JPH10305661A - Laser marking method and resin composition for laser marking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To color in an arbitrary color and to clearly mark by emitting a laser beam even by adding a small amount. SOLUTION: The laser marking having satisfactory visibility is obtained without coloring a base material by filler by emitting a laser beam to thermoplastic resin composition in which non-black non-metal inorganic conductive filler or preferably zinc oxide substance is dispersed and mixed. A filler content in the composition is preferably 0.05 to 30 wt.% and its mean particle size is preferably 20 μm or less. As the resin component, olefin resin is preferable. A molding of a beautiful color is obtained by using desired colorant having high transparency without coloring in suitable combination of conditions. Various laser such as a YAG laser, carbon dioxide gas laser selected from a wide wavelength region is usable with small energy density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for marking management information such as a production date, a lot number, a bar code and the like on a container of a thermoplastic resin molded product by using a laser beam, and a method suitable for laser marking. The present invention relates to a thermoplastic resin composition.

[0002]

2. Description of the Related Art Laser marking is a method of marking letters, numbers, trademarks, bar codes or images using a laser beam on the surface of a metal, ceramic, or polymer organic material. In addition, since the marking speed is high and automation and process control are easy, it has recently been widely used industrially.

[0003] When laser marking is performed on a thermoplastic resin, in general, the resin is simply melted or etched at a laser irradiated portion, and a clear mark display cannot be obtained since there is no contrast between an irradiated portion and a non-irradiated portion.

[0004] Therefore, marking is performed by blending various additives with a thermoplastic resin, molding the mixture, and irradiating a laser beam. For example, a molded product obtained by blending a colorant that changes color by heat into a thermoplastic resin is irradiated with a laser, and a contrast is obtained by decolorization and discoloration of the colorant at the irradiated portion, and a method of printing (Japanese Patent Publication No. 41320/1986, JP-A-5-254
252) Irradiating a laser to an injection molded product comprising 0.08 to 0.125% of carbon black or graphite mixed with a thermoplastic resin, and irradiating a rough surface with a dark color such as black in a non-irradiated portion. Printing from the contrast by whitening by foaming and foaming (Japanese Patent Laid-Open No. 57-116620,
JP-A-5-92657), a resin composition for laser marking using titanium black (JP-A-8-25806)
There is.

Although not directly related to the discoloration of a thermoplastic resin, a small amount of a film-forming binder contains a semiconducting metal oxide, and a thin film of the metal oxide is formed on a support. And a method of irradiating a laser to the metal oxide to discolor the metal oxide to form an image (JP-A-49-823).
40) are also known.

[0006]

In the method of (1), coloring,
In the method of requiring a coloring agent of about several percent for discoloration and a problem that a desired color cannot be arbitrarily colored because the coloring agent gives a color, the addition amount of carbon black is small, so that there is little influence on physical properties. However, the use of carbon black causes the molded product to be black and cannot be colored as desired. In addition, titanium black has a high coloring power and thus cannot be arbitrarily colored.

In addition, the semiconducting metal oxide only discolors itself when it is attached to or coated on the substrate surface with a binder, and has no connection with marking by discoloration of a resin molded product.

[0008] Further, these additives for imparting laser marking properties only produce visible markings only with laser light in a certain narrow wavelength range, so that the oscillation wavelength of the marking laser device used is low. If they are different, marking may not be performed, and there is a problem that a usable laser device is limited (for example, a carbon dioxide gas laser having a wavelength of 10.6 μm and a YAG laser having a wavelength of 1.064 μm have a problem).
(Because the laser light wavelengths differ greatly). From these points,
There has been a demand for a resin composition for laser marking that can be colored in an arbitrary color and that can be clearly marked by irradiation with a laser beam even when added in a small amount.

Further, there has been a demand for a resin composition for laser marking capable of performing clear marking with a commonly used marking laser device, for example, either a YAG laser device or a carbon dioxide laser device.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of such circumstances, and as a result, a molded article made of a thermoplastic resin composition containing a non-black non-metallic inorganic conductive filler has been obtained. The molded product can be colored to any color, and even with a small amount of non-black non-metallic inorganic conductive filler added, it is easy to make clear and highly visible markings near the surface without roughening the surface. Find out what you can do,
The present invention has been completed.

That is, the gist of the present invention is as follows. (1) A laser marking method characterized by irradiating a molded article made of a thermoplastic resin composition containing a non-black non-metallic inorganic conductive filler as a color sensitizer or a light-absorbing exothermic agent with laser light. . (2) The method according to (1), wherein the non-black non-metallic inorganic conductive filler is a zinc oxide-based substance. (3) The method according to the above (1) or (2), wherein the thermoplastic resin is a polyolefin resin. (4) The method according to the above (1), (2) or (3), wherein the laser light is a laser light having an oscillation wavelength in an infrared region. (5) The method according to any one of (1) to (4) above, wherein the oscillation wavelength of the laser light is 0.8 to 1.2 μm. (6) The method according to the above (2), wherein the laser beam is a carbon dioxide laser beam having an oscillation wavelength of 10.6 μm. (7) A resin composition for laser marking, comprising a thermoplastic resin and a non-black non-metallic inorganic conductive filler as a color sensitizer or a light-absorbing / heating agent. (8) The resin composition according to (7), wherein the non-black non-metallic inorganic conductive filler is a zinc oxide-based substance. (9) The average particle size of the nonmetallic inorganic conductive filler is 20
The resin composition according to the above (7) or (8), which is not more than μm and contains 0.05 to 30% by weight. (10) The resin composition according to the above (7), (8) or (9), wherein the thermoplastic resin is a polyolefin resin.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The typical and best modes of the embodiment of the present invention will be specifically shown in the examples described later, and the outline thereof is as follows.

The mechanism by which a thermoplastic resin containing a non-black non-metallic inorganic conductive filler causes visible marking by laser light is based on the non-black non-metallic type present near the surface of a resin molded product. When the inorganic conductive filler is irradiated with laser light, the inorganic conductive filler absorbs the laser light and generates heat, and the surrounding thermoplastic resin is carbonized by heat and becomes black, or the resin is partially heated. This is presumed to be due to the fact that it turned into gas and became bubbles in the molded product and appeared white.

The non-black non-metallic inorganic conductive filler used in the present invention includes a zinc oxide compound doped with aluminum, tin or titanium; a titanium oxide compound doped with antimony or tin or a mixture of antimony oxide and tin oxide. Titanium oxide compounds (anatase type, rutile type) forming a conductive layer of composite oxide; barium sulfate compounds forming a conductive layer of composite oxide of antimony oxide and tin oxide; composite oxide of antimony oxide and tin oxide Aluminum borate-based compound forming a conductive layer of: an antimony oxide and a tin oxide; a potassium titanate-based compound forming a conductive layer of an antimony oxide and a tin oxide; a composite oxidation of indium oxide and a tin oxide And non-black fillers such as compound-based compounds.

In general, a compound having a powder resistance of 500 Ω · cm or less and exemplified by trade names, such as Pastoran II, Pastoran IV, Pastoran V, ATO, ITO manufactured by Mitsui Kinzoku Co., Ltd.
Etc .; Mitsubishi Materials Corporation W-P, T-1, 10-S etc .;
Ishihara Sangyo ET-500W, FT-1000, FT-
2000 etc .; DENTOL WK-200, W manufactured by Otsuka Chemical Co., Ltd.
Specific examples include K-200B and the like; 23-K manufactured by Hakusui Chemical Co., Ltd., and the like.

Among them, a zinc oxide compound doped with aluminum, tin or titanium, a complex oxide of antimony oxide and tin oxide, and a complex oxide compound of indium oxide and tin oxide can provide a molded article with less coloring. The titanium oxide-based compound doped with antimony or tin or the titanium oxide-based compound (anatase type, rutile type) forming a conductive layer of a composite oxide of antimony oxide and tin oxide is slightly gray-white but other than white It is preferable because it can be colored to any color and has good laser marking property.

Further, the zinc oxide compound doped with aluminum, tin or titanium is excellent in heat absorption and heat generation in a wide wavelength range, that is, it has high sensitivity and high visibility even when irradiating a laser beam having a significantly different oscillation wavelength. It is particularly preferable in that laser printing is possible.

The non-black non-metallic inorganic conductive filler is 1
Species or a mixture of two or more species may be used, and the use amount thereof is in the range of 0.05 to 30% by weight in the thermoplastic resin composition or in the molded product composed of the composition.
When the content is less than 0.05% by weight, clear printing cannot be obtained by laser beam irradiation, and when it exceeds 30% by weight, mechanical properties and moldability are impaired. Preferably, the range is 0.1 to 5% by weight.

The non-black non-metallic inorganic conductive filler exists in a dispersed state in the thermoplastic resin. Accordingly, the smaller the particle size, the better the uniform coloring property of the laser-printed portion, the transparency of the molded product, the surface smoothness, and the mechanical properties, so that the average particle size is preferably 20 μm or less, and especially 5 μm.
m or less is particularly preferred.

These non-black non-metallic inorganic conductive fillers are surface-treated with a metal soap, a low molecular weight resin wax, a silane coupling agent, a titanium coupling agent or the like in order to enhance dispersibility in a thermoplastic resin. Can be used.

The thermoplastic resin used in the present invention includes polyolefin resin, polystyrene resin, polycarbonate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, acrylic resin, polysulfone resin, polyphenylene ether resin,
Polyethersulfone resin, polyarylate resin, polyamide resin, polyamideimide resin, polyetherimide resin, acrylonitrile-butadiene-styrene resin (ABS resin), acrylonitrile-styrene resin (AS resin) Resins) and thermoplastic polyurethane-based resins.

Examples of the polyolefin resin include a polyethylene resin, a polypropylene resin, a polymethylpentene resin, and a cyclic olefin resin. Furthermore,
Linear low-density polyethylene as polyethylene resin,
Low density polyethylene, high density polyethylene, ethylene-
Polar vinyl monomer copolymers and the like; propylene homopolymers and random copolymers as polypropylene resins,
Block copolymers, propylene-polar vinyl monomer copolymers, syndiotactic polypropylene and the like can be mentioned.

Among them, the polyolefin-based resin has a resin composition for laser marking to which a non-black non-metallic inorganic conductive filler is added. Is preferable because a clear laser print can be obtained.

Also, when a coloring agent is used in combination, bright coloring is possible, and a vivid and clear marking can be obtained on a beautiful color background, which is preferable. As the laser device used in the present invention, a device that generates laser light having a wavelength in the infrared region is preferable, and examples thereof include a carbon dioxide laser device, a carbon monoxide laser device, a semiconductor laser device, and a YAG laser device. A laser device of 8 to 1.2 μm is preferable, and a pulse YAG laser device having an oscillation wavelength of 1.064 μm and a scanning YAG laser device with a Q switch are particularly preferable.

However, in the case of a thermoplastic resin containing a zinc oxide compound doped with aluminum, tin or titanium, a TEA having an oscillation wavelength of 10.6 μm and an output of 3 J or more is used.
Type carbon dioxide laser device (pulse type), scanning type carbon dioxide laser with output 5W or more, output 5 with oscillation wavelength 1.064μm
A pulse-type YAG laser device with J or more and a scanning YAG laser device with Q-switch with output of 0.5 W or more are particularly preferable.

In order to carry out the laser marking method of the present invention, a thermoplastic resin composition containing a non-black non-metallic inorganic conductive filler is used, and a desired shape is formed by injection molding, extrusion molding, inflation molding or the like. A molded product such as a film or a film is obtained, and in the case of a pulsed laser, a laser beam is cut out and irradiated to a desired mark shape with a mask, or in the case of a scanning type laser marking, a laser beam is applied to the surface of the molded product. If marking is performed by scanning and irradiating a laser beam having a large spot diameter, marking with high visibility can be achieved only by laser irradiation.

When irradiating the laser beam, the surface of the thermoplastic resin composition containing a non-black non-metallic inorganic conductive filler may not be present, and the laser beam may be applied to the surface of the molded product for protection or the like. Laser light may be irradiated from the surface of a molded product having a coating film or a laminated film which is not completely absorbed or a molded product having a multilayer film shape.

In order to obtain the resin composition for laser marking of the present invention, a non-black non-metallic inorganic conductive filler may be dispersed in a thermoplastic resin. Any color can be used in combination.

In order to disperse a non-black non-metallic inorganic conductive filler in a thermoplastic resin, it is used in general resin processing fields such as a dispersion stirrer, a two-roller, a three-roller, an extrusion kneader, and an internal mixer. The known dispersion kneading apparatus can be used. What is necessary is just to select a dispersing and kneading apparatus suitable for the thermoplastic resin to be used, in which the non-black non-metallic inorganic conductive filler has few aggregated particles and a more uniform dispersion state is obtained.

Further, a master batch or the like containing a high concentration of non-black non-metallic inorganic conductive filler is prepared in advance, and a thermoplastic resin is added and diluted to a predetermined concentration at the time of molding to form a laser. A molding for marking may be obtained.

Various additives can be added to the laser batch resin composition or the masterbatch containing the non-black non-metallic inorganic conductive filler at a high concentration, if necessary.

As additives, dispersants (metal soap, low molecular weight resin wax, surfactant), lubricants / release agents, antioxidants, ultraviolet absorbers, antioxidants, reinforcing agents (whiskers, glass fibers, Carbon fiber), colorant (inorganic pigment,
Organic pigments, dyes, etc.), fillers (calcium carbonate, clay, etc.), resin nucleating agents, and the like, which are usually used for thermoplastic resins, may be mentioned.

It is preferable to use one or more of these additives as appropriate in a range that does not reduce the moldability and the mechanical properties. However, when no mechanical properties are required, Is required for workability and required characteristics of molded products.
More than one additive may be used in the required amount.

Examples of molded articles to be marked by the laser marking method of the present invention include: electronic parts such as connectors and relay cases; mechanical parts such as gears and cams; containers such as plastic cases and packaging films; electric wires and key tops. ,
Plastic sheets, plastic tubes, cards, plastic lenses, etc., products, such as trademarks, product numbers, lot numbers, production dates, expiration dates, barcodes, etc., or marking characters that are very small or have a flat surface Articles that are difficult to be marked by ordinary methods, or articles that require markings that cannot be erased for the purpose of preventing forgery and the like.

[0035]

Next, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Incidentally, all percentages and parts in the examples are based on weight.

Example 1 High-density polyethylene resin {J-REX A6080A manufactured by Nippon Polyolefin Co., Ltd.} 100 parts Conductive titanium oxide {ET-500W manufactured by Ishihara Sangyo Co., Ltd.) 0.5 part The above components were homogenized using a twin-screw extruder. A resin pellet was obtained, and a stepped plate-like thin gray-white molded product having a length of 9 cm, a width of 5 cm, a thickness of about 2.5 mm and a thickness of 1.5 mm was obtained using an injection molding machine.

The molded product has a Q switch frequency of 2 kHz,
The laser beam is set to 10 with a YAG laser device set to output 5W.
When the characters were marked at a speed of 0 mm / sec, very clear dark brown characters were obtained.

Comparative Example 1 A molded product was obtained using only high-density polyethylene in the same manner as in Example 1 except that the amount of conductive titanium oxide was changed to 0.05 part, and laser marking was performed in the same manner. I couldn't.

Comparative Example 2 Laser marking was performed in the same manner as in Example 1 except that the conductive titanium oxide was replaced with titanium oxide, but no clear characters were obtained.

Example 2 Polybutylene terephthalate resin {Planac 1 20 manufactured by Dainippon Ink and Chemicals, Inc. 100} 100 parts Conductive zinc oxide {manufactured by Hakusui Chemicals 23-K} 0.5 part The above components were homogenized using a twin-screw extruder. The obtained resin pellets were obtained using an injection molding machine to obtain stepped plate-like thin off-white molded products having a length of 9 cm, a width of 5 cm, a thickness of about 2.5 mm and 1.5 mm. This molded product has a Q switch frequency of 2 kHz.
When a letter was marked with a laser beam at a speed of 100 mm / sec with a YAG laser device set at 1.5 W and an output of 1.5 W, very clear dark brown letters were obtained.

Examples 3 to 5 In place of the conductive titanium oxide of Example 1, a non-black non-metallic inorganic conductive filler shown in Table 1 was used, and a molded product was obtained by the same composition and method as in Example 1. Marking was similarly performed using a YAG laser device. Table 1 shows the evaluation results.

Example 6 The formed plate of Example 5 was subjected to 3.5 with a TEA-CO ₂ laser device.
When one pulse of laser light having an energy of J / cm ² was irradiated, very clear black marking characters were obtained.

Comparative Example 3 A molded product was obtained in the same manner as in Example 5 except that zinc oxide was used instead of conductive zinc oxide, and marking was performed with a YAG laser device in the same manner as in Example 1, but no printing was performed. Was.

Comparative Example 4 A molded product was obtained in the same manner as in Example 5 except that zinc oxide was used instead of conductive zinc oxide, and a laser beam having an energy of 3.5 J / cm ² was obtained using a TEA-CO ₂ laser apparatus. Was irradiated for one pulse, but no printing was performed.

[0045]

[Table 1]

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23/00 C08L 23/00 101/00 101/00

Claims (10)

[Claims] 1. A laser characterized in that a molded article comprising a thermoplastic resin composition containing a non-black non-metallic inorganic conductive filler as a color sensitizer or a light-absorbing exothermic agent is irradiated with a laser beam. Marking method. 2. The method according to claim 1, wherein the non-black non-metallic inorganic conductive filler is a zinc oxide-based material. 3. The method according to claim 1, wherein the thermoplastic resin is a polyolefin resin. 4. The method according to claim 1, wherein the laser light is a laser light having an oscillation wavelength in an infrared region. 5. An oscillation wavelength of a laser beam is 0.8 to 1.2 μm.
The method according to any one of claims 1 to 4, wherein m is m. 6. The method according to claim 2, wherein the laser beam is a carbon dioxide laser beam having an oscillation wavelength of 10.6 μm. 7. A resin composition for laser marking, comprising a thermoplastic resin and a non-black non-metallic inorganic conductive filler as a color sensitizer or a light-absorbing / heating agent. 8. The resin composition according to claim 7, wherein the non-black non-metallic inorganic conductive filler is a zinc oxide-based substance. 9. The resin composition according to claim 7, wherein the nonmetallic inorganic conductive filler has an average particle size of 20 μm or less and contains 0.05 to 30% by weight. 10. The resin composition according to claim 7, wherein the thermoplastic resin is a polyolefin resin.