TW202413104A - Void-containing polyester-based easy adhesion film - Google Patents

Abstract

This void-containing polyester-based easy adhesion film: has a first coating layer B1 that contains a polyester resin containing an inorganic pigment, a void-containing layer A that contains voids therein, and a second coating layer B2 that contains a polyester resin containing an inorganic pigment laminated in this order; has a functional easy adhesion layer on the first coating layer B1; and has an apparent density of 0.80 g/cm3 or greater and 1.20 g/cm3 or less, the void-containing layer A containing a composition that contains a polyester resin, a polypropylene resin, and a silicone resin.

Description

Polyester film with holes for easy bonding

The present invention relates to a "void-containing polyester easy-adhesive film" containing voids inside.

As a method for obtaining a film having a function similar to that of paper, a method of making a film contain a large number of fine cavities inside the film is known.

This method is to mix an immiscible thermoplastic resin (hereinafter referred to as the immiscible resin) in a polyester resin to obtain a sheet in which the immiscible resin is dispersed in the polyester resin and extends in at least a uniaxial direction. In this way, this method causes voids to appear by peeling at the interface between the polyester resin and the immiscible resin. As such immiscible resins, for example, polyolefin resins such as polyethylene resin, polypropylene resin, and polymethylpentene resin (for example, refer to Patent Documents 1 to 3), and polystyrene resin (for example, refer to Patent Documents 4 and 5) have been proposed. Among these, polypropylene resin is excellent in terms of void appearance and cost performance.

Here, when the polypropylene resin is simply dispersed in the polyester resin, the dispersion diameter of the polypropylene dispersed particles becomes larger. Therefore, although it is easy to make voids appear, on the other hand, the voids become larger, sufficient shielding properties cannot be obtained, and the film-forming properties also deteriorate. Therefore, a method of microdispersing the polypropylene resin is adopted. So far, as a method for this microdispersion, a method of adding a dispersant such as a surfactant or polyethylene glycol has been proposed (for example, refer to Patent Document 6 and Patent Document 7). [Prior Technical Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 49-134755. [Patent Document 2] Japanese Patent Publication No. 2-284929. [Patent Document 3] Japanese Patent Publication No. 2-180933. [Patent Document 4] Japanese Patent Publication No. 54-29550. [Patent Document 5] Japanese Patent Publication No. 11-116716. [Patent Document 6] Japanese Patent Publication No. 7-17779. [Patent Document 7] Japanese Patent Publication No. 8-252857.

[The problem that the invention wants to solve]

However, when adding dispersants such as surfactants and polyethylene glycol, although it has a micro-dispersion effect on polypropylene resin, the polypropylene resin will deform in the heating and stretching step and the heat fixing step. Therefore, the resulting voids are also easily destroyed and sufficient lightness and cushioning properties cannot be obtained. Furthermore, since surfactants and polyethylene glycol have poor heat resistance, they are easily thermally degraded in the melt extrusion step when combined with polyester resin, resulting in a decrease in the whiteness of the resulting film. Depending on the situation, there is a problem of promoting the deterioration of polyester resin and worsening film-forming properties.

Furthermore, in recent years, in the printing industry, the speed of printing has been advancing, and higher adhesion than UV curing inks and the like is being sought.

The purpose of the present invention is to improve the problems of the above-mentioned prior art, and to provide a polyester-based easy-to-adhere film containing voids that is excellent in lightness, film-forming properties, shielding properties, whiteness, and easy adhesion, even when polypropylene resin is mainly used as a void-inducing agent. [Means for solving the problem]

As a result of active research, the inventors of the present invention have discovered the following by adding a very small amount of silicone resin to polypropylene resin. That is, the inventors of the present invention have discovered that the heat resistance of the dispersed polypropylene particles in the polyester resin can be improved, and the deformation of the dispersed polypropylene particles during heat extension and heat fixing can be reduced. In this way, the inventors of the present invention have discovered that a polyester-based easy-to-bond film containing voids with excellent lightness, film-forming properties, shielding properties, and whiteness can be obtained. Furthermore, the inventors of the present invention have discovered a polyester-based easy-to-bond film containing voids that can suppress the deterioration of coating and printing properties, which are side effects of silicone resins, by adjusting the layered structure and the amount of silicone resin added.

That is, the polyester-based easy-to-bond film containing voids of the present invention is completed by the following structure. 1. A polyester-based adhesive film containing voids, which comprises a first coating layer B1, a layer A containing voids and a second coating layer B2 laminated in sequence, wherein the first coating layer B1 comprises a polyester resin containing an inorganic pigment, the layer A containing voids comprises voids inside, the second coating layer B2 comprises a polyester resin containing an inorganic pigment, and a functional adhesive layer is provided on the first coating layer B1; the apparent density of the polyester-based adhesive film containing voids is greater than 0.80 g/ ^cm3 and less than 1.20 g/ ^cm3 ; the layer A containing voids comprises a composition containing a polyester resin, a polypropylene resin and a polysilicone resin. 2. The polyester-based adhesive film containing voids as described in the above Item 1, wherein in the above-mentioned void-containing layer A, the content of polydimethylsiloxane in the above-mentioned polysiloxane resin is 1 ppm or more and 2500 ppm or less relative to the total mass of the above-mentioned void-containing layer A. 3. The polyester-based adhesive film containing voids as described in the above Item 1, wherein in the above-mentioned void-containing layer A, the content of polydimethylsiloxane in the above-mentioned polysiloxane resin is 0.005 mass % or more and 2.000 mass % or less relative to 100 mass % of the above-mentioned polypropylene resin. 4. The polyester-based adhesive film containing voids as described in the above Item 1, wherein the inorganic pigment in the above-mentioned first coating layer B1 and the above-mentioned second coating layer B2 is titanium oxide. 5. The polyester adhesive film containing voids as described in the above Item 1, wherein the ratio of the sum of the thickness of the first coating layer B1 and the thickness of the second coating layer B2 to the sum of the thickness of the first coating layer B1, the thickness of the layer A containing voids and the thickness of the second coating layer B2 is 6% or more and 40% or less. 6. The polyester adhesive film containing voids as described in the above Item 1, wherein the total light transmittance is 1% or more and 30% or less. 7. The polyester adhesive film containing voids as described in the above Item 1, wherein the apparent density is 0.80 g/cm ³ or more and 1.10 g/cm ³ or less. 8. The polyester-based adhesive film containing voids as described in the above Item 1, wherein the functional adhesive layer has a close contact residual area of 99% or more as measured by the following evaluation method; wherein the evaluation method for the close contact residual area is as follows: UV (Ultraviolet) ink [manufactured by T&K TOKA (Co., Ltd.; trade name "BEST CURE (Registered Trademark) UV161 Blue S"] is used on the functional adhesive layer of the polyester-based adhesive film containing voids, and is printed by a printing press [manufactured by Mei Seisakusho (Co., Ltd.; trade name "RI TESTER"], and then the film coated with the ink layer is irradiated with a high-pressure mercury lamp at 40 mJ/cm ² , to cure the UV curing ink; then, using Nichiban cellophane tape (CT405AP-24), cut into 24mm wide and 50mm long pieces, and using a handy rubber roller to completely adhere the cellophane tape to the surface of the ink layer in a manner that prevents air from entering; then, vertically tear off the cellophane tape, and observe and determine the residual area (closely contacted residual area) (%) of the printed layer in an area of 24mm×50mm. 9. The polyester-based easy-to-bond film containing voids as described in item 1 above, wherein the functional easy-to-bond layer contains an antistatic agent, and the surface intrinsic resistance is less than 1.0×10 ¹³ Ω/sq. 10. The polyester-based adhesive film containing voids as described in item 1 above, wherein the number of pinhole-like shrinkages of the functional adhesive layer is 5 or less per ^square meter; wherein the number of pinhole-like shrinkages of the functional adhesive layer is evaluated by visually observing the functional adhesive layer of the polyester-based adhesive film containing voids under a 3-wavelength fluorescent lamp and counting the number of pinhole-like shrinkages. 11. The polyester-based adhesive film containing voids as described in any one of items 1 to 10 above, which is used for labels, cards, packaging materials or release films. [Effect of the invention]

The present invention can provide a polyester-based adhesive film containing voids which is excellent in lightness, film-forming property, concealing property, whiteness, and adhesion to various inks, even when the void-forming agent mainly contains polypropylene resin.

The present invention is described in detail below.

The polyester-based adhesive film containing voids of the present invention is preferably a laminated body having a first coating layer B1, a layer A containing voids, and a second coating layer B2 laminated in sequence, wherein the first coating layer B1 comprises a polyester resin containing an inorganic pigment, the layer A containing voids comprises voids inside, and the second coating layer B2 comprises a polyester resin containing an inorganic pigment. The layer A containing voids is preferably a composition comprising a polyester resin, a polypropylene resin, and a polysilicone resin. Furthermore, the apparent density of the polyester-based adhesive film containing voids is preferably 0.80 g/cm ³ or more and 1.20 g/cm ³ or less.

The polyester resin that is the main component of the void-containing layer A, the first coating layer B1, and the second coating layer B2 is preferably a polymer synthesized from a dicarboxylic acid or an ester-forming derivative thereof, and a diol or an ester-forming derivative thereof. Representative examples of such polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. Among these, polyethylene terephthalate is preferred from the viewpoints of mechanical properties, heat resistance, cost, and the like.

Furthermore, in these polyester resins, other components may be copolymerized as long as they do not impair the purpose of the present invention. Specifically, as copolymerization components, the dicarboxylic acid components include: isophthalic acid, naphthalene dicarboxylic acid, 4,4-diphenyl dicarboxylic acid, adipic acid, sebacic acid and ester-forming derivatives thereof. Furthermore, as diol components, the diethylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexanedimethanol may be listed. In addition, polyoxyalkylene glycols such as polyethylene glycol and polypropylene glycol may also be listed. As for the copolymerization amount, the repeating unit of each component is preferably within 10 mol%, and more preferably within 5 mol%.

As a method for producing polyester resin, for example, it is preferred to first use the aforementioned dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative as main starting materials, then preferably carry out esterification or transesterification reaction according to a conventional method, and then carry out polycondensation reaction at high temperature and reduced pressure to produce the polyester resin.

The limiting viscosity of the polyester resin is preferably 0.50 dl/g to 0.9 dl/g, and more preferably 0.55 dl/g to 0.85 dl/g, from the viewpoint of film-forming properties and recyclability.

The content of the polyester resin is preferably 70% to 97% by mass, and more preferably 75% to 95% by mass, relative to 100% by mass of the total components contained in the void-containing layer A. When the content of the polyester resin is 70% by mass or more, the polyester-based adhesive film containing voids can suppress the deterioration of film-forming properties. When the content of the polyester resin is 97% by mass or less, the polyester-based adhesive film containing voids can form voids by adding polypropylene resin and polysilicone resin.

Next, the polypropylene resin used as the immiscible resin in the present invention as the voiding agent is described. The void-containing polyester-based easy-adhesion film of the present invention adopts a specific layer structure, and by using a specific polypropylene resin, the voiding property can be maintained. Thereby, the void-containing polyester-based easy-adhesion film of the present invention can obtain sufficient lightness and cushioning properties, and has excellent film-making properties, shielding properties, and whiteness.

The polypropylene resin used in the present invention is preferably a crystalline polypropylene having a propylene unit content of preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably a crystalline polypropylene homopolymer having a propylene unit content of 100 mol%.

From the viewpoint of void appearance and film forming properties, the melt flow rate (MFR) of the polypropylene resin used in the present invention is preferably 1.0 g/10 minutes to 10.0 g/10 minutes, and more preferably 1.5 g/10 minutes to 7.0 g/10 minutes. When the MFR is 1.0 g/10 minutes to 10.0 g/10 minutes, it is difficult for the polypropylene dispersed particles to deform when extruded from the die, so it is easy to form voids. Furthermore, when the MFR is 1.0 g/10 minutes to 10.0 g/10 minutes, the dispersibility of the polypropylene dispersed particles is also excellent, sufficient shielding properties can be obtained, and film forming properties are also excellent. The melt flow rate (MFR) is a value measured at 230°C and a load of 2.16 kg in accordance with JIS K 7210.

In the polypropylene resin used in the present invention, from the viewpoint of void occurrence, the heat deflection temperature is preferably 85°C or higher, more preferably 90°C or higher, and further preferably 95°C or higher. As an upper limit, although no special restriction is required, it is preferably 135°C or lower. When the heat deflection temperature is 85°C or higher, especially in the longitudinal stretching step of stretching the film by heating above the glass transition temperature of the polyester resin described later, since the dispersed particles of the polypropylene become difficult to be destroyed, it becomes easy to form voids. Furthermore, the heat deflection temperature is a measured value when the bending stress of the test piece is 0.45 MPa according to the B method of JIS K 7191-1 and JIS K 7191-2.

From the viewpoint of void appearance and suppression of thermal degradation in the extrusion step and the recovery step, the weight average molecular weight (Mw) of the polypropylene resin used in the present invention is preferably 200,000 to 450,000, and more preferably 250,000 to 400,000. When the Mw is 450,000 or less, the dispersibility of the polypropylene dispersed particles becomes good, sufficient shielding can be obtained, and excellent film-forming properties are obtained. When the Mw is 200,000 or more, since the polypropylene dispersed particles become difficult to deform, it becomes easy to form voids. When the Mw is 200,000 or more, even when using recycled raw materials, it is preferable because the decrease in void appearance can be suppressed.

Furthermore, the molecular weight distribution (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably from 2 to 6, and more preferably from 2 to 5. Mw/Mn is an index representing the breadth of the molecular weight distribution, and the larger the value, the wider the molecular weight distribution. When Mw/Mn is less than 6, the low molecular weight components are reduced, so even when recycled raw materials are used, the reduction in whiteness and the appearance of voids can be suppressed, which is better. Furthermore, as long as Mw/Mn is more than 2, it is suitable for industrial production from a cost point of view. Furthermore, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values measured by gel permeation chromatography (GPC).

From the viewpoint of void appearance and film forming properties, the content of the polypropylene resin is preferably 3 mass % or more and 30 mass % or less, and more preferably 5 mass % or more and 25 mass % or less, relative to 100 mass % of the total components contained in the void-containing layer A. When the content of the polypropylene resin is 3 mass % or more and 30 mass % or less, voids can be formed to obtain sufficient lightness and cushioning properties, and excellent film forming properties are achieved.

As the polysilicone resin used in the present invention, polysilicone polymers can be listed, such as partially cross-linked polysilicone polymers (i.e., polysilicone synthetic resins belonging to the narrow sense of polysilicone resins) and linear polysilicone polymers (i.e., polysilicone rubbers). Specifically, methyl polysilicone resins, methyl phenyl polysilicone resins, phenyl polysilicone resins, alkyd-modified polysilicone resins, polyester-modified polysilicone resins, urethane-modified polysilicone resins, epoxy-modified polysilicone resins, and acrylic-modified polysilicone resins can be listed. From the viewpoint of being able to withstand the extrusion temperature of the polyester resin as the base resin and from the viewpoint of suppressing step contamination due to sublimation, a polysilicone resin having a cross-linked structure is preferred.

The method of adding the silicone resin is not particularly limited, but the silicone resin in powder or granular form may be directly added by dry blending with the base resin. Alternatively, a master batch may be prepared by pre-melting polyester resin, polypropylene resin, and silicone resin.

From the viewpoint of void appearance, film forming properties, and manufacturing cost, the amount of silicone resin added is preferably 1 ppm or more and 10,000 ppm or less, and more preferably 100 ppm or more and 8,000 ppm or less, relative to the total mass of the void-containing layer A. By setting it to 1 ppm or more, the surface density can be effectively reduced. By setting it to 10,000 ppm or less, the contamination of the process and the deterioration of the film forming properties can be suppressed. Thus, the manufacturing cost can be suppressed.

The content of polydimethylsiloxane derived from polysilicone resin can be obtained by NMR (nuclear magnetic resonance) method. From the viewpoint of void appearance, film forming property, and manufacturing cost, the content of polydimethylsiloxane derived from polysilicone resin is preferably 1 ppm to 2500 ppm, more preferably 100 ppm to 2400 ppm, and further preferably 100 ppm to 1400 ppm, relative to the total mass of layer A containing voids. By setting it to 1 ppm or more, the surface density can be effectively reduced. By setting it to 2500 ppm or less, the contamination of the process and the deterioration of the film forming property can be suppressed. Thus, the manufacturing cost can be suppressed. Since polysilicone has a cross-linked structure and is insoluble in a solvent, the content of polydimethylsiloxane in the polysilicone can be determined by using the NMR measurement method described later, which can be used as an indicator of the content of the polysilicone in the layer A containing voids.

The content of polydimethylsiloxane in the silicone resin contained in the void-containing layer A determined by the NMR method is preferably 0.005 mass % or more and 2.000 mass % or less, more preferably 0.010 mass % or more and 1.800 mass % or less, and further preferably 0.100 mass % or more and 0.800 mass % or less, relative to 100 mass % of the polypropylene resin in the void-containing layer A. By containing 0.005 mass % or more of polydimethylsiloxane relative to 100 mass % of the polypropylene resin, the heat resistance of the polypropylene resin can be improved, and the void can be effectively formed without being damaged during stretching. By setting the content of polydimethylsiloxane to 2.000 mass % or less, the deterioration of film forming properties can be suppressed.

By containing a small amount of silicone resin in the void-containing layer A, heat resistance can be imparted to the polypropylene resin. Therefore, during material recycling, thermal degradation of the polypropylene resin can be suppressed and void appearance can be maintained. Even as a polyester-based adhesive film containing voids, the voids become difficult to be destroyed in a high temperature environment, so the thickness unevenness caused by the local destruction of the polypropylene resin as a void appearance agent can be suppressed.

Furthermore, as long as it is within the scope that does not harm the purpose of the present invention, it may also contain an immiscible resin other than polypropylene resin. With respect to 100 mass% of the immiscible resin in the layer A containing the voids, it is preferred that 90 mass% or more of the polypropylene resin is contained, more preferably 95 mass% or more, and most preferably 100 mass%. In addition, from the viewpoint of whiteness and void appearance, it is preferred that the dispersant does not contain polyethylene glycol, surfactant, etc.

Furthermore, within the scope of not impairing the purpose of the present invention, these polyester resins or polypropylene resins may also contain a small amount of other polymers or antioxidants, thermal stabilizers, matting agents, pigments, ultraviolet absorbers, fluorescent whitening agents, plasticizers or other additives. In particular, in order to inhibit the oxidative degradation of polypropylene resin, it is preferred to contain an antioxidant or a thermal stabilizer. Although the types of antioxidants and thermal stabilizers are not particularly limited, for example, hindered phenol series, phosphorus series, hindered amine series, etc. can be listed, which can be used alone or in combination. As for the added amount, it is preferably more than 1 ppm and less than 50000 ppm relative to the total mass of the layer A containing voids. Furthermore, in the present invention, even if no fluorescent whitening agent is added to the layer A containing voids, excellent whiteness can be ensured.

In the present invention, in order to improve the hiding power and whiteness of the polyester-based easy-to-bond film containing voids, inorganic pigments can be included in the polyester resin or the polypropylene resin as needed. As inorganic pigments, there can be listed: silicon dioxide, kaolinite, talc, calcium carbonate, zeolite, aluminum oxide, barium sulfate, titanium oxide, zinc sulfide, etc. Among these, titanium oxide, calcium carbonate, and barium sulfate are preferred from the perspective of hiding power and whiteness. Furthermore, these inorganic pigments can be used alone, or two or more kinds can be used in combination. These inorganic pigments can be contained in the polyester-based easy-to-bond film containing voids by being added to the polyester resin or the polypropylene resin in advance.

Although there is no particular limitation on the method of mixing the inorganic pigment with the polyester resin or the polypropylene resin, the following methods can be cited. That is, the following methods can be cited: a method of dry-blending the polyester resin and the polypropylene resin and then directly feeding the mixture into a film-making machine; and a method of dry-blending the polyester resin and the polypropylene resin and then melt-blending the mixture using various common mixers to form a masterbatch.

The void-containing polyester easy-adhesive film of the present invention has a laminated structure in which a first coating layer B1, a void-containing layer A, and a second coating layer B2 are sequentially laminated. The first coating layer B1 contains a polyester resin containing an inorganic pigment, the void-containing layer A contains voids inside, and the second coating layer B2 contains a polyester resin containing an inorganic pigment. Here, when the void-containing layer A containing a polypropylene resin is exposed on the surface, the partially exposed polypropylene dispersed particles cause step contamination such as roller contamination. Furthermore, the void-containing layer A is coated by the first coating layer B1 containing an inorganic pigment and the second coating layer B2, thereby having the effect of preventing the decrease of whiteness.

From the viewpoint of void appearance and suppression of exposure of polypropylene resin and polysilicone resin, the ratio of the total thickness of the first coating layer B1 and the thickness of the second coating layer B2 to the total thickness of the first coating layer B1, the thickness of the layer A containing voids, and the thickness of the second coating layer B2 (hereinafter also referred to as the layer ratio) is preferably 6% to 40%, and more preferably 8% to 30%. When the layer ratio is 6% to 40%, exposure of polypropylene resin and polysilicone resin can be suppressed, and the contact angle of water and the contact angle of diiodomethane can be reduced. Furthermore, when the layer ratio is 6% to 40%, it is easy to form voids for obtaining sufficient lightness and cushioning properties.

As the inorganic pigments contained in the first coating layer B1 and the second coating layer B2, there can be listed: silicon dioxide, kaolin, talc, calcium carbonate, zeolite, aluminum oxide, barium sulfate, titanium oxide and zinc sulfide. Among these, from the perspective of shielding and whiteness, titanium oxide, calcium carbonate and barium sulfate are preferred, and titanium oxide is particularly preferred. Furthermore, these inorganic pigments can be used alone or in combination of two or more. These pigments can be contained in the film by being added to the polyester resin in advance.

The amount of the inorganic pigment added to the first coating layer B1 is not particularly limited, but is preferably 1% to 35% by mass, and more preferably 2% to 30% by mass, relative to 100% by mass of all the components constituting the first coating layer B1. When the amount of the inorganic pigment added is 1% to 35% by mass, the shielding property and whiteness of the polyester-based adhesive film containing voids are easily improved, and the film-forming property and mechanical strength of the polyester-based adhesive film containing voids can be improved.

The amount of inorganic pigment added in the second coating layer B2 is not particularly limited, and is preferably the same as the amount of inorganic pigment added in the first coating layer B1. The first coating layer B1 and the second coating layer B2 are preferably substantially the same in composition, thickness, etc. That is, the laminated structure of the first coating layer B1/the layer A containing voids/the second coating layer B2 is preferably a two-type three-layer structure. Furthermore, it is preferred that a functional easy-to-bond layer is laminated on the first coating layer B1, and it is also preferred that a functional easy-to-bond layer that is the same as the functional easy-to-bond layer on the first coating layer B1 or that is different in composition, thickness, etc. is laminated on the second coating layer B2.

The inorganic pigment contained in the first coating layer B1 and the second coating layer B2 is preferably in the form of particles, and the average particle size of the particles is preferably 0.1 μm to 4.0 μm, and particularly preferably 0.3 μm to 1.5 μm. Specifically, preferred are white pigments in the form of particles such as titanium oxide, barium sulfate, calcium carbonate, zinc sulfide, etc., which may also be mixed. Furthermore, the film may also contain generally contained inorganic particles such as silicon dioxide, aluminum oxide, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconium oxide, tungsten oxide, lithium fluoride, calcium fluoride, calcium sulfate, etc.

As long as the purpose of the present invention is met, the shape of the particles is not particularly limited, and spherical particles or amorphous non-spherical particles can be used. The particle size of amorphous particles can be calculated as an equivalent circle diameter.

Furthermore, in the polyester-based easy-to-adhesive film containing voids of the present invention, in order to improve the coating and adhesion of printing inks, coating agents, etc., it is preferred to provide a functional easy-to-adhesive layer having both easy adhesion and antistatic properties on at least one side thereof. As the resin contained in the composition constituting the functional easy-to-adhesive layer, polyester resins, urethane resins having a polycarbonate structure, polyester urethane resins, acrylic resins, and other compounds commonly disclosed as means for improving the adhesion of polyester-based films can be applied. In order to facilitate so-called in-line coating, the resin is preferably water-soluble and water-dispersible.

In the present invention, a blocked isocyanate as a crosslinking agent may be added to the composition constituting the functional easy-adhesion layer. Blocked isocyanates with three or more functional groups are preferred, and blocked isocyanates with four or more functional groups are particularly preferred. By these, when the composition described later contains an antistatic agent, the antistatic property of the surface of the easy-adhesion layer can be controlled, and the back transfer property of the antistatic agent can be suppressed.

In order to impart water solubility or water dispersibility to the blocked isocyanate of the present invention, a hydrophilic group may be introduced into the polyisocyanate as a precursor. Examples of the hydrophilic group include (1) quaternary ammonium salts of dialkylamino alcohols, quaternary ammonium salts of dialkylaminoalkylamines, etc.; (2) sulfonates, carboxylates, phosphates, etc.; (3) polyethylene glycol and polypropylene glycol, etc., with one end blocked by an alkyl group. When a hydrophilic site is introduced, it will become (1) cationic; (2) anionic; (3) non-ionic. Among them, since other water-soluble resins are mostly anionic, anionic and non-ionic resins that are easily miscible are preferred. Furthermore, since anionic resins have excellent solubility with other resins and non-ionic resins do not have ionic hydrophilic groups, they are also better for improving moisture and heat resistance.

As the anionic hydrophilic group, a hydroxyl group for introducing polyisocyanate or a carboxylic acid group for imparting hydrophilicity is preferred. For example, glycolic acid, lactic acid, tartaric acid, citric acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypivalic acid, dihydroxymethylacetic acid, dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, and polycaprolactone having a carboxylic acid group can be cited. In order to neutralize the carboxylic acid group, an organic amine compound is preferred. For example, there can be mentioned ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, ethylenediamine and other linear or branched primary, secondary or tertiary amines having 1 to 20 carbon atoms, morpholine, N-alkylmorpholine, cyclic amines such as pyridine, monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, triethanolamine and other amines containing a hydroxyl group.

The number of repeating units of ethylene oxide and/or propylene oxide of polyethylene glycol or polypropylene glycol with one end blocked by an alkyl group as a non-ionic hydrophilic group is preferably 3 to 50, more preferably 5 to 30. When the number of repeating units is small, the miscibility with the resin becomes poor and the haze increases; when the number of repeating units is large, the adhesion under high temperature and high humidity is sometimes reduced. In order to improve the water dispersibility of the blocked isocyanate of the present invention, non-ionic, anionic, cationic, or amphoteric surfactants can be added. For example, the following can be cited: non-ionic systems such as polyethylene glycol and polyol fatty acid esters; anionic systems such as fatty acid salts, alkyl sulfates, alkylbenzene sulfonates, sulfosuccinates, and alkyl phosphates; cationic systems such as alkylamine salts and alkyl betaines; surfactants such as carboxylic acid amine salts, sulfonic acid amine salts, and sulfate ester salts, etc.

It is preferred to add an antistatic agent to the composition constituting the functional easy-adhesion layer. The antistatic agent is preferably capable of inhibiting the transfer to other objects in contact or the back side of the film itself. For example, the functional groups include: non-ionic systems such as sorbitan type, ether type, ester type, sorbitol type, glucose type, etc.; cationic systems such as quaternary ammonium salt type, quaternary ammonium resin type, imidazoline, Archebel type, Solomine A type, etc.; anionic systems such as alkyl sulfate type, alkyl phosphate type, phosphate salt type, sulfate salt type, etc.; and amphoteric surfactant types or polymer types such as betaine type, amino acid type, aminosulfate type, etc.

In the above antistatic agent, the counter ion of the quaternary ammonium salt group is not particularly limited as long as it is an anionic compound. It is preferably selected from halogen ions, monohalogenated alkyl ions or polyhalogenated alkyl ions, nitrate ions, sulfate ions, alkyl sulfate ions, sulfonate ions or alkyl sulfonate ions. Ethyl sulfate is preferred in order to obtain the stability of the surface resistivity, coating stability, ink adhesion and inhibit the migration of the antistatic agent to other objects or the back.

(Polycarbonate urethane resin) In the present invention, the urethane resin having a polycarbonate structure suitably contained in the composition constituting the functional easy-to-bond layer preferably has at least a urethane bond partial structure derived from a polycarbonate polyol component and a polyisocyanate component, and further contains a chain extender as needed. Furthermore, it is preferred to appropriately introduce a polyisocyanate having a branched structure by making the number of terminal functional groups of any of the raw material components mentioned above as constituting the molecular chain to be 3 or more, thereby forming a molecular chain structure on a branch after synthesis and polymerization.

In the case of the urethane resin having a polycarbonate structure in the present invention and having a branched structure, the lower limit of the number of terminal functional groups in the molecular chain is preferably 3, and more preferably 4, according to the branched structure. If it is 3 or more, the anti-blocking property during water adhesion is improved and it is preferred. In the urethane resin having a polycarbonate structure in the present invention, due to its branched structure, the upper limit of the number of terminal functional groups in the molecular chain is preferably 6. If it is 6 or less, the resin can be stably dispersed in an aqueous solution and it is preferred.

In the present invention, the polycarbonate polyol component used for polymerizing the urethane resin having a polycarbonate structure preferably includes an aliphatic polycarbonate polyol having excellent heat resistance and hydrolysis resistance. Examples of the aliphatic polycarbonate polyol include aliphatic polycarbonate diols and aliphatic polycarbonate triols. The aliphatic polycarbonate diols can be suitably used. Examples of the aliphatic polycarbonate diols used for polymerizing the urethane resin having a polycarbonate structure in the present invention include aliphatic polycarbonate diols obtained by reacting one or more diols such as ethylene glycol, propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene.

The functional adhesive layer may contain lubricant particles in order to impart slip or roughness, ink absorption, etc. to the surface. The particles may be inorganic particles or organic particles. Although not particularly limited, examples thereof include: (1) silicon dioxide, kaolin, talc, light calcium carbonate, heavy calcium carbonate, zeolite, aluminum oxide, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium oxide, titanium dioxide, aluminum silicate, diatomaceous earth, etc. (1) inorganic particles such as calcium silicate, aluminum hydroxide, calcium carbonate, magnesium carbonate, calcium phosphate, magnesium hydroxide, and barium sulfate; (2) organic particles such as acrylic acid or methacrylic acid, vinyl chloride, vinyl acetate, nylon, styrene/acrylic acid, styrene/butadiene, polystyrene/acrylic acid, polystyrene/isoprene, methyl methacrylate/butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, and polyester. In order to impart appropriate slip to the adhesive layer, silicon dioxide can be particularly suitably used.

The average particle size of the particles is preferably 0.1 μm to 2.4 μm, more preferably 0.3 μm to 2.0 μm. If the average particle size of the particles is 0.1 μm or less, the glossiness of the film surface may increase. On the contrary, if the average particle size of the particles exceeds 2.4 μm, the particles fall off from the functional easy-bonding layer, which tends to cause powder falling.

The content of the aforementioned particles can be added within a range that does not impair the efficacy of the present invention. However, in order to prevent the particles from falling off from the functional easy-bonding layer and causing powder falling, the content of the particles is relative to the solid content of the functional easy-bonding layer as a whole. The solid content of the particles is preferably 0 mass % to 70.0 mass %, more preferably 0 mass % to 60.0 mass %, and further preferably 0 mass % to 55.0 mass %.

As long as the purpose of the present invention is met, the shape of the particles is not particularly limited, and spherical particles or amorphous non-spherical particles can be used. The particle size of amorphous particles can be calculated by calculating the equivalent diameter of a circle.

(Polyester resin) The polyester resin that can be suitably contained in the composition forming the functional easy-to-bond layer in the present invention can be a linear polyester resin, and more preferably a polyester resin composed of a dicarboxylic acid and a diol having a branched structure. The dicarboxylic acid mentioned here, in addition to terephthalic acid, isophthalic acid or 2,6-naphthalene dicarboxylic acid, can be listed as the main component: aliphatic dicarboxylic acids such as adipic acid and sebacic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid. Furthermore, the so-called branched diol is a diol having a branched alkyl group, for example, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol and 2,2-di-n-hexyl-1,3-propanediol, etc.

The above-mentioned polyester resin can be said to be a branched diol component as the above-mentioned better embodiment, preferably contained in the total diol component at a ratio of 10 mol% or more, preferably 20 mol% or more. If it is 10 mol% or more, the crystallinity will not become too high, and the adhesion of the easy-adhesion layer will be better. The upper limit of the diol component in the total diol component is preferably 80 mol% or less, and more preferably 70 mol%. If it is 80 mol% or less, the concentration of oligomers as by-products is suppressed, and the transparency of the easy-adhesion layer is good and better. As a diol component other than the above-mentioned compounds, ethylene glycol is the best. If it is a small amount, diethylene glycol, propylene glycol, butanediol, hexanediol or 1,4-cyclohexanedimethanol can also be used.

Regarding the dicarboxylic acid as a component of the above polyester resin, terephthalic acid or isophthalic acid is the most preferable. In addition to the above dicarboxylic acids, in order to impart water dispersibility to the copolymerized polyester resin, it is preferred to copolymerize 5-sulfoisophthalic acid in a range of 1 mol% to 10 mol%, for example, 5-sulfoisophthalic acid dimethyl ester, etc. A polyester resin containing a dicarboxylic acid having a naphthalene skeleton can also be used, but in order to suppress the decrease in adhesion to UV ink, the ratio of the amount of the dicarboxylic acid having a naphthalene skeleton is preferably less than 5 mol% in the total carboxylic acid component, and it is not necessary to use it.

As a constituent component of the polyester resin, a triol or a tricarboxylic acid may be contained to the extent that the properties of the polyester resin are not impaired.

The above-mentioned polyester resin may also contain polar groups other than carboxyl groups. For example, sulfonate metal salt groups, phosphoric acid groups, etc. may be listed, and these may contain one or more. As a method for introducing sulfonate metal salt groups, the following method may be listed: using dicarboxylic acids or diols containing sulfonate metal salt groups such as metal salts of 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-[4-sulfophenoxy]isophthalic acid, or metal salts of 2-sulfo-1,4-butanediol, 2,5-dimethyl-3-sulfo-2,5-hexanediol, etc. in an amount of less than 10 mol %, preferably less than 7 mol %, and more preferably less than 5 mol % of the total of polycarboxylic acid components or polyol components. If the polycarboxylic acid component or the polyol component exceeds 10 mol%, the hydrolysis resistance of the resin itself and the water resistance of the coating film tend to decrease.

As a means to improve the adhesion, other disclosed compounds can also be applied and added. In order to improve the adhesion durability of the functional easy-adhesion layer, even other crosslinking agents can further improve the adhesion under high temperature and high humidity. As specific crosslinking agents, urea series, epoxy series, melamine series, oxazoline series, carbodiimide series, etc. can be listed. Furthermore, in order to promote the crosslinking reaction, a catalyst can be used appropriately as needed.

(Additives) In the functional bonding layer of the present invention, known additives may be added within the scope that does not impair the efficacy of the present invention, such as surfactants, pH adjusters, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, nucleating agents, etc.

As a method for providing a functional easy-to-adhesive layer, commonly used methods such as gravure coating, kiss coating, dip coating, spray coating, curtain coating, air knife coating, blade coating, reverse roll coating, etc. can be applied. As a coating stage, any method can be used, such as a method of coating before film stretching, a method of coating after longitudinal stretching, and a method of coating on the film surface after stretching treatment.

The manufacturing method of the polyester-based easy-to-bond film containing voids in the present invention is described. For example, after drying, mixed particles composed of a composition including a polyester resin, a polypropylene resin, and a polysilicone resin are melt-extruded into a sheet from a T-shaped nozzle, and then closely contacted to a casting drum by an electrostatic application method, and then cooled and solidified to obtain an unstretched film. Subsequently, the unstretched film is stretched and oriented. The most commonly used sequential biaxial stretching method, especially the method of stretching the unstretched film longitudinally in the length direction and then stretching it transversely in the width direction, is described as an example. First, in the longitudinal stretching step along the length direction, the film is heated and stretched between two or more rollers with different circumferential speeds to 2.5 to 5.0 times. The heating means at this time may be a method using a heating roller, a method using a non-contact heating medium, or a combination of these. At this time, it is preferred to set the film temperature to a range of (Tg-10°C) to (Tg+50°C). Next, the uniaxially stretched film is coated by reverse gravure coating in a wet (WET) coating amount of 1 g/ ^m2 to 20 g/ ^m2 , and then introduced into a tenter, and stretched to 2.5 to 5 times in the width direction at a temperature of (Tg-10°C) to Tm-10°C or less, thereby obtaining a biaxially stretched film. Here, Tg is the glass transition temperature of the polyester resin, and Tm is the melting point of the polyester. Furthermore, the film obtained by the above method is preferably subjected to heat treatment as needed, and the treatment temperature is preferably in the range of (Tm-60°C) to Tm.

Furthermore, the polyester-based adhesive film containing voids in the present invention may contain recycled raw materials composed of the polyester-based adhesive film containing voids in the layer A containing voids. The so-called used polyester-based adhesive film containing voids in the present invention is film scraps generated by ear or break problems in the film making step or things collected from the city. Even when recycled raw materials are added to the layer A containing voids, as long as the recycled raw materials of the polyester-based adhesive film containing voids in the present invention are used, a small amount of polysilicone resin is added to the polypropylene resin, so that the void appearance can be maintained. Thus, the polyester adhesive film containing voids can obtain sufficient lightness and cushioning properties, and can obtain a polyester adhesive film containing voids with excellent shielding properties and whiteness. Especially in today's era of seeking to cope with environmental loads, the amount of recycled raw materials added is increased compared to the past because the used polyester adhesive film containing voids is recycled. However, as long as polysilicone is added, the void appearance can be maintained even when the amount added is increased.

The amount of recycled raw materials added is preferably 5% to 70% by mass relative to 100% by mass of the total mass of the layer A containing voids, from the viewpoint of reducing raw material costs, whiteness, and film-forming properties. Also, even if the first coating layer B1 or the second coating layer B2 contains recycled raw materials, it is not a problem. However, from the viewpoint of deterioration of whiteness and exposure of polypropylene resin in the recycled raw materials, it is better not to contain them.

The apparent density of the polyester-based adhesive film containing voids in the present invention is preferably 0.80 g/cm ³ or more and 1.20 g/cm ³ or less, and more preferably 0.80 g/cm ³ or more and 1.10 g/cm ³ or less. When the apparent density is 0.80 g/cm ³ or more and 1.20 g/cm ³ or less, the total voids in the polyester-based adhesive film containing voids become appropriate, and it becomes easy to handle during post-processing such as printing or use. Furthermore, when the apparent density is 0.80 g/cm ³ or more and 1.20 g/cm ³ or less, sufficient lightness and cushioning properties can be obtained. In particular, the polyester-based adhesive film containing voids in the present invention can have excellent lightness, film-forming properties, shielding properties and whiteness even if the surface density is 0.80 g/cm ³ to 1.10 g/cm ³ by containing a trace amount of polysilicone resin.

Note that the apparent density is a value measured by the measurement method described in the evaluation method described later.

The polyester-based easy-to-bond film containing voids in the present invention preferably has a total light transmittance of 30% or less, and more preferably 25% or less. When the total light transmittance is 30% or less, sufficient shielding can be obtained. For example, when used for labels, the image printed on the label becomes clear. In addition, the total light transmittance is a value converted to a thickness of 50 μm obtained by the measurement method described in the evaluation method described later.

The color tone b value of the polyester-based adhesive film containing voids in the present invention is preferably 4.0 or less, more preferably 3.0 or less, and particularly preferably 1.5 or less. When the color tone b value is greater than 4.0, the whiteness is poor, and when it is made into a label, the clarity during printing may be reduced, which may damage the product value.

The thickness of the void-containing polyester-based adhesive film of the present invention is arbitrary, but is preferably 20 μm to 300 μm.

In the present invention, the remaining area of the functional easy-adhesion layer and the curable ink printing layer is preferably 90% or more of the entirety, more preferably 99% or more, and of course, 100% is the most preferable, according to the evaluation method described below.

The functional bonding layer preferably contains an antistatic agent as described above, and preferably has a surface resistivity of 1.0×10 ¹³ Ω/sq or less, more preferably 1.0×10 ¹² Ω/sq or less, and particularly preferably 1.0×10 ¹¹ Ω/sq or less. The lower limit is not particularly set, but may be 1.0×10 ⁵ Ω/sq or more, and may be 1.0×10 ⁶ Ω/sq or more.

The number of pinhole shrinkages of the functional adhesive layer as determined by the evaluation method described below is preferably 5/ ^m2 or less. The fewer the number of pinhole shrinkages, the better, and the best number is of course 0/ ^m2 .

The water contact angle of the functional easy-adhesion layer of the polyester-based easy-adhesion film containing voids of the present invention after heating at 150°C for 30 minutes is preferably 50° to 90°, and more preferably 55° to 85°. When the water contact angle is below 90°, the polyester-based easy-adhesion film containing voids can suppress coating or printing omissions in the processing step. The water contact angle is preferably small, but when a polyester resin is included, it is preferably 50° or more. Furthermore, the diiodomethane contact angle achieved by the functional easy-adhesion layer after heating at 150°C for 30 minutes is preferably 10° to 60°. When the contact angle of diiodomethane is 60° or less, the polyester-based adhesive film containing voids can suppress coating or printing omissions in the processing step. When the contact angle of diiodomethane is 10° or more, the polyester-based adhesive film containing voids can improve the adhesion between the coating and the original roll in the processing step.

The water contact angle of the functional easy-bonding layer of the polyester-based easy-bonding film containing voids of the present invention at 85°C, 85%RH, and after 72 hours is preferably 46° to 90°, and more preferably 50° to 85°. When the water contact angle is below 90°, the polyester-based easy-bonding film containing voids can suppress coating or printing leaks when processed after long-term warehouse storage. The water contact angle is preferably small, but when a polyester resin is included, it is preferably 46° or more. Furthermore, the contact angle of the functional easy-bonding layer with diiodomethane at 85°C, 85%RH, and after 72 hours is preferably 10° to 60°. When the contact angle of diiodomethane is 60° or less, the polyester adhesive film containing voids can suppress coating or printing omissions during processing after long-term storage. When the contact angle of diiodomethane is 10° or more, the polyester adhesive film containing voids can improve the adhesion between the coating and the original roll in the processing step.

As described above, the void-containing polyester-based adhesive film of the present invention can suppress the thermal degradation of polypropylene resin and maintain the void appearance in the processing step by including a trace amount of polysilicone resin in the void-containing layer A. Therefore, the void-containing polyester-based adhesive film of the present invention can have excellent lightness, film-forming properties, shielding properties and whiteness even if the apparent density is 0.80 g/cm ³ to 1.20 g/cm ³ .

Therefore, the polyester-based easy-to-bond film containing voids of the present invention can be suitably used as a base material such as a release film used in the manufacture of labels, cards, packaging materials, polarizing plates, or laminated ceramic capacitors. [Example]

The present invention is specifically described with the following examples. In addition, the present invention is not limited to the examples described below. In addition, each evaluation item in the examples and comparative examples is measured by the following method. (1) Film-forming property Under the film-forming conditions described in the preparation of the polyester-based easy-to-bond film containing voids described later, the number of breaks during the preparation with a film-forming time of 2 hours is evaluated as described below. ○: No break △: 1 to 3 breaks ×: 4 or more breaks, unable to form a film

(2) Apparent density Cut the polyester adhesive film containing voids into four square pieces of 5.0 cm square, overlap the four pieces and use a micrometer to obtain the four significant figures. Change the position of the total thickness and measure 10 points to obtain the average thickness of the four overlapping pieces. Divide the average value by 4 and round it to three significant figures to obtain the average thickness of each piece (t: μm). Use an automatic plate balance to measure the mass (w: g) of four pieces of the same sample to obtain the apparent density using the following formula. In addition, the apparent density is rounded to three significant figures. Apparent density (g/cm ³ ) = w/(5.0 × 5.0 × t × 10 ^-4 × 4)

(3) Total light transmittance Measured using a haze meter (manufactured by Nippon Denshoku Industries; NDH5000) and converted to a value per film thickness of 50 μm. The same measurement was performed three times and the arithmetic mean value was adopted.

(4) Hue b value The hue b value is measured using a colorimeter (ZE6000) manufactured by Nippon Denshoku Co., Ltd. in accordance with JIS-8722. The smaller the hue b value, the higher the whiteness and the weaker the yellowness.

(5) Water contact angle after heating at 150°C for 30 minutes After heating the sample at 150°C for 30 minutes in a gear oven, the contact angle between the surface of the functional adhesive layer and distilled water dripped for 1 minute was measured using a FACE contact angle meter (manufactured by Kyowa Interface Chemical Co., Ltd.; CA-X model). In addition, five measurements were performed for each sample, and the average of the three measured values after removing the maximum and minimum values was set as the contact angle.

(6) Diiodomethane contact angle after heating at 150°C for 30 minutes After heating the sample at 150°C for 30 minutes in a gear oven, the contact angle between the surface of the functional adhesive layer and diiodomethane after dripping for 1 minute was measured using a FACE contact angle meter (manufactured by Kyowa Interface Chemical Co., Ltd.; CA-X model). In addition, five measurements were performed for each sample, and the average of the three measured values after removing the maximum and minimum values was set as the contact angle.

(7) Water contact angle after 72 hours at 85°C and 85%RH After placing the sample in a constant temperature and humidity chamber at 85°C and 85%RH for 72 hours, the contact angle between the surface of the functional adhesive layer and distilled water dripped for 1 minute was measured using a FACE contact angle meter (manufactured by Kyowa Interface Chemicals Co., Ltd.; CA-X model). In addition, five measurements were performed on each sample, and the average of the three measured values after removing the maximum and minimum values was set as the contact angle.

(8) Diiodomethane contact angle after 72 hours at 85°C and 85% RH After placing the sample in a constant temperature and humidity chamber at 85°C and 85% RH for 72 hours, the contact angle between the surface of the functional adhesive layer and diiodomethane dripped one minute after was measured using a FACE contact angle meter (manufactured by Kyowa Interface Chemicals Co., Ltd.; CA-X model). In addition, five measurements were performed on each sample, and the average of the three measured values after removing the maximum and minimum values was set as the contact angle.

(9) Determination of polydimethylsiloxane content 0.5 ml of TCE (tetrachloroethane)-d was added to 0.1 ml of CDC13 (deuterated chloroform)/HFIP-d (deuterated hexafluoroisopropyl alcohol) (1/1 volume ratio) and dissolved at 130°C. The solution was subjected to H-NMR measurement at 120°C, and the mass ratio of polydimethylsiloxane was calculated from the ratio of the integral values of the obtained components. The peak of polydimethylsiloxane is the peak detected near 0.2 ppm using the NMR spectrum. The content of polydimethylsiloxane in layer A containing voids was calculated using the layer ratio. Since polysiloxane resin is cross-linked and contains a large amount of insoluble components, it is difficult to quantify the amount of addition. However, the polydimethylsiloxane as a soluble component in polysiloxane resin can be quantified by using the above method. It was confirmed that the amount of silicone resin added is related to the content of polydimethylsiloxane.

(10) Determination of the mass ratio of polypropylene resin content to polydimethylsiloxane content H-NMR was performed in the same manner as above, and the mass ratio was calculated from the ratio of the integrated values of the peaks of polypropylene resin and polydimethylsiloxane in the obtained NMR spectrum.

Adhesion with UV ink On the functional easy-adhesive layer of the polyester-based easy-adhesive film containing voids, UV ink [T&K TOKA (Co., Ltd.); trade name "BEST CURE (Registered Trademark) UV161 Blue S"] was printed using a printer [Ming Seisakusho (Co., Ltd.); trade name "RI TESTER"], and then the film coated with the ink layer was irradiated with 40mJ/ ^cm2 of ultraviolet light using a high-pressure mercury lamp to cure the ultraviolet curing ink. Then, a cellophane tape (CT405AP-24) manufactured by Michelbon was cut into 24mm wide and 50mm long pieces, and the cellophane tape was completely attached to the surface of the ink layer using a handheld rubber roller in a manner that prevented air from entering. Then, the cellophane tape was torn off vertically, and the remaining area of the printed layer was observed in an area of 24 mm x 50 mm, and judged according to the following criteria: ○: The remaining area of the printed layer is 99% or more of the whole △: The remaining area of the printed layer is 90% or more but less than 99% of the whole ×: The remaining area of the printed layer is less than 90% of the whole In the present invention, 90% or more is considered acceptable.

(12) Antistatic property (surface resistivity) Three 5.0 cm square pieces of the polyester adhesive film containing voids were cut out as samples. The surface resistivity of the three pieces was measured using a surface resistivity meter (Hiresta MCP-HT800 manufactured by Nitto Seiko Analytech) at an applied voltage of 500 V, 23°C, and 65% humidity in accordance with JIS K6911, and the average value was taken.

(13) Evaluation of shrinkage in appearance Ten rectangular films of 300 mm in the length direction (also called longitudinal direction or machine direction) and 210 mm in the width direction of the polyester-based easy-adhesion film containing voids were randomly cut out, and the functional easy-adhesion layer was visually observed under a 3-wavelength LED light. The number of pinhole-like shrinkages was counted and converted into the number per ^1m2 for evaluation. ○: The number of pinhole-like shrinkages per ^1m2 of film was 0 or more and 5 or less △: The number of pinhole-like shrinkages per ^1m2 of film was 6 or more and 10 or less ×: The number of pinhole-like shrinkages per ^1m2 of film was more than 10. In the present invention, 5 or less was considered acceptable.

(Example 1) [Manufacturing of titanium oxide master pellets (M1)] 50% by mass of tantalum-type titanium dioxide having an average particle size of 0.3 μm (electron microscopy) was mixed with 50% by mass of polyethylene terephthalate resin having an ultimate viscosity of 0.62 dl/g. Then, the mixture was supplied to an exhaust double-spindle extruder for kneading to manufacture master pellets (M1) containing titanium oxide.

[Manufacturing of Silicone Resin S] Thermosetting silicone resin (KS-774 manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with a solvent, and 3 parts by mass of a catalyst (CAT-PL-3 manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 parts by mass of the silicone resin, and heated at 150°C for 60 seconds. After heating, the cured silicone resin was powdered to obtain silicone resin S.

[Manufacturing of unstretched film] 93% by mass of polyethylene terephthalate resin with an ultimate viscosity of 0.62 dl/g, 6.92% by mass of polypropylene resin with MFR = 2.5 g/10 minutes, Mw = 320000, Mw/Mn = 4.0, and heat deformation temperature = 92°C, and 800 ppm of polysilicone resin S were mixed. The mixture was vacuum dried to prepare the raw material of layer A containing voids. On the other hand, 30% by mass of the masterbatch particles (M1) containing titanium oxide and 70% by mass of polyethylene terephthalate resin with an ultimate viscosity of 0.62 dl/g were mixed in particles. Furthermore, the mixture is vacuum dried to serve as the raw material for the first coating layer B1 and the second coating layer B2. These raw materials are supplied to respective extruders, melted at 285°C, and the void-containing layer A, the first coating layer B1, and the second coating layer B2 are layered in the order of B1/A/B2. The layered bodies are joined using a feed block in a thickness ratio of 10/80/10. The joined bodies are extruded from a T-die onto a cooling drum adjusted to 30°C, thereby producing two types of three-layer unstretched films.

[Functional easy-adhesion layer] (Cationic antistatic agent A) Use 116g of N,N-dimethyl-1,3-propylenediamine and 285g of stearic acid with a carbon number of 17 to carry out an esterification reaction at 100°C and nitrogen atmosphere for 10 hours, add tetrahydrofuran as a quaternary solvent, add a predetermined amount of dimethylsulfuric acid to the target amine, and react at 70°C for about 10 hours. After the reaction, the solvent is distilled off by reducing pressure, and isopropyl alcohol is added to adjust the solid content to the desired concentration, thereby obtaining an isopropyl alcohol solution of cationic antistatic agent A with quaternary ammonium ethyl sulfate.

(Polymerization of Urethane Resin B Having Polycarbonate Structure) In a four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silicone drying tube and a thermometer, 22 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 20 parts by mass of polyethylene glycol monomethyl ether having a number average molecular weight of 700, 53 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2100, 5 parts by mass of neopentyl glycol and 84.00 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere to confirm that the reaction solution reached the predetermined amine equivalent. Next, 16 parts by weight of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals; DURANATE (registered trademark) TPA; trifunctional) using hexamethylene diisocyanate as a raw material was added, and stirred at 75°C for 1 hour under a nitrogen atmosphere to confirm that the reaction solution reached the predetermined amine equivalent. Thereafter, the reaction solution temperature was lowered to 50°C, and 7 parts by weight of methyl ethyl ketoxime was added dropwise. After the reaction solution was cooled to 40°C, a polyurethane prepolymer was obtained. Next, 450 g of water was added to a reaction container equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing at 2000 min ^-1 , the polyurethane prepolymer was added for water dispersion. Then, by removing acetone and a portion of water under reduced pressure, a solution of a water-dispersible urethane resin B having a solid content of 35% by mass was prepared.

(Polymerization of closed-type isocyanate crosslinker C) In a flask equipped with a stirrer, a thermometer, and a reflux condenser, 100 parts by mass of a polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material (manufactured by Asahi Kasei Chemicals; DURANATE (registered trademark) TPA), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) were placed, and maintained at 70°C for 4 hours under a nitrogen atmosphere. Then, the temperature of the reaction solution was lowered to 50°C, and 47 parts by mass of methyl ethyl ketone oxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm that the absorption of the isocyanate group disappeared. 210 parts by weight of water was added to obtain an aqueous dispersion of oxime-blocked isocyanate crosslinker (C) with a solid content of 40% by weight. The number of functional groups of the blocked isocyanate crosslinker is 3 and the NCO equivalent is 170.

(Polymerization of Copolymerized Polyester Resin D-1) In a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 185 parts by mass of neopentyl glycol, 188 parts by mass of ethylene glycol and 0.2 parts by mass of tetra-n-butyl titanium were placed and an ester exchange reaction was carried out at a temperature ranging from 160°C to 220°C for 4 hours. Then, the temperature was raised to 255°C, the reaction system was slowly depressurized, and the reaction was carried out under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin (D-1). The obtained copolymerized polyester resin (D-1) was light yellow and transparent. The reduced viscosity of the copolymerized polyester resin (D-1) was measured to be 0.40 dl/g. The glass transition temperature obtained by DSC (Differential Scanning Calorimetry) was 65°C.

(Preparation of polyester aqueous dispersion Dw-1) In a reactor equipped with a stirrer, a thermometer, and a reflux device, 25 parts by mass of copolymerized polyester resin (D-1) and 10 parts by mass of ethylene glycol mono-n-butyl ether were placed, and the mixture was heated and stirred at 110°C to dissolve the resin. After the resin was completely dissolved, 65 parts by mass of water was slowly added to the polyester solution while stirring. After the addition, the liquid was stirred while cooling to room temperature to prepare a milky white polyester aqueous dispersion (Dw-1) with a solid content of 25% by mass.

(Example 1) The solid content in the coating liquid of the coating compound constituting the functional easy-adhesion layer is as follows. The total solid content contained in the functional easy-adhesion layer is set to 100 mass %. ・Cationic antistatic agent A: 6.2 mass% ・Urethane resin B with polycarbonate structure: 22.8 mass% ・Blocked isocyanate crosslinker C: 10.9 mass% ・Polyester resin Dw-1: 54.6 mass% ・Polysilicone surfactant: 0.4 mass% ・pH adjuster (sodium bicarbonate): 2.4 mass% The solid content mass ratio of urethane resin (B)/crosslinker (C)/polyester resin (Dw-1) is 28/12/60.

[Preparation of a polyester-based adhesive film containing voids] A polyester-based adhesive film containing voids was prepared under the following film-making conditions. That is, the obtained unstretched film was uniformly heated at 70°C using a heating roller, and longitudinally stretched to 3.4 times between two pairs of clamping rollers with different peripheral speeds. At this time, as an auxiliary heating device for the unstretched film, an infrared heater (rated at 20 W/cm) with a gold reflective film in the middle of the clamping roller was set opposite to both sides of the film (1 cm away from the film surface) to heat it. The above-mentioned coating structure was used on one side of the uniaxially stretched film obtained in this way, and the WET coating amount was 7 g/m ² by reverse gravure coating method, and then introduced into a tenter, heated at 140°C, stretched to 4.0 times in the transverse direction, fixed in width, heat treated at 235°C, and then relaxed by 3% in the width direction at 210°C, thereby obtaining a polyester-based easy-adhesion film containing voids with a film thickness of 50 μm and a functional easy-adhesion layer thickness of 0.11 g/m ^2. Table 1 shows the results of apparent density, water contact angle, diiodomethane contact angle, color tone b value, total light transmittance, and film forming properties. In addition, the gloss value of the surface of the functional easy-adhesion layer in 60-degree regular reflection is 70%, which is a functional easy-adhesion layer with excellent glossiness.

(Example 2, Example 3, Example 5) In Example 1, the raw material ratio of layer A containing voids was changed as shown in Table 1. In addition, a polyester-based easy-to-bond film containing voids was obtained by the same method as in Example 1.

(Example 4) In Example 1, the raw material ratio and layer ratio of the layer A containing voids were changed as shown in Table 1, and the coating composition of the functional easy-adhesion layer was changed to the following. A polyester-based easy-adhesion film containing voids was obtained by the same method as in Example 1. The solid components in the coating liquid of the compound constituting the functional easy-adhesion layer are shown below. The total solid components contained in the functional easy-adhesion layer are set to 100 mass %.・Colloidal silica particles (E) (average particle size: 450nm): 48.8 mass% ・Cationic antistatic agent A: 2.1 mass% ・Urethane resin B with polycarbonate structure: 12.2 mass% ・Blocked isocyanate crosslinker C: 12.2 mass% ・Polyester resin Dw-1: 24.4 mass% ・Polysilicone-based surfactant: 0.1 mass% ・pH adjuster (sodium bicarbonate): 0.2 mass% ・The mass ratio of urethane resin (B)/crosslinker (C)/polyester resin (Dw-1) is 25/25/50. Except for setting the above-mentioned functional easy-adhesion layer structure and changing the WET coating amount to 10 g/m ² , a polyester-based easy-adhesion film containing voids having a functional easy-adhesion layer thickness of 0.55 g/m ² after drying was obtained in the same manner as in Example 1. In addition, the gloss value of the surface of the functional easy-adhesion layer in 60-degree regular reflection was 9.0%, and a functional easy-adhesion layer with excellent roughness was obtained.

(Comparative Example 1) In Example 1, a polyester film containing voids was obtained by the same method as in Example 1 except that the polysilicone resin of the void-containing layer A was changed to 0 ppm, the polyethylene terephthalate resin was changed to 93.08 mass % and the functional easy-adhesion layer was not provided. In the polyester film containing voids of Comparative Example 1, since the apparent density exceeded 1.20 g/cm ³ , the lightness and cushioning properties were poor. The manufacturing cost was also high due to the large mass. Furthermore, the total light transmittance of the polyester film containing voids in Comparative Example 1 is also high, and its shielding property is poor compared to Examples 1 to 5. Since there is no functional adhesive layer, it lacks UV ink adhesion and cannot exhibit anti-static properties, causing the films to adsorb to each other due to static electricity, etc., which raises concerns about handling properties.

(Comparative Example 2) In Example 1, except that the aforementioned layer ratio is set to 0%, a polyester-based easy-to-bond film containing voids is obtained by the same method as in Example 1. The total light transmittance is slightly high, and the shielding property is poor compared with Examples 1 to 5. In addition, the color tone b value is large, and the whiteness is slightly low and the yellowness is strong compared with Examples 1 to 5. In addition, the polyester-based easy-to-bond film containing voids in Comparative Example 2 is affected by the polysilicone resin, and the appearance of the obtained functional easy-to-bond layer has the defect of pinhole shrinkage. In addition, the UV ink applied to the functional easy-to-bond layer also has the defect of pinhole shrinkage, resulting in poor adhesion. Comparative Example 2 cannot prevent coating omissions in the processing step of the produced polyester easy-to-bond film containing voids and printing omissions in the next step.

(Comparative Example 3) In Example 1, a void-containing polyester-based adhesive film was obtained by the same method as in Example 1 except that the raw material ratio of the void-containing layer A was changed as shown in Table 1. In the void-containing polyester-based adhesive film of Comparative Example 3, the surface density was lower than 0.80 g/cm ³ , the film itself had a weak sense of straightness, and as a result, the surface strength was also reduced. The film-forming property of Comparative Example 3 was inferior to that of Examples 1 to 5. In summary, the void-containing layer A of the void-containing polyester-based adhesive film of the present invention contains a trace amount of polysilicone resin, thereby suppressing the thermal degradation of the polypropylene resin in, for example, the processing step, and maintaining the void appearance. Therefore, the polyester adhesive film containing voids of the present invention has excellent adhesiveness, and has excellent lightness, film-forming property, shielding property and whiteness even if the apparent density is 0.80 g/cm ³ to 1.20 g/cm ^3. In particular, the polyester adhesive film containing voids of Examples 1 to 5 has excellent adhesiveness, and has excellent lightness, film-forming property, shielding property and whiteness even if the apparent density is 0.80 g/cm ³ to 1.10 g/cm ³ .

[Table 1] Unit Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Comparison Example 1 Comparison Example 2 Comparison Example 3 A layer Raw material 1 Polyethylene terephthalate resin Quality% 93.00 87.75 82.50 82.50 81.7 93.08 82.60 86.00 Raw material 2 Polypropylene resin Quality% 6.92 12.11 17.30 17.30 17.3 6.92 17.30 12.00 Raw material 3 Silicone resin ppm 800 1400 2000 2000 10000 0 1000 20000 Dimethicone ppm 118 196 270 270 1300 0 270 2700 Mass ratio of dimethicone/polypropylene resin Quality% 0.17 0.16 0.16 0.16 0.75 0.00 0.16 2.25 Layer Ratio First coating layer B1 % 10 10 10 5 10 10 0 10 Layer A containing voids % 80 80 80 90 80 80 100 80 Second coating layer B2 % 10 10 10 5 10 10 0 10 Functional easy-adhesion layer First coating layer B1 - have have have have have without Yes (On one side of layer A containing holes) have Apparent density g/cm ³ 1.18 1.03 0.97 0.93 0.82 1.22 0.95 0.75 Functional easy-adhesion layer Water contact angle after 150℃, 30 minutes Spend 72.2 71.8 71.5 77.6 71.3 - 77.2 73.3 Water contact angle after 72 hours at 85°C, 85%RH Spend 49.3 47.4 46.3 66.8 46.0 - 45.4 46.8 Diiodomethane contact angle after 150℃ and 30 minutes Spend 48.5 50.6 50.2 53.2 50.8 - 55.1 51.2 Diiodomethane contact angle after 72 hours at 85°C and 85%RH Spend 50.8 51.4 51.9 54.5 52.1 - 56.7 52.2 Whiteness level Hue b value - 1.2 1.2 1.2 1.3 1.1 1.2 1.5 1.1 Concealment Total light transmittance % twenty three twenty one 20 20 18 twenty four 26 17 Film making properties Film making properties - ○ ○ ○ ○ ○ ○ ○ △ UV curing ink adhesion - ○ ○ ○ ○ ○ × △ ○ Anti-static Ω/sq 6.0×10 ¹⁰ 5.0×10 ¹⁰ 7.3×10 ¹⁰ 2.0×10 ¹⁰ 6.0×10 ¹⁰ 9.9×10 ¹³ 6.7×10 ¹⁰ 5.8×10 ¹⁰ Shrinking appearance - ○ ○ ○ ○ ○ ○ × ○ [Industry Availability]

As described above, the void-containing polyester-based easy-adhesive film of the present invention is excellent in lightness, film-forming property, shielding property, and whiteness, and has easy adhesiveness, and can be suitably used as a base material for release films used in the manufacture of labels, cards, packaging materials, electronic materials, polarizing plates, and multilayer ceramic capacitors.

Claims (11)

A polyester-based adhesive film containing voids is sequentially laminated with a first coating layer B1, a layer A containing voids, and a second coating layer B2, wherein the first coating layer B1 comprises a polyester resin containing an inorganic pigment, the layer A containing voids comprises voids inside, the second coating layer B2 comprises a polyester resin containing an inorganic pigment, and a functional adhesive layer is provided on the first coating layer B1; the apparent density of the polyester-based adhesive film containing voids is greater than 0.80 g/ ^cm3 and less than 1.20 g/ ^cm3 ; the layer A containing voids comprises a composition containing a polyester resin, a polypropylene resin, and a polysilicone resin. The void-containing polyester adhesive film as described in claim 1, wherein in the void-containing layer A, the content of polydimethylsiloxane in the polysilicone resin is greater than 1 ppm and less than 2500 ppm relative to the total mass of the void-containing layer A. The void-containing polyester adhesive film as recited in claim 1, wherein in the void-containing layer A, the content of polydimethylsiloxane in the polysilicone resin is 0.005 mass % or more and 2.000 mass % or less relative to 100 mass % of the polypropylene resin. The polyester adhesive film containing voids as recited in claim 1, wherein the inorganic pigment in the first coating layer B1 and the second coating layer B2 is titanium oxide. The polyester adhesive film containing voids as described in claim 1, wherein the ratio of the sum of the thickness of the first coating layer B1 and the thickness of the second coating layer B2 to the sum of the thickness of the first coating layer B1, the thickness of the layer A containing voids and the thickness of the second coating layer B2 is greater than 6% and less than 40%. The polyester easy-to-bond film containing voids as described in claim 1 has a total light transmittance of more than 1% and less than 30%. The polyester adhesive film containing voids as described in claim 1 has an apparent density of 0.80 g/cm ³ or more and 1.10 g/cm ³ or less. The polyester-based adhesive film containing voids as described in claim 1, wherein the functional adhesive layer has a close-contact residual area of 99% or more as measured by the following evaluation method: Evaluation method of close-contact residual area: On the functional adhesive layer of the polyester-based adhesive film containing voids, UV ink [manufactured by T&K TOKA (Co., Ltd.); product name "BEST CURE (Registered Trademark) UV161 Blue S"] is used to print using a printing press [manufactured by Mei Seisakusho (Co., Ltd.); product name "RI TESTER"], and then the film coated with the ink layer is irradiated with 40mJ/cm2 using a high-pressure mercury lamp. ² of ultraviolet light to cure the ultraviolet curing ink; then, using Michelin cellophane tape (CT405AP-24), cut into 24mm wide and 50mm long pieces, and use a handy rubber roller to completely adhere the cellophane tape to the surface of the ink layer in a way that does not mix with air; then, tear off the cellophane tape vertically, and observe and calculate the residual area (closely contacted residual area) (%) of the printed layer in an area of 24mm×50mm. The polyester-based adhesive film containing voids as recited in claim 1, wherein the functional adhesive layer contains an antistatic agent and has a surface resistivity of less than 1.0×10 ¹³ Ω/sq. The polyester-based adhesive film containing voids as described in claim 1, wherein the number of pinhole-like shrinkages of the functional adhesive layer is 5/ ^m2 or less; the number of pinhole-like shrinkages of the functional adhesive layer is evaluated by visually observing the functional adhesive layer of the polyester-based adhesive film containing voids under a 3-wavelength fluorescent lamp and counting the number of pinhole-like shrinkages. The polyester adhesive film containing voids as recited in any one of claims 1 to 10 is used for labels, cards, packaging materials or release films.