JPH10100354A - Surface treated plastic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide antistatic properties and printability by the single surface of a plastic film and to enable offset printing by providing a surface coating layer consisting of an antistatic agent, copolyester and a crosslinking agent on the plastic film to specify the contact angle with water thereof. SOLUTION: A surface treated plastic film is obtained by providing a surface coating layer containing an antistatic agent, a copolyester resin and/or a crosslinking agent containing a blocked isocyanate group on at least the single surface of a plastic film. The contact angle of the surface coating layer and water is set to 45 deg. or more. As a crosslinking agent containing a blocked isocyanate group, there is a heat reaction type water soluble urethane resin wherein a terminal isocyanate group is blocked by a hydrophilic group. The addition amt. of the antistatic agent to the copolyester resin and the crosslinking agent containing the blocked isocyanate group is pref. 1-20wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for various labels, delivery slips, recording paper for printers, etc., and has an adhesive property and an antistatic property for an oxidation polymerization type ink, a UV curing type ink, a back carbon ink and the like. And a surface-treated plastic film having excellent offset printability.

[0002]

BACKGROUND OF THE INVENTION Polyester films are used in a wide range of applications because of their high crystallinity, excellent transparency, gloss, mechanical properties and chemical resistance. However, since a general polyester film has a high degree of electrical insulation, static electricity is likely to be generated and accumulated, and has the drawback of causing various problems due to electrostatic damage. Such static electricity damages, for example, wraps around a roll when performing film formation, printing, adhesion, bag making, packaging, electrostatic recording, etc., causes an electric shock to the human body, etc. This causes a reduction in commercial value such as a decrease in printability. As a method for preventing such static electricity damage, generally, a method of preparing a film by kneading an antistatic agent into a resin (hereinafter, also referred to as a “kneading type antistatic treatment method”), an antistatic agent composition on the film surface And the like.

In general, when imparting antistatic properties to a film by a kneading-type antistatic treatment method, an antistatic effect is exhibited by oozing out of the antistatic agent from the inside of the film to the surface. However, since the polyester resin has a high secondary transition temperature, when an antistatic film is produced by using a kneading type antistatic treatment method, the antistatic agent inside the film does not exude on the film surface at a temperature near normal temperature. In addition, the obtained antistatic film has insufficient antistatic properties. Furthermore, that high temperature is required for antistatic film production, that the polyester resin is deteriorated during film production by adding an antistatic agent due to the high reactivity of the polar group of the polyester resin,
In addition, there is a problem that the physical properties are deteriorated by the antistatic agent. In particular, when the antistatic polyester film obtained by the kneading type antistatic treatment method is biaxially stretched, the antistatic agent on the film surface escapes and disappears in the stretching step, so that the obtained film shows no antistatic effect at all. Often not. Furthermore, as described above, most of the antistatic agents have a problem that the transparency of the film is extremely lowered by blending it into the polyester film, so that the practicality is poor.

When an antistatic property is imparted by applying an antistatic composition to the surface of a film, a low molecular weight antistatic agent or a high molecular weight antistatic agent is mixed with an aqueous resin which normally serves as a binder. An agent composition is prepared and applied to the film surface. However, although the antistatic property of the antistatic film manufactured by this method is good, when performing offset printing, it is difficult to apply the antistatic agent composition to the surface to be printed because the ink transfer property becomes worse. No, the antistatic agent composition must be applied to the side opposite to the printing side. For this reason, when performing offset printing, the surface that can be printed on one of the films,
In addition, there is a problem that it is necessary to form both surfaces of the surface having antistatic properties on the opposite surface.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a film capable of offset printing which satisfies both antistatic properties and printability on at least one side of a plastic film. .

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, by treating at least one side of a plastic film, the contact angle with water becomes 45 degrees or more. This led to the completion of the present invention.

That is, the present invention provides (1) a plastic film, and a surface coating layer comprising an antistatic agent and a copolymerized polyester resin formed on at least one surface of the film and / or a crosslinking agent containing a block type isocyanate group. Wherein the contact angle between the surface coating layer and water is 45 ° or more, (2) the surface-treated plastic film according to (1), wherein the antistatic agent is a cationic antistatic agent, 3) The surface-treated plastic film according to the above (2), wherein the cationic antistatic agent is an ethosulfate salt of a quaternary ammonium cation, and (4) the above-mentioned (1) to (3), wherein the plastic film is a polyester film. The surface-treated plastic film described in any one of (5) the polyester film The polyester resin contains at least one kind of thermoplastic resin that is incompatible with the polyester and the polyester, and has fine voids therein by being stretched in at least one axial direction. The apparent specific gravity of the surface-treated plastic film is zero. .
The surface-treated plastic film according to (4), which has a light transmittance of 8 to 1.3, and (6) a light transmittance of 30% or less and an in-plane birefringence of -0.02 or more and +0.04 or less. To a surface-treated plastic film according to any one of (1) to (5).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The surface-treated plastic film of the present invention comprises at least one surface of a plastic film,
A surface coating layer containing an antistatic agent and a copolymerized polyester resin and / or a cross-linking agent containing a blocked isocyanate group, wherein the contact angle between the surface coating layer and water is 45 ° or more. Has features. When the contact angle (θH ₂ O) between the surface coating layer and water is less than 45 degrees,
There is a tendency for ink transfer failure to occur during offset printing. The contact angle with water is preferably 45 from the viewpoint of printability.
Degrees or more, more preferably 50 degrees or more.

The contact angle of water was measured at 23 ° C. and 65% RH.
Using a contact angle meter (manufactured by Elmo Corporation), 15 points were measured for one sample under the atmosphere described above, and the calculation was performed with the average of 13 points excluding the upper and lower two points.

The surface-treated plastic film of the present invention having such a contact angle has a surface coating containing an antistatic agent and a copolymerized polyester resin and / or a crosslinking agent containing a block type isocyanate group on at least one surface of the plastic film. It is obtained by providing a layer.

The antistatic agent is not particularly limited as long as the contact angle between the surface coating layer and water is 45 degrees or more. For example, the functional groups are sorbitan type, ether type, ester type, sorbitol type, nonionic type such as glucose type,
Quaternary ammonium salt type, quaternary ammonium resin type,
Cationic such as imidazoline type, arcobel type and solomin A type, anionic type such as alkyl sulfate type, alkyl phosphate type, phosphate ester type and sulfate ester type, and amphoteric type such as betaine type, amino acid type and amino sulfate type Surfactant type or polymer type (manufactured by Shin-Nakamura Chemical Co., Ltd .: EL polymer). Preferred are cationic antistatic agents from the viewpoint of ink transferability. Among them, an ethosulfate salt of a quaternary ammonium cation is particularly preferred.

The copolymerized polyester resin is not particularly limited as long as it is water-soluble or water-dispersible and has a sulfonic acid group.

The crosslinking agent having a blocked isocyanate group is a heat-reactive water-soluble urethane resin in which terminal isocyanate groups are blocked with a hydrophilic group.

The ratio of the amount of the antistatic agent to the copolymerized polyester resin and the crosslinking agent containing a blocked isocyanate group is preferably 1 to 20% by weight,
More preferably, it is 5 to 10% by weight. If the proportion of the antistatic agent is less than 1% by weight, sufficient antistatic properties cannot be obtained, and if it exceeds 20% by weight, offset printability deteriorates. It tends to decrease stability.

The ratio of the amount of the antistatic agent to the copolymerized polyester resin or the crosslinking agent containing a block type isocyanate group is 1 to 1 with respect to the copolymerized polyester resin or the crosslinking agent containing a block type isocyanate group.
It is 40% by weight, preferably 10 to 20% by weight.

The plastic film used in the present invention is not particularly limited, and may be, for example, one of polyolefin, polyester, polyamide, polyimide, polycarbonate, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride and polyvinylidene fluoride. A polymer film using two or more kinds is exemplified. Among them, a polyester film is particularly preferable. The thickness of the plastic film is not particularly limited, but is preferably in the range of 1 to 5000 μm, more preferably 5 to 500 μm, from the viewpoint of securing general strength characteristics as synthetic paper.

The polyester preferably used as the plastic film material includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid or esters thereof, ethylene glycol, diethylene glycol, 1,4-butanediol, Polyester produced by polycondensation of glycols such as pentyl glycol. The polyester is obtained by a method of directly reacting an aromatic dicarboxylic acid and a glycol, a method of subjecting an alkyl ester of an aromatic dicarboxylic acid to a transesterification reaction with a glycol followed by polycondensation, or a method of polymerizing a diglycol ester of an aromatic dicarboxylic acid. It can be produced by a condensation method or the like.

Representative examples of the polyester include polyethylene terephthalate, polybutylene terephthalate and polyethylene-2,6-naphthalate. The polyester may be a homopolymer or a copolymer obtained by using two or more kinds of acid components and glycol components. In the present invention, a polyester in which the ethylene terephthalate unit, butylene terephthalate unit or ethylene-2,6-naphthalate unit is at least 70 mol%, preferably at least 80 mol%, more preferably at least 90 mol% of the entire polyester is used. Preferably, by selectively using these polyesters as a plastic film material, it is possible to obtain a surface-treated plastic film which is more excellent in dimensional stability and heat resistance.

Further, as the film material, a material in which one or more kinds of thermoplastic resins incompatible with the polyester are blended together with the above-mentioned polyester is used. By performing uniaxial stretching treatment, and preferably biaxially stretching in the vertical and horizontal directions, a large number of fine cavities are formed inside the film,
The apparent specific gravity of the surface-treated plastic film is 0.8 ~
Polyester films (films containing fine voids) that can be set to 1.3 are extremely suitable as plastic films used in the present invention.

Here, the thermoplastic resin incompatible with the polyester is compounded as a cavity developing agent in order to form fine cavities in the polyester film to enhance flexibility, lightness and drawing properties. It can be used without any particular limitation as long as it has incompatibility with the polyester. That is, since the thermoplastic resin is incompatible with the above-mentioned polyester, it is dispersed in the polyester in the form of fine particles, and peels off at the interface with the polyester at the time of stretching to become a cavity forming source.

As the thermoplastic resin, for example, a polystyrene resin (for example, isotactic polystyrene,
Syndiotactic polystyrene, atactic polystyrene, styrene-butadiene copolymer, acrylonitrile-butadiene styrene copolymer, impact-resistant polystyrene (a mixture of styrene and olefin rubber), etc.,
Examples include polyphenylene ether resins, polyolefin resins (eg, polymethylpentene, polypropylene, polyethylene, cyclic olefin polymers, etc.), polyacrylic resins, polycarbonate resins, polysulfone resins, and cellulose resins. Among them, particularly preferred are polystyrene resins and polyolefin resins such as polymethylpentene and polypropylene.

The amount of the thermoplastic resin to be blended with the polyester varies depending on the target amount of cavities formed in the plastic film and the stretching conditions, but is preferably in the range of 3 to 40% by weight, especially 5% by weight, based on the whole plastic film. ~ 1
5% by weight is preferred. If the amount is less than 3% by weight, there is a limit in increasing the amount of cavities formed, and it tends to be difficult to obtain the flexibility, light weight, or drawing properties imparted to the plastic film by forming cavities. On the other hand, if it exceeds 40% by weight, the stretchability of the film is liable to decrease, and the heat resistance, strength and stiffness of the plastic film tend to be impaired. The above thermoplastic resins can be used alone or in combination of two or more.

In addition, inorganic or organic particles may be added to the plastic film used in the present invention, if necessary, in order to improve concealing properties, drawing properties, and the like. Examples of the inorganic particles include silica, kaolinite, talc, calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, and titanium dioxide. As the organic particles, for example, organic white pigment,
Particles of benzoguanamine, cross-linked polystyrene, cross-linked acrylic resin and the like can be mentioned.

In the present invention, the plastic film may be a single-layer film or a composite film having two or more layers depending on the use. Although the method for producing the composite film is not particularly limited, from the viewpoint of productivity and the like, the raw materials of each layer are extruded from separate extruders, guided into one die, and an unstretched film is obtained. Lamination by a so-called co-extrusion method in which at least one axis is oriented is most preferable.

[0025] The surface-treated plastic film of the present invention comprises, on at least one side of the plastic film,
A surface treatment layer containing the antistatic agent and a copolyester resin and / or a crosslinking agent containing a blocked isocyanate group is formed.

Among them, the surface-treated plastic film using the fine void-containing film has an apparent specific gravity of 0.8 to 1.3, preferably 1.05 to 1.25, as described above. is there. The apparent specific gravity is 0.8
If it is less than 10, the void content becomes excessive, the strength of the surface-treated plastic film tends to be insufficient, and cracks and wrinkles tend to be easily generated on the surface of the surface-treated plastic film. Conversely, if the apparent specific gravity exceeds 1.3, the void content ratio becomes insufficient, and the cushioning property, flexibility, and drawing properties with a pencil or the like tend to decrease.

The apparent specific gravity can be adjusted by the kind and amount of a cavity developing agent, ie, a thermoplastic resin that is incompatible with polyester, and by film forming conditions, especially stretching conditions.

Here, the apparent specific gravity was measured as follows. 5cm × 5c surface-treated plastic film
m was accurately cut out into squares, the thickness was measured at 50 points, the average thickness was set to tμm, and the weight was measured to the nearest 0.1 mg to obtain wg, which was calculated by the following equation. Apparent specific gravity = w × 10000 / (5 × 5 × t)

The surface-treated plastic film of the present invention using a plastic film containing or not containing fine cavities has a light transmittance of 30% or less and an in-plane birefringence of -0.02 or more and +0.04 or less. Are preferred.

That is, the surface-treated plastic film of the present invention has a light transmittance of preferably 30% or less, more preferably 20% or less, and still more preferably 15% or less, in order to enhance suitability as synthetic paper. If the light transmittance exceeds 30%, the back will be seen through, and the appearance of the printed matter may be hindered.

The light transmittance can be adjusted by adjusting the content of fine voids and the amount of added particles.

Here, the light transmittance is JIS-K6714.
In accordance with the Poick integrating sphere formula H. T. The total light transmittance of the surface-treated plastic film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.).

The surface-treated plastic film of the present invention preferably has an in-plane birefringence of -0.02 to +0.04, more preferably 0 to +0.03. By making the in-plane birefringence -0.02 or more, preferably 0 or more, the film becomes a substantially isotropic film,
The film can be made less likely to tear in the lateral direction. However, when the in-plane birefringence exceeds +0.04, on the other hand, the film tends to be vertically torn, which is likely to cause breakage when slitting the film or crack in the longitudinal direction when cutting. Tend. Also, the in-plane birefringence is-
If it is less than 0.02 or more than +0.04, wrinkling or curling tends to occur when printing with a printer or the like. Here, the fact that the in-plane birefringence is + (or-) means that the history of longitudinal stretching is larger (or smaller) than the history of transverse stretching, and a so-called bowing phenomenon at the time of transverse stretching. May cause some distortion of the principal axis of the refractive index.

Here, the in-plane birefringence was measured as follows. 10cm × 10c surface treated plastic film
m, and the weight W (g) is weighed.
And the density ρ when there are no cavities inside the film
(G / cm ³ ), the actual thickness T (cm) of the film irrespective of the void content is calculated by the following equation. T = W / (ρ × 100) Next, using a molecular orientation meter MOA-2001A (manufactured by Kanzaki Paper Co., Ltd.) and substituting the thickness T obtained above, the refractive index in the microwave region is set to the longitudinal main axis. The in-plane birefringence was determined by the following equation along the lateral main axis. In-plane birefringence = longitudinal principal axis refractive index-transverse principal axis refractive index The density ρ was calculated from the composition ratio of each component constituting the surface-treated plastic film and its density.

The method for producing the plastic film used in the present invention is not particularly limited. In particular, as a method for producing the fine void-containing film, an unstretched film obtained by molding a mixture containing a polyester and a thermoplastic resin incompatible with the polyester into a film is formed in one or preferably multiple stages in the longitudinal direction. After stretching to 3.0 times or more, a relaxation treatment of 3% or more is performed in the longitudinal direction, and then a transverse stretching is performed at a magnification equal to or more than the longitudinal stretching ratio after the relaxation treatment, and then heat treatment is performed.

In the first longitudinal stretching step, longitudinal stretching is performed in the running direction of the film while appropriately heating between two or many rolls having different peripheral speeds. As the heating means at this time, a method using a heating roll, a method of heating with hot air, radiant heat or the like in a non-contact state with a roll or the like can be adopted. Alternatively, these can be used in combination. However, in this longitudinal stretching step, in order to effectively cause peeling at the interface between the polyester and the thermoplastic resin which is incompatible with the polyester and efficiently develop cavities in the film, the stretching temperature should be (Tg + 10) ° C. (Tg + 50) ° C
(Tg: glass transition temperature of polyester), and it is preferable to perform longitudinal stretching at a stretching ratio of 3.0 times or more, preferably 3.2 to 5.0 times. If the longitudinal stretching ratio is less than 3.0 times, it is difficult to sufficiently develop fine cavities inside the film, and it tends to be difficult to reduce the apparent specific gravity of the finally obtained surface-treated plastic film to 1.3 or less. is there. On the other hand, when the longitudinal magnification exceeds 5 times, it is difficult to sufficiently perform the subsequent relaxation treatment, and it is substantially difficult to reduce the in-plane birefringence of the surface-treated plastic film to +0.04 or less.

After the above-described longitudinal stretching, a relaxation treatment of 3% or more, preferably 5% or more in the longitudinal direction is performed. The more preferable relaxation rate varies depending on the longitudinal stretching ratio performed before the relaxation, but it is preferable to set the longitudinal stretching ratio after the relaxation to be 2.8 to 3.5 times. If the relaxation rate is set to 3% or more, the in-plane birefringence becomes −0.02 to +0.0.
It becomes possible to produce the surface-treated plastic film of No. 4 industrially stably. On the other hand, if the relaxation rate is less than 3%, the transverse stretchability to be performed in the next step is significantly deteriorated, and it tends to be difficult to produce a film having an in-plane birefringence of −0.02 to +0.04. . If the surface-treated plastic film has an apparent specific gravity of more than 1.3 (using a film having a small content of fine voids), it is possible to impart isotropy without performing such relaxation treatment. As described above, in order to produce a low-specific-gravity-containing film having low specific gravity, which is flexible, lightweight, and excellent in drawing properties, it is preferable to perform the above-described relaxation treatment.

As described above, the preferred longitudinal stretching ratio after the longitudinal relaxation treatment is 2.8 to 3.5, and when the longitudinal stretching ratio is less than 2.8, the relaxation is poor and uneven. Tends to be difficult to obtain a uniform film,
In addition, the in-plane birefringence of the finally obtained surface-treated plastic film tends to be less than -0.02.
Conversely, if the longitudinal stretching ratio after relaxation exceeds 3.5 times, poor stretching is likely to occur during transverse stretching, and the in-plane birefringence of the surface-treated plastic film after biaxial stretching is +0.04.
Tend to exceed.

As a method for performing the relaxation treatment, a method of once cooling the longitudinally stretched film and then reheating it to about 80 to 150 ° C. in a heating device such as an oven, A method of relaxing by reheating between groups, a method of relaxing between a driving roll group or a free roll group heated to about 60 to 100 ° C., and a method of appropriately combining these methods. Can be adopted. Among these, particularly preferred is a relaxation treatment method mainly comprising a method of performing a relaxation treatment without cooling immediately after longitudinal stretching, and according to this method, a heat loss is small and a more uniform relaxation treatment is efficiently performed. It can be carried out.

After the relaxation treatment, the film is introduced into a tenter, and is subjected to a transverse stretching at a magnification equal to or greater than the longitudinal stretching magnification after the relaxation treatment, followed by heat treatment. The preferred transverse stretching temperature is not less than the maximum temperature of longitudinal stretching / relaxation treatment and not more than (Tm-10) ° C (Tm: melting point of polyester). When the transverse stretching ratio is lower than the longitudinal stretching ratio after the relaxation treatment, the in-plane birefringence of the obtained surface-treated plastic film tends to be hardly reduced to +0.04 or less. Although the upper limit of the transverse stretching ratio is not particularly limited, the in-plane birefringence of the surface-treated plastic film finally obtained under stable stretchability is surely −
To make it 0.02 or more, the longitudinal stretching ratio after the relaxation treatment is +
It is preferable to keep it 1.0 times or less.

The biaxially stretched film thus obtained is preferably subjected to a heat treatment if necessary. The heat treatment is preferably performed in a tenter, and the heat treatment temperature is preferably in the range of (Tm-50) to Tm ° C. Further, in parallel with the heat treatment, re-lateral stretching or transverse relaxation treatment can be performed.

The method for producing the surface-treated plastic film of the present invention, that is, the method for forming a surface coating layer on the surface of the plastic film obtained as described above, includes an antistatic agent, a copolyester resin and / or a block. A coating solution is prepared by previously mixing a predetermined amount of a crosslinking agent containing a type isocyanate group and a solvent, and a gravure coater, a reverse kiss coater, a reverse roll coater,
The coating solution may be applied using a usual coating device such as a multilayer curtain coater, a bar coater or an air doctor coater, and the application method is not particularly limited. The coating amount (wet state) of the coating liquid is 1 m ^{2 of} plastic film.
Per 5 to 50 g is good.

As the timing of application, any method such as a method of applying before stretching a plastic film, a method of applying after stretching in a longitudinal direction, and a method of applying to a film which has been subjected to an orientation treatment may be adopted. In order to enhance the adhesion between the plastic film and the surface coating layer, the most preferable is to apply a coating solution on at least one surface of the uniaxially stretched plastic film by the above-mentioned coating method and then to make a right angle to the further uniaxial stretching direction. This is an in-line coat extending in the direction of.

The surface coating layer containing the above three components may be mixed with various additives such as an organic filler, an inorganic filler, an antioxidant, a surfactant and a lubricant, if necessary. Good. The amount of these additives is preferably 1 to 500% by weight based on the weight of the copolymerized polyester resin.
And more preferably 10 to 300% by weight.

The thickness of the surface coating layer (after drying) is 0.0
05 to 20 μm, more preferably 0.01 to 20 μm.
１1 μm. If it is less than 0.005 μm, there is a tendency that sufficient adhesion to a plastic film cannot be obtained. Conversely, if it exceeds 20 μm, it tends to be difficult to apply uniformly due to problems such as physical properties and rheology of the coating solution, and equipment.

[0046]

EXAMPLES Hereinafter, the structure and operation and effect of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention is applicable to the above and following points. It is, of course, possible to carry out the present invention with appropriate modifications within the scope of the invention, and all of them are included in the technical scope of the present invention. The methods for measuring and evaluating various physical properties and performances employed in the following examples are as follows.

(1) Antistatic Property The surface-treated plastic film was allowed to stand for 24 hours under the conditions of a relative humidity of 65% and 20 ° C., and the antistatic property of the surface coating layer was measured with a Hiresta (manufactured by Mitsubishi Yuka).

(2) Printability Sheet-fed offset printing press (Ryobi 3302M, manufactured by Ricoh Company) and offset ink for synthetic paper (POP-VIP)
(Black), POP-VIP (red), manufactured by Dainippon Ink Co., Ltd.), and the surface of each sample film (surface coating layer side)
Was actually printed, and the inking property of the solid portion of the second color ink was visually evaluated. The evaluation is as follows. ：: The inking property was good (a state in which the ink was uniformly transferred and there was no spot). ×: Ink adhesion was poor (there was uneven transfer of ink and low density).

(3) Measurement of contact angle with water The contact angle between the surface coating layer of the surface-treated plastic film and water was measured using a contact angle meter (manufactured by Elmo) under an atmosphere of 23 ° C. and 65% RH. Measured.

(4) Ink Adhesion The ink adhesion was evaluated based on the following method. In the case of an oxidative polymerization (or solvent) type ink, the ink is printed on a surface coating layer of a surface-treated plastic film by a Tetron screen (# 250 mesh), and then air-dried for one day. In the case of a UV curable ink, after printing on a surface coating layer of a surface-treated plastic film by a Tetron screen (# 300 mesh),
500 mj / V
A UV exposure of cm ² is given to cure the UV ink. Next, a 100 mm cross cut surface of a 2 mm square was inserted into each ink surface with a cutter, and a cellophane tape (manufactured by Nichiban Co., 25 mm width) was stuck thereon so that air bubbles did not enter.
Furthermore, rub it on it to make it adhere well, hold both ends of the ink surface before and after the cellophane tape is not adhered by hand, and peel off rapidly in the direction above the cellophane tape (angle of 90 °). The ink surface was observed, and the adhesion was evaluated based on the ink residual ratio. The inks used and the evaluations are as follows.

<Ink brand used> 1) Oxidative polymerization (or solvent) type ink No. 9 for polyester manufactured by Jujo Kako Ink Co., Ltd. RAM Black manufactured by Seiko Advance Co., Ltd. SS-8 grass for PVC manufactured by Toyo Ink Co., Ltd. 2) UV curable ink FDSS black manufactured by Toyo Ink Co., Ltd. UVA black manufactured by Seiko Advance Co., Ltd.

<Determination Method> After the cross-cut surface was peeled off, the ink residual ratio was evaluated based on the following four criteria. A: No peeling at 100% residual rate. ：: A residual ratio of 90% or more and less than 100% can be used without any practical problem. Δ: When the residual ratio is 70% or more and less than 90%, the adhesion is slightly weak and a problem may occur in practical use. X: There is a problem in adhesion when the residual ratio is 50% or more and less than 70%.

Example 1 0.3% by weight of an ethosulfate salt of quaternary ammonium cation "Katiogen ES-L" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an antistatic agent, and "Vylonal MD" as a copolymerized polyester resin. -1200 "(manufactured by Toyobo Co., Ltd.) in an amount of 2.5% by weight, and using a stirrer, water and isopropyl alcohol (weight ratio 70/30).
And a coating solution was prepared. This coating solution was applied to a 50 μm-thick polyester film (polyester film containing fine cavities) manufactured by the following method using a wire bar (No. 8). The coating amount of the coating liquid was about 12 g (wet state) per 1 m ² of the polyester film.
After drying for 2 seconds, heat treatment was performed at 200 ° C. for 30 seconds to obtain a surface-treated plastic film having a surface coating layer of 0.34 g / m ² .

(Preparation of polyester film containing fine voids) As raw materials, 83% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62, 13% by weight of polystyrene having a melt flow index of 2.0 g / 10 minutes, and an average particle diameter of 0.3 μm ( Electron microscopy) anatase type titanium dioxide 4
The mixture is supplied to an extruder, melt-extruded at 290 ° C., and cast on a cooling drum at 30 ° C. by an electrostatic adhesion method to produce an unstretched film having a thickness of 500 μm. did. Next, the film was heated by a roll heated to 70 ° C., further heated using an infrared heater, and subjected to 3.7 times longitudinal stretching in the longitudinal direction between rolls having different peripheral speeds. At this time, the stretching roll temperature on the high speed side was set to 70 ° C. Immediately after the completion of the longitudinal stretching, a 14% relaxation treatment was applied between the rolls without cooling, and the longitudinal stretching ratio after relaxation was set to 3.2.
Next, the longitudinally stretched / relaxed film is guided to a tenter,
After preheating at 140 ° C. for 8 seconds, 3.6 mm in the horizontal direction at the same temperature.
It was stretched twice. Thereafter, the sheet was heat-treated at 220 ° C. for 5 seconds, further re-stretched in the transverse direction by 8% at the same temperature, and further heat-treated at the same temperature for 5 seconds. By this method, a polyester resin film containing fine cavities having an average thickness of 50 μm was obtained.

The properties of the obtained surface-treated plastic film are as shown in Table 1. The adhesiveness between the film surface and the solvent ink, the antistatic property and the offset printability were extremely excellent.

[0056]

[Table 1]

Example 2 0.3% by weight of an ethosulfate salt of quaternary ammonium cation "Katiogen ES-L" as an antistatic agent, and "Vironal MD" as a copolymerized polyester resin.
-1200 "as a cross-linking agent containing 1.25% by weight of a blocked isocyanate group.
8 "(manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 2.5% by weight of" Eposta MS "(Nippon Shokubai Co., Ltd.) as organic particles. A surface-treated plastic film was obtained.

Example 3 Ethosulfate salt of quaternary ammonium cation "TIE612" (manufactured by Takemoto Yushi Co., Ltd.) as an antistatic agent
0.55% by weight, and 9% by weight of “Vironal MD-1200” as a copolymerized polyester resin, and water and isopropyl alcohol (weight ratio 70
/ 30) to give a coating solution. This coating solution was applied using a wire bar (No. 8) onto a 200 μm-thick uniaxially stretched microvoided polyester film produced by the following method.
The coating amount of the coating liquid was about 12 g (wet state) per 1 m ² of the polyester film. After the coating, the coating liquid was dried at 70 ° C. for 60 seconds, and then 14 ° perpendicular to the uniaxially stretched direction.
Stretched 3.6 times at 0 ° C., heat-treated at 220 ° C. for 5 seconds, re-stretched at the same temperature in the transverse direction by 8%, and heat-treated at the same temperature for 5 seconds to obtain a surface coating of 0.29 g / m ² . A surface-treated plastic film having a layer was obtained.

(Preparation of uniaxially stretched polyester film containing microvoids) As raw materials, 83% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62, 13% by weight of polystyrene having a melt flow index of 2.0 g / 10 minutes, and an average particle size of 0% A mixture of 4% by weight of 0.3 μm (electron microscopic) anatase type titanium dioxide is supplied to an extruder, melt-extruded at 290 ° C., and cast on a cooling drum at 30 ° C. by an electrostatic adhesion method. Thereby, an unstretched film having a thickness of 650 μm was produced. Next, the film was heated by a roll heated to 70 ° C., further heated using an infrared heater, and stretched 3.7 times in the longitudinal direction between rolls having different peripheral speeds. At this time, the stretching roll temperature on the high speed side was set to 70 ° C. Immediately after the completion of the longitudinal stretching, a 14% relaxation treatment was applied between the rolls without cooling, and the longitudinal stretching ratio after relaxation was 3.2.
Thus, a uniaxially stretched fine void-containing polyester resin film having a thickness of 200 μm was obtained.

Example 4 0.55% by weight of an ethosulfate salt of quaternary ammonium cation “TIE612” as an antistatic agent, and “Vironal MD-120” as a copolymerized polyester resin
0 "is 4.5% by weight," Elastron BN-11 "(manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is 4.5% by weight as a crosslinking agent containing a blocked isocyanate group, and" Eposta MS "is 9 as organic particles. A surface-treated plastic film was obtained in the same manner as in Example 3 except that the amount by weight was used.

The results of evaluating the properties of the surface-treated plastic films obtained in Examples 2 to 4 are as shown in Table 1, and the same good results as in Example 1 were obtained.

Comparative Example 1 No antistatic agent was used, and 1.25% by weight of "Vylonal MD-1200" was used as a copolymerized polyester resin, and "Elastron H-38" was used as a crosslinking agent containing a blocked isocyanate group. A surface-treated plastic film was obtained in the same manner as in Example 4, except that 0.25% by weight and 2.5% by weight of “Eposta MS” were used as the organic particles.

The results of evaluation of the properties of the obtained film are as shown in Table 2. The offset printability and ink adhesion were good, but no antistatic property was exhibited.

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[Table 2]

Comparative Example 2 A surface-treated plastic film was obtained in exactly the same manner as in Example 2, except that 0.08% by weight of "sodium paraffin sulfonate" (manufactured by Matsumoto Yushi Co., Ltd.) was used as an antistatic agent. Was.

Comparative Example 3 A surface-treated plastic film was obtained in exactly the same manner as in Example 4, except that 0.03% by weight of "sodium paraffin sulfonate" was used as an antistatic agent.

The results of evaluating the properties of the films obtained in Comparative Examples 2 and 3 are as shown in Table 2. The antistatic properties and the ink adhesion were good, but the offset printability was insufficient. there were.

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According to the surface-treated plastic film of the present invention, by treating at least one side of the film, the contact angle with water becomes 45 ° or more, and both the antistatic property and the offset printing property are excellent, and as a synthetic paper, Extremely useful.

Claims (6)

[Claims] 1. A surface coating layer comprising: a plastic film; and an antistatic agent formed on at least one side of the film, a copolymerized polyester resin and / or a crosslinking agent containing a blocked isocyanate group. A surface-treated plastic film having a contact angle between water and water of 45 degrees or more. 2. The surface-treated plastic film according to claim 1, wherein the antistatic agent is a cationic antistatic agent. 3. The surface-treated plastic film according to claim 2, wherein the cationic antistatic agent is an ethosulfate salt of a quaternary ammonium cation. 4. The surface-treated plastic film according to claim 1, wherein the plastic film is a polyester film. 5. A polyester film comprising a polyester and a thermoplastic resin incompatible with the polyester.
5. The surface-treated plastic according to claim 4, wherein the surface-treated plastic film contains fine voids by being stretched in at least one axis direction, and has an apparent specific gravity of 0.8 to 1.3. the film. 6. A light transmittance of 30% or less and an in-plane birefringence of −0.02 or more and +0.04 or less.
5. The surface-treated plastic film according to any one of 5.