JP2024075403A - Laminates and laser labels - Google Patents

Abstract

[Problem] To provide a laminate and a laser label that are excellent in both character visibility and color transmittance of a light source. [Solution] A laminate in which a first resin layer made of a first resin composition containing a first binder resin, scale-like particles, and spherical particles containing a compound having a triazine ring, and a second resin layer made of a second resin composition containing a second binder resin are laminated in this order. [Selected Figure] None

Description

The present invention relates to a laminate and a laser label.

Laser labeling is a technique for printing characters, bar codes, symbols, etc. by etching the surface layer of a laminate consisting of two or more resin layers with laser irradiation to expose the underlying layer.
For example, Patent Document 1 discloses a laser label comprising a colored resin layer that can be removed by irradiation with laser light, a colored destruction layer laminated on the colored resin layer and having a visible color difference from the colored resin layer, and an adhesive layer laminated on the colored destruction layer.

JP 2007-021818 A

Laser labels are also used for applications such as attaching them to the surface of indicator lamps of industrial equipment, personal computers, etc., and allowing the light of the indicator lamp to pass through the laser-printed area to facilitate the determination of whether the power of the equipment is on or off. In conventional laser labels, emphasis is placed on preventing the color of the lower layer from passing through, so the labels are laminated with a layer containing a material that blocks light. Therefore, since a light-blocking material is used, it is easy to determine the printed characters (hereinafter, this phenomenon is also referred to as character visibility). However, in conventional laser labels, the color of the light source of an indicator lamp or the like is difficult to transmit through the laser-printed area, so it is difficult to determine the color of the light source (hereinafter, this phenomenon is also referred to as light source color transmittance). And, if a laminate containing a material that transmits the color of the light source is used to improve the color transmittance of the light source, it becomes difficult to determine the printed characters. In other words, in conventional laminates, when applied to laser labels, there is a trade-off between character visibility and light source color transmittance.
In view of the above circumstances, the present disclosure has an object to provide a laminate and a laser label that are excellent in both character visibility and color transmittance of a light source.

That is, the present invention includes the following aspects.
<1> A first resin layer made of a first resin composition including a first binder resin, scaly particles, and spherical particles containing a compound having a triazine ring;
a second resin layer made of a second resin composition containing a second binder resin;
A laminate formed by stacking the above in this order.
<2> The laminate according to <1>, wherein a content of the scale-like particles is 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the first binder resin.
<3> The laminate according to <1> or <2>, wherein the scaly particles include titanium oxide-coated mica.
<4> The laminate according to any one of <1> to <3>, wherein the spherical particles include at least one of benzoguanamine beads and melamine beads.
<5> The laminate according to any one of <1> to <4>, wherein the content of the spherical particles is 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the first binder resin.
<6> The laminate according to any one of <1> to <5>, wherein the first resin layer further contains a pigment.
<7> The laminate according to <6>, wherein the pigment contains titanium oxide.
<8> The laminate according to <7>, wherein the content of the titanium oxide is 3 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the first binder resin.
<9> The laminate according to any one of <1> to <8>, wherein the second resin layer further contains a pigment.
<10> The laminate according to <9>, wherein the pigment includes carbon black.
<11> The laminate according to any one of <1> to <10>, wherein the second resin layer has a thickness of 0.5 μm or more and 30 μm or less.
<12> The laminate according to any one of <1> to <11>, wherein the first resin layer is an adhesive layer.
<13> The laminate according to any one of <1> to <12>, further comprising a transparent resin layer between the first resin layer and the second resin layer, the transparent resin layer being made of a third resin composition containing a third binder resin.
<14> The laminate according to any one of <1> to <13>, wherein the second binder resin contains an acrylic resin as a main component.
<15> The laminate according to any one of <1> to <14>, which is for use in a laser label.
<16> A laser label comprising the laminate according to any one of <1> to <14>.

The present invention provides a laminate and laser label that are excellent in both character visibility and color transmittance of the light source.

FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of a laminate according to the present disclosure.

In the present disclosure, a numerical range indicated using "to" indicates a range including the numerical values before and after "to" as the minimum and maximum values, respectively. In addition, unless otherwise specified, the amount of each component in a composition is expressed as the total amount of multiple types of substances when each component contains multiple types of substances.
In the present disclosure, (meth)acrylic means one or both of acrylic and methacrylic, and (meth)acrylate means one or both of acrylate and methacrylate.
In the present disclosure, "printing" is a concept that includes not only the recording of letters, symbols, and codes, but also filling in, and refers to all areas etched by laser irradiation.

--Laminate--
The laminate according to the present disclosure is a laminate in which a first resin layer made of a first resin composition containing a first binder resin, scaly particles, and spherical particles containing a compound having a triazine ring, and a second resin layer made of a second resin composition containing a second binder resin are laminated in this order.

The laminate according to the present disclosure has the above-mentioned configuration, and thus has excellent character visibility and color transmittance of the light source. The mechanism of this action is not entirely clear, but is presumed to be as follows.

When the laminate according to the present disclosure is irradiated with a laser from the second resin layer side (i.e., the surface layer side), the second resin layer is etched and the first resin layer is exposed (if a transparent resin layer is present, the transparent resin layer is exposed).
The first resin layer that is exposed (or seen through the transparent resin layer) contains scale-like particles and spherical particles.
Due to their structural characteristics, the scale-like particles in the first resin layer tend to be arranged horizontally with respect to the surface into which light is incident when viewing characters (i.e., the surface etched by laser irradiation). When light is reflected by the horizontally arranged scale-like particles, all of them tend to be mirror-reflected. Therefore, the incident light is prevented from being absorbed by the layer walls of the second resin layer that are not etched, and the light is diffused while maintaining brightness, resulting in excellent character visibility. In addition, the light irradiated (or incident) from below on the horizontally arranged scale-like particles is less likely to scatter and is easily transmitted, resulting in excellent color transmission of the light source.
Furthermore, due to the structural characteristics of the spherical particles containing a compound having a triazine ring, when light is incident, a part of the light is scattered on the surface of the spherical particles, and most of the light is refracted and transmitted through the inside of the spherical particles. Therefore, even when light is incident from the opposite side to the surface to be etched by laser irradiation, the color of the light source is not unnecessarily blocked, and the light spreads uniformly on the etched surface. Therefore, the color transmittance of the light source is also excellent.

Furthermore, the laminate according to the present disclosure also has excellent base concealment properties, and excellent light transmittance and light source visibility when light is irradiated from the first resin layer side (i.e., the side opposite the surface to be etched by laser irradiation). This is thought to be because, as described above, the scale-like particles and spherical particles in the first resin layer do not unnecessarily block light, but scatter or specularly reflect it.

Hereinafter, the laminate according to the present disclosure will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a laminate according to the present disclosure.
The laminate 100 has a structure in which a transparent resin layer 12 is provided on a first resin layer 11, and a layer C, a layer B, and a layer A constituting a second resin layer 13 are sequentially formed on the transparent resin layer 12.

1, the second resin layer 13 has a three-layer structure including a layer C, a layer B, and a layer A, but the second resin layer 13 may have a single layer. Each of the layers C, B, and A contains a second binder resin.
1, the first resin layer 11 has a single layer configuration, but may have two or more layers. When the first resin layer 11 has two or more layers, all of the two or more layers are made of a first resin composition containing a first binder resin, scale-like particles, and spherical particles containing a compound having a triazine ring.
Although not shown, a base layer may further be included under the first resin layer 11 , that is, on the surface opposite to the surface in contact with the transparent resin layer 12 .

Each layer of the laminate according to the present disclosure will be described in detail below. Note that reference numerals will be omitted in the description.

<First Resin Layer>
The first resin layer is made of a first resin composition including a first binder resin, scaly particles, and spherical particles containing a compound having a triazine ring. The first resin layer may be a single layer or multiple layers.

[First resin composition]
The first resin composition includes a first binder resin, scaly particles, and spherical particles containing a compound having a triazine ring. The first resin composition may include other materials (hereinafter, simply referred to as "other materials") other than the first binder resin, the scaly particles, and the spherical particles containing a compound having a triazine ring.

(First binder resin)
The first binder resin is not particularly limited, but examples thereof include polyolefin resins (e.g., polyethylene resins, polypropylene resins), polycarbonate resins, polystyrene resins, polyethylene terephthalate resins (hereinafter also referred to as "PET resins"), polyurethane resins, acrylic resins, and ester resins (including rosin ester resins).
Among the above, from the viewpoint of ease of handling as a label, the first binder resin is preferably at least one resin selected from the group consisting of polycarbonate resin, polyurethane resin, PET resin, acrylic resin, and ester resin, and more preferably contains at least one of an acrylic resin and an ester resin (more preferably a rosin ester resin).

(Scaly particles)
A scaly particle is, for example, a particle in which the ratio of the average length in one direction (e.g., the major axis) to the average length in the other direction (e.g., the minor axis) is taken as 1 (hereinafter also referred to as the "aspect ratio") is 5 or more.

The scaly particles are not particularly limited as long as they are a shiny material (i.e. a material that mirror-reflects incident light), and examples include metal particles such as aluminum alone, brass, bronze, nickel, stainless steel, zinc, etc.; mica coated with metal oxides such as titanium oxide, zinc oxide, zirconium oxide, iron oxide, chromium oxide, tin oxide, and talc; uncoated mica; coated flaky inorganic crystalline substrates such as barium sulfate, layered silicates, and layered aluminum silicates; single crystal plate-like titanium oxide; glass flakes; silica flakes; bismuth oxychloride; and the like.
The mica may be any of natural mica (e.g., muscovite, phlogopite, etc.) and synthetic mica (e.g., fluorine phlogopite, potassium tetrasilicic mica, sodium tetrasilicic mica, etc.). The scale-like particles may be used alone or in combination of two or more kinds.

Among the above, it is preferable that the scaly particles contain titanium oxide-coated mica.
When the scaly particles contain titanium oxide-coated mica, the scaly particles in the first resin layer do not unnecessarily block incident light and more suitably specularly reflect it, resulting in better color transmittance of the light source and better character visibility.

From the viewpoint of achieving better orientation in the first resin layer, the average primary particle diameter of the scale-like particles is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 80 μm or less, and even more preferably 10 μm or more and 60 μm or less.

The average primary particle size of the scaly particles is a value measured using the same method as the average primary particle size of the spherical particles described below.

The content of the scale-like particles is preferably 3 parts by mass or more and 20 parts by mass or less, more preferably 4 parts by mass or more and 18 parts by mass or less, and even more preferably 5 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the first binder resin.

(Spherical particles containing a compound having a triazine ring)
The spherical particles containing a compound having a triazine ring (hereinafter also simply referred to as "spherical particles") include particles that contain a compound having a triazine ring and have a ratio (hereinafter also referred to as "aspect ratio") of the average length in one direction (e.g., the minor axis) to the average length in the other direction (e.g., the major axis) of 1, which is less than 5. In other words, the spherical particles include not only true spheres but also elliptical spheres.
The spherical particles are not particularly limited as long as they are spherical particles containing at least a compound having a triazine ring. When the spherical particles contain a compound having a triazine ring, the refractive index is suitably adjusted, and the scattering property when light is incident on the spherical particles is excellent, and the visibility of characters is excellent. The spherical particles may be used alone or in combination of two or more kinds.

Examples of spherical particles containing a compound having a triazine ring include spherical particles of a compound having a triazine ring, and composite spherical particles consisting of a compound having a triazine ring and particles.
Examples of spherical particles of a compound having a triazine ring include spherical particles of resins such as a copolymer of benzoguanamine and formaldehyde, a copolymer of benzoguanamine, melamine and formaldehyde, a copolymer of melamine and formaldehyde, a melamine resin, a benzoguanamine resin, a bismaleimide triazine resin, a melamine-modified phenolic resin, and a melamine resin.
Examples of composite spherical particles composed of a compound having a triazine ring and particles include composite spherical particles composed of the resin and inorganic particles (e.g., silica, zirconium oxide, titanium oxide, barium titanate, strontium titanate) or organic particles (e.g., benzoguanamine beads, melamine beads, etc.).

From the viewpoint of more suitably adjusting the refractive index to obtain spherical particles with superior scattering properties when light is incident, it is preferable that the spherical particles contain at least one of benzoguanamine beads and melamine beads.

From the viewpoint of appropriately adjusting the light scattering properties, the average primary particle diameter of the spherical particles is preferably 0.1 μm or more and 10.0 μm or less, more preferably 0.5 μm or more and 8.0 μm or less, and even more preferably 0.8 μm or more and 6.0 μm or less.

The content of the spherical particles is preferably 1 part by mass or more and 25 parts by mass or less, more preferably 3 parts by mass or more and 20 parts by mass or less, and even more preferably 4 parts by mass or more and 19 parts by mass or less, relative to 100 parts by mass of the first binder resin.
When the content of the spherical particles is equal to or less than the upper limit, light shielding due to excessive light scattering is suppressed, and the color transmittance and light transmittance of the light source are superior.
When the content of the spherical particles is equal to or more than the lower limit, light scattering occurs appropriately, resulting in better character visibility and light source visibility.

The total amount of the scaly particles and spherical particles is not particularly limited, but is preferably 5 parts by mass or more and 40 parts by mass or less, and more preferably 10 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the first binder resin.
When the total amount of the scaly particles and spherical particles is equal to or more than the lower limit, the balance between the transmission of the color of the light source and the reflection of light falls within a more suitable range, resulting in superior character visibility and color transmittance of the light source.
When the total amount of the scaly particles and the spherical particles is equal to or less than the upper limit, the hardness of the first resin layer is increased, and thus the first resin layer is prevented from becoming brittle.

The mass ratio of the scaly particles to the spherical particles (scaly particles/spherical particles) is not particularly limited, but from the viewpoint of appropriately adjusting the light reflectivity and light scattering properties, it is preferably 0.1 or more and 5.0 or less, more preferably 0.2 or more and 4.0 or less, and even more preferably 0.3 or more and 3.0 or less.

(Other materials)
The first resin composition may contain other materials in addition to the first binder resin, the scaly particles, and the spherical particles containing a compound having a triazine ring, such as a pigment, a crosslinking agent, a solvent, a leveling agent, an antifoaming agent, an ultraviolet absorbing agent, a light stabilizer, a matting agent, and a modifier.

(Pigment)
The first resin layer preferably further contains a pigment.
When the first resin layer contains a pigment, the light reflectivity and light scattering properties can be more suitably adjusted, resulting in more excellent character visibility and color transmittance of the light source.
The pigments may be used alone or in combination of two or more kinds.
The pigment is not particularly limited, but it is preferable that the pigment be removable by laser irradiation and have weather resistance and durability that allows long-term use.
Pigments also include those listed in Color Index 3rd Edition (1971) and Supplements (1975), published by The Society of Dyers and Colourists.

The color tone of the pigment is not particularly limited, and may be any color tone, such as yellow, orange, red, purple, blue, green, brown, black, and white.
The pigment may be a laser coloring material that develops color in the area irradiated with a laser. Examples of the laser coloring material include transition metal compounds, such as bismuth-containing compounds such as bismuth oxide, molybdenum-containing compounds such as molybdenum oxide, and iron-containing compounds such as iron oxide.

The pigment preferably contains, for example, a white pigment, and more preferably contains titanium oxide. When the pigment further contains a white pigment (more preferably titanium oxide), the light reflectivity and light scattering properties can be more suitably adjusted, resulting in better character visibility and color transmittance of the light source. In addition, the light source visibility and base hiding properties are also excellent.

The content of titanium oxide is preferably 1 part by mass or more and 25 parts by mass or less, more preferably 2 parts by mass or more and 20 parts by mass or less, and even more preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the first binder resin.
When the content of titanium oxide is equal to or less than the upper limit, light blocking by titanium oxide is suppressed, and color transmittance and light transmittance of the light source are superior.When the content of titanium oxide is equal to or more than the lower limit, contrast is created between the area etched by laser irradiation and the other area, and character visibility is superior.

The content of titanium oxide is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 98 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the total amount of pigment.

The content of the pigment is preferably 1 part by mass or more and 25 parts by mass or less, more preferably 2 parts by mass or more and 20 parts by mass or less, and even more preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the first binder resin.
When the pigment content is equal to or less than the upper limit, light blocking by the pigment is suppressed, and the color transmittance and light transmittance of the light source are superior.When the pigment content is equal to or more than the lower limit, a contrast in shading is created between the area etched by laser irradiation and the other areas, and the character visibility is superior.

(Crosslinking Agent)
The crosslinking agent is not particularly limited, but may be an epoxy crosslinking agent, an isocyanate crosslinking agent, or the like. An isocyanate crosslinking agent is preferred, and a polymer of a compound having two or more isocyanate groups in one molecule is more preferred. Examples of compounds having two or more isocyanate groups in one molecule include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI) and their hydrogenated products, diphenylmethane diisocyanate, hexamethylene diisocyanate (HMDI), and isophorone diisocyanate. Among the above, HMDI is preferred from the viewpoint of suppressing yellowing. The crosslinking agent may be used alone or in combination of two or more types.

(solvent)
Examples of the solvent include ketone-based solvents such as cyclohexanone, isophorone, diacetone alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and methylcyclohexanone; ester-based solvents such as ethyl acetate, propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, butyl cellosolve acetate, and carbitol acetate;
Examples of the solvent include aliphatic hydrocarbon solvents such as hexane, cyclohexane, octane, mineral spirits, and kerosene, aromatic hydrocarbon solvents such as toluene, xylene, and 1,2,4-trimethylbenzene, and halogen-based solvents such as chlorobenzene and dichlorobenzene. The solvent may be used alone or in combination of two or more kinds.

(Leveling Agent)
Examples of the leveling agent include fluorine-based leveling agents, silicon-based leveling agents, and acrylic leveling agents. When the resin composition contains a leveling agent, the leveling agent is oriented on the coating film surface when the resin composition dries, and the surface tension of the coating film is uniformized, thereby preventing poor appearance such as floating spots and repelling, and improving wetting with the substrate layer (e.g., film). Specific examples of the leveling agent include "Polyflow" (acrylic leveling agent manufactured by Kyoeisha Chemical Co., Ltd.), "Disparlon" (Kusumoto Chemical Co., Ltd.), and "BYK" (BYK Japan). The leveling agent may be used alone or in combination of two or more types.

(Antifoaming agent)
As the defoaming agent, a known one can be appropriately used. Examples of the defoaming agent include "DOWSIL" (Dow Toray Co., Ltd., silicone-based defoaming agent), "Shin-Etsu Silicone (trademark)" (Shin-Etsu Chemical Co., Ltd.), TSF451 series and TFH450 series (Momentive Performance Materials). The defoaming agent may be used alone or in combination of two or more types.

(UV absorbers, light stabilizers)
The ultraviolet absorbent and the light stabilizer may be appropriately selected from known ones. Examples of the ultraviolet absorbent include "Tinuvin 400" (BASF). Examples of the light stabilizer include "Tinuvin 770" (BASF). The ultraviolet absorbent and the light stabilizer may be used alone or in combination of two or more kinds.

(Matte agent)
As the matting agent, a known one can be appropriately used. For example, the matting agent may be a porous silica, such as "Silisia 380 (registered trademark)" (volume average particle size: about 9 μm, manufactured by Fuji Silysia Corporation). The matting agent may be used alone or in combination of two or more kinds.

(Modifier)
As the modifier, a known modifier can be appropriately used. For example, the modifier may be a polycaprolactone polyol such as "Placcel Series" (manufactured by Daicel Industries, Ltd.). The modifier may be used alone or in combination of two or more kinds.

The first resin layer may be an adhesive layer.
When the first resin layer is an adhesive layer, the cost of the laser label can be kept low.
When the first resin layer is an adhesive layer, the first binder resin preferably contains at least one resin selected from the group consisting of ester resins (more preferably rosin ester resins), acrylic resins, and urethane resins.

The first resin layer has a thickness of preferably 0.5 μm to 30 μm, more preferably 5 μm to 28 μm, and even more preferably 10 μm to 25 μm. When the first resin layer is composed of a plurality of layers, the thickness of the first resin layer refers to the sum of the thicknesses of the layers.
When the thickness of the first resin layer is within the above range, the light scattering and light reflecting properties of the scaly particles and the spherical particles are more ensured, and the character visibility and light transmittance are more excellent. In addition, when the first resin layer is an adhesive layer, the adhesiveness is easily ensured.

<Second Resin Layer>
The second resin layer is made of a second resin composition containing a second binder resin. The second resin layer may be a single layer or a plurality of layers.

[Second Resin Composition]
The second resin composition includes a second binder resin. The second resin composition may include other materials (hereinafter, simply referred to as "other materials") other than the second binder resin.

(Second Binder Resin)
The second binder resin is not particularly limited, but examples thereof include polyolefin resins (e.g., polyethylene resins, polypropylene resins), polycarbonate resins, polystyrene resins, polyethylene terephthalate resins (hereinafter also referred to as "PET resins"), polyurethane resins, acrylic resins, and ester resins (including rosin ester resins).
Among the above, from the viewpoint of ease of handling as a label, it is preferable that the second binder resin is at least one resin selected from the group consisting of polycarbonate resin, PET resin, acrylic resin, and ester resin, and it is more preferable that it contains acrylic resin.

The second binder resin preferably contains an acrylic resin as a main component. When the second binder resin contains an acrylic resin as a main component, the bonding strength between the first resin layer and the second resin layer is more excellent.
The phrase "containing an acrylic resin as a main component" means that the proportion of the acrylic resin is the highest among the resin components constituting the second binder resin.

(Other materials)
The second resin composition may contain materials other than the second binder resin. Examples of the other materials include pigments, crosslinking agents, solvents, leveling agents, defoamers, UV absorbers, light stabilizers, matting agents, and modifiers. The details of these materials are the same as those described above for the first resin composition.

The second resin layer preferably further contains a pigment.
When the second resin layer contains a pigment, the contrast of color tone with the first resin layer can be easily adjusted, and the visibility of characters is improved.

Examples of pigments in the second resin layer include the same pigments as those listed as examples of pigments in the first resin layer.

Preferably, the pigment comprises a black pigment, more preferably carbon black.
When the second resin layer contains a black pigment, the contrast of color tone with the first resin layer can be easily adjusted, and the visibility of characters is improved.

When the second resin layer is composed of two or more layers, for example, from the viewpoint of adjusting the color contrast and improving the visibility of characters, the outermost layer (i.e., the outermost surface on the side that is etched by laser irradiation) may be a layer containing a black pigment, and the layer below the outermost layer may be a layer containing a white pigment.

When the second resin layer is composed of two or more layers, for example, from the viewpoint of adjusting the color contrast and improving character visibility, the layer may contain two or more types of pigments with large differences in shade (for example, a combination of titanium oxide, which is a white pigment, and carbon black, which is a black pigment).

The pigment content is preferably 28 parts by mass or more and 48 parts by mass or less, more preferably 31 parts by mass or more and 45 parts by mass or less, and even more preferably 34 parts by mass or more and 41 parts by mass or less, relative to 100 parts by mass of the second binder resin. When there are two or more second resin layers, the pigment content refers to the total amount of pigment relative to the total amount of second binder resin in the entire second resin layer. When the pigment content is 28 parts by mass or more, a contrast in shade is created between the area etched by laser irradiation and the other areas, resulting in better character visibility.

The second resin layer preferably has a thickness of 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 25 μm or less, and even more preferably 2 μm or more and 20 μm or less. When the second resin layer is composed of a plurality of layers, the thickness of the second resin layer refers to the sum of the thicknesses of the layers.
When the thickness of the second resin layer is within the above range, when the laser is irradiated from the second resin layer side (i.e., from the surface layer side) to perform etching, the first resin layer is prevented from being etched, and therefore, the visibility of characters in the first resin layer is prevented from being reduced.

<Transparent resin layer>
The laminate according to the present disclosure preferably further includes a transparent resin layer between the first resin layer and the second resin layer, the transparent resin layer being made of a third resin composition containing a third binder resin. The transparent resin layer may be a single layer or multiple layers.
When the transparent resin layer is included, when the laser is irradiated from the second resin layer side (i.e., from the surface layer side) to perform etching, the first resin layer is prevented from being etched, and therefore, the visibility of characters in the first resin layer is prevented from being reduced.

The term "transparent resin layer" refers to a resin layer having a visible light transmittance of 90% or more in the wavelength range of 400 nm to 700 nm. The visible light transmittance of the transparent resin layer is preferably 95% or more.
The transmittance of the transparent resin layer can be measured using a spectrophotometer UH4150 manufactured by HITACHI Corporation.

[Third resin composition]
The third resin composition includes a third binder resin.
The third binder resin is not particularly limited as long as it is a resin that can make the layer a transparent resin layer, and examples thereof include polyethylene terephthalate resin, acrylic resin, polyester resin, polyurethane resin, polyolefin resin, and silicone resin.

The third resin composition may further contain other materials other than the third binder resin, within the range in which the layer becomes a transparent resin layer (i.e., within the range in which the transmittance of the transparent resin layer satisfies the above range). Examples of the other materials include the same materials as those listed for the first resin composition.

The transparent resin layer preferably has a thickness of 1 μm or more and 80 μm or less, more preferably 10 μm or more and 70 μm or less, and even more preferably 20 μm or more and 60 μm or less. When the transparent resin layer is composed of a plurality of layers, the thickness of the transparent resin layer refers to the sum of the thicknesses of the layers.
When the thickness of the transparent resin layer is within the above range, when the laser is irradiated from the second resin layer side (i.e., from the surface layer side) to perform etching, etching to the first resin layer is suppressed, and therefore, deterioration of character visibility in the first resin layer is suppressed.

<Applications>
The laminate according to the present disclosure is excellent in both character visibility and light source color transmittance. It is also excellent in base concealment, light source visibility, and light transmittance. For this reason, it is suitable for use as a laser label, sticker, etc. to be attached to the indicator part of a precision instrument, and is preferably used as a laser label.

<Method of manufacturing laminate>
The laminate according to the present disclosure is formed by sequentially applying the above-mentioned resin composition onto a substrate layer or a printing layer provided as necessary, and curing the composition. The method of applying the resin composition is not particularly limited, and examples thereof include screen printing, gravure printing, bar coating, knife coating, roll coating, blade coating, die coating, lamination, spray coating, electrostatic coating, dip coating, and combinations thereof. The method of curing the resin composition is not particularly limited, and can be performed using hot air drying, an oven, a hot plate, or the like.

-Laser label-
A laser label according to the present disclosure is a laser label including the laminate according to the present disclosure. The laser label refers to a display material on which an image can be recorded by laser irradiation and which can be attached to an adherend.
According to the present disclosure, a laser label can be obtained that has excellent character visibility and color transmittance of the light source.

The laser label is printed by irradiating the second resin layer side (i.e., the surface layer side) of the laminate according to the present disclosure with a laser.
The intensity of the laser irradiated onto the laminate can be appropriately designed depending on the thickness of the second resin layer in the laminate.

The present disclosure will be illustrated in detail below with examples, but the present disclosure is not limited to these examples.

<Preparation of ink for forming second resin layer>
・Ink A1
A second binder resin, 100.0 parts by mass of acrylic resin Nikalite H4007K4 (manufactured by Nippon Carbide Industries Co., Ltd.), 52.0 parts by mass of polycaprolactone polyol PLACCEL L320AL (manufactured by Daicel Industries, Ltd.), 31.5 parts by mass of crosslinking agent Takenate D268 (manufactured by Mitsui Chemicals, Inc.), and 280.0 parts by mass of titanium oxide pigment NBK-967 White (manufactured by Nikko Bix Co., Ltd.), were mixed and diluted with ethyl acetate to a solid content of 30% by mass, to obtain a second resin layer forming ink A1, which is a second resin composition.

・Ink A2
Ethyl acetate was mixed with 16.7 parts by mass of silica, Sylysia 445 (manufactured by Fuji Silysia Chemical Co., Ltd.), 100.0 parts by mass of acrylic resin, Nikalite H4007K4 (manufactured by Nippon Carbide Industries Co., Ltd.), 22.3 parts by mass of polycaprolactone polyol, Plaxel L320AL (manufactured by Daicel Industries, Ltd.), 9.6 parts by mass of crosslinking agent, Takenate D140N (manufactured by Mitsui Chemicals, Inc.), 7.7 parts by mass of Takenate D268 (manufactured by Mitsui Chemicals, Inc.), 77.7 parts by mass of carbon black pigment, NBK-968 Black (manufactured by Nikko Bix Co., Ltd.), and 51.5 parts by mass of titanium oxide pigment, NBK-967 White (manufactured by Nikko Bix Co., Ltd.), and diluted with ethyl acetate to a solid content of 30% by mass to obtain a second resin layer forming ink A2, which is a second resin composition.

Ink B
Polyflow No. in ethyl acetate. 85HF (Kyoeisha Chemical Co., Ltd.) 3.6 parts by mass, OH group-containing silicone BYK-370 (Big Chemie Japan Co., Ltd.) 14.0 parts by mass, Cylysia 445 (Fuji Silysia Chemical Co., Ltd.) 20 parts by mass were added, and acrylic resin Nikalite H4007K4 (Nippon Carbide Industries Co., Ltd.) 100.0 parts by mass as a second binder resin, polycaprolactone polyol Plaxel 305 (Daicel Industries, Ltd.) 13.2 parts by mass, crosslinking agent Takenate D-140N-60 (Mitsui Chemicals, Inc.) 40.0 parts by mass, crosslinking agent Coronate HK (Toray Industries, Inc.) 11.2 parts by mass, titanium oxide pigment NBK-967 White (Nikko Bix Co., Ltd.) 66.8 parts by mass were mixed, and diluted with ethyl acetate so that the solid content was 52.9% by mass, and a second resin layer forming ink B, which is a second resin composition, was obtained.

<Preparation of Coating Solution 1 for Forming First Resin Layer>
In ethyl acetate, 8.3 parts by mass of Pencel D-125 (a rosin ester resin, manufactured by Arakawa Chemical Industries, Ltd.) serving as a first binder resin was dissolved.
Next, the amounts (parts by mass) shown in Table 1 of Iriodin 103WNT (titanium oxide-coated mica, manufactured by Merck), spherical particles, Eposter MS (registered trademark), (manufactured by Nippon Shokubai Co., Ltd., copolymer beads of benzoguanamine (a compound having a triazine ring) and formaldehyde, average primary particle diameter 2 μm), and 100 parts by mass of Nissetsu SY-2523 (acrylic adhesive, molecular weight Mw: 600,000) as a first binder resin were mixed and stirred in this order, and then 3.36 parts by mass of CK-101 (manufactured by Nippon Carbide Industries, isocyanate crosslinking agent) as a crosslinking agent was mixed and stirred to adjust the solid content to 30% by mass, thereby obtaining a first resin layer forming coating solution 1, which is a first resin composition.

<Preparation of Coating Fluids 2 to 6 and c1 to c5 for Forming First Resin Layer>
Except for the amounts and types of the scale-like particles, spherical particles, first binder resin and white pigment shown in Table 1, the specifications were the same as those of the coating liquid 1 for forming the first resin layer, and coating liquids 2 to 6 and c1 to c5 for forming the first resin layer were obtained, respectively.
In the case of Coating Solution 6 for forming a first resin layer, the following spherical particles were used instead of Eposter MS (registered trademark). In the case of Coating Solution c4 for forming a first resin layer, the following acrylic beads were used instead of the spherical particles of the present disclosure.
The units of the numerical values in the columns for each component in Table 1 are "parts by mass."

Melamine beads, which are spherical particles: Nissan Chemical Co., Ltd., Optobeads 2000M; composite spherical particles made of a compound having a triazine ring and silica, with an average primary particle diameter of 2 μm
Acrylic beads: acrylic resin particles without triazine rings, Art Pearl J-4P, manufactured by Negami Chemical Industries, Ltd.

<Examples 1 to 6, Comparative Examples 1 to 5>
As the transparent resin layer, a PET resin film S-50 (thickness 50 μm) manufactured by Unitika Ltd. was prepared, and both sides were subjected to a corona treatment.
Then, ink A1 was applied to one surface of the PET resin film so that the film thickness after drying would be 2 μm, and the coating was dried at 100° C. for 1 minute.
Next, Ink A2 was applied onto the coating of Ink A1 so that the coating thickness after drying would be 2 μm, and then dried at 100° C. for 1 minute.
Subsequently, the film was aged at 40° C. for 3 days, and then ink B was applied onto the coating of ink A2 so that the film thickness after drying would be 15 μm, and after drying at 150° C. for 1 minute, the film was aged for 3 days at 60° C. In this manner, a second resin layer composed of three layers, ink A1/ink A2/ink B, in this order, was formed on the PET resin film.
Next, the first resin layer forming coating liquid of the type shown in Table 1 was applied to the release paper, which is the base layer, so that the film thickness after drying was 20 μm, and dried at 100 ° C. for 1 minute to prepare a release paper / first resin layer laminate. Then, this laminate was laminated on the surface of the PET resin film opposite to the surface on which the second resin layer was provided, to form a first resin layer. This resulted in a laser label having a laminate structure of release paper / first resin layer / PET resin film / second resin layer. The first resin layer is an adhesive layer.

<Evaluation>
Laser printing For each example of the laser label, the characters "NIPPON CARBIDE INDUSTRY" were printed on the second resin layer side with a FAYb laser marker LP-Z 130 (manufactured by Panasonic Corporation) under the conditions of line width 0.01 mm, laser power 50.0%, 3000 mm/sec, and print pulse period 50.0 μs (printing 1). In addition, a square area of 3 cm x 3 cm was irradiated with the laser over the entire surface to perform square printing (printing 2).
After laser printing, the laser labels of each example were evaluated for character visibility, light source visibility, background hiding ability, light transmittance, and light source color transmittance by the following evaluation methods. The results are shown in Table 1.
In the evaluation method described below, the release paper, which is the base layer, is peeled off for evaluation; however, depending on the thickness and type of the base layer, it may be possible to irradiate and transmit light without peeling off the base layer, and the evaluation method of the present disclosure is not limited thereto.

[Text visibility]
For the printed laser label of each example, the base material layer (release paper) was peeled off and the readability of the characters of print 1 "NIPPON CARBIDE INDUSTRY" when viewed from the second resin layer side (i.e., the side irradiated with the laser) was visually evaluated according to the following criteria.
-Evaluation criteria-
A: The characters are clearly legible.
B: The characters are easy to read.
C: The characters can be read.
D: The characters are difficult to read.

[Light source visibility]
For the printed laser label of each example, the base material layer (release paper) was peeled off and light was irradiated from the side of the base material layer (release paper) that was in contact with the first resin layer. Print 2 "print that completely filled in an area of 3 cm x 3 cm" was evaluated based on whether the shape of the light source was visible, using the following criteria.
-Evaluation criteria-
A: The shape of the light source is unknown.
B: The shape of the light source is slightly visible.
C: The shape of the light source is clearly visible.

[Base hiding power]
The printed laser label of each example had the base material layer (release paper) peeled off and was placed on a desk with a wood grain surface. When viewed from the second resin layer side (i.e., the side irradiated with the laser), the area of print 2 (print that completely fills in an area of 3 cm x 3 cm) was evaluated according to the following criteria to see whether the wood grain pattern of the base was visible.
-Evaluation criteria-
A: You can't see the base at all.
B: The base is barely visible.
C: The base coat is slightly visible.
D: The base coat is quite visible.

〔Optical transparency〕
For the printed laser label of each example, the base material layer (release paper) was peeled off and light was irradiated from the first resin layer side, and the area of print 2 "printing that completely filled in an area of 3 cm x 3 cm" was evaluated for its ability to transmit the irradiated light using the following criteria.
-Evaluation criteria-
A: Light is transmitted.
B: No light is transmitted.

[Color transmittance of light source]
For the printed laser label of each example, the base material layer (release paper) was peeled off and blue light was irradiated from the first resin layer side. Whether the color of the irradiated light source could be confirmed in the area of print 2 (printing that completely filled in an area of 3 cm x 3 cm) was evaluated according to the following criteria.
-Evaluation criteria-
A: The color of the light source is visible as is.
B: The color of the light source appears almost exactly as it is.
C: The color of the light appears a little whitish.
D: The light appears quite whitish.
E: No light is transmitted.

As shown in Table 1, the laminate of the Example had superior character visibility when used in a laser label compared to the laminate of the Comparative Example. Furthermore, the laminate of the Example had superior light source color transparency compared to the laminate of the Comparative Example, so that even when the light source was a color other than white, the light that passed through was the same color as the light source. Furthermore, the laminate of the Example also had superior light transparency, base concealment, and light source visibility.

100 Laminate 11 First resin layer 12 Transparent resin layer 13 Second resin layer

Claims (16)

a first resin layer made of a first resin composition including a first binder resin, scaly particles, and spherical particles containing a compound having a triazine ring;
a second resin layer made of a second resin composition containing a second binder resin;
A laminate formed by stacking the above in this order. The laminate according to claim 1, wherein the content of the scale-like particles is 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the first binder resin. The laminate according to claim 1, wherein the scale-like particles include titanium oxide-coated mica. The laminate according to claim 1, wherein the spherical particles include at least one of benzoguanamine beads and melamine beads. The laminate according to claim 1, wherein the content of the spherical particles is 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the first binder resin. The laminate according to claim 1, wherein the first resin layer further contains a pigment. The laminate according to claim 6, wherein the pigment comprises titanium oxide. The laminate according to claim 7, wherein the content of the titanium oxide is 3 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the first binder resin. The laminate according to claim 1, wherein the second resin layer further contains a pigment. The laminate of claim 9, wherein the pigment comprises carbon black. The laminate according to claim 1, wherein the second resin layer has a thickness of 0.5 μm or more and 30 μm or less. The laminate according to claim 1, wherein the first resin layer is an adhesive layer. The laminate according to claim 1, further comprising a transparent resin layer between the first resin layer and the second resin layer, the transparent resin layer being made of a third resin composition containing a third binder resin. The laminate according to claim 1, wherein the second binder resin contains an acrylic resin as a main component. The laminate according to any one of claims 1 to 14, which is for use in laser labels. A laser label comprising the laminate according to any one of claims 1 to 14.