JP7175185B2 - Resin composition for laser marking and sheet for laser marking - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laser marking resin composition capable of marking the surface of a plastic sheet with a laser beam without damage, and to a laser marking sheet obtained by forming the resin composition into a sheet.

In recent years, as a printing method that does not use ink, it is widely used for ID cards, tag cards, credit cards, display boards, authentication plates, cash cards, ETC cards, and the like. Various laser marking methods have been proposed in which this sheet is irradiated with a laser beam to print on a plastic molded product. Carbon black, titanium black, metal nitrides, metal sulfides, and the like, for example, are used as the laser beam energy absorber (Patent Document 1).

However, when conventional laser beam energy absorbers are applied to plastic sheets, various problems arise. For example, depending on the laser marking conditions of the energy absorbing agent of the laser beam, there is a problem that the gas generated during marking swells or damages the transparent skin layer. Moreover, depending on the type of resin, there may be some problems with heat resistance.

JP 2010-194757 A

The present invention provides a plastic sheet widely used for ID cards, tag cards, credit cards, display boards, authentication plates, cash cards, ETC cards, etc., which has no external damage or foaming, has good contrast, and has excellent surface properties. To provide a resin composition for laser marking, which enables laser marking with excellent smoothness and has excellent heat resistance, and a sheet for laser marking using the same.

The present invention consists of claims 1 to 10 below.
<Claim 1>
(A) Per 100 parts by weight of the thermoplastic resin, (B) at least one laser beam energy absorber selected from the group consisting of carbon black, titanium black, metal oxides, metal nitrides, and metal sulfides (however, , excluding the following components (C) to (D)) 0.0005 to 0.1 parts by weight, (C) antimony-doped tin oxide (ATO), tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), aluminum 0.05 to 1.5 parts by weight of at least one composite metal oxide selected from the group consisting of doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), tin-doped zinc oxide, and silicon-doped zinc oxide, and ( D) A resin composition for laser marking, containing 0.05 to 1.5 parts by weight of a silicate mineral.
<Claim 2>
(A) The thermoplastic resin is polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, AS resin, ABS resin, polycarbonate, polyamide, polyester, polylactic acid resin, cellulose resin, vinyl chloride resin, polyoxymethylene 2. The resin composition for laser marking according to claim 1, which is at least one selected from the group consisting of , polyethersulfone, polyetheretherketone, and acrylic resin.
<Claim 3>
3. The resin composition for laser marking according to claim 1, wherein (B) the laser light energy absorbing agent is carbon black.
<Claim 4>
4. The resin composition for laser marking according to claim 1, wherein (C) the composite metal oxide is antimony-doped tin oxide (ATO) and/or tin-doped indium oxide (ITO).
<Claim 5>
(D) The resin composition for laser marking according to any one of claims 1 to 4, wherein the silicate mineral is mica.
<Claim 6>
A laser marking sheet obtained by calendaring or melt extruding the resin composition for laser marking according to any one of claims 1 to 5.
<Claim 7>
A multi-layer laser marking sheet obtained by laminating (A) a thermoplastic resin sheet according to claim 1 on at least one surface of the laser marking sheet according to claim 6.
<Claim 8>
A multi-layer laser marking sheet obtained by laminating the laser marking sheet according to claim 6 on at least one surface of (A) a thermoplastic resin sheet according to claim 1.
<Claim 9>
The thermoplastic resin (A) according to claim 1 and the resin composition for laser marking according to any one of claims 1 to 5 are melt-coextruded, for multilayer laser marking according to claim 7 or 8. Sheet manufacturing method.
<Claim 10>
Claim 7, characterized in that the sheet made of the thermoplastic resin (A) according to claim 1 and the sheet made of the resin composition for laser marking according to any one of claims 1 to 5 are press-molded. 9. The method for producing a multilayer laser marking sheet according to 8 above.

According to the present invention, a plastic sheet widely used for ID cards, tag cards, credit cards, display boards, authentication plates, cash cards, ETC cards, etc., has no external damage or foaming, and has good contrast. It is possible to provide a resin composition for laser marking, which enables laser marking with excellent surface smoothness and excellent heat resistance, and a sheet for laser marking using the same.

The resin composition for laser marking of the present invention comprises (A) a thermoplastic resin, (B) a laser light energy absorber, (C) a composite metal oxide, and (D) a silicate mineral, which are three-component systems. A resin composition for laser marking that does not damage or foam the appearance, has good contrast, enables laser marking with excellent surface smoothness, and has excellent heat resistance, and also for laser marking using the same. sheet can be provided.
(A) thermoplastic resin, (B) laser beam energy absorber, (C) composite metal oxide, and (D) silicate mineral are described below.

(A) Thermoplastic resin (A) The thermoplastic resin is not particularly limited as long as it is a thermoplastic resin capable of forming a sheet. Examples include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, AS resin, and ABS resin. , polycarbonate, polyamide, polyester, polylactic acid resin, cellulose resin, vinyl chloride resin, polyoxymethylene, polyethersulfone, polyetheretherketone, and acrylic resin.
Among them, polycarbonate, heat-resistant PETG [polycarbonate/PETG (cyclohexanedimethanol cocondensation PET) polymer alloy], and vinyl chloride resins are preferable.

In particular, vinyl chloride resin (PVC) has a lower heat-sealing temperature than heat-resistant PETG, so it has good press moldability (pressing equipment is simple and there is little print cracking). (printing, punching, sublimation transfer printing, embossing)

Here, the vinyl chloride-based resin is not particularly limited in type, and examples thereof include vinyl chloride homopolymers, vinyl acetate-vinyl chloride copolymers, ethylene-vinyl chloride copolymers, propylene-vinyl chloride copolymers. Copolymers, chlorinated vinyl chloride copolymers, crosslinked vinyl chloride copolymers and the like can be used, and these can be used alone or in mixtures of two or more.

The vinyl chloride resin preferably contains one or more modifiers selected from synthetic rubbers and styrene resins. As a result, the mechanical strength of the card can be greatly improved without impairing the adhesion. The content of this modifier is preferably 2 to 50 parts by weight per 100 parts by weight of the vinyl chloride resin. If the content is less than 2 parts by weight, a sufficient improvement in mechanical strength cannot be expected. Therefore, it is not preferable. Among them, 2 to 15 parts by weight is more preferable.

Examples of the synthetic rubber include, but are not limited to, EPR (ethylene-propylene rubber), BR (butadiene rubber), SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), acrylic rubber, Silicone rubber, fluorine rubber, and the like can be mentioned.
Examples of the styrene resin include, but are not limited to, ABS resin (acrylonitrile-butadiene-styrene copolymer), MBS (methyl methacrylate-butadiene-styrene copolymer), AAS (acrylic rubber-acrylonitrile -styrene copolymer), ACS resin (acrylonitrile-chlorinated polyethylene-styrene copolymer), and the like.
Among them, it is more preferable to use MBS resin and ABS resin as the modifier. In this case, the mechanical strength can be further improved with a small addition amount.

A stabilizer can be added to the vinyl chloride resin.
Examples of the stabilizer include lead-based stabilizers, tin-based stabilizers, and soap-based stabilizers such as calcium and zinc stabilizers.
The above stabilizer should be contained in an amount of 0.5 to 5 parts by weight per 100 parts by weight of the vinyl chloride resin. If the amount is less than 0.5 part by weight, a sufficient effect of stabilizing the resin cannot be obtained, making it difficult to process the resin into a sheet. On the other hand, if the amount exceeds 5 parts by weight, the physical properties such as strength deteriorate, and the stabilization effect cannot be expected to match the increase in the amount added, resulting in an increase in cost. Among them, the content is preferably 1 to 3 parts by weight with respect to 100 parts by weight of the vinyl chloride resin.

In addition, various additives such as plasticizers, pigments, fillers (calcium carbonate, talc, etc.), antistatic agents, lubricants, flame retardants, impact resistance improvers, and ultraviolet absorbers are necessary in the vinyl chloride resin. It can be blended as appropriate. In particular, pigments are often blended to impart hiding power, and white pigments are particularly preferably used, and among these, titanium oxide, which is inexpensive and has excellent hiding power, is more suitable. The amount of the pigment compounded is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the vinyl chloride resin. If it is less than 1 part by weight, it is not preferable because sufficient concealing property cannot be ensured. I don't like it. Among them, 5 to 15 parts by weight is more preferable. Furthermore, various polymers (synthetic resins) can be blended into the vinyl chloride resin as long as the effects of the present invention are not impaired.

(B) Laser light energy absorber (B) Laser light energy absorber includes at least one selected from the group consisting of carbon black, titanium black, metal oxides, metal nitrides, and metal sulfides.

Here, the average particle size of carbon black, titanium black, metal oxides, metal sulfides and metal nitrides is 10 μm or less, preferably 5 μm or less. If the thickness exceeds 10 μm, the sheet surface will have bumps and unevenness.
Here, the average particle size refers to (B) the laser light energy absorber itself, which is determined by a test method such as JIS Z 8825 laser diffraction analysis method, JIS Z 8828 dynamic light scattering method, and JIS Z 8815 sieving test method. is a value that can be
Furthermore, when the (B) laser beam energy absorbing agent is a material composed of aggregates of primary particles, the primary particle diameter is preferably 20 nm or more, more preferably 40 nm or more. If the primary particle size is less than 20 nm, the coloring power becomes high, and the hue of the sheet becomes black, which is not preferable. The size of primary particles can be measured with an electron microscope or the like.
Here, the primary particles are single crystal particles that are aggregates of tens of thousands to millions or more of molecules due to intermolecular mutual forces such as hydrogen bonding and van der Waals forces. Since the primary particles are very small, they are usually identified as aggregates or fused bodies thereof, or aggregates of said aggregates or fused bodies. It is the average particle size referred to here.
Taking carbon black as an example, carbon black exists as a fused body of primary particles called an aggregate, which is the minimum structural unit, or as an agglomerate in which aggregates are further aggregated, and the size of the aggregate or the size of the agglomerate is the average particle size referred to here.

As metal oxides, metals forming oxides include zinc, magnesium, aluminum, iron, titanium, silicon, antimony, tin, copper, manganese, cobalt, bismuth, vanadium, niobium, molybdenum, ruthenium, tungsten, palladium, silver, platinum and the like.
Metal sulfides include zinc sulfide and cadmium sulfide. Furthermore, titanium nitride etc. are mentioned as a metal nitride.
As described above, carbon black, titanium black and metal oxides are preferably used as the laser light energy absorber, and each of them may be used alone or in combination.

The amount of the laser light energy absorber (B) added is 0.0005 to 0.1 parts by weight, preferably 0.001 to 0.05 parts by weight, per 100 parts by weight of the thermoplastic resin (A). . If the amount is less than 0.0005 parts by weight, no color develops upon receiving laser light energy. On the other hand, if the amount exceeds 0.1 parts by weight, the film will turn black and the vividness of printed card images will be reduced.

(C) Composite Metal Oxide The (C) composite metal oxide, when used in combination with the (B) laser beam energy absorber, has the effect of efficiently coloring the laser beam.
Specifically, (B) the laser light energy absorber has an excellent property of developing a black color when exposed to laser light, but has the disadvantage that the sheet to which it is added becomes black because the material itself is blackish. On the other hand, the (C) composite metal oxide has a smaller effect of blackening the sheet itself than the (B) laser beam energy absorber, but it is poor in color development by laser light.
By combining these two kinds of compounds, it is possible to make the sheet to which the compound is added excellent in color developability (property of developing a black color) by laser light without being tinged with black.

(C) Composite metal oxides include antimony-doped tin oxide (ATO), tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and tin-doped. At least one selected from the group of zinc oxide and silicon-doped zinc oxide, preferably antimony-doped tin oxide (ATO), tin-doped indium oxide (ITO), more preferably antimony-doped tin oxide (ATO ).
Specific examples of antimony-doped tin oxide (ATO) include NYAOL SN903SD manufactured by Nyacol Nano Technologies.
A specific example of tin-doped indium oxide (ITO) is "ITO-R" manufactured by CIK Nanotech.

(C) The composite metal oxide is 0.05 to 1.5 parts by weight, preferably 0.1 to 1 part by weight, per 100 parts by weight of the thermoplastic resin (A). If the amount added is less than 0.05 parts by weight, sufficient color development may not be obtained even in combination with (B) the laser light energy absorber. If the intensity is too strong, burns and streaks may occur on the irradiated area, resulting in poor appearance.

(D) Silicate Mineral The (D) silicate mineral in the resin composition for laser marking of the present invention suppresses foaming caused by gas generated in the irradiated portion during laser marking.
Here, silicate minerals have a tetrahedral structure in which a silicon atom is surrounded by four oxygen atoms. The degree to which these tetrahedrons are connected differs depending on the type of mineral, and there are a wide variety of types, such as singly, paired, clustered, ring, chain, double-stranded, layered, and three-dimensional networks. Silicate minerals are classified according to the difference in this anion structure.

Here, silicate minerals are
Nesosilicate minerals (tetrahedral simple substance) (olivine, garnet, etc.),
Sorosilicate minerals (tetrahedral dimers) (vesuvianite, epidote, etc.),
Cyclosilicate minerals (cyclic) (beryl, tourmaline, etc.),
Inosilicate minerals (single-chain) (pyroxene, etc.),
Inosilicate minerals (double-stranded) (amphiboles, etc.),
Phyllosilicate minerals (layered) (such as micas and clay minerals),
Tektosilicate minerals (three-dimensional network) (quartz, feldspars, zeolites, etc.)
etc.
In the present invention, since the (D) silicate mineral is mainly used as a foaming inhibitor, lamellar micas are particularly preferred.
Examples of micas (mica) include natural mica such as muscovite, phlogovite, biotite and sericite, and synthetic mica such as fluorophlogopite and fluorotetrasilicon mica.

The amount of the (D) silicate mineral added is 0.05 to 1.5 parts by weight, preferably 0.1 to 1 part by weight, per 100 parts by weight of the thermoplastic resin (A). If the amount added is less than 0.05 parts by weight, foaming occurring in the irradiated area cannot be suppressed. lower.

In the present invention, the (D) silicate mineral such as mica may be (B) a laser beam energy absorber, or (C) mica coated with a composite metal oxide. Such surface-coated mica is available from Merck Ltd. under the trade names of "Laserflare LS820" (coated metal oxide: titanium oxide, silicon oxide, antimony oxide-doped tin oxide), "Laserflare LS825" (coated metal oxide: oxide Antimony-doped tin oxide), "Laserflare LS830" (coated metal oxide: titanium oxide, iron oxide black), "Laserflare LS835" (coated metal oxide: iron oxide black), etc. are obtained and used in the present invention. can.

Further, the resin composition for laser marking of the present invention can be colored in various hues by using various coloring agents such as inorganic pigments, organic pigments and organic dyes. In addition, the resin composition for laser marking of the present invention may optionally contain various other additives such as stabilizers, antioxidants, antistatic agents, waxes, and UV inhibitors. Furthermore, flame retardants and various fillers can be blended as needed.

Further, the resin composition for laser marking of the present invention may be a simple mixture of the components (A) to (D) and the powder of each component, or may be a mixture obtained by melt-kneading and granulating them into pellets.

When producing a laser marking sheet using the above resin composition, although not particularly limited, each of the above components is blended with a kneader, a mixer, a ribbon blender, etc., and the blended product is processed with an extruder, etc. Pellets are processed into sheets by calender molding, extrusion molding, inflation molding, press molding, or by dissolving the blended material or pellets in an organic solvent and then casting them into sheets. be. Among these, when calendar molding is performed, the resin composition is usually made to contain a lubricant. Lubricants include hydrocarbons such as paraffin wax, fatty acids such as stearic acid, fatty acid amides such as stearylamide, fatty acid esters, alcohols, metal soaps, and polymeric processing aids such as acrylic resins. is mentioned.
When the sheet of the present invention is formed by calendering, in the case of one layer, the resin composition for laser marking of the present invention is formed into a sheet by ordinary calendering.

When the sheet of the present invention is a multi-layer laser marking sheet, for example, the resin composition for laser marking of the present invention is used to prepare a sheet for laser marking, while the sheet is separately used in the present invention. (A) A thermoplastic resin is calendered to form a sheet.
Then, these are punched into a predetermined size to prepare a sheet for press molding.
For example, if one or two layers of the (A) thermoplastic resin sheet used in the present invention are laminated on the front and back of these substrate layers, and the sheets made of the resin composition for laser marking of the present invention are laminated and press-molded. good.
Alternatively, one or two layers of a sheet made of the resin composition for laser marking of the present invention, and a sheet made of (A) the thermoplastic resin used in the present invention are laminated on the front and back of these base layers and press-molded. do it.

In the case of press molding, for example, in order to integrate the sheet for laser marking of the present invention and a sheet made of a thermoplastic resin, a sheet for laser marking is attached to the front and back or one side of one or a plurality of stacked sheets as a base material. sandwiched between chromium-plated steel sheets (mold), then pressurized for a certain period of time at a press surface pressure of 0.01 to 10 MPa in the temperature range from the softening point of the thermoplastic resin to the softening point +50 ° C to heat bond. is preferred. If the molding temperature during such integration exceeds the softening point +50°C or if the integration is performed under a pressure exceeding 5 MPa, the entire sheet may be crushed, which is not preferable. In addition, if the molding temperature during such integration is less than the softening point temperature or the molding pressure (surface pressure) is less than 0.1 MPa, the thermoplastic resin sheet (or laser marking sheet) and the laser The adhesiveness of the marking sheet (or thermoplastic resin sheet) is reduced, resulting in adhesion between the molded thermoplastic resin sheet (or laser marking sheet) and the laser marking sheet (or thermoplastic resin sheet). This is not preferable because it lowers the performance.

In the case of press molding, an adhesive may be used as necessary, and a hot-melt adhesive is preferable as the adhesive.
Examples of hot-melt adhesives include ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methacrylic acid copolymer, Ethylene-maleic anhydride copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer, ethylene-glycidyl methacrylate-methyl acrylate copolymer , ethylene-methacrylic acid-maleic anhydride copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer, maleic anhydride-grafted polypropylene, maleic anhydride-grafted ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, etc. Polyolefin hot melt adhesive, urethane adhesive, synthetic rubber hot melt adhesive, polyester hot melt adhesive. Polyamide-based hot-melt adhesives, olefin-based thermoplastic elastomer resins, styrene-based thermoplastic elastomer resins, urethane-based thermoplastic elastomer resins, ester-based thermoplastic elastomer resins, amide-based thermoplastic elastomer resins, and the like can be used.
These hot-melt adhesives are usually used in a basis weight of about 0.1 to 100 g/m2.

Furthermore, in the present invention, the laser marking sheet can also be formed into a sheet by melt extrusion.
In the present invention, in order to obtain a laser marking sheet, for example, a three-layer multi-layer laser marking sheet, it is desirable to laminate by a co-extrusion method in which the resin compositions of each layer are melt co-extruded and laminated.
Specifically, the resin composition of each layer is blended, or if necessary, pelletized, and put into each hopper of a multi-layer T-die extruder with two or more layers covalently connected to the T-die, and the temperature is 150. C. to 300.degree. C., co-extruded with a multi-layer T-die, and solidified by cooling with a cooling roll or the like to form a multi-layer laminate. The multilayer laser marking sheet obtained by melt co-extrusion molding of the present invention can be formed by a known method without being limited to the method described above.

In addition, the laser marking sheet of the present invention is a multilayer (for example, (A) thermoplastic resin sheet / laser marking resin composition sheet / (A) thermoplastic resin sheet or laser marking resin composition sheet / ( In the case of A) thermoplastic resin sheet/laser marking resin composition sheet), (A) the thermoplastic resin used for the laser marking resin composition sheet and (A) used for the laser marking resin composition of the present invention ) The thermoplastic resins may be the same or different.

By scanning the obtained sheet for laser marking with a continuous or discontinuous laser beam, characters, numbers, patterns, bar codes, point codes, symbols, pictures, etc. can be easily attached to the sheet. Lasers used for marking are not limited, and lasers used include gas lasers such as carbon dioxide lasers, excimer lasers and argon lasers, and solid lasers such as ruby lasers, semiconductor lasers and YAG lasers. One preferred laser used is a Nd:YAG laser operating at a wavelength of 1064 nm.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.
Various evaluations in the examples were carried out as follows.
<Whiteness of white card>
The L value of the card surface (value measured using a Konica Minolta dye meter CM-5) was measured and evaluated.
○: L value is 88 or more △: L value is 87 or more and less than 88 ×: L value is less than 87 <chromogenic color>
observed visually.
○: Good (black color development)
×: Poor (colored brown and gray)
<Foaming after color development>
observed visually.
○: Good (the film is not blistered)
×: Defective (the film is swollen)

Reference Example (Preparation of vinyl chloride resin composition)
Vinyl chloride resin compositions used in Examples and Comparative Examples of the present invention were prepared.
The formulation is shown in Table 1.

Example 1
<Production of base sheet>
10 parts by weight of titanium oxide was blended with 100 parts by weight of the vinyl chloride resin composition (corresponding to component (A) of the present invention) prepared in Reference Example 1, and the mixture was processed at a processing temperature of 180°C using a calendering device. Calendering was performed to obtain a base sheet having a thickness of 0.28 mm. This was further cut into a length of 32 cm and a width of 48 cm to obtain a base sheet (hereinafter abbreviated as "core sheet").
<Production of front and back sheets>
Next, for 100 parts by weight of the vinyl chloride resin composition prepared in Reference Example 1, 0.002 parts by weight of carbon black (manufactured by Mitsubishi Chemical Holdings Corporation, #10, primary particle size = 75 nm), antimony-doped tin oxide 0.5 parts by weight of coated mica [Iriotec 8825, manufactured by Merck & Co., antimony-doped tin oxide/mica (weight ratio) = 46/54] was blended, and the resin composition for laser marking of the present invention was prepared in the same manner as above. was prepared and calendered in the same manner as in Reference Example 1 to prepare a laser marking sheet having a thickness of 0.1 mm. This was further cut into a length of 32 cm and a width of 48 cm to prepare a front and back layer sheet (hereinafter abbreviated as "OS sheet").

<Preparation of multi-layer laser marking sheet>
Next, a multilayer laser marking sheet of the present invention was produced by hot press molding.
That is, first, the cushion paper, the SUS plate, the OS sheet, two core sheets, the OS sheet, the SUS plate, and the cushion paper are placed in this order on the lower mold of the heat press, and then the upper mold of the heat press is placed. A multilayer laser marking sheet (card) of the present invention was obtained by hot press molding under press conditions of a temperature of 145° C., a surface pressure of 1.5 MPa, and a holding time of 10 minutes.
<Laser printing>
Next, on the multilayer laser marking sheet (card) obtained as described above, a bar code was printed in a conventional manner under the following laser printing conditions.
Laser printer:
Keyence Corporation (hybrid laser marker), YVO4 laser, wavelength 1.064 nm
printing conditions;
Frequency 5-30 kHz, output 20-32%, scan speed 1,250 mm/s, variable spot (focus) -20, number of prints 1 <evaluation>
Table 2 shows the results of laser marking.

Example 2
In the preparation of the laser marking resin composition of Example 1, 0.015 parts by weight of carbon black and 0.2 parts by weight of antimony-doped tin oxide-coated mica were mixed with 100 parts by weight of the vinyl chloride resin composition. A laser marking resin composition was prepared in the same manner as in Example 1, a multilayer laser marking sheet was obtained in the same manner, and laser marking was performed for evaluation.
Table 2 shows the results of laser marking.

Example 3
In the preparation of the laser marking resin composition of Example 1, 0.035 parts by weight of carbon black and 0.8 parts by weight of antimony-doped tin oxide-coated mica were mixed with 100 parts by weight of the vinyl chloride resin composition. A laser marking resin composition was prepared in the same manner as in Example 1, a multilayer laser marking sheet was obtained in the same manner, and laser marking was performed for evaluation.
Table 2 shows the results of laser marking.

Example 4
In the preparation of the resin composition for laser marking of Example 1, the type of carbon black was changed (#40, manufactured by Mitsubishi Chemical Holdings Corporation, primary particle diameter = 24 nm) with respect to 100 parts by weight of the vinyl chloride resin composition. , 0.002 parts by weight, and 0.5 parts by weight of antimony-doped tin oxide-coated mica were blended to prepare a laser marking resin composition in the same manner as in Example 1, and a multilayer laser marking sheet was prepared in the same manner. It was obtained and evaluated by performing laser marking printing.
Table 2 shows the results of laser marking.

Comparative example 1
In the preparation of the laser marking resin composition of Example 1, the procedure of Example 1 was repeated except that antimony-doped tin oxide (NYACOL SN903SD, manufactured by Nyacol Nano Technologies) was used instead of antimony-doped tin oxide-coated mica. A resin composition for laser marking was produced in the same manner, a sheet for multilayer laser marking was obtained in the same manner, and laser marking was performed for evaluation.
Table 3 shows the laser marking results.
In the case of Comparative Example 1, foaming was observed especially after color development because mica as component (D) was not used.

Comparative example 2
In the preparation of the laser marking resin composition of Example 1, bismuth trioxide + neodymium trioxide (manufactured by Tokan Material Technology Co., Ltd., 42-920A) was used without using antimony-doped tin oxide-coated mica. A resin composition for laser marking was prepared in the same manner as in Example 1, a multi-layer laser marking sheet was obtained in the same manner, and laser marking was performed for evaluation.
Table 3 shows the laser marking results.
In the case of Comparative Example 2, neither composite metal oxide as component (C) nor mica as component (D) was used, so neither evaluation was favorable.

Comparative example 3
In the preparation of the laser marking resin composition of Example 1, laser marking was carried out in the same manner as in Example 1, except that the antimony-doped tin oxide-coated mica was not used and an iminium dye (CIR-RL, manufactured by Nippon Carlit Co., Ltd.) was used. A marking resin composition was prepared, a multilayer laser marking sheet was obtained in the same manner, and laser marking was performed for evaluation.
Table 3 shows the laser marking results.
In the case of Comparative Example 3, neither composite metal oxide as component (C) nor mica as component (D) was used, so neither evaluation was favorable.

Comparative example 4
In the preparation of the laser marking resin composition of Example 1, a laser marking resin composition was prepared in the same manner as in Example 1, except that only carbon black (manufactured by Mitsubishi Chemical Holdings Corporation, #10) was used. A multi-layer laser marking sheet was obtained and laser marking was performed for evaluation.
Table 3 shows the laser marking results.
In the case of Comparative Example 4, neither composite metal oxide as component (C) nor mica as component (D) was used, so neither evaluation was favorable.

Comparative example 5
In the preparation of the laser marking resin composition of Example 1, a resin composition for laser marking was prepared in the same manner as in Example 1, except that a large amount of carbon black (manufactured by Mitsubishi Chemical Holdings Corporation, #10) was used. A multi-layer laser marking sheet was obtained in the same manner, and laser marking was performed for evaluation.
Table 3 shows the laser marking results.
In the case of Comparative Example 5, the amount of component (B) was too large, and the evaluation of whiteness and foaming after color development was poor.

Comparative example 6
In the preparation of the resin composition for laser marking of Example 1, a resin composition for laser marking was prepared in the same manner as in Example 1, except that the amount of components (C) to (D) was increased. A multi-layer laser marking sheet was obtained by the above method, and laser marking was performed for evaluation.
Table 3 shows the laser marking results.
In Comparative Example 5, there were too many components (C) to (D), and the evaluation of whiteness and color-developing hue was poor.

The sheet for laser marking of the present invention is used, for example, in automotive parts, bottle and bottle caps, tubes, pipes, containers, covers, keyboards, labels, chips, security documents (for example, identity cards or credit cards), office supplies, Equally good results are obtained with household items, school items, military items, toys, and many more items that will be clearly recognized by those skilled in the art. Laser marking can be used to identify, personalize, decorate, follow up, or protect such items. This marking may include, for example, information about the article itself, its contents, price, dimensions, purpose, date of manufacture or durability, holder, owner, manufacturer, distributor or place of origin. can.

Claims (9)

(A) Per 100 parts by weight of the thermoplastic resin, (B) 0.001 to 0.05 parts by weight of a laser light energy absorber that is carbon black and/or titanium black, (C) antimony-doped tin oxide (ATO) and / or 0.05 to 1.5 parts by weight of a composite metal oxide that is tin-doped indium oxide (ITO), and (D) 0.05 to 1.5 parts by weight of a silicate mineral for laser marking Resin composition. (A) The thermoplastic resin is polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, AS resin, ABS resin, polycarbonate, polyamide, polyester, polylactic acid resin, cellulose resin, vinyl chloride resin, polyoxymethylene , polyether sulfone, polyether ether ketone, and acrylic resin. 3. The resin composition for laser marking according to claim 1, wherein (B) the laser light energy absorbing agent is carbon black. 4. The resin composition for laser marking according to any one of claims 1 to 3 , wherein (D) the silicate mineral is mica. A laser marking sheet obtained by calendaring or melt extruding the resin composition for laser marking according to any one of claims 1 to 4 . A multi-layer laser marking sheet obtained by laminating (A) a thermoplastic resin sheet according to claim 1 on at least one surface of the laser marking sheet according to claim 5 . A multi-layer laser marking sheet obtained by laminating the laser marking sheet according to claim 5 on at least one surface of (A) a thermoplastic resin sheet according to claim 1. The thermoplastic resin (A) according to claim 1 and the resin composition for laser marking according to any one of claims 1 to 4 are melt-coextruded, for multilayer laser marking according to claim 6 or 7 . Sheet manufacturing method. Claim 6 , characterized in that the sheet made of the thermoplastic resin (A) according to claim 1 and the sheet made of the resin composition for laser marking according to any one of claims 1 to 4 are press-molded. 8. The method for producing a multilayer laser marking sheet according to 7 above.