JP7160861B2 - COATING COMPOSITION FOR LASER ETCHING, METHOD FOR MANUFACTURING MAIN INGREDIENT THEREOF, MOLDED BODY AND METHOD FOR FORMING THE SAME - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a coating composition for laser etching, a method for producing a main agent thereof, a molded article, and a method for forming the same.

2. Description of the Related Art In switch parts provided in automobile interiors, etc., laser etching is applied to a film formed on a base material for the purpose of providing operability or visibility at night. Laser etching is, for example, a technique employed in manufacturing processes of semiconductor devices, ceramic substrates, circuit boards, etc. (see, for example, Patent Document 1). In addition, by irradiating a laser beam to a molded product coated with a thermoplastic resin composition for laser marking, which consists of a thermoplastic resin and an organic fiber, the contrast and hue between the laser-irradiated part and the substrate of the adjacent molded product can be improved. A technology has been disclosed in which a molded product having a laser-marked surface is obtained by the difference in the thickness (see, for example, Patent Document 2). Since the switch part is often touched by the driver, it is generally preferable to have a light-transmitting layer having light-transmitting properties as a coating and a protective layer for protecting the light-transmitting layer. Briefly, a transparent base material such as a polycarbonate material or an acrylic material is formed with a light-transmitting layer having light-transmitting properties, and a protective layer is formed thereon. After that, a specific portion is irradiated with a laser beam to peel off only the protective layer. The light-transmitting layer is exposed at the peeled portion, and when light is applied from the rear surface of the transparent base material, characters or shapes can be visually recognized through the light-transmitting layer. As a coating material, a two-liquid reaction type urethane coating is generally used because of requirements such as designability and durability, and the need for interlayer adhesion due to the multi-layered structure.

JP 2011-45890 A JP-A-2008-13599

Peeling of the protective layer means (1) irradiating a specific portion of the coating with a laser beam, (2) the energy absorbing material in the protective layer absorbs the energy of the laser beam, and (3) the surface temperature of the protective layer rises rapidly. , (4) partial burning of the protective layer, and (5) partial burning of the protective layer. The wavelength of the laser light is near-infrared, and the protective layer contains an energy absorbing material that absorbs this light. However, depending on the required performance or design, the compounding material of the protective layer may not be able to sufficiently absorb near-infrared rays, which may affect the required quality in etching. In this case, the protective layer may remain unburned, the light-transmitting layer may stain, or a distorted outline may be formed, resulting in quality problems. Countermeasures include changing the laser output or pattern conditions, or changing the coating film thickness, but in industrial production lines, from the viewpoint of production efficiency, it is not desirable to extend the time or set detailed individual conditions. .

An object of the present disclosure is to provide a coating composition for laser etching that has good laser etching properties and excellent productivity, a method for producing the main agent thereof, a molded article, and a method for forming the same.

A coating composition for laser etching according to the present invention is a two-component coating composition for laser etching containing a main agent containing an acrylic polyol and a curing agent containing a polyisocyanate, wherein the main agent or the curing agent contains a laser absorber, and the acrylic polyol contains a branched alkyl group-containing monomer unit having a branched alkyl group in a side chain as a constituent monomer unit, and the branched relative to the mass of the acrylic polyol The content of the alkyl group-containing monomer unit is 13 to 57% by mass, the hydroxyl value of the acrylic polyol is 28 to 62 mgKOH/g, the glass transition point of the acrylic polyol is 45 to 82 ° C. , The branched alkyl group-containing monomer unit is either or both of a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group, or a monomer unit derived from a monomer having 3 methyl groups in the branched alkyl group. and the branched alkyl group has 3 to 10 carbon atoms .

In the laser etching coating composition according to the present invention, the branched alkyl group-containing monomer unit includes a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group and a monomer having 3 methyl groups in the branched alkyl group. The content ratio of the monomer unit derived from the monomer having 2 methyl groups in the branched alkyl group is the content of the monomer units derived from the monomer having 3 methyl groups in the branched alkyl group. Includes more than proportion forms.

In the laser etching coating composition according to the present invention, the branched alkyl group-containing monomer unit includes a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group and a monomer having 3 methyl groups in the branched alkyl group. The content ratio of the monomer unit derived from the monomer having 3 methyl groups in the branched alkyl group is the content of the monomer units derived from the monomer having 2 methyl groups in the branched alkyl group. Includes more than proportion forms. In the coating composition for laser etching according to the present invention, the monomer having two methyl groups in the branched alkyl group includes isopropyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and The monomer that is at least one of isodecyl (meth)acrylate and has 3 methyl groups in the branched alkyl group is preferably tert-butyl (meth)acrylate.

A method for producing a main component of a coating composition for laser etching according to the present invention is a two-component laser etching coating composition containing a main component containing an acrylic polyol and a curing agent containing a polyisocyanate. In the production method of , the acrylic polyol is prepared by using a mixed solution containing a reaction solvent, a reaction initiator, and at least a monomer having a hydroxyl group and a monomer having a branched alkyl group as monomers constituting the acrylic polyol. a step of copolymerizing constituent monomers to obtain an acrylic polyol solution, wherein the proportion of the monomer having a branched alkyl group is 13 to 57% by mass with respect to the total weight of the monomers constituting the acrylic polyol; has a hydroxyl value of 28 to 62 mgKOH/g, the acrylic polyol has a glass transition point of 45 to 82° C., and the monomer having a branched alkyl group has 2 methyl groups in the branched alkyl group. One or both of a monomer and a monomer having 3 methyl groups in the branched alkyl group, wherein the branched alkyl group has 3 to 10 carbon atoms .

It is preferable that the method for producing the main component of the coating composition for laser etching according to the present invention further includes the step of blending a laser absorber into the acrylic polyol solution.

The molded article according to the present invention is a molded article having a substrate and a coating provided on the surface of the substrate, wherein the coating has a protective layer, and the protective layer is the laser etching according to the present invention. It is a cured film of a coating composition for industrial applications and has laser-etched holes.

In the molded article according to the present invention, the base material has transparency, and the film contains either or both of a light scattering agent and a colorant between the base material and the protective layer. It is preferred to have further layers.

The method for forming a molded article according to the present invention comprises applying the coating composition for laser etching according to the present invention onto the surface of a substrate or onto the surface of a light-transmitting layer provided on the surface of a substrate to form a protective layer. and forming a laser-etching hole by laser-etching the protective layer.

ADVANTAGE OF THE INVENTION According to this indication, the coating composition for laser etching which has favorable laser etching property and was excellent in productivity, the manufacturing method of the main ingredient, the molded object, and its forming method can be provided.

1 is a schematic cross-sectional view showing an example of a molded body according to a first embodiment; FIG. FIG. 4 is a schematic cross-sectional view showing an example of a molded body according to a second embodiment; This is a sample for evaluating the laser etching properties of Example 9. It is a sample for evaluating the laser etching properties of Comparative Example 8.

One aspect of the present invention will now be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In addition, in this specification and the drawings, constituent elements having the same reference numerals are the same as each other. Various modifications may be made as long as the effects of the present invention are achieved.

The laser etching coating composition according to the present embodiment is a two-component laser etching coating composition containing a main agent containing an acrylic polyol and a curing agent containing a polyisocyanate. Either one or both contain a laser absorber, the acrylic polyol contains a branched alkyl group-containing monomer unit having a branched alkyl group in the side chain as a constituent monomer unit, and the branched alkyl group-containing monomer relative to the mass of the acrylic polyol The unit content is 13 to 57% by mass, the acrylic polyol has a hydroxyl value of 28 to 62 mgKOH/g, and a glass transition point of 45 to 82°C.

A coating composition for laser etching is a coating composition whose cured product can be laser-etched. Here, the laser etching is a phenomenon of evaporating and removing the resin of a predetermined portion by irradiating the predetermined portion with a laser.

The main agent contains acrylic polyol. Acrylic polyol is an acrylic resin having two or more hydroxyl groups in one molecule.

In this embodiment, the acrylic polyol includes branched alkyl group-containing monomer units having branched alkyl groups. As used herein, a monomer unit refers to a structural unit derived from the monomer. For example, a branched alkyl group-containing monomer unit is a structural unit derived from a branched alkyl group-containing monomer. In the branched alkyl group-containing monomer, the branched alkyl group preferably has 3 to 10 carbon atoms, more preferably 4 to 8 carbon atoms. The branched alkyl group-containing monomer has two methyl groups in the branched alkyl group, such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate or isodecyl (meth)acrylate. A branched alkyl group-containing monomer or a branched alkyl group-containing monomer having three methyl groups in the branched alkyl group such as tert-butyl (meth)acrylate. Among these, the branched alkyl group-containing monomer is more preferably isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate or 2-ethylhexyl acrylate. The number of methyl groups can be confirmed, for example, by analyzing the coating composition by NMR (Nuclear Magnetic Resonance) method or GC/MS method (Gas Chromatography-Mass Spectrometry). Moreover, in this specification, (meth)acrylic acid means acrylic acid and methacrylic acid. Branched alkyl group-containing monomers may be used alone or in combination of two or more.

In the laser etching coating composition according to the present embodiment, the branched alkyl group-containing monomer unit is a monomer unit derived from a monomer having two methyl groups in the branched alkyl group or a monomer having three methyl groups in the branched alkyl group. Includes forms that are either or both of the derived monomeric units. In the present embodiment, the branched alkyl group-containing monomer unit is only a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group, or a monomer unit derived from a monomer having 3 methyl groups in the branched alkyl group. and a form in which both a monomer unit derived from a monomer having two methyl groups in the branched alkyl group and a monomer unit derived from a monomer having three methyl groups in the branched alkyl group are included.

In the laser etching coating composition according to the present embodiment, the branched alkyl group-containing monomer unit is a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group and 3 methyl groups in the branched alkyl group. The content ratio of monomer units derived from a monomer having 2 methyl groups in the branched alkyl group and the content ratio of the monomer units having 3 methyl groups in the branched alkyl group are both monomer-derived monomer units. includes more forms than

Further, in the laser etching coating composition according to the present embodiment, the branched alkyl group-containing monomer unit is a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group and a monomer unit having 3 methyl groups in the branched alkyl group. The content ratio of monomer units derived from a monomer having 3 methyl groups in the branched alkyl group is the content of monomer units derived from a monomer having 2 methyl groups in the branched alkyl group. Includes more than proportion forms.

The acrylic polyol contains a hydroxyl group-containing monomer unit having a hydroxyl group in addition to the branched alkyl group-containing monomer unit. Hydroxyl group-containing monomers include, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, and other monomers having hydroxyl groups; A ring-opening adduct of γ-butyrolactone to 2-hydroxyethyl methacrylate and a ring-opening adduct of ε-caprolactone to 2-hydroxyethyl acrylate. Any one of the hydroxyl group-containing acrylic monomers can be used alone, or two or more of them can be used in appropriate combination.

Moreover, in this embodiment, the acrylic polyol may contain other ethylenically unsaturated monomer units in addition to the branched alkyl group-containing monomer units and the hydroxyl group-containing monomer units. Other ethylenically unsaturated monomers are, for example, acrylic acid esters, methacrylic acid esters, styrene or derivatives thereof, vinyl esters, halogenated vinyl monomers or nitrogen-containing vinyl monomers. Other ethylenically unsaturated monomers may be used alone or in combination of two or more.

The content ratio of the branched alkyl group-containing monomer units to the weight of the acrylic polyol (hereinafter sometimes referred to as branched alkyl concentration) is 13 to 57% by weight, more preferably 15 to 55% by weight. If the branched alkyl concentration is less than 13% by mass, the laser etchability is poor. If the branched alkyl concentration exceeds 57% by mass, the oil resistance is poor. The branched alkyl concentration is the ratio of the mass of the branched alkyl group-containing monomer to the total mass of the monomers constituting the acrylic polyol. The branched alkyl concentration is preferably calculated, for example, from the blending ratio of the main agent of the coating composition.

The acrylic polyol has a hydroxyl value (OHV) of 28 to 62 mgKOH/g, more preferably 30 to 60 mgKOH/g. If the hydroxyl value of the acrylic polyol is less than 28 mgKOH/g, the crosslink density of the urethane bonds with the polyisocyanate is insufficient, resulting in poor cosmetic resistance and oil resistance. When the hydroxyl value of the acrylic polyol exceeds 62 mgKOH/g, the cross-linking density of the urethane bonds with the polyisocyanate becomes excessive, resulting in poor wet adhesion resistance and heat cycle adhesion resistance.

The acrylic polyol has a glass transition point (Tg) of 45 to 82°C, more preferably 50 to 80°C. If the acrylic polyol has a glass transition point of less than 45°C, the cosmetic resistance is poor. If the glass transition point of the acrylic polyol exceeds 82°C, the cosmetic resistance is poor.

The curing agent contains polyisocyanate. A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. diisocyanate, methylcyclohexyl diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, n-pentane-1,4-diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate. Any one of these can be used alone, or two or more thereof can be used in appropriate combination.

The mixing ratio of the main agent and the curing agent is preferably such that the isocyanate group of the polyisocyanate compound is 0.5 to 3.0 molar equivalents, preferably 0.5 to 2.0, with respect to the hydroxyl group of the acrylic polyol. Molar equivalents are more preferred. If the amount is less than 0.5 molar equivalents, the cosmetic resistance and oil resistance may be poor. If the amount exceeds 3.0 molar equivalents, excessive cure shrinkage may result in poor wet adhesion resistance and heat cycle adhesion resistance.

At least one of the main agent and the curing agent contains a laser absorber. A laser absorber is a substance that generates heat by absorbing laser light. Although the type thereof is not particularly limited, it is, for example, a colored coloring agent such as an inorganic pigment or an organic pigment, or an extender pigment. The colored coloring agent is not particularly limited, and is, for example, a black coloring pigment such as carbon. A laser absorber may be used individually by 1 type, or may use 2 or more types together. This embodiment includes a form in which the laser absorbing agent is contained only in the main agent, a form in which it is contained only in the curing agent, and a form in which it is contained in both the main agent and the curing agent. Among these, the laser absorber is preferably contained only in the main agent. Further, a nuance may be imparted to black by using a black colorant as a laser absorber and further adding a blue colorant. However, in this case, there is a problem that the blue dye tends to transfer to the substrate during the laser etching process. However, since the cured film of the coating composition for laser etching according to the present embodiment has good laser etching properties, even when a blue dye is used, color transfer of the blue dye to the substrate can be suppressed. can.

In addition, the main agent or curing agent includes a solvent such as a reaction solvent or a diluting solvent, a thickener, a matting agent, a slip agent, a pigment, an inorganic filler, a glitter material, a plasticizer, a dispersant, as long as the effect of the present invention is not impaired. , an emulsifier, a flow control agent, an ultraviolet absorber, or a light stabilizer.

Next, a method for producing the base material of the coating composition for laser etching according to this embodiment will be described. A method for producing a main component of a coating composition for laser etching according to the present embodiment is a main component of a two-component laser etching coating composition containing a main component containing an acrylic polyol and a curing agent containing a polyisocyanate. In the production method of , a mixed solution containing a reaction solvent, a reaction initiator, and at least a monomer having a hydroxyl group and a monomer having a branched alkyl group as monomers constituting the acrylic polyol is used to constitute the acrylic polyol. It includes a step of copolymerizing monomers to obtain an acrylic polyol solution, wherein the blending ratio of the monomer having a branched alkyl group is 13 to 57% by mass with respect to the total mass of the monomers constituting the acrylic polyol, and the hydroxyl value of the acrylic polyol is 28 to 62 mgKOH/g, and the glass transition point of the acrylic polyol is 45 to 82°C.

Examples of the reaction solvent include, but are not limited to, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate and n-butyl acetate, and hydrocarbon solvents such as toluene and xylene.

Examples of reaction initiators include peroxides such as t-butylperoxy-2-ethylhexanoate, azobisisobutyronitrile (AIBN), and azobisnitriles such as azobismethylvaleronitrile.

The step of obtaining the acrylic polyol solution can employ a known polymerization method, for example, a step of copolymerizing the monomers constituting the acrylic polyol by a dropping method of radical polymerization.

It is preferable that the method for producing the main component of the coating composition for laser etching according to the present embodiment further includes the step of blending the acrylic polyol solution with a laser absorber.

Next, a molded article provided with a cured film of the coating composition for laser etching according to this embodiment will be described. As shown in FIG. 1 or FIG. 2, the molded bodies 1 and 2 according to the present embodiment are molded bodies having a substrate 10 and a coating 20 provided on the surface of the substrate 10, and the coating 20 is protected. It has a layer 21 , and the protective layer 21 is a cured film of the coating composition for laser etching according to the present embodiment, and has laser etching holes 30 . The molded body according to this embodiment includes a molded body 1 (first embodiment) in which the protective layer 21 is directly provided on the surface of the substrate 10, and a light and a molded body 2 (second embodiment) provided on the surface of the transmission layer 22 .

First, a molded body 1 according to the first embodiment will be described with reference to FIG.

The material of the substrate 10 is, for example, polycarbonate resin, acrylic resin, polypropylene resin, ABS (Acrylonitrile Butadiene Styrene) resin, or AES (Acrylonitrile Ethylene-Propylene-Dien Styrene) resin. In the molded article according to the first embodiment, the substrate 10 may be transparent or opaque. In the present specification, having transparency includes colorless and transparent, colored and translucent, such as frosted glass. Among these, it is more preferable that the base material 10 is opaque, colored transparent, or translucent in terms of enhancing the visibility of the laser-etched holes 30 . In applications such as button parts used in automobile interiors where the back surface of the substrate is exposed to light, the substrate 10 preferably has transparency, and more preferably is colored transparent or translucent.

The protective layer 21 is a cured film of the coating composition for laser etching according to this embodiment, and is a layer to be laser etched. The cured film of the coating composition for laser etching is composed of an acrylic urethane resin formed by reaction and curing of acrylic polyol as a main agent and polyisocyanate as a curing agent.

The thickness of the protective layer 21 is preferably 5-40 μm, more preferably 10-30 μm. If the thickness is less than 10 μm, the durability of the coating may be poor. If it exceeds 30 μm, laser etching may take longer than usual.

A laser etching hole 30 is a portion where a part of the protective layer has disappeared due to laser etching. The laser-etched holes 30 constitute characters, symbols, designs, pictures, photographs, or the like.

Next, the molded body 2 according to the second embodiment will be described with reference to FIG. A molded body 2 according to the second embodiment has the same basic configuration as that of the molded body according to the first embodiment except that it has a light transmission layer 22 . Therefore, the description of the common configuration is omitted.

In the molded body 2 according to the second embodiment, the substrate 10 has transparency, and the film 20 contains either or both of a light scattering agent and a colorant between the substrate 10 and the protective layer 21. It is preferred to further have a light transmission layer 22 comprising.

In the molded body 2 according to the second embodiment, the base material 10 has transparency, so that the light transmission layer 22 can transmit light appropriately in applications where light is applied from the back side of the base material, such as button parts used in automobile interiors. As a result, the visibility of the laser-etched holes 30 can be enhanced.

The light transmission layer 22 is preferably a cured resin film. The type of resin is not particularly limited, and examples thereof include acrylic resin, acrylic urethane resin, and acrylic silicon resin. Among these, the acrylic urethane resin is preferable because it has good adhesion to the protective layer 21 .

Light scattering agents are, for example, titanium oxide, silica, talc or resin beads. By blending the light scattering agent, the light transmission layer 22 can be made into a frosted glass shape, and the visibility of the laser-etched holes 30 formed in the protective layer 21 can be further enhanced.

Colorants are, for example, inorganic or organic pigments. The coloring agent is preferably a coloring agent that has low laser absorption and is difficult to be laser etched or does not have laser absorption. The color of the coloring agent is not particularly limited, and is white, blue, red, yellow, green or black, for example. One colorant may be used alone, or two or more colorants may be used in combination. By adding a coloring agent, the light transmission layer 22 can be colored and transparent, and the visibility of the laser-etched holes 30 formed in the protective layer 21 can be further enhanced.

Although the thickness of the light transmission layer 22 is not particularly limited, it is preferably 5 to 40 μm, more preferably 110 to 30 μm.

The method for forming the molded bodies 1 and 2 according to the present embodiment includes coating the surface of the substrate 10 or the surface of the light transmission layer 22 provided on the surface of the substrate 10 with the laser etching paint according to the present embodiment. It has a step of applying a composition to form the protective layer 21 and a step of laser etching the protective layer 21 to form the laser etching holes 30 .

In the step of forming the protective layer 21, a main agent and a curing agent are mixed in a predetermined ratio, and a laser etching coating composition adjusted to an appropriate solid content concentration with a diluent solvent as necessary is applied on the surface of the base material. Alternatively, it is coated on the surface of the light transmission layer and dried to form a cured film. A known coating method can be used as the coating method, and examples thereof include a roll coating method, a spray method, a dipping method, and a brush coating method. The diluent solvent is not particularly limited, and examples thereof include the solvents listed as reaction solvents.

When forming the light-transmitting layer 22 , the coating composition for forming the light-transmitting layer is applied onto the surface of the substrate 10 . As the coating method, the known methods listed in the coating method of the protective layer 21 can be employed. The coating composition for forming a light transmission layer may be a one-part system or a two-part system. Among these, the two-liquid system is preferable. In the present embodiment, the coating composition for forming a light transmission layer is a two-component coating composition having a main agent containing an acrylic polyol and a curing agent containing a polyisocyanate, either the main agent or the curing agent, or Both are preferably coating compositions containing either or both of a light scattering agent or a colorant that has low laser absorption and is difficult to laser etch or does not have laser absorption. Here, the type of acrylic polyol is not particularly limited, but the acrylic polyol used in the laser etching coating composition according to the present embodiment is preferable. Thereby, the adhesion between the light transmission layer 21 and the protective layer 22 can be further enhanced, and the durability of the coating can be further enhanced.

The type of laser used for laser etching is not particularly limited, and is, for example, a near-infrared laser such as a YAG laser.

The molded bodies 1 and 2 according to the present embodiment can be applied to many industrial products such as automobile parts such as button parts, daily goods, home electric appliances, OA equipment such as computer keyboards, and building materials.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

(Preparation of acrylic polyol solution)
150 g of n-butyl acetate was placed in a 500 ml four-necked flask equipped with a stirrer, cooler, nitrogen enclosure, thermometer and monomer dropping device, and heated until the internal temperature reached 90°C. Next, a mixed solution of a monomer and a reaction initiator shown in Tables 1 and 2 was added dropwise over 120 minutes, and the reaction was completed by holding at 90°C for 4 hours to obtain an acrylic polyol solution. In Tables 1 and 2, materials are indicated by abbreviations. Abbreviations are explained below.
MMA: Methyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
St: Styrene (manufactured by Sankyo Chemical Co., Ltd.)
n-BMA: n-butyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
i-BMA: isobutyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
t-BMA: Tertiary butyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
BA: normal butyl acrylate (manufactured by Mitsubishi Chemical Corporation)
HEA: Hydroxyethyl acrylate (manufactured by Mitsubishi Chemical Corporation)
MAA: Methacrylic acid (manufactured by Mitsubishi Chemical Corporation)
DEMA: Diethylaminoethyl methacrylate (manufactured by Mitsubishi Chemical Corporation)
ABN-E: Azobismethylbutyronitrile (manufactured by Japan Finechem Co., Ltd.)
n-BAC: n-butyl acetate (manufactured by Sankyo Chemical Co., Ltd.)

(Preparation of main ingredient of coating composition for forming light transmission layer)
80 g of the obtained acrylic polyol solution of each example and each comparative example, 5 g of R-930 (manufactured by Ishihara Sangyo Co., Ltd., titanium oxide), and 12 g of ethyl acetate were dispersed for 3 hours with a paint shaker, PFA-131 (Kusumoto Kasei 3 g of amide thickener manufactured by Co., Ltd. was added, and the mixture was dispersed for an additional 15 minutes to obtain a main ingredient of a coating composition for forming a light-transmitting layer.

(Preparation of main agent of coating composition for laser etching (coating composition for forming protective layer))
80 g of the obtained acrylic polyol solution of each example and each comparative example, 3 g of MA100 (manufactured by Mitsubishi Chemical Corporation, carbon) as a coloring pigment, and 14 g of ethyl acetate were dispersed with a paint shaker for 8 hours, PFA-131 (Kusumoto Kasei 3 g of amide thickener) was added and dispersed for another 15 minutes to obtain a black dispersion. 80 g of black dispersion liquid, 1 g of NX-053 blue (manufactured by Dainichiseika Kogyo Co., Ltd., pigment paste, PB-15:4, pigment concentration 19%), and 4 g of ACEMATT OK 607 (manufactured by EVONIK, organically modified silica) as a matting agent Then, 10 g of Microflat PB-18BA (manufactured by Koyo Chemical Co., Ltd., 10% polyethylene dispersion) as a slip agent and 6 g of ethyl acetate were dispersed and stirred to prepare a coating composition for laser etching (a coating composition for forming a protective layer). A main ingredient was obtained.

(Formation of compact)
Sumidur N3300 (Hexamethylene diisocyanate, manufactured by Sumika Covestrourethane Co., Ltd.) was added as a curing agent to the main component of the resulting coating composition for forming a light transmission layer in an equivalent amount (NCO/OH=1.0), and the viscosity was further adjusted. For this purpose, n-butyl acetate was added to adjust the solid content to 20% to obtain a coating composition for forming a light transmission layer. The resulting coating composition for forming a light-transmitting layer was applied onto a transparent polycarbonate substrate (manufactured by SABIC, length 10 mm, width 10 mm, thickness 2 mm) so as to give a dry film thickness of 20 µm. It was dried for 40 minutes to form a light transmission layer. Then, Sumidur N3300 (hexamethylene diisocyanate, manufactured by Sumika Covestro Urethane Co., Ltd.) was added as a curing agent to the main component of the obtained coating composition for forming a protective layer on the surface of the light-transmitting layer in an equivalent amount (NCO/OH = 1.0), and n-butyl acetate was added to adjust the viscosity to adjust the solid content to 20% to obtain a coating composition for forming a protective layer (a coating composition for laser etching). The obtained coating composition for forming a protective layer was applied so as to have a dry film thickness of 20 μm and dried at 80° C. for 40 minutes to form a protective layer. Then, the protective layer was irradiated with a YAG laser to form laser-etched holes to obtain a compact. After curing the obtained compact at room temperature for 72 hours, the following tests were carried out. Evaluation results are shown in Tables 1 and 2.

(Initial adhesion)
According to JIS K5600-5-6:1999 "cross-cut method", 100 grid-like incisions of 1 mm x 1 mm were made on the surface of the film, and a peel test was performed using an adhesive tape. Evaluation criteria are as follows.
○: No peeling (practical level)
×: Peeling of 1 square or more out of 100 squares (practically unsuitable level)

(wet adhesion resistance)
Adhesion was evaluated after 200 hours in an atmosphere of 50° C. and 90% RH. The evaluation method and evaluation criteria are the same as those for initial adhesion.

(Heat cycle adhesion)
Adhesion was evaluated after 10 cycles of 90°C and -30°C for 5 hours each. The evaluation method and evaluation criteria are the same as those for initial adhesion.

(cosmetics resistance)
A sunscreen (NEUTROGENA, Ultra Sheer Dry-touch SPF10) was applied to the surface of the film at 0.2 g per 100 cm ² , and after 4 hours at 50°C, the sunscreen was washed off and the surface of the film was cleaned. It was evaluated visually. Evaluation criteria are as follows.
○: No trace (practical level)
△: There is a slight residue, but there is no practical problem (practical lower limit level)
×: Significant residue, practically problematic (practical unsuitable level)

(Oil resistance)
5 ml of volatile oil (JXTG Energy Co., Ltd., ligroin) was dropped onto the surface of the film, and after 2 hours in a room temperature atmosphere, the volatile oil was wiped off, and the appearance of the surface of the film was visually evaluated. Evaluation criteria are the same as for cosmetic resistance.

(Laser etching property 1)
In forming the molded body, a laser etching hole having a square shape of 3 mm long and 3 mm wide was formed with a laser frequency of 100 kHz and a laser scanning speed of 400 mm/sec. Evaluation criteria are as follows.
○: The protective layer completely disappeared and the white transparent layer was exposed (practical level)
△: The protective layer was completely lost, but the blue pigment of the laser absorber slightly transferred to the transparent layer (practical lower limit level).
×: The protective layer remained unburned, the outline of the laser etching hole was distorted, and the blue dye often transferred to the transmission layer (unsuitable for practical use).

In all examples, it was confirmed that the coating film performance was at a practical level and could be applied to many industrial products. Also, the laser etching property was good. On the other hand, in Comparative Examples 1 and 2, since the hydroxyl value of the acrylic polyol was small, the cosmetic resistance and oil resistance were at a practically unsuitable level. In Comparative Examples 3 and 4, since the hydroxyl value of the acrylic polyol was large, the wet adhesion resistance and the heat cycle adhesion resistance were at a practically unsuitable level. In Comparative Examples 5 and 6, since the glass transition point of the acrylic polyol was low, the cosmetic resistance was at an unsuitable level for practical use. In Comparative Examples 7 and 8, the concentration of branched alkyl with respect to the mass of the acrylic polyol was low, so the laser etchability was at an unsuitable level for practical use. Comparative Example 9 had a high concentration of branched alkyl relative to the mass of the acrylic polyol, so the oil resistance was at an unsuitable level for practical use. In Comparative Example 10, the glass transition point of the acrylic polyol was too high and the reaction with the curing agent was poor, so the cosmetic resistance was at a practically unsuitable level.

(Laser etching property 2)
In forming the molded bodies of Example 9 and Comparative Example 8, the frequency of the laser for laser etching was changed from 20 to 200 kHz at intervals of 20 kHz, and the scanning speed of the laser was changed from 200 to 1100 mm/sec to 100 mm/sec. Square laser etching holes of 3 mm long and 3 mm wide were formed by changing the intervals of sec. FIG. 3 shows a sample of Example 9 evaluated for laser etching properties, and FIG. 4 shows a sample of Comparative Example 8 evaluated for laser etching properties. 3 and 4, the vertical axis indicates the value of the laser frequency Qf (unit: kHz), and the horizontal axis indicates the value of the laser scanning speed v (unit: mm/sec). The scanning speed v increases, and the frequency Qf increases toward the upper side. In FIGS. 3 and 4, the images of the samples evaluated for laser etchability were processed into gray gradation, but each sample can be represented more accurately by the color image before being processed into gray gradation. As shown in FIG. 3, in the sample of Example 9, the transmissive layer was exposed in almost all squares. In addition, there were many squares in which the exposed transmissive layer was white. In other words, there were few squares where the blue dye in the protective layer was color-transferred. On the other hand, as shown in FIG. 4, in the sample of Comparative Example 8, when the scanning speed was increased to 800 mm/sec or more, many squares where the protective layer did not disappear were observed. Moreover, even in the exposed transmissive layer, color transfer of the blue dye of the protective layer was observed in most of the squares. From the comparison of FIGS. 3 and 4, it was confirmed that the coating composition for laser etching according to the present embodiment has good laser etching properties and can perform laser etching with excellent productivity.

1, 2 molded body 10 substrate 20 coating 21 protective layer 22 light transmission layer 30 laser etching hole

Claims (9)

In a two-component laser etching coating composition containing a main agent containing an acrylic polyol and a curing agent containing a polyisocyanate,
Either one or both of the main agent and the curing agent contain a laser absorber,
The acrylic polyol contains a branched alkyl group-containing monomer unit having a branched alkyl group in a side chain as a constituting monomer unit, and the content of the branched alkyl group-containing monomer unit is 13 to 57% by mass with respect to the mass of the acrylic polyol. can be,
The acrylic polyol has a hydroxyl value of 28 to 62 mgKOH/g,
The acrylic polyol has a glass transition point of 45 to 82° C. ,
The branched alkyl group-containing monomer unit is either or both of a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group, or a monomer unit derived from a monomer having 3 methyl groups in the branched alkyl group. can be,
A coating composition for laser etching , wherein the branched alkyl group has 3 to 10 carbon atoms . The branched alkyl group-containing monomer unit is both a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group and a monomer unit derived from a monomer having 3 methyl groups in the branched alkyl group,
A content ratio of monomer units derived from a monomer having two methyl groups in the branched alkyl group is higher than a content ratio of monomer units derived from the monomer having three methyl groups in the branched alkyl group. Item 1. The coating composition for laser etching according to item 1. The branched alkyl group-containing monomer unit is both a monomer unit derived from a monomer having 2 methyl groups in the branched alkyl group and a monomer unit derived from a monomer having 3 methyl groups in the branched alkyl group,
A content ratio of monomer units derived from a monomer having 3 methyl groups in the branched alkyl group is higher than a content ratio of monomer units derived from a monomer having 2 methyl groups in the branched alkyl group. The coating composition for laser etching according to claim 1 . The monomer having two methyl groups in the branched alkyl group is at least one of isopropyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and isodecyl (meth)acrylate. and
4. The coating composition for laser etching according to claim 1, wherein the monomer having 3 methyl groups in the branched alkyl group is tert-butyl (meth)acrylate. In a method for producing a main agent of a two-component laser etching coating composition containing a main agent containing an acrylic polyol and a curing agent containing a polyisocyanate,
Using a mixed solution containing a reaction solvent, a reaction initiator, and at least a monomer having a hydroxyl group and a monomer having a branched alkyl group as the monomers constituting the acrylic polyol, the monomers constituting the acrylic polyol are mixed. comprising a step of polymerizing to obtain an acrylic polyol solution;
The blending ratio of the monomer having the branched alkyl group is 13 to 57% by mass with respect to the total mass of the monomers constituting the acrylic polyol,
The acrylic polyol has a hydroxyl value of 28 to 62 mgKOH/g,
The acrylic polyol has a glass transition point of 45 to 82° C. ,
the monomer having a branched alkyl group is either or both of a monomer having 2 methyl groups in the branched alkyl group or a monomer having 3 methyl groups in the branched alkyl group;
A method for producing a main component of a coating composition for laser etching , wherein the branched alkyl group has 3 to 10 carbon atoms . 6. The method for producing a main ingredient of a coating composition for laser etching according to claim 5, further comprising adding a laser absorber to the acrylic polyol solution. In a molded article having a base material and a coating provided on the surface of the base material,
The coating has a protective layer, the protective layer is a cured film of the coating composition for laser etching according to any one of claims 1 to 4, and has laser etching holes. molded body. The base material has transparency,
8. The molded article according to claim 7, wherein the coating further has a light transmission layer containing either one or both of a light scattering agent and a colorant between the substrate and the protective layer. A protective layer is formed by coating the coating composition for laser etching according to any one of claims 1 to 4 on the surface of the base material or on the surface of the light transmission layer provided on the surface of the base material. and
and forming a laser etching hole in the protective layer by laser etching.

Images