Patent Application
20200086657
The present invention relates to a label and, in particular, a label having a water-based ink layer.
Labels such as shrinkable labels are attached to containers such as PET bottles to provide a product name, a graphical pattern, a manufacturer name, a logotype, a product description, and the like. A print layer is formed on the labels to provide a product name, a graphical pattern, and the like. For example, Patent Literature 1 discloses a heat shrinkable label, wherein at least one surface of a heat shrinkable film is printed with a water-based ink, and a topcoat layer composed of a water-resistant or alkali-resistant resin is formed on the surface of a water-based ink layer.
Patent Literature 1: Japanese Patent Laid-Open No. 2001-296805
When a water-based ink layer is formed by directly applying a water-based ink on a base material film made of a synthetic resin that constitutes a label, it is assumed that the ink is repelled and an ink layer cannot be formed over the entirety of the target zone, thus resulting in the problem of a poor label appearance. This problem is more noticeable when the water-based ink has a greater water content. It is possible to improve the wettability of the label base material by treating the surface of the label base material by corona discharge or the like; however, in this case, blocking of the label base material may occur, which makes it difficult to handle the label base material. Also, it can be considered to perform a corona discharge treatment on the label base material immediately before applying the water-based ink, but the corona discharge treatment may not always be employed from the safety viewpoint of the manufacturing process.
An object of the present invention is to improve the appearance of a label obtained by directly forming a water-based ink layer on a label base material, without performing a special surface treatment on the label base material.
A label, which is one aspect of the present invention, comprises a label base material having a dyne level of 40 mN/m or less; a water-based ink layer directly formed on the label base material and having a halftone dot reproducibility of 50 to 95%; a first solvent-based ink layer formed above the label base material so as to cover the water-based ink layer; and a second solvent-based ink layer formed above the label base material so as to cover the water-based ink layer and the first solvent-based ink layer.
A method for manufacturing a label, which is one aspect of the present invention, comprises the steps of providing a label base material having a dyne level of 40 mN/m or less; directly forming a water-based ink layer having a halftone dot reproducibility of 50 to 95% on the label base material by using a water-based ink having a water content in a solvent of 90% to 100%; forming a first solvent-based ink layer above the label base material so as to cover the water-based ink layer; and forming a second solvent-based ink layer above the label base material so as to cover the water-based ink layer and the first solvent-based ink layer.
According to one aspect of the present invention, it is possible to improve the appearance of a label obtained by directly forming a water-based ink layer on a label base material, without performing a special surface treatment on the label base material. In the label according to the present invention, since the dyne level of the label base material is low, the ink is repelled and the water-based ink layer is not formed on the entirety of the target zone on the label base material; however, provision of the first solvent-based ink layer and the second solvent-based ink layer makes it possible to prevent the color loss of a zone where the water-based ink layer is formed and clearly show characters, graphical patterns, background colors, and the like on the label.
That is, when the water-based ink is repelled on the label base material, the halftone dot reproducibility of the water-based ink layer is lowered and, accordingly, the irregularities (the thickness variation) of the water-based ink layer increases. It is thus difficult to uniformly apply an ink to the back side of the water-based ink layer. Accordingly, in the label according to the present invention, the first solvent-based ink layer is provided on the back side of the water-based ink layer to mitigate the influence of the irregularities, and the back side of the water-based ink layer is completely covered by the second solvent-based ink layer. It is thus possible to clearly show characters, graphical patterns, background colors, and the like on the label.
Below, one embodiment according to the present invention is described in detail in reference to the drawings, but the application of the present invention is not limited to the embodiment described below. The drawings referred to in the embodiment are schematic, and thus the dimensional ratios and the like of the components depicted in the drawings should be determined in view of the following description.
Herein, when the label is attached to the attachment target such as a container, the surface of the label facing the attachment target side is referred to as the “back surface,” and the surface on the opposite side to the back surface is referred to as the “front surface.” Regarding the components of the label as well, the positional relationship is described using the terms “front” and “back.” As for a cylindrical label obtained by forming the label into a cylindrical shape, the back surface of the label is the inner surface facing the inside of the cylinder. Herein, the “edge” when described in reference to a printing zone means a portion located at the end of the printing zone, and the “end part” means the edge of the printing zone and the vicinity thereof.
While labels 10 and 10A that are shrinkable labels having heat shrinkability are exemplified below, the configuration of the label according to the present invention is also applicable to, for example, a wrap around label, a stretchable label, and a tack label that do not have heat shrinkability.
The label 10 comprises a solvent-based ink base layer 14 (a first solvent-based ink layer) formed above the label base material 11 so as to cover the water-based ink layer 13, and a solvent-based ink cover layer 15 (a second solvent-based ink layer) formed above the label base material 11 so as to cover the water-based ink layer 13 and the solvent-based ink base layer 14. Preferably, the label 10 further comprises a solvent-based ink layer 12 (a third solvent-based ink layer) directly formed on the label base material 11.
The solvent-based ink layer 12 and the water-based ink layer 13 are print layers for showing a product name, a graphical pattern, a manufacturer name, a logotype, a product description, or the like. As will be described in detail below, the water-based ink layer 13 may be a heat sensitive print layer containing heat sensitive capsules. On the other hand, the solvent-based ink base layer 14 and the solvent-based ink cover layer 15 function especially as print layers for preventing damage to the water-based ink layer 13, i.e., protective layers, and also as print layers for improving the appearance of the water-based ink layer 13.
The label 10 may be formed into a rectangular shape, an elliptical shape, a circular shape, a polygonal shape other than a rectangular shape, or a shape, the edge of which has a wavy shape or the like, as viewed from above. The shape of the label 10 is determined by the shape of the label base material 11 that functions as a support for each of the above print layers. The label base material 11 is a shrinkable base material having heat shrinkability, and generally heat shrinkage in one direction differs from that in a direction perpendicular to that direction. The label base material 11 has, for example, a rectangular shape as viewed from above, and the long side direction (the circumferential direction when the label is attached to a container) is the main shrinking direction. Herein, the term “as viewed from above” means a state when the label 10 (the label base material 11) is observed perpendicularly to the front or back surface thereof.
The solvent-based ink layer 12 is formed on the back surface of the label base material 11 excluding the end part of the label base material 11 and a window zone Z described below. The end part along one short side of the label base material 11 has an exposed zone where the back surface of the label base material 11 is exposed, and the exposed zone is provided so as to be broader than the exposed zone of another end part. Hereinafter, this broad exposed zone is referred to as an exposed zone 18. For example, the label 10 is formed into a cylindrical shape with the long side direction being the circumferential direction of a cylinder, and a joined part is formed in the exposed zone 18 (see
On the label base material 11, the window zone Z is provided that is surrounded by a zone where the solvent-based ink layer 12 is formed (hereinafter referred to as a “zone Z12”). That is, an edge E12 of the zone Z12 that serves as the edge of the window zone Z is formed in an annular shape. The window zone Z does not have the solvent-based ink layer 12 but has the water-based ink layer 13, and the window zone Z serves as a zone where characters, graphical patterns, or the like shown by the water-based ink layer 13 are visible on the front side of the label 10 without being hidden by the solvent-based ink layer 12. In the example shown in
The shape, arrangement, and size of the window zone Z are not limited to those shown in
The water-based ink layer 13 is provided in an annular shape having a predetermined width on the back side of the solvent-based ink layer 12, and the entirety of an edge E13 of a zone where the water-based ink layer 13 is formed (hereinafter referred to as a “zone Z13”) is disposed on the back side of the solvent-based ink layer 12 (the zone Z12) With the edge E13 overlapping the back side of the zone Z12, the edge E13 can be less noticeable. The water-based ink layer 13 may be formed in a place other than the window zone Z, and, for example, the water-based ink layer 13 may be formed in a zone that is not surrounded by the zone Z12, such as the vicinity of the end part of the label base material 11.
The solvent-based ink base layer 14 is formed on the back surface side of the label base material 11 so as to cover the water-based ink layer 13. The solvent-based ink base layer 14 covers at least part of the water-based ink layer 13, and is preferably formed so as to cover 50% or more and more preferably 70% or more of the water-based ink layer 13. In other words, there may be a portion where the solvent-based ink base layer 14 is not present on the back side of the water-based ink layer 13. The solvent-based ink base layer 14 is preferably formed in a range such that the solvent-based ink base layer 14 overlaps the water-based ink layer 13 in the thickness direction of the label 10 and in the vicinity of the range, and part of the solvent-based ink base layer 14 may be directly formed on the solvent-based ink layer 12 or on the label base material 11. The solvent-based ink base layer 14 may be formed in a broad range over the back surface of the label base material 11 so as to greatly exceed the range where the solvent-based ink base layer 14 and the water-based ink layer 13 overlap.
The solvent-based ink cover layer 15 is formed on the back surface side of the label base material 11 so as to cover the water-based ink layer 13 and the solvent-based ink base layer 14. The solvent-based ink cover layer 15 is preferably formed in a range such that the solvent-based ink cover layer 15 overlaps the water-based ink layer 13 in the thickness direction of the label 10 and in the vicinity of the range, and part of the solvent-based ink cover layer 15 may be directly formed on the solvent-based ink layer 12 or the label base material 11. For example, the solvent-based ink cover layer 15 is formed on the solvent-based ink base layer 14 and is also formed on the water-based ink layer 13 not covered by the solvent-based ink base layer 14. That is, the solvent-based ink cover layer 15 is formed on the back side of the water-based ink layer 13 so as to cover the entirety of the water-based ink layer 13.
The solvent-based ink cover layer 15 is preferably an opaque print layer, and prevents the color loss of the zone Z13 where the water-based ink layer 13 is formed. By providing the solvent-based ink cover layer 15, characters, graphical patterns, background colors, or the like on the label can be clearly shown. The color of the solvent-based ink cover layer 15 may be either an achromatic color such as white or a chromatic color such as red, blue, yellow, or green. By forming an opaque solvent-based ink cover layer 15, the design on the label can be clearly shown without being affected by, for example, the color of a container or the color of a liquid with which the container is filled, when the label 10 is attached to the container. The solvent-based ink cover layer 15 may be formed in a broad range over the back surface of the label base material 11 so as to exceed the range where the solvent-based ink cover layer 15 overlaps the solvent-based ink layer 12. The solvent-based ink base layer 14 may be colorless and transparent, may have an achromatic color such as white, or may have a chromatic color such as red, blue, yellow, or green.
The joined part 31 is formed by, for example, bonding using a solvent such as tetrahydrofuran (THF), and may also be formed using an adhesive. An adhesive tape may be attached over the outer surfaces of the inner end part 32 and the outer end part 33 to thereby join both end parts. In the example shown in
The label 10A constituting the cylindrical label 30 is different from the label 10 in that the water-based ink layer 13 is formed over a broad range on the label base material 11 as far as the inner surface of the outer end part 33 that overlaps the inner end part 32. In the case where the water-based ink layer 13 is present on the inner surface of the outer end part 33, it is assumed that, for example, when high-temperature steam is used to thermally shrink the cylindrical label 30, a softened water-based ink layer 13 is brought into contact with the inner end part 32, and thus the ink layer is cracked, resulting in a poor appearance. In order to address such a problem, a curing agent may be added to at least one of the solvent-based ink base layer 14 and the solvent-based ink cover layer 15 to cure the coating film. In
Below, the components of the label 10 are described in further detail.
The label base material 11 is, for example, a shrinkable base material having heat shrinkability and is preferably composed of a colorless, transparent shrinkable film. However, the label base material 11 is not limited to a shrinkable base material, and may be an unstretched base material having substantially no heat shrinkability, a stretchable base material having a stretchable and non-shrinkable base material, or the like. For example, when the label 10 is a wrap around label, an unstretched film or a non-shrinkable film is applicable to the label base material 11, and when the label 10 is a stretchable label, a stretchable film having stretchability is applicable to the label base material 11.
The type of the resin constituting the label base material 11 can be suitably selected according to the required physical properties, application, cost, and the like, and examples include, but are not particularly limited to, resins such as polyester resins, polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyamide resins, and acrylic resins. In particular, polyester resins, polyolefin resins, and polystyrene resins are preferable. These resins may be used singly, or in combinations of two or more. The resin film constituting the label base material 11 may be a single layer film or a laminated film obtained by laminating the same or different type of resins.
Polyester resins usable in the polyester film may be a polyethylene terephthalate (PET) resin, poly(ethylene-2,6-naphthalenedicarboxylate) (PEN), and polylactic acid (PLA). In particular, a PET resin is preferable. Examples of the polyolefin resins usable in the polyolefin film include polyethylene resins such as low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and metallocene catalyst LLDPE (mLLDPE), polypropylene resins such as polypropylene and propylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, and cyclic olefin resins. Examples of the polystyrene resins usable in the polystyrene film include polystyrene, styrene-butadiene-styrene copolymers (SBS), styrene-butadiene/isoprene-styrene copolymers (SBIS), and styrene-acrylate copolymers.
The dyne level of the label base material 11 is 40 mN/m or less and may be 38 mN/m or less. The dyne level of the label base material 11 is, for example, 30 to 40 mN/m or 35 to 38 mN/m. When the label base material 11 is composed of a polyolefin film, the dyne level is about 40 mN/m, and when the label base material 11 is composed of a polystyrene film, the dyne level is about 38 mN/m. When the dyne level of the label base material 11 is 40 mN/m or less and in particular 38 mN/m or less, the wettability with water is reduced and the water-based ink is likely repelled, thus making it difficult to form the water-based ink layer 13 in the entirety of the target zone. The dyne level of the label base material 11 is measured in accordance with JIS K 6768.
When the label base material 11 is a shrinkable film, the film is preferably a film oriented in at least one direction from the viewpoint of exerting good shrink characteristics. The label base material 11 thermally shrinks mainly in the orientation direction of the shrinkable film. A preferably used shrinkable film is a uniaxially oriented film oriented in one direction (including a film stretched substantially in one direction, which is mainly stretched in one direction and slightly stretched in a direction perpendicular to that direction) or a biaxially oriented film. The oriented film is obtained by stretching an unstretched film in at least one direction by, for example, a tenter method, a roll method, or a tube method.
The heat shrinkage in the main shrinking direction of the shrinkable film is, for example, preferably 30 to 90%, more preferably 40 to 85%, and particularly preferably 45 to 80% under conditions involving immersion in hot water at 90° C. for 10 seconds. The heat shrinkage in the direction perpendicular to the main shrinking direction of the shrinkable film (immersed in hot water at 90° C. for 10 seconds) is not particularly limited, and is preferably −3 to 15% and more preferably −1 to 10%. The thickness of the shrinkable film is not particularly limited, and is preferably 10 μm to 100 μm, more preferably 15 μm to 80 μm, and particularly preferably 20 μm to 60 μm.
The solvent-based ink layer 12 is a print layer for showing a product name, a graphical pattern, a manufacturer name, a logotype, a product description, or the like, and is formed in any print pattern. The print pattern means a design such as characters or graphical patterns, and the arrangement of the design. The solvent-based ink layer 12 can be formed by a conventionally known printing method such as a gravure printing method, a flexographic printing method, a rotary letterpress printing method, or a screen printing method. The plate printing method is a printing method involving a plate prepared in accordance with the characters, graphical patterns, or the like of a print layer. For example, an intaglio printing plate is used in the gravure printing method, a relief printing plate is used in the flexographic printing method and the rotary letterpress printing method, and a permeographic printing plate is used in the screen printing method.
The solvent-based ink layer 12 contains, for example, a coloring material and a binder resin, and may contain various additives. The solvent-based ink layer 12 can be formed using a conventionally known solvent-based ink. The solvent-based ink is also called a solvent type ink, and contains, for example, a coloring material, a binder resin, an optional additive, and an organic solvent, in which the binder resin and the coloring material are dissolved or dispersed in the solvent. In the state of the solvent-based ink layer 12 (the same applies to other solvent-based ink layers), the organic solvent is evaporated. Generally, the solvent-based ink layer 12 is soluble in an organic solvent and insoluble even when exposed to an aqueous solvent.
The color (hue, lightness, saturation) of the solvent-based ink layer 12 can be suitably set according to the design such as characters and graphical patterns, and examples include red, yellowish red, yellow, yellowish green, green, bluish green, blue, bluish purple, purple, reddish purple, metallic color (such as silver color or gold color), and pearl color. The color of the solvent-based ink layer 12 may be white, black, or gray (achromatic). The solvent-based ink layer 12 forms characters, graphical patterns, or the like by, for example, one print layer containing one coloring material or by a combination of two or more print layers containing mutually different coloring materials.
The coloring material contained in the solvent-based ink layer 12 is not particularly limited as long as the color desired according to the design such as characters and graphical patterns can be provided, and conventionally known dyes and pigments are usable. Specific examples of the coloring material include cyan pigments (such as copper phthalocyanine blue, ultramarine blue, and Prussian blue), magenta pigments (such as condensed azo pigments and red lead), yellow pigments (such as azo lake pigments, yellow lead, and zinc yellow), and black pigments (such as carbon black and titanium black). By each of the cyan (C), magenta (M), yellow (Y), and black (K) pigments, or by combining two or more of these, the above various colors can be provided. Metal pigments, pearl pigments, and extender pigments such as alumina, calcium carbonate, and barium sulfate may be used.
Examples of the binder resin contained in the solvent-based ink layer 12 include one or a mixture of two or more selected from acrylic resins, polyurethane resins, polyester resins, cellulose resins, polyamide resins, polyolefin resins, polyvinyl chloride resins, polyvinyl acetate resins, and vinyl chloride-vinyl acetate copolymer resins. In particular, acrylic resins, polyurethane resins, and cellulose resins are preferable.
The solvent-based ink layer 12 is formed by, for example, applying the desired printing ink in the form of a large number of dots to the label base material 11, and the color and in particular the light and dark shading or the like of the solvent-based ink layer 12 are shown according to the size of the dots and the dot area per unit area of the label base material 11. The dot is generally called a halftone dot. The density, size, and the like of the halftone dots of the printing ink can be regulated by changing the irregularity pattern of the plate. The halftone dot reproducibility in the solvent-based ink layer 12 is, for example, about 100%. The thickness of the solvent-based ink layer 12 is not particularly limited, and is preferably 0.1 μm to 5 μm.
Below, the water-based ink layer 13, the solvent-based ink base layer 14, and the solvent-based ink cover layer 15 are described in detail with reference to
The water-based ink layer 13, as with the solvent-based ink layer 12, is a print layer for showing a product name, a graphical pattern, a manufacturer name, a logotype, a product description, or the like, and is formed in any print pattern. The water-based ink layer 13 can be formed by a conventionally known printing method such as a gravure printing method (the same applies to the solvent-based ink base layer 14 and the solvent-based ink cover layer 15). The water-based ink layer 13 contains, for example, a coloring material and a binder resin, and may contain various additives.
The water-based ink layer 13 can be formed using a conventionally known water-based ink. The water-based ink contains, for example, a coloring material, a binder resin, an optional additive, and an aqueous solvent, in which the binder resin and the coloring material are dissolved or dispersed in the aqueous solvent. The aqueous solvent is a solvent mainly composed of water, and the proportion of water is preferably 90% to 100%, and more preferably 95% to 100%. In the state of the water-based ink layer 13, the aqueous solvent is evaporated. Generally, the water-based ink layer 13 is dissolved in or swollen by the aqueous solvent.
The color (hue, lightness, saturation) of the water-based ink layer 13, as with the solvent-based ink layer 12, can be suitably set, and examples include red, yellowish red, yellow, yellowish green, green, bluish green, blue, bluish purple, purple, reddish purple, metallic color (such as silver color or gold color), and pearl color. The color of the water-based ink layer 13 may be white, black, or gray (achromatic). The water-based ink layer 13 forms characters, graphical patterns, or the like by, for example, one print layer containing one coloring material or by a combination of two or more print layers containing mutually different coloring materials.
The coloring material contained in the water-based ink layer 13 is not particularly limited as long as the color desired according to the design such as characters and graphical patterns can be provided, and conventionally known dyes and pigments are usable. Specific examples of the coloring material include the above cyan pigments, magenta pigments, yellow pigments, and black pigments. Metal pigments, pearl pigments, and extender pigments such as alumina, calcium carbonate, and barium sulfate may be used.
The water-based ink layer 13 may contain microcapsules such as heat sensitive capsules as a coloring material. The heat sensitive capsules are a coloring material, the color of which changes according to the temperature change. For example, the heat sensitive capsules are colorless at a predetermined temperature or higher and develop a color at a temperature below the predetermined temperature, or are colorless at a predetermined temperature or lower and develop a color at a temperature exceeding the predetermined temperature. The water-based ink layer 13 may be colorless when the temperature of the layer is at a predetermined temperature or higher and develop a color when the temperature of the layer is lower than the predetermined temperature, e.g., may be colorless at normal temperature (25° C.) and develop a color at a temperature of 10° C. or lower. That is, when a bottle to which the label 10 is attached is cooled, the design appears due to the heat sensitive print layer. Also, the water-based ink layer 13 may be colorless when the temperature of the layer is at a predetermined temperature or lower and develop a color when the temperature of the layer exceeds the predetermined temperature, e.g., may be colorless at normal temperature and develop a color at a temperature of 50° C. or higher. That is, when a bottle to which the label 10 is attached is heated, the design appears due to the heat sensitive print layer. Provision of such a heat sensitive print layer makes it possible to impart to the label 10 the function to indicate when to eat, when to drink, or the like. The heat sensitive capsules contained in the water-based ink layer 13 may be irreversible heat sensitive capsules, the color change of which is irreversible, and are preferably reversible heat sensitive capsules, the color change of which is reversible. Examples of reversible heat sensitive capsules include microcapsules of a leuco dye, a color developer, and a solvent. In this case, microcapsules develop a color when the leuco dye and the color developer are in a bonded state in which electrons are donated to and accepted from each other, and microcapsules are colorless when the leuco dye and the color developer are in a non-bonded state in which electrons are neither donated nor accepted. The temperature of color development can be changed by changing the type of solvent. The heat sensitive capsules may be colorless when in the bonded state and develop a color when in the non-bonded state. Heat sensitive capsules in which a leuco dye is used easily collapse and become deactivated in an organic solvent, and therefore the configuration of the label 10 is suitable when such heat sensitive capsules are directly provided on the label base material 11. The water-based ink layer 13 may contain aroma capsules or the like as a coloring material. The water-based ink layer 13 may contain irreversible heat sensitive capsules that are colorless at normal temperature (25° C.) and develop a color at a temperature of 50° C. or higher. In this case, once exposed to a specific temperature range (for example, 50° C. or higher), the heat sensitive print layer remains colored, thus making it possible to detect exposure to the specific temperature range.
In the case where the water-based ink layer 13 is a heat sensitive print layer containing heat sensitive capsules, the solvent-based ink base layer 14 is an opaque print layer or a colorless, transparent print layer, and the solvent-based ink cover layer 15 is an opaque print layer, a design is shown by at least the solvent-based ink cover layer 15 when the heat sensitive print layer does not develop a color. On the other hand, when the heat sensitive print layer develops a color, the background color of the heat sensitive print layer is provided by the solvent-based ink cover layer 15 or the like such that the heat sensitive print layer appears attractive. In particular, in the case where the solvent-based ink base layer 14 is a white print layer or a colorless, transparent print layer, and the solvent-based ink cover layer 15 is a white print layer, a white design is shown by at least the solvent-based ink cover layer 15 when the heat sensitive print layer does not develop a color. On the other hand, when the heat sensitive print layer develops a color, the background color of the heat sensitive print layer is provided by the solvent-based ink cover layer 15 or the like such that the heat sensitive print layer appears attractive. That is, the colored heat sensitive print layer is clearly shown. The solvent-based ink base layer 14 is preferably an opaque print layer containing the same coloring material as that of the solvent-based ink cover layer 15 (a print layer having the same color as the solvent-based ink cover layer 15) or a colorless, transparent print layer. When the solvent-based ink base layer 14 is an opaque print layer, the design and the background color are provided by both the solvent-based ink base layer 14 and the solvent-based ink cover layer 15.
The average particle size of the heat sensitive capsules is, for example, 0.1 μm to 5 μm. Herein, the average particle size means a volume average particle size as measured by a laser diffraction method and a median size at which the volume integrated value is 50% in the particle size distribution. The function of the heat sensitive capsules is easily deteriorated by organic solvents. Accordingly, when the heat sensitive capsules are used, the water content in the solvent of a water-based ink that forms the water-based ink layer 13 is preferably 90% to 100%, and more preferably 95% to 100%.
As with the solvent-based ink layer 12, examples of the binder resin contained in the water-based ink layer 13 include acrylic resins, polyurethane resins, polyester resins, and cellulose resins, but unlike the binder resin of the solvent-based ink layer 12, which is lipophilic, the binder resin of the water-based ink layer 13 is hydrophilic. The binder resin of the water-based ink layer 13 has a hydrophilic group such as a hydroxyl group or an amine-neutralized carboxy group, or is hydrophilized by a surfactant. The binder resin of the water-based ink layer 13 generally has a greater molecular weight than the binder resin of the solvent-based ink layer 12. For example, the weight average molecular weight (Mw) of the binder resin of the solvent-based ink layer 12 is less than 100000 (preferably less than 50000), whereas the weight average molecular weight of the binder resin of the water-based ink layer 13 is 100000 or more.
As shown in
The halftone dot reproducibility of the water-based ink layer 13 is 50 to 95%, 75 to 95%, or 50 to 70%. That is, as for the target zones of the halftone dots 20 indicated by dotted lines in
The shape of the target zones of the halftone dots 20, i.e., the shape of holes in the printing plate, is not particularly limited, and may be a perfectly circular shape, an elliptical shape, a rectangular shape, or the like. As shown in
As shown in
The solvent-based ink base layer 14 may be colorless and transparent because the solvent-based ink base layer 14 is provided to fill up the gap between the adjacent halftone dots 20, mitigate the influence of different thicknesses of the halftone dots 20, and thus cause all halftone dots 20 to be covered by the solvent-based ink cover layer 15. The solvent-based ink base layer 14 may be composed solely of a binder resin. Alternatively, the solvent-based ink base layer 14 may contain the same coloring material as that of the solvent-based ink cover layer 15, such as a white pigment. Also, the solvent-based ink base layer 14 may contain the same coloring material as that of the water-based ink layer 13.
Configuring the solvent-based ink base layer 14 to be a colorless, transparent print layer and the solvent-based ink cover layer 15 to be an opaque print layer (for example, a white print layer) makes it possible to smooth the irregularities of the water-based ink layer to a suitable extent by the colorless solvent-based ink base layer 14 and securely cover the back side of the water-based ink layer by the colored solvent-based ink cover layer 15, thus enabling the background color and the like on the label to be clearly shown.
The solvent-based ink base layer 14 can be formed using a conventionally known solvent-based ink. Generally, the solvent-based ink base layer 14 is soluble in an organic solvent and insoluble even when exposed to an aqueous solvent. As in the case of the solvent-based ink layer 12, one or a mixture of two or more selected from acrylic resins, polyurethane resins, polyester resins, cellulose resins, polyamide resins, polyolefin resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins, and the like is usable as the binder resin of the solvent-based ink base layer 14. For the solvent-based ink cover layer 15 as well, the same binder resins are usable, and the solvent-based ink base layer 14 and the solvent-based ink cover layer 15 may be composed of the same type of binder resin.
At least one of the solvent-based ink base layer 14 and the solvent-based ink cover layer 15 may contain a curing agent component as described above. For example, a curing agent may be added to the solvent-based ink that forms the solvent-based ink cover layer 15 and, in this case, the curing agent and the functional group of the binder resin react to cure the coating film. The curing agent may react with the functional groups of the resins constituting the solvent-based ink base layer 14, the water-based ink layer 13, the solvent-based ink layer 12, and the label base material 11, and the entirety of the print layers may be cured. When the print layers such as the solvent-based ink cover layer 15 is cured, the strength of the coating film increases, thus making it possible to prevent cracking of the water-based ink layer 13 and the like during heat shrinking.
Examples of the curing agent include aziridine curing agents and carbodiimide curing agents. In particular, aziridine curing agents are preferable. Examples of aziridine curing agents include trimethylolpropane tris[3-(1-aziridinyl)propionate], trimethylolpropane tris[3-(1-(2-methyl)aziridinylpropionate)], N,N′-toluene-2,4-bis(1-aziridinecarboxide), N,N′-diphenylmethane-4,4′-bis(1-aziridinecarboxide), triethylenemelamine, bisisoprotaloyl-1-(2-methylaziridine), tri-1-aziridinyl phosphine oxide, tetramethylolmethane-tri-β-aziridinylpropionate, 2,2′-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], 1,6-hexamethylenediethyleneurea, N,N′-diphenylmethane-4,4′-bis(1-aziridinecarboxamide), and N,N′-hexamethylene-1,6-bis(1-aziridinecarboxamide).
The solvent-based ink base layer 14 may be composed of a plurality of halftone dots as in the water-based ink layer 13 or the like, and is preferably formed such that the coating film (halftone dots) is continuous so as to form a solid coating. The thickness of the solvent-based ink base layer 14 is, for example, 0.1 μm to 5 μm. The thickness of the solvent-based ink base layer 14 is not particularly limited, and the solvent-based ink base layer 14 is preferably formed so as to have a greater thickness than the average thickness of the water-based ink layer 13 in order to mitigate the irregularities of the water-based ink layer 13 and prevent the color loss.
As shown in
The coloring material contained in the solvent-based ink cover layer 15 may be the above cyan pigment, magenta pigment, yellow pigment, black pigment, or the like, or may be a white pigment such as titanium oxide. The solvent-based ink cover layer 15 can be formed using a conventionally known solvent-based ink. Generally, the solvent-based ink cover layer 15 is soluble in an organic solvent and insoluble even when exposed to an aqueous solvent. The same type of binder resin as that of the solvent-based ink base layer 14 is applicable. The solvent-based ink cover layer 15 may contain the above curing agent component.
The solvent-based ink cover layer 15 is preferably formed such that the coating film (halftone dots) is continuous so as to form a solid coating as in the solvent-based ink base layer 14. The thickness of the solvent-based ink cover layer 15 is, for example, 0.1 μm to 5 μm. The thickness of the solvent-based ink cover layer 15 is not particularly limited, and the solvent-based ink cover layer 15 is preferably formed so as to have a greater thickness than the average thickness of the water-based ink layer 13.
As described above, the label 10 with the above configuration has an improved appearance without performing a special surface treatment on the label base material 11. In the label 10, the dyne level of the label base material 11 is low, and thus the water-based ink layer 13 is not formed on the entirety of the target zones on the label base material 11. However, in the label 10, the solvent-based ink base layer 14 is provided to mitigate the irregularities of the water-based ink layer 13 and then the solvent-based ink cover layer 15 is formed, thus making it possible to prevent the color loss of the zone Z13 where the water-based ink layer 13 is formed and making it possible to clearly show characters, graphical patterns, background colors, and the like on the label.
One example of the method for manufacturing the label 10 comprises the steps of providing the label base material 11 having a dyne level of 40 mN/m or less; directly forming the water-based ink layer 13 having a halftone dot reproducibility of 50 to 95% on the label base material 11 by using a water-based ink having a water content in a solvent of 90% to 100%; forming the solvent-based ink base layer 14 above the label base material 11 so as to cover the water-based ink layer 13; and forming the solvent-based ink cover layer 15 above the label base material 11 so as to cover the water-based ink layer 13 and the solvent-based ink base layer 14. The “ink layer” refers to a layer composed of a solidified ink formed by performing printing with a conventionally known ink using a conventionally known printing method (such as gravure printing, flexographic printing, or rotary letterpress printing).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-118877 | Jun 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/022751 | 6/14/2018 | WO | 00 |
