JP2000289171A - Polyester coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester coating film having enhanced printability by preventing dislocation an ink while maintaining ink receptivity. SOLUTION: In a polyester film comprising a coating layer having an opacity rated as an optical density of 0.3 or above on at least one side surface, the coating layer contains an at least one type of resin component selected from a polyester, a polyurethane, or acrylic copolymer, at least one type of inert particles, and a ratio d/t of a mean particle size d (μm) of the particles in the layer to a thickness t (μm) of the resin component is 1.0 to less than 5.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester-based coated film having good ink adhesion and excellent printability, and is particularly suitable as a base material for labels.

[0002]

2. Description of the Related Art Polyester films are used in a wide range of applications because of their high crystallinity, excellent transparency, gloss, mechanical properties, and chemical resistance. Further, it is common practice to form a coating layer on the surface of the polyester film for the purpose of imparting functions such as printability, blocking resistance and antistatic property. In addition, the transparency and handling properties of the film (blocking resistance,
In order to achieve both slip and abrasion resistance), it is also common practice to include particles in the coating layer of the polyester film to form irregularities on the film surface.

[0003] However, in the case of sticker printing, which is frequently used as a label printing method in printing, and in the case of offset printing, when the surface to be printed and the roll of the printing machine slip, the film and the roll rub and particles are coated. There is a problem that a problem occurs that the material is scraped off from the layer, becomes powder, and falls off the surface of the coating layer. Heretofore, attention has not been paid to the detachment of particles from such a coating layer. If the particles fall, not only the above-mentioned properties are lost, but also the fallen powder causes roll contamination. Another problem is that ink loss occurs and the commercial value is reduced.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to prevent ink bleeding by maintaining at least one surface of a polyester film while maintaining ink adhesion as in the prior art. To provide a polyester-based coated film having improved printability.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, determined that the ratio of the thickness of the resin component in the coating layer to the average particle size of the inert particles was within a specific range. By doing so, it has been found that a polyester-based coated film having both ink adhesion and printability can be obtained.

That is, the object of the present invention can be achieved by the following means. 1) In a polyester film having an opacity of 0.3 or more in optical density and having a coating layer on at least one surface, the coating layer is made of at least one selected from polyester, polyurethane, and acrylic copolymers. A resin component and at least one or more inert particles, and an average particle diameter d of the inert particles in the coating layer.
(Μm) and the thickness d (t) of the resin component, d / t, is 1.
A polyester-based coating film having a value of 0 or more and less than 5.0. 2) A polyester-based coated film, wherein the polyester-based film according to the above item 1 comprises at least 60% or more of polyethylene terephthalate. (3) The polyester-based coated film as described in (1) or (2) above, wherein the polyester-based film is stretched at least uniaxially and has a thickness of 5 to 300 μm. 4) A polyester film contains cavities inside the film, and the apparent specific gravity of the film is 0.3 to 1.3.
g / cm ³ , wherein the polyester-based coated film according to any one of the above items 1 to 3, wherein 5) The thickness t of the resin component of the coating layer is 0.01 to 5.
The polyester-based coating film according to any one of the above items 1 to 4, wherein the thickness is 0 μm. 6) The average particle diameter d of the inert particles in the coating layer is 0.0
4 to 10.0 μm.
The polyester-based coated film according to the above. 7) The resin / particle weight ratio in the coating layer is 30/7.
7. The polyester-based coated film according to any one of the above items 1 to 6, wherein the ratio is from 0 to 70/30. 8) The polyester according to any one of 1 to 7 above, wherein the resin of the coating layer comprises a water-insoluble and water-dispersible polyester resin and an aqueous urethane prepolymer having at least one blocked isocyanate in a molecule. Coating film. 9) The polyester-based coating film as described in any one of 1 to 8 above, wherein the surface resistance of the coating layer is 1 × 10 ¹³ Ω / □ or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyester resin used in the polyester film of the present invention includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid or esters thereof, and ethylene glycol, diethylene glycol, 1, 4 -Butanediol,
It mainly comprises a polyester obtained by polycondensing glycols such as 1,6-hexamethylene glycol and neopentyl glycol. Of course, it is needless to say that copolymerizable aromatic, aliphatic and alicyclic dicarboxylic acids and aromatic, aliphatic and alicyclic glycols may be contained as components of the polyester resin. These polyesters are prepared by a method of subjecting an aromatic dicarboxylic acid and a glycol to polycondensation after an esterification reaction, a method of subjecting an alkyl ester of an aromatic dicarboxylic acid to a glycol to a polycondensation after an ester exchange reaction, It can be produced by a known method such as a method of polycondensing an ester. Representative examples of such polyesters include polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. This polyester may be a homopolymer or a copolymer of the third component. In any case, in the present invention, a polyester having ethylene terephthalate, butylene terephthalate, and ethylene-2,6-naphthalate units of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable.

[0008] The polyester film of the present invention is particularly preferably a biaxially oriented film from the viewpoint of practicality such as strength and stiffness.

The polyester film of the present invention is preferably partially or entirely opaque. The opacity of the polyester film needs to have an optical density of 0.3 or more, and preferably 0.3 to 4.0. Particularly preferably, it is 0.5 to 3.0. If the optical density is less than 0.3, the printing effect is unclear when printing is performed on the surface, which is not preferable. Further, when the optical density exceeds 4.0, further printing effect cannot be expected, and it is necessary to add a large amount of inorganic particles contained in the polyester or a resin incompatible with the polyester, which causes a cost increase. Becomes

The method for obtaining the optical density within the above range is not particularly limited, but it can be achieved by incorporating inorganic particles or a resin incompatible with the polyester in the polyester. The content of these is not particularly limited,
In the case of inorganic particles, it is 5 to 35% by weight, preferably 8 to 25% by weight based on the produced polyester. On the other hand, when an incompatible resin is contained, 5 to 3
It is 5% by volume, preferably 8 to 28% by volume.

The inorganic particles used are not particularly limited.
Average particle size is 0.1-4 μm, preferably 0.3-1.5
μm inorganic particles. Specifically, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate,
Silica, alumina, talc, kaolin, clay and the like or a mixture thereof, and further used in combination with other general inorganic particles such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride and the like. Is also good.

The resin incompatible with polyester is not particularly limited. For example, in the case of mixing with polyethylene terephthalate, acrylic resin, polyethylene, polypropylene, polymethylpentene, modified olefin resin, polystyrene, polystyrene Examples include butylene terephthalate resin, phenoxy resin, polyphenylene oxide, and polycarbonate. As a matter of course, it can be used in combination with the above-mentioned inorganic particles. Needless to say, various whitening agents may be added as necessary.

Further, the polyester film of the present invention is preferably made of a thermoplastic polyester resin containing fine cavities having an apparent specific gravity of 0.3 to 1.3. It is also particularly useful because the fine cavities contained in the film cause light scattering at the interface with the matrix, whereby the opacity is further improved and the addition of the inorganic particles can be reduced. Further, the inclusion of the fine cavities can reduce the weight of the resin layer itself, so that it is easy to handle and has a great economic effect such as a reduction in raw material costs and transportation costs.

As a method for obtaining such a polyester film containing fine cavities, a sheet obtained by adding the above-mentioned incompatible resin to the thermoplastic polyester resin matrix, kneading the mixture, and dispersing the resulting mixture in the form of fine particles is used. A known method, such as a method of forming a cavity around the incompatible resin fine particles by stretching in the direction, can be used.

Further, it is preferable that at least one surface of the polyester film of the present invention is subjected to an easy adhesion treatment. Examples of the method of the easy adhesion treatment include a method by irradiation with active energy rays such as a corona discharge treatment, a plasma discharge treatment, an ultraviolet (UV) irradiation treatment and a radiation (EB) irradiation treatment, a flame treatment, and a vapor deposit such as PVD and CVD. Law. In particular, a method of applying a coating solution containing an easily adhesive resin composition to the surface of the polyester-based film, etc., from the viewpoint of adhesion to a coating layer, a printing ink layer, and other coating agents in the configuration of the present invention, This is the most effective method. As a composition for forming such a coating layer, a polyester-based resin, a polyurethane-based resin, an acrylic-based resin, a mixture thereof, a copolymer, or the like can be used.

Among the above easily adhesive resin compositions, a water-insoluble aqueous polyester resin containing a sulfone group in the molecule and an aqueous polyurethane resin having at least one blocked isocyanate in the molecule are used. The easy-adhesion layer is particularly preferable because it can significantly improve the adhesion to not only the polyester film as the base material but also the UV-curable printing ink. In this case, the aqueous polyester resin (A) and the aqueous polyurethane resin (B)
Is (A) / (B) = 90 / 10-1 by weight ratio.
0/90 is preferable, and (A) / (B) = 80 /
20-20 / 80 is particularly preferred.

In the polyester-based coated film of the present invention, the average particle size d (μ
m) and the thickness d (t) of the coating layer resin component, d / t,
It is necessary to be 1.0 or more and less than 5.0, preferably 1.2 or more and less than 4.0, and most preferably 1.
5 or more and less than 2.5. When d / t is less than 1.0, there is a tendency that sufficient ink deposition property, printing paper feeding property and blocking resistance cannot be obtained. Conversely, if it is 5.0 or more, particles tend to fall off the film during printing and cause powder drop.

The thickness of the resin component of the coating layer is from 0.01 to
5.0 μm is preferable, and more preferably 0.05 to
It is 1.5 μm, particularly preferably 0.1 to 1.0 μm. When the thickness of the resin component of the coating layer is less than 0.01 μm, sufficient adhesion to the film cannot be obtained, and the particles cannot be sufficiently fixed in the coating layer, and the particles tend to fall off the coating layer. is there. On the other hand, if it exceeds 5.0 μm, the particles are buried in the resin of the coating layer, and there is a tendency that surface irregularities and blocking resistance, which are indispensable for the handleability of the film, cannot be obtained.

In the present invention, the inert particles to be contained in the coating layer of the polyester film include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay and the like, or a mixture thereof. And other common inorganic particles such as calcium phosphate, mica, hectorite,
Examples include inorganic particles such as zirconia, tungsten oxide, lithium fluoride, calcium fluoride, and the like, and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone.

The average particle size of the inert particles in the coating layer is as follows:
It is preferably from 0.04 to 10.0 μm, more preferably from 0.06 to 2.0 μm, particularly preferably from 0.1 to 1.0 μm.
μm. When the average particle size of the inert particles is less than 0.04 μm, the formation of irregularities on the film surface is insufficient, and the ink adhesion tends to be insufficient. Conversely, 1
If it exceeds 0.0 μm, particles tend to fall off the film and cause powder drop.

Among the above particles, the particle size ratio (major axis / minor axis)
Are in the range of 1.0 to 1.5, and the inactive particles having a standard deviation of the particle diameter of 1.0 or less are preferred from the viewpoint of the resistance to falling off of the particles. Particularly preferably, the particle size ratio (major axis / minor axis) is 1.0 to 1.2.
And inactive particles having a standard deviation of particle diameter of 0.5 or less. Inert particles satisfying this requirement include spherical monodisperse silica particles, crosslinked spherical polystyrene particles, crosslinked spherical acrylic particles, spherical or cubic calcium carbonate particles having a vaterite structure, and the like.

The average particle size, the particle size ratio and the standard deviation of the particle size of the inert particles in the coating layer are described in, for example, JP-A-1-284.
534 can be obtained.

In the coating layer, the weight ratio of resin / particle is preferably 30/70 to 70/30, more preferably 35/65 to 60/40, and particularly preferably 40/60.
５０50/50. If the weight ratio of the resin is less than 30, the particles cannot be sufficiently fixed in the coating layer, and the particles tend to fall off the coating layer and cause powder drop. On the other hand, if the ratio of the resin exceeds 70, there is a tendency that sufficient ink deposition property, paper feeding property and blocking resistance cannot be obtained.

When the coating layer composition further contains an antistatic agent, various steps for labeling the resulting film, such as coating with an adhesive, printing, cutting, punching, etc. This is particularly preferable because the occurrence of static electricity troubles can be prevented. As antistatic agents,
What is generally used as a coating type antistatic agent is arbitrarily used.

Means for providing the coating layer include roll coating such as gravure coating, reverse coating, and kiss coating, bar coating, air knife, blade coating, comma coating, curtain coating, spraying, and dip coating. A commonly used method such as a method can be applied.

As a step of applying, a method of applying in advance to the surface of an unstretched polyester film, a method of applying the film to a film surface oriented in an axial direction, and further orienting the film surface in a perpendicular direction, and a method of applying a biaxially oriented film Any method such as a method of applying the film to the film surface is possible, but in particular, a method of applying the film to a uniaxially oriented film surface and then stretching and orientating in a perpendicular direction to complete the crystallization is a method of adhesion, economy,
This is the most preferable method in terms of cleanliness and the like.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited by the following examples. The methods for measuring and evaluating various physical properties and performances employed in the following examples are as follows.

(1) Printability After printing on the surface of the polyester-based coating film on the coating layer side with a UV curable ink, the irradiation energy was 500 mJ / cm ^2.
UV irradiation treatment was performed to obtain a print sample. The obtained sample was visually judged as follows. ：: The printed part is clear and easy to understand △: The printed part is slightly uneven ×: The printed part is uneven

(2) Ink Adhesion In the case of oxidative polymerization (or solvent) type ink, after printing on a surface coating layer of a polyester film with a screen (250 mesh), it is air-dried for one day. In the case of a UV curable ink, after printing on a surface coating layer of a polyester film with a screen (300 mesh), the UV exposure device is used to print 500 mJ /.
A UV exposure of cm ² is given to cure the UV ink. Next, a 100 mm cross cut surface of 2 mm square was put on each ink surface with a cutter, and a cellophane tape (25 mm
Width) is attached so that air bubbles do not enter, and further rubbed on it to make sufficient contact. After that, both ends of the ink surface before and after the cellophane tape is not adhered are pressed by hand, and the cross-cut surface is rapidly peeled in the direction above the cellophane tape (in the direction of an angle of 90 °). And the adhesion was evaluated. ◎: Residual rate 100% (does not peel at all) ○: Residual rate 90% or more and less than 100% (can be used without practical problems) △: Residual rate 70% or more and less than 90% (adhesion is slightly weak,
Possibility of causing a problem in practical use) ×: Residual rate 50% or more and less than 70% (problem in adhesion)

(3) Powder fall resistance Black paper was used for the contact portion between the load head and the film using a Gakushin type friction tester.
The state of the black paper after reciprocating 0 times and rubbing against the load head was visually determined as follows. ：: No powder on black paper at all △: 10 or less powders of 0.5 mm or less on black paper ×: 10 or more powders of 0.5 mm or less on black paper, or 0. With powder larger than 5mm

(4) Antistatic Property After the polyester film was seasoned at 23 ° C. and 65% RH for 24 hours, the surface resistivity (Ω / □) of the film coating layer surface was measured by a high resistivity meter. .

(5) Average Particle Size of Inactive Particles According to the description in JP-A-1-284534, at least 100 particles were measured using a scanning electron microscope and an image processing apparatus, and the average particle size was determined. μm).

(6) Thickness of Resin Component of Coating Layer A cross-sectional photograph of the film is taken with a scanning electron microscope, and the thickness of the resin component is measured on the photograph. The same measurement was performed 100 times at different locations, and the average of the measured values was defined as the thickness (μm) of the resin component.

(7) Opacity of Polyester Resin Film Using a Macbeth densitometer TR-927, the optical density of the transmitted light under a G filter was measured. The optical density is
Light transmittance (range: 0 to 100%) of the logarithm (Log ₁₀₎
Is represented as

(8) Apparent Specific Gravity of Polyester Resin Film The film was accurately cut into a square of 10 (cm) × 10 (cm), and its thickness was measured at 50 points to obtain an average thickness t (μ).
m). Next, the weight of the sample was measured up to 0.1 mg and set as W (g), and the value calculated by the following equation was defined as apparent specific gravity. Apparent specific gravity (g / cm ³ ) = (W / t) × 10
0

Example 1 Polyethylene terephthalate resin 8 having an intrinsic viscosity of 0.62
0% by weight and a melt flow index of 5.5 g / 10
% Of polystyrene and an average particle diameter of 0.3 μm
Is melted at 285 ° C. and extruded on a drum having a surface temperature of 40 ° C., and the obtained unstretched sheet is stretched 3.5 times at 90 ° C. The film was stretched to obtain a uniaxially stretched film.

As a copolymerized polyester resin, "Vironal" (manufactured by Toyobo Co., Ltd.) was 3.15% by weight in solid content.
"Elastron" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a water-soluble urethane resin having a terminal isocyanate group blocked with a hydrophilic group is 5.85% by weight in solids, and a quaternary ammonium salt-based antistatic as an antistatic agent A coating liquid was prepared as an agent, using 6.2% by weight based on the resin component and silica particles having an average particle diameter of 0.45 μm such that the resin / particle weight ratio was 42/58.

This coating solution was applied by a reverse kiss coating method so that the thickness of the resin solids after stretching was 0.3 μm, and then stretched 3.5 times in the horizontal direction at 120 ° C. while drying. Heat treatment was performed while relaxing at 4 ° C. by 4% to obtain a surface-treated polyester film having a thickness of 50 μm and containing about 25% by volume of fine voids inside. Tables 1 and 2 show the properties and evaluation results of the obtained films.

Example 2 The average particle size of the inert particles contained in the coating layer was 0.3 μm.
m and a resin / particle weight ratio of 45/55, and a film was obtained in exactly the same manner as in Example 1. Tables 1 and 2 show the properties and evaluation results of the obtained films.

Comparative Example 1 The average particle size of the inert particles contained in the coating layer was 2.0 μm.
Resin / particle weight ratio 50/50, resin thickness 0.27μ
Except having set it as m, it carried out similarly to Example 1, and obtained the film. In Comparative Example 1, the ratio (d / t) between the average particle diameter d of the inert particles in the coating layer and the thickness t of the resin layer was 7.41;
It is outside the upper limit of the claims of the present invention. Tables 1 and 2 show the properties and evaluation results of the obtained films.

Comparative Example 2 A film was obtained in exactly the same manner as in Example 1 except that the resin / particle weight ratio was 90/10 and the resin thickness was 0.49 μm. In Comparative Example 2, the ratio (d / t) between the average particle diameter d of the inert particles in the coating layer and the thickness t of the resin layer was used.
Is outside the lower limit of the present invention. Tables 1 and 2 show the properties and evaluation results of the obtained films.

[0042]

【table 1】

[0043]

[Table 2]

[0044]

Industrial Applicability The polyester-based coated film of the present invention can be used as a label base material, because it can prevent powder dropping and improve printability while maintaining ink adhesion.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C09D 5/00 C09D 5/00 Z 175/04 175/04 C09J 7/02 C09J 7/02 ZF Term (reference) 4F100 AK25B AK41A AK41B AK42A AK51B BA02 DE01B DJ00A EJ37A GB90 JB07B JG04B JN02A YY00A YY00B 4J004 CA06 CC02 FA01 4J038 CG141 DD001 DG001 DG291 DG301 KA20 MA14 PC08

Claims (9)

[Claims] An opacity of not less than 0.3 optical density,
In a polyester-based film having a coating layer on at least one side, the coating layer comprises a resin component composed of at least one selected from polyester, polyurethane, and acrylic copolymers, and at least one or more inert particles. And the ratio d / t of the average particle size d (μm) of the inert particles in the coating layer and the thickness t (μm) of the resin component.
Is 1.0 or more and less than 5.0. 2. A polyester-based coated film, wherein the polyester-based film according to claim 1 comprises at least 60% or more of polyethylene terephthalate. 3. The polyester coated film according to claim 1, wherein the polyester film is stretched at least uniaxially and has a thickness of 5 to 300 μm. 4. A polyester film containing voids inside the film, wherein the apparent specific gravity of the film is 0.3.
The polyester-based coated film according to any one of claims 1 to ³ , wherein the weight is from 1.3 to 1.3 g / cm3. 5. The method according to claim 1, wherein the thickness t of the resin component of the coating layer is 0.0
The thickness is 1 to 5.0 μm.
The polyester-based coated film according to the above. 6. An average particle diameter d of inert particles in the coating layer.
Is from 0.04 to 10.0 μm. 7. The polyester-based coated film according to claim 1, wherein the resin / particle weight ratio in the coating layer is 30/70 to 70/30. 8. A resin according to claim 1, wherein said resin of said coating layer comprises a water-insoluble and water-dispersible polyester resin and an aqueous urethane prepolymer having at least one blocked isocyanate in a molecule. The polyester-based coated film according to the above. 9. The coating layer having a surface resistance of 1 × 10 ¹³ Ω / □.
The polyester-based coated film according to any one of claims 1 to 8, wherein: