JPH10237319A - Thermoplastic resin composition for laser marking, resin molded article and method for laser marking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition having no influence on the color tone of a resin, obtaining clear dark down to black marks by the irradiation of laser rays, having high mechanical reading accuracy and useful for marking of a bar code, a Karura code, etc., by compounding titanium dioxide as an active component. SOLUTION: The objective composition is obtained by compounding titanium dioxide in an amount of 0.05-70wt.%, preferably 0.1-50wt.%, further preferably 0.1-20wt.% as an active component in a thermoplastic resin such as a polyolefin resin of polyethylene, polypropylene, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition for laser marking, a resin molded product, and a method for recording a barcode using a laser beam.

[0002]

2. Description of the Related Art At present, a bar code system is most widely used as a technique for automatically recognizing various kinds of information using an optical device. Barcodes are used not only for inventory management, process management, assembly, shipping, etc. in the manufacturing industry, but also for large-volume retailers such as supermarkets and department stores, as well as specialty stores and restaurants that operate chains. It is widely applied to POS systems. This barcode requires the accuracy of the displayed bar width,
There are many technical restrictions on display processing.

In laser marking, laser light is directly applied to the surface of a component made of a high-molecular organic material, metal, or the like, and changes in the state of the surface or changes in the irradiated portion due to discoloration or decolorization of the colorant are utilized. Marking. However, in this marking method, when a polyolefin resin is used as a base material for marking, depending on the case, the resin transmits laser light and cannot be marked, or the laser light is absorbed and etching occurs. Even in this case, there is a problem that clear marking cannot be performed only by melting the resin, and that even if a coloring agent is used, it is difficult to form a clear color.

[0004] In order to solve such problems, when applying a laser marking method to a polyolefin resin molded product, various studies have been made on a color former which produces a clear color. For example, in JP-A-60-155493, yellow iron oxide is used.
No. 6285, an inorganic lead compound is disclosed in JP-A-2-204888.
Then manganese violet, cobalt violet,
JP-A-63-239059 describes metal compounds such as mercury, cobalt, copper, bismuth, and nickel, respectively. However, since the resin composition containing these compounds contains heavy metals, there are problems such as safety and impact on the environment.In addition, in the case of resin compositions containing yellow iron oxide, the compounds themselves are colored. Therefore, there is a problem that the color tone of the composition is limited. JP-A-60-110737 describes a resin composition to which a pearlescent pigment is added, assuming that the compound is not colored. In this case, the pearlescent pigment is not colored but has a pearly luster. There is a problem that it can not be used for products that do not.

[0005]

Accordingly, there is a need for a resin composition for marking, which has a white active ingredient itself, is colored from a clear blackish brown to black by a laser beam, and has high machine-readable accuracy.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have arrived at the present invention. That is, the present invention provides (1) a thermoplastic resin composition for laser marking containing titanium dioxide as an active ingredient, and (2) a content of titanium dioxide of 0.05.
(1) the thermoplastic resin composition for laser marking, wherein the thermoplastic resin is a polyolefin resin; and (4) the thermoplastic resin composition for laser marking, wherein the thermoplastic resin is a polyolefin resin. (3) a thermoplastic resin composition for laser marking wherein the polyolefin resin is polyethylene or polypropylene; and (5) a resin molding obtained by molding the thermoplastic resin composition for laser marking according to any one of (1) to (4). (6) The resin molded product according to (5), wherein the resin molded product is a container, a plate, or a film.
(7) A laser marking method characterized by applying a laser beam to the surface of the resin molded product of (5) or (6) to provide a mark, and (8) the type of laser beam is a YAG laser. ) Laser marking method, (9)
The present invention relates to the laser marking method according to (7) or (8), wherein the mark is a machine-readable mark, and (10) the laser marking method according to (9), wherein the machine-readable mark is a barcode.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic resin composition for laser marking of the present invention contains titanium dioxide as an active ingredient. The titanium dioxide is not particularly limited, and those commercially available for pigments and fine particle titanium dioxide can be used. Titanium dioxide for pigments can be either rutile or anatase. The particle size is not particularly limited, and is practically, for example, about several μm to several tens μm (weight average particle diameter). 0.1μ for fine titanium dioxide
It has the following particle size, for example, MT-500B manufactured by Teica (company). The amount of titanium dioxide used is not particularly limited, but is usually 0.05 to 70% by weight, preferably 0.1 to 70% by weight, based on the total amount of the resin composition for laser marking.
It is about 50% by weight, more preferably about 0.1 to 20% by weight.

The thermoplastic resin used in the present invention is, for example, a polyolefin resin. Examples of the polyolefin resin include polyethylene and polypropylene, and the melting index (M
The value of I) is preferably from 0.01 to 60, preferably from about 0.02 to 55.

Additives and the like can be added to the thermoplastic resin composition for laser marking of the present invention as needed. Examples of the additive include a colorant, a filler (fillers), a lubricant, and a plasticizer. The colorant that can be used is not particularly limited, but a colorant other than black is preferable, for example, phthalocyanine, azo, disazo, quinacridone, anthraquinone, flavanthrone, perinone, perylene, dioxazine, condensed azo, azomethine or methine-based Inorganic pigments such as organic dyes, lead sulfate, zinc oxide, chrome yellow, zinc yellow, chrome vermillion, red iron, cobalt violet, dark blue, chrome green, chromium oxide, and cobalt green. These organic,
The inorganic pigment is in a range that does not affect the sharpness of the formed mark, for example, 0.001 to 3 with respect to the polyolefin resin.
It is added in the range of weight%. It should be noted that even a black colorant can be used within a range that does not affect the accuracy of reading the colored mark by a machine. Examples of the filler include fillers usually used for polyolefin resins, such as silicon dioxide, mica, kaolins, blast furnace slag, silica compounds such as silica sand, diatomaceous earth, and talc, calcium carbonate, alumina, and glass fiber. These are in a range that does not affect the reading accuracy of the colored mark by a machine, for example, 0.001 to 7 for polyolefin resin.
It is added in the range of 0% by weight.

Examples of usable lubricants include stearic acid, behenic acid and esters or salts thereof, waxes such as carnauba wax and polyethylene wax, and various surfactants. These are added, if necessary, usually in a ratio of 0.1 to 5.0% by weight based on the polyolefin resin. Examples of the plasticizer include esters such as phthalic acid, phosphoric acid, and sebacic acid. others,
Additives commonly used in the processing of plastics, such as antioxidants, heat stabilizers, light stabilizers, and flame retardants, may be added. These additives may be used in the form of a powder or in the form of a masterbatch when preparing the polyolefin resin composition for marking of the present invention.

The thermoplastic resin composition for laser marking of the present invention is obtained by adding titanium dioxide powder and, if necessary, additives such as a coloring agent, a filler, a lubricant, a plasticizer and a heat stabilizer to a resin, preferably a polyolefin resin. In addition, it can be obtained by blending uniformly using a kneader such as an extruder, a twin-screw kneader, or a roll mill. The thermoplastic resin composition for laser marking of the present invention thus obtained is intact, and if necessary, further additives such as a thermoplastic resin such as a polyolefin resin or a filler are added, and a method known per se is used. Thus, the resin molded product of the present invention is manufactured. When the resin composition for laser marking of the present invention having a low content of titanium dioxide is produced, it may be produced in the same manner as described above using a master batch having a high concentration of titanium dioxide powder or the like. Master batches with high concentrations such as titanium dioxide powder are made by adding titanium dioxide and, if necessary, additives such as coloring agents, fillers, lubricants, plasticizers, and heat stabilizers to thermoplastic resins such as polyolefin resins. It is obtained by uniformly blending using a kneader such as a ruder, a twin-screw kneader, or a roll mill, and molding into a desired shape such as a pellet or marble.

Examples of the resin molded product include a two-dimensional molded product such as a film and a tape, and a three-dimensional molded product such as a plate, a container, a cap, and a part. These resin molded products may have a multilayer structure.

A two-dimensional molded product such as a film is formed by inflation processing, multilayer inflation processing, T-die film processing, simultaneous vertical and horizontal biaxial centrifugation using a flat film method, or vertical and horizontal sequential biaxial centrifugation used for forming a thermoplastic resin into a film. It is produced by a method known per se, such as a method and a tubular film method. Films produced in this way are used for ordinary thermoplastic resin films such as food packaging, textile packaging, miscellaneous goods packaging, medicine packaging, tapes, insulating materials, agricultural films, various sheets, various seals, labels, etc. Used in the same fields as Further, the film of the present invention can be laminated with various substrates, that is, papers such as kraft paper and woodfree paper, plastic films, metal foils such as aluminum and the like, and thus obtained. Examples of uses of the laminated product include food containers for milk and alcohol, packaging materials for pharmaceuticals, packaging materials for food, various sheets, various seals, labels, and the like.

The three-dimensional molded product used in the present invention is molded by a method known per se such as injection molding, extrusion molding, hollow molding, rotational molding, foam molding, powder molding, vacuum molding, etc., according to the molded product. . As specific examples, containers for food, detergent, pharmaceuticals, cosmetics, beverage products, etc. and their caps,
Food trays, tubes, medical containers, clothing, housing for home appliances, electrical supplies, household goods, automotive parts such as bumpers, automotive interior parts, audio equipment such as tape cassettes, information equipment supplies such as floppy disks, Pipes, building materials, industrial parts, various containers, clothing containers,
Various molded products mainly composed of generally available thermoplastic resins, such as multilayer containers, daily miscellaneous goods, various office machines, office supplies, identification plates, etc., can be mentioned. The identification plate is used, for example, for identifying livestock and containers.

The laser marking method of the present invention is performed by irradiating the surface of a resin molded product containing titanium dioxide with a laser beam. Examples of the laser light include a far-infrared laser such as a carbon dioxide gas laser (wavelength: about 10600 nm) and YAG (yttrium aluminum aluminum).
A near-infrared laser such as a garnet laser (wavelength: about 1060 nm), an excimer laser, and the like are preferable, and a YAG laser and an excimer laser are preferable. The mode of oscillation may be continuous oscillation or pulse oscillation, but a scan type of continuous oscillation is preferred. As the irradiation energy of the laser beam, for example, in the case of a YAG laser, the current value is 9 to 22, preferably 10 to 20 A, and the frequency is 1.4 to 5.5 kHz, preferably 1.8.
５5 kHz.

By irradiating the surface of the resin molded product containing titanium dioxide of the present invention with a laser beam, a clear contrast black-brown to black mark can be obtained on the irradiated portion. Examples of the mark include various marks such as a bar code, a color code, a logo mark, and a character symbol, and a machine-readable mark such as a bar code or a color code is preferable.

[0017]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following examples, “parts” means “parts by weight”. Further, in the examples, ○ indicates that a black-brown or black mark was obtained, and that the mark had good mechanical readability.
“X” indicates that the mark has poor mechanical readability or that only a white mark can be obtained. <Marking conditions> Apparatus: YAG laser ML-4140C manufactured by Miyachi Technos Co., Ltd. Marking method: One-stroke writing method Laser output (W): 50 Frequency (kHz): 1.8 Speed (mm / s): 80 Focal length (mm): 140 Barcode type: CODE39 Current value (A): 11 to 15 <Reading machine> Barcode reader Touch 7Σ manufactured by Welcat

Example 1 Polyethylene (HIZEX 1300 manufactured by Mitsui Petrochemical Co., Ltd.)
JMI: 30) and 100 parts of titanium dioxide for pigment (PS-2902 manufactured by Nippon Pigment) are kneaded at 180 ° C using a biaxial kneader, pulverized by a rotoplex mill, and the major axis is 1 mm or less. Was removed to obtain a marking composition of the present invention. This is molded into a plate at 200 ° C. using an injection molding machine (SAV-40 manufactured by Yamashiro Seiki, hereinafter referred to as an injection molding machine).
A YAG laser (Miyachi Technos, ML)
-4140C), a clear black mark was obtained, and the mechanical readability of the mark was good (○).

Example 2 Polyethylene (HIZEX 1300 manufactured by Mitsui Petrochemical Co., Ltd.)
JMI: 30) 100 parts, mica (Kuraray, Kuralite mica 600W, average particle size 8 μm) 0.5 part, titanium dioxide (Ishihara Sangyo, Taipaque CR-60) 1.0 part using a biaxial kneader. After kneading at 200 ° C. and pulverizing with a rotoplex mill, those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This was made into a film having a thickness of 0.1 mm at 180 ° C. using a 50-ton press, and the surface thereof was marked using a YAG laser (ML-4140C, manufactured by Miyachi Technos Co., Ltd.). As a result, a clear black mark was obtained. The mechanical readability of the mark was good (○).

Example 3 Polyethylene (HIZEX 1300 manufactured by Mitsui Petrochemicals)
JMI: 30) 100 parts, 0.1 part of mica (Kuraray Co., Ltd., Clarite Mica 600W, average particle size 8 μm), and 0.3 part of titanium dioxide (Ishihara Sangyo, Taipaque CR-60) are mixed. It was molded into a plate at 200 ° C. using an injection molding machine, and its surface was marked using a YAG laser (ML-4140C, manufactured by Miyachi Technos). A clear black mark was obtained, and the mark was mechanically read. The property was good (○).

Example 4 Polyethylene (HIZEX 1300 manufactured by Mitsui Petrochemicals)
J MI: 30) 100 parts, mica (Kuraray Co., Ltd., Clarite Mica 600W, average particle size 8 μm) 0.1 part, titanium dioxide (Ishihara Sangyo, Taipaque CR-60) 3.0 parts using a biaxial kneader. After kneading at 180 ° C. and pulverizing with a rotoplex mill, those having a major axis of 1 mm or less were removed to obtain a marking composition of the present invention. This was molded into a plate at 200 ° C. using an injection molding machine, and YA
G Laser (ML-4140C, manufactured by Miyachi Technos)
When the marking was performed using, a clear black mark was obtained, and the mechanical readability of the mark was good (（).

Comparative Example 1 Polyethylene (Shorex S500 manufactured by Showa Denko KK)
3BH MI: 0.3) using a 50 ton press to obtain 18
A film having a thickness of 0.5 mm at 0 ° C.
G gas laser (ML-4140, manufactured by Miyachi Technos)
When marking was performed using C), no machine-readable mark was obtained (x).

[0023]

According to the present invention, since a white titanium dioxide is used as an active ingredient, a thermoplastic resin composition for laser marking which does not affect the color tone of the resin can be obtained. By irradiating the surface of the molded article of the thermoplastic resin composition for laser marking with a laser beam, a clear black-brown to black mark can be obtained. Since this mark has high reading accuracy by a machine, it is particularly useful as a mark for reading a machine such as a bar code and a carla code.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FIG06K 1/12 B41J 3/00 Q 19/02 B41M 5/26 S

Claims (10)

[Claims] 1. A thermoplastic resin composition for laser marking, comprising titanium dioxide as an active ingredient. 2. The resin composition for laser marking according to claim 1, wherein the content of titanium dioxide is 0.05 to 70% by weight. 3. The thermoplastic resin composition for laser marking according to claim 1, wherein the thermoplastic resin is a polyolefin resin. 4. The thermoplastic resin composition for laser marking according to claim 3, wherein the polyolefin resin is polyethylene or polypropylene. 5. A resin molded article obtained by molding the thermoplastic resin composition for laser marking according to claim 1. 6. The resin molded product according to claim 5, wherein the resin molded product is a container, a plate or a film. 7. A laser marking method comprising irradiating a laser beam on the surface of the resin molded product according to claim 5 to give a mark. 8. The laser marking method according to claim 7, wherein the type of laser light is a YAG laser. 9. The laser marking method according to claim 7, wherein the mark is a machine-readable mark. 10. The laser marking method according to claim 9, wherein the machine-readable mark is a bar code.