JP2016120671A - Multilayer film for laser printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film for a laser printing, which uses paper as a base material, capable of obtaining printing excellent in visibility with less damage.SOLUTION: A multilayer film for a laser printing comprises: a paper base material layer 1; a coloring ink layer 2; and a pattern printing layer 3, they are stacked in this order. The pattern printing layer is an outermost surface layer of the film, and partially provided on the coloring ink layer, therefore there are an area B on which the coloring ink layer and the pattern printing layer are overlapped, and an area A on which there is only the coloring ink layer. The coloring ink layer develops color by radiation of laser beam of any one of green laser whose oscillation wavelength is 532 nm, fiber laser whose oscillation wavelength is 1090 nm, carbonic acid gas laser whose oscillation wavelength is 10600 nm, and YVOlaser or YAG laser whose oscillation wavelength is 1064 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multilayer film for laser printing that can be printed by a laser, a packaging material comprising the same, and a laser printing method.

  Conventionally, the surface of packaging materials used for packaging containers for pharmaceuticals, beverages, foods, etc., along with information common to products such as product name, product design, etc., as well as the manufacturing site, date of manufacture, expiration date, production manager, etc. Have been described. The former common information is printed on the packaging bag before the contents are sealed, but the latter is written by the nature when the contents are stored and sealed, and entered in a predetermined recording frame part on the outer surface of the bag. Is done.

  As the description method, printing is performed on the surface of the packaging material by ink jetting, or a separately printed label is attached. However, the mechanical printing method is not appropriate for packaging with an irregular surface or flexible packaging containing impact-sensitive contents. Inkjet printing requires that the oil-rich contents be printed on the printing part. There are problems such as disappearance and desorption by adhering to the surface and rubbing during handling and transportation.

  As a countermeasure, a printing method has been performed in which characters and symbols are drawn and written on the printing surface of the package by laser irradiation (Patent Document 1, etc.). However, this has a low print density and poor visibility. In addition, in order to obtain a sufficient printing density, it was necessary to strengthen the laser irradiation conditions, and the damage to the packaging material was large.

Further, when paper is used as a base material, a method of printing by scraping the surface with carbon dioxide (CO ₂ ) is used. However, this method causes great damage to the packaging material, and during processing. The resulting paper dust and fumes are a problem.

Japanese Patent Laid-Open No. 2007-217048

  Accordingly, the present invention provides a laser-printing multilayer film that solves the above-mentioned problems and is a laser-printing multi-layer film based on paper, and that provides a print with excellent visibility with little damage. And it aims at providing the laser printing method which obtains the printing excellent in visibility with little damage, without producing paper dust and smoke.

As a result of various studies, the inventor is a multilayer film for laser printing laminated in the order of a paper base layer, a coloring ink layer, and a pattern printing layer, and the pattern printing layer is the outermost layer of the film, In addition, it is partially provided on the color ink layer, so that there is an area where the color ink layer and the pattern printing layer overlap and an area only of the color ink layer, and the color ink layer oscillates. A multilayer film for laser printing, which develops color when irradiated with a laser beam of a green laser having a wavelength of 532 nm, a fiber laser having an oscillation wavelength of 1090 nm, a carbon dioxide gas laser having an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser having an oscillation wavelength of 1064 nm; And it discovered that the printing method to this film achieved said objective.

The present invention is characterized by the following points.
1. A multilayer film for laser printing in which a paper base layer, a color ink layer, and a pattern print layer are laminated in this order, the pattern print layer being the outermost layer of the film and partially on the color ink layer As a result, a region where the color ink layer and the pattern printing layer overlap each other and a region only of the color ink layer exist, and the color ink layer includes a green laser having an oscillation wavelength of 532 nm and an oscillation wavelength of 1090 nm. The multilayer film for laser printing described above, which develops color when irradiated with a laser beam of a fiber laser, a carbon dioxide gas laser with an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser with an oscillation wavelength of 1064 nm.
2. 2. The multilayer film for laser printing according to 1 above, wherein the coloring ink layer is a layer made of a white ink containing a titanium oxide pigment and a binder resin.
3. 2. The multilayer film for laser printing according to 1 above, wherein the color ink layer is a layer made of laser color ink containing a bismuth compound and a binder resin.
4). The packaging material for laser printing which has a heat-sealable resin layer as an innermost layer in the paper base material layer side of the multilayer film for laser printing in any one of said 1-3.
5. 5. The packaging material for laser printing according to 4 above, having a barrier layer between the paper base material layer and the heat-sealable resin layer.
6). A laser printing method on the multilayer film for laser printing or the packaging material for laser printing according to any one of 1 to 5 above, wherein an oscillation wavelength of 532 nm is applied to the region of only the color ink layer from the pattern printing layer side. A laser that prints a pattern by irradiating a laser beam of a green laser, a fiber laser with an oscillation wavelength of 1090 nm, a carbon dioxide laser with an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser with an oscillation wavelength of 1064 nm, Printing method.

The multilayer film for laser printing of the present invention has only a color ink layer and a partially printed pattern print layer on a paper substrate, and a green laser having an oscillation wavelength of 532 nm, an oscillation wavelength on the exposed color ink layer. An arbitrary pattern can be printed by irradiating a laser beam of a 1090 nm fiber laser, a carbon dioxide gas laser having an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser having an oscillation wavelength of 1064 nm. With this configuration, the multilayer film for laser printing of the present invention can print a pattern with excellent visibility with little damage.

  Further, the multilayer film for laser printing of the present invention can be manufactured at a low cost with a small number of layers, and paper dust and smoke are not generated in the printing process.

It is a schematic sectional drawing which shows an example about the layer structure of the multilayer film for laser printing of this invention. It is a schematic sectional drawing which shows an example about the layer structure of the packaging material for laser printing of this invention. It is a schematic sectional drawing which shows an example about the layer structure of the packaging material for laser printing of this invention.

The present invention will be described in detail below.
<I> Layer Configuration of Multilayer Film for Laser Printing of the Present Invention FIG. 1 is a schematic sectional view showing an example of the layer configuration of the multilayer film for laser printing of the present invention.
As shown in FIG. 1, the multilayer film for laser printing according to the present invention is basically composed of a paper base layer 1, a coloring ink layer 2, and a pattern printing layer 3. Here, each layer may have a single layer structure or a multilayer structure in which two or more layers are stacked. The pattern print layer 3 is the outermost layer of the film of the present invention and is a layer partially provided on the color ink layer 2. As a result, there are a region A having only the color ink layer and a region B in which the color ink layer and the pattern printing layer are overlapped.

In the area A having only the color ink layer, the color ink layer 2 is exposed on the outermost surface of the film. By irradiating this region A with a laser beam having a specific oscillation wavelength using any one of a green laser, a fiber laser, a carbon dioxide laser, a YVO ₄ laser, and a YAG laser, the coloring ink layer develops a color. The pattern is printed.

  Further, as shown in FIG. 2, the laser-printing packaging material of the present invention can be obtained by laminating a heat-sealable resin layer 4 as the innermost layer on the paper substrate layer 1 side of the multilayer film for laser printing. . Further, as shown in FIG. 3, a barrier layer 5 may be provided between the paper base material layer 1 and the heat-sealable resin layer 4.

  Further, if necessary, a desired surface treatment can be performed on each of the lamination surfaces before lamination. As the surface treatment, for example, pretreatment such as corona discharge treatment, ozone treatment, low temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, oxidation treatment using chemicals or the like can be performed. .

<II> Paper Base Layer In the present invention, as the paper base layer, any paper having various formability, flex resistance, rigidity, waist, strength, etc. can be used depending on the application. For example, it is a main strength material, and it is possible to use various types of paper, such as bleached or unbleached paper of strong size, or pure white roll paper, kraft paper, paperboard, processed paper, and milk base paper. The paper base material layer may be obtained by laminating a plurality of layers of these papers. An arbitrary thickness can be used. For example, the basis weight is 50 to 600 g / m ² , preferably the basis weight is 70 to 200 g / m ² , and the thickness is 60 to 860 μm, preferably 80 to 400 μm. It is a range.

<III> Coloring Ink Layer In the present invention, the coloring ink layer is any one of a green laser having an oscillation wavelength of 532 nm, a fiber laser having an oscillation wavelength of 1090 nm, a carbon dioxide gas laser having an oscillation wavelength of 10600 nm, and a YVO ₄ or YAG laser having an oscillation wavelength of 1064 nm. This is a layer formed by applying a color ink that develops color by irradiation with laser light on a paper base material layer. The color ink layer may be formed at a desired location where laser printing is to be performed, and does not need to be formed on the entire surface.

In one embodiment of the present invention, the color ink is a white ink containing at least a titanium oxide pigment and a binder resin. For white ink, additives such as plasticizers, stabilizers, antioxidants, light stabilizers, UV absorbers, curing agents, crosslinking agents, lubricants, antistatic agents, and fillers are optionally added as necessary. May be.
As the titanium oxide pigment, one or more of white pigments such as anatase-type titanium oxide and rutile-type titanium oxide can be used.

  Binder resin includes linseed oil, drill oil, soybean oil, hydrocarbon oil, rosin, rosin ester, rosin modified resin, shellac, alkyd resin, phenolic resin, maleic acid resin, natural resin, hydrocarbon resin, polychlorinated resin Vinyl resin, polyacetic acid resin, polystyrene resin, polyvinyl butyral resin, acrylic or methacrylic resin, polyamide resin, polyester resin, polyurethane resin, epoxy resin, urea resin, melamine resin, aminoalkyd resin, One type or two or more types of nitrified cotton, nitrocellulose, ethyl cellulose, chlorinated rubber, cyclized rubber, chlorinated polypropylene resin, vinyl chloride-vinyl acetate copolymer, and the like can be used in combination.

  The above-described titanium oxide pigment and binder resin, and further additives as necessary, are dispersed and kneaded with a solvent, a diluent, etc. to obtain a white ink. The mixing ratio of the titanium oxide pigment and the binder resin may be any ratio, but the mass ratio of the titanium oxide pigment: binder resin is particularly preferably 10 to 35:65 to 90, more preferably 10. ~ 25: 75-90. When there are more titanium oxide pigments than the above range, the film is easily damaged by laser irradiation. In addition, the cohesive force of the ink film is reduced, and there is a defect that the ink film falls off or the film strength decreases. On the contrary, when the amount of the titanium oxide pigment is less than the above range, the ink is thin, the concealability is insufficient, and the printed image may be unclear.

By limiting the content of titanium oxide pigments to a large amount and increasing the coating amount of titanium oxide pigments to 2.5 g / m ² or more, the density difference in laser printing with only white ink is large. It becomes easy to read.
Using the white ink, printing is performed on the paper substrate layer by a conventional printing method such as gravure printing, letterpress printing, screen printing, flexographic printing, and the like, and a color ink layer made of white ink is formed. The color ink layer made of white ink also functions as a printing ground for the pattern printing layer provided thereon. The white ink may be formed by one-time printing (one-time printing) or a plurality of times printing (multi-color printing).

  In another embodiment of the present invention, the coloring ink is a laser coloring ink containing a coloring material that develops color by laser light and a binder resin. Laser coloring inks optionally contain additives such as plasticizers, stabilizers, antioxidants, light stabilizers, UV absorbers, curing agents, crosslinking agents, lubricants, antistatic agents, fillers, etc. It may be added. By using laser coloring ink as the coloring ink, a clearer printed image can be obtained.

  As coloring materials that develop color by laser light, coloring agents such as dyes and pigments, clays, and the like can be used. Specifically, bismuth compounds, yellow iron oxide, inorganic lead compounds, manganese violet, cobalt violet, and the like. Metal compounds such as mercury, cobalt, copper, nickel, pearlescent pigments, silicon compounds, mica, kaolins, silica sand, diatomaceous earth, talc, titanium oxide-coated mica, tin dioxide-coated mica, antimony-coated mica One or two or more of tin + antimony-coated mica, tin + antimony + titanium oxide-coated mica can be used. In the present invention, a clear color can be obtained at a low output by irradiating a laser beam having an oscillation wavelength of 532 nm using a green laser or a laser beam having an oscillation wavelength of 1090 nm using a fiber laser. Preferably used.

  Examples of the bismuth compounds include bismuth nitrates such as bismuth oxide, bismuth nitrate and bismuth oxynitrate, bismuth halides such as bismuth chloride, bismuth oxychloride, bismuth sulfate, bismuth acetate, bismuth citrate, bismuth hydroxide, Examples thereof include bismuth titanate, and among them, bismuth nitrate and bismuth hydroxide are desirable from the viewpoint that they are easily available and inexpensive. A bismuth-type compound can contain 1 type, or 2 or more types of compounds. In addition, a coloring material that develops color by laser light other than bismuth compounds can be used in combination.

  As the binder resin, the conventional binder resins mentioned in the above white ink, for example, linseed oil, drill oil, soybean oil, hydrocarbon oil, rosin, rosin ester, rosin modified resin, shellac, alkyd resin, phenolic resin , Maleic acid resin, natural resin, hydrocarbon resin, polyvinyl chloride resin, polyacetic acid resin, polystyrene resin, polyvinyl butyral resin, acrylic or methacrylic resin, polyamide resin, polyester resin, polyurethane resin, epoxy 1 type or 2 types of resin, urea resin, melamine resin, amino alkyd resin, nitrified cotton, nitrocellulose, ethyl cellulose, chlorinated rubber, cyclized rubber, chlorinated polypropylene resin, vinyl chloride-vinyl acetate copolymer, etc. The above can be used together.

In the present invention, the laser coloring ink preferably further contains an inorganic compound as an additive for increasing the heat generation efficiency and enhancing the color development.
As such an inorganic compound, a metal oxide, a copper compound, a molybdenum compound, a copper / molybdenum composite oxide, a copper / tungsten compound, a metal salt, or the like is used.
Specifically, examples of the metal oxide include titanium oxide, magnesium oxide, zinc oxide, aluminum oxide, silicon oxide, nickel oxide, tin oxide, neodymium oxide, mica, zeolite, and kaolinite, and titanium oxide is particularly preferable. It is.

Examples of the copper compound include copper, copper oxide, copper halide, formic acid, citric acid, salicylic acid, lauric acid, oxalic acid, maleic acid and other organic acid copper, copper phosphate, hydroxyphosphate copper and the like. It can be used suitably.
As the molybdenum compound, molybdenum, molybdenum dioxide, molybdenum trioxide, molybdenum chloride, metal molybdate (metals: K, Zn, Ca, Ni, bismuth, Mg, etc.) can be preferably used.

As the metal salt, a salt of an acid such as sulfuric acid, nitric acid, oxalic acid, or carbonic acid with a metal such as barium, cobalt, magnesium, nickel, or iron can be used.
In the present invention, in particular, a material containing a bismuth-based compound as a color forming material and a material containing titanium oxide as an additive for enhancing color development is preferably used.

  The coloring material and the binder resin that develop color by the above laser beam, and further, if necessary, additives are added, and dispersed and kneaded with a solvent, a diluent or the like to obtain a laser coloring ink. The mixing ratio of the coloring material that develops color with the laser beam and the binder resin may be any ratio, but the content of the coloring material that develops color with the laser beam is particularly preferably based on the total mass of the laser coloring ink. It is preferable that it is 1-30 mass% in conversion of solid content. If it is less than 1% by mass, color development and printing are insufficient and unclear. Also, as the content increases, the color of the print becomes deeper, but even if it is 30% by mass or more, the difference in visibility due to the increase in density is not recognizable, but rather the cost increases, cracks, This is not preferable because the pigment color of the color forming material itself that develops the intensity reduction and develops color when irradiated with laser light appears.

  The inorganic compound as an additive for enhancing the color development is a ratio of up to 65% by mass, more preferably 5 to 65% by mass in terms of solid content, with respect to the total mass of the laser color ink. It can be added to laser coloring ink. If it exceeds 65% by mass, the increase in inorganic compounds is undesirable because the cost increases, the printed underlayer becomes brittle, and the strength is reduced. On the other hand, if the amount is less than 5% by mass, color development, printing may be insufficient, and blurring may occur.

Using the laser color ink, printing is performed on a paper base layer by a conventional printing method such as gravure printing, letterpress printing, screen printing, flexographic printing, and the like, and a color ink layer made of laser color ink is formed.
The color developing ink layer preferably has a thickness of 0.05 to 20 μm, more preferably about 0.1 to 7 μm. If the film thickness is less than 0.05 μm, color development, printing may be insufficient, and the image may be unclear.

  On the other hand, as the film thickness increases, the color of the print becomes darker. However, if the film thickness exceeds 20 μm, the cost increases, the strength of the color ink layer decreases, and the pigment color of the color material itself that develops color by laser light irradiation becomes a color ink layer. It is not preferable for the reason such as coloring. When the amount of pigment used is the same, the visibility of printing is slightly improved when the additive concentration is higher and the film thickness is thinner.

<IV> Picture Print Layer In the present invention, the picture print layer is formed by using a normal printing method to form a desired print picture such as a character, a figure, a symbol, a picture, or a pattern on a base material. .
In the present invention, the pattern printing layer may be composed of an arbitrary ink and may have a structure in which two or more layers are laminated.

Usually, the ink (or coating liquid) used to form the pattern printing layer is a binder resin, a colorant such as a pigment or dye, and various additives such as extender pigments, stabilizers, plasticizers, catalysts, and curing agents that are appropriately added thereto. Consists of.
In addition, when the pattern printing layer is printed and formed, the printing method may be a conventional printing method such as gravure printing, silk screen printing, offset printing, gravure offset printing, ink jet printing, or transfer printing. good.

<V> Heat-sealable resin layer In the present invention, in order to apply the multilayer film for laser printing as a packaging material for laser printing, a heat-sealable resin layer that functions as an innermost sealant is provided on the paper substrate layer side. Can be provided.
Moreover, you may include arbitrary intermediate | middle layers, for example, a barrier layer, between a heat-sealable resin layer and the said paper base material layer depending on necessity.

In the present invention, specific examples of the heat-sealable resin include polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene- Resins such as methacrylic acid copolymers can be used alone or in admixture of two or more.
These heat sealable resins can be laminated by extrusion coating or the like, or by laminating films made of these heat sealable resins by any method.

In heat-sealable resins, various types of lubricants, fillers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, colorants, etc. are used for various purposes such as adjusting the laminate strength. Additives can be added.
The layer thickness of the heat-sealable resin layer can be appropriately set according to the use of the multilayer film for laser printing, but is preferably 5 to 170 μm, and more preferably 10 to 50 μm.

<VI> Barrier Layer If desired, a barrier layer having a barrier property against oxygen and / or water vapor is provided between the paper base material layer and the heat-sealable resin layer.
In the present invention, the barrier layer may include a barrier resin layer, a vapor deposition film having an inorganic or inorganic oxide vapor deposition film, or a metal foil. Specific examples of the barrier layer include aluminum foil, aluminum-deposited polyester film, aluminum-deposited polypropylene film, silica-deposited polyester film, silica-deposited polyamide film, alumina-deposited polyester film, ethylene-vinyl alcohol copolymer film, and polyvinylidene chloride. , Polyvinyl alcohol, MXD6 and the like. Note that two or more barrier layers may be provided. When two or more barrier layers are provided, each may have the same composition or a different composition.

  A person skilled in the art can appropriately determine the thickness of the barrier layer. For example, when a barrier layer consists of barrier films, such as metal foil or a vapor deposition film, the thickness may be 5-30 micrometers, Preferably it is about 5-15 micrometers.

<VII> Printing The printing method of the present invention uses either a green laser with an oscillation wavelength of 532 nm, a fiber laser with an oscillation wavelength of 1090 nm, a carbon dioxide gas laser with an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser with an oscillation wavelength of 1064 nm. Printing is performed by irradiating a laser printing multilayer film with a laser beam.

Particularly preferably, printing is performed by irradiating a multilayer film for laser printing with a laser beam having a wavelength of 532 nm, which is the second harmonic of YAG or YVO ₄ , using a green laser marker device. Or it prints by irradiating the laser beam of wavelength 1090nm to the multilayer film for laser printing using a fiber laser marker apparatus. The laser light is irradiated from the surface on the pattern print layer side.

Laser light having a wavelength of 532 nm (green laser light) can be printed more finely because the spot diameter is small. Further, since the damage to the packaging material is small, the pulse width is short and the peak power is high, the amount of heat generation is small, and the influence on the laminate strength is small.
Further, laser light (fiber laser light) having a wavelength of 1090 nm has a high output and thus has high reactivity, and printing with higher visibility is possible.

  In the method of the present invention, a laser beam with a wavelength of 532 nm (green laser) or a laser beam with a wavelength of 1090 nm (fiber laser) is irradiated onto the color-printing ink layer from the pattern printing layer side to the multilayer film for laser printing. The colored ink layer in the portion irradiated with the laser light absorbs energy, carbonizes, and exhibits a black color. Alternatively, when the color forming ink layer contains a color former, it exhibits a color corresponding to the color former contained. On the other hand, the paper substrate is not damaged, and no paper dust or smoke is generated. Thereby, a desired clear printed image can be formed.

In the present invention, the laser print image includes, but is not limited to, letters, numbers, symbols, designs, and the like.
The printing method of the present invention can be applied to various packaging materials, labels, cards and the like.
EXAMPLES The present invention will be specifically described below with reference to examples, but these do not limit the present invention.

[Example 1]
A white ink having the following composition was applied to one surface of a gravure paper having a thickness of 200 μm by gravure printing to provide a coloring ink layer having a thickness of 5 μm.

White ink Titanium oxide 20% by mass (solid content conversion value)
Urethane resin 80% by mass (converted to solid content)
Total 100% by mass
The white ink having the above composition was used by mixing with an equal mass of a mixed solvent (methyl ethyl ketone: n-propyl acetate: isopropyl alcohol = 3: 5: 2 (mass ratio)).

  Next, a pattern printing layer was partially provided on the color ink layer by gravure printing. Further, an ethylene methacrylic acid copolymer resin (EMAA) was laminated on the opposite surface of the gravure paper by an extrusion laminating method to obtain a multilayer film for laser printing of the present invention.

A region of only the color ink layer of the film was irradiated with laser light having a wavelength of 532 nm (green laser SHG type) from the pattern printing layer side under the conditions of an average output of 4.8 W, a scanning speed of 2000 mm / s, and a frequency of 30 kHz.
As a result, the colored ink layer in the portion irradiated with the laser beam was carbonized and blackish, and a clear printed image was obtained.

[Example 2]
A multilayer film for laser printing of the present invention was obtained in the same manner as in Example 1 except that a laser color ink having the following composition was used in place of the white ink as the color ink layer.

Laser coloring ink Bismuth oxide (coloring agent) 5% by mass (solid content conversion value)
Titanium oxide (white ink content) 15% by mass (in terms of solid content)
Urethane resin 80% by mass (converted to solid content)
Total 100% by mass
The ink composition having the above composition was used by mixing with an equal mass mixed solvent (methyl ethyl ketone: n-propyl acetate: isopropyl alcohol = 3: 5: 2 (mass ratio)).

A region of only the color ink layer of the film was irradiated with a laser beam (fiber laser) having a wavelength of 1090 nm from the pattern printing layer side under conditions of an average output of 12 W, a scan speed of 2000 mm / s, and a frequency of 60 kHz.
As a result, the colored ink layer in the portion irradiated with the laser light was colored, and a clear printed image was obtained.

[Example 3]
An anchor coating agent was applied over the entire surface of the color ink layer and the pattern printing layer of the multilayer film for laser printing obtained in Example 2, and polyethylene was laminated thereon by an extrusion coating method so as to have a thickness of 13 μm. An overcoat layer was provided.

An area where the pattern print layer of the film does not exist was irradiated with laser light (green laser SHG type) having a wavelength of 532 nm from the overcoat layer side under conditions of an average output of 4.8 W, a scan speed of 2000 mm / s, and a frequency of 30 kHz. .
As a result, the colored ink layer in the portion irradiated with the laser beam was carbonized and blackish, and a clear printed image was obtained.

[Comparative Example 1]
A black ink having a thickness of 5 μm was applied on one surface of a gravure paper having a thickness of 200 μm by gravure printing to obtain a multilayer film for laser printing.
The film was irradiated with a carbon dioxide laser beam having an oscillation wavelength of 10600 nm to disperse black ink, thereby partially exposing the gravure paper to form a printed image. At this time, smoke and dust were generated.

1. 1. Paper base material layer 2. Colored ink layer Pattern printing layer4. 4. Heat sealable resin layer Barrier layer A. Region of color ink layer only Area where the color ink layer and the pattern printing layer overlap

Claims (6)

A multilayer film for laser printing, which is laminated in the order of a paper base layer, a coloring ink layer and a pattern printing layer,
The pattern printing layer is the outermost layer of the film and is partially provided on the coloring ink layer, whereby the coloring ink layer and the pattern printing layer overlap with each other, and the coloring ink layer There is only an area,
The coloring ink layer is colored by irradiation with a laser beam of a green laser having an oscillation wavelength of 532 nm, a fiber laser having an oscillation wavelength of 1090 nm, a carbon dioxide gas laser having an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser having an oscillation wavelength of 1064 nm. The multilayer film for laser printing.   The multilayer film for laser printing according to claim 1, wherein the coloring ink layer is a layer made of a white ink containing a titanium oxide pigment and a binder resin.   The multilayer film for laser printing according to claim 1, wherein the color ink layer is a layer made of laser color ink containing a bismuth compound and a binder resin.   The packaging material for laser printing which has a heat-sealable resin layer as an innermost layer in the paper base material layer side of the multilayer film for laser printing of any one of Claims 1-3.   The packaging material for laser printing according to claim 4, which has a barrier layer between the paper base material layer and the heat-sealable resin layer. A laser printing method for a multilayer film for laser printing or a packaging material for laser printing according to any one of claims 1 to 5,
From the pattern printing layer side to the color ink layer alone, either a green laser with an oscillation wavelength of 532 nm, a fiber laser with an oscillation wavelength of 1090 nm, a carbon dioxide laser with an oscillation wavelength of 10600 nm, or a YVO ₄ laser or a YAG laser with an oscillation wavelength of 1064 nm A laser printing method, wherein a pattern is printed by irradiating the laser beam.