JPH06297828A - Laser marking method and laser-marked molded product - Google Patents

Abstract

(57) [Abstract] [Purpose] Using laser light, a mark such as a clear character or symbol of a desired color is provided on the surface of a thermoplastic resin molded product or a molded product coated with the resin. [Structure] In a method of marking by irradiating a laser beam on the surface of a molded article molded from a thermoplastic resin, an additive that discolors or decolorizes by absorbing the laser beam and being heated, and the influence of the laser beam Difficult organic pigment
A surface of a molded article molded from a thermoplastic resin composition containing a dye together is irradiated with laser light for marking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser for applying a mark such as a clear character or symbol of a desired color to the surface of a thermoplastic resin molded product or a molded product coated with the resin by utilizing a laser beam. TECHNICAL FIELD The present invention relates to a marking method and a molded article that is satisfactorily marked by the marking method.

[0002]

2. Description of the Related Art Many methods have already been proposed as a method for marking a thermoplastic resin by irradiating it with a laser beam, and (1) a change in the surface state due to the etching of the irradiated part. There are known a method of marking by (roughening and depression) and a method of (2) marking by adding a discolorable and decolorizable filler. However, in most cases, the color of the marking characters obtained in the prior art is the black character due to carbonization of resin,
Alternatively, only white characters due to the added pigment / dye can be obtained, and it is impossible to obtain marking characters of any color.

[0003]

DISCLOSURE OF THE INVENTION In view of the above-mentioned prior art, the present inventor diligently studied the diversification of the color of laser marking characters, and as a result, it was found that many organic pigments and dyes are stable to laser light. As a result of further studying the application of these organic pigments / dye to the laser marking method, the present invention has been completed. That is, the present invention is a method of irradiating the surface of a molded article molded from a thermoplastic resin with a laser beam for marking, and an additive that discolors or decolorizes by absorbing the laser beam and heating, and the effect of the laser beam. Laser marking method characterized by irradiating a laser beam on the surface of a molded article molded from a thermoplastic resin composition containing an organic pigment / dye which is hard to receive, and a thermoplastic resin In a method of irradiating a laser beam on the surface of a molded article for marking, molding formed from a thermoplastic resin composition containing an additive that discolors or decolorizes by absorbing laser light and being heated Specially, the product is dyed with a dye that is not easily affected by laser light, and then the surface of the molded product is irradiated with laser light for marking. In the laser marking method, and in the method of marking by irradiating the surface of a molded article molded from a thermoplastic resin with a laser beam, containing an additive that discolors or decolorizes by absorbing the laser beam and being heated. The laser marking method is characterized in that the surface of a molded product molded from the thermoplastic resin composition is irradiated with a laser beam to perform marking, and then the molded product is dyed with a dye.

The laser marking method of the present invention will be described in detail below. First, the thermoplastic resin used in the present invention is not particularly limited, and examples thereof include polyolefin resins such as polyethylene and polypropylene, polystyrene resins, polyvinyl chloride resins, poly (meth) acrylate resins, acrylic resins. Any known thermoplastic resin such as resin, polyacetal resin, polyethylene terephthalate, polybutylene terephthalate, polyester resin such as liquid crystalline polyester, polyamide resin, polycarbonate resin, polyphenylene sulfide resin, and polyimide resin can be used. These resins may be used alone or in combination of two or more. Among these resins, in the present invention, a polyolefin resin, a polystyrene resin, a poly (meth) acrylate resin, which is hard to be carbonized by heating with a laser,
Acrylic resins, polyacetal resins, and polyester resins are preferable, and polyacetal resins and polyester resins are particularly preferable. When such resins are used, particularly vivid color marking is possible. Here, the polyacetal resin used in the present invention is a polymer compound having (-CH ₂ O-) as a main constituent unit, and a polyoxymethylene homopolymer, a copolymer containing a small amount of another constituent unit other than an oxymethylene group (block (Including a copolymer) or a terpolymer, and the molecule may have not only a linear structure but also a branched or crosslinked structure. Further, there is no particular limitation on the degree of polymerization or the like. Examples of the thermoplastic polyester resin include polyalkylene terephthalate resins such as polyethylene terephthalate and polybutylene terephthalate.

In the first method of the present invention, an additive that discolors or decolors by absorbing a laser beam and being heated, and an organic pigment / dye which is hardly affected by the laser beam are added to the above resin. It is characterized in that the surface of a molded product molded from the resin composition is also irradiated with laser light for marking. In the second method, the resin as described above is mixed with an additive that discolors or discolors when heated by absorbing a laser beam, and a molded article molded from the resin composition is treated with a laser beam. It is characterized in that it is dyed with a dye which is not easily affected and then the surface of the molded product is irradiated with laser light for marking. In the third method, the resin as described above is mixed with an additive that discolors or bleaches when heated by absorbing a laser beam, and a laser beam is applied to the surface of a molded article molded from the resin composition. Is applied to perform marking, and then the molded product is dyed with a dye to obtain a marking of a desired color.

In the method of the present invention, examples of the additive that discolors or decolorizes by absorbing laser light and being heated include carbon black, iron oxide, ultramarine blue, titanium oxide, titanium yellow and the like. Carbon black is preferable. The blending amount is preferably 0.01 to 0.5% by weight. 0.01% by weight of carbon black
If it is less than 0.5%, marking with sufficient contrast cannot be carried out. On the other hand, if it exceeds 0.5% by weight, the surface of the resin molded product is severely etched by laser irradiation, and marking with good contrast becomes difficult. For clearer marking, the carbon black content should be 0.03 to 0.3.
It is particularly preferable that the content is wt%. Carbon black
Furnace black, channel black, thermal black and the like are classified according to the manufacturing method, and acetylene black, oil black, gas black and the like are classified according to the raw material, and any of them can be used in the present invention. It is also possible to use Ketjen Black. By irradiating the surface of a molded product made of a thermoplastic resin composition containing such a low concentration of carbon black or a molded product coated with the resin composition with a laser beam, the laser irradiation part is generally Markings with good contrast can be obtained with a very slight protrusion, for example, about 5 to 50 μm.

Further, in the first method of the present invention, an organic pigment which is hard to be influenced by laser light, which is blended with the above-mentioned additive in order to obtain a marking character of a desired color,
The dye is not particularly limited as long as it is not easily affected by laser light and can color and dye the thermoplastic resin. Here, the organic pigment that is hardly affected by the laser light means a material having high heat resistance that is unlikely to cause discoloration or decolorization even when exposed to the laser light, and examples thereof include anthraquinone-based, perylene-based, and isoindolinone. System, phthalocyanine series, and polyazo series pigments. The dye is selected from disperse dyes, sublimable dyes, cationic dyes, basic dyes, and the like, which are unlikely to cause discoloration or decolorization even when exposed to laser light. Particularly preferred are hydrophobic dyes (disperse dyes) developed for dyeing hydrophobic fibers. Also, in the second method of the present invention, since laser irradiation is performed after dyeing a molded product, a dye for dyeing a molded product is one that is unlikely to cause discoloration or decolorization by laser light as described above. Must be used. On the other hand, in the third method of the present invention, dyeing is performed after laser irradiation, and there is no particular limitation as a dye.

In the present invention, the resin composition as described above, which is molded or coated and used for laser marking, contains known additives and inorganic fillers, if necessary, as long as the marking by laser irradiation is not impaired. Etc. can be added. For example, antioxidants, heat resistance stabilizers, ultraviolet absorbers, stabilizers such as light stabilizers, antistatic agents, colorants such as dyes and pigments, lubricants, plasticizers, release agents, surfactants,
It is also possible to add a crystallization accelerator, a crystal nucleating agent and the like.

In the present invention, any of the above-mentioned first to third methods is possible, but the first method is particularly preferable, and a molded article made of the above-mentioned specific resin composition or the resin composition is printed, Resin coated by coating, multiple molding, etc.,
By simply irradiating a desired position with a laser beam on a molded product such as ceramic or metal, clear marking can be easily performed. In order to mark the desired shape,
For example, a method of scanning the surface of an object with a spot of laser light having an appropriate size, a method of irradiating the surface of the object with laser light having a desired shape by masking the laser light, and the like can be given. . The type of laser used is not particularly limited, and examples thereof include carbon dioxide laser, ruby laser, semiconductor laser, argon laser, excimer laser, and YAG laser. Among them, N characterized by a wavelength of 1.06 μm
The d: YAG laser is preferred. The oscillation mode may be continuous oscillation or pulsed oscillation, but a particularly suitable one is a scan type Nd: YAG laser which is continuous oscillation using a Q switch.

[0010]

The action mechanism of the present invention is presumed as follows, taking the first method as an example. That is, as in the present invention, heat containing an additive (for example, carbon black) that discolors or bleaches when it absorbs laser light and is heated, and an organic pigment / dye that is not easily affected by laser light. When the surface of a molded product molded from a plastic resin composition or the surface of a molded product coated with the resin composition is irradiated with laser light, the laser light passes through the surface of the molded product and selectively heats carbon black in the resin. To do. Especially in the case of Nd: YAG laser, which is less absorbed by the resin itself, it is heated efficiently. The heated carbon black heats and melts the surrounding resin to locally decompose it, and at the same time, the carbon black itself is oxidized by excessive heating and becomes a gas. Therefore, a foamed region where carbon black does not exist is formed in the portion irradiated with the laser light. In the case of this molded product in which the color of the organic pigment / dye is hidden by carbon black, the color of the concealed organic pigment / dye appears due to the formation of a region where carbon black does not exist, and the added organic pigment / dye A laser marking character identical to the dye color is obtained. In particular, it is considered to be achieved by using an organic pigment / dye that does not absorb laser light or undergo discoloration or decolorization by heating, that is, hardly affected by laser light.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 0.05% by weight of carbon black in polyacetal resin
And 1% by weight of the following dye a was added and kneaded with an extruder,
A blackish pellet was obtained. Injection molding this pellet,
A black flat plate having a size of 7 mm × 5 mm and a thickness of 3 mm was formed. next,
When this flat plate was marked under the following conditions, clear marking characters of the same color as the dye (in this case, pink) were obtained. Also, when the following b and c were used as dyes and the addition amount of carbon black was 0.1% by weight, the same operation was carried out. As a result, a clear color of the same color (dark blue for b, yellow for c) was obtained. Got the marking letters.

Example 2 To a polyacetal resin, 0.05% by weight of carbon black was added and kneaded with an extruder to obtain black pellets. The pellet was injection-molded to form a black flat plate having a size of 7 mm × 5 mm and a thickness of 3 mm. Next, this flat plate was dyed with the following dye a in water to obtain a dyeing aqueous solution having a concentration of 2 g / liter (water temperature: 90
C.) for 10 minutes and then washed with water. After dyeing, the plate was marked under the following conditions, and clear marking characters of the same color as the dye (in this case, pink) were obtained. Also, when carbon black was added in an amount of 0.1% by weight and the following dyes b and c were used for the immersion treatment for 30 minutes, the same treatment was carried out. As a result, the same color as the dye (dark blue in the case of b, c
In that case, clear marking characters (yellow) were obtained.

Example 3 To a polyacetal resin, 0.05% by weight of carbon black was added and kneaded with an extruder to obtain black pellets. The pellet was injection-molded to form a black flat plate having a size of 7 mm × 5 mm and a thickness of 3 mm. Next, this flat plate was marked under the following conditions to obtain white characters. Then, this plate was immersed in a dyeing aqueous solution (water temperature: 90 ° C.) having a concentration of 2 g / liter in which the following dye a was dissolved in water for 10 minutes, and then washed with water to obtain clear marking characters of the same color (pink in this case) Obtained. When carbon black was added in an amount of 0.1% by weight and the following dyes b and c were used for the immersion treatment for 30 minutes, the same treatment was carried out. As a result, the same color as that of the dye (dark blue for b, and c for (Yellow) clear marking characters were obtained.

The marking conditions are as follows. Device: NEC Corporation Laser marker SL475E Laser type: Nd: YAG laser (with Q switch) Marking method: One-stroke writing method (scan method) Processing power at the marking part: 1-3W Scan speed: 100-400mm / sec Byte size: 30 to 50 μm Q switch frequency: 1 to 3 kHz The dyes a to c used in the examples are disperse dyes manufactured by Mitsubishi Kasei. a; Dianix Red AC-E b; Dianix Blue AC-E c; Diacelliton Fast Yellow GL

[0015]

The laser marking technology for a thermoplastic resin has hitherto been known as an excellent surface decoration method in terms of unmanned operation, automation, solvent-free operation, reliability, etc. The field of application was very limited because of the black or white achromatic color, but according to the present invention, the color of the marking characters obtained is diversified, so that the field of application is expanded and the economic value is high.

Claims (7)

[Claims] 1. In a method of irradiating a surface of a molded article molded from a thermoplastic resin with a laser beam for marking, an additive that discolors or decolorizes by absorbing the laser beam and being heated, and the influence of the laser beam. A laser marking method, which comprises irradiating a surface of a molded article molded from a thermoplastic resin composition containing an organic pigment / dye, which is difficult to receive, together with a dye, with laser light for marking. 2. A method of irradiating a surface of a molded article molded from a thermoplastic resin with a laser beam for marking, the heat comprising an additive that discolors or decolorizes by absorbing the laser beam and being heated. A laser marking method characterized by dyeing a molded article molded from a plastic resin composition with a dye that is not easily affected by laser light, and then irradiating the surface of the molded article with laser light for marking. 3. A method of marking by irradiating a laser beam on the surface of a molded article molded from a thermoplastic resin, wherein the heat containing an additive that discolors or decolorizes by absorbing the laser beam and being heated. A laser marking method characterized by irradiating a surface of a molded article molded from a plastic resin composition with laser light to perform marking, and then dyeing the molded article with a dye. 4. An additive that discolors or decolorizes by absorbing laser light and being heated is carbon black,
The compounding amount thereof is 0.01 to 0.5% by weight in the composition.
4. The laser marking method according to any one of 3 to 3. 5. The laser marking method according to claim 1, wherein the marking is performed using a scan type Nd: YAG laser. 6. The laser marking method according to claim 1, wherein the thermoplastic resin is mainly composed of a polyacetal resin or a thermoplastic polyester resin. 7. A molded product marked by the laser marking method according to claim 1.