left untreated. This exhibits an adhesive blocking phenomenon and is extremely difficult to avoid unless the base surface is extremely roughened. An exception to this is when the primer coating is performed in a continuous process prior to the final desired coating, such as a magnetic coating or a photographic emulsion coating, in which case this type of blocking and handling problem can be avoided; Disadvantages that are unilaterally imposed only on site measurements that carry out continuous coating, such as the effort to improve or modify equipment that allows continuous coating, the effort of keeping two continuous processes in good condition at the same time, and the trouble when one of the processes is in poor condition. Considering losses due to reduced yield, etc., even if it seems efficient, the economic burden is actually extremely large. For example, center line average roughness (Ra)
For the reasons mentioned above, it is difficult to use a polyester film that is a flat base for magnetic tape (less than 0.015μ) and has a thickness of 25μ or less unless a primer coat is applied before applying the magnetic paint. However, it is extremely difficult to provide the primer coat as an easily adhesive film with a primer coat to the user, either in the form of an independent, separate product, or in the hands of the film material supplier. In general, transportability when using film rolls, their handling, ease of handling,
Blocking properties are largely affected by the slippery properties of film contact surfaces and the frictional behavior at each contact point in the transport roll system during film formation, and in order to keep this low, it is important to It is known in principle to reduce the adhesive shearing force of the material, to maintain the Young's modulus of the polymer material at a high level during pressure bonding, or to form minute protrusions on the surface to reduce the contact surface area. However, when a primer that is compatible with a polyester film is formed, most of the thin film exhibits flat characteristics, so unless the base becomes too rough and contributes to reducing the contact area, the friction coefficient will decrease for the reasons mentioned above. It's difficult to measure. In other words, in order to reduce the coefficient of friction and ensure ease of handling, it can be said that an effective measure is to reduce the adhesive shearing force at the surface layer interface or to reduce the surface contact area. In order to reduce the adhesive shearing force, it is possible to add organic lubricants and oils to the primer, which are also effective in preventing blocking. In addition, in order to make the contact area relatively small, small particles such as CaCO ₃ ,
It is preferable to add MgO TiO ₂ , ZnO, etc. so that a small amount of air is likely to exist between the contact layers. However, even if the adhesive shear force and contact area are reduced in this way, and ultimately ease of handling is achieved, the adhesion between the primer layer and the substrate base, which is important, may be significantly weakened in the future. However, problems remain such that the original primer effect is not sufficiently expressed, and it is almost impossible to achieve an appropriate balance between the two for the reasons described above. In view of this, the inventor of the present invention aims to provide a supplier with an easily adhesive film that is less likely to cause blocking, has excellent transportability and easy handling, and is coated with a primer, particularly a polyester film that is particularly suitable for magnetic tapes. As a result of intensive studies aimed at It has been found that the present object can be completely achieved by a film in which the projected area is maintained at a ratio of 1% or more to the total surface area, and the present invention has been achieved based on this finding. Aspects of the present invention will be successively explained below. The composition selected in the present invention is a mixture consisting of one or more water-dispersed polymer liquids and a surfactant,
It is preferable that the film forming temperature of the polymer is rather high, and as a standard, 40° C. or higher is desirable. On the other hand, the specific conditions for applying the composition require a series of steps such as applying the composition to the polyester before completing crystal orientation, and then completing biaxial stretching and oriented crystallization. The temperature conditions are lateral stretching temperature of 75℃~
It is necessary for the coated original fabric to undergo a heating history of 120°C and a crystallization temperature of 180°C to 245°C. With the combination of these conditions, the primer layer can be scattered and fixed to the film surface extremely uniformly in the form of particles. As described above, the greatest aim of the present invention is not to simply form the primer layer on the substrate as a flat film, but to form the primer itself into particles under special conditions and fix the primer itself in order to exhibit easy adhesion. That is, this method is completely different from the conventional method in which, for example, an inorganic filler is added to the coated primer layer and the friction coefficient is reduced by reducing the contact surface area by the protrusions. Examples of primers that can be used include water-dispersed acrylic resins, vinylidene chloride vinyl chloride copolymers, acrylic styrene resins, epoxy resins, and polyurethane resins. A polyurethane dispersion with a high dispersion is preferred. If the coating formation temperature drops significantly below 40°C, the resin may melt due to the high temperatures encountered during film formation, potentially resulting in a flat film. Furthermore, if the Young's modulus of the resin film itself is too low, even if it is possible to form a granular primer layer, the result will be unfavorable in terms of slipperiness and blocking. In this sense, it is preferable that the resin film has a microhardness meter (Shorr A) of 40° or more in order to fully implement the present invention. The polyurethane may be aromatic polyurethane or aliphatic polyurethane as long as it satisfies the above conditions, and its types include polyester type, polyether type, or ionic (anion type) or cation type to enable water dispersion. It can be either. Samples available include
UX-3500 (Sanyo Chemical Industries), Softex U
-100, UE-296A (Kao Soap), Pascoal V-217 (Meisei Chemical Industry), Rezamin W-1020
(Dainichiseika), Impranyl DLN (Bayer), Impranyl DLH (Bayer), Hydran HW-140 (Dainippon Ink), Igelak S-4040 (Hodogaya Chemical), etc. can be cited as examples. The various resins to be used as primers as described above may be used alone or in a mixture of two or more without any problem, as long as the purpose of the present invention is not significantly impaired. There is also no problem in adding a small proportion of a surfactant to the primer of the present invention in order to maintain a better painted surface appearance or to improve the wetting properties of the primer surface. Further, in order to improve the performance of the coating film properties of the primer, for example, a crosslinking agent or a crosslinking accelerator may be generally added as long as the above-mentioned purpose is not hindered. As mentioned above, the granular primer of the present invention differs from the conventional concept of covering the entire surface of the base film with a thin film, but in terms of effectiveness, it covers more than 1% of the total area (projected area ratio). If it is occupied by a granular primer, sufficient effects can be obtained. If it is less than 1%, the effect is not completely absent, but it is rather insufficient and deviates from the purpose of the present invention. In order to explain the present invention in more detail, the present invention will be described below with reference to examples, but these are merely illustrative and not limiting. Note that the measurement items in the examples were measured by the following methods. 1. Adhesion After the primer coating process, the polyester film was coated with various top coats under the specified conditions, and Scotch Tape No. 600 (manufactured by 3M) width 19.4 m/m and length 8 cm was applied to avoid air bubbles. , above this JISC2701 ('75)
This sample was peeled off in a T-shape over a 5 cm distance between the bonded laminated parts using the manual load roll described above using Tensilon manufactured by Toyo Seiki Co., Ltd. at a head speed of 300 mm/min.
The peel strength at this time is determined and divided by the tape width to determine g/cm. In the T-peel, the laminate was placed with the tape side facing down and the distance between the tension chucks was 5 cm. 2 Surface slipperiness Temperature 20 for primer-coated and non-coated surfaces
The static friction coefficient was measured at ℃ and humidity of 60% RH using a Slippery measurement tester manufactured by Toyo Tester Co., Ltd. 3 Blocking resistance Two films (5 cm x 5 cm) are pasted together on the coated surfaces, and a silicone rubber measuring 6 x 6 cm with a thickness of 2 m/m is then applied with the same dimensions and a thickness of 3 m/m.
Sandwich a glass plate from both sides and apply a load of 2 kg to it in an atmosphere of 40℃ x 75%RH.
After being left for 24 hours, the film surfaces were peeled off from each other, and those that could be peeled off without any problems were marked with ○, those with surface defects caused entirely by adhesive on either side were marked with ×, and those with slight defects were marked with △. 4 Center flatness roughness (Ra) Using a stylus type surface roughness meter (Sarfcom8B) manufactured by Tokyo Seimitsu Co., Ltd., with a needle radius of 2μ and a load of 0.19g, the film standard length is 26m/m, and the standard length direction is multiplied by 50. Magnify 20,000 times in the surface roughness direction and find the roughness curve. Cut out a part with a measurement length L (reference length 2 mm) in the direction of the center line, set the center line of this cut out part as the X axis, and the direction of vertical magnification as the Y axis, and draw a roughness curve as Y=f(x). When expressed, the value given by the following formula is expressed in units of μ. RCLA=1/L∫ ^L _O |f(x)|dx In this measurement, the standard length is 0.25 mm, 8 measurements are taken, 3 are excluded from the direction with the largest value, and the average value of the 5 is expressed. 5 Granular primer occupancy The entire field of view that can be observed from a photograph at an appropriate magnification with a differential interference microscope or scanning electron microscope is Vf,
When the area of the uncoated portion in which no particulate matter is formed is Vn, the particulate primer occupancy is expressed by the following formula. Vf-Vn/Vf×100 Example 1 Using orthochlorophenol as a solvent, 0.125wt% of calcium carbonate with an intrinsic viscosity of 0.62 measured at 35°C and a particle size of 0.5μ, and 0.15wt of titanium oxide with a particle size of 0.3μ
% containing polyethylene terephthalate at 160℃
Dry at 284℃, melt-extrude and cool solidify on a casting drum kept at 50.4℃ to 160μ
An unstretched film was obtained. Then 3.6 in the longitudinal direction
Immediately after the uniaxially stretched film is stretched, the total solid content is
A 2wt% aqueous dispersion coating solution was coated on one side using the usual roll coating method. The solid content of the coating liquid consists of the following types, and all numbers indicate weight ratios. Polyvinylidene chloride resin (product name: Saran
EX2380/Asahi Kasei) 30 Polyepoxy compound (product name: EX314/Nagase Sangyo) 30 Polyethyleneimine (product name: P-1000/Nippon Shokubai) 30 Surfactant (product name: NS206/NOF) 10 After 90~ Roughly dried in a preheating zone at 95°C, then horizontally stretched to 3.51 times, and then heated at 210°C.
Heat fixation was performed for 7.7 seconds. In the end, a 15μ base film was obtained, but the coating amount was 0.03g/m ²
It was (Dry). The photographs confirmed the presence of scattered particulate matter. A summary of the properties of the obtained film is shown in Table 1 below, which shows that the basic properties are no different from those of an uncoated film that is not treated at all under the same conditions, and that it exhibits good adhesion properties. I understand.

[Preparation of paint for evaluation]

Nitrocellulose for paint thinner
RS1/2 [Flakes containing 25% isopropanol, manufactured by Daicel Corporation] was dissolved to prepare a 40wt% solution, and 43.8 parts of the solution was added, followed by 32.5 parts of polyester resin (Desmofene 1700 manufactured by Bayer AG) and chromium diacid powder. 200gr, 1 part, 0.5 part of soybean oil fatty acid (Resion P manufactured by Riken Vitamin Co., Ltd.), a cationic activator (Cation AB manufactured by Nippon Oil & Fats Co., Ltd.) and squalene (shark liver oil) as a dispersant/wetting agent. Add 0.8 parts to a ball mill. 282 parts of a mixed solvent consisting of methyl ethyl ketone (hereinafter abbreviated as MEK)/cyclohexanone/toluene-3/4/3 (weight ratio) is further mixed and sufficiently pulverized to prepare a mother liquor paint (45 wt%). This mother liquor
To 50 parts, add 48 parts of an addition reaction product of trimethylolpropane and toluylene diisocyanate (Coronatere: manufactured by Nippon Polyurethane Industries, Ltd.) to butyl acetate.
6.25 parts were added to prepare a final magnetic paint for evaluation with a concentration of 42.75wt%. Example 2 Under the same film forming conditions as in Example 1, in-line coating was performed by replacing the coating liquid composition with the following. The solid fraction ratio is as follows: N-β (aminoethyl) γ-aminopropyltrimethoxysilane (SH6020: Toray Silicon): 30 N-methylacrylamide (Soken Chemical): 30 N-methylolacrylamide (Torezin F30 Teikoku) Chemical): 30 Diphenylmethane-P-diethylene urea (Sogo Yakuko): 20 Surfactant (NS208 Nippon Oil & Fats): 10 The total solid concentration was 2 wt% aqueous dispersion. The final film has 0.035g/m ² (Dry)
was applied, and the photograph confirmed that the particulate matter was evenly distributed. This is shown in Figure 1. It was found that the polyester film on which this type of granular primer was formed was completely equivalent in handling and had significantly improved adhesion properties compared to the uncoated polyester film obtained under the same conditions. This is shown in Table-2. The primer occupancy rate was 5.3%, and Ra was
It was 0.020.

[Table] The adhesion () was evaluated using the same method as described in Example 1, and the adhesion () was evaluated using cellophane printing ink (CL-S709) whose main binder is a nitrocells resin binder and a rosin resin. White) stock solution 1 was diluted with a mixed solvent 2 ratio of MEK/toluene/ethyl acetate/=1/1/1 to prepare a paint for evaluation. Dainippon Ink (trade name) Coating thickness was determined using a gravure coater, applying 2.1 μm under the same conditions, and determining the peel strength using a prescribed method. Comparative Example 1 Water-soluble copolymerized polyester (Pesresin 4000: Solid content ratio (weight) of methylolized melasin resin (Sumitex Resin M3 Sumitomo Chemical) and surfactant (NS208 Nippon Oil & Fats) for hardening it (Takamatsu Oil and Fat)
However, in-line coating was performed under the same film forming conditions as in Example 1, except that a 2 wt% aqueous solution having a ratio of 80:10:10 was used to form a primer on the surface. As a result, although it was possible to wind the film, the slipperiness of the film itself was greatly reduced, some wrinkles appeared at the edges, and the film could not be completely rolled. The primer effect of this film was found to be sufficient compared to that of an uncoated film, but as a result of examining the surface using differential interference microscopy, it was clear that the primer was formed as a flat thin film, which caused problems with slippage. It became. The slipperiness (static friction coefficient) of coated/uncoated surfaces is 1.0.
It was confirmed that the resulting film was extremely difficult to handle and could not be used practically. Comparative Example 2 In Example 1, the crystallization heat treatment temperature after lateral stretching was lowered to 164°C, the treatment time was increased from 7.7 seconds to 8.8 seconds, and in-line coating was performed with the same coating liquid composition, but no Although the primer was partially granular, its shape was distorted in some places, and there were areas that were exactly the same as the base material and areas that looked like dust and agglomeration, and the slipperiness was 0.57 in terms of static friction coefficient. I found out that it has been rising.
However, regarding the primer effect, the adhesion () was at exactly the same level as in Example 1 and there were no problems, but the uneven shape of the primer layer caused concerns from a quality standpoint and it could not be used. It is something. Examples 3, 4, 5 Polyethylene terephthalate having an intrinsic viscosity of 0.63 measured at 35°C using orthochlorophenol as a solvent and containing 0.25wt% titanium oxide with a particle size of 0.3μ was dried at 167°C and melt-extruded at 287°C. It was rapidly solidified on a casting drum held at 47.8°C to obtain an unstretched film with a thickness of 152μ, which was then heated to 93°C.
Stretched at 3.6 times in the longitudinal direction on a heated metal roll, then sequentially in-line coated with coating liquids No. 3, No. 4, and No. 5 using a conventional method, and then in a preheating zone. After approximately drying, the temperature is
Stretching was performed 3.5 times at 104°C. After heat fixing at 231° C. for 7.4 seconds, the material was wound around a core to prepare four types of samples including a non-coated sample. Table 3 summarizes the characteristics of the obtained film.

[Table] The corresponding uncoated films of Examples 3, 4, and 5 had adhesion properties of 10.7, which were formed as granules.
g/cm, it showed an extremely low value, and it was found that the primer was sufficiently effective in promoting adhesion.

[Brief explanation of the drawing]

FIG. 1 is a 900x differential interference microscope photograph showing an aspect of Example 3, showing that particulate matter is scattered on the surface.

Claims (1)

[Claims] 1 Particulate primer is scattered and adhered to the surface of the polyester film, and its proportion to the total surface area is 1% or more in terms of projected area, and the surface roughness in this state is more than 0.05μ in terms of center line average roughness (Ra). An easily adhesive polyester film coated with a primer.