JP2011093170A - Ink for laser sensitization layer, recording medium for laser marking, and laser marking method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ink for a laser sensitization layer, which achieves sharp and clear marking using lower laser irradiation energy and prevents a sheet or a film from curling when printed on the sheet or the film by a laser marking method having features such as non-contact and high-speed marking, and to provide a recording medium for laser marking using the same, and a laser marking method. <P>SOLUTION: The ink for the laser sensitization layer contains titanium dioxide, nitrocellulose, polyurethane, and a plasticizer. A solid content excluding a solvent from the ink for the laser sensitization layer contains 50-70 wt.% of the titanium dioxide, 20-30 wt.% of the nitrocellulose, 5-10 wt.% of the polyurethane, and 5-15 wt.% of the plasticizer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser sensitizing layer ink in a laser marking method and a laser marking recording body using the same.

  In general, the laser marking method that destroys the surface layer irradiates the surface of the substrate with laser light of an arbitrary pattern, destroys the surface layer of the substrate by evaporation and scattering, and the brightness and hue between the exposed base and the non-destructive part. The marking method obtains visibility by using the difference obtained by the difference between the above or the irregular reflection of the light due to the unevenness of the broken portion. Compared to irregular reflection of light due to fine irregularities on the surface, for example, the colored ink layer printed on wrapping paper or paper labels is destroyed by laser light, and the white and non-destructive parts of the exposed underlying paper are colored A method using brightness and hue difference with ink has high visibility, and is simple and effective.

  However, since this method requires high laser energy to evaporate or scatter the colored layer, a laser marking recording material that can be marked with a lower energy laser has been studied. For example, Patent Document 1 describes that a molded article made of an amorphous thermoplastic resin containing cordiolite and / or mica can be marked with a low energy laser.

  Further, in Patent Document 2, a sensitizing layer containing a laser sensitizer that converts laser light into heat is formed between a support and a colored layer, and synthetic mica, cordierite or laser sensitizer is used as the laser sensitizer. By using kaolin, a recording body is disclosed that can efficiently destroy and mark a colored layer even with weak laser light. However, a special sensitizer such as synthetic mica, cordierite or kaolin must be added to this sensitized layer, and an operation for mixing and dispersing them is required, and the colored layer is destroyed by laser. In particular, with a low energy laser, the appearance and the visibility of the printed part were insufficient.

  Therefore, in Patent Document 3, the present inventor has disclosed an ink for a laser sensitizing layer that can be clearly marked with a lower laser irradiation energy without using a special laser sensitizer, and a recording for laser marking using the same. Body and laser marking method could be provided. However, in subsequent studies, when the laser sensitizing layer ink is coated on paper or film, the coated material curls, making it difficult to handle in the step of applying the coated material to the container. There was a problem.

JP-A-4-267191 JP-A-9-286169 Japanese Patent Application No. 2008-334434

  Accordingly, an object of the present invention is to provide a laser marking method characterized by non-contact, high-speed marking, which can be clearly marked with a lower laser irradiation energy and does not curl when applied to paper or film. An object of the present invention is to provide a sensitizing layer ink, a laser marking recording material using the same, and a laser marking method.

  As a result of earnestly examining the improvement of the laser sensitizing layer ink of Patent Document 3, the present inventor can improve the curling property while maintaining the conventional performance by adding a polyurethane compound and a plasticizer to the ink. The present invention has been completed.

That is, the present invention
(1) A laser-sensitized layer ink comprising titanium dioxide, nitrocellulose, polyurethane and a plasticizer,

(2) 50 to 70% by weight of the titanium dioxide, 20 to 30% by weight of the nitrocellulose, 5 to 10% by weight of the polyurethane, and the plasticizer in a solid content obtained by removing the solvent from the ink for the laser sensitizing layer. The ink for laser sensitizing layers according to (1), comprising 5 to 15% by weight,

(3) The laser sensitizing layer ink according to (1) or (2), wherein the titanium dioxide has an average particle size of 0.1 to 0.3 μm,

(4) The laser sensitizing layer ink according to any one of (1) to (3) is applied on the support, and dried and solidified to form a laser sensitizing layer, and a colored layer is further formed thereon. A recording body for laser marking, characterized in that

(5) The recording material for laser marking according to (4), wherein the colored layer has a thickness of 0.1 to 10 μm,

(6) The recording body for laser marking according to (4) or (5), wherein the support is plain paper, resin-coated paper, or aluminum-deposited paper,

(7) A laser marking method, wherein the colored layer is destroyed and marked by irradiating the laser marking recording medium according to any one of (4) to (6) with a laser beam. ,

(8) The laser marking method according to (7), wherein the laser beam is a carbon dioxide laser.
It is.

According to the present invention, since the colored layer can be broken with a low-energy laser beam, laser marking for a laser sensitizing layer capable of high-speed and wide-range laser marking and capable of clear marking with a low-energy laser is also possible. And a recording medium and a recording method using the same.
In addition, since the laser sensitizing layer ink of the present invention does not curl even when applied to paper or film, it becomes easy to affix the coated paper or film to a container, etc. It can contribute to improvement.

    Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that this embodiment is merely an embodiment for carrying out the present invention, and the present invention is not limited by this embodiment, and various modified embodiments can be made without departing from the gist of the present invention. Is possible.

  The recording material for laser marking of the present invention is formed by applying a laser sensitizing layer ink containing titanium dioxide, nitrocellulose, polyurethane and a plasticizer on a support, and then drying to form a laser sensitizing layer. Further, a colored layer is formed thereon.

  The sensitizer used in the laser sensitizing layer ink of the present invention is titanium dioxide. Titanium dioxide is suitable because it efficiently absorbs laser light, particularly a carbon dioxide laser generally used as a low-energy laser, and has high coloring power and hiding power. The average particle diameter of titanium dioxide is preferably 0.1 to 0.3 μm. When the particle diameter is less than 0.1 μm, the concealability is lowered, and when it exceeds 0.3 μm, the dispersibility is lowered, which is not preferable. The titanium dioxide may be in the form of crystals such as rutile type and anatase type, but is preferably surface-treated in order to suppress the photocatalytic activity of the surface. Examples of the surface treatment agent include polyol, silica, siloxane, and alumina. However, the surface treatment agent is not limited to these as long as the photocatalytic activity is suppressed, and a plurality of surface treatments are possible.

  The titanium dioxide content in the laser sensitizing layer ink is 50 to 70% by weight in terms of solid content excluding the solvent. If it is less than 50% by weight, the hiding power is insufficient and the laser sensitizing effect is also insufficient, so that the printing becomes unclear when laser printing is performed. On the other hand, if it exceeds 70% by weight, the amount of resin becomes excessive compared to the amount of resin, and the resin cannot retain titanium dioxide. It becomes unsuitable.

  The particle diameter is a value measured using a laser type particle size distribution measuring machine (for example, Microtrack manufactured by Nikkiso Co., Ltd.).

  The nitrocellulose used in the laser sensitizing layer ink is preferably a low-viscosity type 1/16 nitrocellulose, and the content thereof is 20 to 30 in terms of solid content excluding the solvent of the laser sensitizing layer ink. % By weight. Since the nitrocellulose has a low viscosity, its content can be easily adjusted.

  In the laser sensitizing layer ink of the present invention, polyurethane and a plasticizer are added to improve curling properties when printed on paper or film.

  The polyurethane having a number average molecular weight of 4,000 to 10,000 is suitable. The amount used is 5 to 10% by weight in terms of solid content with respect to the laser sensitizing layer ink.

  As the plasticizer, mono-higher fatty acid ester of glycerin diacetate is preferably used, and the amount used thereof is 5 to 15% by weight in terms of solid content with respect to the laser sensitizing layer ink.

  Other resins may be added to the laser sensitizing layer ink depending on the purpose. For example, polyamide resin, polybutyral resin, polyvinyl butyral resin, polyvinyl alcohol resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, petroleum resin, chlorinated rubber resin, cyclized rubber resin, alkyd resin , Phenolic resins, epoxy resins and the like.

  In addition, a filler such as calcium carbonate, silica, alumina, magnesia, barium sulfate, and zinc oxide, and a colorant such as a pigment and a dye can be added to the laser sensitizing layer ink as necessary.

  The ink for a laser sensitizing layer of the present invention is produced by uniformly mixing and dispersing the above-described components together with a diluting solvent.

  In the colored layer of the present invention, colorants such as pigments and dyes are dispersed or dissolved in the resin component. Examples of the resin component include polyamide resins, polybutyral resins, polyvinyl butyral resins, polyvinyl alcohol resins, nitrocellulose resins, acrylic resins, vinyl chloride-vinyl acetate copolymer resins, urethane resins, petroleum resins, Examples thereof include chlorinated rubber resins, cyclized rubber resins, alkyd resins, phenol resins, and epoxy resins.

  The colorant and filler used in the colored layer are not limited by chemical composition, structure, color, etc., but are generally used dyes, fluorescent dyes, extender pigments, organic fine particles, hollow particles, metal powders, metal coats Examples thereof include particles, among which those having a high laser beam transparency are preferable.

  The support of the present invention is not particularly limited, and is selected from durability, design properties, etc. required by the intended use, plain paper, art paper, coated paper, aluminum vapor-deposited paper, vinyl chloride resin Polyester resin, polyolefin resin, metal sheet or film, synthetic paper, laminated paper, or the like can be used. It may be a three-dimensional object.

  The recording body for laser marking of the present invention is produced by forming a laser sensitizing layer and a colored layer in order on a support.

The laser sensitizing layer is formed by applying the laser sensitizing layer ink on the support, and the coating thickness is 0.1 to 10 g / m ² or 0.1 after drying. 10 to 10 μm, preferably 0.5 to 5 g / m ² or 0.5 to 5 μm.

The colored layer is formed on the laser sensitizing layer. The coating thickness of the colored layer is such that it is easy to be destroyed even at a low energy density, and in order to reduce the amount of scattering from the colored layer, the thin coating thickness is good in the range where the necessary hue can be obtained, and it is dry. It is 0.1-10 g / m < ² > or 0.1-10 micrometers later, More preferably, it is 0.5-5 g / m < ² > or 0.5-5 micrometers. In addition, the content of the colorant in the dry coating film of the colored layer is preferably as small as possible within the range where the necessary hue and color density are obtained, and is preferably 0.1 to 50% by weight.

  Also, in order to give smoothness to the support or to improve the adhesion between the support and the laser sensitizing layer, a nitrocellulose resin, polyamide resin, acrylic resin is provided between the laser sensitizing layer and the support. In addition, an undercoat layer containing a resin or filler mainly containing various polymers such as polyurethane resin, polyester resin, epoxy resin, silicon resin, or fluorine resin may be formed.

  In order to enhance the durability of the recording material for laser marking of the present invention or to suppress damage due to external force, polyethylene resin, polypropylene resin, ethylene-vinyl acetate resin, ethylene-ethyl acrylate resin, acetate nitrocellulose Resins, nitrocellulose resins, polyamide resins, acrylic resins, polyurethane resins, polyester resins, epoxy resins, silicon resins, fluorine resins, and the like, as well as fillers and lubricants for these resins Further, an overcoat layer to which an auxiliary agent such as an ultraviolet absorber, an antioxidant, a water repellent or an oil repellent is added can be used on the colored layer.

  The resin type used for the overcoat layer is preferably one or more of acrylic resin, nitrocellulose resin or polyamide resin. Further, the thermal decomposition temperature of the resin is preferably low, and 450 ° C. or less, preferably 350 ° C. or less, so as not to hinder the destruction due to evaporation and scattering of the colored layer. Since the thickness of the overcoat layer also affects the destruction by evaporation and scattering of the colored layer, it is preferably 15 μm or less.

  As a method of forming a laser sensitizing layer, a colored layer, and an overcoat layer on a support, conventional printing and coating methods can be used. For example, gravure printing, offset printing, flexographic printing, screen printing, air printing Examples of the coating method include knife coating and blade coating.

  The coating solution for the laser sensitized layer and the colored layer includes a dispersant, a viscosity modifier, a filler, a leveling agent, a lubricant, an ultraviolet absorber, an antioxidant, an antistatic agent, a colorant, a thermal sensitizer, Auxiliaries classified as preservatives and the like can be added.

In order to print on the recording medium of the present invention, the laser marking recording medium of the present invention may be marked by irradiating with a laser beam, and the output of the laser device is 0.2 joule / cm ² · pulse or more, preferably Is preferably a pulsed laser capable of applying an energy of 0.3 Joule / cm ² · pulse or more to the irradiation surface, or a scanning laser having an output of 0.5 W or more. For example, a carbon dioxide laser, a carbon monoxide laser, a semiconductor Lasers, yttrium aluminum garnet (YAG) lasers, etc., among others, Transversely
Since an Excited Atmospheric Pressure (TEA) type carbon dioxide laser can irradiate a wide area at a high speed with one pulse, a large amount of information can be marked at a high speed, which is particularly preferable.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but is not limited thereto.

<Laser sensitizing layer ink>
The raw materials used are listed in Table 1.

  Each laser sensitizing layer ink was prepared by dispersing the formulation shown in Table 2 together with ceramic beads by shaking with a paint conditioner for 2 hours. Moreover, in Table 3, each component was represented by weight% of solid content except a solvent.

<Colored layer ink>
NEWMAC VESTA910 Black (polyamide-based black ink manufactured by Tokyo Ink Co., Ltd.)
Diluting solvent: toluene / isopropyl alcohol / ethyl acetate = 6/3/1

<Overcoat layer ink>
KROP varnish 130B (Nitrocellulose OP Varnish manufactured by Tokyo Ink Co., Ltd.)
Diluent: Ethyl acetate

<Preparation of recording material>
After adjusting the printing viscosity by adding a diluting solvent so that each ink has a viscosity of 18 ± 1 seconds in # 3 Zahn cup method viscosity measurement, it is used for a laser sensitizing layer on a letterpress printing base paper as a support. Gravure printing was performed in the order of ink (plate depth 30 μm), colored layer ink (plate depth 35 μm), and overcoat layer ink (plate depth 30 μm) to prepare a recording material. In addition, the recording bodies produced from Formulation Examples 1 and 2 correspond to Examples 1 and 2, respectively, and the recording bodies produced from Formulation Examples 3 to 5 correspond to Comparative Examples 1 to 3, respectively.

<Printing on the recording medium>
A carbon dioxide gas laser (ML-G 9 30 0 manufactured by Keyence Co., Ltd.) was used for this recording medium, and printing recording was performed with a laser at a laser power of 50% and a scanning speed of 4800 mm / s, and evaluation was performed according to the following criteria.

<Evaluation method>
Printing effect: Lightness difference between laser irradiated portion and non-laser irradiated portion is measured with a colorimeter (CR-241 manufactured by Minolta). Brightness difference is 50 or more, ○ is less than 40-50, Δ is less than 40 As evaluated.
Finish: Evaluation of the finish of the label as a whole. The appearance such as color developability and gloss in the printing configuration was evaluated in three stages: good ○, medium Δ, and bad ×.
Curling property: A 55 mm × 65 mm piece of paper is cut out from the recording material produced in the above <Production of recording material> and stored under the following three conditions with the coated surface facing up, and then the maximum floating portion of the grounded portion and the edge of the paper piece The distance was measured, and 10 mm or less was accepted, and more than 10 mm was rejected. The pass was evaluated as over 90% as ◯, 90-70% as Δ, and less than 70%.
1. 30 ° C, humidity 55% 24 hours 10 samples
2. 30 ° C, 70% humidity 24 hours Sample number 10
3. 40 ° C, 80% humidity 24 hours Sample number 10

These evaluation results are shown in Table 4.
According to Table 3, it can be seen that the curling properties are clearly improved in Examples 1 and 2 using the laser sensitizing layer ink of the present invention as compared with the comparative example.
Note that Comparative Examples 2 and 3 correspond to the examples of Patent Document 3, but the printing effect and finish are good, but it can be seen that there is a problem in curling properties.

Claims (8)

  A laser sensitizing layer ink comprising titanium dioxide, nitrocellulose, polyurethane and a plasticizer.   In the solid content obtained by removing the solvent from the laser sensitizing layer ink, the titanium dioxide is 50 to 70% by weight, the nitrocellulose is 20 to 30% by weight, the polyurethane is 5 to 10% by weight, and the plasticizer is 5 to 15%. The ink for a laser sensitizing layer according to claim 1, comprising: wt%.   3. The laser sensitizing layer ink according to claim 1, wherein the titanium dioxide has an average particle diameter of 0.1 to 0.3 [mu] m.   Applying the laser-sensitizing layer ink according to any one of claims 1 to 3 on the support, drying and solidifying the laser-sensitizing layer, and further forming a colored layer thereon. Characteristic recording material for laser marking.   5. The recording material for laser marking according to claim 4, wherein the colored layer has a thickness of 0.1 to 10 [mu] m.   6. The recording body for laser marking according to claim 4, wherein the support is plain paper, resin-coated paper, or aluminum vapor-deposited paper.   7. A laser marking method, wherein the colored layer is destroyed and marked by irradiating the laser marking recording body according to any one of claims 4 to 6 with a laser beam.   The laser marking method according to claim 7, wherein the laser beam is a carbon dioxide gas laser.