JP5334475B2 - Label for in-mold molding and molded body with label - Google Patents

Description

  The present invention relates to an in-mold molding label and an in-mold molded body with an in-mold molding label using the same. More specifically, in an in-mold label made of a laminated resin film including a base layer and a heat seal layer, blow molding made of a wide variety of thermoplastic resin raw materials is performed by performing a specific surface treatment on the heat seal layer. The present invention relates to an in-mold label that can achieve a uniform high adhesive force to a body, and an in-mold molded body with a label using the same.

Blow molding techniques are well known in which molten thermoplastic resin is extruded into a cylindrical shape to form a parison, which is inflated by air pressure in a metal mold and shaped into a mold shape. At this time, a technique for obtaining a molded body in which the label is integrated is well known by fixing a label or a blank in the mold and sticking the label to the molten resin together with the shaping of the resin. Such an in-mold label is called an “in-mold label” (In-Mold Label, IML) or an “in-mold molding label”.
In-mold molding labels that can be used for applications that also require water resistance, chemical resistance, durability, etc., have been developed in the past, in addition to the characteristics of resin molded products such as water resistance, chemical resistance, and durability. Yes. For example, stretched or unstretched transparent film made of polyolefin resin, stretched or unstretched white film (synthetic paper) in which inorganic fine powder or organic filler is blended with polyolefin resin, and various types of heat on one side. Co-extruded seal layer in the course of film production (Patent Document 1), heat-sealing resin film bonded or laminated, heat-sealing resin coated on the surface using various coating equipment ( Patent Document 2) and the like have been proposed, and some have been put into practical use.

  These conventional in-mold molding labels are embossed on the surface of the heat seal layer during the label manufacturing process so that air is not trapped between the molded body and the label during in-mold molding (Patent Document 1). Applying unevenness to the heat seal layer of the label, such as pasting or laminating a pre-embossed film, or providing a trapezoidal uneven pattern during coating, etc. There is a device to allow air to escape by providing a communicating gap. In addition, when the concave / convex pattern for escaping these air is not formed on the surface, a method of opening the pores penetrating the label itself to release the air (Patent Document 3), a fine opening communicating with the label surface in the substrate There has been proposed a method (Patent Document 4) of applying a water-based heat-sealable resin coat to a film provided with a portion.

  Of these, the conventional method of coating the surface with a heat-sealable resin using various coating equipment is a heat-sealable resin that exhibits high adhesive strength to molded products made from a wide range of thermoplastic resin raw materials. The composition can be selected. However, in the case where a heat-sealable resin is coated on the surface of a base film that has been previously embossed (Patent Document 5), since the solvent absorption of the base film is low, most of the coating agent is a base film. There is a problem that it is difficult to reproduce the embossed shape on the surface of the coat. When using a film that does not absorb solvent, apply a hot melt resin or solvent heat seal resin coating with a high-viscosity coating using a gravure coating machine to create a trapezoidal pattern for the engraving roll cell on the substrate surface. The method of attaching to is also adopted. However, in this case, a high-viscosity coating is indispensable, resulting in an increase in production cost due to a decrease in productivity and a problem of fire and environmental pollution due to the use of an organic solvent.

Furthermore, in the method of applying an aqueous heat-sealable resin to a film having a fine opening on the surface, the water resistance of the labeled molded article is weak, and the label and molded article when the molded article is immersed in an aqueous liquid In particular, the adhesive strength when immersed in a detergent (surfactant solution) is remarkably reduced, and it is easy to peel off.
In the conventional method of providing the heat seal layer by co-extrusion or laminating during the production process of the base film, which is the simplest method for producing the label for in-mold molding, and embossing it, water resistance, chemical resistance, durability A label excellent in properties can be provided. However, since the heat-sealable resin is melt-extruded in an extruder and used, the resin that can be used is naturally limited due to the heat resistance of the resin, the equipment corrosivity, and the viscosity characteristics at the time of melting, and the melting point temperature is mainly 60 to 130. Polyolefin resin at 0 ° C. is used. From these resins, it is possible to produce labels that adhere with high adhesive strength to molded articles made of nonpolar polyolefin, but to produce labels that adhere with high adhesive strength to polar resins such as polyethylene terephthalate. could not.

  The inventors of the present invention provide a heat sealing layer by co-extrusion or laminating in the production process of the base film, and performs a process of chemically modifying the surface of the heat sealing layer based on the conventional technique of embossing the heat sealing layer. Therefore, intensive research was conducted to obtain an in-mold molding label that is excellent in water resistance, chemical resistance, and durability, and that can be applied not only to nonpolar resins but also to molded products of polar resins. The plasma treatment of these resin films is performed for the purpose of improving hydrophilicity and adhesion before coating, before printing, and before lamination with other molten resins. However, the corona oxidation treatment, which is generally performed for the purpose of improving the wetting of polyolefin film, is applied to the heat seal layer, and the adhesion to the molded body made of non-polar polyolefin resin, which was originally good, is remarkable. It was found to be damaged. For plasma treatment other than the corona treatment described above, a method of enclosing a minute amount of reactive gas under low pressure, and processing by mixing a minute amount of reactive gas into an expensive rare gas such as argon or helium under atmospheric pressure. A method or a method of mixing water vapor with nitrogen gas (Patent Document 6) has been reported. However, any of these methods cannot avoid the problem of complicated management of the processing environment pressure and the enclosed gas. Accordingly, the above-described methods for treating resin films are not so common, and the fact is that they are not so widespread that a person skilled in the art can easily try to accept or reject them.

Japanese Patent Laid-Open No. 02-084319 Japanese Patent Laid-Open No. 02-122914 Japanese Patent Laid-Open No. 02-108516 JP 2004-255864 A JP 05-249895 A JP 2003-155364 A

  By applying a specific plasma treatment to the heat seal layer of the label, the present invention is excellent in water resistance, chemical resistance and durability, and for molded articles such as polyethylene terephthalate which is a polar resin as well as a nonpolar resin. However, an object of the present invention is to provide an in-mold molding label having excellent adhesive force and an in-mold molded body to which the in-mold molding label is attached.

  As a result of further diligent research, the inventors conducted plasma discharge treatment on the heat seal layer of the in-mold molding label composed of a laminated resin film including a heat seal layer and a base layer under a pressure near atmospheric pressure. By applying the conventional coating equipment, various methods during production in the conventional method of coating the surface with a heat-sealable resin and attempts to provide a heat-sealable layer by coextrusion or lamination using a polar resin as the heat-sealable resin One or more thermoplastics selected from the group consisting of high-density polyethylene, low-density polyethylene, polypropylene, polyethylene terephthalate, or a copolymer of polyethylene terephthalate, having no problems and excellent in water resistance, chemical resistance, and durability. In-mold molding label that exhibits excellent adhesion to blow molded articles made of resin And it completed the present invention found that to be able to provide.

That is, the present invention relates to an in-mold molding label having the following configuration and a resin molded product with an in-mold molding label.
(1) A label for in-mold molding used for a blow molded article made of one or more thermoplastic resins selected from the group consisting of high-density polyethylene, low-density polyethylene, polypropylene, polyethylene terephthalate, or a copolymer of polyethylene terephthalate. The in-mold molding label is formed of a laminated resin film including at least a heat-seal layer and a base layer, and the heat-seal layer satisfies the following requirements.
1) A gas selected from air and nitrogen gas is introduced, plasma treatment is performed under a pressure near atmospheric pressure, and the adhesive force between the in-mold molding label after molding and the blow-molded body is dry, water-resistant In both adhesion and oil adhesion, the range is 200 to 500 g / 15 mm.
2) Surface roughness is 1-10 micrometers as three-dimensional center plane average roughness (SRa).
3) A thermoplastic resin having a melting point of 60 to 130 ° C.

here,
(2) The plasma treatment uses a pair of opposing electrodes covered with a solid dielectric, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency pulse voltage is applied to the electrodes. In addition, it is preferable that the heat seal layer is activated by generating plasma in the gas and passing an in-mold molding label between the electrodes, or (3) the plasma treatment is at least A pair of opposing electrodes, one of which is covered with a solid dielectric, is filled with gas under a pressure close to atmospheric pressure, and a high-frequency voltage is applied to the electrodes to generate plasma in the gas. The plasma gas is preferably blown from the electrodes to the heat seal layer of the in-mold molding label located outside the space between the electrodes, and the heat seal layer is activated.
(4) The gas used in the plasma treatment is preferably nitrogen gas.

The label for in-mold molding of the present invention is subjected to plasma treatment under normal pressure nitrogen gas,
(5) The atomic composition ratio from the surface of the heat seal layer to a depth of 10 nm is the ratio of the number of nitrogen atoms and the number of carbon atoms determined from the peak area of the 1S orbital spectrum using ESCA by performing the plasma treatment. (N / C) is preferably in the range of 0.02 to 0.07, and further, air is not trapped between the molded body and the label during in-mold molding,
(6) It is more preferable that the thermoplastic resin constituting the heat seal layer is made of a polyolefin resin.

(7) The base layer preferably contains a polyolefin-based resin.
(8) It is preferable that it contains at least one of an inorganic fine powder and an organic filler, and contains pores formed using this as a nucleus.
(9) In the blow molded article with a label for blow molding, the adhesive force between the in-mold molding label and the blow molded article after being immersed in a surfactant solution for 24 hours is maintained at 150 to 300 g / 15 mm. It is preferable that the present invention
(10) The above-mentioned in-mold molding label is formed into a blow molded article made of one or more thermoplastic resins selected from the group consisting of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate, or polyethylene terephthalate copolymer. It includes a resin molded body with a label formed by sticking.

  The in-mold molding label of the present invention has an excellent adhesive force not only for a non-polar resin molded body but also for a polar resin molded body such as polyethylene terephthalate. Even if the attached blow molded article is dipped in the surfactant solution, the label is not easily peeled off.

Below, the heat seal layer surface treatment in-mold molding label of the present invention and the blow-molded body with the label will be described in detail.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
(1) Base layer In the laminated resin film constituting the in-mold molding label of the present invention, the base layer provides the label with strength, printability, water resistance, chemical resistance, and in some cases opaqueness as a label support. To do. In forming the label, the heat seal layer is supported to facilitate the forming.

  The base layer includes a thermoplastic resin. Examples of the thermoplastic resin used for the base layer include polypropylene resins, polyethylene resins such as high density polyethylene, medium density polyethylene, and low density polyethylene, and polyolefin resins such as polymethyl-1-pentene and ethylene-cycloolefin copolymers. , Nylon-6, nylon-6,6, nylon-6,10, nylon-6,12 and other polyamide resins, polyethylene terephthalate and copolymers thereof, polyethylene naphthalate, aliphatic polyester and other thermoplastic polyester resins And thermoplastic resins such as polycarbonate, atactic polystyrene, syndiotactic polystyrene, polyphenylene sulfide, and the like. These may be used in combination of two or more.

Among these, from the viewpoints of chemical resistance and production cost, it is preferable to use a polyolefin resin, and it is more preferable to use a polypropylene resin.
As the polypropylene resin, it is preferable to use an isotactic polymer or a syndiotactic polymer obtained by homopolymerizing propylene. Copolymers mainly composed of propylene having various stereoregularities obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene and 4-methyl-1-pentene. Polymers can also be used. The copolymer may be a binary system or a ternary or higher multi-element system, and may be a random copolymer or a block copolymer.

The base layer may contain at least one of an inorganic fine powder and an organic filler in addition to the thermoplastic resin from the viewpoint of opacity and weight reduction, and may include pores formed using this as a core. good.
As the inorganic fine powder, those having an average particle diameter of usually 0.01 to 15 μm, preferably 0.01 to 8 μm, more preferably 0.03 to 4 μm from the viewpoint of stable film stretching and uniform pore formation. Can be used. Specifically, calcium carbonate, calcined clay, silica, diatomaceous earth, talc, titanium oxide, barium sulfate, alumina, or the like can be used.

  As the organic filler, those having an average particle diameter after dispersion of usually 0.01 to 15 μm, preferably 0.01 to 8 μm, and more preferably 0.03 to 4 μm can be used as in the case of the inorganic fine powder. As the organic filler, it is preferable to select a different type of resin from the thermoplastic resin that is the main component of the base layer. For example, when the matrix resin is a polyolefin resin, the melting point is polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, a cyclic olefin homopolymer or a copolymer of cyclic olefin and ethylene. Having a glass transition temperature of 120 ° C. to 280 ° C. can be used. If necessary, the base layer may further contain a stabilizer, a light stabilizer, a dispersant, a lubricant, a fluorescent brightener, a colorant, and the like.

  The film constituting the base layer is preferably stretched at least in a uniaxial direction from the viewpoint of weight reduction by pore formation and improvement of rigidity by molecular orientation. When the base layer is composed of a plurality of layers, it is preferable that at least one of the layers is stretched. When extending | stretching a several layer, you may extend | stretch separately before laminating | stacking each layer, and you may extend | stretch after laminating | stacking. Further, the stretched layer may be stretched again after being laminated. Furthermore, you may extend | stretch the whole, after shape | molding a heat seal layer in a base layer.

Various conventionally known methods can be used for stretching the base layer. For example, after a molten resin is extruded and formed into a sheet using a T die or I die connected to a screw type extruder, the sheet is subjected to a longitudinal stretching method between rolls using a difference in peripheral speed between rolls, a tenter Transverse stretching method using an oven, simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor, simultaneous biaxial stretching method using a pantograph type stretching device after cutting the sheet, and a circle connected to a screw type extruder Examples thereof include a simultaneous biaxial stretching (inflation molding) method in which a molten resin is extruded into a tube shape using a die and then air is blown into the tube.
When the thermoplastic resin is an amorphous resin, the stretching temperature is set to be equal to or higher than the glass transition point of the olefin resin to be used. In the case of a crystalline resin, the stretching temperature is set to be higher than the glass transition point of the amorphous part and lower than the melting point of the crystalline part. can do. Specifically, the temperature is 2 to 60 ° C. lower than the melting point of the thermoplastic resin to be used. When the resin is a propylene homopolymer (melting point 155 to 167 ° C.), 152 to 164 ° C., high density polyethylene (melting point 121 to 134). C.) is preferably 110 to 120 ° C. The stretching speed is preferably 20 to 350 m / min.

(2) Heat Seal Layer In the laminated resin film constituting the in-mold molding label of the present invention, the heat seal layer functions as an adhesive that joins the label and the blow molded body, and is solid at room temperature. Although it is shaped, it is activated by the heat of the molten resin when molding the resin molded body in the mold, melted and joined with the resin molded body, becomes solid again after cooling, and can exhibit strong adhesive force Is. The heat seal layer is made of a thermoplastic resin, and is provided as a part of the laminated resin film laminated on the base layer in the in-mold molding label of the present invention. More specifically, in the production process of the laminated resin film, a heat seal layer is provided as a film by co-extrusion with the base layer or melt lamination to the base layer.

The kind of the thermoplastic resin constituting the heat seal layer is not particularly limited as long as it has a function of sticking the label to the resin molded body by heating when forming the resin molded body by in-mold molding.
The thermoplastic resin constituting the heat seal layer in the present invention preferably has a melting point of 60 to 130 ° C. determined as a peak temperature by DSC measurement. If it is lower than 60 ° C., the stickiness of the label deteriorates due to stickiness at room temperature, and blocking or the like is likely to occur. Therefore, when inserting the label into the mold, troubles such as inserting two sheets are likely to occur frequently. On the other hand, if the temperature exceeds 130 ° C., the adhesion between the label and the molded body tends to deteriorate, such being undesirable.

Specific examples of thermoplastic resins include polyolefin resins, low density to medium density high pressure polyethylene, linear linear polyethylene, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene Acrylic acid alkyl ester copolymer, ethylene / methacrylic acid alkyl ester copolymer (alkyl group having 1 to 8 carbon atoms), ethylene / methacrylic acid copolymer metal salt (Zn, Al, Li, K, Na, etc.) ) And the like having a melting point of 60 to 130 ° C. These resins may be used alone or in combination of two or more.
Other known additives for resin can be arbitrarily added to the heat seal layer as long as the performance required for the heat seal layer is not impaired. Examples of such additives include dyes, nucleating agents, plasticizers, mold release agents, antioxidants, antiblocking agents, flame retardants, and ultraviolet absorbers.

  The heat seal layer has a three-dimensional center plane average roughness (SRa) based on JIS-B-0601: 2001 in order to prevent blistering due to air entrainment between the label and the molded body during in-mold molding. It is preferable to have an uneven shape of 10 μm. In order to give such an uneven shape, the heat seal layer can be embossed if necessary. The embossing can be carried out when the laminated resin film is formed or by pressing the embossing roll or the like after the forming and transferring the roll pattern. If the uneven shape is smaller than 1 μm, air is trapped between the molded body and the label at the time of blow molding, and an appearance defect called blister tends to occur, which is not preferable. Further, if it is 10 μm or more, irregularities appear in the appearance on the base layer side, and printing unevenness is likely to occur during printing, which is not preferable. The embossing roll used in the embodiment of the present invention has an uneven shape in which convex portions (head-cut pyramid shapes) formed by cutting off the vertices of a regular square pyramid are arranged at equal intervals. did.

(3) Plasma treatment under pressure near atmospheric pressure The following two types of methods can be applied to the plasma treatment under pressure near atmospheric pressure, which is carried out in the present invention. One is a method of performing treatment by passing a substrate to be treated through plasma generated between opposed electrodes, and is called a direct method or a planar method. In the present specification, this will be referred to as a direct method hereinafter.
The other is a method in which plasma generated between the electrodes is blown from the electrode toward the substrate to be processed by gas flow or electric field arrangement, such as a remote method, a downstream method, or a plasma jet method. It is what is called. In the present specification, it is hereinafter referred to as a remote method.

Here, under the pressure near atmospheric pressure refers to under a pressure in the range of 1.333 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa. Among these, a range of 9.331 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa is preferable because pressure adjustment is easy and the apparatus is simple. The atmospheric pressure (1 atm) is 10.133 × 10 ⁴ Pa. Since the plasma treatment used in the present invention is performed under a pressure near atmospheric pressure, it is excellent in workability and safety as compared with the conventional plasma treatment.
In the direct plasma processing, a pair of opposing electrodes covered with a solid dielectric is used, and a gas having a pressure near atmospheric pressure is introduced between the opposing electrodes with a substrate to be processed disposed between the electrodes. In this method, a pulsed voltage is applied to one electrode and the other is grounded, thereby performing plasma discharge in the gas and bringing the plasma into contact with the substrate.
In this case, both of the pair of electrodes used in the present invention may be flat plate-shaped, the ground-side electrode may be a roll shape, the application-side electrode may be a curved plate shape along the roll curved surface, and the ground-side electrode is a flat plate The application side electrode may have a plurality of fine lines.

  As said electrode, what consists of single metals, such as copper and aluminum, alloys, such as stainless steel and brass, is mentioned, for example. Solid dielectric materials include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, and complex oxides such as barium titanate (ceramics). ) And the like. The distance between the electrodes is preferably about 1 to 20 mm, although it depends on the magnitude of the applied voltage and the type of processing gas. If it is less than 1 mm, it becomes difficult to install the substrate to be treated within the interval, and if it is more than 20 mm, it is difficult to generate uniform discharge plasma.

In this plasma treatment, a pulse voltage is applied between the counter electrodes. The pulsed voltage waveform used may be any of an impulse waveform, a square waveform, and a modulation waveform. The rise time and fall time of the pulse voltage are preferably 100 μs or less, and particularly preferably 50 ns to 5 μs. If it exceeds 100 μs, it is easy to shift to arc discharge, and it becomes unstable, and it is difficult to realize less than 50 ns due to restrictions on the apparatus.
The rise time here refers to the time during which the voltage (absolute value) increases continuously, and the fall time refers to the time during which the voltage (absolute value) decreases continuously.

The frequency of the pulse voltage is preferably 0.5 to 100 kHz (similar applied voltage is expressed as a high frequency pulse voltage in this specification). If the frequency is less than 0.5 kHz, the plasma density is lowered and processing takes time. Conversely, if the frequency exceeds 100 kHz, arc discharge tends to occur, resulting in an unstable state.
The pulse duration is preferably 1 to 1000 μs. If the time is less than 1 μs, the discharge becomes unstable, and if it exceeds 1000 μs, it tends to shift to arc discharge. More preferably, it is 3 to 200 μs. Here, one pulse continuation time refers to a continuous ON time of one pulse in a pulse voltage composed of repetition of ON and OFF.

The difference between the plasma treatment of the present invention and the conventional corona treatment is that a high-frequency pulse voltage is applied to the application electrode using an electrode covered with a solid dielectric.
In the conventional corona treatment, a corona is generated using a high-frequency alternating current (sine wave, sine wave) voltage. However, arc discharge is likely to occur, and the treatment strength that can treat the substrate to be treated uniformly, that is, the set voltage. The range of is narrow. For example, in order to obtain a sufficient treatment effect in the corona treatment, for example, to introduce nitrogen atoms into the substrate to be treated under a nitrogen gas atmosphere, even if the voltage is increased, a uniform and stable corona hardly occurs and arc discharge is often caused. The nitrogen atom introduction effect is low, and surface defects increase. In addition, many low molecular weight oxides (degraded products) are generated on the surface of the substrate to be treated, and this causes problems in adhesion, and the treatment life is short due to the migration of the substrate to be treated. . This plasma treatment can generate a stable plasma with a wide range of treatment intensities and enables uniform activation treatment to the substrate to be treated. For example, nitrogen atoms can be introduced with high efficiency in a nitrogen gas atmosphere. As a result, high adhesive strength to the molded body can be obtained during in-mold molding.

Although it is possible to use air as the gas introduced in the plasma treatment of the present invention, the adhesive force between the label and the molded body after immersing the molded body with a label for in-mold molding in a surfactant solution, That is, in order to further improve the detergent resistance, it is preferable for the purpose of the present invention to use nitrogen gas capable of positively introducing nitrogen atoms into the substrate to be treated. In addition, this treatment can continuously process a roll-shaped substrate, and when nitrogen gas is introduced, nitrogen is introduced by a small amount of oxygen in the entrained air on the surface of the substrate. Not only atoms but also oxygen atoms are introduced into the surface of the substrate to be treated.
In the present invention, by performing a plasma treatment using nitrogen gas, the atomic composition ratio from the surface of the porous adhesive layer to a depth of 10 nm is obtained from the number of nitrogen atoms determined from the peak area of the 1S orbital spectrum using ESCA and The ratio of carbon atoms (N / C) is preferably in the range of 0.015 to 0.070.

The remote type plasma treatment is characterized in that the substrate to be treated is located between a pair of opposed electrodes.
Since it exists outside between electrodes, the to-be-processed base material is not damaged by the influence of a strong electric field. Therefore, a high processing effect according to the applied energy can be obtained. As the apparatus shape and method, two parallel sides of plate-like electrodes arranged in parallel are sealed to form a substantially cylindrical shape, and gas is introduced from one end that is not sealed, and the substrate to be processed from the other end. The method of spraying plasma toward the surface, both the application side and ground side electrodes are cylindrical, one is positioned inside the other, gas is introduced between the cylinders from the end of the cylinder, and the object is processed from the other end A method of spraying plasma toward the substrate, or a plate-shaped solid dielectric that has a plate-like application side and ground side electrode embedded therein, and a plurality of through holes are opened in the plate, The treatment base material is located below the ground side electrode, and includes a method of introducing gas from the application side to make it plasma in the through hole and spraying it on the treatment base material. Among these, more preferably, the treatment Plate-shaped electrode with large area It is a method that was used.

  This remote type solid dielectric is only required to be coated on at least one, and the same materials as those of the former direct type are used for the electrodes and the solid dielectric. The distance between the electrodes is preferably 0.1 to 50 mm. If it is less than 0.1 mm, it is difficult to install electrodes at intervals, and if it exceeds 50 mm, uniform discharge plasma is difficult to be generated. Furthermore, although the space | interval of an electrode edge part and a to-be-processed base material is based also on an applied voltage and the flow rate of gas, 1-50 mm is preferable. If it is less than 1 mm, arc discharge tends to occur from the electrode end to the substrate to be treated. The voltage applied to the electrode is a high frequency voltage. The waveform may be an alternating wave having a sine waveform or a sine waveform, or may be pulsed having an impulse waveform, a square waveform or a modulated waveform.

  This remote method blows out the plasma generated between the electrodes to the outside of the electrode with the substrate to be processed, and applies a certain amount of pressure to the gas to be introduced to flow the plasma to the substrate to be processed. Alternatively, there is a method in which plasma is blown out by an electric field generated by a voltage applied between electrodes in order to generate plasma, or a method in which both are combined, but a method using a gas flow in which the applied voltage can be changed is preferable. Although air can also be used as the gas introduced in the plasma treatment, it is preferable for the purpose of the present invention to use nitrogen gas capable of introducing nitrogen atoms into the substrate to be treated.

In the present invention, a high frequency voltage or a high frequency pulsed voltage is applied to the plasma treatment. Since both of these waveform voltages are converted from a direct current power source, the surface treatment to the substrate to be treated (heat seal layer) is strong. The processing strength (kJ / m ² ) obtained from the value obtained by dividing the power (wattage) of the original DC power source by the processing area (processing speed × processing width) per unit time of the substrate to be processed is obtained. be able to. The optimum range of the treatment strength varies depending on each treatment method, the substrate to be treated, and the clearance (gap distance), but it is sufficient that the substrate to be treated does not have arc damage, thermal deformation, shrinkage, etc., 1 to 300 kJ / m ² is preferred.

The heat seal layer of the present invention is formed by the plasma treatment described above, and the adhesive force between the label and the resin molded body when the resin molded body with a label for in-mold molding is formed (in the section of [Label Adhesion] described later, (Adhesive force of water tight adhesion and oil tight adhesion) is 200 to 500 gf / 15 mm, preferably 250 to 500 gf / 15 mm, particularly preferably 350 to 500 gf / 15 mm. If the adhesive force is lower than 200 gf / 15 mm, the label may be peeled off due to an impact applied during transportation after the contents of the resin-molded body with a label are filled or during product display.
Further, in the present invention, the adhesive strength between the label and the resin molded article after the resin molded article with a label is immersed in a surfactant solution for 24 hours (adhesive strength for adhesion to a detergent in the section of [Label Adhesion] described later). Is preferably 150 to 300 g / 15 mm, and more preferably 170 to 290 g / 15 mm. When the adhesive strength is lower than 150 gf / 15 mm, when the molded body is, for example, a container and a surfactant such as a body soap or shampoo is used as a content, the label may be peeled off due to a long-term use.

The features of the present invention will be described more specifically with reference to examples and comparative examples.
The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Example 1
<Manufacture of laminated resin film>
Propylene homopolymer (trade name “Novatech PPMA-8”, melting point 164 ° C., manufactured by Nippon Polypro Co., Ltd.) 67% by weight, high density polyethylene (trade name “Novatech HDHJ580”, melting point 134 ° C., manufactured by Nippon Polyethylene Co., Ltd.) ) A resin composition (C) comprising 10% by weight and 23% by weight of calcium carbonate powder having an average particle size of 1.5 μm was melt-kneaded at 250 ° C. using an extruder and then extruded into a film from a die. The film was cooled to a temperature of 50 ° C. This film was heated again to about 150 ° C. and then stretched 4 times in the longitudinal direction using the peripheral speed of the roll group to obtain a uniaxially stretched film serving as a core layer.

  On the other hand, propylene homopolymer (trade name “Novatech PPMA-3”, manufactured by Nippon Polypro Co., Ltd.) 51.5% by weight, high density polyethylene (trade name “Novatech HDHJ580”, manufactured by Nippon Polyethylene Co., Ltd.) 3.5 A resin composition (D) consisting of 42% by weight of calcium carbonate powder having an average particle size of 1.5 μm and 3% by weight of titanium oxide powder having an average particle size of 0.8 μm was melted at 240 ° C. using another extruder. This was kneaded and extruded onto a single side of the uniaxially stretched film in a film form from a die and laminated to obtain a surface layer / core layer (D / C) laminate.

  Furthermore, propylene homopolymer (trade name “Novatech PPMA-3”, manufactured by Nippon Polypro Co., Ltd.) 51.5% by weight, high density polyethylene (trade name “Novatech HDHJ580”, Nippon Polyethylene, respectively) using different extruders. A resin composition (E) comprising 3.5% by weight, 42% by weight of calcium carbonate powder having an average particle size of 1.5 μm and 3% by weight of titanium oxide powder having an average particle size of 0.8 μm, and heat sealing As a layer, linear linear polyethylene (resin a) (trade name “Novatech LLUJ580”, melting point 123 ° C., manufactured by Nippon Polyethylene Co., Ltd.) 80% by weight and ethylene / vinyl acetate copolymer (resin b) (melting point 63 ° C.) 20% by weight of the resin composition (B) is melt-kneaded at 200 ° C., supplied to one coextrusion die, laminated in the die, The laminate (D / C) is laminated so that the heat seal layer is the outermost layer on the surface of the laminate (D / C), and has a four-layer structure of surface layer / core layer / back layer / heat seal layer. A laminate (D / C / E / B) was obtained. The heat-seal layer side of the obtained laminate is passed through an embossing roll (150 wires per inch, depth 40 μm, reverse gravure type) made of a metal roll and a rubber roll, and 0.17 mm intervals are provided on the heat-seal layer (B) side. The pattern was embossed. In the laminate having the four-layer structure, the surface layer / core layer / back surface layer (D / C / E) corresponds to the base layer of the present invention. The embossed surface had a three-dimensional center plane average roughness (SRa) of 2 μm.

This four-layer laminate is guided to a tenter oven, heated to 155 ° C., stretched 5 times in the transverse direction using a tenter, then heat-set (annealed) at 164 ° C., and further cooled to 55 ° C. After slitting the ear, the corona discharge treatment was applied to the surface layer (D) side. When the value obtained by dividing the amount of power of the DC power source before conversion to a high frequency by the area of the substrate to be processed was defined as the processing strength, it was 1.5 kJ / m ² . Then, it wound up in roll shape with the winder and was set as the laminated resin film of Example 1.

<Plasma treatment>
The above-mentioned laminated resin film was subjected to direct plasma treatment under a pressure in the vicinity of atmospheric pressure under the following conditions.
Each of the pair of electrodes has a plate shape, and is made of stainless steel so as to have a length of 100 mm, a width of 150 mm, and a thickness of 20 mm, and is covered with a ceramic that is a solid dielectric. A cavity through which a cooling medium can flow is provided inside the electrode, and the cooling medium can be circulated and pumped to maintain a constant temperature during the discharge process. These pair of electrodes were fixed so as to maintain a distance of 20 mm. The heat treatment layer side of the substrate to be treated (laminated resin film) was directed to the application side electrode between these electrodes, and the distance between the application side electrode and the substrate was adjusted to 10 mm. Further, nitrogen gas was introduced between the electrodes at 10.133 × 10 ⁴ Pa and 100 l / min, and the base roll was wound at a speed of 30 m / min, and a pulse with a frequency of 50 kHz and a pulse duration of 100 μs was applied to the application side electrode. A plasma discharge treatment was applied to the heat seal layer of the substrate to be treated by applying a voltage. When the value obtained by dividing the amount of power of the direct current power source before pulsing by the area of the substrate to be treated was defined as the treatment intensity, the intensity of the plasma treatment was 12 kJ / m ² .

<Printing>
A high-speed letterpress label printing machine (manufactured by Shiki Co., Ltd.) and UV offset ink (trade name “Best Cure”, manufactured by T & K TOKA Corporation) are formed on the surface of the plasma-treated substrate thus obtained. The product name, manufacturer, sales company name, character, barcode, usage method, etc. were printed at 4 speed with a UV seal at a speed of 26.4 m / min. Further, UV gloss OP varnish to which a release agent was added was coated and dried by irradiation with ultraviolet rays.
<Punching>
The printed product thus obtained was once cut from a roll shape into a sheet shape, and then punched into a label shape having a length of 11 cm and a width of 9 cm to obtain an in-mold forming label.

<Adhesion-1>
After fixing this in-mold molding label to one of the blow molds using a vacuum so that the surface layer side is in contact with the mold, high-density polyethylene (trade name “NOVATEC HDHB330”, melting point 133 ° C., Nippon Polyethylene (Made by Co., Ltd.) is melt-extruded parison at 220 ° C., and the split mold is clamped after being introduced between the split molds, 0.4 MPa of compressed air is supplied into the parison, and the parison is expanded and shaped into a container. At the same time, it was heat-sealed with an in-mold label. The mold was cooled to 10 ° C., and after about 10 seconds, the mold was opened to obtain a resin container (an in-mold molded article with a label of the present invention) on which a label with an internal volume of 1,000 ml was attached. . There was no fading in the printing of the label attached to the resin container, and no shrinkage of the label or generation of blisters was observed.

<Adhesion-2>
In addition, after fixing this in-mold molding label to one of the blow molds using a vacuum so that the surface layer side is in contact with the mold, polyethylene terephthalate (trade name “Unipet RD383”, melting point 235 ° C., Nippon Unipet Co., Ltd.) was melt-extruded at 260 ° C. into a parison. After being introduced between the split molds, the split mold was clamped, 0.5 MPa of compressed air was supplied into the parison, and the parison was expanded into a container shape. It was shaped and heat-sealed with an in-mold label. The mold was cooled to 15 ° C., and after about 10 seconds, the mold was opened to obtain a resin container (an in-mold molded article with a label of the present invention) on which a label with an internal volume of 1,000 ml was attached. There was no fading in the printing of the label attached to the resin container, and no shrinkage of the label or generation of blisters was observed.

(Example 2)
In Example 1, except that the processing speed was set to 60 m / min, twice that of Example 1, so that the plasma processing intensity was 6 kJ / m ² , which was half that of Example 1, the in-mold was manufactured. A label for molding and an in-mold molded body with a label were obtained.
(Example 3)
In Example 1, it was manufactured in the same manner as in Example 1 except that the processing speed was set to 120 m / min, which is four times that in Example 1, so that the processing intensity of the plasma processing was ¼, 3 kJ / m ^2. Thus, an in-mold molding label and an in-mold molded body with a label were obtained.
Example 4
In Example 1, a label for in-mold molding and an in-mold molded body with a label were obtained in the same manner as in Example 1 except that air was introduced instead of nitrogen gas for plasma treatment.

(Example 5)
In Example 1, in order to change the plasma treatment from the direct method to the remote method, the same electrode as in Example 1 was used, the distance between the electrodes was fixed to 1 mm, and the two sides of the electrode squared were sealed into a cylindrical shape, The roll of the laminated resin film, which is the substrate to be treated, is placed outside the pair of electrodes, and the heat seal layer side of the substrate to be treated (laminated resin film) is directed to these electrodes. The distance from the substrate was adjusted to 3 mm. Further, nitrogen gas was introduced between the electrodes at a flow rate of 10.133 × 10 ⁴ Pa and 300 l / min so as to be blown toward the adhesive layer side of the roll. Implemented except that the roll was wound at a speed of 5 m / min, a high-frequency voltage was applied to the electrode so that the amount of power of the DC power supply before high-frequency conversion was 1 kw, and a plasma treatment with a treatment intensity of 80 kJ / m ² was performed. In the same manner as in Example 1, an in-mold molding label and an in-mold molded body with a label were obtained.

(Example 6)
In Example 1, the embossing roll (150 lines per inch, depth 130 μm, reverse gravure type) was changed so that the three-dimensional center plane average roughness (SRa) of the embossed surface of the heat seal layer was 9 μm. Except for embossing, the same production as in Example 1 was carried out to obtain an in-mold molding label and a labeled in-mold molding.

(Comparative Example 1)
In Example 1, except that the heat-sealing layer was not subjected to plasma treatment, it was produced in the same manner as in Example 1 to obtain an in-mold molded label and a labeled in-mold molded body.
(Comparative Example 2)
In Example 1, except manufacturing a heat seal layer (B), it manufactured like Example 1 and obtained the label for in-mold fabrication, and the in-mold molded article with a label.

(Comparative Example 3)
In Example 1, corona discharge treatment was used instead of plasma treatment. The discharge electrode of the device is enclosed, nitrogen gas is introduced into the enclosure at a flow rate of 10.133 × 10 ⁴ Pa and 80 l / min, and the roll is wound at a speed of 20 m / min and converted to high frequency. Corona discharge treatment is applied to the heat seal layer of the laminated resin film by applying a high frequency voltage to the electrodes so that the treatment intensity obtained by dividing the amount of power of the previous DC power source by the area of the substrate to be treated is 3 kJ / m ^2. Except having applied, it manufactured similarly to Example 1, and obtained the label for in-mold shaping | molding, and the in-mold molded object with a label.

(Comparative Example 4)
In Example 1, except that embossing with an embossing roll was not performed, the same production as in Example 1 was performed, and the three-dimensional center plane average roughness (SRa) of the embossed surface of the heat seal layer was 0.5 μm. Labels and in-mold molded articles with labels were obtained.
(Comparative Example 5)
In Example 1, the embossing roll (150 lines per inch, depth 170 μm, reverse gravure type) was changed so that the three-dimensional center plane average roughness (SRa) of the embossed surface of the heat seal layer was 12 μm. Except for embossing, the same production as in Example 1 was carried out to obtain an in-mold molding label and a labeled in-mold molding.

(Comparative Example 6)
In Example 1, as a thermoplastic resin used for the heat seal layer, linear linear polyethylene (resin a) (trade name “Novatech LLUJ580”, melting point 123 ° C., manufactured by Nippon Polyethylene Co., Ltd.) 80% by weight, ethylene / vinyl acetate A label for in-mold molding and an in-mold molded body with a label were obtained in the same manner as in Example 1 except that a resin composition comprising 20% by weight of copolymer (resin c) (melting point: 44 ° C.) was used.

(Comparative Example 7)
In Example 1, as a thermoplastic resin used in the heat seal layer, high-density polyethylene (resin d) (trade name “NOVATEC HDHJ360”, melting point: 132 ° C., manufactured by Nippon Polyethylene Co., Ltd.) 80% by weight and ethylene / vinyl acetate A label for in-mold molding and a labeled in-mold molded body were obtained in the same manner as in Example 1 except that a resin composition comprising 20% by weight of polymer (resin b) (melting point 63 ° C.) was used.

[Test example]
About the label for in-mold shaping | molding manufactured in the said Examples 1-6 and Comparative Examples 1-7 and the in-mold molded object with a label, the following physical property measurement and evaluation were performed.
[Three-dimensional center plane average roughness (SRa) of heat seal layer]
Based on JIS-B-0601: 2001, the three-dimensional center plane average roughness (SRa) of the surface of the heat seal layer of the label for in-mold molding is measured using a three-dimensional roughness measuring machine (trade name “SE-3AK”, Kosaka And a analyzer (trade name “ModelSPA-11”, manufactured by Kosaka Laboratory). The results are shown in Table 1.

[Atom composition ratio]
Using an ESCA spectrometer (trade name “ESCA3200 type”, manufactured by Shimadzu Corporation), incident X-ray: Mg—Kα ray (1250 eV), X-ray output: 8 kv × 30 mA (output 240 W), measurement environment is a degree of vacuum: about Under the condition of 10E-5 Pa, the peak area obtained from the 1S orbital spectrum of the carbon of the surface layer part from the surface of the heat seal layer of the in-mold molding label to the depth of 10 nm, similarly obtained from the 1S orbital spectrum of nitrogen obtained. The peak area was measured. Further, the ratio of the number of nitrogen atoms to the number of carbon atoms (N / C) was determined from the detected intensity of each element. The results are shown in Table 1.

[Unevenness during printing]
After the above printing, the following evaluation was performed by visually observing printing unevenness due to the influence of the roughness of the heat seal layer on the base layer side (surface layer side) surface. The results are shown in Table 1.
○: No problem even if observed carefully.
Δ: Unevenness can be seen by careful observation.
X: Unevenness is found even with normal visual inspection.

[Adaptability to insert molds]
In each process of the sticking-1 and the sticking-2, the attachment state of the label to the mold in each of the 100 shots of hollow molding was evaluated based on the following criteria. The results are shown in Table 1.
○: All installed at the specified position without any problem.
X: There were problems such as dropping of the label at the time of mounting, insertion of two labels, and displacement of the designated label position.

[Blister occurrence]
In each process of the above-mentioned sticking-1 and sticking-2, the blister generation situation of 20 sticking labels each obtained was judged on the standard shown below.
○: Blister generation in all containers is less than 20% of the label area.
X: There is a container where blister generation is 20% or more of the label area.

[Label adhesive strength]
Cut the label part of the container with the label pasted into 15 mm width, and immerse it as it is or under the following conditions, and then peel off a part of the pasted label end. AGS-D type "(manufactured by Shimadzu Corporation) was used to measure the peel strength (g) when the label part and the container part were peeled off at a pulling rate of 200 mm / min, and the average value thereof was determined and shown below. Judged by criteria.
◎: 200 g or more ○: 150 to less than 200 g Δ: 100 to less than 150 g ×: less than 100 g

The same sample cut to a width of 15 mm is immersed in the following various liquids as they are or at room temperature for 24 hours, and then the various liquids are wiped off so that the evaluation is not hindered, and the adhesion (peel strength) is confirmed by the above method. And evaluated according to the above criteria.
Dry: No pickling Water-resistant adhesion: Water (distilled water)
Oil-resistant adhesion: Edible oil (trade name “Nisshin beni flower oil”, manufactured by Nisshin Oilio Group)
Detergent-resistant adhesion: Detergent for tableware (trade name “Charmy Green”, manufactured by Lion Corporation)

  The present invention can be suitably applied in the technical field of an in-mold molding label and an in-mold molding with an in-mold molding label using the same.

Claims (10)

A label for in-mold molding used for a blow molded article made of one or more thermoplastic resins selected from the group consisting of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate, or a copolymer of polyethylene terephthalate, An in-mold molding label, wherein the in-mold molding label comprises a laminated resin film including at least a heat seal layer and a base layer, and the heat seal layer satisfies the following requirements.
(1) A gas selected from air and nitrogen gas is introduced, plasma treatment is performed under a pressure near atmospheric pressure, and the adhesive strength between the in-mold molding label after molding and the blow molded body is dry, Both water-resistant adhesion and oil adhesion are in the range of 200 to 500 g / 15 mm.
(2) The surface roughness is 1 to 10 μm as the three-dimensional center plane average roughness (SRa).
(3) It consists of a thermoplastic resin having a melting point of 60 to 130 ° C.   The plasma treatment uses a pair of opposed electrodes covered with a solid dielectric, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency pulse voltage is applied to the electrodes to form a gas. The in-mold molding label according to claim 1, wherein the heat-sealing layer is activated by generating plasma therein and passing the in-mold molding label between the electrodes.   The plasma treatment uses a pair of opposed electrodes, at least one of which is covered with a solid dielectric, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency voltage is applied to the electrodes. Plasma is generated in the gas, and the plasma gas is blown out from the electrode to the heat seal layer of the in-mold molding label located outside between the electrodes, and the heat seal layer is activated. The label for in-mold molding according to claim 1.   The in-mold molding label according to any one of claims 2 and 3, wherein a gas used in the plasma treatment is nitrogen gas. The atomic composition ratio from the surface of the heat seal layer to a depth of 10 nm is the ratio of the number of nitrogen atoms and the number of carbon atoms determined from the peak area of the 1S orbital spectrum using ESCA (N / The in-mold molding label according to claim 4, wherein C) is in the range of 0.02 to 0.07. The in-mold molding label according to any one of claims 1 to 5, wherein the thermoplastic resin constituting the heat seal layer is a polyolefin resin.   The label for in-mold molding according to any one of claims 1 to 6, wherein the base layer contains a polyolefin-based resin.   The in-mold molding according to any one of claims 1 to 7, wherein the base layer includes at least one of an inorganic fine powder and an organic filler, and includes pores formed using the core as a core. For labels.   The adhesive strength between the in-mold molding label and the blow-molded body after the blow-molded body with the label for in-mold molding is immersed in a surfactant solution for 24 hours is 150 to 300 g / 15 mm, The label for in-mold molding according to any one of claims 1 to 8.   The in-mold molding label according to any one of claims 1 to 9, wherein the one or more selected from the group consisting of high-density polyethylene, low-density polyethylene, polypropylene, polyethylene terephthalate, or a copolymer of polyethylene terephthalate. A blow molded article with a label formed by sticking to a blow molded article made of a thermoplastic resin.