3d-printed products

Abstract

To provide 3D-printed products.SOLUTION: The present invention relates to urethane-acrylate-resin-based 3D-printed products having a colour distance ΔE of less than 20 from the L*a*b* coordinates for a colour number beginning with "2" of the RAL colour chart, comprising at least one orange methine dye dissolved therein, to the use of orange methine dyes for producing 3D-printed products having a colour distance ΔE of less than 20 from the L*a*b* coordinates for a colour number of the RAL colour chart beginning with "2" by photopolymerization-based 3D printing, and to a method for increasing the lightfastness and colouristic properties of photopolymerizable urethane-acrylate-resin-based compositions and 3D-printed products to be produced therefrom having a colour distance ΔE of less than 20 from the L*a*b* coordinates for a colour number beginning with "2" of the RAL colour chart by means of at least one orange methine dye dissolved therein.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to L colorants for the color numbers beginning with "2" of the RAL color chart, which contain at least one orange methine dye dissolved therein. * a * b * From the coordinates (i.e. L * a * b * 3D printed products based on urethane acrylate resins with a color difference ΔE of less than 20 (in coordinates), L for color numbers on the RAL color chart starting with "2" by 3D printing based on photopolymerization * a * b * The use of the orange methine dye for producing 3D printed products having a color difference ΔE of less than 20 from the coordinates, as well as L for color numbers beginning with "2" on the RAL color chart by means of a composition based on a photopolymerizable urethane acrylate resin and at least one orange methine dye dissolved therein. * a * b * The present invention relates to a method for improving the lightfastness and color properties of 3D printed products (3D printed products) produced therefrom that have a color difference ΔE of less than 20 from the coordinates. [Background technology]

[0002] Color masterbatches contain colorants in dispersed or dissolved form. The color or hue of a plastic product can serve, among other things, as a distinctive feature for a company or a specific product, as a protective ingredient, as a safety indicator, or as a functional additive. For amorphous plastics, such as polystyrene, polycarbonate, and polymethylmethacrylate, to maintain their transparency, dyes soluble in the polymer must be used. In contrast to pigments, colorants used for 3D printing by photopolymerization are preferably soluble in the plastic resin being processed and not present in a colloidal form.

[0003] 3D printing is a method of additive manufacturing. It refers to the process of building components layer-by-layer by depositing raw materials based on digital 3D design data. Therefore, for the purposes of this invention, "3D printing" is used as a synonym for "additive manufacturing." However, "additive manufacturing" better describes this manufacturing process, which is significantly different from conventional ablative fabrication methods. For example, instead of grinding a workpiece from a solid, additive manufacturing builds components layer-by-layer from raw materials that are available, for example, in powder form. A variety of metals, plastics, and composite materials are available as raw materials.

[0004] 3D printing has recently become established as a manufacturing method in various sectors and industries. In the construction of demonstration and functional prototypes, small- and medium-scale production runs, and by extension, mass production, this process is demonstrating advantages unattainable through other conventional methods. For example, it can significantly accelerate product development and launch, achieving product individualization or functional integration in less time and often at lower cost. For major original equipment manufacturers (OEMs) from a wide variety of industries, additive manufacturing through 3D printing thus offers opportunities for market differentiation in terms of new customer benefits, potential cost reductions, and sustainability goals. In 3D printing, 3D-printed products are created by selectively introducing technology-suitable raw materials that print layer-by-layer into the corresponding desired shape in an automated process. Original equipment manufacturers (OEMs) are the creators of components or products but do not directly release these products into the retail market. In the automotive industry, the term "OEM" is used synonymously with vehicle manufacturer.

[0005] There are various 3D printing processes for plastics, including those that produce plastics by curing only during printing. One embodiment is photopolymerization-based 3D printing, in which a liquid photocurable resin is applied layer by layer and light is used to initiate the photocuring process / polymerization, i.e., photoinduced curing. Selective layer-by-layer curing of the liquid resin is achieved by spatially limited, precisely defined, and computer-controlled exposure of the resin to light within a spectral range suitable for initiating the photopolymerization process. UV light is particularly suitable, but visible or infrared light is also suitable. The photopolymerization-based 3D printing process of the present invention is preferably stereolithography (SLA) or digital light processing (DLP). In both 3D printing methods, the corresponding equipment consists of a light source, which can be used to expose to light from above or below (so-called "top-down" or "bottom-up" printing); a resin tank; and a platform on which the plastic resin used for 3D printing is cured layer by layer. In SLA 3D printing, the surface to be cured is exposed to light point by point by scanning with a laser beam, while in DLP processes, the entire surface is exposed using an LCD (liquid crystal display) panel in particular. In a typical printing process, the printing platform is immersed in resin in a resin tank while an exposure program is carried out to form layers. By repeating the layer formation, the 3D printed product is finally obtained. In the SLA process, a stereolithography printer uses a laser to form the 3D printed product. For this purpose, a plastic solution that hardens under UV light is applied. The corresponding 3D printers are called SLA 3D printers or DLP 3D printers.A comparison of the two technologies, as well as suppliers of comparable 3D printers, can be found in the following review: 3Dnatives, Regina P., 8 April 2021 (Non-Patent Document 1).

[0006] Patent Document 1 discloses a highly sensitive two-photon polymerizable composition that can be photopolymerized by two-photon absorption and can simultaneously dye the polymer to a desired color during polymerization. Such a composition that can be polymerized by two-photon absorption includes at least (A) a polymerizable compound, (B) a two-photon absorbing compound, (C) a polymerization initiator, and (D) a dye.

[0007] Patent Document 2 describes a golf ball comprising a core, at least one layer (shell) surrounding the core, and a fluorescent pigment coloring layer applied to the surface of the outermost layer of the shell. The outermost layer may be made of a thermoplastic polyurethane material (Pandex® T8290 or Pandex® T8283). In one embodiment, the coloring layer applied to the outermost layer is Solvent Orange 60 (Sumiplast® Orange HRP), an orange fluorescent dye. The ball has an appearance characterized by excellent spin performance and durability, excellent visibility, style, and a luxurious feel, as well as excellent weather resistance. Patent Document 3 discloses a colored, curable composition for use in additive manufacturing processes, which comprises a curable resin composition containing a radiation-curable component, a photoinitiator, and a dye composition containing dye D1 and dye D2 (wherein dye D1 has a light absorption maximum in the wavelength range of 400 to 530 nm and dye D2 has a light absorption maximum in the wavelength range of 540 to 650 nm). As an example, two anthraquinone dyes are used: CI Solvent Red 111, CAS No. 82-38-2 (Dye 1), and CI Solvent Violet 13, CAS No. 81-48-1 (Dye 2). It also describes an S30 3D printer (Rapid Shape GmbH, Heimsheim, Germany), which uses LED light with a wavelength of 405 nm at 50 mW / cm. 2 Apply at a strength of 11 seconds per layer.

[0008] In addition to the advantages of color performance during and immediately after the photopolymerization process for producing 3D printed products, the in-use performance of such 3D printed products must also be considered. The colorants used in the aforementioned prior art have proven undesirable during the 3D fabrication process due to color changes that occur as a result of exposure to the light necessary for photopolymerization. However, light sensitivity / lightfastness is a quality attribute for colored 3D printed products produced by photopolymerization-based 3D printing. Fading or discoloration, even browning, of 3D printed products produced by photopolymerization-based 3D printing should be avoided to the greatest extent possible.

[0009] Furthermore, upon photopolymerization, preferably by SLA or DLP processes, colorants intended for 3D printing should maintain their advantageous performance characteristics and should not weaken or even stop the curing / polymerization of the 3D printed product. For the purposes of this invention, advantageous performance characteristics of the orange dye defined for 3D printing in this invention are the establishment of a desired / defined hue and the establishment of a highly pure and vivid color. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] US Patent Application Publication No. 2004 / 204513A1 [Patent Document 2] US Patent Application Publication No. 2011 / 0070976A1 [Patent Document 3] US Patent Application Publication No. 2019 / 0201171A1 [Non-patent literature]

[0011] [Non-Patent Document 1] https: / / www.3dnatives.com / de / sla-vs-dlp-3d-druck-080420211 / Summary of the Invention [Problem to be solved by the invention]

[0012] The problem that the present invention aims to solve is to provide orange dyes for 3D printing by photopolymerization, in particular by SLA or DLP photopolymerization, which, due to their high solubility in the plastics to be processed, allow the establishment of a defined orange hue and remain lightfast during the printing process while also retaining their color properties. [Means for solving the problem]

[0013] <Lightfastness evaluation method> To measure the lightfastness of dyes for photopolymerization-based 3D printing, rectangular specimens of the colored resin were prepared for the purposes of this invention, measuring 60 mm in length, 40 mm in width, and 2 mm in height, with a dye concentration of 0.02% in the resin. The specimens were then exposed to a light source (xenon lamp) in the as-printed state for 95-100 hours using a Xenotest Beta+ instrument (Atlas Material Testing Technology GmbH, Linsengericht-Altenhasslau, Germany) in accordance with DIN EN ISO 4892-2. Lightfastness was assessed colorimetrically by recording the transmission spectra of the exposed specimens using an X-Rite Ci7800 integrating sphere spectrophotometer (X-Rite GmbH, Planegg-Martinsried, Germany) with the following settings: optical geometry = d / 8°; spectral interval = 10 nm; spectral range = 360-750 nm. The manufacturer's software for the integrating sphere spectrophotometer then calculates the following from the resulting transmission spectrum: Illuminant / photometer = D65 / 10°; color space = L * a * b * C * The colorimetric data is calculated using the h° setting. The standard for evaluating lightfastness is L * a * b *C * This is the color difference ΔE between the exposed specimen and the corresponding unexposed specimen in the h° color space. The larger the color difference, the greater the change in color impression caused by exposure to light, i.e., the poorer the lightfastness. ΔE is classified based on a comparison with other exemplary orange dyes not according to the invention, whose lightfastness in other applications, especially in the bulk discoloration of plastics, is generally rated as good according to manufacturer's data.

[0014] <Method for evaluating the stability of color characteristics> For the purposes of this invention, the absorption spectra of the studied pigmented resins before and after light-induced curing are compared in order to establish the changes in spectral properties that determine the color properties of the dye.

[0015] To do this, the colored resin prepared as described above in the "Lightfastness Evaluation Method" is transferred to a 1 cm wide quartz glass cell, and an absorption spectrum is recorded in transmission mode in the wavelength range of 360-750 nm using an X-Rite Ci7800 instrument (X-Rite GmbH, Planegg-Martinsried, Germany). These absorption spectra are then corrected for the absorbance of the corresponding uncolored resin by performing the same measurement on the uncolored resin. Similarly, absorption spectra are recorded in transmission mode for the colored specimens and corrected, in each case normalizing the spectrum to the path length of the cell / test specimen.

[0016] Finally, the similarity of the absorption spectra before and after 3D printing is calculated from the measurement data by calculating the correlation coefficient R of the normalized absorption (spectral interval 10 nm). The larger the value of R, the greater the similarity of the absorption spectra, and the more stable the color properties of the dye intended for photopolymerization-based 3D printing are, and the more suitable it is for the purpose of this invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] <The present invention> The solution to the above problem provided by the present invention is based on a photopolymerizable composition comprising at least one urethane acrylate resin and at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility of 0.05 g / L or more at 23°C in the composition based on the urethane acrylate resin, as measured in accordance with DIN EN ISO 7579:2010 DE, for color numbers starting with "2" of the RAL color chart. * a * b * A 3D printed product with a color difference ΔE of less than 20 from the coordinates.

[0018] The present invention further relates to compositions based on at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a photopolymerizable urethane acrylate resin for improving the lightfastness and color properties as measured in accordance with DIN EN ISO 4892-2, and compositions produced therefrom that are L for color numbers starting with "2" of the RAL color chart. * a * b * Also provided is the use of a 3D printed product having a color difference ΔE of less than 20 from the coordinates and a dye solubility of 0.05 g / L or more at 23°C in the urethane acrylate resin-based composition, measured in accordance with DIN EN ISO 7579:2010 DE. The improvement in lightfastness and color properties in the use according to the invention is measured by determining the similarity of the absorption spectra before and after 3D printing by using an integrating sphere spectrophotometer to record the transmission spectra of test pieces of the corresponding colored urethane acrylate resin before and after photoinduced curing, then correcting for the absorbance of the corresponding uncolored resin and normalizing to the path length of the cell / test piece length considered, and finally calculating the correlation coefficient R of the normalized absorbance from the measurement data.

[0019] The present invention further relates to a photopolymerizable urethane acrylate resin-based composition, which uses at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility of 0.05 g / L or more at 23°C in the urethane acrylate resin-based composition, as measured in accordance with DIN EN ISO 7579:2010 DE, and a composition produced therefrom having a color number starting with "2" in the RAL color chart of L. * a * b * The present invention also relates to a method for improving the lightfastness and color properties of 3D printed products having a color difference ΔE of less than 20 from the coordinates, as measured in accordance with DIN EN ISO 4892-2. The improvement in lightfastness and color properties in the method according to the present invention is measured by using an integrating sphere spectrophotometer to record the transmission spectra of test pieces of the corresponding colored urethane acrylate resin before and after photoinduced curing, correcting them for the absorbance of the corresponding uncolored resin and normalizing them for the cell path length / test piece length, and finally calculating the correlation coefficient R of the normalized absorbance from the measurement data, thereby determining the similarity of the absorption spectra before and after 3D printing.

[0020] Finally, the present invention further relates to a method for producing a 3D printer based on a photopolymerization-based SLA method or a DLP method, using a composition based on a urethane acrylate resin containing at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on a urethane acrylate resin of 0.05 g / L or more at 23°C, as measured in accordance with DIN EN ISO 7579:2010 DE, for a color number starting with "2" on the RAL color chart. * a * b * The present invention also relates to a process for additively manufacturing a 3D printed product having a color difference ΔE of less than 20 from coordinates.

[0021] For the avoidance of doubt, it should be noted that the scope of the present invention encompasses all of the definitions and parameters set forth below in "general terms" or specified as "preferred ranges," in any desired combination. This also relates to the combination of the stated amounts of the individual components relevant to the claimed processes and uses. Specifications cited in the context of this application refer to the latest editions as of the filing date of the present application. Percentage figures are by weight unless otherwise specified.

[0022] Table 1: RAL color chart for orange In the context of the present invention, orange is understood to mean a color in the RAL color system, as described at https: / / de.wikipedia.org / wiki / RAL-Farbe#Orange, that has a color number on the RAL color chart starting with "2." Specifically, at the time of filing the present application, the following distinctions are made between orange hues:

[0023] [Table 1]

[0024] This table shows the device-independent CIE L values ​​for each RAL value for orange. * a * b * The color values ​​are shown here, but when using the D65 standard light with a 10° field of view of the standard photometer, L * represents the brightness, and a * denotes the color locus on the red-green axis, and b * represents the color coordinates on the yellow-blue axis. The color model is based on EN ISO 11664-4 "Colorimetry - Part 4: CIE 1976, L * a * b * It is standardized in the "Color space". * a * b* For more information on color spaces (and more specifically: CIELAB), see: https: / / de.wikipedia.org / wiki / Lab-Farbraum. Each color in the color space is represented by a rectangular coordinate system, L * , a * , b *}. Therefore, a * b * The coordinate plane is constructed using opponent color theory: green and red are opposite each other, a * Located at both ends of the axis, and from blue to yellow is b * The axis. Complementary hues are on opposite sides of each other at an angle of 180°, and all achromatic colors are centered between them (the coordinate origin, a * =0, b * =0).

[0025] L * The axis is a number between 0 and 100, representing the brightness (luminance) of the color. In the coordinate system, it is a * b * It stands perpendicular to the surface. It can also be called the neutral gray axis, because all achromatic colors (gray hues) are connected to the black (L * =0) and White (L * = 100). * The axis indicates the green or red component of the color, where negative values ​​represent green and positive values ​​represent red. * The axis represents the blue or yellow component of the color, where negative values ​​represent blue and positive values ​​represent yellow.

[0026] a * The value ranges from approximately -170 to +100, and b * The values ​​range between -100 and +150, where their maximum value is reached only at mid-luminance for certain hues. The CIELAB color space has its maximum range in the mid-luminance region, but this varies in height and magnitude depending on the color range.

[0027] According to the present invention, the orange hue is determined by the L color number starting with "2" on the RAL color chart. * a * b * The coordinates have a color difference ΔE of less than 20.

[0028] <Preferred orange methine dyes according to the present invention> Methine dyes (also called polymethine dyes), according to https: / / de.wikipedia.org / wiki / Methinfarbstoffe#:~:text=Die%20Methinfarbstoffe%20enthalten%20eine%20ungerade,kationisch%2C%20anionisch%20oder%20neutral%20sein, are dyes in which the chromophore system consists of multiple conjugated double bonds (polyene) flanked by two end groups (electron acceptor A and electron donor D), as seen in formula (I). [ka]

[0029] Methine dyes contain an odd number of methine groups. The terminal group may be part of a heterocycle, or the double bond may be part of an aromatic system. This gives rise to various subspecies of methine dyes. Methine dyes can be characterized as polyene dyes with terminal electron donor and electron acceptor groups. In most cases, the end groups of methine dyes contain nitrogen or oxygen atoms. However, while polyene dyes, typically obtained as natural dyes such as carotenoids, are limited to yellow to yellow-red hues, a nearly complete color spectrum can be achieved using primarily synthetic methine dyes. For coloring plastics, and therefore for photopolymerization-based 3D printing in this invention, the preferred orange methine dyes are merocyanine dyes with amino and carbonyl groups as terminal groups of the polyene structural element. Dyes of this type can be represented in either neutral or zwitterionic mesomeric canonical form, as shown in formula (II). [ka]

[0030] A well-known representative merocyanine dye is Macrolex® Orange R (CAS No. 185766-20-5), or Solvent Orange 107.

[0031] According to the present invention, methine dyes suitable for coloring plastics, which are preferably used for 3D printing, are styryl dyes obtained by condensing active methylene compounds, such as malononitrile, with benzaldehyde derivatives. As a result of the introduction of a benzene ring into the polyene moiety, these compounds have a styrene substructure.

[0032] <Preferred embodiment of the present invention> The compositions based on urethane acrylate resins and 3D printed products produced therefrom that can be used in accordance with the present invention are L for color numbers starting with "2" on the RAL color chart for orange. * a * b * It is preferable to have a color difference ΔE of less than 10 from the coordinates.

[0033] Particularly preferably, compositions based on urethane acrylate resins and 3D printed products produced therefrom that can be used in accordance with the present invention are those that are based on the L 2000 series of RAL color charts for orange. * a * b * The coordinates have a color difference ΔE of less than 5.

[0034] Preferably, the present invention relates to a composition for additive manufacturing of 3D printed products by photopolymerization-based 3D printing, comprising at least one urethane acrylate-based resin and at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a dye solubility in the urethane acrylate resin-based composition at 23°C of 0.05 g / L or more, as measured according to DIN EN ISO 7579:2010 DE, for color numbers starting with "2" of the RAL color chart. * a * b * For 3D printed products with a color difference ΔE of less than 20 from the coordinates.

[0035] Preferably, the present invention relates to the use of at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility of 0.05 g / L or more at 23°C in compositions based on urethane acrylate resins, measured according to DIN EN ISO 7579:2010 DE, and to the production of compositions based on photopolymerizable urethane acrylate resins and compositions produced therefrom by means of additive manufacturing in 3D printing, for color numbers starting with "2" of the RAL color chart.* a * b * The present invention relates to a method for improving the lightfastness and color properties of 3D printed products having a color difference ΔE of less than 20 from the coordinates, as measured in accordance with DIN EN ISO 4892-2.

[0036] Preferably, the present invention relates to compositions based on at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a photopolymerizable urethane acrylate resin for improving the lightfastness and color properties measured in accordance with DIN EN ISO 4892-2, and the compositions based on the RAL color chart for the color numbers starting with "2" and the RAL color chart for the color numbers starting with "2" produced therefrom by means of additive manufacturing in 3D printing. * a * b * The present invention relates to the use of 3D printed products having a color difference ΔE of less than 20 from the coordinates and a dye solubility of 0.05 g / L or more at 23° C. in the urethane acrylate resin-based composition, measured according to DIN EN ISO 7579:2010 DE. Preferred methine dyes for use in the present invention are orange merocyanine dyes having amino and carbonyl groups as terminal groups of the polyene structural element, or orange styryl dyes obtained by condensing an active methylene compound with a benzaldehyde derivative and having a styrene substructure as a result of the introduction of a benzene ring into the polyene moiety.

[0037] Preferably, the present invention relates to a 3D printed product, a use according to the present invention and a method according to the present invention for improving the lightfastness and color properties of a 3D printed product, wherein 0.005 to 5 parts by weight of methine dye are used per 20 to 99.995 parts by weight of urethane acrylate-based resin (preferably including additives).

[0038] Particularly preferably, in addition to the at least one methine dye, the urethane acrylate resin further contains 0.5 to 10 parts by mass of a photoinitiator (preferably having absorption in the wavelength range of 300 to 450 nm).

[0039] Very particularly preferably, in addition to the at least one methine dye and 0.5 to 10 parts by weight of a photoinitiator, the urethane acrylate resin further comprises 0.001 to 1 part by weight of at least one additive, with preferred additives for the purposes of the present invention being at least one leveling agent, at least one stabilizer, at least one additional dye different from the methine dye, at least one filler, or at least one organic pigment.

[0040] <Urethane acrylate-based resin> Photopolymerizable urethane acrylate-based resins preferred according to the present invention for additive manufacturing, especially in 3D printing, are based on polyurethane acrylates (CAS No. 82116-59-4), polyether urethane acrylates, or urethane acrylate resins. See WO 2005 / 028532 A1, RU 2546966 C1, or M. Alishiri et al., Materials Science and Engineering: C, Vol. 42 (September 2014), pp. 763-773.

[0041] Particularly preferred for use in connection with the present invention is "3D Printing UV Sensitive Resin Clear" (Shenzhen Anycubic Technology Co., Ltd, China), which is a colorless resin for high-speed light-induced 3D printing, comprising 30-60% polyurethane acrylate (CAS No. 82116-59-4); 10-40% isooctyl acrylate (CAS No. 29590-42-9), and 2-5% photoinitiator.

[0042] In addition to at least one dye, the photopolymerizable resin usable in accordance with the present invention preferably contains a mixture of at least one polymerizable monomer, preferably an acrylate, and / or a prepolymer, preferably a (poly)urethane acrylate, at least one photoinitiator, and at least one additive. For details of such additives, please refer to WO 2018 / 038954 A1 (the entire contents of which are incorporated herein by reference). Suitable photoinitiators and additives are listed below.

[0043] <Photoinitiator> Photoinitiators that can be used in accordance with the present invention are typically characterized by one or more of the following properties: one or more light absorption bands within the wavelength range of 300-450 nm and / or a solubility of at least 2 g / L at 23°C in the curable composition; solubility in the radiation-curable component of the curable resin composition and / or in any additives optionally present; The ability to form chemical species that induce polymerization reactions, for example by free radicals, when exposed to light energy having a wavelength between 300 and 450 nm.

[0044] Particular preference is given in accordance with the invention to using at least one photoinitiator from the following group: 2-hydroxy-2-methyl-1-phenylacetone, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate.

[0045] <Additives> According to the present invention, the photopolymerizable resin composition usable for 3D printing may preferably include at least one additive, stabilizer(s), or mixtures thereof.

[0046] In particular, the addition of stabilizer(s) to the curable composition can improve the resolution and accuracy of the SLA process by attenuating or preventing undesirable scattering effects, and also contribute to extending the shelf life of the curable composition. Such stabilizers generally contain phenolic units. Preferred are: p-methoxyphenol (MOP), hydroquinone monomethyl ether (MEHQ), 2,6-di-tert-butyl-4-methylphenol (BHT; Ionol), phenothiazine, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), and mixtures thereof. Such stabilizer(s) are preferably used in the following amounts: Lower limit: at least 0.001%, or at least 0.005%, or at least 0.01% by mass; Upper limit: 0.02% or less, or 0.05% or less, or 0.5% or less, or 1% or less by mass; Range: 0.001% to 1% or 0.005% to 0.05% by mass; (wherein weight percent is based on the weight of the curable composition).

[0047] <Methine dyes> The orange methine dyes that can be used in the present invention are characterized by the following properties: · Molecular weight in the range of 50-1000 g / mol; a solubility in the hardenable composition of at least 0.05 g / L at 23°C; · Light absorption maximum in the wavelength range of 400-560 nm; Very good lightfastness in 3D objects; · Extremely stable color properties during the curing process; Contains at least one methine unit.

[0048] The methine dyes that can be suitably used in the present invention include at least one methine dye having the structure of the following formula (V) (wherein R 1 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R 2 represents C1-C4 alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl) [ka] or the methine dye comprises a structural element of formula (VIII): [ka] wherein R is the following group: [ka] or the following group: [ka] where R 3 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl).

[0049] Methine dyes that can be particularly preferably used in the present invention include at least one structure of the following formula (V), (VI), or (VII): [ka] (In formula V, R 1 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R 2 represents C1-C4 alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), [ka] (In formula VI, R 3 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), or [ka] .

[0050] Methine dyes which can be used very particularly preferably in accordance with the invention are: 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester; Solvent Orange 107 (CAS No. 185766-20-5).

[0051] The method for improving the lightfastness and color properties, measured according to DIN EN ISO 4892-2, of compositions based on photopolymerizable urethane acrylate resins is preferably used in the additive manufacturing of 3D printed products, more preferably in the additive manufacturing by photopolymerization, particularly preferably in the additive manufacturing of 3D printed products using SLA 3D printers or DLP 3D printers based on photopolymerization.

[0052] Therefore, the present invention further relates to a method for producing a 3D printer based on the SLA method or the DLP method using a composition based on a urethane acrylate resin containing at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on the urethane acrylate resin of 0.05 g / L or more at 23°C, as measured in accordance with DIN EN ISO 7579:2010 DE, for a color number starting with "2" on the RAL color chart. * a * b* The present invention also relates to a process for additively manufacturing a 3D printed product having a color difference ΔE of less than 20 from the coordinates. Preferably, the orange methine dye comprises at least one compound of the following structure (V): 1 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R 2 represents C1-C4 alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), [ka] or comprises a structural element of formula (VIII): [ka] wherein R is the following group: [ka] or the following group: [ka] where R 3 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl).

[0053] Particularly preferably, the methine dyes used in the process according to the invention have at least one structural unit of the following formula (V), (VI) or (VII): [ka] (In the formula, R 1 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R 2represents C1-C4 alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), [ka] (In the formula, R 3 represents C1-C4 alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl), [ka] .

[0054] Finally, the present invention very particularly preferably relates to a method for producing a 3D printer based on the SLA method or the DLP method using a composition based on a urethane acrylate resin, which comprises at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on the urethane acrylate resin of 0.05 g / L or more at 23 °C, as measured in accordance with DIN EN ISO 7579:2010 DE, for a color number starting with "2" of the RAL color chart. * a * b * The present invention also relates to a process for additive manufacturing a 3D printed product having a color difference ΔE of less than 20 from coordinates, wherein the methine dye is: 1,3,3-Trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester; Solvent Orange 107, CAS No. 185766-20-5. [Example]

[0055] <Method for measuring the lightfastness of dyes in 3D printing> To measure the lightfastness of dyes in 3D printing, test specimens made from pigmented resin based on Resin Composition 1 (see Table 6) with a dye concentration of 0.02% by weight in the resin were prepared for the purposes of the present invention. As test specimens, rectangular parallelepipeds with the following dimensions were prepared from the pigmented resin by 3D printing: Length: 60mm Width: 40mm Height: 2mm

[0056] The specimens were exposed to a light source (xenon lamp) for 95-100 h using a Xenotest Beta+ instrument (Atlas Material Testing Technology GmbH, Linsengericht-Altenhasslau, Germany) according to DIN EN ISO 4892-2.

[0057] Lightfastness was evaluated colorimetrically by recording the transmission spectra of exposed specimens using an X-Rite Ci7800 integrating sphere spectrophotometer (X-Rite GmbH, Planegg-Martinsried, Germany), for which the following settings were selected: · Optical geometry condition: d / 8゜ · Spectral spacing: 10nm Spectral range: 360~750nm

[0058] From the transmission spectra, the colorimetric data were calculated by the instrument manufacturer's software for the integrating sphere spectrophotometer using the following settings: · Light source / photometer: D65 / 10° · Color space: L * a * b * C * h゜

[0059] The standard for evaluating lightfastness is L * a * b * C *The color difference ΔE between the exposed specimen and the corresponding unexposed specimen in h° color space. The larger the color difference, the greater the change in color impression caused by exposure to light, i.e., the poorer the lightfastness. ΔE was classified based on a comparison with orange dyes not according to the invention (see Non-Inventive Examples), whose lightfastness in other applications (e.g., bulk discoloration of plastics) is generally rated as good according to manufacturer data.

[0060] [Table 2]

[0061] <Method for evaluating the stability of color characteristics> In order to identify changes in the spectral properties that determine the color properties of the dye, the absorption spectra of a colored resin based on Resin Composition 1 before and after curing by photoexcitation were compared.

[0062] The colored resins prepared as described above were transferred to 1 cm-wide quartz glass cells. An X-Rite Ci7800 instrument (X-Rite GmbH, Planegg-Martinsried, Germany) was used to record absorption spectra in the transmission mode over the wavelength range of 360–750 nm. These data were then corrected for the absorbance of the uncolored resin by performing the same measurements on the corresponding uncolored resin. Similarly, absorption spectra in transmission mode were recorded and corrected for the colored specimens. These spectra were normalized to the path length of the cell or specimen in each case.

[0063] Next, we calculated the similarity of the absorption spectra before and after 3D printing from these measurement data by calculating the normalized absorption correlation coefficient R (spectral interval 10 nm). The larger the R value, the greater the similarity of the absorption spectra, and therefore the more stable the color characteristics of the dye in 3D printing.

[0064] [Table 3]

[0065] Three resin compositions with different properties (see the "Raw Materials" section) were used to create colored 3D printed objects and tested according to the methods described above. For resin composition 1, a dye mixture was also tested as an example.

[0066] [Table 4]

[0067] [Table 5]

[0068] <Reaction raw materials>

[0069] [Table 6]

Claims

1. Regarding the number of colors starting with "2" on the RAL color chart ＊ a ＊ b ＊ 1. A 3D printed product having a color difference ΔE of less than 20 in coordinates, the 3D printed product being based on a photopolymerizable composition comprising at least one urethane acrylate resin and at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and having a solubility of 0.05 g / L or more at 23°C in a composition based on said urethane acrylate resin, as measured according to DIN EN ISO 7579:2010 DE.

2. 2. The 3D printed product of claim 1, wherein the urethane acrylate resin is based on a urethane acrylate, a polyurethane acrylate, or a polyether urethane acrylate.

3. 3. The 3D printed product of claim 1 or 2, characterized in that the orange methine dye is a merocyanine dye having an amino group and a carbonyl group as terminal groups of its polyene structural element, or a styryl dye having a styrene substructure.

4. The orange methine dye is represented by the following formula (V), (VI), or (VII): 【Chemical 1】 (In the formula, R １ is C １ ~C ４ alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R ２ is C １ ~C ４ alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl); 【Chemistry 2】 (In the formula, R ３ is C １ ~C ４ alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl); or 【Chemistry 3】 4. The 3D printed product of claim 1, comprising at least one structure of:

5. 5. The 3D printed product of any one of claims 1 to 4, wherein the methine dye is 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester.

6. Use of at least one orange methine dye to improve the lightfastness and color properties, as measured in accordance with DIN EN ISO 4892-2, of photopolymerizable urethane acrylate resin-based compositions and 3D printed products produced therefrom, wherein the methine dye has a molecular weight in the range of 50 to 1000 g / mol and a solubility in the urethane acrylate resin-based composition at 23°C of 0.05 g / L or more, provided that the urethane acrylate resin-based compositions and 3D printed products produced therefrom have a solubility in the range of 0.05 g / L or more, as measured in accordance with DIN EN ISO 4892-2, of the RAL color chart for color numbers starting with "2". ＊ a ＊ b ＊ Use characterized by a color difference ΔE of less than 20 in coordinates.

7. 7. Use according to claim 6, characterized in that the use of the at least one orange methine dye in the additive manufacturing of 3D printed products is carried out in photopolymerization-based 3D printing.

8. 8. Use according to claim 6 or 7, characterized in that the composition based on a urethane acrylate resin is based on a urethane acrylate, a polyurethane acrylate or a polyether urethane acrylate.

9. 9. Use according to any one of claims 6 to 8, characterized in that the orange methine dye is a merocyanine dye having an amino group and a carbonyl group as terminal groups of its polyene structural element, or a styryl dye having a styrene substructure.

10. The orange methine dye is represented by the following formula (V), (VI), or (VII): 【Chemistry 4】 (In the formula, R １ is C １ ~C ４ alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R ２ is C １ ~C ４ alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl); 【Chemistry 5】 (In the formula, R ３ is C １ ~C ４ alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl); or 【Chemistry 6】 Use according to any one of claims 6 to 9, characterized in that it comprises at least one structure of

11. Use according to any one of claims 6 to 9, characterized in that the methine dye is 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester.

12. A method for improving the lightfastness and color properties of photopolymerizable urethane acrylate resin-based compositions and 3D printed products produced therefrom, as measured in accordance with DIN EN ISO 4892-2, comprising using at least one methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility of 0.05 g / L or more at 23°C in the urethane acrylate resin-based composition, with the proviso that the urethane acrylate resin-based composition is in the range of 100% by weight for color numbers starting with "2" on the RAL color chart. ＊ a ＊ b ＊ A method characterized by having a color difference ΔE of less than 20 in coordinates.

13. 13. The method of claim 12, wherein the use of the at least one orange methine dye in the additive manufacturing of 3D printed products is carried out in photopolymerization-based 3D printing.

14. 14. The method according to claim 12 or 13, characterized in that the composition based on a urethane acrylate resin is based on a urethane acrylate, a polyurethane acrylate, or a polyether urethane acrylate.

15. The methine dye is represented by the following formula (V), (VI), or (VII): 【Chemistry 7】 (In the formula, R １ is C １ ~C ４ alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl, and R ２ is C １ ~C ４ alkyl, preferably cyclohexyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl); 【Chemistry 8】 (In the formula, R ３ is C １ ~C ４ alkyl, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl); or 【Chemistry 9】 The method according to any one of claims 12 to 14, characterized in that it comprises at least one structure of the formula:

16. 15. The method according to any one of claims 12 to 14, characterized in that the methine dye is 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester.

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