Brightly colored photoluminescent materials

Abstract

To provide a photoluminescent material which exhibits a beautiful light color under light and has good luminescent properties.SOLUTION: The present invention relates to a photoluminescent material comprising 19.3-54.3 wt.% of a polymer matrix, 45-80 wt.% of a photoluminescent compound, 0.5-15 wt.% of zirconium oxide, and 0.2-7 wt.% of an optical brightener, and optionally 0-5 wt.% of aluminum oxide, 0-0.3 wt.% of porous silica, a dye system, and additives, the total percentage of the dye system and additives being 0-15 wt.%. The invention also relates to an item coated with such photoluminescent material or made as a whole from such photoluminescent material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a bright-colored photoluminescent material with optimized luminescence performance. [Background technology]

[0002] To create photoluminescent materials, phosphorescent pigments of europium and dysprosium-doped strontium aluminate (Eu 2+ Dy 3+ SrAl2O4 is frequently used. These green or blue luminescent pigments are often yellowish, which makes it difficult to obtain specific bright colors. It is possible to make the pigment white by adding a dopant such as calcium to the crystal lattice, but this has a serious negative impact on the luminescence performance.

[0003] It has been recognized that certain compounds used in photoluminescent materials containing pigments have properties that suppress luminescence. The luminescence of phosphorescent materials occurs as a result of physicochemical interactions between the compounds in the photoluminescent material.

[0004] Therefore, it is difficult to optimize both coloring performance and luminescence performance together. In order to develop the composition, the inventors of the present invention conducted tests to whiten luminescent materials using mineral compounds such as TiO2, CaCO3, ZnO, BaSO4, SiO2, and Al2O3. The mineral compounds were doped with 60% by weight europium and dysprosium-doped strontium aluminate (Eu 2+ Dy 3+ It was added to phosphorescent pigments of the type (SrAl2O4). Tests have shown that these mineral compounds negatively affect the luminescence properties. Therefore, it is always necessary to find the optimal balance between the color perceived under light and photoluminescence. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention comprises a novel composition for white, and more generally, bright colors, that has good luminescence properties while enabling the acquisition of beautiful bright colors under light. [Means for solving the problem]

[0006] In this context, the present invention proposes adding zirconium oxide (ZrO2), particularly stabilized zirconia, to the composition, and more specifically, adding 4-5 mol% yttria-stabilized zirconia, a fluorescent whitening agent, and optionally aluminum oxide (Al2O3). This combination provides the best compromise between whiteness and luminescence performance, and suppresses the yellowish tint of pigments obtained from rare-earth doped alkaline earth aluminates. This color can be optionally adjusted to a brighter shade by adding a dye system.

[0007] Specifically, the present invention relates to a photoluminescent material comprising 19.3 to 54.3% by weight of a polymer matrix, 45 to 80% by weight of a photoluminescent compound, 0.5 to 15% by weight of zirconium oxide, and 0.2 to 7% by weight of a fluorescent whitening agent, and optionally comprising 0 to 5% by weight of aluminum oxide and 0 to 0.3% by weight of porous silica, a dye system, or an additive, wherein the total content of the dye system and the additive is 0 to 15% by weight.

[0008] This fluorescent whitening agent is useful for achieving a brilliant white color because it absorbs light in the near-ultraviolet visible region and re-emits light in the blue region. In particular, this fluorescent whitening agent suppresses the yellowish tint of phosphorescent pigments.

[0009] Adding Al2O3 can make the composition whiter. However, adding Al2O3 alone causes the luminescence to rapidly quench. To address this problem, Al2O3 needs to be used in combination with zirconia.

[0010] Optionally, the photoluminescent material may further contain porous silica obtained from algae to enhance its luminescence properties. This porous silica is obtained from the skeletons of diatoms. These diatom skeletons are microalgae, single-celled organisms with silica skeletons. In fact, recent biological research has shown that diatoms, single-celled algae that make up plankton, are composed of silica nanocells that can absorb sunlight with very high efficiency and perform photosynthesis efficiently even in the dark depths of the ocean. By adding a limited proportion of porous silica (less than 1% by weight) to the photoluminescent material, its luminescence properties can be improved.

[0011] The present invention further relates to an article made entirely of the photoluminescent material, or coated with the photoluminescent material. [Modes for carrying out the invention]

[0012] This invention relates to a photoluminescent material comprising zirconium oxide (ZrO2). This material can be used to manufacture articles entirely from this material, and to coat articles with this material. The articles may be, for example, components of a timepiece. In particular, the articles may be outer components selected from the group consisting of the middle section, case back, bezel, crown, push buttons, bracelet links, bracelet, tang buckle, clasp, dial, flange, date disc, hands, and dial indices. However, this is not an exhaustive list.

[0013] The photoluminescent material comprises a polymer matrix, a photoluminescent compound, zirconium oxide, a fluorescent whitening agent, and optionally aluminum oxide (Al2O3), porous silica, and dyes and additives.

[0014] It contains 0.5 to 5% by weight of zirconium oxide in the form of stabilized zirconia, stabilized by, for example, 4 mol% or 5 mol% of yttrium oxide, based on the total weight of the photoluminescence material. Preferably, this zirconium oxide is contained at 1 to 10% by weight. Typically, the particle size of the zirconia is at the submicron level, with a D50 of about 500 nm.

[0015] The polymer matrix is contained at 19.3 to 54.3% by weight, preferably 28.5 to 48.5% by weight. Note that the upper limit value of the polymer matrix is calculated for the photoluminescence material without aluminum oxide, without porous silica, and without dyes and additives. In the presence of one of these compounds, this upper limit value is reduced so that all compounds in the photoluminescence material do not exceed 100%. In the case of the polymer matrix, the polymer matrix can include all polymers that are translucent or semi-translucent in the visible region. For example, the polymer matrix can be a polymer that is one or more types of resins selected from the acrylic family, polyamide family, polyolefin family, epoxy family, polyurethane family, fluoroelastomer family, and silicone.

[0016] The photoluminescence compound is contained at 45 to 80% by weight, preferably 50 to 70% by weight. The photoluminescence compound can consist of a pigment or a pigment encapsulated within a translucent shell. The pigment is preferably a derivative of an alkaline earth aluminate doped with rare earths. In particular, the pigment is of the formula Sr x Al y O z :Eu 2+ 、Dy 3+ strontium aluminate doped with europium and dysprosium. In particular, the pigment is Sr4Al 14 O 25 :Eu 2+ 、Dy 3+ 、or SrAl2O4:Eu 2+ 、Dy 3+This is possible, and optionally, both can be present in the photoluminescent compound. Advantageously, the pigment can have different particle sizes to optimally distribute the pigment in volume and avoid free space. Furthermore, the presence of different particle sizes in volume allows for a combination of small particles that form shallow surface traps, resulting in high light intensity over short periods, and larger particles that form deeper traps, resulting in longer-term light persistence. For example, the pigment can have a first particle size range centered on a diameter D1 of 500 nm to 10 μm, ideally 500 nm to 5 μm, and a second particle size range centered on a diameter D2 of 10 μm to 500 μm, ideally 10 μm to 20 μm, where the particle size is measured by laser particle size analysis ISO 13320:2020, which is optionally supplemented by SEM analysis using secondary electron imaging. Note that small portions of more than two particle sizes can be sieved and then combined. For example, it is possible to have a first sub-portion of 500 nm to 5 μm at 20% by weight, a second sub-portion of 5 μm to 20 μm at 60% by weight, and a third sub-portion of 20 μm to 50 μm at 20% by weight.

[0017] The pigment can optionally be encapsulated within a translucent organic or mineral shell. The organic shell can typically be selected from the polymers mentioned for the polymer matrix. A mineral shell can be, for example, a silica (SiO2) shell obtained by the sol-gel method. Other examples of mineral shells include zirconium oxide (ZrO2) and aluminum oxide (Al2O3).

[0018] The photoluminescent material further contains a fluorescent whitening agent so as to impart a white luster to the material. The fluorescent whitening agent is contained in an amount of 0.2 to 7% by weight, preferably 0.5 to 5% by weight. The fluorescent whitening agent used is a synthetic organic molecule derived from stilbene containing a sulfonic acid group that absorbs light having a wavelength of 300 nm to 400 nm and re-emits light in the range of blue-violet. These are mainly used as bleaching agents for materials. For example, distyryl biphenyl (DSBP) and diamino stilbene derivatives.

[0019] Optionally, the photoluminescent material can contain 0 to 5% by weight, preferably 0 to 2.5% by weight, of aluminum oxide (Al2O3) according to the desired whiteness. Advantageously, it contains 0.5 to 5% by weight, more advantageously 0.5 to 3% by weight, of Al2O3.

[0020] Optionally, the photoluminescent material further contains 0 to 15% by weight, preferably 0.5 to 8% by weight, of pigment systems and additives. Preferably, the photoluminescent material contains 0.5 to 5% by weight of a pigment system. This pigment system preferably contains an organic dye that does not absorb light in the emission wavelength range of the photoluminescent pigment. This organic dye can be a fluorescent pigment or dye whose absorption is in the UV range and emission is in the visible spectrum. For example, organic fluorescent pigments or dyes such as those with the trade names Radiant and Aralon (registered trademark). It can also be a semi-translucent pigment or dye with a low absorption rate at the emission wavelength of the energy storage pigment. For example, it can be a semi-translucent pigment or dye by Clariant. Other additives such as metallic pigments and pigments with a pearlescent effect, UV-resistant additives for protecting the polymer matrix, dispersants such as silanes for promoting the dispersion of additives, and silica-type nanoscale fillers for adapting the viscosity parameters of the mixture can also be added.

[0021] Optionally, the photoluminescent material can include porous silica obtained from the skeletons of diatoms. Typically, the average diameter of the pores can be on the order of 500 μm. Optionally, the porous silica can be synthetic porous silica. In the case of synthetic silica, the average diameter of the pores is typically 0.1 μm to 3 μm. The porous silica is included at 0 to 0.3 wt%, preferably 0.01 to 1 wt%, more preferably 0.07 to 0.3 wt%, and even more preferably 0.09 to 0.2 wt%.

[0022] A method for manufacturing an article made entirely from a photoluminescent material involves mixing one or more types of polymers intended to form a polymer matrix, preferably with a dispersant. This initial mixing is carried out with respect to a photoluminescent pigment, which may optionally be pre-encapsulated. Then, zirconium oxide and a fluorescent whitening agent are added to this second mixture, along with any dye systems, additives, aluminum oxide, and porous silica. This mixture can be made from a liquid resin using a speed mixer or a paddle mixer. And the resulting mixture can be shaped by extrusion. Also, to produce a thermoplastic mixture and convert it into reusable granules for injection molding, the mixture can be made by a twin-screw extruder or a high-speed mixer.

[0023] A method for manufacturing an article coated with a photoluminescent material involves depositing a coating on a substrate by techniques such as screen printing, pad printing, spray coating, etc.

[0024] A test for making a sample entirely from the photoluminescent material is carried out with 5 wt% of yttria-stabilized zirconia with respect to the total weight of the photoluminescent material, SrAl2O3:Eu 2+ , Dy 3+This was carried out by adding the photoluminescent pigment to an epoxy resin with a filler content of 60% by weight. Samples were observed under a D65 light booth. In parallel, the same base material was tested with TiO2, ZnO, BaSO4, CaCO3, SiO2, and Al2O3.

[0025] Furthermore, the tests were conducted by combining 5 wt% yttria-stabilized zirconia with 0.25, 2.5, and 5 wt% Al2O3.

[0026] Furthermore, the tests were conducted by combining 5 wt% yttria-stabilized zirconia with 0.2 wt% porous silica.

[0027] This material was molded by vacuum casting.

[0028] These tests showed that the best compromise between the whiteness and intensity of phosphorescent luminescence is obtained in yttria-stabilized zirconia, where the level of whiteness increases in the presence of Al2O3, depending on the quality of whiteness achieved in the visible color.

[0029] In tests using porous silica, the luminescence properties increased by 20% after 10 minutes. These luminescence properties were measured according to ISO 17514-2003.

Claims

1. A photoluminescent material comprising 19.3 to 54.3% by weight of a polymer matrix, 45 to 80% by weight of a photoluminescent compound, 0.5 to 15% by weight of zirconium oxide, and 0.2 to 7% by weight of a fluorescent whitening agent, and further comprising 0 to 5% by weight of aluminum oxide, 0 to 0.3% by weight of porous silica, and at least one of a dye system and an additive, The total content of the dye system and the additive is 0 to 15% by weight. A photoluminescent material characterized by the following features.

2. The polymer matrix is ​​contained in an amount of 28.5 to 48.5% by weight. The aforementioned photoluminescent compound is present in an amount of 50 to 70% by weight. Zirconium oxide is present in a quantity of 1 to 10% by weight. The aforementioned fluorescent whitening agent is present in an amount of 0.5 to 5% by weight. The photoluminescent material according to feature 1.

3. Aluminum oxide is present in a quantity of 0.5 to 5% by weight. The photoluminescent material according to feature 1.

4. The porous silica is present in an amount of 0.01 to 1% by weight. The photoluminescent material according to feature 1.

5. The porous silica mentioned above was obtained from the skeleton of a diatom. The photoluminescent material according to feature 1.

6. The aforementioned photoluminescent compound includes a pigment which is a rare earth-doped alkaline earth aluminate derivative. The photoluminescent material according to feature 1.

7. The aforementioned pigment is of the formula Sr x Al y O z :Eu 2+ , Dy 3+ These are europium and dysprosium-doped alkaline earth aluminate derivatives. The photoluminescent material according to feature 6.

8. The pigment is Sr 4 Al 14 O 25 : Eu 2+ and Dy 3+ and / or SrAl 2 O 4 : Eu 2+ and Dy 3+ is such The photoluminescent material according to feature 7.

9. The photoluminescent compound is composed of the pigment encapsulated within an organic or mineral translucent shell. The photoluminescent material according to feature 6.

10. Zirconium oxide is stabilized by yttria. The photoluminescent material according to feature 1.

11. The polymer matrix comprises one or more resins selected from the acrylic family, polyamide family, polyolefin family, epoxy family, polyurethane family, fluoroelastomer family, and silicone. The photoluminescent material according to feature 1.

12. The organic translucent shell comprises one or more resins selected from the acrylic family, polyamide family, polyolefin family, epoxy family, polyurethane family, fluoroelastomer family, and silicone. The aforementioned translucent mineral shell contains silica. The photoluminescent material according to feature 9.

13. The photoluminescent compound includes pigments having various particle sizes. The photoluminescent material according to feature 6.

14. The pigment has at least a first particle size range centered on a diameter D1 of 500 nm to 10 μm, and a second particle size range centered on a diameter D2 of 10 μm to 500 μm. The photoluminescent material according to feature 13.

15. The fluorescent whitening agent is a stilbene derivative containing a sulfonic acid group. The photoluminescent material according to feature 1.

16. Made of or coated with the photoluminescent material described in claim 1 An article characterized by the following:

17. A component of a timekeeping device The article according to feature 16.