JP2011016304A - Molded body for laser marking and laser marking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately apply a marking which is excellent in visibility without causing problems such as a layer separation, cracks, whitening and bleeding on the laminated interface of a double color molded part including a black color base layer and a transparent coating layer by irradiation of a laser beam.SOLUTION: The molded body for laser marking includes the double color molded part including the base layer and the coating layer which coats the base layer, and can carry out the marking on the laminated interface between the base layer and the coating layer by irradiating the base layer with the laser beam from the coating layer side. In the molded body for laser marking, the base layer is constituted of a thermoplastic resin composition containing 0.0001-0.05 pts.mass of a boride lanthanum (B) based on 100 pts.mass of a thermoplastic resin (A). The coating layer is constituted of a transparent thermoplastic resin (a) in the molded body for laser marking.

Description

The present invention relates to a molded article for laser marking capable of marking a laminated interface of a two-color molded part of a base layer and a coating layer by laser light irradiation. Specifically, a black base layer and a transparent coating layer are provided. The present invention relates to a molded article for laser marking capable of accurately marking with excellent visibility without causing problems such as delamination, cracks, whitening, and bleeding at the laminated interface of the two-color molded part.
The present invention also relates to a laser marking method for marking the molded article for laser marking.

  Conventionally, as a printing method that does not use ink, there has been proposed a laser marking method in which laser light is irradiated to print on the surface of a plastic molded body.

  In the laser marking method, a plastic molded body formed by kneading an additive that absorbs laser light into a thermoplastic resin is irradiated with laser light, and foamed on the surface of the laser light irradiated portion of the plastic molded body by the action of the additive. A thermal change such as decomposition, melting, carbonization, or vaporization is caused, and thereby white or black marking is applied with a difference in contrast with a non-irradiated portion of the laser beam.

  In addition, a method for marking a laminated interface portion of a two-color molded body composed of a base layer and a transparent coating layer covering the base layer by such a laser marking method has been proposed (for example, Patent Documents 1 and 2). .

  In this way, if it is a method of marking the laminated interface part of the two-color molded body, the marking part by laser light irradiation is coated with a coating layer, so the marking part has excellent wear resistance and is marked. The effect that the characters, symbols, symbols, etc. are maintained semipermanently is obtained. In other words, in order to perform marking with sufficient contrast by the laser marking method, it is necessary to increase the amount of laser light irradiation. As a result, the laser light irradiation surface becomes rough and the rough marking portion is exposed. In the molded product, the marking part is worn, deteriorated or deteriorated from the marking part, and the marked characters or the like cannot be visually recognized over time. . On the other hand, when marking is performed on the laminated interface part of a two-color molded body having a transparent coating layer, the roughened surface by this laser light irradiation is covered with the coating layer, so the marking part is worn and deteriorated. There is no fear of alteration. Compared to the case where a coating layer is provided after marking by laser beam irradiation, laser beam irradiation can be performed on a two-color molded body on which a coating layer has been formed in advance. It can be used as a product after marking, which is very advantageous in terms of process.

  However, in the past, when marking is performed by laser light irradiation on the laminated interface of the two-color molded body, a relatively clear black marking is obtained with good contrast on the white base layer of the two-color molded body by laser light irradiation. However, there is a problem that marking with sufficient contrast cannot be performed on the black base layer.

  That is, when the base layer of the two-color molded body for laser marking is black and conventionally white marking is performed by laser irradiation, carbon black is generally blended into the resin composition constituting the base and colored. However, the white marking is given by the dissociative foaming of the resin due to the laser light absorption of carbon black, but in this case, if the amount of carbon black is small, the contrast is sufficient for the non-irradiated part of the laser light Clear marking cannot be performed. In order to perform clear marking with excellent visibility, it is necessary to increase the blending amount of carbon black, but if the blending amount of carbon black is too large, the foaming of the resin becomes intense, so even in areas other than the laser irradiation part As a result of dissociative foaming, peeling at the interface between the base layer and the coating layer occurs in a wide range, and the marking portion appears blurred, or in the case of remarkable, the periphery of the marking portion is whitened over a wide range. . If the amount of laser light irradiation is increased in order to increase the contrast by suppressing the blending amount of carbon black, the coating layer will be cracked or interface peeling will occur. For example, as seen in Example 4 of Patent Document 1, even if the blending amount of carbon black is 0.1% by weight with respect to the resin, it is difficult to achieve both contrast and crack prevention.

International Publication WO2006 / 101063 JP 2007-106840 A

  The present invention solves the above-mentioned conventional problems, and causes problems such as delamination, cracks, whitening, and bleeding at the lamination interface of the two-color molded part composed of a black base layer and a transparent coating layer by laser light irradiation. An object of the present invention is to provide a laser marking molded body capable of accurately marking with excellent visibility without causing the occurrence, and a laser marking method using the laser marking molded body.

As a result of intensive studies to solve the above-mentioned problems, the present inventor used lanthanum boride (LaB ₆ ) as a colorant in place of carbon black conventionally used for resin coloring, thereby forming a black base layer. The system can be colored, and the laser beam irradiation can give clear white markings with good contrast without causing problems such as delamination, cracks, whitening, and bleeding. I found.

  The present inventor has been achieved on the basis of such findings, and the summary is as follows.

[1] It has a two-color molded part composed of a base layer and a coating layer that covers the base layer, and marks the laminated interface between the base layer and the coating layer by irradiating the base layer with laser light from the coating layer side. In the molded product for laser marking, the base layer contains (B) lanthanum boride 0.0001 to 0.1 parts by mass with respect to (A) 100 parts by mass of the thermoplastic resin. And the coating layer is made of (a) a transparent thermoplastic resin.

[2] The thermoplastic resin composition constituting the base layer has a carbon black content of 0.1 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin (A) or substantially contains carbon black. And (C) a colorant other than carbon black and lanthanum boride is not contained, or (C) a colorant other than carbon black and lanthanum boride is added to (A) 100 parts by mass of the thermoplastic resin. The molded article for laser marking according to [1], comprising not more than part by mass.

[3] The molded body for laser marking according to [1] or [2], wherein the base layer and the coating layer are co-molded by injection molding.

[4] The marking according to [1] to [3], wherein the laser light irradiation portion of the base layer has a higher brightness than the non-irradiation portion by laser light irradiation, thereby providing a visible marking. The molded object for laser marking in any one.

[5] The thermoplastic resin (A) is polycarbonate resin, alloy of polyphenylene ether resin and polystyrene resin, alloy of polyphenylene ether resin and polyamide resin, thermoplastic polyester resin, methyl methacrylate / acrylonitrile / butadiene / styrene copolymer resin. , A methyl methacrylate / styrene copolymer resin, a methyl methacrylate resin, a rubber-reinforced methyl methacrylate resin, a polyamide resin, a polyacetal resin, a polylactic acid resin, and a polyolefin resin [1] ] To [4], a molded article for laser marking.

[6] The molded article for laser marking according to any one of [1] to [5], wherein (a) the transparent thermoplastic resin is a polycarbonate resin.

[7] The laser marking molding according to any one of [1] to [6], wherein the thickness ratio of the coating layer to the base layer is coating layer / base layer = 1/9 to 9/1 body.

[8] A laser marking method, wherein the laser marking molded body according to any one of [1] to [7] is irradiated with a laser beam for marking.

[9] The laser marking method according to [8], wherein marking is performed by irradiating the molded body for laser marking with YAG laser light having a wavelength of 532 to 1064 nm or Nd: YVO ₄ laser light.

According to the present invention, the visibility of the laminated interface of the two-color molded part composed of a black base layer and a transparent coating layer is not caused by laser light irradiation without causing problems such as delamination, cracks, whitening, and bleeding. Can be marked with high accuracy.
According to the present invention, a highly durable marking protected by a coating layer can be accurately and efficiently formed into a desired shape under a clear and good contrast by laser light irradiation. The marking technology according to the present invention is extremely useful industrially in various fields such as electronic / electrical parts, medical equipment, automobile parts, various recording media, various display boards, and the like.

Embodiments of the present invention are described in detail below.
In the present invention, “marking” refers to the formation of characters, symbols, designs and the like. In the laser marking according to the present invention, the laser beam irradiation part is usually a laser beam on a black base layer. This is a marking technology that can be visually recognized by taking on a white color tone having a relatively high brightness with respect to a non-irradiated part.

[Molded body for laser marking]
The molded article for laser marking of the present invention has a two-color molded part composed of a base layer and a coating layer that covers the base layer, and the base layer and the coating are formed by irradiating the base layer with laser light from the coating layer side. In the molded article for laser marking capable of marking on the laminated interface with the layer, the base layer comprises (B) lanthanum boride 0.0001 to 0.1 parts by mass with respect to (A) 100 parts by mass of the thermoplastic resin. It is comprised with the thermoplastic resin composition to contain, and this coating layer is comprised with (a) transparent thermoplastic resin, It is characterized by the above-mentioned.

{Thermoplastic resin composition for base layer}
First, the thermoplastic resin composition constituting the base layer of the two-color molded part according to the present invention will be described. This thermoplastic resin composition contains at least (A) a thermoplastic resin and (B) lanthanum boride, and may contain other colorants and other additives as necessary.

<(A) Thermoplastic resin>
The thermoplastic resin constituting the base layer (A) is not particularly limited as long as it can be laser-marked as a resin composition containing lanthanum boride, and can be selected and used depending on the application. For example, polycarbonate resin Alloys of polyphenylene ether resin and polystyrene resin, alloys of polyphenylene ether resin and polyamide resin, thermoplastic polyester resin, methyl methacrylate / acrylonitrile / butadiene / styrene copolymer resin, methyl methacrylate / styrene copolymer resin, methyl methacrylate resin , Rubber reinforced methyl methacrylate resin, polyamide resin, polyacetal resin, polylactic acid resin, polyolefin resin and the like. When these thermoplastic resins are irradiated with laser light, side chains such as methyl group, methylene group, and amino group of the thermoplastic resin are dissociated, so that the laser light irradiation part is dissociated and foamed and interacts with lanthanum boride. Thus, marking is performed by exhibiting a white color tone with high brightness with respect to the laser light non-irradiated portion.

  Of these, polycarbonate resin is preferable because of particularly high surface impact.

  In addition, the said thermoplastic resin may be used individually by 1 type, and 2 or more types may be mixed and used for it.

<(B) Lanthanum boride>
In the present invention, lanthanum boride is used as a colorant or laser light energy absorber instead of conventional carbon black. Lanthanum boride is blended with resin to color the resin black according to the amount of the lanthanum boride, absorb the laser beam energy irradiated at the time of marking, and give marking due to dissociative foaming of the resin It exhibits a catalytic action.

In the present invention, if the blending amount of lanthanum boride is excessively small, the marking ability imparting effect due to blending it cannot be obtained, and if it is too much, the impact resistance is lowered and economically It is disadvantageous.
Therefore, the blending amount of lanthanum boride is 0.0001 to 0.1 parts by mass, preferably 0.001 to 0.05 parts by mass with respect to 100 parts by mass of (A) the thermoplastic resin.

  In addition, a commercial item can be used as lanthanum boride, and it is usually preferable to use lanthanum boride as a mixed powder containing zirconium oxide. Zirconium oxide has a role of well dispersing lanthanum boride in the resin. The amount of zirconium oxide used is preferably in the same range as the amount of lanthanum boride used.

<(C) Other colorant>
The thermoplastic resin composition for forming the base layer may contain a colorant other than lanthanum boride.
That is, by blending lanthanum boride, the resin composition can be colored black, but for the purpose of further improving the blackness and further diversification of color tone, a colorant other than lanthanum boride. May be blended.

  However, since carbon black causes delamination due to dissociative foaming, cracks, bleeding of marking, and whitening as described above, it is preferable to avoid carbon black, and substantially carbon black is blended. Even in such a case, the amount is less than the amount that does not cause adverse effects due to the carbon black compound, specifically 0.1 parts by mass or less, more preferably 0.05 parts by mass or less, particularly preferably 100 parts by mass with respect to the thermoplastic resin. Is preferably 0.03 parts by mass or less, and more preferably substantially free of carbon black. Here, “substantially does not contain” means that the resin composition does not contain more than 100 ppm.

  The thermoplastic resin composition for a base layer according to the present invention includes a colorant other than lanthanum boride and carbon black (in the present invention, this colorant is referred to as “(C) other colorant”). In the case of (C) other colorants, inorganic pigments, organic pigments, dyes and the like can be mentioned. Among these, examples of inorganic pigments include titanium oxide, barium sulfate, zinc sulfide, and zinc oxide as white pigments, iron oxide, titanium yellow as yellow pigments, iron oxide as red pigments, cobalt blue and ultramarine blue as blue pigments. Examples of organic pigments include monoazo, condensed azo, anthraquinone, disazo, heterocyclic ring for yellow, quinacridone, anthraquinone, perylene, monoazo for red, phthalocyanine for blue, and phthalocyanine for green. Further, examples of the dye include monoazo, anthraquinone, disazo, and heterocyclic ring for yellow, anthraquinone, perinone, thioindigo, disazo, and anthraquinone for blue. These colorants may be used alone or in combination of two or more.

  As (C) the other colorant, an organic pigment or a dye is preferable to the inorganic pigment, and a dye is particularly preferable because it may cause the same problem as that of carbon black.

  In the case of using the other colorant (C), if the blending amount is too small, the coloring effect due to blending it cannot be sufficiently obtained, and if it is too much, problems such as deterioration of physical properties of the molded product are caused. Since there is a possibility, the blending amount of (C) other colorant ((C) the total blending amount when two or more other colorants are used) is 0 with respect to 100 parts by mass of the thermoplastic resin. It is preferable to set it as 10 mass parts, especially 0-5 mass parts.

<Other additives>
In addition to lanthanum boride and (C) other colorants, the thermoplastic resin composition for a base layer according to the present invention contains various general additives that are usually blended in thermoplastic resin compositions. Also good.
Examples of such additives include mold release agents, stabilizers, antioxidants, ultraviolet absorbers, reinforcing agents, flame retardants, and the like, but are not limited thereto.

If the amount of these other additives is too small, the compounding effect cannot be obtained sufficiently, but if it is too large, other physical properties and moldability will be impaired. The blending amount of the agent is preferably 1 part by mass or less with respect to 100 parts by mass of the thermoplastic resin.
Further, the compounding amount of the reinforcing agent is preferably 100 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin, and the compounding amount of the flame retardant is preferably 30 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

{Transparent thermoplastic resin for coating layer}
Next, the transparent thermoplastic resin constituting the coating layer of the two-color molded part according to the present invention will be described.

  The transparent thermoplastic resin is not particularly limited as long as it is excellent in laser light transmittance and has high transparency without impairing the visibility of the marking portion. For example, polymethacrylstyrene resin (MS resin) AS resin, methyl methacrylate resin (PMMA resin), soft methyl methacrylate resin (soft PMMA resin), polycarbonate resin, polyethylene terephthalate resin, polycyclohexane 1,4-dimethyl phthalate resin, polystyrene resin, transparent ABS resin, polychlorinated A vinyl resin, a polypropylene resin, a polyethylene resin, etc. are mentioned. Among these transparent thermoplastic resins, methyl methacrylate resin, soft methyl methacrylate resin, polycarbonate resin, and polyethylene terephthalate resin are preferable from the viewpoint of surface hardness characteristics, and polycarbonate resin is particularly preferable because of excellent transparency.

  In addition, the transparent thermoplastic resin for the coating layer may be used as a resin composition by blending various additives in the same manner as the thermoplastic resin composition for the base layer. About the compounding quantity, it is the same as that of the thermoplastic resin composition for base layers.

{Thickness ratio}
The thickness ratio between the base layer and the coating layer of the two-color molded part according to the present invention is not particularly limited, but if the balance between the thickness ratio of the base layer and the coating layer is bad, the coating layer cracks during laser marking, May cause interfacial debonding. Accordingly, the thickness ratio of the base layer to the coating layer is preferably coating layer / base layer = 1/9 to 9/1, particularly 2/8 to 8/2, particularly 3/7 to 7/3.

  Note that the coating layer functions as a protective layer for the marking portion and does not need to be excessively thick. The thickness of the coating layer is usually 0.1 to 10 mm, particularly preferably about 0.3 to 5 mm.

  On the other hand, various thicknesses can be adopted for the base layer depending on the application, but it is usually about 0.1 to 10 mm.

{Layer structure}
The molded body for laser marking of the present invention may be a two-color molded body composed only of the base layer and the coating layer, or may be a multicolor molded body having a two-color molded portion composed of the base layer and the coating layer. Good. Further, the two-color molded part may be laminated and integrated with another member.

{Production method}
The molded article for laser marking of the present invention is most simply used by using the above-mentioned thermoplastic resin composition for a base layer and a transparent thermoplastic resin for a coating layer, and supplying them to an injection molding machine to perform two-color molding. It can be produced as a two-color molded body.
In addition, it is also possible to produce by multicolor formation of three or more colors, or coextrusion using a material for forming each layer.
As a co-molding method by injection molding, two different colors (two types) such as core back method, die slide method, rotary method, etc. are sequentially injected and filled into the mold from different injection cylinders, different materials Or the molding method which makes the molded article of a different color material is mentioned.

[Laser marking method]
The laser marking method of the present invention is characterized in that marking is performed by irradiating the above-described molded article for laser marking of the present invention with laser light.

The laser beam used in the laser marking method of the present invention is preferably one having a laser oscillation wavelength of 532 to 1064 nm which can be absorbed by lanthanum boride and can mark the laminated interface between the coating layer and the base layer. Modified yttrium-aluminum-garnet (YAG) or neodymium-modified yttrium-vanadium tetroxide (Nd: YVO ₄ ) can be used as a laser medium.

  As the laser marker, the laser beam may be either single mode or multi-mode, and the laser beam can be used not only with a narrow beam diameter of 20 to 40 μm but also with a wide beam diameter of 80 to 100 μm. However, in the single mode, the beam diameter of 20 to 40 μm is preferable because marking can be performed with good contrast.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  In addition, the compounding material of the resin composition used in the following Examples and Comparative Examples is as follows.

(A) Aromatic polycarbonate resin: Mitsubishi Engineering Plastics Co., Ltd. product “trade name: Iupilon (registered trademark) S-3000”, viscosity average molecular weight 22,000
(A) Aromatic polycarbonate resin: Mitsubishi Engineering Plastics Co., Ltd. product “trade name: Iupilon (registered trademark) S-3000”, viscosity average molecular weight 22,000
(B-1) Dispersed powder containing 10% by mass of lanthanum boride: Sumitomo Metal Mining Co., Ltd. product “trade name: KHGS-02” (the other component is zirconium oxide)
(X-1) Carbon Black: Product of Mitsubishi Chemical Corporation “Product Name: Mitsubishi Carbon Black # 1000”
(C-1) Blue Dye: LANXESS Co., Ltd. Product “Product Name: Macrolex Blue RR”
(C-2) Yellow Dye: LANXESS Co., Ltd. Product “Product Name: Macrolex Yellow 6G”
(C-3) Red dye: Sumika Finechem Co., Ltd. product “Product name: Sumiplast RedHL5B”
(E) Release agent: Pentaerythritol tetrastearate, manufactured by Nippon Oil & Fats Co., Ltd. “Product Name: Unistar H476”

[Examples 1 and 2 and Comparative Example 1]
Using the thermoplastic resin composition for the base layer and the transparent thermoplastic resin composition for the coating layer having the composition shown in Table 1, the resin temperature was 280 ° C. using an injection molding machine (Japan Steel Works “J150E-P-2M”). After forming the base layer at a mold temperature of 80 ° C. with a filling time of 1 second, a holding pressure of 50 MPa, and a cooling time of 60 seconds, the mold is slid to form a space, and the coating layer is filled with a filling time of 1 second, a holding pressure of 50 MPa, By performing two-color molding under the condition of a cooling time of 60 seconds, a two-color molded body having a base layer thickness of 2 mm and a coating layer thickness of 2 mm and having a total thickness of 4 mm of 100 mm × 100 mm was molded.

Using the YAG laser marker shown below from the coating layer side of this two-color molded body, laser beam irradiation was performed under the following conditions to mark the laminated interface between the base layer and the coating layer.
YAG Laser Marker: NEC Corporation “Product Name: SL475H”
(Single mode)
Laser light irradiation conditions: Laser light wavelength = 1.06 μm
Pulse frequency = 2kHz
Scanning speed = 100mm / s
Output = 10A

The visibility of the marking formed by laser light irradiation was visually observed and evaluated according to the following criteria.
○: The contrast with the non-irradiated portion of the laser beam is good and the visibility is excellent.
X: The contrast with a laser beam non-irradiation part is bad, and visibility is bad.

Moreover, the marking part was visually observed for bleeding or whitening due to interfacial peeling of the marking part, and evaluated according to the following criteria.
○: Marking is not blurred or whitened, and a marking with high accuracy following the laser light irradiation shape is formed.
X: Bleeding or whitening due to interfacial peeling is observed at or around the marking part.

These results are shown in Table 1.
In Table 1, the color tone of the base layer and the color tone of the marking portion are shown together.

  From Table 1, according to the present invention, the laser beam irradiation causes problems such as delamination, cracks, whitening, and bleeding at the lamination interface of the two-color molded part composed of the black base layer and the transparent coating layer. It can be seen that marking with excellent visibility can be performed with high accuracy.

Claims (9)

It has a two-color molded part composed of a base layer and a coating layer that covers the base layer, and by irradiating the base layer with laser light from the coating layer side, it is possible to mark the laminated interface between the base layer and the coating layer In molded products for laser marking,
The base layer is composed of (B) a thermoplastic resin composition containing 0.0001 to 0.1 parts by mass of lanthanum boride with respect to 100 parts by mass of the thermoplastic resin.
The covering layer is made of (a) a transparent thermoplastic resin, and is a molded article for laser marking.   The thermoplastic resin composition constituting the base layer has a carbon black content of 0.1 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin (A), or substantially does not contain carbon black, and Or (C) a colorant other than carbon black and lanthanum boride is not contained, or (C) a colorant other than carbon black and lanthanum boride is 10 parts by mass or less with respect to 100 parts by mass of (A) thermoplastic resin. The molded article for laser marking according to claim 1, comprising:   The molded body for laser marking according to claim 1 or 2, wherein the base layer and the coating layer are co-molded by injection molding.   The laser beam irradiation part of the said base layer is provided with the marking which can be visually recognized by becoming higher brightness than a non-irradiation part by irradiation of a laser beam. The molded object for laser marking as described.   The thermoplastic resin (A) is polycarbonate resin, alloy of polyphenylene ether resin and polystyrene resin, alloy of polyphenylene ether resin and polyamide resin, thermoplastic polyester resin, methyl methacrylate / acrylonitrile / butadiene / styrene copolymer resin, methyl meta 5. At least one selected from the group consisting of an acrylate / styrene copolymer resin, a methyl methacrylate resin, a rubber-reinforced methyl methacrylate resin, a polyamide resin, a polyacetal resin, a polylactic acid resin, and a polyolefin resin. The molded article for laser marking according to any one of the above.   The molded article for laser marking according to any one of claims 1 to 5, wherein (a) the transparent thermoplastic resin is a polycarbonate resin.   The molded product for laser marking according to any one of claims 1 to 6, wherein a thickness ratio between the coating layer and the base layer is coating layer / base layer = 1/9 to 9/1.   A laser marking method, comprising: irradiating a laser beam on the molded article for laser marking according to any one of claims 1 to 7 for marking. The YAG laser light or Nd wavelength 532~1064nm laser marking article for: YVO ₄ laser marking method according to claim 8 which is irradiated with laser light and performing marking.