JPH03260689A - In-mold label - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Background of the invention]

<Industrial Application Field> The present invention relates to an in-mold label (including a blank) used for a label (including a blank) that is attached to a synthetic resin container manufactured by differential pressure molding or blow molding at the same time as the container is molded. , a label is set in advance in a mold, and a thermoplastic resin is blow-molded, vacuum-formed, or pressure-formed on top of the label, thereby making it possible to integrally mold a resin-molded container with a label and decorate the container. Regarding labels for molds. <Conventional technology> Conventionally, in order to integrally mold a resin molded container with a label,
A blank or label is inserted into a mold in advance, and then the container is molded by injection molding, blow molding, differential pressure molding, foam molding, etc., and the container is decorated (Japanese Patent Laid-Open No. 58-69015) , European Published Patent No. 254
(See specification No. 923). Such labels include gravure-printed resin films, offset multicolor printed synthetic paper (for example, Japanese Patent Publication No. 46-40794, Japanese Patent Publication No. 54-31030, British Patent No. 109005).
9), or an aluminum label in which polyethylene is laminated on the back side of aluminum foil and gravure printing is performed on the front side of the foil. <Problems to be Solved by the Invention> However, the manufacturing method of the resin molded container decorated with the above label does not require high pressure (20 to 200 kg) such as injection molding.
The method of fusing the label and the molten resin container with
g/go, -50 to -650wHg) and hollow molding (1 to 1
In methods of molding at low pressures such as 0 kg/g), due to the recent development of high-speed molding machines, there was insufficient air escape between the blank and the melting container, and blisters were generated here and there between the container and the blank. It was found that small amounts of containers were generated. Therefore, we used an embossing roll with recesses on its surface (normal embossing type roll) to create a convex embossed pattern on the back side of the label that adheres to the container, thereby creating a barrier between the container and the back of the label when forming the container. It has been proposed and implemented to facilitate air escape to obtain blister-free labeling containers. However, this method of preventing blisters by providing a convex embossed pattern on the back side of the label (the side that is attached to the container) is not effective under molding conditions or in a narrow range (especially when the resin temperature is high during molding). However, it was found that when trying to further lower the resin temperature during molding to shorten the time required for cooling to improve high-speed moldability, the adhesive strength of the label was insufficient. In addition, if the temperature of the molding resin is raised to obtain a container with better gloss, the decomposition gases and sublimation of the antioxidants and antistatic agents added to the resin will increase, resulting in labeling. Gas accumulation occurs between the molded product and the molded product, resulting in poor blister prevention properties. Therefore, in the present invention, it is an important technical challenge to create a label that is suitable for a wide range of molding conditions, such as molding temperature range, shot cycle width, and shape of the molded product.

[Summary of the invention]

Summary> The inventors of the present invention have conducted intensive research in view of the above problems, and as a result, have developed a method for setting an in-mold label in advance in a mold when blow molding, vacuum molding, or pressure molding thermoplastic resin. , in an in-mold label in which a thermoplastic resin is supplied to the mold and the thermoplastic resin is pressed and adhered to the wall of the mold, the surface of the label on the side to be adhered to the container is formed into a reverse gravure pattern. By making the embossing (concave), the four parts of the emboss have an independent chamber structure, and by having the concave chambers distributed over the entire surface of the label, gas and air can be dispersed little by little into the concave areas. The present invention was developed based on the knowledge that if the label is sealed in a shape, it can significantly reduce the occurrence of blistering on the label, which occurs when gas or air collects in a part of the label. be. That is, the in-mold label of the present invention is produced by embossing a reverse gravure pattern on a resin film with a roll number of 80 to 200 lines/inch, and then stretching the film. A label for molding, in which the surface area of the convex portion above the center line of the amplitude of the peaks and valleys of the unevenness on the surface of the embossed side of the film after stretching accounts for 50 to 90% of the surface area of the label. %, and the average depth of the concave portion below the center line is 0.5 ~
It is characterized by having a thickness of 10 μm. Effect> Such an in-mold label of the present invention can be obtained by setting an in-mold label in advance in a mold when blow molding, vacuum forming, or pressure forming a thermoplastic resin, and melting the in-mold label into this mold. A resin-molded container with a label is integrally molded by supplying a thermoplastic resin, pressing the thermoplastic resin against the mold wall, and sticking the in-mold label to the thermoplastic resin. There is no deformation of the label, the adhesion between the container body and the label is strong, there is no blister, and the container is decorated with a label and has a good appearance. In particular, in the in-mold label of the present invention, the adhesive surface of the adhesive layer with the container is embossed and formed in a reverse gravure type, so the area of the convex part (the adhesive surface between the container and the label) is the area of the label. This accounts for the majority, and the adhesive strength per unit area is increased compared to conventional labels with a convex pattern obtained using an embossing roll with a regular gravure pattern. In addition, by making the embossed part of the adhesive layer into a reverse gravure type, the recesses form an independent chamber structure, and by distributing the recesses over the entire surface of the label, gas and air can be contained in a dispersed form little by little. In addition, by setting the depth of the recess to 0.5 to 10 μm, which is extremely small compared to the thickness of the entire label, it is possible to prevent the label from lifting when gas or air collects in a part ( The occurrence of blisters can be significantly improved. [Eco-in-mold label (1) Structure The in-mold label of the present invention is a label that is attached to a container in a mold when a synthetic resin container is manufactured by differential pressure molding or blow molding. . Such an in-mold label is made of a single-layer stretched film with an embossed pattern of the above structure formed on the back side and a melting point of 85 to 1, with an embossed pattern of the above structure formed on the back side.
A two-layer structure in which a 30°C resin adhesive layer is adhered to a base layer made of a higher temperature resin, or a paper-like layer made of a stretched resin film containing inorganic fine powder is formed on the surface,
It can be a three-layer structure with a base material layer formed in the middle and a low melting point resin adhesive layer on the back side, or a laminated paper strip-like structure with a multilayer structure. preferable. Such an in-mold label has a paper strip shape before being attached to a container in a mold, but becomes integral with the container after being attached. The label is embossed on the back side (the side to be affixed to the container) with a reverse gravure pattern using a roll number of 80 to 200 lines/inch, and then embossed with a reverse gravure pattern in the vertical direction.
By stretching 8 times and/or 4 to 12 times in the transverse direction, the surface area of the convex portion is preferably 50 to 90% of the entire label from the center line of the amplitude of the peaks and valleys of the unevenness on the film surface after stretching. occupies 55 to 80%, and the average depth of the recesses from the center line is 0.5 to 10 μm, preferably 1 to 8 μm. Such an in-mold label can be used as an in-mold label in differential pressure molding such as vacuum forming or pressure forming, or in blow molding in which a parison is pressed against the inner wall of a mold using compressed air. Of course, it can also be used as an in-mold label for injection molding. Although any structure may be used as long as it has the above structure, a preferred method for manufacturing an in-mold label will be described below in more detail. [1 [Manufacture of in-mold label (1) Constituent materials (a) Base layer The in-mold label of a preferred embodiment of the present invention is usually composed of a base layer and an adhesive layer, and as the base layer The materials used include a thermoplastic resin with a melting point of 135-264°C, such as polypropylene, high-density polyethylene, polyvinyl chloride, polyethylene terephthalate, and polyamide, containing 8-65% by weight of inorganic fine powder, or a resin film. , a film in which an inorganic filler-containing latex (coating agent) is coated on the surface of the resin film, or a film in which aluminum is vapor-deposited on the resin film. Such a base material layer may be a single layer or may have a laminated structure of two or more layers. (b) Adhesive layer The back side of the resin film of the base layer (the side in contact with the resin container) is made of low-density polyethylene, vinyl acetate/ethylene copolymer, ethylene/acrylic acid copolymer, ethylene, etc. - A film layer made of a heat-sealable resin having a melting point of 85 to 135°C, such as a metal salt of a methacrylic acid copolymer, is laminated. Alternatively, an adhesive layer may be formed by applying an emulsion of these resins or a solution dissolved in a solvent and drying. Lamination of this heat-sealable resin film layer can further strengthen the adhesion between the in-mold label and the resin container. However, if the resin to be molded and the resin of the label material are the same, the adhesive layer may be omitted. (2) Embossing And this heat-sealable resin film layer has a reverse gravure type pattern with a number of dots or lines of 1 inch (2,
Embossing is performed using a metal roll and a rubber roll, which are formed into an embossed pattern of 80 to 200 lines per 54 cm)'. It is important that the embossing is an inverted gravure type pattern (see Figure 5) that has many independent four-part structures surrounded by ridge lines, and has a convex shape that allows the gas in each chamber to move freely as shown in Figure 7. The effects of the present invention cannot be achieved with a regular gravure type pattern. (3) Stretching The laminate structure film after the embossing process is stretched in at least one direction, usually 4 to 12 times, preferably 4 to 8 times. The stretching is performed at a temperature lower than the melting point of the resin of the base layer and higher than the melting point of the heat-sealable resin. Although the base material layer is oriented by this stretching, the heat seal layer is not oriented. (4) Other treatments The stretched laminated structure film (synthetic paper) may be subjected to corona discharge machining, flame treatment, plasma treatment, etc. to improve its surface printability and adhesion, if necessary. You can leave it there. The surface side of the base material layer, for example, the paper-like layer, is usually printed. Examples of such printing include gravure printing, offset printing, flexo printing, and screen printing.
With this, it is possible to print the product name, manufacturer, sales company name, characters, barcode, usage instructions, etc. . (5) Stamping Process The printed and embossed container label is separated into labels of required shapes and dimensions by stamping process. This label may be a partial label attached to a part of the container surface, but it is usually used as a blank surrounding the side of a cup-shaped container in differential pressure molding, and on the front and back sides of a rough container in blow molding. It is manufactured as a label that is attached to [III] The in-mold label of the present invention manufactured as an in-mold label clay bell has the above-described structure, and is formed by differential pressure forming such as vacuum forming or pressure forming, or by forming a parison by pressure forming. It can be used as an in-mold label for hollow molding, etc., which is crimped onto the inner wall of a mold. Below, as a representative example of the in-mold label of the present invention, a blank for a blow-molded container will be cited and specifically explained. FIG. 1 shows a cross-sectional view of a two-layer in-mold label used for blow molding, which is cited as an example of the in-mold label of the present invention. In this Figure 1, 1 is an in-mold label, and 2
3 is a thermoplastic resin film base material layer constituting it, 3 is a printing layer, and 4 is an adhesive layer formed from a heat-sealable resin film. In addition, 5 is the top of the twill (convex part) which has been given a lattice pattern by embossing the adhesive layer made of the heat-sealable resin film using a reverse gravure roll, and 6 is the trough (four parts) of the lattice pattern. This shows that. FIG. 2 shows a plan view of the adhesive layer 4 side (back side of the in-mold label) made of a human-sealable resin film of the in-mold label 1, and FIG. 3 shows the in-mold label 1 shown in FIG. FIG. 4 shows a cross-sectional view of a laminated structure film before stretching and printing to obtain a label, and FIG.
It is a partially enlarged view of the laminated structure film shown in the figure. The embossed pattern of the laminated structure film shown in Fig. 3 is
Decrease the number of dots or lines on the roll, e.g. 1 inch (2,54
80 to 200 wires are provided per crr+). If it is less than the above range, the grooves in the four parts 6 will become too deep, and an embossed pattern will easily appear on the label surface (printed side) after pasting, and the embossed pattern will appear even on the printed side of the pasted label (orange peel). to facilitate the occurrence of Furthermore, if the above range is exceeded, the grooves of the recesses 6 become too shallow, resulting in insufficient volume for sealing in gas and air, and the effect of preventing blisters is reduced. Furthermore, if the temperature exceeds the above range, some low-melting point resins may stick to the roll due to insufficient cooling during embossing, resulting in processing problems. The number of lines per inch is called the number of lines, and is a measure of the fineness or roughness of the embossed pattern. In the present invention, it is important that such an embossed pattern is a reverse gravure type pattern. The depth (h) of the valley of the embossed pattern is suitably 1/3 or more of the wall thickness (ho) of the heat-sealing resin layer, preferably 1
/2 or more, and may dig into the base material layer (h>h
o). As shown in 2, by stretching the laminated structure film embossed with a reverse gravure type pattern, the thickness of the laminated structure film is reduced, and as the embossed pattern is widened, the depth of the embossed valleys is also shallowed. Then, the surface area S of the convex portion 5 is 50 to 90% of the area of the entire label from the center line (h/2 position) L of the amplitude of the uneven peaks (twill) 5 and valleys 6 on the film surface after horizontal stretching. Preferably, it accounts for 55 to 80%, and furthermore, the average depth L1 of the concave portion is 0.5 to 10 μm, preferably 1 to 8 μm from the center line. The surface area of the above convex portion is 5
If it is less than 0%, blisters are likely to occur, and 90%
%, the adhesive strength decreases. Furthermore, if the average depth of the four parts is less than the above range, blisters are likely to occur, and if it exceeds the above range, the adhesive strength will decrease. In addition, the surface Bekk smoothness (J
l5-P8119) is 20 to 800 seconds, preferably 30
~400 seconds, and the average surface roughness (Ra) is preferably O75 ~ 5 μm from the viewpoint of adhesive strength. Since the in-mold label of the present invention is configured as described above, especially since it is formed in a reverse gravure type,
The unevenness on the surface of the adhesive layer 4 of the stretched film increases the area S of the convex portion 5 above the center line, and also increases the adhesive area when adhering to a low melting point resin, thereby increasing the strength per unit area. can be significantly increased. Furthermore, since it is a reverse gravure type, it is possible to reduce the accumulation of gas or air in one place under high temperature molding conditions, and to prevent the occurrence of blisters by dispersing and sealing it into many recesses 6. [m] Adhesion In the in-mold label of the present invention, after the label is installed in the cavity of a mold so that the printed side is in contact with the mold wall surface, it is fixed to the mold inner wall by the suction of the mold, and then the container is molded. A molten sheet of resin material is introduced into a mold and molded in a conventional manner to form a container with a label fused to the outer wall of the container. In containers molded in this way, the label and resin container are molded together after the label is fixed in the mold, so there is no deformation of the label and the adhesion between the container body and the label is strong. The container does not have any blisters and has a good appearance decorated with a label.

[Experiment example]

Example 1 Production of in-mold label Melt flow rate (MFR) 0.8, 70% by weight of homopolypropylene with a melting point of 164°C, 12% by weight of high-density polyethylene with a melting point of 134°C, and heavy carbonic acid with an average particle size of 1.5 μm. 18% by weight of calcium was blended (A), kneaded in an extruder set at 270°C, extruded into a sheet,
It was cooled using a cooling device to obtain a non-stretched sheet. Next, this sheet was heated to 145° C. and then stretched 5 times in the machine direction to obtain a 5 times stretched sheet in the machine direction (layer A). On the other hand, 58% by weight of homopolybrobylene with MFR of 4.0
A mixture (B) of 42 wt.
After melting and kneading at a temperature of 0°C, it is supplied to a die of -
After laminating (B layer-0 layer) within the die, this laminate (B
Layer C (layer C) is extruded into a film form through a die, extruded onto the back side of the sheet stretched 5 times in the longitudinal direction of layer A so that the 0 layer is on the outside, and passed through an embossing roll consisting of a metal roll and a rubber roll. A reverse gravure type pattern having dots at 0.3 mm intervals (80 lines) and a valley depth of 30 μm was embossed on the C layer side of the laminated film. On the other hand, the mixture of (B) above was laminated on the surface side of the sheet of layer A to form a paper-like layer (layer B) to obtain a four-layer laminated film. Next, this laminated film was reheated to about 155°C, stretched 7 times in the transverse direction, and then the paper-like layer (layer B) was subjected to corona discharge treatment, and then cooled to 55°C, Slit the ears and make (B)/ (A)/ (B)/
The thickness of each layer of (C) is 30/70/30/1, respectively.
A synthetic paper with a four-layer structure of 0 μm was obtained. After performing offset printing on the paper-like layer (layer B) side of this synthetic paper, this was further punched to obtain an in-mold label 1 (width: 60 mm, length: 110 mm). The surface structure of the embossed reverse gravure pattern on the surface of layer (C) of this label was measured and drawn using a surface roughness meter (Surfcorder 5E-30 manufactured by Koita Research Institute), and the results revealed that the unevenness of the surface was The surface area S of the convex part that protrudes from the center line, which is between the amplitudes of peaks 5 and troughs 6, is 65% of the entire label.
, and the average depth of the recesses 6 recessed from the center line is 6 μm, the Beck smoothness is 30 seconds, and the average surface roughness (Ra) is 1. 21℃m, J I 5-P
The Dever hardness measured by the method of No. 8125 was 1.8 g in the MD force direction and 3.5 g in the TD force direction. Adhesion After fixing this in-mold label 1 to one of the split molds for blow molding using a vacuum so that the printed side (layer B) is in contact with the mold, a parison of high-density polyethylene (melting point 134°C) is attached. was melt-extruded at 155°C (low-temperature parison) and 205°C (high-temperature parison), then the split molds were clamped, and 4.2 kg/cd of compressed air was supplied into the parison to engrave the parison into a container shape. At the same time, the mold was fused to an in-mold label, and then, after cooling the mold, the mold was opened and the hollow container was taken out. In this hollow container, there was no fading of the print, and no label shrinkage or blister formation was observed. In addition, even though 100 labels were continuously fed to the split mold for blow molding using the automatic label feeding device, there was not a single mistake (such as a label falling out of the mold). Furthermore, Table 1 shows the results of measuring the adhesive strength and orange peel of the label when melt-extruded using the above-mentioned low-temperature parison and high-temperature parison. , Examples 2 to 6 and Comparative Example 1
~5 It was carried out in the same manner as in Example 1 except that the structure of the in-mold label was changed to the structure shown in Table 1. The results are shown in Table 1. The evaluation was performed based on the criteria shown below. The blister label was classified into the following 5 stages depending on the state of adhesion of the label. 5: Fully adhesive 4 Less than 100% to 90% of the label is adhered. 3 Less than 90% to 70% of the labels are stuck. Less than 7096 to 50% of the 2 labels are stuck. 1 Less than 50% of the labels stick. Label Adhesive Strength The adhesive strength (T-peel) of the adhesive label with a width of 15 mm was measured. Orange beer did not cause orange peel. △Ni-orange peel is slightly visible. ×The orange peel is noticeable. In addition, the surface structure of the layer (C) before and after horizontal stretching in Example 2 and Comparative Example 2 was measured using a mold using a surfcorder 5E-30 manufactured by Koita Research Institute.
It is shown as FIGS. 5 to 8. FIG. 5 is a diagram showing the surface of a film on which a 100-line inverted trapezoidal gravure embossing of the present invention is formed, and FIG.
It is a figure showing the film surface after transversely stretching the film of the figure. Moreover, FIG. 7 is a diagram showing the surface of a film on which a conventional 100-line regular trapezoidal gravure emboss has been formed, and FIG. 8 is a diagram showing the surface of the film after the film of FIG. 7 is laterally stretched. Moreover, FIGS. 9 to 11 are diagrams showing the surface layer film thickness and surface morphology at the 100 line of Example 2 of the present invention, and FIGS.
The figure shows the surface morphology of a film with a thickness of 2 μm, FIG. 10 with a film thickness of 4 μm, and FIG. 11 with a film thickness of 6 μm. Furthermore, FIGS. 12 to 14 show 150 of Embodiment 4 of the present invention.
These are diagrams showing the surface layer film thickness and surface morphology along the line, where the film thickness in Fig. 12 is 2 μm, and the film thickness in Fig. 13 is 4 μm;
Figure 4 shows the surface morphology of a film with a thickness of 6 μm.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view of the in-mold label of the present invention having a two-layer structure, FIG. 2 shows a plan view of the back side of the in-mold label, and FIG. 4 is a partially enlarged view of the laminated structure film shown in FIG. 3. FIG. 4 is a partially enlarged view of the laminated structure film shown in FIG. 3. FIG. 5 is a diagram showing the surface of a film on which a 100-line inverted trapezoidal gravure emboss is formed according to an example of the present invention, and FIG. 6 is a diagram showing the surface of the film after the film of FIG. 5 is laterally stretched. Moreover, FIG. 7 is a diagram showing the surface of a film on which a conventional 100-line regular trapezoidal gravure emboss is formed.
The figure shows the surface of the film after the film shown in Fig. 7 is laterally stretched, and Figs. 9 to 11 show the surface morphology of Example 2 of the present invention at a surface layer thickness of 2 to 6 μm at the 100 line. FIG. 12 to FIG. 14 are diagrams representing Embodiment 4 of the present invention.
It is a figure showing the surface form in the surface layer film thickness of 2-6 micrometers on the 150th line. 1 Label for coin mold 2: Thermoplastic resin film base material layer 3: Printing 4, heat-sealable resin layer 5: Top of twill (convex portion) given a dot-like lattice pattern by embossing 6: A lattice pattern Valley (concave) L: Center line Ll: Area of convex above the average depth SQL of concave

Claims (1)

[Claims] An in-mold label obtained by embossing a reverse gravure pattern on a resin film with a roll number of 80 to 200 lines/inch and then stretching the film, The surface area of the convex portion above the center line of the amplitude of the peaks and valleys of the unevenness on the surface of the embossed side of the film accounts for 50 to 9 of the surface area of the label.
0%, and the average depth of the concave portion below the center line is 0.5 to 10 μm.